Biomaterials (v.32, #36)
Lysostaphin-functionalized cellulose fibers with antistaphylococcal activity for wound healing applications
by Jianjun Miao; Ravindra C. Pangule; Elena E. Paskaleva; Elizabeth E. Hwang; Ravi S. Kane; Robert J. Linhardt; Jonathan S. Dordick (pp. 9557-9567).
With the emergence of “super bacteria” that are resistant to antibiotics, e.g., methicillin-resistant Staphylococcus aureus, novel antimicrobial therapies are needed to prevent associated hospitalizations and deaths. Bacteriophages and bacteria use cell lytic enzymes to kill host or competing bacteria, respectively, in natural environments. Taking inspiration from nature, we have employed a cell lytic enzyme, lysostaphin (Lst), with specific bactericidal activity against S. aureus, to generate anti-infective bandages. Lst was immobilized onto biocompatible fibers generated by electrospinning homogeneous solutions of cellulose, cellulose-chitosan, and cellulose-poly(methylmethacrylate) (PMMA) from 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), room temperature ionic liquid. Electron microscopic analysis shows that these fibers have submicron-scale diameter. The fibers were chemically treated to generate aldehyde groups for the covalent immobilization of Lst. The resulting Lst-functionalized cellulose fibers were processed to obtain bandage preparations that showed activity against S. aureus in an in vitro skin model with low toxicity toward keratinocytes, suggesting good biocompatibility for these materials as antimicrobial matrices in wound healing applications.
Keywords: Antimicrobial; Biocompatibility; Enzyme; Cellulose; Keratinocyte; In vitro; test
The effect of substrate microtopography on focal adhesion maturation and actin organization via the RhoA/ROCK pathway
by Chang Ho Seo; Katsuko Furukawa; Kevin Montagne; Heonuk Jeong; Takashi Ushida (pp. 9568-9575).
Recently, a growing number of reports have reported that micro- or nanoscale topography enhances cellular functions such as cell adhesion and stem cell differentiation, but the mechanisms responsible for this topography-mediated cell behavior are not fully understood. In this study, we examine the underlying processes and mechanisms behind specific topography-mediated cellular functions. Formation of focal adhesions (FA) was studied by culturing cells on different kinds of topographies, including a flat surface and surfaces with a micropatterned topography (2 μm lattice pattern with 3 μm intervals). We found that the formation and maturation of focal adhesions were highly dependent on the topography of the substrate although the shape, morphology and spreading of cells on the different substrates were not significantly affected. Focal adhesion maturation and actin polymerization were also promoted in cells cultured on the micropatterned substrate. These differences in cell adhesion led us to focus on the Rho GTPases, RhoA and downstream pathways since a number of reports have demonstrated that RhoA-activated cells have highly enhanced focal adhesions and actin activation such as polymerization. By inhibiting the Rho-associated kinase (ROCK) and downstream myosin II, we found that the FA formation, actin organization, and FAK phosphorylation were dramatically decreased. The topographical dependency of FA formation was also highly decreased. These results show that the FA formation and actin cytoskeleton organization of cells on the microtopography is regulated by the RhoA/ROCK pathway.
Keywords: Extracellular matrix (ECM); Fibronectin; Topography; Focal adhesion; RhoA-ROCK pathway; Myosin II
The use of molecular fluorescent markers to monitor absorption and distribution of xenobiotics in a silkworm model
by Natalia C. Tansil; Yang Li; Leng Duei Koh; Teng Choon Peng; Khin Yin Win; Xiang Yang Liu; Ming-Yong Han (pp. 9576-9583).
The fate of xenobiotics in living organisms is determined by their in vivo absorption, distribution, metabolism and excretion. A convenient and scalable animal model of these biological processes is thus highly beneficial in understanding the effects of xenobiotics. Here we present a silkworm model to investigate the molecular properties-directed absorption, distribution and excretion of fluorescent compounds as model xenobiotics through introducing the compounds into the silkworm’s diet and monitoring the resulting color and fluorescence in the silkworm’s body. The efficient uptake of xenobiotics into silk has been further studied through quantitative analysis of the intrinsically colored and highly luminescent silk secreted by silkworm. Our findings provide first-hand insights to better understand the molecular properties that allow specific materials to be incorporated into silk while it is being produced in the silk gland. The use of resulting luminescent silk as scaffold for tissue engineering application has been demonstrated to clearly reveal the interaction of silk with cells. Furthermore, this new development also paves a way to produce various functional silk embedded with stimuli-sensitive dyes or drugs as novel biomaterials for in vivo applications.
Keywords: Silk; Xenobiotic; ADME; Tissue engineering
Synergistic regulation of cell function by matrix rigidity and adhesive pattern
by Shinuo Weng; Jianping Fu (pp. 9584-9593).
Cell–extracellular matrix (ECM) interactions play a critical role in regulating cellular behaviors. Recent studies of cell–ECM interactions have mainly focused on the actomyosin based and adhesion mediated mechanosensing pathways to understand how individual mechanical signals in the cell microenvironment, such as matrix rigidity and adhesive ECM pattern, are sensed by the cell and further trigger downstream intracellular signaling cascades and cellular responses. However, synergistic and collective regulation of cellular behaviors by matrix rigidity and adhesive ECM pattern are still elusive and largely uncharacterized. Here, we generated a library of microfabricated polydimethylsiloxane (PDMS) micropost arrays to study the synergistic and independent effects of matrix rigidity and adhesive ECM pattern on mechanoresponsive behaviors of both NIH/3T3 fibroblasts and human umbilical vein endothelial cells (HUVECs). We showed that both cell types were mechanosensitive and their cell spreading, FA formation, cytoskeletal contractility, and proliferation were all strongly dependent on both substrate rigidity and adhesive ECM pattern. We further showed that under the same substrate rigidity condition, smaller and closer adhesive ECM islands would cause both cells to spread out more, form more adhesion structures, and have a higher proliferation rate. The influence of adhesive ECM pattern on rigidity-mediated cytoskeletal contractility was cell type specific and was only significant for NIH/3T3. Morphometric analysis of cell populations revealed a strong correlation between focal adhesion and cell spreading, regardless of substrate rigidity and adhesive ECM pattern. We also observed a strong correlation between cellular traction force and cell spreading, with a substantially smaller independent effect of substrate rigidity on traction force. Our study here had determined key aspects of the biomechanical responses of adherent cells to independent and collective changes of substrate rigidity and adhesive ECM pattern.
Keywords: Extracellular matrix (ECM); Matrix rigidity; Adhesive pattern; Polydimethylsiloxane (PDMS); Mechanotransduction
Effects of fibrin pad hemostat on the wound healing process in vivo and in vitro
by Alexander M. Harmon; Wei Kong; Charito S. Buensuceso; Anne J. Gorman; Tim R. Muench (pp. 9594-9601).
Fibrin Pad is a hemostatic pad designed to control surgical-related bleeding. It consists of a fully absorbable composite matrix scaffold coated with human-derived active biologics that immediately form a fibrin clot upon contact with targeted bleeding surfaces. Studies were conducted to investigate the effect of Fibrin Pad and its biologics-free composite matrix component (Matrix) on the wound healing process in in vitro and in vivo models. Fibrin Pad was evaluated in solid organ, soft tissue defects, and subcutaneous tissues. Immunocompromised rodents were used to avoid xeno-mediated responses. Extracts created from both materials were evaluated for biological activity using in vitro cell culture assays. Neither Fibrin Pad nor Matrix alone showed any inhibition of the wound healing of treated defect sites. An apparent accelerated healing was noted in the soft tissue and subcutaneous tissue defects with Fibrin Pad as compared to Matrix. Both materials showed desirable properties associated with tissue scaffolds. The in vitro study results show that Fibrin Pad extract can induce dose-dependent increases in fibroblast proliferation and migration. These studies confirm that the biologic components of Fibrin Pad can enhance wound healing processes in in vitro assays and fully support wound healing at the site of in vivo application.
Keywords: Wound healing; Fibrinogen; Thrombin; Hemostasis; Animal model
Neuromuscular junction formation between human stem cell-derived motoneurons and human skeletal muscle in a defined system
by Xiufang Guo; Mercedes Gonzalez; Maria Stancescu; Herman H. Vandenburgh; James J. Hickman (pp. 9602-9611).
Functional in vitro models composed of human cells will constitute an important platform in the next generation of system biology and drug discovery. This study reports a novel human-based in vitro Neuromuscular Junction (NMJ) system developed in a defined serum-free medium and on a patternable non-biological surface. The motoneurons and skeletal muscles were derived from fetal spinal stem cells and skeletal muscle stem cells. The motoneurons and skeletal myotubes were completely differentiated in the co-culture based on morphological analysis and electrophysiology. NMJ formation was demonstrated by phase contrast microscopy, immunocytochemistry and the observation of motoneuron-induced muscle contractions utilizing time-lapse recordings and their subsequent quenching byd-Tubocurarine. Generally, functional human based systems would eliminate the issue of species variability during the drug development process and its derivation from stem cells bypasses the restrictions inherent with utilization of primary human tissue. This defined human-based NMJ system is one of the first steps in creating functional in vitro systems and will play an important role in understanding NMJ development, in developing high information content drug screens and as test beds in preclinical studies for spinal or muscular diseases/injuries such as muscular dystrophy, Amyotrophic lateral sclerosis and spinal cord repair.
Keywords: Stem cell; Co-culture; In vitro; Nerve tissue engineering; Skeletal muscle; In vitro test
The influence of scaffold elasticity on germ layer specification of human embryonic stem cells
by Janet Zoldan; Emmanouil D. Karagiannis; Christopher Y. Lee; Daniel G. Anderson; Robert Langer; Shulamit Levenberg (pp. 9612-9621).
Mechanical forces are critical to embryogenesis, specifically, in the lineage-specification gastrulation phase, whereupon the embryo is transformed from a simple spherical ball of cells to a multi-layered organism, containing properly organized endoderm, mesoderm, and ectoderm germ layers. Several reports have proposed that such directed and coordinated movements of large cell collectives are driven by cellular responses to cell deformations and cell-generated forces. To better understand these environmental-induced cell changes, we have modeled the germ layer formation process by culturing human embryonic stem cells (hESCs) on three dimensional (3D) scaffolds with stiffness engineered to model that found in specific germ layers. We show that differentiation to each germ layer was promoted by a different stiffness threshold of the scaffolds, reminiscent of the forces exerted during the gastrulation process. The overall results suggest that three dimensional (3D) scaffolds can recapitulate the mechanical stimuli required for directing hESC differentiation and that these stimuli can play a significant role in determining hESC fate.
Keywords: Human embryonic stem cells; Differentiation; Germ layers; Scaffold elasticity
Biomimetic nanofibrous scaffolds for bone tissue engineering
by Jeremy M. Holzwarth; Peter X. Ma (pp. 9622-9629).
Bone tissue engineering is a highly interdisciplinary field that seeks to tackle the most challenging bone-related clinical issues. The major components of bone tissue engineering are the scaffold, cells, and growth factors. This review will focus on the scaffold and recent advancements in developing scaffolds that can mimic the natural extracellular matrix of bone. Specifically, these novel scaffolds mirror the nanofibrous collagen network that comprises the majority of the non-mineral portion of bone matrix. Using two main fabrication techniques, electrospinning and thermally-induced phase separation, and incorporating bone-like minerals, such as hydroxyapatite, composite nanofibrous scaffolds can improve cell adhesion, stem cell differentiation, and tissue formation. This review will cover the two main processing techniques and how they are being applied to fabricate scaffolds for bone tissue engineering. It will then cover how these scaffolds can enhance the osteogenic capabilities of a variety of cell types and survey the ability of the constructs to support the growth of clinically relevant bone tissue.
Keywords: Bone; Bone tissue engineering; Scaffold; Biomimetic material; Nanofiber
Engineering of living autologous human umbilical cord cell-based septal occluder membranes using composite PGA-P4HB matrices
by Benedikt Weber; Roman Schoenauer; Francesca Papadopulos; Peter Modregger; Silvia Peter; Marco Stampanoni; Arabella Mauri; Edoardo Mazza; Julia Gorelik; Irina Agarkova; Laura Frese; Christian Breymann; Oliver Kretschmar; Simon P. Hoerstrup (pp. 9630-9641).
Interventional closure of intracardiac wall defects using occluder devices has evolved as a highly attractive treatment option. However, incomplete and delayed healing reactions often result in a major risk of residual defects, thromboembolism, or device fractures. Biodegradable living tissue engineered occluder membranes (TEOMs) could provide autologous thromboresistant implants with growth and remodeling capacities. PGA-P4HB composite matrices were seeded with human umbilical cord-derived cells or vascular-derived control cells and exposed to static ( n = 19) or dynamic ( n = 13) conditioning. Harvested TEOMs were integrated into occluder frameworks, exposed to crimping and delivered into pre-formed defects of juvenile porcine hearts. Dynamically conditioned TEOM constructs showed higher collagen formation in histology than static constructs with significantly higher stiffness moduli in uniaxial tensile testing. Grating interferometry revealed substantial but inhomogeneous cone-like degradation of the composite matrices in dynamic conditioning. The crimping and delivery procedures resulted in no significant changes in macroscopy, histo-morphology, cellular viability, DNA or hydroxyproline content, and scanning electron microscopy findings. Here, we present the in vitro fabrication, crimping and experimental delivery of living human umbilical cord-cell derived TEOMs based on composite matrices as a potential future autologous therapy of intracardiac wall defects.
Keywords: Umbilical cord cells; Biodegradable matrix; Septal occluder system; Polyglycolic acid; Poly-4-hydroxybutyrate; Crimping
Local delivery of siRNA using a biodegradable polymer application to enhance BMP-induced bone formation
by Tomoya Manaka; Akinobu Suzuki; Kazushi Takayama; Yuuki Imai; Hiroaki Nakamura; Kunio Takaoka (pp. 9642-9648).
Small interfering RNA (siRNA) is useful tool for specific and efficient knockdown of disease-related genes. However, in vivo applications of siRNA are limited due to difficulty in its efficient delivery to target cells. In this study, we investigated the efficacy of a biodegradable hydrogel, poly-d,l-lactic acid- p-dioxanone-polyethylene glycol block co-polymer (PLA-DX-PEG), as a siRNA carrier. PLA-DX-PEG pellets with or without fluorescein-labeled dsRNA were implanted into mouse dosal muscle pouches. The cellular uptake of dsRNA surround the polymer was confirmed by fluorescent microscopy. The fluorescence intensity was dose-dependent of the dsRNA, and exhibited a time-dependent decrease. To investigate its biological efficiency, noggin (antagonoist to BMPs) gene-silencing with siRNA (siRNA/Noggin) was examined by the amount of suppression of BMP-2-induced noggin expression and the level of performance of BMP, indicated by ectopic bone formation. Noggin gene expression induced by BMP-2 was suppressed by addition of siRNA/Noggin to the implant, and the ectopic bone formation induced by implants with both BMP-2 and siRNA/Noggin was significantly greater than those induced by implants with BMP-2 alone. These results indicate the efficacy of local delivery of siRNAs by PLA-DX-PEG polymer, which intensified bone-inducing effects of BMP and promoted new bone formation by suppressing gene expression of Noggin.
Keywords: siRNA; Polymer; BMP; Noggin; Bone regeneration
Two-tier hydrogel degradation to boost endothelial cell morphogenesis
by Karolina Chwalek; Kandice R. Levental; Mikhail V. Tsurkan; Andrea Zieris; Uwe Freudenberg; Carsten Werner (pp. 9649-9657).
Cell-responsive degradation of biofunctional scaffold materials is required in many tissue engineering strategies and commonly achieved by the incorporation of protease-sensitive oligopeptide units. In extension of this approach, we combined protease-sensitive and -insensitive cleavage sites for the far-reaching control over degradation rates of starPEG-heparin hydrogel networks with orthogonally modulated elasticity, RGD presentation and VEGF delivery. Enzymatic cleavage was massively accelerated when the accessibility of the gels for proteases was increased through non-enzymatic cleavage of ester bonds. The impact of gel susceptibility to degradation was explored for the 3-dimensional ingrowth of human endothelial cells. Gels with accelerated degradation and VEGF release resulted in strongly enhanced endothelial cell invasion in vitro as well as blood vessel density in the chicken chorioallantoic membrane assay in vivo. Thus, combination of protease-sensitive and -insensitive cleavage sites can amplify the degradation of bioresponsive gel materials in ways that boost endothelial cell morphogenesis.
Keywords: Angiogenesis; Hydrogel; Degradation; Endothelial cell; Matrix metalloproteinase
Cultured cell-derived extracellular matrix scaffolds for tissue engineering
by Hongxu Lu; Takashi Hoshiba; Naoki Kawazoe; Ichie Koda; Minghui Song; Guoping Chen (pp. 9658-9666).
Cell-derived extracellular matrix (ECM) scaffolds have received considerable interest for tissue engineering applications. In this study, ECM scaffolds derived from mesenchymal stem cell (MSC), chondrocyte, and fibroblast were prepared by culturing cells in a selectively removable poly(lactic-co-glycolic acid) (PLGA) template. These three types of ECM scaffolds were used for in vitro cultures of MSC and fibroblasts to examine their potential as scaffolds for cartilage and skin tissue engineering. The MSC were cultured in MSC- and chondrocyte-derived ECM scaffolds. The ECM scaffolds supported cell adhesion, promoted both cell proliferation and the production of ECM and demonstrated a stronger stimulatory effect on the chondrogenesis of MSC compared with a conventional pellet culture method. Histological and immunohistochemical staining indicated that cartilage-like tissues were regenerated after the MSC were cultured in ECM scaffolds. Fibroblasts were cultured in the fibroblast-derived ECM scaffolds. Fibroblasts proliferated and produced ECM to fill the pores and spaces in the scaffold. After 2 weeks of culture, a uniform multilayered tissue was generated with homogenously distributed fibroblasts. Cell-derived ECM scaffolds have been demonstrated to facilitate tissue regeneration and will be a useful tool for tissue engineering.
Keywords: Extracellular matrix; Scaffold; Cell culture; Decellularization; Template; Tissue engineering
The creation of an in vitro adipose tissue that contains a vascular–adipocyte complex
by J. Michael Sorrell; Marilyn A. Baber; Dmitry O. Traktuev; Keith L. March; Arnold I. Caplan (pp. 9667-9676).
An increased demand for soft-tissue substitutes has impelled the development of an in vitro adipose tissue. Ideally, such a tissue should contain a vascular network that can deliver blood throughout the construct following its engraftment. This study describes the in vitro fabrication of a pre-vascularized adipose tissue entirely using a self-assembly approach. Adult human adipose stromal cells (ASCs) provided the foundation for this construct. These cells were cultured at high density in the presence of elevated levels of ascorbate prior to adipocytic induction. Vascular support cells consisting of dermal fibroblasts, mixtures of adipose stromal cells and bone marrow mesenchymal stem cells (MSCs) were introduced to sustain an extensive vascular network formed by human umbilical vein endothelial cells (HUVECs). MSCs were introduced to serve as perivascular cells. The resulting construct contained a vascular–adipose tissue continuum that was held together by basement membrane molecules. This construct contains multiple cell types that are typically found in adipose tissue: adipocytes, pre-adipocytes, stem cells, fibroblasts, vascular cells, and perivascular support cells. As such, these constructs can be employed both for in vitro studies to assay cellular interactions between vasculature and other components of adipose tissue. Further, they can also be engrafted into athymic hosts to study vascular and adipocyte stability.
Keywords: Adipose tissue engineering; Fibroblast; ECM; Angiogenesis; Mesenchymal stem cell; Co-culture
Extrahepatic islet transplantation with microporous polymer scaffolds in syngeneic mouse and allogeneic porcine models
by Romie F. Gibly; Xiaomin Zhang; Melanie L. Graham; Bernhard J. Hering; Dixon B. Kaufman; William L. Lowe Jr.; Lonnie D. Shea (pp. 9677-9684).
Intraportal transplantation of islets has successfully treated select patients with type 1 diabetes. However, intravascular infusion and the intrahepatic site contribute to significant early and late islet loss, yet a clinical alternative has remained elusive. We investigated non-encapsulating, porous, biodegradable polymer scaffolds as a vehicle for islet transplantation into extrahepatic sites, using syngeneic mouse and allogeneic porcine models. Scaffold architecture was modified to enhance cell infiltration leading to revascularization of the islets with minimal inflammatory response. In the diabetic mouse model, 125 islets seeded on scaffolds implanted into the epididymal fat pad restored normoglycemia within an average of 1.95 days and transplantation of only 75 islets required 12.1 days. Increasing the pore size to increase islet–islet interactions did not significantly impact islet function. The porcine model was used to investigate early islet engraftment. Increasing the islet seeding density led to a greater mass of engrafted islets, though the efficiency of islet survival decreased. Transplantation into the porcine omentum provided greater islet engraftment than the gastric submucosa. These results demonstrate scaffolds support murine islet transplantation with high efficiency, and feasibility studies in large animals support continued pre-clinical studies with scaffolds as a platform to control the transplant microenvironment.
Keywords: Islet; Diabetes; Transplantation; Scaffold; Polylactic acid; Polyglycolic acid
PEG hydrogels formed by thiol-ene photo-click chemistry and their effect on the formation and recovery of insulin-secreting cell spheroids
by Chien-Chi Lin; Asad Raza; Han Shih (pp. 9685-9695).
Hydrogels provide three-dimensional frameworks with tissue-like elasticity and high permeability for culturing therapeutically relevant cells or tissues. While recent research efforts have created diverse macromer chemistry to form hydrogels, the mechanisms of hydrogel polymerization for in situ cell encapsulation remain limited. Hydrogels prepared from chain-growth photopolymerization of poly(ethylene glycol) diacrylate (PEGDA) are commonly used to encapsulate cells. However, free radical associated cell damage poses significant limitation for this gel platform. More recently, PEG hydrogels formed by thiol-ene photo-click chemistry have been developed for cell encapsulation. While both chain-growth and step-growth photopolymerizations offer spatial-temporal control over polymerization kinetics, step-growth thiol-ene hydrogels offer more diverse and preferential properties. Here, we report the superior properties of step-growth thiol-ene click hydrogels, including cytocompatibility of the reactions, improved hydrogel physical properties, and the ability for 3D culture of pancreatic β-cells. Cells encapsulated in thiol-ene hydrogels formed spherical clusters naturally and were retrieved via rapid chymotrypsin-mediated gel erosion. The recovered cell spheroids released insulin in response to glucose treatment, demonstrating the cytocompatibility of thiol-ene hydrogels and the enzymatic mechanism of cell spheroids recovery. Thiol-ene click reactions provide an attractive means to fabricate PEG hydrogels with superior gel properties for in situ cell encapsulation, as well as to generate and recover 3D cellular structures for regenerative medicine applications.
Keywords: Hydrogel; Photopolymerization; Type 1 diabetes; Degradation
Odontogenic differentiation of human dental pulp stem cells induced by preameloblast-derived factors
by Ji-Hyun Lee; Dong-Seol Lee; Han-Wool Choung; Won-Jun Shon; Byoung-Moo Seo; Eun-Hyang Lee; Je-Yoel Cho; Joo-Cheol Park (pp. 9696-9706).
The differentiation of odontoblasts is initiated by the organization of differentiating ameloblasts during tooth formation. However, the exact roles of ameloblast-derived factors in odontoblast differentiation have not yet been characterized. We investigated the effects of preameloblast-conditioned medium (PA-CM) on the odontogenic differentiation of human dental pulp stem cells (hDPSCs) in vitro and in vivo. Furthermore, we analyzed the PA-CM by liquid chromatography-mass spectrometry to identify novel factors that facilitate odontoblast differentiation. In the co-culture of MDPC-23 cells or hDPSCs with mouse apical bud cells (ABCs), ABCs promoted differentiation of odontoblastic MDPC-23 cells and facilitated odontoblast differentiation of hDPSCs. PA-CM, CM from ABCs after 3 days culture, was most effective in increasing the dentin sialophosphoprotein promoter activity of odontoblastic MDPC-23 cells. When PA-CM-treated hDPSCs were transplanted into immunocompromised mice, they generated pulp-like structures lined with human odontoblast-like cells showing typical odontoblast processes. However, during recombinant human bone morphogenenetic protein 2-treated hDPSCs transplantation, some of the cells were entrapped in mineralized matrix possessing osteocyte characteristics. After proteomic analyses, we identified 113 types of proteins in PA-CM, of which we characterized 23. The results show that preameloblast-derived factors induce the odontogenic differentiation of hDPSCs and promote dentin formation.
Keywords: Epithelial-mesenchymal interaction; Preameloblast-CM; Human dental pulp stem cell; Odontoblast differentiation; Dentin regeneration
Repairing critical-sized calvarial defects with BMSCs modified by a constitutively active form of hypoxia-inducible factor-1α and a phosphate cement scaffold
by Duohong Zou; Zhiyuan Zhang; Jiacai He; Siheng Zhu; Shaoyi Wang; Wenjie Zhang; Jian Zhou; Yuanjin Xu; Yan Huang; Yuanyin Wang; Wei Han; Yong Zhou; Shuhong Wang; Sulan You; Xinquan Jiang; Yuanliang Huang (pp. 9707-9718).
Tissue engineering combined with gene therapy represents a promising approach for bone regeneration. The Hypoxia-inducible factor-1α (HIF-1α) gene is a pivotal regulator of vascular reactivity and angiogenesis. Our recent study has showed that HIF-1α could promote osteogenesis of bone mesenchymal stem cells (BMSCs) using a gene point mutant technique. To optimize the function of HIF-1α on inducing stem cells, another constitutively active form of HIF-1α (CA5) was constructed with truncation mutant method and its therapeutic potential on critical-sized bone defects was evaluated with calcium-magnesium phosphate cement (CMPC) scaffold in a rat model. BMSCs were treated with Lenti (lentivirus) -CA5, Lenti-WT (wild-type HIF-1α), and Lenti-LacZ. These genetically modified BMSCs were then combined with CMPC scaffolds to repair critical-sized calvarial defects in rats. The results showed that the overexpression of HIF-1α obviously enhanced the mRNA and protein expression of osteogenic markers in vitro and robust new bone formation with the higher local bone mineral density (BMD) was found in vivo in the CA5 and WT groups. Furthermore, CA5 showed significantly greater stability and osteogenic activity in BMSCs compared with WT. These data suggest that BMSCs transduced with truncation mutanted HIF-1α gene can promote the overexpression of osteogenic markers. CMPC could serve as a potential substrate for HIF-1α gene modified tissue engineered bone to repair critical sized bony defects.
Keywords: HIF-1α; BMSCs; Calcium–magnesium phosphate cement; Osteogenesis
Enhancing cell penetration and proliferation in chitosan hydrogels for tissue engineering applications
by Chengdong Ji; Ali Khademhosseini; Fariba Dehghani (pp. 9719-9729).
The aim of this study was to develop a process to create highly porous three-dimensional (3D) chitosan hydrogels suitable for tissue engineering applications. Chitosan was crosslinked by glutaraldehyde (0.5 vol %) under high pressure CO2 at 60 bar and 4 °C for a period of 90 min. A gradient-depressurisation strategy was developed, which was efficient in increasing pore size and the overall porosity of resultant hydrogels. The average pore diameter increased two fold (59 μm) compared with the sample that was depressurised after complete crosslinking and hydrogel formation (32 μm). It was feasible to achieve a pore diameter of 140 μm and the porosity of hydrogels to 87% by addition of Acacia gum (AG) as a surfactant to the media. The enhancement in porosity resulted in an increased swelling ratio and decreased mechanical strength. On hydrogels with large pores (>90 μm) and high porosities (>85%), fibroblasts were able to penetrate up to 400 μm into the hydrogels with reasonable viabilities (∼80%) upon static seeding. MTS assays showed that fibroblasts proliferated over 14 days. Furthermore, aligned microchannels were produced within porous hydrogels to further promote cell proliferation. The developed process can be easily used to generate homogenous pores of controlled sizes in 3D chitosan hydrogels and may be of use for a broad range of tissue engineering applications.
Keywords: Chitosan; Hydrogels; Porosity; High pressure CO; 2; Acacia gum
The effect of detergent-based decellularization procedures on cellular proteins and immunogenicity in equine carotid artery grafts
by Ulrike Böer; Andrea Lohrenz; Melanie Klingenberg; Andreas Pich; Axel Haverich; Mathias Wilhelmi (pp. 9730-9737).
Decellularized equine carotid arteries (dEAC) may represent a reasonable alternative to alloplastic materials in vascular replacement therapy. Acellularity of the matrix is standardly evaluated by DNA quantification what however may not record sufficiently the degree of matrix immunogenicity. Thus, our aim was to analyze dEAC with a low DNA content for residual cellular proteins. A detergent-based decellularization protocol including endonuclease treatment resulted in dEAC with 0.6 ± 0.15 ng DNA/mg dry weight representing 0.33 ± 0.14% of native tissue DNA content. In contrast, when matrices were homogenized and extracted by high detergent concentrations westernblot analyses revealed cytosolic and cytosceleton proteins like GAPDH and smooth muscle actin which were depleted to 4.1 ± 1.9% and 13.8 ± 0.55%, resp. Also putative immunogenic MHC I complexes and the alpha-Gal epitop were reduced to only 14.8 ± 1.2% and 15.1 ± 2.05%. Mass spectrometry of matrix extracts identified 306 proteins belonging to cytosol, organelles, nucleus and cell membrane. Moreover, aqueous matrix extracts evoked a pronounced antibody formation when administered in mice and thus display high immunogenic potential. Our data indicate that an established decellularization protocol which results in acellular matrices evaluated by low DNA content reduces but not eliminates cellular components which may contribute to its immunogenic potential in vivo.
Keywords: Extracellular matrix; Decellularization; Westernblot; Mass spectrometry; Immune response
The potential for salmon fibrin and thrombin to mitigate pain subsequent to cervical nerve root injury
by Christine L. Weisshaar; Jessamine P. Winer; Benjamin B. Guarino; Paul A. Janmey; Beth A. Winkelstein (pp. 9738-9746).
Nerve root compression is a common cause of radiculopathy and induces persistent pain. Mammalian fibrin is used clinically as a coagulant but presents a variety of risks. Fish fibrin is a potential biomaterial for neural injury treatment because it promotes neurite outgrowth, is non-toxic, and clots readily at lower temperatures. This study administered salmon fibrin and thrombin following nerve root compression and measured behavioral sensitivity and glial activation in a rat pain model. Fibrin and thrombin each significantly reduced mechanical allodynia compared to injury alone ( p < 0.02). Painful compression with fibrin exhibited allodynia that was not different from sham for any day using stimulation by a 2 g filament; allodynia was only significantly different ( p < 0.043) from sham using the 4 g filament on days 1 and 3. By day 5, responses for fibrin treatment decreased to sham levels. Allodynia following compression with thrombin treatment were unchanged from sham at any time point. Macrophage infiltration at the nerve root and spinal microglial activation were only mildly modified by salmon treatments. Spinal astrocytic expression decreased significantly with fibrin ( p < 0.0001) but was unchanged from injury responses for thrombin treatment. Results suggest that salmon fibrin and thrombin may be suitable biomaterials to mitigate pain.
Keywords: Fibrin; Thrombin; Inflammation; Astrocyte; Pain; Macrophage
Amidolytic, procoagulant, and activation-suppressing proteins produced by contact activation of blood factor XII in buffer solution
by Avantika Golas; Chyi-Huey Joshua Yeh; Christopher A. Siedlecki; Erwin A. Vogler (pp. 9747-9757).
The relative proportions of enzymes with amidolytic or procoagulant activity produced by contact activation of the blood zymogen factor XII (FXII, Hageman factor) in buffer solution depends on activator surface chemistry/energy. As a consequence, chromogenic assay of amidolytic activity (cleavage of amino acid bonds in s-2302 chromogen) does not correlate with the traditional plasma coagulation time assay for procoagulant activity (protease activity inducing clotting of blood plasma). Amidolytic activity did not vary significantly with activator particle surface energy, herein measured as water adhesion tensionτo=γlvocosθa ; whereγlvo is pure buffer interfacial tension andθ a is the advancing contact angle. By contrast, procoagulant activity varied as a parabolic-like function ofτ o, high at both hydrophobic and hydrophilic extremes of activator surface energy and falling through a broad minimum within a 20<τ o<40 mJ/m2 (55 °<θ a < 75 °) range, corroborating and expanding previously-published work. It is inferred from these functional assays that an unknown number of protein fragments are produced by contact activation of FXII (a.k.a. autoactivation) rather than just αFXIIa and βFXIIa as popularly believed. Autoactivation products produced by activator particles within the 20<τ o<40 mJ/m2 (55 °<θ a < 75 °) surface-energy range suppresses production of procoagulant enzymes by activators selected from the hydrophobic or hydrophilic surface-energy extremes through as-yet unknown biophysical chemistry. Suppression proteins may be responsible for the experimentally-observed autoinhibition of the autoactivation reaction.This work shows that contact activation of the blood zymogen FXII is a complex surface-mediated reaction that produces a number of different kinds of protein fragments that can influence the hemocompatibility of cardiovascular biomaterials.
Keywords: Autoactivation; Contact activation; Plasma coagulation; Hageman factor; FXII
Antibody conjugated magnetic iron oxide nanoparticles for cancer cell separation in fresh whole blood
by Hengyi Xu; Zoraida P. Aguilar; Lily Yang; Min Kuang; Hongwei Duan; Yonghua Xiong; Hua Wei; Andrew Wang (pp. 9758-9765).
A highly efficient process using iron oxide magnetic nanoparticles (IO)-based immunomagnetic separation of tumor cells from fresh whole blood has been developed. The process involved polymer coated 30 nm IO that was modified with antibodies (Ab) against human epithelial growth factor receptor 2 (anti-HER2 or anti-HER2/neu) forming IO-Ab. HER2 is a cell membrane protein that is overexpressed in several types of human cancer cells. Using a HER2/neu overexpressing human breast cancer cell line, SK-BR3, as a model cell, the IO-Ab was used to separate 73.6% (with a maximum capture of 84%) of SK-BR3 cells that were spiked in 1 mL of fresh human whole blood. The IO-Ab preferentially bound to SK-BR3 cells over normal cells found in blood due to the high level of HER2/neu receptor on the cancer cells unlike the normal cell surfaces. The results showed that the nanosized magnetic nanoparticles exhibited an enrichment factor (cancer cells over normal cells) of 1:10,000,000 in a magnetic field (with gradient of 100 T/m) through the binding of IO-Ab on the cell surface that resulted in the preferential capture of the cancer cells. This research holds promise for efficient separation of circulating cancer cells in fresh whole blood.
Keywords: Magnetic nanoparticles; Iron oxide; Cancer cells; Cell sorting; Immunomagnetic separation
Suicide gene therapy using reducible poly (oligo-d-arginine) for the treatment of spinal cord tumors
by Young-Wook Won; Kyung-Min Kim; Sung Su An; Minhyung Lee; Yoon Ha; Yong-Hee Kim (pp. 9766-9775).
Suicide gene therapy based on a combination of herpes simplex virus-thymidine kinase (HSV-tk) and ganciclovir (GCV) has obstacles to achieving a success in clinical use for the treatment of cancer due to inadequate thymidine kinase (TK) expression. The primary concern for improving anticancer efficacy of the suicide gene therapy is to develop an appropriate carrier that highly expresses TK in vivo. Despite great advances in the development of non-viral vectors, none has been used in cancer suicide gene therapy, not even in experimental challenge. Reducible poly (oligo-d-arginine) (rPOA), one of the effective non-viral carriers working in vivo, was chosen to deliver HSV-tk to spinal cord tumors which are appropriate targets for suicide gene therapy. Since the system exerts toxicity only in dividing cells, cells in the central nervous system, which are non-proliferative, are not sensitive to the toxic metabolites. In the present study, we demonstrated that the locomotor function of the model rat was maintained through the tumor suppression resulting from the tumor-selective suicide activity by co-administration of rPOA/HSV-tk and GCV. Thus, rPOA plays a crucial role in suicide gene therapy for cancer, and an rPOA/HSV-tk and GCV system could help promote in vivo trials of suicide gene therapy.
Keywords: Suicide gene therapy; Cancer gene therapy; Reducible polymer; Spinal cord tumor
The influence of ligand organization on the rate of uptake of gold nanoparticles by colorectal cancer cells
by Torben Lund; Martina F. Callaghan; Phil Williams; Mark Turmaine; Christof Bachmann; Tom Rademacher; Ivan M. Roitt; Richard Bayford (pp. 9776-9784).
We have explored the uptake of different hydrophilic mono- and dual-ligand gold nanoparticles in colorectal cancer cells in vitro and find that the rate of uptake is dependent on the structural organization of the ligands on the surface of the particles rather than their charge or chemical properties. Gold nanoparticles with 50%PEG-NH2/50% glucose are taken up eighteen fold faster than nanoparticles carrying only PEG-NH2 or glucose. Glutathione-coated gold particles are by far the most efficiently internalized; however, glucose-glutathione dual-ligand nanoparticles are taken up at a thirty fold reduced rate. We found furthermore that the rates are influenced by the cell density and concentration of glucose in the growth medium. Rather than being internalized through a conventional receptor-mediated mechanism the particles appear to be taken up by the cells via an energy-independent diffusion across the cell membrane through pre-existing pores or openings in the lipid bi-layer created by ligands on the gold nanoparticles.
Keywords: Cell culture; Gold nanoparticles; Colon cancer cells; Thiol bonds
Cationic drug-derived nanoparticles for multifunctional delivery of anticancer siRNA
by Rae Sung Chang; Min Sung Suh; Sunil Kim; Gayong Shim; Sangbin Lee; Sung Sik Han; Kyung Eun Lee; Hyesung Jeon; Han-Gon Choi; Yongseok Choi; Chan-Wha Kim; Yu-Kyoung Oh (pp. 9785-9795).
Combined treatment of anticancer drugs and small interfering RNAs (siRNAs) have emerged as a new modality of anticancer therapy. Here, we describe a co-delivery system of anticancer drugs and siRNA in which anticancer drug-derived lipids form cationic nanoparticles for siRNA complexation. The anticancer drug mitoxantrone (MTO) was conjugated to palmitoleic acid, generating two types of palmitoleyl MTO (Pal-MTO) lipids: monopalmitoleyl MTO (mono-Pal-MTO) and dipalmitoleyl MTO (di-Pal-MTO). Among various lipid compositions of MTO, nanoparticles containing mono-Pal-MTO and di-Pal-MTO at a molar ratio of 1:1 (md11-Pal-MTO nanoparticles) showed the most efficient cellular delivery of siRNA, higher than that of Lipofectamine 2000. Delivery of red fluorescence protein-specific siRNA into B16F10-RFP cells using md11-Pal-MTO nanoparticles reduced the expression of RFP at both mRNA and protein levels, demonstrating silencing of the siRNA target gene. Moreover, delivery of Mcl-1-specific anticancer siRNA (siMcl-1) using md11-Pal-MTO enhanced antitumor activity in vitro, reducing tumor cell viability by 81% compared to a reduction of 68% following Lipofectamine 2000-mediated transfection of siMcl-1. Intratumoral administration of siMcl-1 using md11-Pal-MTO nanoparticles significantly inhibited tumor growth, reducing tumor size by 83% compared to untreated controls. Our results suggest the potential of md11-Pal-MTO multifunctional nanoparticles for co-delivery of anticancer siRNAs for effective combination therapy.
Keywords: siRNA; Mitoxantrone; Multifunctional nanoparticles; Co-delivery; Anticancer chemo-gene therapy
Folic acid-conjugated Silica-modified gold nanorods for X-ray/CT imaging-guided dual-mode radiation and photo-thermal therapy
by Peng Huang; Le Bao; Chunlei Zhang; Jing Lin; Teng Luo; Dapeng Yang; Meng He; Zhiming Li; Guo Gao; Bing Gao; Shen Fu; Daxiang Cui (pp. 9796-9809).
Multifunctional nanoprobes are designed to own various functions such as tumor targeting, imaging and selective therapy, which offer great promise for the future of cancer prevention, diagnosis, imaging and treatment. Herein, silica was applied to replace cetyltrimethylammonium bromide (CTAB) molecules on the surface of gold nanorods (GNRs) by the classic Stöber method, thus eliminating their cytotoxicity and improving their biocompatibility. Folic acid molecule was covalently anchored on the surface of GNRs with silane coupling agent. The resultant folic acid-conjugated silica-modified GNRs show highly selective targeting, enhanced radiation therapy (RT) and photo-thermal therapy (PTT) effects on MGC803 gastric cancer cells, and also exhibited strong X-ray attenuation for in vivo X-ray and computed tomography (CT) imaging. In conclusion, the as-prepared nanoprobe is a good candidate with excellent imaging and targeting ability for X-ray/CT imaging-guided targeting dual-mode enhanced RT and PTT.
Keywords: Folic acid; Silica; Gold nanorods; Photo-thermal therapy; Radiation therapy; X-ray imaging
The effect of particle size on the cytotoxicity, inflammation, developmental toxicity and genotoxicity of silver nanoparticles
by Margriet V.D.Z. Park; Arianne M. Neigh; Jolanda P. Vermeulen; Liset J.J. de la Fonteyne; Henny W. Verharen; Jacob J. Briedé; Henk van Loveren; Wim H. de Jong (pp. 9810-9817).
Silver nanoparticles are of interest to be used as antimicrobial agents in wound dressings and coatings in medical devices, but potential adverse effects have been reported in the literature. The most pronounced effect of silver nanoparticles and the role of particle size in determining these effects, also in comparison to silver ions, are largely unknown. Effects of silver nanoparticles of different sizes (20, 80, 113 nm) were compared in in vitro assays for cytotoxicity, inflammation, genotoxicity and developmental toxicity. Silver nanoparticles induced effects in all endpoints studied, but effects on cellular metabolic activity and membrane damage were most pronounced. In all toxicity endpoints studied, silver nanoparticles of 20 nm were more toxic than the larger nanoparticles. In L929 fibroblasts, but not in RAW 264.7 macrophages, 20 nm silver nanoparticles were more cytotoxic than silver ions. Collectively, these results indicate that effects of silver nanoparticles on different toxic endpoints may be the consequence of their ability to inflict cell damage. In addition, the potency of silver in the form of nanoparticles to induce cell damage compared to silver ions is cell type and size-dependent.
Keywords: Nanomaterials; In vitro; assays; Size-related; Silver; Toxicity
Specific labelling of cell populations in blood with targeted immuno-fluorescent/magnetic glyconanoparticles
by Juan Gallo; Isabel García; Nuria Genicio; Daniel Padro; Soledad Penadés (pp. 9818-9825).
Current performance of iron oxide nanoparticle-based contrast agents in clinical use is based on the unspecific accumulation of the probes in certain organs or tissues. Specific targeted biofunctional nanoparticles would significantly increase their potential as diagnostic and therapeutic tools in vivo. In this study, multimodal fluorescent/magnetic glyco-nanoparticles were synthesized from gold-coated magnetite (glyco-ferrites) and converted into specific probes by the covalent coupling of protein G and subsequent incubation with an IgG antibody. The immuno-magnetic-fluorescent nanoparticles were applied to the specific labelling of peripheral blood mononuclear cells (PBMCs) in a complex biological medium, as human blood. We have been able to label specifically PBMCs present in blood in a percentage as low as 0.10–0.17%. Red blood cells (RBCs) were also clearly labelled, even though the inherent T2 contrast arising from the high iron content of these cells (coming mainly from haemoglobin). The labelling was further assessed at cellular level by fluorescence microscopy. In conclusion, we have developed new contrast agents able to label specifically a cell population under adverse biological conditions (low abundance, low intrinsic T2, high protein content). These findings open the door to the application of these probes for the labelling and tracking of endogenous cell populations like metastatic cancer cells, or progenitor stem cells that exist in very low amount in vivo.
Keywords: Fluorescent/magnetic nanoparticles; Specific labelling; Human blood cells; Magnetic resonance imaging; Fluorescence microscopy
A review of the prospects for polymeric nanoparticle platforms in oral insulin delivery
by Mei-Chin Chen; Kiran Sonaje; Ko-Jie Chen; Hsing-Wen Sung (pp. 9826-9838).
Success in the oral delivery of therapeutic insulin can significantly improve the quality of life of diabetic patients who must routinely receive injections of this drug. However, oral absorption of insulin is limited by various physiological barriers and remains a major scientific challenge. Various technological solutions have been developed to increase the oral bioavailability of insulin. Having received considerable attention, nano-sized polymeric particles are highly promising for oral insulin delivery. This review article describes the gastrointestinal barriers to oral insulin delivery, including chemical, enzymatic and absorption barriers. The potential transport mechanisms of insulin delivered by nanoparticles across the intestinal epithelium are also discussed. Finally, recent advances in using polymeric nanoparticles for oral insulin delivery and their effects on insulin transport are reviewed, along with their future.
Keywords: Bioavailability; Transcellular pathway; Paracellular pathway; Target delivery; Formulation technology
PEG-b-PPS-b-PEI micelles and PEG-b-PPS/PEG-b-PPS-b-PEI mixed micelles as non-viral vectors for plasmid DNA: Tumor immunotoxicity in B16F10 melanoma
by Diana Velluto; Susan N. Thomas; Eleonora Simeoni; Melody A. Swartz; Jeffrey A. Hubbell (pp. 9839-9847).
Cationic micelles formed from poly(ethylene glycol)-bl-poly(propylene sulfide)-bl-poly(ethylene imine) (PEG-b-PPS-b-PEI) and from mixtures of poly(ethylene glycol)-bl-poly(propylene sulfide) (PEG-b-PPS) with PEG-b-PPS-b-PEI were explored as non-viral vectors for plasmid DNA (pDNA) transfection in a tumor immunotoxicity model. Complexes with pDNA were found to be templated exclusively by the size of the pDNA-free micelles and ranged from 240 nm (for PEG-b-PPS-b-PEI) to 30 nm (for mixed micelles of PEG-b-PPS/PEG-b-PPS-b-PEI). Both formulations transfected melanoma cells well in vitro. As a model with a functional read-out of tumor cell death, one with likely only small bystander effects, tumors were transfected with an antigen transgene, using an antigen to which the recipient animals had been previously vaccinated with a Th1-biasing adjuvant. Reduction in tumor growth, increase in intratumoral infiltration of cytotoxic T lymphocytes and accumulation of Th1-biasing cytokines indicated that both micelle formulations transfected efficiently compared with naked pDNA and with low cytotoxicity.
Keywords: Copolymer; Micelle; Gene therapy; Immune response
Complementary targeting of liposomes to IL-1α and TNF-α activated endothelial cells via the transient expression of VCAM1 and E-selectin
by Rico C. Gunawan; Dariela Almeda; Debra T. Auguste (pp. 9848-9853).
Inflammation is in part defined by the transient upregulation of cell adhesion molecules on the surface of endothelial cells (ECs) in response to cytokines. We hypothesized that liposomes with a complementary surface presentation of antibodies to the pattern of molecules on the EC surface may enhance targeting. We quantified the expression of vascular cell adhesion molecule-1 (VCAM1) and endothelial leukocyte cell adhesion molecule-1 (E-selectin) on ECs upon exposure to either tumor necrosis factor-α (TNF-α) or interleukin-1α (IL-1α) as a function of time. Liposomes, composed of 95 mol% dioleoyl phosphatidylcholine (DOPC) and 5 mol% dodecanyl phosphatidylethanolamine (N-dod-PE), were prepared by conjugating different molar ratios of antibodies against VCAM1 (aVCAM1) and E-selectin (aE-selectin). Increased binding was observed when immunoliposomes complemented the presentation of VCAM1:E-selectin expressed on TNF-α activated ECs. The 1:1 aVCAM1:aE-selectin liposomes had maximal binding at both 6 and 24 h on IL-1α activated ECs due to differences in molecular organization. The results demonstrate that liposomes targeting to inflamed endothelium may be optimized by exploiting the dynamic expression of VCAM1 and E-selectin on the EC surface.
Keywords: Liposome; Inflammation; Endothelial cell; E-selectin; VCAM1; Transient
The significance of plasmid DNA preparations contaminated with bacterial genomic DNA on inflammatory responses following delivery of lipoplexes to the murine lung
by Reto P. Bazzani; Ying Cai; Henry L. Hebel; Stephen C. Hyde; Deborah R. Gill (pp. 9854-9865).
Non-viral gene transfer using plasmid DNA (pDNA) is generally acknowledged as safe and non-immunogenic compared with the use of viral vectors. However, pre-clinical and clinical studies have shown that non-viral (lipoplex) gene transfer to the lung can provoke a mild, acute inflammatory response, which is thought to be, partly, due to unmethylated CG dinucleotides (CpGs) present in the pDNA sequence. Using a murine model of lung gene transfer, bronchoalveolar lavage fluid was collected following plasmid delivery and a range of inflammatory markers was analysed. The results showed that a Th1-related inflammatory cytokine response was present that was substantially reduced, though not abolished, by using CpG-free pDNA. The remaining minor level of inflammation was dependent on the quality of the pDNA preparation, specifically the quantity of contaminating bacterial genomic DNA, also a source of CpGs. Successful modification of a scalable plasmid manufacturing process, suitable for the production of clinical grade pDNA, produced highly pure plasmid preparations with reduced genomic DNA contamination. These studies help define the acceptable limit of genomic DNA contamination that will impact FDA/EMEA regulatory guidelines defining clinical grade purity of plasmid DNA for human use in gene therapy and vaccination studies.
Keywords: Cytokine; Bacterial genomic DNA; Gene therapy; Lung inflammation; Lipoplex; Plasmid
The effect of micro and nanotopography on endocytosis in drug and gene delivery systems
by Benjamin K.K. Teo; Seok-Hong Goh; Tanu S. Kustandi; Wei Wei Loh; Hong Yee Low; Evelyn K.F. Yim (pp. 9866-9875).
Endocytosis is a fundamental biological process and is also the key mechanism for drug and non-viral gene delivery. The importance of topographical cues in modulating cell behaviors has become increasingly evident, but the influence of topography on endocytosis has however only been sparsely studied. We hypothesize that topography can enhance cellular endocytosis, and in turn the non-viral transfection efficiency. Nano- to microtopographical patterns were fabricated using nano-imprinting lithography (NIL). We first investigated if the substrate topographies could modulate endocytosis and in turn the cellular transfectability. Our results showed increased internalization of fluorescently labeled dextran by human mesenchymal stem cells (hMSCs) and monkey kidney fibroblasts (COS7) when they were cultured on micro- and nanopillars. When the hMSCs were introduced to green-fluorescent protein (GFP) encoding plasmid with Lipofectamine, highest transfection efficiency was observed in cells on nanopillars. Tunable detachable substrate topographies were also fabricated using NIL to promote endocytosis in different cell types, and our results show hMSCs phagocytosis of these polymeric structures. Besides being important in understanding the fundamental process of endocytosis, the current research results may also lead to applications utilizing nanotopography to enhance drug and gene delivery.
Keywords: Topography; Nanoimprinting; Non-viral transfection; Human mesenchymal stem cells; Phagocytosis; Transfection efficiency
Multi-functional core-shell hybrid nanogels for pH-dependent magnetic manipulation, fluorescent pH-sensing, and drug delivery
by Weitai Wu; Jing Shen; Zheng Gai; Kunlun Hong; Probal Banerjee; Shuiqin Zhou (pp. 9876-9887).
Remotely optical sensing and drug delivery using an environmentally-guided magnetically-driven hybrid nanogel particle could allow for medical diagnostics and treatment. Such multifunctional hybrid nanogels (<200 nm) were prepared through the first synthesis of magnetic Ni NPs, followed by a moderate growth of fluorescent metallic Ag on the surface of Ni NPs, and then a coverage of a pH-responsive copolymer gel shell of poly(ethylene glycol- co-methacrylic acid) [p(EG-MAA)] onto the Ni-Ag bimetallic NP cores (18 ± 5 nm). The introduction of the pH-responsive p(EG-MAA) gel shell onto the magnetic and fluorescent Ni-Ag NPs makes the polymer-bound Ni-Ag NPs responsive to pH over the physiologically important range 5.0–7.4. The hybrid nanogels can adapt to surrounding pH and regulate the sensitivity in response to external magnetic field (such as a small magnet of 0.1 T), resulting in the accumulation of the hybrid nanogels within the duration from hours to a few seconds as the pH value decreases from 7.4 to 5.0. The pH-dependent magnetic response characteristic of the hybrid nanogels were further integrated with the pH change to fluorescent signal transduction and pH-regulated anticancer drug (a model drug 5-fluorouracil) delivery functions. The hybrid nanogels can overcome cellular barriers to enter the intracellular region and light up the mouse melanoma B16F10 cells. The multiple responsive hybrid nanogel that can be manipulated in tandem endogenous and exogenous activation should enhance our ability to address the complexity of biological systems.
Keywords: Hybrid nanogels; Ni-Ag bimetallic nanoparticle; pH-responsive; Magnetic manipulation; Biosensor; Drug delivery
Low molecular weight protamine-functionalized nanoparticles for drug delivery to the brain after intranasal administration
by Huimin Xia; Xiaoling Gao; Guangzhi Gu; Zhongyang Liu; Ni Zeng; Quanyin Hu; Qingxiang Song; Lei Yao; Zhiqing Pang; Xinguo Jiang; Jun Chen; Hongzhuan Chen (pp. 9888-9898).
The development of new strategies for enhancing drug delivery to the brain is of great importance in diagnostics and therapeutics of central nervous diseases. Low-molecular-weight protamine (LMWP) as a cell-penetrating peptide possesses distinct advantages including high cell translocation potency, absence of toxicity of peptide itself, and the feasibility as an efficient carrier for delivering therapeutics. Therefore, it was hypothesized that brain delivery of nanoparticles conjugated with LMWP should be efficiently enhanced following intranasal administration. LMWP was functionalized to the surface of PEG-PLA nanoparticles (NP) via a maleimide-mediated covalent binding procedure. Important parameters such as particle size distribution, zeta potential and surface content were determined, which confirmed the conjugation of LMWP to the surface of nanoparticle. Using 16HBE14o- cells as the cell model, LMWP-NP was found to exhibit significantly enhanced cellular accumulation than that of unmodified NP via both lipid raft-mediated endocytosis and direct translocation processes without causing observable cytotoxic effects. Following intranasal administration of coumarin-6-loaded LMWP–NP, the AUC0–8 h of the fluorescent probe detected in the rat cerebrum, cerebellum, olfactory tract and olfactory bulb was found to be 2.03, 2.55, 2.68 and 2.82 folds, respectively, compared to that of coumarin carried by NP. Brain distribution analysis suggested LMWP-NP after intranasal administration could be delivered to the central nervous system along both the olfactory and trigeminal nerves pathways. The findings clearly indicated that the brain delivery of nanoparticles could be greatly facilitated by LMWP and the LMWP-functionalized nanoparticles appears as a effective and safe carrier for nose-to-brain drug delivery in potential diagnostic and therapeutic applications.
Keywords: Brain targeting; Low molecular weight protamine; Nanoparticles; Intranasal administration
Cadherin-integrated liposomes with potential application in a drug delivery system
by Koki Kamiya; Kanta Tsumoto; Tetsuro Yoshimura; Kazunari Akiyoshi (pp. 9899-9907).
N-cadherin (CDH2) proteins were reconstituted with liposomes using a baculovirus expression-liposome fusion method. CDH2 budded viruses were fused with giant liposomes containing dioleoylphophogycerol/dioleoylphosphatidylcholine (DOPG/DOPC) at pH 4.5 and the localization of CDH2 on the liposome membrane was observed by confocal laser scanning microscopy. CDH2 liposomes showed Ca2+-dependent association. CDH2-mediated association/dissociation in CDH2 liposomes was specific to Ca2+ and reversible. CDH2-expressing LN-229 cells (human glioblastoma cell) adhered to CDH2 liposomes and small CDH2 liposomes (diameter approximately 150 nm), in particular, were internalized by endocytosis and partly escaped endosomes. Cadherin-containing liposomes show high potential as a new cell-specific proteoliposome. The baculovirus expression-liposome fusion method is useful as a new enabling technology for biomedical applications of functional proteoliposomes.
Keywords: Liposome; Membrane protein; Proteoliposome; Cadherin; Baculovirus
Accelerated gene transfer through a polysorbitol-based transporter mechanism
by Mohammad Ariful Islam; Cheol-Heui Yun; Yun-Jaie Choi; Ji-Young Shin; Rohidas Arote; Hu-Lin Jiang; Sang-Kee Kang; Jae-Woon Nah; In-Kyu Park; Myung-Haing Cho; Chong-Su Cho (pp. 9908-9924).
Here we report an accelerated gene transfer through a polysorbitol-based osmotically active transporter (PSOAT) that shows several surprising results through interesting mechanisms. The nano-sized and well-complexed PSOAT/DNA particles are less toxic, stable at serum and show no aggregation after lyophilization due to their polysorbitol backbone. The transfection is remarkably accelerated both in vitro and in vivo, presumably due to a transporter mechanism of PSOAT in spite of possibility of reduction of transfection by many hydroxyl groups in the transporter. PSOAT possesses a transporter mechanism owing to its polysorbitol backbone, which enhances cellular uptake by exerting polysorbitol transporter activity, thus accelerates gene transfer to cells because transfection ability of PSOAT is drastically reduced in the presence of a cyclooxygenase (COX)-2-specific inhibitor, which we have reported as an inhibitor of the transporter to cells. Moreover, the gene expression is found to be enhanced by hyperosmotic activity and buffering capacity due to polysorbitol and polyethylenimine backbone of PSOAT, respectively. The polysorbitol in PSOAT having polyvalency showed more efficiency in accelerating gene transfer capability than monovalent sorbitol. The above interesting mechanisms display PSOAT as a remarkably potential system to deliver therapeutic (small interfering RNA) and diagnostic agents for effective treatment of cancer.
Keywords: Gene transfer; Polysorbitol; Transporter; COX-2 inhibitor; Accelerated transfection
A strategy to improve serum-tolerant transfection activity of polycation vectors by surface hydroxylation
by Xiao-hua Luo; Fu-wei Huang; Si-yong Qin; Hua-fen Wang; Jun Feng; Xian-zheng Zhang; Ren-xi Zhuo (pp. 9925-9939).
The aim of this contribution is to develop a universal method to promote the serum-tolerant capability of polycation-based gene delivery system. A “hydroxylation camouflage” strategy was put forward by coating the polycation vectors with hydroxyl-enriched “skin”. Branched polyethyleneimine (PEI) was herein used as the polycation model and modified via the catalyst-free aminolysis reaction with 5-ethyl-5-(hydroxymethyl)-1,3-dioxan-2-oxo (EHDO). PEI-g-EHDO, PEI and alkylated PEI derivative termed as PEI-g-DPA were comparatively explored with respect to the transfection efficiency in the serum-free and serum-conditioned medium. The resultant data indicate that the serum-tolerant capability largely depended on the surface composition and substitution degree. In addition to the reduced surface charge, the introduced function caused by hydroxyl coating is believed to play a crucial role for the improved properties of PEI-g-EHDOs. The EHDO modification can effectively inhibit the adsorption of BSA proteins onto polyplexes surface. And the polyplexes stability was remarkably enhanced in the presence of DNase and heparin after EHDO modification. Note that the transfection activity of PEI-g-EHDO34.5% in the serum-conditioned medium was even higher than that without serum addition. In contrast, serum addition led to appreciable reduction in the transfection efficiency mediated by PEI and PEI-g-DPAs. Specifically, as far as the transfection activity in the presence of serum is concerned, PEI-g-EHDO could be up to 30-fold higher than unmodified PEI25k. PEI-g-EHDO34.5% displayed little to no hemolytic effect and high cell-biocompatibility with nearly no cytotoxicity detected in 293T cells and HeLa cells. Taking into account the high biocompatibility and serum-tolerant transfection activity, PEI-g-EHDO34.5% holds great potential for the use as efficient gene vector. More importantly, it is expected that such “hydroxylation camouflage” strategy may be universally applicable for a majority of existing polycation vectors.
Keywords: Polycation vector; Hydroxylation camouflage; Serum-tolerance; Gene transfection; Cell-biocompatibility
Synthesis and immunomodulatory activity of fullerene–tuftsin conjugates
by Yingying Xu; Jiadan Zhu; Kun Xiang; Yuankai Li; Ronghua Sun; Jie Ma; Hongfang Sun; Yuanfang Liu (pp. 9940-9949).
Immunomodulating peptide tuftsin (Thr-Lys-Pro-Arg) was covalently conjugated to fullerene C60 by two different ways to prepare NH2–tuftsin–C60 and C60–tuftsin–COOH. The two new compounds were intensively characterized. The synthetic C60–tuftsin conjugates were assayed for their stability against leucine aminopeptidase degradation. And the immunostimulating activities to murine peritoneal macrophages were investigated in vitro. Compared with the natural tuftsin, significant enhancement of phagocytosis, chemotaxis activities and major histocompatibility complex class II (MHC II) molecule expression were observed in macrophages stimulated by both of the conjugates. The two conjugates also exhibit complete resistance to enzymatic hydrolysis, and they are non-toxic to macrophages in the tested concentrations. On all accounts, these results suggest that the C60–tuftsin conjugates can be used as potential candidates of immunomodulators and vaccine adjuvants.
Keywords: Fullerene C; 60; Tuftsin; Peritoneal macrophages; Phagocytosis; Chemotaxis; MHC II
Design of interior-functionalized fully acetylated dendrimers for anticancer drug delivery
by Jingjing Hu; Yunzhang Su; Hongfeng Zhang; Tongwen Xu; Yiyun Cheng (pp. 9950-9959).
In this study, dendrimers was synthesized by introducing functional groups into the interior pockets of fully acetylated dendrimers. NMR techniques including COSY and 2D-NOESY revealed the molecular structures of the synthesized dendrimers and the encapsulation of guest molecule such as methotrexate within their interior pockets. The synthesized polymeric nanocarriers showed much lower cytotoxicity on two cell lines than cationic dendrimers, and exhibited better performance than fully acetylated dendrimers in the sustained release of methotrexate. The results provided a new strategy in the design of non-toxic dendrimers with high performance in the delivery of anti-cancer drugs for clinical applications.
Keywords: Dendrimer; Interior-functionalized; Non-toxic; Acetylation; NMR