International Journal of Pharmaceutics (v.523, #2)

Special issue on biomaterials for tissue engineering by María J. Blanco-Prieto; Elisa Garbayo (439-440).

Display OmittedThe development of biomimetic highly-porous scaffolds is essential for successful tissue engineering. Electrospun nanofibers are highly versatile platforms for a broad range of applications in different research areas. In the biomedical field, micro/nanoscale fibrous structures have gained great interest for wound dressings, drug delivery systems, soft and hard-tissue engineering scaffolds, enzyme immobilization, among other healthcare applications. In this mini-review, electrospun gelatin-based scaffolds for a variety of tissue engineering applications, such as bone, cartilage, skin, nerve, and ocular and vascular tissue engineering, are reviewed and discussed. Gelatin blends with natural or synthetic polymers exhibit physicochemical, biomechanical, and biocompatibility properties very attractive for scaffolding. Current advances and challenges on this research field are presented.
Keywords: Gelatin; Electrospun scaffolds; Tissue engineering; Biopolymers;

Hydrogel based approaches for cardiac tissue engineering by Laura Saludas; Simon Pascual-Gil; Felipe Prósper; Elisa Garbayo; María Blanco-Prieto (454-475).
Display OmittedHeart failure still represents the leading cause of death worldwide. Novel strategies using stem cells and growth factors have been investigated for effective cardiac tissue regeneration and heart function recovery. However, some major challenges limit their translation to the clinic. Recently, biomaterials have emerged as a promising approach to improve delivery and viability of therapeutic cells and proteins for the regeneration of the damaged heart. In particular, hydrogels are considered one of the most promising vehicles. They can be administered through minimally invasive techniques while maintaining all the desirable characteristics of drug delivery systems. This review discusses recent advances made in the field of hydrogels for cardiac tissue regeneration in detail, focusing on the type of hydrogel (conventional, injectable, smart or nano- and micro-gel), the biomaterials used for its manufacture (natural, synthetic or hybrid) and the therapeutic agent encapsulated (stem cells or proteins). We expect that these novel hydrogel-based approaches will open up new possibilities in drug delivery and cell therapies.
Keywords: Myocardial infarction; Cell therapy; Protein therapy; Hydrogel; Biomaterial; Tissue engineering;

Tailoring biomaterial scaffolds for osteochondral repair by Sandra Camarero-Espinosa; Justin Cooper-White (476-489).
Display OmittedArticular cartilage is a mechanically and structurally complex, lubricious tissue that permits load-bearing and frictionless movement of our joints upon articulation. Unfortunately, cartilage is unable to properly self-heal as a result of acute trauma or damage, resulting in many cases in significant pain, reduction in physical activity and quality of life for the patient. Due to the inability of resident cells to repair damaged osteochondral tissue, researchers have focused on utilizing endogenously or exogenously sourced cells (chondrocytes or tissue-derived mesenchymal stem cells), with or without scaffolds, to encourage the secretion of extracellular matrix (ECM) that replicates this highly anisotropic osteochondral tissue, in which the phenotype of the cells and the composition and orientation of the ECM varies along its depth. Important advances have been achieved towards the development of scaffolds with macroscopically relevant structures, however, articular cartilage and bone tissue contain complex, hierarchical structures that provide cells with biophysical and biochemical cues spanning multiple length scales, presenting researchers with some substantial challenges. This review summarizes the latest advances in mechanical, biochemical and topographical engineering of biomaterials to drive requisite biological responses, such as cell differentiation and matrix deposition, in an effort to achieve functional repair of osteochondral defects.
Keywords: Tissue engineering; Cartilage; Osteochondral; Surface engineering; Biomaterial; Scaffold;

Biomaterials to suppress cancer stem cells and disrupt their tumoral niche by Carla Garcia-Mazas; Noemi Csaba; Marcos Garcia-Fuentes (490-505).
Display OmittedLack of improvement in the treatment options of several types of cancer can largely be attributed to the presence of a subpopulation of cancer cells with stem cell signatures and to the tumoral niche that supports and protects these cells. This review analyses the main strategies that specifically modulate or suppress cancer stem cells (CSCs) and the tumoral niche (TN), focusing on the role of biomaterials (i.e. implants, nanomedicines, etc.) in these therapies. In the case of CSCs, we discuss differentiation therapies and the disruption of critical cellular signaling networks. For the TN, we analyze diverse strategies to modulate tumor hypervascularization and hypoxia, tumor extracellular matrix, and the inflammatory and tumor immunosuppressive environment. Due to their capacity to control drug disposition and integrate diverse functionalities, biomaterial-based therapies can provide important benefits in these strategies. We illustrate this by providing case studies where biomaterial-based therapies either show CSC suppression and TN disruption or improved delivery of major modulators of these features. Finally, we discuss the future of these technologies in the framework of these emerging therapeutic concepts.
Keywords: Cancer stem cells; Tumor initiating cells; Tumor niche; Biomaterials; Tissue engineering; Drug delivery; Nanomedicine;

Nanoprecipitated catestatin released from pharmacologically active microcarriers (PAMs) exerts pro-survival effects on MSC by C Angotti; M.C. Venier-Julienne; C Penna; S Femminò; L Sindji; C Paniagua; C.N. Montero-Menei; P Pagliaro (506-514).
Display OmittedCatestatin (CST), a fragment of Chromogranin-A, exerts angiogenic, arteriogenic, vasculogenic and cardioprotective effects. CST is a very promising agent for revascularization purposes, in “NO―OPTION” patients. However, peptides have a very short half-life after administration and must be conveniently protected. Fibronectin-coated pharmacologically active microcarriers (FN-PAM), are biodegradable and biocompatible polymeric microspheres that can convey mesenchymal stem cell (MSCs) and therapeutic proteins delivered in a prolonged manner. In this study, we first evaluated whether a small peptide such as CST could be nanoprecipitated and incorporated within FN-PAMs. Subsequently, whether CST may be released in a prolonged manner by functionalized FN-PAMs (FN-PAM-CST). Finally, we assessed the effect of CST released by FN-PAM-CST on the survival of MSCs under stress conditions of hypoxia-reoxygenation. An experimental design, modifying three key parameters (ionic strength, mixing and centrifugation time) of protein nanoprecipitation, was used to define the optimum condition for CST. An optimal nanoprecipitation yield of 76% was obtained allowing encapsulation of solid CST within FN-PAM-CST, which released CST in a prolonged manner. In vitro, MSCs adhered to FN-PAMs, and the controlled release of CST from FN-PAM-CST greatly limited hypoxic MSC-death and enhanced MSC-survival in post-hypoxic environment. These results suggest that FN-PAM-CST are promising tools for cell-therapy.
Keywords: Microcarriers; Drug delivery; Catestatin; Mesenchymal stem cells; Hypoxia;

Long term performance evaluation of small-diameter vascular grafts based on polyvinyl alcohol hydrogel and dextran and MSCs-based therapies using the ovine pre-clinical animal model by Nuno Alexandre; Irina Amorim; Ana Rita Caseiro; Tiago Pereira; Rui Alvites; Alexandra Rêma; Ana Gonçalves; Guilherme Valadares; Elísio Costa; Alice Santos-Silva; Miguel Rodrigues; Maria Ascensão Lopes; André Almeida; José Domingos Santos; Ana Colette Maurício; Ana Lúcia Luís (515-530).
Display OmittedThe functional and structural performance of a 5 cm synthetic small diameter vascular graft (SDVG) produced by the copolymerization of polyvinyl alcohol hydrogel with low molecular weight dextran (PVA/Dx graft) associated to mesenchymal stem cells (MSCs)-based therapies and anticoagulant treatment with heparin, clopidogrel and warfarin was tested using the ovine model during the healing period of 24 weeks. The results were compared to the ones obtained with standard expanded polyetetrafluoroethylene grafts (ePTFE graft). Blood flow, vessel and graft diameter measurements, graft appearance and patency rate (PR), thrombus, stenosis and collateral vessel formation were evaluated by B-mode ultrasound, audio and color flow Doppler. Graft and regenerated vessels morphologic evaluation was performed by scanning electronic microscopy (SEM), histopathological and immunohistochemical analysis. All PVA/Dx grafts could maintain a similar or higher PR and systolic/diastolic laminar blood flow velocities were similar to ePTFE grafts. CD14 (macrophages) and α-actin (smooth muscle) staining presented similar results in PVA/Dx/MSCs and ePTFE graft groups. Fibrosis layer was lower and endothelial cells were only detected at graft-artery transitions where it was added the MSCs. In conclusion, PVA/Dx graft can be an excellent scaffold candidate for vascular reconstruction, including clinic mechanically challenging applications, such as SDVGs, especially when associated to MSCs-based therapies to promote higher endothelialization and lower fibrosis of the vascular prosthesis, but also higher PR values.
Keywords: PVA; Dextran; Synthetic small diameter vascular graft; Mesenchymal stem cells; Ovine model;

Cytokine-loaded PLGA and PEG-PLGA microparticles showed similar heart regeneration in a rat myocardial infarction model by Simon Pascual-Gil; Teresa Simón-Yarza; Elisa Garbayo; Felipe Prósper; María J. Blanco-Prieto (531-533).
Display OmittedNeuregulin (NRG1) and fibroblast growth factor (FGF1) are well known growth factors implicated in cardiomyocyte proliferation and survival, as well as in angiogenesis, the development of adult heart and the maintenance of cardiac function. NRG1 and FGF1 have become promising therapeutic agents to treat myocardial infarction (MI) disorder. Unfortunately, clinical trials performed so far reported negative efficacy results, because growth factors are rapidly degraded and eliminated from the biological tissues once administered. In order to increase their bioavailability and favour their therapeutic effects, they have been combined with poly(lactic-co-glycolic acid) and polyethylene glycol microparticles (PLGA MPs and PEG-PLGA MPs). Here we compare both types of microparticles loaded with NRG1 or FGF1 in terms of efficacy in a rat MI model. Our results showed that intramyocardial injection of NRG1 or FGF1-loaded PLGA and PEG-PLGA MPs brought about similar improvements in the ejection fraction, angiogenesis and arteriogenesis after administration into the infarcted hearts. PEG coating did not add any effect regarding MP efficacy. Both PLGA and PEG-PLGA MPs were equally phagocyted in the heart. To our knowledge, this is the first study analysing the opsonisation process in heart tissue. The results allow us to conclude that the opsonisation process is different in heart tissue compared to blood.
Keywords: Myocardial infarction; Protein therapy; Microparticles; Controlled release; Efficacy; PEGylation;

Bovine bone matrix/poly(l-lactic-co-ε-caprolactone)/gelatin hybrid scaffold (SmartBone®) for maxillary sinus augmentation: A histologic study on bone regeneration by Delfo D’Alessandro; Giuseppe Perale; Mario Milazzo; Stefania Moscato; Cesare Stefanini; Gianni Pertici; Serena Danti (534-544).
Display OmittedThe ideal scaffold for bone regeneration is required to be highly porous, non-immunogenic, biostable until the new tissue formation, bioresorbable and osteoconductive. This study aimed at investigating the process of new bone formation in patients treated with granular SmartBone® for sinus augmentation, providing an extensive histologic analysis. Five biopsies were collected at 4–9 months post SmartBone® implantation and processed for histochemistry and immunohistochemistry. Histomorphometric analysis was performed. Bone-particle conductivity index (BPCi) was used to assess SmartBone® osteoconductivity.At 4 months, SmartBone® (12%) and new bone (43.9%) were both present and surrounded by vascularized connective tissue (37.2%). New bone was grown on SmartBone® (BPCi = 0.22). At 6 months, SmartBone® was almost completely resorbed (0.5%) and new bone was massively present (80.8%). At 7 and 9 months, new bone accounted for a large volume fraction (79.3% and 67.4%, respectively) and SmartBone® was resorbed (0.5% and 0%, respectively). Well-oriented lamellae and bone scars, typical of mature bone, were observed. In all the biopsies, bone matrix biomolecules and active osteoblasts were visible. The absence of inflammatory cells confirmed SmartBone® biocompatibility and non-immunogenicity. These data indicate that SmartBone® is osteoconductive, promotes fast bone regeneration, leading to mature bone formation in about 7 months.
Keywords: Maxillary bone; Tissue engineering; Dental implants; Histology; Scaffold; Sinus lift;

Display OmittedThis study describes the use of a set of protein-based biomaterials that allow us to explore the mechanism of cell-mediated 3-D invasion associated with peripheral nerve regeneration. Hydrogels made from poly(ethylene glycol) (PEG) conjugated extracellular matrix proteins, including fibrinogen, gelatin and albumin were compared in their ability to support the neurite extension and glial cell migration from dorsal root ganglion (DRG) as compared to PEG only hydrogel controls. The synthetic polymer in the system provides a cross-linked network with controlled mechanical properties and degradation, whereas the protein components provide the unique extracellular matrix (ECM) for controlling neuronal cell morphogenesis. A range of hydrogel compositions were found to support DRG cell outgrowth, based on the mechanical properties, density and proteolytic degradation of the matrix. The 3-D invasion and morphogenesis of newly grown neurites and glial cells in the different materials were characterized and correlated to the properties of the scaffolds. The DRG cell outgrowth was highly correlated with the density of different hydrogel compositions.
Keywords: Semi-synthetic; Hydrogel scaffold; Tissue engineering; Nerve guidance conduit; Fibrinogen; Gelatin; Albumin; PEG;

Novel nanofibrous dressings containing rhEGF and Aloe vera for wound healing applications by Itxaso Garcia-Orue; Garazi Gainza; Franciso Borja Gutierrez; Jose Javier Aguirre; Carmen Evora; Jose Luis Pedraz; Rosa Maria Hernandez; Araceli Delgado; Manoli Igartua (556-566).
Display OmittedNanofibrous membranes produced by electrospinning possess a large surface area-to-volume ratio, which mimics the three-dimensional structure of the extracellular matrix. Thus, nanofibrous dressings are a promising alternative for chronic wound healing, since they can replace the natural ECM until it is repaired. Therefore, in this study we have developed a PLGA nanofibrous membrane that contains recombinant human Epidermal Growth Factor (rhEGF) and Aloe vera (AV) extract. Both of them promote wound healing, as EGF is a wound healing mediator and AV stimulates the proliferation and activity of fibroblast. The obtained membranes were composed of uniform and randomly oriented fibers with an average diameter of 356.03 ± 112.05 nm, they presented a porosity of 87.92 ± 11.96% and the amount of rhEGF was 9.76 ± 1.75 μg/mg. The in vitro viability assay demonstrated that the membranes containing rhEGF and AV improved fibroblast proliferation, revealing the beneficial effect of the combination. Furthermore, these membranes accelerated significantly wound closure and reepithelisation in an in vivo full thickness wound healing assay carried out in db/db mice. Overall, these findings demonstrated the potential of PLGA nanofibers containing rhEGF and AV for the treatment of chronic wounds.
Keywords: Wound healing; Electrospinning; Wound dressing; rhEGF; Growth factors; Aloe vera;