Frontiers of Materials Science (v.8, #4)

Physical modification of polyetheretherketone for orthopedic implants by Ya-Wei Du; Li-Nan Zhang; Zeng-Tao Hou; Xin Ye; Hong-Sheng Gu; Guo-Ping Yan; Peng Shang (313-324).
Polyetheretherketone (PEEK) is regarded as one of the most potential candidates for replacing current implant applications. To obtain good bone-implant interfaces, many modification methods have been developed to enable PEEK and PEEK-based composites from bio-inert to bioactive. Among them, physical methods have aroused significant attention and been widely used to modify PEEK for orthopedic implants. This review summarizes current physical modification techniques of PEEK for orthopedic applications, which include composite strategies, surface coating methods and irradiation treatments. The positive consequences of those modification methods will encourage continuing investigations and stimulate the wide range of applications of PEEK-based implants in orthopedics.
Keywords: polyetheretherketone (PEEK); modification; bioactivity; bone-implant interface

Modification of biomaterials surface by mimetic cell membrane for improving biocompatibility, to imitate the excellent biological and physiological properties of the natural cell membrane, is an important research area in materials science. Numerous studies have been attempted to construct a mimetic cell membrane biointerface composed of phosphorylcholine (PC)-containing polymers or other phospholipid analogues on biomaterials surface. PC-containing biointerfaces show outstanding characteristics, especially in biological aspects such as blood compatibility and antifouling property. In this mini-review, the strategies of membrane mimetic modification of biomaterials and their antifouling applications are summarized.
Keywords: mimetic cell membrane; phosphorylcholine (PC); biocompatibility; surface modification; biomaterial

To improve the anti-tumor activity of hydrophobic drug curcumin, we prepared curcumin-loaded PLGA nanoparticles (PLGA-Cur NPs) through a modified spontaneous emulsification solvent diffusion (modified-SESD) method. The influence of main preparation parameters was investigated, such as the volume ratio of binary organic solvents and the concentration of surfactant. Results indicated that the synthesized regular spherical PLGA NPs with the average diameter of 189.7 nm exhibited relatively higher yield (58.9%), drug loading (11.0% (w/w)) and encapsulation efficiency (33.5%), and also a controllable drug release profile. In order to evaluate the in vitro cytotoxicity of the prepared NPs, MTT assay was conducted, and results showed that the NPs could effectively inhibit HL60 and HepG2 cells with lower IC50 values compared with free curcumin. Furthermore, confocal microscopy together with flow cytometry analysis proved the enhanced apoptosis-inducing ability of PLGA-Cur NPs. Polymeric NP formulations are potential to be used for hydrophobic drug delivery systems in cancer therapy.
Keywords: curcumin; PLGA nanoparticle; modified spontaneous emulsification solvent diffusion (modified-SESD); anti-tumor

In vitro degradation of MAO/PLA coating on Mg-1.21Li-1.12Ca-1.0Y alloy by Rong-Chang Zeng; Wei-Chen Qi; Ying-Wei Song; Qin-Kun He; Hong-Zhi Cui; En-Hou Han (343-353).
Magnesium and its alloys are promising biomaterials due to their biocompatibility and osteoinduction. The plasticity and corrosion resistance of commercial magnesium alloys cannot meet the requirements for degradable biomaterials completely at present. Particularly, the alkalinity in the microenvironment surrounding the implants, resulting from the degradation, arouses a major concern. Micro-arc oxidation (MAO) and poly(lactic acid) (PLA) composite (MAO/PLA) coating on biomedical Mg-1.21Li-1.12Ca-1.0Y alloy was prepared to manipulate the pH variation in an appropriate range. Surface morphologies were discerned using SEM and EMPA. And corrosion resistance was evaluated via electrochemical polarization and impedance and hydrogen volumetric method. The results demonstrated that the MAO coating predominantly consisted of MgO, Mg2SiO4 and Y2O3. The composite coating markedly improved the corrosion resistance of the alloy. The rise in solution pH for the MAO/PLA coating was tailored to a favorable range of 7.5–7.8. The neutralization caused by the alkalinity of MAO and Mg substrate and acidification of PLA was probed. The result designates that MAO/PLA composite coating on Mg-1.21Li-1.12Ca-1.0Y alloys may be a promising biomedical coating.
Keywords: magnesium alloy; micro-arc oxidation (MAO); poly(lactic acid) (PLA); biomaterial; degradation

Fabrication and characterization of curcumin-loaded silk fibroin/P(LLA-CL) nanofibrous scaffold by Yuan Lian; Jian-Chao Zhan; Kui-Hua Zhang; Xiu-Mei Mo (354-362).
Curcumin exhibited excellent properties including antioxidant, antiinflammatory, antiviral, antibacterial, antifungal, anticancer, and anticoagulant activities. In this study, curcumin was incorporated into silk fibroin (SF)/poly(L-lactic acid-co-e-caprolactone) (P(LLA-CL)) nanofibrous scaffolds via electrospinning, and changes brought about by raising the curcumin content were observed: SEM images showed that the average nanofibrous diameter decreased at the beginning and then increased, and the nanofibers became uniform; FTIR showed that the conformation of SF transforming from random coil form to β-sheet structure had not been induced, while SF conformation converted to β-sheet after being treated with 75% ethanol vapor; XRD results confirmed that the crystal structure of (P(LLA-CL)) had been destroyed; The mechanical test illustrated that nanofibrous scaffolds still maintained good mechanical properties. Further, curcumin-loaded nanofibrous scaffolds were evaluated for drug release, antioxidant and antimicrobial activities in vitro. The results showed that curcumin presented a sustained release behavior from nanofibrous scaffolds and maintained its free radical scavenging ability, and such scaffolds could effectively inhibit S. aureus growth (> 95%). Thus, curcumin-loaded SF/P(LLA-CL) nanofibrous scaffolds might be potential candidates for wound dressing and tissue engineering scaffolds.
Keywords: curcumin; SF/P(LLA-CL); nanofibrous scaffold; control release

Glucose-conjugated chitosan nanoparticles for targeted drug delivery and their specific interaction with tumor cells by Jing Li; Fang-Kui Ma; Qi-Feng Dang; Xing-Guo Liang; Xi-Guang Chen (363-372).
A novel targeted drug delivery system, glucose-conjugated chitosan nanoparticles (GCNPs), was developed for specific recognition and interaction with glucose transporters (Gluts) over-expressed by tumor cells. GC was synthesized by using succinic acid as a linker between glucosamine and chitosan (CS), and successful synthesis was confirmed by NMR and elemental analysis. GCNPs were prepared by ionic crosslinking method, and characterized in terms of morphology, size, and zeta potential. The optimally prepared nanoparticles showed spherical shapes with an average particle size of (187.9 ± 3.8) nm and a zeta potential of (− 15.43 ± 0.31) mV. The GCNPs showed negligible cytotoxicity to mouse embryo fibroblast and 4T1 cells. Doxorubicin (DOX) could be efficiently entrapped into GCNPs, with a loading capacity and encapsulation efficiency of 20.11% and 64.81%, respectively. DOX-loaded nanoparticles exhibited sustained-release behavior in phosphate buffered saline (pH 7.4). In vitro cellular uptake studies showed that the GCNPs had better endocytosis ability than CSNPs, and the antitumor activity of DOX/GCNPs was 4–5 times effectiveness in 4T1 cell killing than that of DOX/CSNPs. All the results demonstrate that nanoparticles decorated with glucose have specific interactions with cancer cells via the recognition between glucose and Gluts. Therefore, Gluts-targeted GCNPs may be promising delivery agents in cancer therapies.
Keywords: drug delivery; target; nanoparticle; glucose transporter (Glut); chitosan (CS)

Release behavior and kinetic evaluation of berberine hydrochloride from ethyl cellulose/chitosan microspheres by Hui-Yun Zhou; Pei-Pei Cao; Jie Zhao; Zhi-Ying Wang; Jun-Bo Li; Fa-Liang Zhang (373-382).
Novel ethyl cellulose/chitosan microspheres (ECCMs) were prepared by the method of w/o/w emulsion and solvent evaporation. The microspheres were spherical, adhesive, and aggregated loosely with a size not bigger than 5 μm. The drug loading efficiency of berberine hydrochloride (BH) loaded in microspheres were affected by chitosan (CS) concentration, EC concentration and the volume ratio of V(CS)/V(EC). ECCMs prepared had sustained release efficiency on BH which was changed with different preparation parameters. In addition, the pH value of release media had obvious effect on the release character of ECCMs. The release rate of BH from sample B was only a little more than 30% in diluted hydrochloric acid (dHCl) and that was almost 90% in PBS during 24 h. Furthermore, the drug release data were fitted to different kinetic models to analyze the release kinetics and the mechanism from the microspheres. The released results of BH indicated that ECCMs exhibited non-Fickian diffusion mechanism in dHCl and diffusion-controlled drug release based on Fickian diffusion in PBS. So the ECCMs might be an ideal sustained release system especially in dHCl and the drug release was governed by both diffusion of the drug and dissolution of the polymeric network.
Keywords: ethyl cellulose (EC); chitosan (CS); microsphere; release in vitro ; release kinetics

A series of model polymerization are carried out via the one-pot externally initiated Kumada catalyst-transfer polycondensation (KCTP) of 2-bromo-5-chloromagnesium thiophene monomers, and the excess amount of initiators or catalysts are found no need to be isolated during the polycondensation process. Especially, the impacts of the nickel catalyst loading variation on regioregularity (rr), yield, molecular weight (M n), polydispersity (PDI) and initiation efficiency of poly(3-hexylthiophene) (P3HT) are systematically investigated. The 1H NMR, size-exclusion chromatography (SEC), and MALDI-TOF mass spectroscopy results indicated that an excess amount of catalyst does not influence yield, rr, M n, and PDI of P3HT, nor the initiation efficiency. However, the PDI of the product is broad, and the M n and rr values decreased in the absence of 1,3-bis (diphenylphosphino)propane (dppp). It can be concluded that the in-situ KCTP polymerization of P3HT is a practical and effective process. These results are especially valuable for the synthesis of all-conjugated block copolymers where macroinitiators are used.
Keywords: Kumada catalyst-transfer polycondensation (KCTP); poly(3-hexylthiophene) (P3HT); regioregularity (rr)

Improvement in electrochemical capacitance of activated carbon from scrap tires by nitric acid treatment by Yan Han; Ping-Ping Zhao; Xiao-Ting Dong; Cui Zhang; Shuang-Xi Liu (391-398).
Activated carbon (AC) obtained from the industrial pyrolytic tire char is treated by concentrated nitric acid (AC-HNO3) and then used as the electrode material for supercapacitors. Surface properties and electrochemical capacitances of AC and ACHNO3 are studied. It is found that the morphology and the porous texture for AC and AC-HNO3 have little difference, while the oxygen content increases and functional groups change after the acid treatment. Electrochemical results demonstrate that the AC-HNO3 electrode displays higher specific capacitance, better stability and cycling performance, and lower equivalent series resistance, indicating that AC obtained from the industrial pyrolytic tire char treated by concentrated nitric acid is applicable for supercapacitors.
Keywords: pyrolytic tire char; activated carbon (AC); nitric acid treatment; electrochemical capacitance; supercapacitor

A new method for concentration analysis of bacterial endotoxins in perfluorocarbon by Dan-Dan Chen; Xiao-Ming Feng; Chun-Ren Wang; Qing-Quan Huang; Zhao-Peng Yang; Qing-Yuan Meng (399-402).
This communication demonstrates the feasibility of the gel-clot method for the analysis of bacterial endotoxins in water extracts of perfluorocarbon which is a water insoluble liquid medical device. Perfluorocarbon (10 mL) was shaken with 10mL water for 15 min at 2000 r/min and the endotoxin present was extracted to the aqueous phase without interference inhibition/enhancement of the product and the recovery of endotoxin added to perfluorocarbon was determined. A validation study confirmed that endotoxins presented in perfluorocarbon pass over into the aqueous phase at concentrations of 20, 10 and 5 EU/mL with recoveries from 86.8% to 96.8%. Therefore, the gel-clot test is suitable for detecting bacterial endotoxins in perfluorocarbon which is a water insoluble medical device.
Keywords: perfluorocarbon; bacterial endotoxin; endotoxin recovery

Choosing animal-derived regenerative implantable medical devices based on tissue engineering technology as a research theme, this paper presents bibliometric analysis of relative literature from the mainland of China to understand such data as publication year and journal preference, authors’ geographic location, research topics and core expertise to predict the research trends and provide an informed basis of decision making for researchers and clinicians.
Keywords: animal-derived medical device; tissue engineering; regenerative implantable medical device; literature mainland China; bibliometric analysis