Enzymatically-degradable hydrogel coatings on titanium for bacterial infection inhibition and enhanced soft tissue compatibility via a self-adaptive strategy

Ideal percutaneous titanium implants request both antibacterial ability and soft tissue compatibility.ZnO structure constructed on titanium has been widely proved to be helpful to combat pathogen contamination,but the biosafety of ZnO is always questioned.How to maintain the remarkable antibacterial ability of ZnO and efficiently reduce the corresponding toxicity is still challenging.Herein,a hybrid hydrogel coating was constructed on the fabricated ZnO structure of titanium,and the coating was proved to be enzymatically-degradable when bacteria exist.Then the antibacterial activity of ZnO was presented.When under the normal condition(no bacteria),the hydrogel coating was stable and tightly adhered to titanium.The toxicity of ZnO was reduced,and the viability of fibroblasts was largely improved.More importantly,the hydrogel coating provided a good buffer zone for cell ingrowth and soft tissue integration.The curbed Zn ion release was also proved to be useful to regulate fibroblast responses such as the expression of CTGF and COL-I.These results were also validated by in vivo studies.Therefore,this study proposed a valid self-adaptive strategy for ZnO improvement.Under different conditions,the sample could present different functions,and both the antibacterial ability and soft tissue compatibility were finely preserved.

Biocompatibility and characteristics of chitosan/cellulose acetate microspheres for drug delivery

In this work, chitosan/cellulose acetate microspheres （CCAM） were prepared by the method of WlO/W emulsion with no toxic reagents. The microspheres were spherical, free flowing, and non-aggregated, which had a narrow size distribution. More than 90% of the microspheres had the diameter ranging from 200 to 280 pm. The hemolytic analysis indicated that CCAM was safe and had no hemolytic effect. The implanted CCAM did not produce any significant changes in the hematology of Sprague- Dawley （SD） rats, such as white blood cell, red blood cell, platelet, and the volume of hemoglobin. In addition, the levels of serum alanine aminotransferase, blood urea nitrogen, and creatinine had no obvious changes in SD rats implanted with CCAM, surger thread, or normal SD rats without any implantation. Thus, the CCAM had good blood compatibility and had no hepatotoxicity or renal toxicity to SD rats. Furthermore, CCAM with or without the model drug had good tissue compatibility with respect to the inflammatory reaction in SD rats and showed no significant difference from that of SD rats implanted with surgery thread. CCAM shows promise as a long-acting delivery system, which had good biocompatibility and biodegradability.

Preparation of enzymatically cross-linked sulfated chitosan hydrogel and its potential application in thick tissue engineering

For the requirement of preliminary vascularization, the scaffolds for thick tissue engineering should have not only good cell affinity, but also anticoagulant ability. In this paper, enzymatically cross-linked hydrogel scaffolds based on sulfated chitosan （SCTS） were prepared. Firstly, sulfated chitosan-hydroxyphenylpionic acid （SCTS-HPA） conjugate was synthesized, and the structure of SCTS-HPA was identified by FITR and ~H NMR. And then the enzymatically cross-linked hydrogels were pre- pared in presence of horseradish peroxidase （HRP） and hydrogen peroxide （H202）. The gelation time, mechanical property, morphology and cytotoxicity to human umbilical vein endothelial cells （HUVECs） of the hydrogel were evaluated in vitro, the tissue compatibility of SCTS-HPA scaffold was studied in vivo. The results showed that the gelation time, mechanical property, morphology of the dehydrated hydrogel could be controlled by the the concentration of HRP and H202. The cytotoxicity test showed that the hydrogel extracts have no cytotoxicity to HUVECs. The in vivo assay indicated that SCTS-HPA scaffold have good tissue compatibility with no thrombus formation. All these results indicated that the SCTS-HPA scaffold could be used as a thick tissue engineering scaffold.

In vivo biological stability of chemically pretreated silicone gel inserts intended for use in keratoprostheses

Background Pretreatment with chemical agents could alter the surface chemistry of the silicone gel, which makes it suitable for epithelial migration onto its surface and thus enhances the cytobiocompatibility. This study aimed to evaluate the biological response of the corneal stroma to porous silicone gel pretreated with different chemical agents in vivo. Methods The porous silicone gels were treated with a mixed acid solution containing 23.2% H2SO4 and 0.8% K2Cr207 for 10 or 15 minutes or with 30% H202 for 15 minutes. Discs （4 mm in diameter） were inserted into interlamellar stromal pockets of New Zealand white rabbits and followed up for a period of 3 months. Clinical evaluations such as corneal infiltration, edema and neovascularization were performed daily. At 3 months, the fibroplasias and collagen deposition were examined under light and scanning electron microscopy （SEM） and by immunohistochemical analysis. Results Pretreatment of the discs obviously decreased conjunctival congestion, discharge, cornea edema, and the extent of neovascularization. More fibroblasts migrated into the pretreated discs than into the control, and collagen was deposited, indicating that the biocompatibility of the corneal replacements was enhanced by the chemical pretreatments. From immunohistochemical analysis, Type I collagen deposition in the pretreated silicone discs was greater than in the control. Conclusions Chemical treatment of silicone gel is effective in decreasing rabbit corneal inflammation, encouraging fibroblast in-growth, and enhancing tissue compatibility. Pretreated gels show good biological stability when used as a skirt material in Keratoprosthesis （Kpros）.