In vivo and in vitro performances of chitosan-coated Mg-Zn-Zr-Gd-Ca alloys as bone biodegradable materials in rat models.

Mg alloys have attracted significant attention as promising biomedical materials, specifically as fixation materials for promoting fracture healing. However, their unsatisfactory corrosion resistances hinder further clinical applications and thus require attention. This study aims to determine the performance of novel chitosan-coated Mg-1Zn-0.3Zr-2Gd-1Ca alloy and its ability to promote the healing of osteoporotic fractures. Moreover, its corrosion resistance and biocompatibility were assessed. Performance degradations of the samples were measured via electrochemical tests, weight loss test and morphological analysis, and the uncoated and chitosan-coated fixations were compared based on their effects on biocompatibility via the cytotoxicity test, X-rays, and hematoxylin and eosin staining. The effect of bone growth and healing was investigated via immunohistochemical test. Results of the electrochemical tests indicated that compared with the bare body, chitosan-coated Mg-Zn-Ca-Zr-Gd alloys improved by one order of magnitude. Additionally, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and weight loss test demonstrated that the corrosion resistance of the chitosan-coated Mg alloy is better than that of the uncoated alloy. In addition, cytotoxicity analysis indicated that the viability and morphology of the chitosan-coated alloy groups were superior to the uncoated groups in vitro. During in vivo analysis, chitosan-coated and uncoated Mg-1Zn-0.3Zr-2Gd-1Ca alloys were implanted into ovariectomized SD female rats with osteoporotic fractures for 1, 2, and 3 weeks. No displacement and shedding were observed through X-rays, and pathological analyses proved that the material was not harmful for liver and kidney tissues. Immunohistochemistry revealed that the chitosan-coated Mg-Zn-Ca-Zr-Gd alloy material contributed to the healing of osteoporotic fractures in the SD rat models. In conclusion, this study demonstrated the chitosan-coated Mg-Zn-Ca-Zr-Gd alloys have improved corrosion resistance and biocompatibility. Moreover, the alloy was found to accelerate the healing of osteoporotic fractures in SD rat models. Therefore, it has significant potential as a fixation material for osteoporotic fractures.

Corrosion and biocompatibility behaviours of microarc oxidation/phytic acid coated magnesium alloy clips for use in cholecystectomy in a rabbit model.

With the popularisation of laparoscopic cholecystectomy, ligation clips have been commonly used for ligating the cystic duct and cystic artery. However, non-degradable clips remain in the body long-term, which significantly increases the risk of the clip becoming detached. Thus, magnesium alloys have attracted tremendous attention owing to their biodegradability and good biocompatibility. However, the poor corrosion resistance hinders the clinical application of magnesium alloys with microarc oxidation/phytic acid (MAO/PA) composite coatings as protective coatings. Here, these alloys were used to hinder the rapid material degradation in aqueous solution. Electrochemical tests were conducted to evaluate the in vivo degradation behaviour in simulated body fluid (SBF) for Mg-Zn-Y-Nd alloys, and scanning electron microscopy (SEM) was used to observe the micromorphology of in vivo clip degradation. Cell toxicity, cell adhesion, and flow cytometry were performed in vitro to detect cytocompatibility. Biochemical detection of serum magnesium, serum creatinine (CREA), blood urea nitrogen (BUN), alanine transaminase (ALT), and alanine aminotransferase (AST), and haematoxylin-eosin (HE) staining of the heart, liver, and kidney tissues in vivo was conducted to determine the biocompatibility properties after surgery. Electrochemical measurements and SEM images revealed that the MAO/PA-coated magnesium alloy delayed corrosion in SBF. The apoptosis rate increased slightly with increased extract concentration. Nevertheless, MAO/PA-coated magnesium alloys still exhibited good cytocompatibility. No obvious abnormality was observed in the blood biochemical test or HE staining. Thus, MAO/PA-coated magnesium alloys exhibit better corrosion than bare magnesium. In addition, Mg-Zn-Y-Nd and MAO/PA-coated magnesium alloys exhibited no cytotoxicity, good adhesion, and biosafety.

Biological behavior exploration of a paclitaxel-eluting poly-l-lactide-coated Mg-Zn-Y-Nd alloy intestinal stent in vivo.

As a new type of intestinal stent, the MAO/PLLA/paclitaxel/Mg-Zn-Y-Nd alloy stent has shown good degradability, although its biocompatibility in vitro and in vivo has not been investigated in detail. In this study, its in vivo biocompatibility was evaluated by animal study. New Zealand white rabbits were implanted with degradable intestinal Mg-Zn-Y-Nd alloy stents that were exposed to different treatments. Stent degradation behavior was observed both macroscopically and using a scanning electron microscope (SEM). Energy dispersion spectrum (EDS) and histological observations were performed to investigate stent biological safety. Macroscopic analysis showed that the MAO/PLLA/paclitaxel/Mg-Zn-Y-Nd stents could not be located 12 days after implantation. SEM observations showed that corrosion degree of the MAO/PLLA/paclitaxel/Mg-Zn-Y-Nd stents implanted in rabbits was significantly lower than that in the PLLA/Mg-Zn-Y-Nd stent group. Both histopathological testing and serological analysis of in vivo biocompatibility demonstrated that the MAO/PLLA/paclitaxel/Mg-Zn-Y-Nd alloy stents could significantly inhibit intestinal tissue proliferation compared to the PLLA/Mg-Zn-Y-Nd alloy stents, thus providing the basis for designing excellent biodegradable drug stents.

Correction: Biological behavior exploration of a paclitaxel-eluting poly-l-lactide-coated Mg-Zn-Y-Nd alloy intestinal stent in vivo.

[This corrects the article DOI: 10.1039/C9RA10156J.].