The in vitro biological properties of Mg-Zn-Sr alloy and superiority for preparation of biodegradable intestinal anastomosis rings.

BACKGROUND: Magnesium (Mg) alloy is a metal-based biodegradable material that has received increasing attention in the field of clinical surgery, but it is currently seldom used in intestinal anastomosis. This study was conducted to comprehensively assess a ternary magnesium (Mg)-zinc (Zn)-strontium (Sr) alloy's biological superiorities as a preparation material for intestinal anastomosis ring. MATERIAL AND METHODS: Mouse L-929 fibroblasts were cultured with Mg-Zn-Sr alloy extract and compared with both positive (0.64% phenol) and negative (original broth culture) controls. The cell morphology of different groups was examined using microscopy, and a cytotoxicity assessment was performed. Fresh anticoagulated human blood was mixed with Mg-Zn-Sr alloy extract and compared with both positive (distilled water) and negative (normal saline) controls. The absorbance of each sample at 570 nm was used to calculate the Mg-Zn-Sr alloy hemolysis ratio in order to test the Mg alloy's blood compatibility. Bacterial cultures of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were added to Mg-Zn-Sr alloy block samples and compared with positive (Ceftazidime), negative (316LSS stainless steel), and blank controls. The broth cultures were sampled to compare their bacterial colony counts so as to evaluate the antibacterial properties of the Mg-Zn-Sr alloy. The Mg-Zn-Sr alloy was surface-coated with a layer of poly(lactic-co-glycolic acid) carrying everolimus. The surface morphology and degradability of the coating were examined so as to demonstrate feasibility of coating, which can release the drug evenly. RESULTS: The experiments proved that Mg-Zn-Sr alloy has good biocompatible, antibacterial, and drug-loaded coating performances, which are lacking in existing intestinal anastomosis devices/materials. CONCLUSIONS: The Mg-Zn-Sr alloy increases biocompatibility, and yields a safer and better therapeutic effect; therefore, it is a novel biomaterial that is feasible for use when preparing biodegradable intestinal anastomosis rings.

The design, development, and in vivo performance of intestinal anastomosis ring fabricated by magnesium­zinc­strontium alloy.

In the current work, an intestinal anastomosis ring made of magnesium­zinc­strontium (Mg-Zn-Sr) alloy was developed and fabricated in order to take advantages of the appropriate biocompatibility and degradability of Mg-based alloys. As-fabricated anastomosis rings were implanted into the intestinal tracts of Bama miniature pigs to evaluate their biological performance in vivo. At the injury site, the formation of edema and granulation tissue was observed for 2 weeks after surgery. Till week 4, the edema transformed to firm scar tissue, which reached the healing standard of intestinal tissue. The levels of biochemical indicators such as blood routine, liver and kidney functions as well as electrolytes were all under normal conditions, indicating that the implantation of Mg alloy did not have remarkable influence on the blood system as well as liver and kidney functions. Pathological results revealed that no obvious abnormality was found in heart, liver, spleen, lung, kidney and brain tissues. The Mg ions were found to be excreted from the body through urine. The intestinal anastomosis ring could be discharged through excretion around 2 weeks after surgery, of which the surface was corroded and covered by a layer of Ca- and P-containing minerals. According to histological images, a mild inflammatory response was noticed on week 2. At this stage, dilated and congested capillaries were found in the muscular layer. Moreover, the mucosal layer and villi at the injury site were disordered. Till week 4, the muscular and mucosal layer were similar to their healthy counterparts even though the villi were slightly shorter than normal ones. Together, the results indicate that Mg-Zn-Sr alloy is a promising candidate for the fabrication of biodegradable intestinal anastomosis ring.