Magnesium alloys are biodegradable metals receiving increasing attention, but the clinical applications of these materials are delayed by concerns over the rapid corrosion rate and gas formation. Unlike corrosion, which weakens mechanical properties, the gas formation issue has received little attention. Therefore, we evaluated the gas formation and biological effects for Mg implants through preclinical (immersed in Earle’s balanced salt solution and in vivo) and clinical studies. The immersion test examined the gas volume and composition. The in vivo study also examined gas volume and histological analysis. The clinical study examined the gas volume and safety after Mg screw metatarsal fixation. Gas was mainly composed of H₂, CO and CO₂. Maximum volumes of gas formed after 5 days for in vivo and 7 days in clinical study. Within the clinical examination, two superficial wound complications healed with local wound care. Osteolytic lesions in the surrounding metaphysis of the Mg screw insertion developed in all cases and union occurred at 3 months. Mg implants released gas with variable volumes and composition (H₂, CO, and CO₂), with no long-term toxic effects on the surrounding tissue. The implants enabled bone healing, although complications of wound breakdown and osteolytic lesions developed.

Gelatin methacryloyl (GelMA) has been widely studied as a biomaterial for tissue engineering. Most studies focus on mammalian gelatin, but certain factors, such as mammalian diseases and diet restrictions, limit the use of mammalian gelatin. Thus, fish gelatin has received much attention as a substitute material in recent years. To develop a broadly applicable hydrogel with excellent properties, an interpenetrating polymer network (IPN) hydrogel was synthesized, since IPN hydrogels consist of at least two different hydrogel components to combine their advantages. In this study, we prepared GelMA using type A and fish gelatin and then synthesized IPN hydrogels using GelMA with alginate. GelMA single-network hydrogels were used as a control group. The favorable mechanical properties of type A and fish hydrogels improved after the synthesis of the IPN hydrogels. Type A and fish IPN hydrogels showed different mechanical properties (mechanical strength, swelling ratio, and degradation rate) and different cross-sectional morphologies, since the degree of mechanical enhancement in fish IPN hydrogels was less than that in type A; however, the cell biocompatibilities were not significantly different. Therefore, these findings could serve as a reference for future studies when selecting GelMA as a biological material for tissue engineering.

TiO₂ nanotubes (TNT) formation is beneficial for improving bone cell–material interaction and drug delivery for Ti dental implants. Among the natural drugs to be installed in TNT, selected propolis has antibacterial and anti-inflammatory properties. It is a resinous natural product which is collected by the honeybees from the various types of plants with their salivary enzymes. This study concludes that TNT loaded with a propolis (PL-TNT-Ti) dental implant has the ability to improve osseointegration. The propolis particles were embedded within the TNT or adhered to the top. In a cytotoxicity test using osteoblast, PL-TNT-Ti group exhibited an increased cell proliferation and differentiation. A Sprague Dawley rat mandibular model was used to evaluate the osseointegration and bone bonding of TNT or PL-TNT-Ti. From the µ-CT and hematoxylin and eosin (HE) histological results after implantation at 1 and 4 weeks to rat mandibular, an increase in the extent of new bone formation and mineral density around the PL-TNT-Ti implant was confirmed. The Masson’s trichrome staining showed the expression of well-formed collagenous for bone formation on the PL-TNT-Ti. Immunohistochemistry staining indicate that bone morphogenetic proteins (BMP-2 and BMP-7) around the PL-TNT-Ti increased the expression of collagen fibers and of osteogenic differentiation whereas the expression of inflammatory cytokine such as interleukin-1 beta (IL-1ß) and tumor necrosis factor-alpha (TNF-α) is decreased.