Magnesium (Mg) has good biocompatibility, making it suitable as an implant material. However, Mg has a high corrosion rate because of the reaction between magnesium implants and fluids in the human body. To lower the corrosion rate of magnesium alloys, it is necessary to perform a coating process using tannic acid (TA) and hyaluronic acid (HYA), as we have done in this study. TA, an active ingredient, is relatively inexpensive, easy to find, and can effectively reduce the degradation rate. SEM characterization showed that the TA–HYA layer was formed by chelation between the Mg and TA surfaces. Furthermore, adding HYA to the coating covered the cracks caused by the TA layer and increased the hydrophilic properties. In vitro corrosion tests using Tafel polarization showed that the TA–HYA coating reduced the corrosion rate of the magnesium alloy from 7.379 mm/year to 0.204 mm/year. The immersion test in the SBF solution showed that the TA–HYA layer could bind Mg²⁺, which is beneficial for new bone growth.

The high corrosion rate of magnesium limits its application as a bioresorbable implant, despite its good biocompatibility. A tannic acid (TA) coating on magnesium has succeeded in increasing the corrosion resistance of magnesium, although the presence of cracks in this coating still limits its effectiveness. This research focuses on the effect of adding polyethyleneimine (PEI) to the TA coating to increase the corrosion resistance of magnesium and its biocompatibility. The TA–PEI coating on magnesium with TA : PEI weight ratios of 1 : 0, 1 : 0.5, 1 : 1, and 1 : 2, which was achieved by the immersion method, was evaluated by characterizing the composition, morphology, structure, and surface roughness of the coating as well as the deformation mechanism. The corrosion properties and corrosion rate were examined through immersion and electrochemical corrosion tests (potentiodynamic polarization and EIS). Wettability, cell adhesion, and MTT assay tests were carried out as a coating biocompatibility test. The magnesium's surface was successfully covered with the TA–PEI coating, increasing its corrosion resistance and biocompatibility. The increase in the PEI content in the weight ratio of TA : PEI from 1 : 0 to 1 : 2 resulted in a reduction in the areal crack density from 25.49% to 7.12%, an increase in the coating thickness from 5.7 μm to 9.3 μm, a decrease in the surface roughness from 5.20 μm to 0.98 μm, but a change in the deformation mechanism from ductile to brittle. Adding PEI to TA as a pure magnesium coating has increased the material's corrosion resistance. The changed weight ratio of TA : PEI from 1 : 0 to 1 : 2 is the most optimum ratio because it can reduce the corrosion rate of the material from 3.7 mm year⁻¹ to 0.47 mm year⁻¹. The formation of hydroxyapatite on a corroded material indicates that this system is biocompatible. Increasing the PEI content from 1 : 0 to 1 : 2 TA : PEI weight ratio decreased the contact angle from 74° to 24°. At a 1 : 2 TA : PEI ratio, passage 6 HWJ cells can adhere well, and this system has the highest absorbance from the MTT assay result. Both indicate that this coating system has good biocompatibility with human physiochemical systems.

Bone cement is one of the materials used in orthopaedics that serves various functions, such as binding bone implants, replacing damaged bones and filling spaces within bones. Various materials have been used to synthesize bone cement, and one promising material for further research is fish bone waste-based bone cement. This study investigates the potential of fish bone waste-based bone cement by incorporating nano fish bone (NFB) and L -arginine ( L -Arg) protein into polymethyl methacrylate (PMMA) to examine apatite growth. NFB derived from the Salmo salar fish positively influences osteoblast cell proliferation and differentiation, while L-Arg enhances biocompatibility and antibiotic properties. The NFB/L-Arg combination holds promise in accelerating new bone formation and cell growth, both of which are crucial for fracture healing and bone remodelling. Tensile strength tests reveal the superior performance of BC-PMMA-1-NFB/L-Arg (36.11 MPa) compared with commercial PMMA (32 MPa). Immersion tests with simulated body fluid (SBF) solution for 7 days reveal accelerated apatite layer formation, emphasizing the potential benefits of NFB/ L -Arg in bone cement applications.