Enhancement of the biological properties of 316L stainless steel using chitosan-based biocomposite coatings via the sol–gel dip-coating technique

The primary objective of this study is to enhance the biological performance of 316L stainless steel by applying biocomposite coatings derived from natural polymers. A chitosan/collagen blend was selected as the polymeric matrix due to its biocompatibility, biodegradability, and favorable bioactive properties. The coatings were fabricated using a sol–gel dip-coating technique, which enables controlled deposition, uniform thickness, and strong adhesion to the metallic substrate. To further improve functional performance, the matrix was reinforced with ceramic particles, namely titanium dioxide (TiO₂) and phosphorus pentoxide (P₂O₅), chosen for their bioactivity and antimicrobial potential. Structural characterization using X-ray diffraction (XRD) confirmed the crystalline phases of the incorporated ceramic reinforcements, verifying their successful integration into the polymer matrix. Field Emission Scanning Electron Microscopy (FESEM) analysis revealed smooth, homogeneous, and defect-minimized surfaces with a uniform dispersion of TiO₂ and P₂O₅ particles throughout the coating. Such morphology is essential for ensuring mechanical stability and long-term durability under physiological conditions. Surface energy and wettability measurements demonstrated that TiO₂-containing coatings exhibited lower contact angle values, indicating superior hydrophilicity compared to P₂O₅-reinforced layers. Enhanced wettability is associated with improved protein adsorption and cell attachment, which are critical factors for implant integration. Antibacterial assays further showed that TiO₂-modified surfaces exerted stronger inhibitory effects against both Escherichia coli and Staphylococcus aureus, suggesting effective resistance to bacterial colonization. These findings highlight that chitosan-based biocomposite coatings offer a promising and sustainable approach to improving the bioactivity, corrosion resistance, and antibacterial performance of stainless steel surgical implants.