Electrophoretic Deposition of Cu-Doped SiO2/Chitosan Composite Coatings on AISI 316L Stainless Steel: Correlation Between Adhesion, Microstructure, and In Vitro Bioactivity

Abstract

In this study, SiO₂ particles were deposited on AISI 316L stainless steel by electrophoretic deposition using chitosan as a matrix. Different SiO₂:Cu-to-chitosan compositions were investigated to determine the coating formulation providing the most favorable combination of adhesion, microstructural characteristics, and biological performance. Electrophoretic deposition was carried out at an applied voltage of 15 V and a current of 60 mA, respectively. The results of the ASTM D3359 adhesion test showed that the coating adhesion grade of the selected sample was 3B. In the XRD pattern, a broad peak in the range of 22-25° was attributed to the amorphous phase of SiO₂. Two distinct peaks were observed at approximately 36° and 39°, indicating the presence of copper oxide phases. The FE-SEM images showed that the average particle size was approximately 1.4 μm for the samples containing different amounts of silica. The coating thickness ranged from 11.5 to 12.5 μm for the samples possessing R = 2/3 and from 19 to 20 μm for the samples with R = 1. In vitro biological evaluation, including MTT cytocompatibility assessment and simulated body fluid (SBF) immersion testing, demonstrated favorable cellular viability and bioactive behavior of the coatings. Based on the experimental results, the coating with R = 3/3 exhibited the most balanced combination of coating thickness, biological response, and adhesion performance and was therefore identified as the optimal composition among the investigated formulations.