Electrophoretic deposition of chitosan/45S5 Bioglass ® composite coatings for orthopaedic applications

Abstract

This article presents experimental results on the electrophoretic deposition (EPD) of bioresorbable chitosan/45S5 Bioglass ® composite coatings for orthopaedic implants based on the Taguchi design of experiments (DOE) approach. The influence of EPD parameters including Bioglass ® concentration, electric voltage and deposition time on deposition yield was studied by an orthogonal Taguchi array of L 18 type. Multivariate analysis of variance (MANOVA) and regression analysis based on the partial least-square method were used to identify the significant factors affecting the deposition yield and its stability during constant-voltage EPD. The coatings were characterised by high resolution scanning electron microscope (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). It is shown that the co-deposition of polymer/Bioglass ® system is very sensitive to the concentration of Bioglass ® particles. The addition of Bioglass ® to the chitosan suspension alters the deposition rate due to variation of pH, suspension conductivity, and zeta potential. For low Bioglass ® concentrations, co-deposition of the chitosan and the bioactive glass particles occurs while at the higher concentrations massive deposition of the bioactive glass particles controls the deposition yield. The optimum condition for a high deposition rate with low standard deviation and homogeneous microstructure is achieved when an almost equal concentrations of chitosan and Bioglass ® is utilized. The validity of the approach is shown by confirmation experiments at the predicted optimal condition, and the mechanism of electrophoretic co-deposition of the polymer/glass system is discussed.