Effect of adding selected carboxylic acids to the solution on electrophoretic deposition, adhesion strength, morphology and antibacterial properties of chitosan coatings on titanium

In the presented work, the possibility of developing chitosan (CS) coatings on Ti substrates by electrophoretic deposition (EPD) from different acidic solutions was studied. The effect of various acids from the carboxylic acid group used in the EPD solutions on the structure and properties of chitosan coatings was investigated. Two acids were chosen that had already been used to prepare EPD chitosan solutions: acetic acid (HOAc) and citric acid (CiA). In addition, malic acid (MaA) was investigated as a novel potential biodegradable natural ingredient. Homogeneous coatings with high adhesion strength were obtained, regardless of the acid used. The coatings showed a roughness higher than that of the uncoated Ti substrate. It was found that acids from the alpha-hydroxy acids group (AHAs, CiA and MaA) not only protonate the amino groups of chitosan but also change its structure, through the proposed cross-linking mechanism. This was reflected in the surface wettability of the coatings. For coatings obtained from the solution with HOAc, the contact angle was about 80 and for those developed from solutions with MaA and CiA, it was about 50 degrees. Microbiological studies revealed that the coatings deposited from solutions containing HOAc and CiA had the highest bactericidal activity.