In vitro corrosion resistance, antibacterial activity and cytocompatibility of a layer-by-layer assembled DNA coating on magnesium alloy

A chitosan/deoxyribonucleic acid (CHI/DNA)5 coating was constructed by layer-by-layer (LbL) assembly dip coating method with Mg(OH)2 coating as an inner protective layer on AZ31 alloy. X-ray diffractometry, X-ray photoelectron spectrometry, Fourier transform infrared spectroscopy and field-emission scanning electron microscopy were utilized to represent the chemical compositions and surface morphologies of the coatings. Electrochemical tests and hydrogen evolution measurements were implemented to confirm the good corrosion resistance of the composite coating in artificial body fluid. Antimicrobial activity of the composite coatings was tested via the plate-counting method, and the cytotoxicity of the samples was appraised by MTT assay and Live/dead staining. A double action was put into effect for the composite coating, which the inner Mg(OH)2 coating plays the part of physical barrier, and the outer (CHI/DNA)5 coating is employed as an inducer to fabricate a biocompatible Ca-P corrosion product coating during immersion, making up for its thin thickness. Otherwise, the composite coating is also beneficial for the growth of bone, resulting from the biomineralization effect of the outer polyelectrolyte multilayer. The good antibacterial property of the (CHI/DNA)5/Mg(OH)2 coating is ascribed to the contact-killing strength of CHI. Thus, the obtained (CHI/DNA)5/Mg(OH)2 coating has a wide application prospect in the field of Mg-based bone implantation.