Electrophoretic deposition of tetracycline hydrochloride loaded halloysite nanotubes chitosan/bioactive glass composite coatings for orthopedic implants

Abstract

Electrophoretic deposition (EPD) was used to apply bioactive multifunctional composite coatings with antibacterial substances on stainless steel AISI 316L (SS). Tetracycline hydrochloride (TCN) loaded halloysite nanotubes were co-deposited with chitosan and bioactive glass (BG) particles to produce composite coatings. SEM/EDX, XRD, and FTIR analyses were performed to characterize the composition and microstructure of coatings. The release of tetracycline hydrochloride (TCN) in phosphate buffered saline (PBS) was investigated by UV spectrometry, and measurements indicated the release of around 54% of the drug within 14days of immersion in PBS. Furthermore, to determine that the bioactivity of coatings had not been adversely influenced, simulated body fluid (SBF) bioactivity tests were performed. The formation of hydroxyl carbonate apatite on the surface of the coatings was confirmed after 3days. The ability of coatings to prevent bacterial growth was tested using E. coli as gram-negative and S. aureus as gram-positive bacteria. Results showed improved bactericidal effect of TCN-containing coatings compared to non-TCN loaded coatings. The corresponding amount of TCN loaded in EPD coatings supported cell viability and proliferation of MG-63 cells for up to 3days. Fluorescence images of MG-63 cells showed evidence of cell growth in islands on the coated surface. The surface roughness of the coating loaded with halloysite nanotubes supported cell adhesion and proliferation. Additionally, the wettability value of the coatings confirmed a moderately hydrophilic surface, which is suitable for bone regenerative applications. Improved corrosion resistance compared to the pure stainless steel (SS) substrate was confirmed. The adhesion between coatings and substrates was tested by the tape test, and the result showed sufficient adhesion of the coatings to be handled without detachment. In all, the new coating system has potential for applications in orthopedics.