Composite
coating of antibiotic gentamicin (Gent), natural polymer
chitosan (CS), and hydroxyapatite (HAP) was successfully assessed
by applying the electrophoretic deposition (EPD) technique. EPD was
performed under optimized deposition conditions (5 V, 12 min) on pure
titanium plates, to obtain HAP/CS and HAP/CS/Gent composite coatings
in a single step from three-component aqueous suspension, with favorable
antibacterial properties. Composite coatings were characterized by
X-ray diffraction (XRD), field emission scanning electron microscopy,
Fourier transform infrared spectroscopy, thermogravimetric analysis,
and X-ray photoelectron analysis, confirming the formation of composite
HAP/CS and HAP/CS/Gent coatings on the titanium surface, which is
due to intermolecular hydrogen bonds. Employing the XRD technique,
HAP was detected by obtaining the characteristic diffraction maximums.
Good antibacterial activity of the composite coating loaded with antibiotic
(HAP/CS/Gent) was confirmed against Staphylococcus
aureus and Escherichia coli, pointing to the high potential for bioapplication. Introduction
of gentamicin in HAP/CS/Gent coating caused very mild cytotoxicity
in the tested cell lines MRC-5 and L929. MTT testing was used to evaluate
cell viability, and HAP/CS was classified as noncytotoxic.
Hydroxyapatite is the most suitable biocompatible material for bone implant coatings. However, its brittleness is a major obstacle, and that is why, recently, research focused on creating composites with various biopolymers. In this study, hydroxyapatite coatings were modified with lignin in order to attain corrosion stability and surface porosity that enables osteogenesis. Incorporating silver, well known for its antimicrobial properties, seemed the best strategy for avoiding possible infections. The silver/hydroxyapatite (Ag/HAP) and silver/hydroxyapatite/lignin (Ag/HAP/Lig) coatings were cathaphoretically deposited on titanium from ethanol suspensions, sintered at 900 °C in Ar, and characterized by X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy, attenuated total reflection Fourier transform infrared, and X-ray photoelectron spectroscopy. The corrosion stability of electrodeposited coatings was evaluated in vitro in Kokubo's simulated body fluid (SBF) at 37 °C using electrochemical impedance spectroscopy. Bioactivity was estimated by immersion in SBF to evaluate the formation of hydroxyapatite on the coating surface. A microcrystalline structure of newly formed plate-shaped carbonate-hydroxyapatite was detected after only 7 days, indicating enhanced bioactive behavior. Both coatings had good corrosion stability during a prolonged immersion time. Among the two, the Ag/HAP/Lig coating had a homogeneous surface, less roughness, and low values of contact angle.
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