Electrophoretic Deposition and Characteristics of Chitosan–Nanosilver Composite Coatings on a Nanotubular TiO2 Layer

Abstract

The surface treatment of titanium implants has been applied mainly to increase surface bioactivity and, more recently, to introduce antibacterial properties. To this end, composite coatings have been investigated, particularly those based on hydroxyapatite. The present research was aimed at the development of another coating type, chitosan–nanosilver, deposited on a Ti13Zr13Nb alloy. The research comprised characterization of the coating’s microstructure and morphology, time-dependent nanosilver dissolution in simulated body fluid, and investigation of the nanomechanical properties of surface coatings composed of chitosan and nanosilver, with or without a surface-active substance, deposited at different voltages for 1 min on a nanotubular TiO2 layer. The microstructure, morphology, topography, and phase composition were examined, and the silver dissolution rate in simulated body fluid, nanoscale mechanical properties, and water contact angle were measured. The voltage value significantly influenced surface roughness. All specimens possessed high biocompatibility. The highest and best adhesion of the coatings was observed in the absence of a surface-active substance. Silver dissolution caused the appearance of silver ions in solution at levels effective against bacteria and below the upper safe limit value.

Electrophoretically Deposited Chitosan/Eudragit E 100/AgNPs Composite Coatings on Titanium Substrate as a Silver Release System

“…Despite that, small nanometric AgNPs groups were also visible. The images obtained at larger magnifications disclosed micro-cracks that did not appear in the biopolymer coating but only in the gold-sputtered layer, following an earlier study [ 33 ].…”

“…The main concern was to demonstrate the sensitivity of the produced coatings to a change in the pH of the media into which the samples would be introduced. Comparing the results obtained in the previous study [ 33 ], it can be said that the addition of Eudragit E 100 contributes to a significant reduction in chitosan coating degradation at neutral pH while maintaining high sensitivity to pH decrease, which is crucial in drug delivery control systems. Thus, this type of multilayer surface modification of the implant can provide long-term protection against biofilm formation and the development of postoperative infections, considered as one of the predominant causes of unsuccessful implant procedures [ 74 ].…”

“…Visible cracks in the coatings, as in Figure 4 c, represent cracks in the sputtered gold layer. Agglomeration of silver nanoparticles decreases the release of silver ions and the antibacterial protection of coating as such agglomerates possess a lower surface-to-volume ratio and less possibility of interaction with bacteria as compared to isolated nanoparticles [ 33 ]. The problem of agglomeration could be solved by adding dispersants such as Polysorbate 20, which stabilizes AgNPs by intensifying existing electrostatic repulsion forces present among these particles.…”

“…In addition, the dose of allowable silver oral exposure determined by the United States Environmental Protection Agency (US EPA) equals 0.005 mg Ag/kg body weight daily. The results indicated that at a pH of 3 for sample A1, this value was slightly exceeded; however, for the B1 sample, the silver concentration was within limits [ 33 ].…”

Effects of Surface Pretreatment of Titanium Substrates on Properties of Electrophoretically Deposited Biopolymer Chitosan/Eudragit E 100 Coatings

“…For this purpose, the surface layer of the implant is modified or a specific coating is deposited [1][2][3][4]. The coatings for implants should be characterized by high adhesion to metallic substrates under shear stresses, suitable roughness, and high resistance to corrosion phenomena [5]. Nevertheless, such structures often exhibit a weak adhesion to the metallic substrate, which is exposed to heavy loads during the implantation procedure [6].…”