No abstract

A galvanic method to deposit chitosan coatings on stainless steel substrate is reported. Deposition of suitable coatings is desired to improve biocompatibility and corrosion resistance of metallic medical devices to be implanted in human body. In the present work, a thin hydrogel layer of chitosan was deposited on 304SS by a galvanic displacement reaction, which is advantageous first as it does not require external power supply. 304SS was immersed into an aqueous solution of chitosan/lactic acid and electrochemically coupled with magnesium acting as a sacrificial anode. SEM images showed the formation of a uniform layer of chitosan with a thickness controlled by deposition time. Corrosion tests in simulating body fluid showed that chitosan coatings shift the corrosion potential of 304 substrates toward nobler values. Finally, the cytotoxicity of the coating was investigated through cell viability assays with osteoblastic cell MC3T3-E1. The results revealed highly satisfying biocompatibility of the coating.

Corrosion behavior and cytotoxicity was reported for mixed brushite (BS)/hydroxyapatite (HA) coatings deposited on 316LSS substrate through a displacement reaction. Corrosion tests, carried out in a simulated body fluid, showed that in comparison with bare 316L, coating shifts E corr to anodic values and reduces i corr even if oscillations were observed, which were explained in terms of the chemical interactions at the solid/liquid interface. Cell biocompatibility of the coating was investigated through osteoblastic cell line MC3T3-E1, evidencing the absence of any cytotoxicity Taken together, the results show that galvanic deposition is a simple and cost-effective method for producing bioactive coatings which enhance corrosion resistance and biocompatibility of the substrate.

During the last decades, biomaterials have been deeply studied to perform and improve coatings for biomedical devices. Metallic materials, especially in the orthopedic field, represent the most common material used for different type of devices thanks to their good mechanical properties. Nevertheless, low/medium resistance to corrosion and low osteointegration ability characterizes these materials. To overcome these problems, the use of biocoatings on metals substrate is largely diffused. In fact, biocoatings have a key role to confer biocompatibility properties, to inhibit corrosion and thus improve the lifetime of implanted devices. In this work, the attention was focused on Hydroxyapatite-Chitosan (HA/CS) and Hydroxyapatite-Polyvinylacetate (HA/PVAc) composites, that have been studied as biocoatings for 304 SS based devices. Hydroxyapatite was selected for its osteoconductivity thanks to its chemical structure similar to bones. Furthermore, Chitosan and Polyvinylacetate are largely used yet in medical field (e.g. antibacterial agent or drug deliver) and in this work were used to create a synergic interaction with hydroxyapatite to increase the strength and bioactivity of coating. Biocotings were obtained by galvanic deposition process that does not require an external power supply. It is a spontaneous electrochemical deposition in which materials with different standard electrochemical potential were short-circuited and immersed in an electrolytic solution. Electrons supply for the cathodic reaction in the noblest material comes from oxidation of the less noble material. SEM, EDS, XRD and RAMAN were performed for chemical-physics characterization of biocoatings. Polarization and impedance measurements have been carried out to evaluate corrosion behavior. Besides, in-vitro cytotoxicity assays have been done for the biological features.