CHITOSAN / SILICA-CALCIA NANO-PARTICLES COATINGS ONTO SURGICAL GRADE STAINLESS STEEL: PRELIMINARY APPROACH OF ITS BIOLOGICAL RESPONSE.

MARIA ROSA KATUNAR; FLORENCIA DIAZ; ALDO BOCCACCINI; JOSEFINA BALLARRE

San Pablo

Congreso; XI COLAOB and XVII LASAO XI Latin American Congress of Artificial Organs and Biomaterials; 2021

.Metals used for prothetic devices do not generally generate efficient natural bonding with bone tissue and it is then necessary to produce a mechanical anchor. Surface modification of materials is one of the most used methods to improve the biomaterial performance. The use of stainless steel removable screws or plates for bone fixation is nowadays considered. Also some apatite derivate coatings have been proposed over the past years to improve their bioactivity. Silica based bioactive glasses in nanoparticles shape can be used as apatite precursors. Sol-gel method is a siutable one to generate porous and homogeneous systems, capable of enhance dissolution rates. The aim of this study is to enhance the bioactivity of stainless steel implants by a electrophoretic deposited coating made of chitosan and silica-calcia nanoparticles. Monodispersed spherical glass nanoparticles (nG) were prepared according to a modified Stober method (1). Two silica-calcia nanopaticles concentration, 0.5 (0.5nG) and 0.75 (0.75nG) g/L were used. Coatings were made by electrophoretic deposition, with direct current (DC) of 30V applied for 3 minutes (2). Planar sheets of AISI 316L stainless steel plates (2.5cm x 3cm x 0.2 cm) were used as counter electrodes and substrates. For a preliminary biological characterization, in vitro cell essays were carried on. To asses cell viability, proliferation, and morphology on the different sample surfaces, the murine stromal cell line ST-2 was used and evaluated at 1,4 and 10 days after seeding. From the WST-8 assay, after 1 day, a few amount of cells adhered and proliferated over 0.5nG; 0.75nG and SS316L samples. However, by day 4 the number of cells over all the surfaces increased compared to the first time point, and continued growing on every samples up till 10 days. Even though, a delayed could be observed over 0.5nG and 0.75nG conditions. Regarding to cell morphology, after one day of seeding, cells over 0.5nG and 0.75nG appeared to be not well spread through all surfaces. Nevertheless, cell number over 0.75nG could be higher compared to 0.5nG. By day 4, an increased number of cells on all surfaces could be observed; however, over 0.5nG and 0.75nG samples cells adhesion was not homogenous showing that the coating was not homogenous as well. At the end point of the experiment (day 10), cells over 0.75nG proliferated with a resulting formation of a cell sheet monolayer and with a better promising cell morphology compared to 0.5nG samples. In both conditions 0.5nG and 0.75nG, as magnification increased, was very difficult to focus the cells, and was hard to clearly see the morphology along the days. This leads us to hypothesize that the change in morphology observed for both 0.5 and 0.75nG samples could be associated with processes related to the dissolution of the coatings; being necessary to evaluate the behaviour of the coating in culture medium at different time points. Complementary assays should be done to confirm that this surface treatment would be a promising superficial treatment for enhance stainless steel behaviours for biomedical applications.