ICMCTF2016 Session D2-1: Surface Coatings, Micro/Nano Texturing, Nanotubes, Drug Delivery, Biodegradable Implants

This study was focused on the coating of TiO₂ layer by using the method of Micro Ark Oxidation with the aim of the improvement of surface and mechanical properties of Shaped-memory and bio material NiTi alloy. In vitro ability was investigated by soaking the coated NiTi samples in simulated body fluid (SBF) at temperature 37 °C for various time periods. After soaking, Ni⁺² release was applied to the media where coated and uncoated shape-memory NiTi samples are available, and its control was made by means of ICP-MS device. In-vitro cytotoxicty tests of coated and uncoated samples were made by means of XTT test. The results show that the bioactivity and bioadaptation properties on aggressive surfaces such as body fluid contacted are increased by the TiO₂ coating. The results also show that Toxic and carcinogenic effects of Ni⁺² release is significantly reduced by the TiO₂ coating. Thus, it is observed that the properties that limit the use of NiTi alloys has been substantially fixed by MAO coating.

A critical aspect in the development of materials for biomedical applications is the optimization of their surface properties to achieve an adequate cell response. In the present work, biocompatible scaffolds were prepared by electrospinning solutions of poly-L-lactide (PLLA) and poly(ε-caprolactone)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PCL/PHBV). The electrospun scaffolds were modified by plasma of magnetron discharge with titanium (Ti) target sputtering in argon atmosphere. The influence of the plasma treatment time on morphology, chemical composition, crystalline structure and mechanical properties of the scaffolds was investigated. Also, in vitro experiments on cultured human endothelial hybrid cell line EA-hy 926 were conducted in order to study the effect of plasma treatment over cell adhesion and viability. It was demonstrated that plasma treatment can enhance the biocompatibility of the fibrous scaffolds.

Most of these applications rely on the so-called Localized Surface Plasmon Resonance (LSPR) absorption, which is governed by the type of the noble metal nanoparticles, NPs, their distribution, size and shape and as well as of the dielectric characteristics of the host matrix [2]. Since changes in size, shape and distribution of the clusters are fundamental parameters for tailoring the LSPR effect, a set of films with a wide range of noble metal concentration was prepared and the optical responses analyzed in detail. The films were deposited by DC magnetron sputtering and in order to promote the clustering of the NPs the as-deposited samples were subjected to an in-air annealing protocol. Results show that the clustering of metallic NPs affects the optical response spectrum and, for certain volume fractions, it broadens when the polarizable NPs are non-randomly distributed in the matrix. This will be the starting point to study the application of such thin film system in a wide range of bio-sensing applications.

The microstructural changes (structure, grain size and surface morphology) of the films promoted by heat-treatment seems to rule the overall biological response, as it will be shown by the interaction of the thin films with well-known proteins such as Bovine Serum Albumin (BSA), as well as with microbial cells (C. albicans). In fact, preliminary results showed that the BSA adhesion is dependent on surface nanostructure morphology, which in turn depends on the annealing temperature that changed the roughness and wettability of the films. The thin films also induced a significant alteration of the microbial cell membrane integrity, and ultimately the cell viability, which in turn affected the adhesion on its surface.

Camphor was incorporated into diamond-like carbon (DLC) films to prevent growth of candida albicans yeasts on polyurethane substrates, which is a material commonly used for catheter manufacturing. The camphor:DLC film for this investigation was produced by plasma enhanced chemical vapor deposition (PECVD), using an apparatus based on the flash evaporation of organic liquid (hexane) containing diluted camphor. The film was deposited at low temperature less than 25 °C. We obtained very adherent camphor:DLC films that accompanied the substrate flexibility without delamination. The camphor:DLC films were characterized by Raman spectroscopy, scanning electron microscopy, and atomic force microscopy. Biofilms of candida yeasts were cultivated in vitro and where developed on polyurethane, with and without camphor:DLC, to verify fungicide properties of DLC. In addition, colony-forming units (CFU /mL) were used to measure the number of microorganisms on the surface of the sample. The camphor:DLC films prevented growth of candida biofilms better than bare polyurethane. This resulted in 99.0% and 91.0% protection for camphor:DLC and DLC, respectively, when compared to polyurethane, which was totally contaminated. These results open the doors to studies of DLC coatings with fungicide properties deposited in polymers such as polyurethane used in the production of catheters or other biomedical applications.