ICMCTF 2023 Session DP-ThP: Coatings for Biomedical and Healthcare Applications (Symposium D) Poster Session

Tetrahedral amorphous carbon (ta-C) coating is a hydrogen-free carbon coating with the remarkable properties comparable with those of diamond film, such as high hardness, optical transparency and chemical inertness. In this study, as silver (Ag) is known to be a potent antibacterial agent, silver (Ag) doped ta-C coatings with different Ag concentrations were synthesized on the AISI 316Land Ti64 coupons using an hybrid filtered cathodic vacuum arc (FCVA) and magnetron sputtering system. The doping effects of Ag concentration in ta-C coatings on the bacteria biofilms formed on the surface of medical products were examined. Surface condition and its physicochemical properties were investigated using SEM, AFM and XPS and also studied was their antibiofilm efficacy against a multi-drug resistant nosocomial pathogen Pseudomonas aeruginosa. In addition the antibacterial activity of Ag doped ta-C was evaluated by bacterial eradication tests with Escherichia coli (E. coli) at different incubation times.The result revealed that the synthesized Ag doped ta-C coatings inhibited the biofilm formation of P. aeruginosaand the antibacterial activity against E. coliin a concentration-dependent manner. Hence, this study demonstrated the possible use of Ag doped ta-C coatingsagainst the biofilm-related infections out of P. aeruginosa and antibacterial activity against E. coli. Experimental details will be discussed.

Surface treatment and functional coating can effectively reduce the degrading status and promote the blood compatibility of magnesium implants. This study applied micro-arc oxidation (MAO) treatment to improve the corrosion resistance of magnesium alloy. The electrolyte was prepared by using sodium silicate, sodium hydroxide, and sodium citrate. The MAO process was performed by adjusting voltage which was determined by observing the completeness of the ceramic films. Then, Layer-by-layer assembly technique was implemented by dipping the substrates with graphene oxide, oxidized polydopamine mixed with pyrolytic 1,8-diaminooctane sequentially to provide their corrosion resistance, adhesive strength, and anti-clotting capability. The composition of substrate was confirmed by inductively coupled plasma mass spectrometry. Microstructural morphologies and crystallography of the MAO coatings were characterized using X-ray diffraction. Optical microscopy was implemented to observe the topographies of coatings. The samples’ surface transition was revealed by water contact angle. Their surface topographies and element were observed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The cross-sectional morphology and the film thickness were evaluated by dual-beam focused ion beam microscopy. The function groups contained in composite multilayers were examined by Fourier transform infrared spectroscopy. The degradation resistance was measured by corrosion polarization curve. The combination of the multilayers was investigated by conducting scratch tests.The hemocompatibility of composite films for original, 7 days, and 15 days were studied according to the activated partial thromboplastin time and the platelet adhesion experiment. The results indicated that the coatings with multilayers of graphene oxide, oxidized polydopamine mixed with pyrolytic 1,8-diaminooctane layers after micro-arc oxidation had the best adhesion strength, corrosion resistance, and anticoagulant ability which can sustain more than 7 days under theorbital shaking tests.

Stainless steels (SSs) containing antibacterial elements, such as copper element, could be used as antibacterial structural materials. However, the traditional metallurgical processes for the fabrication of copper-containing SSs include melting, casting, rolling and many other steps, which are highly costive and inconvenient for final product manufacturing. Furthermore, for ferritic and martensitic stainless steels, the low copper solubility in these grades of stainless steels makes copper alloying more difficult. Therefore, this study aims to develop a novel method for preparing copper-containing martensitic SS (namely SS 440C) on its surface by incorporating electrochemical plating and thermal diffusion process.

Surgical instruments require medical grade and biocompatible materials with good corrosion resistance and tensile strength. Austenitic stainless steels are appropriate materials that can provide a sharp edge for repetitive use in medical procedures. These surgical tools may be cutting and holding tools or closure and hemostatic tools such as suture needles.

This research aims to enhance suture needles for improved ease of use in the repetitive suturing of large incisions. The shape of the needle body and the sharpness of the needle tip determines the force acting on suture needles. Therefore, better ease of use in terms of a smaller resistance force, a smaller body diameter, and a sharper needle tip are preferable. However, as we reduce the body diameter and sharpen the needle tip, the needle strength tends to decrease, and bending of the needle tip and possibly the needle body occurs, resulting in a short useful life span. In this study, surgical suture needles are plasma nitrided to suppress the bending of the needle tip and body for applications in large incisions.

Currently, silicone-coated or metallic glass-coated modified surfaces are the available methods that enhance the durability of surgical tools. However, delamination of the coating while in use may cause an undesirable medical problem for the subject and compromise the sharpness of the needle tip. This study aims to determine the insertion-retraction characteristics of untreated, silicone-coated, and plasma-nitrided suture needles. The results of our experiments show the measured insertion-retraction characteristics curves of plasma nitrided suture needles were superior to those of the silicon-coated and untreated samples tested. Furthermore, since plasma nitriding is a diffusion process, the dimensional changes are minimal and no danger of delamination. The presentation will show the performance of plasma-nitrided stainless steel surgical suture needles.

The development of ideal surfaces to be used in metal implants and osseus stabilization devices require the consideration of different phenomena such as the formation of a bacterial biofilm on the surface followed by the usual appearance of infections or the total rejection of the device. On the other hand, the overgrowth of bone material around these devices constitutes a barrier when it comes to removing them when their function has been fulfilled. Due to this, the development of multilayer antibacterial coatings of TiO2/Ag on Ti6Al4V substrates by means of the Magnetron Sputtering technique for its potential use in non-permanent implants were studied. The coatings obtained using this technique exhibit a uniform and densely packed, columnar growth profile and it also offers significant control over the microstructural features. Consequently, the properties of the developed systems were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), tribologic assays and surface properties such as rugosity and contact angle.

This study aims to improve the initial corrosion and biocompatibility of biodegradable magnesium by coating the magnesium surface with calcium phosphate containing strontium by electrodeposition. In this study, calcium phosphate coatings doped with Sr of various concentrations were electrodeposited on the magnesium surface at an applied voltage of 4 V for 1 h. The corrosion behavior and biocompatibility of the modified magnesium surfaces were evaluated.

The surface of the magnesium coated with strontium-calcium phosphate showed a dense dendritic shape and became denser as the strontium content increased. strontium-calcium phosphate coated magnesium showed improved corrosion resistance and lower pH change than pure magnesium. In vitro strontium-calcium phosphate coated magnesium showed enhanced bioactivity. strontium-calcium phosphate coated magnesium showed excellent osteoblast proliferation and differentiation.

Therefore, the strontium-calcium phosphate developed in this study inhibited the initial corrosion of magnesium and effectively formed corrosion products and bioactive materials on the surface. In addition, excellent biocompatibility was confirmed.

"This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education (No. 2021R1I1A1A01057579) and the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2021R1A2C2005466)"

Acid erosion is common in patients with gastroesophageal reflux disease or eating disorders (nervous bulimia and/or anorexia). Such condition can degrade the mechanical strength of oral restorative materials such as ceramics. Surface treatments have been used to protect or improve the mechanical properties of ceramic materials. In this context, plasma-enhanced chemical vapor deposition (PECVD) is a promising technique for depositing a thin film on ceramics. Therefore, we aimed to evaluate the structural and mechanical characteristics of zirconia/silica ceramic in a CAD-CAM interpenetrating resin matrix (Shofu Block HC) as a function of different finishing procedures associated or not with PECVD after erosive challenge. A total of 120 specimens were divided into 4 groups of surface finishing: only mechanical polishing (MP), only application of light-curing sealant (S), association of MP or S with PECVD (MP+PECVD and S+PECVD). A steel reactor was used for PECVD application and a thin-film was deposited under an atmosphere of 85% hexamethyldisiloxane monomer (HMDSO) and 15% argon (Ar). The erosive challenge was performed with 5% HCl (pH = 2.0) for 273 h. The surface roughness (Ra), surface free energy, Vickers microhardness, flexural strength, and elastic modulus of ceramic material as a function of surface finishing were investigated before and after the erosive challenge. A homogeneous silicon-based thin film was successfully deposited on ceramic surface. The PECVD thin film was able to reduce the surface roughness and increase flexural strength of ceramic when associated with mechanical polishing, even after erosive challenge, while the other groups had an increase in roughness (p<0.05). In general, PECVD increased the ceramic surface hardness, and reduced the surface free energy when associated with mechanical polishing or sealant application before and after erosive challenge (p<0.05). In conclusion, the PECVD thin film effectively enhanced the roughness, hardness, surface energy, flexural strength, and elastic modulus of zirconia/silica ceramic in an interpenetrating resin matrix, mainly when associated with mechanical polishing. The creating of silicon-based thin films might be a good strategy to reduce ceramic degradation in the oral environmental.

Funding from São Paulo Research Foundation (FAPESP) (Grants # 2021/08529-7 and 2021/07251-5).