Microstructural and micromechanical characteristics of composite osteoconductive coatings deposited by the atmospheric pressure plasma technique.

Long-term placement of facial implants requires avoiding the formation of fibrous tissue capsules around the artificial material by creating osteoconductive properties of the surface. Most promising approach is the deposition coatings made of materials very similar to bone mineral components, that is, calcium phosphates such as hydroxyapatite (HAp). As part of the research work, an innovative, cost-effective atmospheric pressure plasma deposition (APPD) system was used as a low-temperature coating technology for generating the HAp coatings deposition. Full microstructural characterisation of the coatings using SEM and TEM techniques was carried out in the work. It has been shown that the fully crystalline HAp powder undergoes a transformation during the coatings deposition and the material had a quasi-sintered structure after deposition. The crystalline phase content increased at the coating/substrate interface, while the surface of the HAp was amorphous. This is a very beneficial phenomenon due to the process of bioresorption. The amorphous phase undergoes much faster biodegradation than the crystalline one. In order to increase the bioactivity of the HAp, Zn particles were introduced on the surface of the coating. The TEM microstructural analysis in conjunction with the qualitative analysis of the EDS chemical composition showed that the binding of the Zn particles within the HAp matrix had diffusive character, which is very favourable from the point of view of the quality of the adhesion and the bioactivity of the coating. In the case of such a complex structure and due to its very porous nature, micromechanical analysis was carried out in situ in SEM, that is, by microhardness measurements of both the HAp matrix and the Zn particle. It was shown that the average value of HAp microhardness was 4.395 GPa ± 0.08, while the average value of Zn microhardness was 1.142 GPa ± 0.02.

Single- and Multilayer Build-Up of an Antibacterial Temperature- and UV-Curing Sol-Gel System with Atmospheric Pressure Plasma.

The versatility of sol-gel systems makes them ideal for functional coatings in industry. However, existing coatings are either too thin or take too long to cure. To address these issues, this paper proposes using an atmospheric pressure plasma source to fully cure and functionalize thicker sol-gel coatings in a single step. The study explores coating various substrates with sol-gel layers to make them scratch-resistant, antibacterial, and antiadhesive. Microparticles like copper, zinc, or copper flakes are added to achieve antibacterial effects. The sol-gel system can be sprayed on and quickly functionalized on the substrate. The study focuses on introducing and anchoring particles in the sol-gel layer to achieve an excellent antibacterial effect by changing the penetration depth. Overall, this method offers a more efficient and effective approach to sol-gel coatings for industrial applications. In order to achieve a layer thickness of more than 100 µm, the second part of the study proposes a multilayer system comprising 15 to 30 µm thick monolayers that can be modified by introducing fillers (such as TiO2) or scratch-resistant chemicals like titanium isopropoxide. This system also allows for individual plasma functionalization of each sol-gel layer. For instance, the top layer can be introduced with antibacterial particles, while another layer can be enhanced with fillers to increase wear resistance. The study reveals the varying antibacterial effects of spherical particles versus flat flakes and the different scratch hardnesses induced by changes in pH, number of layers, and particle introduction.

Antimicrobial Activity of a Novel Cu(NO3)2-Containing Sol-Gel Surface under Different Testing Conditions.

In this study, assessment of the antimicrobial activity of a novel, plasma-cured 2.5% (w/v) Cu(NO3)2-containing sol-gel surface was performed. In contrast to state-of-the-art sol-gel coatings, the plasma curing led to a gradient in cross-linking with the highest values at the top of the coating. As a result, the coating behaved simultaneously hard, scratch-resistant, and tough, the latter due to the more flexible bulk of the coating toward the substrate. Further, the diffusion and permeation through the coating also increased toward the substrate. In our study, tests according to ISO 22196 showed antibacterial activity of the 2.5% (w/v) Cu(NO3)2-containing sol-gel surface against all bacterial strains tested, and we expanded the testing further using a "dry" evaluation without an aqueous contact phase, which confirmed the antimicrobial efficacy of the 2.5% (w/v) Cu(NO3)2-containing sol-gel surface. However, further investigation under exposure to soiling with the addition of 0.3% albumin, used to simulate organic load, led to a significant impairment in the antibacterial effect under both tested conditions. Furthermore, re-testing of the surface after disinfection with 70% ethanol led to a total loss of antibacterial activity. Our results showed that besides the mere application of an antimicrobial agent to a surface coating, it is also necessary to consider the future use of these surfaces in the experimental phase combining industry and science. Therefore, a number of tests corresponding to the utilization of the surface should be obligative on the basis of this assessment.