Durability of the Exterior Transparent Coatings on Nano-Photostabilized English Oak Wood and Possibility of Its Prediction before Artificial Accelerated Weathering

Changes in surface material characteristics can significantly affect the adhesion and overall life of coatings on wood. In order to increase the durability of transparent exterior coatings, it is possible to use the surface modification of wood with UV-stabilizing substances. In this work, selected types of surface modifications using benzotriazoles, HALS, ZnO and TiO2 nanoparticles, and their combinations were applied to oak wood (Quercus robur, L.). On such modified surfaces, the surface free energy, roughness, and contact wetting angle with three selected types of exterior transparent coatings were subsequently determined. An oil-based coating, waterborne acrylic thick layer coating, and thin-layer synthetic coating were tested and interaction with the aforementioned surface modifications was investigated after 6 weeks of accelerated artificial weathering. The results of changes in the initially measured surface characteristics of the modified oak wood were compared to the real results of degradation of coatings after artificial accelerated weathering. The positive effect of surface modification, in particular the mixture of benzotriazoles, HALS, and ZnO nanoparticles on all kinds of coatings was proven, and the best results were observed in thick-film waterborne acrylic coating. The changes in the measured surface characteristics corresponded to the observed durability of the coatings only when measured by wetting using drops of the tested coatings.

Porous Titanium Surfaces to Control Bacteria Growth: Mechanical Properties and Sulfonated Polyetheretherketone Coatings as Antibiofouling Approaches

Here, titanium porous substrates were fabricated by a space holder technique. The relationship between microstructural characteristics (pore equivalent diameter, mean free-path between pores, roughness and contact surface), mechanical properties (Young’s modulus, yield strength and dynamic micro-hardness) and bacterial behavior are discussed. The bacterial strains evaluated are often found on dental implants: Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. The colony-forming units increased with the size of the spacer for both types of studied strains. An antibiofouling synthetic coating based on a sulfonated polyetheretherketone polymer revealed an effective chemical surface modification for inhibiting MRSA adhesion and growth. These findings collectively suggest that porous titanium implants designed with a pore size of 100–200 µm can be considered most suitable, assuring the best biomechanical and bifunctional anti-bacterial properties.

Multidisciplinary treatment of ischemic forms of diabetic foot

Purpose of the study. The phototherapy, platelet growth factor and coating materials in the treatment complex using for improve the results of wound treatment in patients with the ischemic form of diabetic foot. Materials and methods. The analysis of the results of treatment of 48 patients with ischemic forms of diabetic foot syndrome has been performed in the work. The patients were divided into the study and comparative groups. The patients were treated at the clinic of the State institution «V. T. Zaitsev Institute of General and Emergency Surgery National Academy of Medical Sciences of Ukraine» from 2012–2018, and all patients had II stage diabetes mellitus and IV degree of ischemia by Fontaine. Patients in both groups performed open and hybrid reconstructions. In the patients of the study group, the developed treatment technology was applied, containing phototherapy and photodynamic therapy with a range of: λ 470, 525 or 405 nm in the preoperative period, closure with synthetic coating with application plasma enriched of transforming growth factor. The implementation of the developed tactics allowed to achieve complete wound healing in 91,7% of patients, partial healing – in 8,3% of patients. The terms treatment terms for these patients did not exceed 2 months, high amputation was not required. Conclusions. Plastic closure of the wounds of the lower extremities after revascularization operations in an ischemic diabetic foot syndrome is indicated in cases where wounds do not tend to spontaneous healing. The use of a treatment complex consisting of phototherapy and photodynamic therapy, the closure of wounds with a synthetic coating of transforming growth factor is the effective stimulator of development of granulation tissue in the wound, suitable for further autodermoplasty. Keywords: foot ischemic diabetic syndrome, dermoplasty, synthetic coatings, photodynamic therapy, platelet growth factor.

Synthetic Biomimetic Carbonate-Hydroxyapatite Nanocrystals for Enamel Remineralization

New biomimetic carbonate-hydroxyapatite nanocrystals (CHA) have been designed and synthesized in order to obtain a remineralization of the altered enamel surfaces. Synthesized CHA mimic for composition, structure, nano dimension and morphology bone apatite crystals and their chemical-physical properties resemble closely those exhibited by enamel natural apatite. CHA can chemically bound themselves on the surface of natural enamel apatite thanks to their tailored biomimetic characteristics. The remineralization effect induced by CHA represents a real new deposition of carbonate-hydroxyapatite into the eroded enamel surface scratches forming a persistent biomimetic mineral coating, which covers and safeguards the enamel structure. The experimental results point out the possibility to use materials alternative to fluoride compounds which is commonly utilized to contrast the mechanical abrasions and acid attacks. The apatitic synthetic coating is less crystalline than enamel natural apatite, but consists of a new biomimetic apatitic mineral deposition which progressively fills the surface scratches. Therefore the application of biomimetic CHA may be considered an innovative approach to contrast the acid and bacteria attacks.

Relationship Between Platelet Adhesion And Free Energies At Solid-Liquid Interfaces

Surface induced thrombosis remains an obstacle to extra-corpeal circulation and invasive investigation and therapy of the cardiovascular system. Although the molecular details of the blood-foreign surface interaction remain incompletely understood, from a thermodynamic viewpoint, thrombosis can only occur if thrombus formation lowers the free energy of the blood-surface system. We have recently reported a method of estimating surface free energies under physiological conditions from measurements of surface wetting by polar hydrophobic fluids. Here we report a correlation between interfacial energies and platelet retention on natural and artificial surfaces, and the effects on platelet retention of a synthetic coating developed in an attempt to mimic the thromboresistance of healthy endothelium. This coating has a lower surface energy than the artery and it appears to be equally thromboresistant.