K. V. Sergienko

Mechanical properties of nanostructured nitinol/chitosan composite material

The mechanical properties and degradation behavior of a composite material based on nanostructured nitinol and a biodegradable polymer surface coating of chitosan of various molecular weights are studied. The formation of a biodegradable surface layer of any composition does not change the properties of the base material. The created biodegradable polymer surface coating disintegrates upon applying the yield stress, i.e., within the operating range of loadings on medical items. The base disintegrates with the formation of a neck. Surface layer cracking is observed only near the fracture.

Kinetics of the release of antibiotics from chitosan-based biodegradable biopolymer membranes

A process for manufacture of chitosan-based biodegradable biopolymer membranes suitable for medical applications was developed. A technology for inclusion of broad spectrum antibiotics into the chitosan membranes was elaborated. The effects of pH of the solution surrounding the membranes and the initial solvent chosen for chitosan on the kinetics of release of antibiotics from the membranes were studied. It was demonstrated that the kinetics of drug release from the chitosan-based biodegradable biopolymer membranes depends on the properties of substance immobilized in the membrane, the membrane manufacture process, and extraction conditions.

Biocompatibility of new materials based on nano-structured nitinol with titanium and tantalum composite surface layers: experimental analysis in vitro and in vivo

AbstractA technology for obtaining materials from nanostructured nitinol with titanium- or tantalum-enriched surface layers was developed. Surface layers enriched with titanium or tantalum were shown to provide a decrease in the formation of reactive oxygen species and long-lived protein radicals in comparison to untreated nitinol. It was determined that human peripheral vessel myofibroblasts and human bone marrow mesenchymal stromal cells grown on nitinol bases coated with titanium or tantalum-enriched surface layers exhibit a nearly two times higher mitotic index. Response to implantation of pure nitinol, as well as nano-structure nitinol with titanium or tantalum-enriched surface layers, was expressed though formation of a mature uniform fibrous capsule peripherally to the fragment. The thickness of this capsule in the group of animals subjected to implantation of pure nitinol was 1.5 and 3.0-fold greater than that of the capsule in the groups implanted with nitinol fragments with titanium- or tantalum-enriched layers. No signs of calcinosis in the tissues surrounding implants with coatings were observed. The nature and structure of the formed capsules testify bioinertia of the implanted samples. It was shown that the morphology and composition of the surface of metal samples does not alter following biological tests. The obtained results indicate that nano-structure nitinol with titanium or tantalum enriched surface layers is a biocompatible material potentially suitable for medical applications.

The Production of a Thin Wire of Ti-Nb-Ta-Zr Shape Memory Alloy for Medical Devices

Alloys possessing a shape memory effect and mechanical characteristics similar to the behavior of living tissues have been already used for years as the material for production of medical devices, including implants, for example stents, without the need for additional devices except catheter-carrier. However, most of these alloys contain elements (including on its surface) which is toxic for organism. To satisfy the requirements of biochemical compatibility, the alloy should contain only safe elements as alloy components, which include: Ti, Nb, Ta, Zr. The possibility of obtaining of Ti-Nb-Ta-Zr thin wire was investigated. The structure was determined with the use of the optical microscope, X-ray diffractometer, scanning electron microscope (SEM) and Auger spectrometer. Optimal conditions for smelting were chosen. It was noted that a uniform structure was obtained for all compositions, before and after homogenizing annealing. The ingots have a dendritic structure. Niobium and zirconium were uniformly distributed throughout the sample, tantalum was concentrated in the dendrites themselves, titanium was predominantly in the regions between the dendritic axes, but is also found in it. X-ray diffractometry indicates that the elements of the alloy were not distributed in it by separate fragments, but were united in a single structure. The optimal annealing temperature of Ti-(20-30)Nb- (10-13)Ta-5Zr alloys was noted in the range from 600 to 900°C. The grain boundaries after plastic deformation and heat treatment were not identified in a microstructural analysis, which indicates that there was no recrystallization. It is possible that nanostructure was formed. The morphology of wires of any composition after drawing shows a high heterogeneity, two types of surfaces of different composition alternate - areas with a high content of carbon and with a high content of oxygen were observed. After mechanical treatment the surface, its uniformity increases.

Influence of the Surface Modification on the Mechanical Properties of NiTi (55.8 wt % Ni) Alloy Wire for Medical Purposes

The mechanical characteristics of a titanium nickelide alloy are studied depending on the surface machining. The additional processing improves the characteristics.

Chitosan-based films with medicines

Research on development of polymer films based on a chitosan polysaccharide filled with broad spectrum antibiotics (cefotaxime, lincomycin, gentamicin) for protection of the body from penetration of infections is carried out.