Polymers with functionalized surfaces have attracted a lot of attention in the last few years. Due to the progress in the techniques of polymer micro-patterning, miniaturized bioanalytical assays and biocompatible devices can be developed. In the presented work, we performed surface modification of polyethylene naphthalate (PEN) foil by an excimer laser beam through a photolithographic contact mask. The aim was to fabricate micro-patterned areas with surface functional groups available for localized covalent immobilization of biotin. It was found out that depending on the properties of the laser scans, a polymer surface exhibits different degrees of modification and as a consequence, different degrees of surface biotinylation can be achieved. Several affinity tests with optical detection of fluorescently labeled streptavidin were successfully performed on biotinylated micro-patterns of a PEN foil. The polymer surface properties were also evaluated by electrokinetic analysis, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results have shown that PEN foils can be considered suitable substrates for construction of micro-patterned bioanalytical affinity assays.
- MeSH
- biotin chemie MeSH
- biotinylace MeSH
- fotochemické procesy MeSH
- laboratoř na čipu MeSH
- lasery excimerové MeSH
- mikrotechnologie MeSH
- naftaleny chemie účinky záření MeSH
- polyethyleny chemie účinky záření MeSH
- povrchové vlastnosti MeSH
- streptavidin chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Ultrahigh molecular weight polyethylene (UHMWPE) is the most frequently used bearing surface in currently used total joint replacements (TJR). According to the literature available, UHMWPE is the best polymer material, in terms of biocompatibility, mechanical properties and wear resistance, for this application. In spite of this fact, UHMWPE wear (i.e., release of microscopic particles from the polymer surface) remains one of the main reasons of TJR failures. Consequently, the wear of UHMWPE is a subject of intensive study by both materials scientists and orthopaedic surgeons. The structure and properties of UHMWPE strongly depend on the way of processing and post-processing modifications. The processing includes polymer resin preparation (microparticles about 100 urn in size) and resin consolidation (forming bulk material). Post-processing modifications aim at increasing wear resistance and oxidation stability which are regarded as major factors involved in TJR failure. In order to maintain high purity materials for medical application, it is not allowed to use additional chemicals during the modification processes. The only exception is the use of vitamin E, a natural stabilizer and antioxidant. Considering all the above mentioned facts, the modifications can be based on (I) ionizing radiation such as gamma rays or accelerated electrons, (II) thermal modification, (III) additional stabilization with vitamin E, and (IV) sterilization. According to the modifications, we usually differentiate three generations of UHMWPE. The 1st generation UHMWPE is not modified except for obligatory sterilization. The sterilization procedures based on chemical procedures (formaldehyde vapours, hot water) have lately been forbidden, abandoned and replaced by gamma-irradiation with doses of 25-45 kGy In the course of time, sterilization by means of gamma-irradiation showed to be unsuitable due to oxidative degradation of UHMWPE, which resulted in lower wear resistance, worse material properties and a decrease in longevity of joint replacements. The 2nd generation UHMWPE or highly cross-linked UHMWPE is material treated with ionizing radiation (gamma-rays or accelerated electrons) at higher doses (usually 50-100 kGy). The irradiation is followed by thermal treatment in order to eliminate residual radicals and limit oxidative degradation that occurs in the 1st generation UHMWPE types. Finally, the material is sterilized usually by modern procedures using ethylene oxide or gas plasma neither of which causes oxidative degradation (as opposed to gamma-irradiation sterilization). The 3rd generation UHMWPE is basically the same as that of the 2nd generation. The main difference consists in slightly better mechanical properties (strength, fatigue) and further stabilization to oxidative degradation. This is achieved by special procedures, some of which are either controversial (sequential irradiation) or well-accepted by a great majority of the orthopaedic community (vitamin E stabilization). Only the future will show whether the difference between the 2nd and 3rd generations of UHMWPE will play any role in increasing TJR longevity and therefore the quality of its performance. The final objective of all of UHMWPE modifications is, as already mentioned, to increase wear resistance, oxidative resistance and mechanical performance of the polymer. These changes, especially an increase in wear resistance, have been confirmed to prolong the longevity of total joint replacements based on UHMWPE.
- MeSH
- artroplastiky kloubů MeSH
- biokompatibilní materiály MeSH
- biomechanika MeSH
- lidé MeSH
- polyethyleny chemie účinky záření MeSH
- protézy kloubů MeSH
- sterilizace MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- přehledy MeSH
Ultra-high molecular weight polyethylene (UHMWPE) was irradiated with accelerated electrons (1 MeV in air) using high dose rates (> 25 kGy/min) and thin specimens (thickness 1 mm). Parts of the specimens were remelted (200 degrees C for 10 min; 150 degrees C for 0, 2, 10, 30, 60 min). All specimens were stored in nitrogen in the dark at 5 degrees C. Supermolecular structure, extent of crosslinking, oxidative degradation, and macroradical content were studied by a number of methods (SAXS, WAXS, SEM, DSC, FTIR, ESR, TGA, solubility experiments, image analysis). The results obtained with irradiated samples were compared with those obtained with irradiated and remelted samples. It was confirmed that crosslinking predominates over chain scission at very high dose rates, even if the irradiation is performed in air. Discrepancies concerning supermolecular structure changes in UHMWPE after irradiation and thermal treatment, found in various studies in the literature, are discussed. A simple model, which describes and explains all supermolecular structure changes, is introduced. An effective way of eliminating residual macroradicals in UHMWPE is proposed.
- MeSH
- analýza selhání vybavení MeSH
- biokompatibilní materiály chemie účinky záření MeSH
- diferenciální skenovací kalorimetrie MeSH
- elektrony MeSH
- financování organizované MeSH
- lidé MeSH
- mikroskopie elektronová rastrovací MeSH
- molekulární struktura MeSH
- oxidace-redukce MeSH
- polyethyleny chemie účinky záření MeSH
- povrchové vlastnosti MeSH
- protézy kloubů MeSH
- rozpustnost MeSH
- selhání protézy MeSH
- teplota MeSH
- testování materiálů MeSH
- záření MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- hodnotící studie MeSH
