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Membrany kompozytowe przeznaczone na implanty okulistyczne

100%

Stodolak E. , Krok M. , Gumuła T. , Błażewicz S.

tom R. 9, nr 4

352-357

Zaprojektowano i wykonano materiał kompozytowy przeznaczany na śródgałkowy implant okulistyczny (implant keratocytowy). Materiałem bazowym był syntetyczny niedegradowalny terpolimer (PTFE-PVDF-PP) o stwierdzonej biozgodności (norma PN-EN ISO 10993). Jako fazę porotwórczą zastosowano biodegradowalny polimer-alginian sodu (NaAlg), którego użyto w formie proszku i włókien. Biopolimer mieszano z roztworem terpolimeru. Kompozyty otrzymywano metodą odlewania, a następnie poddawano je obróbce fizykochemicznej w celu nadania im niezbędnej porowatości. W ten sposób otrzymano biomateriał o wysokiej porowatości otwartej z systemem porów połączonych. Średnia wielkość porów w biomateriale zależy od rozmiaru cząstek fazy porogennej oraz od jej rodzaju (włókna lub proszek NaAlg). Membrana kompozytowa jest tworzywem trwałym, odpornym na długotrwałe obciążenia zarówno statyczne, jak i dynamiczne. Niewielki wzrost porowatości i wzrost wielkości porów obserwowany po testach zmęczeniowych nie powoduje deformacji tworzywa membrany i nie prowadzi do jej zniszczenia. Powierzchnie membran mają charakter silnie hydrofobowy (wyniki pomiarów kąta zwilżania i energii powierzchniowej), co utrudnia adhezję makromolekuł, będącą powodem blokowania się porów membrany. Wysoki kąt zwilżania utrzymuje się również w przypadku zastosowania jako cieczy pomiarowej medium hodowlanego wzbogacanego albuminą. Otrzymane wyniki eksperymentalne stanowiły podstawę do podjęcia dalszych badań nad zachowaniem się materiałów membranowych w warunkach in vivo.

Glaucoma is an disease in which increased intraocular pressure causes damages of the eye structure. This leads to destruction of ophthalmic nerve, and as a result, changes of the field of vision. As a secondary effect secondary changes in the eye structure are observed. The disease is caused by blocking of a natural porous eyeball structure so called drainage angle. Inflow of the aqueous medium from inside the eye to the anterior chamber is more difficult than in physiological state. This state leads to excessive accumulation of the aqueous medium in the eye ball. As a result, the increased intraocular pressure causes tissue ischemia and afterwards their necrobiosis leaing to atrophy of the ophthalmic nerve. The role of materials used in therapy of glaucoma is to decrease the pressure inside eye. Materials for such application should fulfill main criteria, such as biocompatibility, biostability and appropriate high porosity. Moreover, it is necessary to provide nonpenetrating filtration inside the eye. For long-term-use, the material applied for cornea implants also have to withstand static pressure and dynamic pressure changes and have to be stable in biological environment. Therefore, its durability in in vitro conditions plays an important role. A new composite material for intraocular ophthalmic implant (keratitis implant) was designed and manufactured. The composite matrix based on a synthetic non-degradable terpolymer (PTFE-PVDF-PP) with certified biocompatibility (PN-EN ISO 10993 standard). As a porogenic phase bio-degradable polymer - sodium alginate (NaAlg) in the form of powder and fibres was used. The biopolymer was mixed with terpolymer solution. Composites were manufactured by casting technique followed by such a physicochemical treatment which led to obtaining appropriate porosity. This procedure enable to manufacture biomaterial possessing high open porosity with interconnected pore system. The average pore size in biomaterial remains in relation with size of porogenic phases and the type of porogenic phases (fibres or particles of NaAlg). The composite membrane is a material durable and resistant to long-term static and dynamic loads. The slight increase of total porosity and pore size which was observed after fatigue tests did not lead to deformation of the membrane material and did not lead to its destruction. Surfaces of the membrane materials were highly hydrophobic (results of wetting angle measurements and surface energy determination). That prevent adhesion of macromolecules responsible for blocking of membrane pores. High value of wetting angle were registered not only in case of distilled water but also in case of using plasma enriched with albumins. On the basis of results of these experiments new tests in in vivo conditions were continued.

The relationship between the structural anisotropy of the PFA polymer/compressed expanded graphite-matrix composites and acoustic emission characteristics

100%

Berdowska S. , Berdowski J. , Aubry F.

tom Vol. 69, nr 5

art. no. e138235

The main aim of the study was to search for the relationship between the anisotropy of the structure of polyfurfuryl alcohol (PFA) – polymer/compressed expanded graphite (CEG)-matrix composites at subsequent stages of the technological process and characteristics of the acoustic emission (AE) descriptors. These composites, obtained after successive technological procedures of impregnation, polymerization, and carbonization, possess different structure, densities, porosity, and other physicochemical properties. In the structures of composites prepared on the basis of CEG, two basic directions can be distinguished: parallel to the bedding plane of graphite sheets and perpendicular to it. The measurements were carried out for the stress acting in these two main directions. The investigation has shown that the AE method enables the detection of anisotropy in the structure of materials. The results of the research show that all four of the acoustic emission descriptors studied in this work are sensitive to the technological stages of these materials on the one hand and their structure anisotropy on the other. Fourier analysis of the recorded spectra provides interesting conclusions about the structural properties of composites as well as a lot of information about the bonding forces between the carbon atoms of which the CEG matrix is composed and the PFA polymer or turbostratic carbon.