Synthesis, characterization, and in vitro degradation of poly(L-lactic acid-co-glycolic acid), PLGA

The use of bioabsorbable polymers in the medical area has been increasing every year. Among the bioreabsorbable polymers mostly studied, is poly (L-lactide-co-glycolide), PLGA, whose main characteristic is to present short time of degradation and for that, applied as sutures, devices for controlled liberation of medicines and guided regeneration of fabric in contact with the bone, periodontia. The aim of this work was to synthesize, to characterize and to evaluate the in vitro degradation process of PLGA membranes. The copolymer was synthesized by ring opening of the cyclic diesters d of lactic acid and glicolic acid, using as catalyst Sn(Oct)2. PLGA presented high values of molar mass (Mw around 10(5) g/mol) and its chemical structure was confirmed by ¹H NMR, 13C NMR, and FTIR spectrometry data. The thermal properties of PLGA by DSC, confirmed that the polymer in this relation 80/20 is amorphous. In vitro degradation of PLGA membranes showed that the polymer became crystalline as a function of the degradation time.A utilização de polímeros bioreabsorvíveis na área médica tem aumentado a cada ano. Dentre os polímeros bioreabsorvíveis mais estudados, encontra-se o poli (L-ácido láctico-co-ácido glicólico), PLGA, cuja principal característica é apresentar curto tempo de degradação e por isso, aplicado como suturas, dispositivos para liberação controlada de medicamentos e regeneração guiada de tecido em contato com o osso, periodontia. Os objetivos deste trabalho foram sintetizar, caracterizar e estudar a degradação in vitro de membranas de PLGA. O copolímero foi sintetizado através da abertura dos dímeros cíclicos do ácido láctico e do ácido glicólico, utilizando como catalisador o Sn(Oct)2. Obteve-se PLGA com valores de massa molar ( MW ) da ordem de 10(5) g/mol e sua estrutura química foi confirmada através de RMN de ¹H e 13C e IR. As propriedades térmicas do PLGA foram estudadas por DSC, sendo verificado que o copolímero, na relação estudada, 80/20 é amorfo. O estudo da degradação in vitro das membranas do PLGA, mostrou o surgimento de cristalinidade em função do tempo de degradação.34035

Initial study of in vivo degradation of poly(L-lactic acid-co-D,L ácid láctic), PLDLA

The copolymer poly (L-co-D,L lactic acid), PLDLA, has gained prominence in the field of temporary prostheses due to the fact that their time of degradation is quite compatible with the requirement in the case of osseous fracture. In this work the in vivo degradation of devices from copolymer, as a system of plates and screws, used in fixation of the tibia of rabbits was studied. The devices were implanted in 15 adult rabbits, albinos, New Zealand race, and they were used as control devices of alloys of titanium (Ti-6Al-4V/ V grade). The use of copolymers, synthesized in the laboratory, was tested in the repair of fracture in rabbits'tibias, being assessed in the following times: 2 weeks, 2 months and 3 months. Morphological analysis of tissue surrounding the plate and screw system, for 2 weeks of implantation, showed the presence of osteoblasts, indicating a pre bone formation. After 2 months there was new bone formation in the region in contact with the polymer. This bone growth occurred simultaneously with the process of PLDLA degradation, invading the region where there was polymer and after 3 months there was an intense degradation of the copolymer and hence greater tissue invasion compared to 2 months which characterized bone formation in a region where the polymer degraded. The in vivo degradation study of the devices for PLDLA by means of histological evaluations during the period of consolidation of the fracture showed the efficiency of plate and screw system, and it was possible to check formation of bone tissue at the implantation site, without the presence of inflammatory reactionO copolímero poli(L-co-D,L ácido lático), PLDLA, tem ganhado destaque no campo das próteses temporárias, em virtude de seu tempo de degradação ser bastante compatível com o requisitado no caso de fraturas ósseas. Neste trabalho estudou-se a degradação in vivo de dispositivos do copolímero PLDLA, na forma de um sistema de placas e parafusos, empregado na fixação interna da tíbia de coelhos. Os dispositivos foram implantados em 15 coelhos adultos, albinos, da raça Nova Zelândia. Foram utilizados como controle dispositivos a base de ligas de titânio. (Ti-6Al-4V/Grau V) A aplicação de copolímeros do poli (L-co-D, lácido lático), sintetizado em laboratório, foi testada no reparo de fratura em tíbias de coelhos, sendo avaliado nos seguintes tempos: 2 semanas, 2 meses e 3 meses. A análise morfológica do tecido circunjacente ao sistema placa e parafuso PLDLA, referente a 2 semanas do implante, mostra a presença de osteoblastos, indicando uma pré formação óssea. Após 2 meses verifica-se neoformação óssea na região em contato com o polímero. Esse crescimento ósseo ocorre simultaneamente ao processo de degradação do PLDLA, invadindo a região onde havia o polímero e após 3 meses verifica-se uma intensa degradação do copolímero PLDLA e conseqüentemente uma maior invasão tecidual comparado a 2 meses, sendo caracterizado uma formação óssea na região em que o polímero degradou. O estudo da degradação in vivo dos dispositivos de PLDLA, por meio das avaliações histológicas durante o período de consolidação da fratura, mostrou a eficiência deste sistema placa e parafuso, sendo possível verificar formação de tecido ósseo no local do implante, sem a presença de reação inflamatória.1070107

Mechanical Properties Of Membranes Of Poly(l-co-dl-lactic Acid) With Poly(caprolactone Triol) And Study In Vivo

There is increasing interest in aliphatic polyesters from lactones and lactides because of their biodegradability and biocompatibility. Among these compounds, poly(lactide), and poly(glycolide), poly(ε -caprolactone) and their copolymers are especially interesting because of their potential applications as biomedical materials. The aim of this study was to examine the properties of membranes of poly(L-co-D,L lactic acid) (PLDLA) with poly(caprolactone triol) (PCL-T) obtained by solvent evaporation. The blends were characterized by differential scanning calorimetry, dynamic mechanical analysis, Fourier transform infrared spectroscopy, and tensile strength tests. Based on the results of in vitro studies, PLDLA/PCL-T blends of 100/0 and 90/10 were implanted in subcutaneous tissue of Wistar rats for 1, 3, 7, 15, and 60 days to evaluate their biocompatibility. Histological analysis indicated that, although PCL-T-containing membranes caused a more prominent inflammatory reaction in the initial time intervals, by 60 days after implantation, the material was surrounded by dense, organized collagen with almost no inflammatory infiltrate.2014Navarro, M., Michiardi, A., Castaño, O., Planell, J.A., Biomaterials in orthopaedics (2008) Journal of the Royal Society Interface, 5 (27), pp. 1137-1158Lehle, K., Lohn, S., Reinerth, G., Schubert, T., Preuner, J.G., Birnbaum, D.E., Cytological evaluation of the tissue-implant reaction associated with subcutaneous implantation of polymers coated with titaniumcarboxonitride in vivo (2004) Biomaterials, 25 (24), pp. 5457-5466Kim, D., Vaccaro, A., Fessler, R.G., (2005) Spinal Instrumentation, , chapter 37, Thieme Medical, New York, NY, USAWiley, New York, NY, USAKluger, P.J., Wyrwa, R., Weisser, J., Electrospun poly(D/Llactide- co-L-lactide) hybridmatrix: A novel scaffoldmaterial for soft tissue engineering (2010) Journal of Materials Science: Materials in Medicine, 21 (9), pp. 2665-2671Maluf-Meiken, L.C.V., Silva, D.R.M., Duek, E.A.R., Alberto-Rincon, M.C., Morphometrical analysis of multinucleated giant cells in subdermal implants of poly-lactic acid in rats (2006) Journal of Materials Science: Materials in Medicine, 17 (5), pp. 481-485Motta, A.C., Duek, E.A.R., Synthesis and characterization of the copolymer poly (L-co-D, L lactic acid) (2007) Polímeros, 17 (2), pp. 123-129Wu, S., Butt, H., Graf, K., Kappl, M., Physics and chemistry of interfaces (1971) Journal of Polymer Science Part C, 34, p. 19Meier, M.M., Kanis, L.A., De Lima, J.C., Pires, A.T.N., Soldi, V., Poly(caprolactone triol) as plasticizer agent for cellulose acetate films: Influence of the preparation procedure and plasticizer content on the physico-chemical properties (2004) Polymers for Advanced Technologies, 15 (10), pp. 593-600Pillin, I., Montrelay, N., Grohens, Y., Thermo-mechanical characterization of plasticized PLA: Is the miscibility the only significant factor? (2006) Polymer, 47 (13), pp. 4676-4682(2004) Polymer Handbook, , Wiley, Interscience, New York, NY, USA, 4th editionKim, W.N., Burns, C.M., Compatibility studies of blends of polycarbonate and poly(ethylene terephthalate) (1990) Journal of Polymer Science, Part B: Polymer Physics, 28 (9), pp. 1409-1429Menemse, K., Demiz, G., Synthesis, characterization and in vitro degradation of Poly(DL-Lactide)/Poly(DL-Lactide-co- Glycolide) (1993) Turkish Journal of Chemistry, 13, pp. 153-161Wan, Y., Yang, J., Yang, J., Bei, J., Wang, S., Cell adhesion on gaseous plasma modified poly-(L-lactide) surface under shear stress field (2003) Biomaterials, 24 (21), pp. 3757-3764Tezcaner, A., Bugra, K., Hasirci, V., Retinal pigment epithelium cell culture on surface modified poly(hydroxybutyrate-cohydroxyvalerate) thin films (2003) Biomaterials, 24 (25), pp. 4573-4583Lim, J.Y., Liu, X., Vogler, E.A., Donahue, H.J., Systematic variation in osteoblast adhesion and phenotype with substratum surface characteristics (2004) Journal of Biomedical Materials Research A, 68 (3), pp. 504-512Solhein, E., Sudmann, B., Bang, G., Sudmann, B., Biocompatibility and effect on osteogenesis of poly(ortho ester) compared to poly(DL-lactic acid) (2000) Journal of Biomedical Materials Research, 49 (2), pp. 257-263Kumar, V., Abbas, A.K., Fausto, N., Tissue renewal and repair: Regeneration healing, and fibrosis (2005) Robbins and Cotran Pathologic Basis of Disease, p. 110. , V. Kumar, A. K. Abbas, and N. Fausto, Eds. Elsevier, Saunders, Philadelphia, Pa, USA, 7th editio

Antibacterial activity of cerein 8A, a bacteriocin-like peptide produced by Bacillus cereus

The mode of action of cerein 8A, a bacteriocin produced by the soil bacterium Bacillus cereus 8A, was investigated. The effect of cerein 8A was tested against Listeria monocytogenes and a bactericidal effect at 400 arbitrary units (AU)/ml was observed. In addition, cerein 8A was bactericidal against Bacillus cereus at 200 AU/ml, and inhibited the growth of Escherichia coli and Salmonella Enteritidis. Stronger inhibition of these gram-negative bacteria was achieved when the chelating agent EDTA was added together with bacteriocin. The effect of cerein 8A on B. cereus and L. monocytogenes was also investigated by Fourier transform infrared spectroscopy (FTIR). Treated cells had an important frequency increase at 2920 cm–1 and a decrease at 1400 cm–1, corresponding to assignments of fatty acids. Transmission electron microscopy showed damaged cell walls and loss of protoplasmic material. These results suggest that the mode of action of cerein 8A is to interfere with cell membranes and the cell wall. [Int Microbiol 2005; 8(2):125-131

An overview of jets and outflows in stellar mass black holes

In this book chapter, we will briefly review the current empirical understanding of the relation between accretion state and and outflows in accreting stellar mass black holes. The focus will be on the empirical connections between X-ray states and relativistic (`radio') jets, although we are now also able to draw accretion disc winds into the picture in a systematic way. We will furthermore consider the latest attempts to measure/order jet power, and to compare it to other (potentially) measurable quantities, most importantly black hole spin.Comment: Accepted for publication in Space Science Reviews. Also to appear in the Space Sciences Series of ISSI - The Physics of Accretion on to Black Holes (Springer Publisher

The political nexus between water and economics in Brazil:A critique of recent policy reforms

The reform of water policies in Brazil has involved a combination of regulatory norms and economic-incentive instruments. Nonetheless, contrary to its formal objectives, the process has largely failed to prevent widespread environmental impacts and growing spatial and sectoral conflicts. The main reason for such failures is the perverse influence of market rationality, which is particularly evident in the reorganization of the public sector, the quantification of the monetary value of water, and the payment for environmental services