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

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

Preparation and characterization of poly (L-lactic acid) and poly(ethylene oxide) blends

Poly(L-lactic acid) (PLLA) and poly(ethylene oxide) (PEO) blends were prepared by mechanical mixture and fusion of homopolymers. Samples were submitted to in vitro degradation tests (immersion in a phosphate buffer solution with pH = 7.4 at 37 °C). Independently of the blend composition, PEO was dissolved after 14 days of immersion. As expected, after immersion, scanning electron microscopy showed that the blends were porous, contrary to the samples, which were not immersed in the buffer solution. Phase separation was not evident. Using differential scanning calorimetry, the melting points (Tm) of both PLLA and PEO crystalline fractions were observed and remained practically constant, indicating no miscibility. Thermogravimetry showed that the temperature where the main mass loss stage starts (Tonset), depended on the blend composition and period of immersion in the buffer. The blends and the PLLA homopolymer were implanted in defects produced in the tibias of rats. The blends were as biocompatible as the PLLA.117125Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Use Of Blends Bioabsorbable Poly(l-lactic Acid)/poly(hydroxybutyrate-co-hydroxyvalerate) As Surfaces For Vero Cell Culture

Vero cells, a cell line established from the kidney of the African green monkey (Cercopithecus aethiops), were cultured in F-10 Ham medium supplemented with 10% fetal calf serum at 37°C on membranes of poly(L-lactic acid) (PLLA), poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and their blends in different proportions (100/0, 60/40, 50/50, 40/60, and 0/100). The present study evaluated morphology of cells grown on different polymeric substrates after 24 h of culture by scanning electron microscopy. Cell adhesion was also analyzed after 2 h of inoculation. For cell growth evaluation, the cells were maintained in culture for 48, 120, 240, and 360 h. For cytochemical study, the cells were cultured for 120 or 240 h, fixed, processed for histological analysis, and stained with Toluidine blue, pH 4.0, and Xylidine ponceau, pH 2.5. Our results showed that cell adhesion was better when 60/40 and 50/50 blends were used although cells were able to grow and proliferate on all blends tested. When using PLLA/PHBV (50/50) slightly flattened cells were observed on porous and smooth areas. PLLA/PHBV (40/60) blends presented flattened cells on smooth areas. PLLA/PHBV (0/100), which presented no pores, also supported spreading cells interconnected by thin filaments. Histological sections showed that cells grew as a confluent monolayer on different substrates. Cytochemical analysis showed basophilic cells, indicating a large amount of RNA and proteins. Hence, we detected changes in cell morphology induced by alterations in blend proportions. 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Synthesis, Characterization And "in Vitro" Degradation Of Plla [síntese, Caracterização E Degradação "in Vitro" Do Poli(l-ácido Láctico)]

The study and application of bioreabsorbable polyesters to repair damaged tissues is a promising research area. Poly(L-lactic acid), PLLA, is the most important bioreabsorbable polyester due to it excellent biocompatibility and bioreabsorption. The aim of this work was to synthesize, characterize and evaluate the in vitro degradation process of PLLA membranes. The polymer was synthesized by ring opening of the cyclic diester of lactic acid using as catalyst Sn(Oct) 2. PLLA presented high values of molar mass (M̄ w around 105 g/mol) and its chemical structure was confirmed by RMN 1H, 13C and IR. The thermal properties of PLLA were studied by DSC, from which a high cristallinity degree was observed consistent with the literature. The in vitro degradation of PLLA membranes demonstrated that the crystallinity degree increased with increasing degradation times.1612632Shyamroy, S., (2003) Synthesis of Biodegradable Poly (Lactic Acid) Polymers, , Thesis doctor University of Poona, IndiaSchaldach, M., Cardiologia Cirúrgica Perspectivas Para o Ano (2000) Biomateriais-C3Fukuzaki, M., Yoshida, M., Asano, Kumakura, M., (1989) Eur. Polym. J., 25 (10), pp. 1019-1026Proikakis, C.S., Tarantili, P.A., Andreopoulos, A.G., Synthesis and Characterization of Low Molecular Weight Polylactic Acid (2002) Journal of Elastomers and Plastics, 34, pp. 49-63Ashammakhi, N., Peltoniemi, H., Waris, E., Developments in craniomaxilolfacial surgery: Use of self-reinforced bioabsorbable osteofixation devices (2001) Plastic and Reconstructive Surgery, 108, pp. 167-180Ashammakhi, N., Suuronen, R., Tiainen, J., Tormala, P., Waris, E., Spotligthy on naturally absorbable osteofixation devices (2003) Journal of Craniofacial Surgery, 14, pp. 247-259Rokkanen, P.U., Bostman, O., Hirvensalo, E., Bioabsorbable fixation in orthopaedic surgery and traumatology (2000) Biomaterials, 21, pp. 2607-2613Carothers, W.H., Borough, G.L., Natta, F.J.V., Studies of polymerization and ring formation X the reversible polymerization of six- Membered cyclic esters (1932) J.Am.Chem.Soc., 54, p. 761Kulkarni, R.K., Pani, K.C., Neuman, C., Leonard, F., Polylactid Acid for Surgical Implants (1966) Arch. Surg., 93, pp. 839-843Lunt, J., Large-scale production, properties and commercial applications of polylactic acid polymers (1998) Polym. Degrad. Stab, 59, pp. 145-152Bendix, D., Chemical synthesis of polylactide and its copolymers for medical applications (1998) Polym.Degrad. Stab, 59, pp. 129-135Gogolewski, S., Bioresorbable polymers in trauma and bone surgery (2000) Injury Int. J. Care Injured, 31, pp. S-D28-32Gupta, M.C., Deshmukh, V.G., Thermal oxidative degradation of poly-lactic acid partii:Molecular and eletronic spectra during isothermal heating (1982) Colloid Polymer Sci, 260, pp. 514-517Dubbis, C., Jacobs, R., Jerome, (1991) Macromolecules, 24, p. 2266. , PhD, ThesisHyon, S.H., Jamshidi, K., Ikada, Y., Synthesis of Polylactides with Different Molecular Weights (1997) Biomaterials, 18, pp. 1503-1508Kim, S., Kim, Y.H., (1999) Macromol. Sympo., 144, p. 277Nijenhuis, A.J., (1995) Synthesis and Properties of Lactide Polymers, , Thesis, NetherlandsDrumond, W.S., Wang, S.H., Síntese e Caracterização Do Copolimero Poliácido Lático-B-Glicol Etilênico, , Polimeros: Ciência e Tecnologia, 14,n 2, 74-79, (2004)Kricheldorf, H.R., Sumbél, M.V., (1988) Makromolek. Chem., 189, p. 317Woo, S.I., Kim, B.O., Jun, H.S., Chang, H.N., Polymerization of aqueous lactic acid to prepare high molecular weight poly(lactic acid) by chain-extending with hexamethylene diisocyanate (1995) Polymer Bulletin, 35, p. 415Hiltunen, K., Harkonen, M., Seppala, J.V., Vananen, T., Synthesis and Characterization of Lactic Acid Based Telechelic Prepolymers (1996) Macromolecules, 29, p. 8677Ferreira, B.M.P., Zavaglia, C.A.C., Duek, E.A.R., (2001) Mat. Res., 4, p. 34Moon, S.I., Lee, C.W., Taniguchi, I., Miyamoto, M., Kimura, Y., (2001) Polymer, 42, p. 5059Pistner, H., Gutwald, R., Ordung, R., Reutther, J., (1992) Poly (L-Lactide):A Long-Term Degradation Study in Vivo.Biomaterials, 14 (9), pp. 671-677Duek, A.R., Zavaglia, C.A.C., Belangero, W.D., Vitro study of poly (lactic acid) pin degradation (1999) Polymer, 40, pp. 6465-6473Tsuji, H., Ikada, Y., (2000) Polym. Degrad. and Stab., 67, p. 179Tsuji, H., Ikada, Y., (1997) J. Appl. Polym. Sci., 631, p. 85