O 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.

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 reaction

Os inúmeros artigos científicos aplicando polímeros biorreabsorvíveis como biomaterial, desde 1966, mostram o crescente interesse dos pesquisadores em várias partes do mundo devido a sua ampla gama de aplicações na área médica, tais como regeneração guiada de tecidos, liberação controlada de drogas, suporte para cultura de células, implantes ortopédicos, entre outros. Com o intuito de analisar histologicamente a blenda PLLA/PCL poli(ácido- lático/poli(ε - caprolactona) na composição 70/30 com 3% de plastificante para aplicação como prótese de menisco, foi realizado um estudo in vivo em coelhos, os quais foram submetidos à remoção total do menisco medial do joelho, sendo que em um dos joelhos foi implantada a prótese da blenda e o outro, sem implante, serviu como controle. Após 8, 16 e 24 semanas, foram recolhidos deles, a prótese juntamente com o tecido ao seu redor, o côndilo femural da prótese e o côndilo femural controle. Os materiais foram submetidos à análise histológica por microscopia óptica. Os resultados mostraram que após 24 semanas, ocorreu a formação de um tecido do tipo fibrocartilagem, indicando que a blenda estudada apresenta grande potencial para ser utilizada para aplicação em questão, já que o material favorece a formação de um tecido muito semelhante ao do menisco.

The numerous scientific papers applying bioreabsorbable polymers as biomaterial, since 1966, shows the growing interest of researchers in various parts of the world due to its wide range of applications in medicine, such as guided tissue regeneration, controlled release of drugs, support for cells culture, orthopaedic implants, among others. In order to analyze the histologically PLLA / PCL poly (lactic-acid / poly ( caprolactone) blends composition 70/30 with 3% of plasticizer for application as a meniscal prothesis, a study was performed in vivo in rabbits, which were subjected to total removal of the medial meniscus of the knee, and in one of the knees was implanted in the prosthesis and blend another without implant, served as control. after 8, 16 and 24 weeks, were collected them, along with a prosthesis the tissue around it, the femoral condyle of the prosthesis and the femoral condyle control. The materials were subjected to histological analysis by optical microscopy. The results showed that after 24 weeks, there was the formation of a tissue-type fibrocartilage, indicating that the blend studied presents great potential to be used for application in question, since the material promotes the tissue formation o very similar to the meniscus.

O copolímero poli (L-co-DL ácido lático), PLDLA, tem se destacado no campo das próteses temporárias, porque o seu tempo de degradação é bastante compatível com aquele requerido no caso de fraturas ósseas. Neste trabalho, estudou-se a degradação "in vitro" de dispositivos processados na forma de placas do copolímero PLDLA sintetizado em laboratório. As placas do PLDLA foram imersas numa solução tampão fosfato (pH = 7,4) em um banho termostatizado a 37 ºC ± 1ºC, durante especificados períodos (0, 2, 4, 8, 16, e 30 semanas), e avaliadas pelas seguintes técnicas: cromatografia de permeação em gel (GPC), calorimetria diferencial de varredura (DSC), microscopia eletrônica de varredura (MEV) e ensaios de flexão por três pontos. Foi observado, através do estudo "in vitro", que o processo de degradação afeta a massa molecular desde a segunda semana de estudo. As análises das curvas de DSC demonstram que o material, inicialmente amorfo, apresenta vestígios de cristalinidade durante o processo de degradação, enquanto que as análises de TGA demonstram que a estabilidade térmica do copolímero só é afetada após 16 semanas de estudo. A análise por meio de MEV mostrou que o dispositivo passa de denso para poroso após 18 semanas de estudo "in vitro". O ensaio de resistência à flexão mostrou que o copolímero consegue reter mais de 80 % de sua resistência após período de 4 meses de imersão, um resultado bastante compatível com aquele requerido para consolidação óssea.

The poly (L-co-DL lactic acid) copolymer, PLDLA, has achieved outstanding position in the temporary prostheses because its degradation life is up to goog extent compatible with the requirement for the bone fracture repair. In vitro degradation of the in- Lab synthesized PLDLA was studied. The PLDLA plates were immersed in a phosphate buffer solution with pH = 7,4 at 37ºC +- 1º C provided by a thermostat controlled bath for specified test times (2, 4, 8, 16 and 30 weeks) and evaluated by using the following techniques: gel permeation chromatography (GPC), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and three point flexural strength test. From in vitro test, it was found that change in the PLDLA molecular weight due to its degradation is already noticeable since the second test-week. The initially amorphous PLDLA presented traces of cristalline signs according to DSC curves, while the thermal stability of the copolymer is affected only after 16 test-weeks as shown by TGA results. The change of PLDLA pieces from dense to porous took 18 in-vitro test-weeks as revealed by SEM. After four test months, PLDLA was capable of retaining more than 80% of its original three-point flexural strengh, which is up to good extent compatible with the requirements for bone consolidation.

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.

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.

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. This suggests that the cells changed their differentiation pattern when on various PLLA/PHBV blend surfaces.

Biocompatible and biodegradable polymers have been studied in the last few years with good clinical success in the fixation and stabilization of bone fractures. The understanding and the control of the polymeric prosthetic degradation process and the effect of its degradation products in the organism are crucial for the success of the implant. In this present work, blends of PLLA/PHBV, obtained in several compositions by casting of solvent, obtaining samples in the form of films. The samples were characterized by the analysis of TGA, DSC, DMA and SEM. The results obtained showed that the PLLA/PHBV blends are immiscible, and present a discrete separation by microscopy. The blends obtained showed porous fracture surfaces. It is noticed that PLLA begins its degradation in a few weeks (around 2 weeks), unlike PHBV, where it was possible to observe eventual degradation up to 53 weeks. It was also observed that the blend increased its crystallinity with degradation.

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.