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Blends of poly(l-lactic acid)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PLLA/PHBV), both semicrystalline polymers, were prepared in different compositions (100/0, 80/20, 60/40, 50/50, 40/60, 20/80, and 0/100) and characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), polarized light microscopy (PLM), and tensile tests. Although PLLA/PHBV blends do not present clear phase separation by SEM, the analyses by TGA, DSC, and DMA showed that the PLLA/PHBV blends are immiscible. The cross sections observed by SEM showed that the morphology of the blends changes from porous to dense, due to the composition. DSC and DMA data showed two distinct glass transition and melting temperatures. However, the DMA analysis related to frequency variation showed partial molecular interactions between PHBV and PLLA.

The use of bioresorbable polymers as a support for culturing cells has received special attention as an alternative for the treatment of lesions and the loss of tissue. The aim of this work was to evaluate the degradation in cell culture medium of dense and porous scaffolds of poly(L-lactic acid) (PLLA) and poly(D,L-lactic acid-co-glycolic acid) (50:50) (PLGA50) prepared by casting. The adhesion and morphology of osteoblast cells on the surface of these polymers was evaluated. Thermal analyses were done by differential scanning calorimetry and thermogravimetric analysis and cell morphology was assessed by scanning electron microscopy. Autocatalysis was observed in PLGA50 samples because of the concentration of acid constituents in this material. Samples of PLLA showed no autocatalysis and hence no changes in their morphology, indicating that this polymer can be used as a structural support. Osteoblasts showed low adhesion to PLLA compared to PLGA50. The cell morphology on the surface of these materials was highly dispersed, which indicated a good interaction of the cells with the polymer substrate.

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The present study explored a new approach to the production of tubular conduits designed for peripheral nerve repair. Poly(L-lactic acid) (PLLA) and polycaprolactone (PCL) membranes were obtained after solvent evaporation and wrapped around a mandrel. The effectiveness of nerve regeneration was compared with that obtained with polyethylene and PCL extruded prostheses 30 and 60 days after surgery. The comparison between extruded and membrane-derived tubes clearly showed structural differences that were directly proportional to the hardness and transparency. An important factor to be considered is that the fiber count indicated that membrane-derived PCL tubes provided a significantly greater number of axons 30 days after repair. Sixty days after the procedure, the greatest regenerative performance was obtained with PCL, regardless of tube construction method. An intense imunolabeling of S100, type IV collagen, and laminin could be observed in the tissue obtained from membrane-derived PCL and PLLA groups, indicating that such constructs were able to positively stimulate Schwann cell responses. Overall, the results provided evidence that membrane-derived conduits are an alternative preparation method for tubular prostheses for peripheral nerve regeneration.

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The copolymers poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) are being intensely studied as a tissue engineering substrate. It is known that poly 3-hydroxybutyric acids (PHBs) and their copolymers are quite hydrophobic polyesters. Plasma-surface modification is an effective and economical surface treatment technique for many materials and of growing interest in biomedical engineering. In this study we investigate the advantages of oxygen and nitrogen plasma treatment to modify the PHBV surface to enable the acceleration of Vero cell adhesion and proliferation. PHBV was dissolved in methylene chloride at room temperature. The PHBV membranes were modified by oxygen or nitrogen-plasma treatments using a plasma generator. The membranes were sterilized by UV irradiation for 30 min and placed in 96-well plates. Vero cells were seeded onto the membranes and their proliferation onto the matrices was also determined by cytotoxicity and cell adhesion assay. After 2, 24, 48 and 120 h of incubation, growth of fibroblasts on matrices was observed by scanning electron microscopy (SEM). The analyses of the membranes indicated that the plasma treatment decreased the contact angle and increased the surface roughness; it also changed surface morphology, and consequently, enhanced the hydrophilic behavior of PHBV polymers. SEM analysis of Vero cells adhered to PHBV treated by plasma showed that the modified surface had allowed better cell attachment, spreading and growth than the untreated membrane. This combination of surface treatment and polymer chemistry is a valuable guide to prepare an appropriate surface for tissue engineering application.

O estudo e aplicação de poliésteres bioreabsorvíveis para reparar tecidos danificados tem se mostrado uma área de pesquisa muito promissora. Poli (L-ácido láctico), PLLA, se destaca dentre os poliésteres bioreabsorvíveis, em função de características como biocompatibilidade e bioreabsorção. No entanto, seu alto custo de importação limita a expansão de seus dispositivos no País. Os objetivos deste trabalho foram sintetizar, caracterizar e estudar a degradação in vitro de membranas de PLLA. O polímero foi sintetizado através da abertura do dímero cíclico do ácido láctico, utilizando-se como catalisador Sn(Oct)2. Obteve-se PLLA com altos valores de massa molar (Mw em torno de 10(5) g/mol) e sua estrutura química foi confirmada através de RMN de ¹H e 13C e IR. As propriedades térmicas do PLLA foram estudadas por DSC, sendo verificada uma alta cristalinidade para o material, o que está de acordo com a literatura. O estudo da degradação "in vitro" das membranas do PLLA mostrou um aumento do grau de cristalinidade em função do tempo de degradação.