Eliana Aparecida de Rezende Duek

PLDLA/PCL-T Scaffold for Meniscus Tissue Engineering

Abstract The inability of the avascular region of the meniscus to regenerate has led to the use of tissue engineering to treat meniscal injuries. The aim of this study was to evaluate the ability of fibrochondrocytes preseeded on PLDLA/PCL-T [poly(L-co-D,L-lactic acid)/poly(caprolactone-triol)] scaffolds to stimulate regeneration of the whole meniscus. Porous PLDLA/PCL-T (90/10) scaffolds were obtained by solvent casting and particulate leaching. Compressive modulus of 9.5±1.0 MPa and maximum stress of 4.7±0.9 MPa were evaluated. Fibrochondrocytes from rabbit menisci were isolated, seeded directly on the scaffolds, and cultured for 21 days. New Zealand rabbits underwent total meniscectomy, after which implants consisting of cell-free scaffolds or cell-seeded scaffolds were introduced into the medial knee meniscus; the negative control group consisted of rabbits that received no implant. Macroscopic and histological evaluations of the neomeniscus were performed 12 and 24 weeks after implantation. The polymer scaffold implants adapted well to surrounding tissues, without apparent rejection, infection, or chronic inflammatory response. Fibrocartilaginous tissue with mature collagen fibers was observed predominantly in implants with seeded scaffolds compared to cell-free implants after 24 weeks. Similar results were not observed in the control group. Articular cartilage was preserved in the polymeric implants and showed higher chondrocyte cell number than the control group. These findings show that the PLDLA/PCL-T 90/10 scaffold has potential for orthopedic applications since this material allowed the formation of fibrocartilaginous tissue, a structure of crucial importance for repairing injuries to joints, including replacement of the meniscus and the protection of articular cartilage from degeneration.

Films of poly (L - lactic acid) / poly(hydroxybutyrate-co-hydroxyvalerate) blends: in vitro degradation

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.

Blendas biodegradáveis de poli(3-hidroxibutirato)/poli(e-caprolactona): obtenção e estudo da miscibilidade

Due to its biodegradability, poly(3-hydroxybutyrate) P(3-HB) has attracted much attention in the environmental sector. However, some characteristics of this polymer, such as high crystallinity, poor processability and high brittleness, have lead several research groups to study polymeric blends in order to modify P(3-HB) properties. Poly(e-caprolactone) (PCL) is a synthetic polyester which is completely degraded after about one year when buried in soil. In general, it acts as a polymeric plasticizer lowering the elastic modulus and enhancing the processability of the blend. Blends of two biodegradable polymers, P(3-HB) and PCL have been prepared by casting in different compositions. Miscibility, thermal behavior and morphology of these blends were studied using modulated differential scanning calorimetry (MDSC), scanning electron microscopy (SEM) and polarizing light microscopy (PLM). The two glass transition temperatures, detected by MDSC, suggest the immiscibility of the system. Phase separation was confirmed by PLM.

Preparation and characterization of paclitaxel-loaded PLDLA microspheres

Paclitaxel (Taxol®), is a drug used to treat ovarian, breast, lung and bladder cancer. However, the low solubility of this drug in water is a major limitation in its clinical use. One strategy to overcome this limitation would be to encapsulate paclitaxel in polymeric microspheres that are biocompatible and can be used as drug carriers. The aim of this study was to use the bioresorbable, biocompatible copolymer poly-L-co-D,L-lactic acid (PLDLA) in the 70:30 rate to produce and characterize microspheres containing paclitaxel. The simple emulsion technique was used to obtain spherical microspheres that were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The average size of PLDLA microspheres without and with paclitaxel was 10.3µm ± 1.7 and 12.7 ± 1.3 µm, respectively, as determined by laser light scattering (LLS). Differential scanning calorimetry (DSC) showed that pure paclitaxel had an endothermic peak corresponding to a melting point of 220 °C, which indicated its crystalline nature. The same peak was observed in a physical mixture of PLDLA + paclitaxel in which both components were present in the same proportions used to prepare the microspheres . In contrast, this peak was not observed for the drug, indicating that paclitaxel did not crystallize in PLDLA microspheres. Differential scanning calorimetry (DSC) indicated that paclitaxel was homogeneously dispersed in the PLDLA microspheres, the incorporation of paclitaxel into the microspheres did not alter the thermal properties of PLDLA. The Fourier transform infrared spectroscopy (FTIR) analysis seems to indicate the absence of chemical interaction between polymer and drugs in microspheres and the presence of drugs as a molecular dispersion in the polymer matrix. The efficiency of paclitaxel encapsulation in PLDLA microspheres was 98.0± 0.3%, as assessed by high performance liquid chromatography (HPLC). A kinetic study of drug release

Synthesis and characterization of a novel terpolymer based on L-lactide, D,L-lactide and trimethylene carbonate

Terpolymers of L-lactide, D,L-lactide and trimethylene carbonate (TMC) were synthesized via the ring-opening polymerization reaction for cyclic monomers using stannous octoate as the initiator at a ratio of ~0.05 mol% (monomers/(SnOct)2). Synthesis was done at 130 oC for 48 h. The inclusion of TMC, an aliphatic elastomeric polycarbonate, alongside polymer chain segments containing L-lactide and D,L-lactide, was expected to yield a material with improved properties such as increased elongation; this would overcome the limitation of copolymers consisting entirely of lactide and D,L-lactide. The terpolymer properties were assessed by Nuclear magnetic resonance spectroscopy 1H and 13C NMR, infrared spectroscopy, differential scanning calorimetry and thermogravimetry, with particular attention being given to the effect of TMC on the copolymer of L-lactide-co-D,L-lactide. The mixing of these polymers resulted in material with a high molar mass (105 g/mol). The mechanical properties of the terpolymer were assessed using pins of this material that were tested by mechanical flexion at three points. When compared with results for the copolymer PLDLA there was a decrease in Youngs modulus for the TMC-containing terpolymer.

Benefits of oxygen and nitrogen plasma treatment in Vero cell affinity to poly(lactide-co-glycolide acid)

Cell adhesion on materials surface is critical because this phenomenon occurs before other events, as cell spreading, cell migration and cell differentiation. it is commonly accepted that the adhesion of cells on solid substrate is influenced by several substratum surface properties, such as wettability, surface charge, roughness and topography. plasma technique is a convenient method for modifying surface properties of materials without affecting physical properties. in this study, poly(lactide-co-glycolide), plga, membranes were modified by oxygen and nitrogen plasma to improve polymer hydrophilicity and verify their effect on vero cells culture. the plga membranes, which were characterized by sem and contact angle, showed increased surface rugosity and narrower contact angles. cell adhesion, cytotoxicity assay, sem and cytochemistry analysis showed that plasma treatment was beneficial to cell growth by improving cell-polymer interaction. Cell adhesion on materials surface is critical because this phenomenon occurs before other events, as cell spreading, cell migration and cell differentiation. It is commonly accepted that the adhesion of cells on solid substrate is influenced by several substratum surface properties, such as wettability, surface charge, roughness and topography. Plasma technique is a convenient method for modifying surface properties of materials without affecting physical properties. In this study, poly(lactide-co-glycolide), PLGA, membranes were modified by oxygen and nitrogen plasma to improve polymer hydrophilicity and verify their effect on Vero cells culture. The PLGA membranes, which were characterized by SEM and contact angle, showed increased surface rugosity and narrower contact angles. Cell adhesion, cytotoxicity assay, SEM and cytochemistry analysis showed that plasma treatment was beneficial to cell growth by improving cell-polymer interaction.

PLGA-Hydroxyapatite Composite Scaffolds for Osteoblastic-Like Cells

The aim of this work was to investigate the behaviour of rat calvarial osteoblastics cells on porous PLGA/HA composite scaffolds. Cells were submitted to cytotoxicity and cell adhesion assay. In addition, the cells morphology were observed by SEM, and the collagen synthesis measured by Sirius Red colorimetric method. The results showed that the material was not cytotoxic and hydroxyapatite improved cell adhesion. Osteoblastic cells could adhere and spread on the scaffolds as observed. After 14 days the presence of hydroxyapatite increased the synthesis of collagen. This study demonstrates that composite scaffolds presented better cellular responses compared to polymer scaffolds.

Efficacy of a combination of simvastatin and poly(DL-lactic-co-glycolic acid) in stimulating the regeneration of Bone Defects

The proper healing of bone defects requires a bone graft or bone substitute and synthetic materials have been developed as alternatives to autografts and allografts. Poly(DL-lactic-co-glycolic acid) (PLGA) is a synthetic polymer widely used for bone healing because of its biocompatibility and biodegradability. PLGA scaffolds have also been used in drug delivery devices, such as in combination with simvastatin, to stimulate bone growth. In this work, we examined the usefulness of a combination of PLGA with simvastatin for treating bone defects. For this, two defects were created in rat calvaria and in half of the animals the right sides were filled with PLGA scaffolds while the other half received PLGA plus simvastatin; the left sides remained empty. The rats were killed for histological analysis after four and eight weeks. There was a significant increase in the amount of bone formation in the treated lesions, particularly those that received PLGA plus simvastatin.

In vitro degradation of Poly-L-co-D, L-lactic acid membranes

Poly-L-co-D.L-lactic (PLDLA) is a bioresorbable polymer whose properties have been studied for degradation sensitivity and its application in medicine. In this study, the potential of PLDLA membranes for temporary implantation was evaluated. PLDLA membranes were prepared with the solvent evaporation technique and characterized by differential scanning calorimetry, gel permeation chromatography, thermogravimetric analysis, scanning electron microscopy and traction tests. The glass transition temperature of the membranes was 59 °C. Degradation started around 340 °C during the second week showing pores and fissures on the broken surface. Evident degradation was observed after 16 weeks. Microscopy showed that before degradation PLDLA membranes presented no pores. PLDLA properties of resistance to traction and elasticity module were maintained until the 8 th week, and after the 16 th week there was a sharp reduction of these properties due to degradation. PLDLA membranes present excellent potential as temporary implantation given their degradation characteristics.

The use of vancomycin-loaded poly-l-lactic acid and poly-ethylene oxide microspheres for bone repair: an in vivo study

OBJECTIVE: The aim of this study was to investigate bone repair after the implantation of vancomycin-loaded poly-L-lactic acid/poly-ethylene oxide microspheres compared with vancomycin-unloaded poly-L-lactic acid/poly-ethylene oxide microspheres. METHODS: Poly-L-lactic acid/poly-ethylene oxide microspheres were implanted in rat tibiae and evaluated for periods of 2, 4, 8, and 12 days and 4, 8, 16, and 32 weeks. The groups implanted with vancomycin-loaded and vancomycin-unloaded microspheres were compared. Histopathologic (semi-quantitative) and histomorphometric analyses were performed to evaluate the bone formation process. RESULTS: During the first period (second day), fibrin and hemorrhaging areas were observed to be replaced by granulation tissue around the microspheres. Woven bone formation with progressive maturation was observed. All of the histopathological findings, evaluated by a semi-quantitative assay and a quantitative analysis (percentage of bone formation), were similar between the two groups. CONCLUSION: Vancomycin-loaded poly-L-lactic acid/poly-ethylene oxide microspheres are a good bone substitute candidate for bone repair. Local antibiotic therapy using vancomycin-loaded poly-L-lactic acid/poly-ethylene oxide microspheres should be considered after the microbiological evaluation of its efficacy.