Adriana Cristina Motta

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 (Mw 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.

Síntese e caracterização do copolímero poli (L-co-D,L Ácido Láctico)

Bioreabsorbable polymers are routinely used as temporary prostheses for fractured bones. Among the bioreabsorbable polymers the poly(L-co-D, L lactic acid), PLDLA, in the 70:30 rate has been studied to obtain plates and screws to recuperate traumas in the cranium and maxilla facial regions. In this monomers rate, an amorphous polymer is obtained, which allows adaptation of devices in the local for the implant during the surgery. A limiting factor to use this polymer is its high cost, due to the importation process. In this work PLDLA was synthesized by mass polymerization of the cyclical monomers L-lactic acid and D, L lactic acid, using Sn(Oct)2 as catalyst. A material with high molar mass (105 g/mol) was obtained and characterized by 1H RMN, 13C RMN, GPC, FTIR and DSC.

Synthesis, Characterization, and Osteoblastic Cell Culture of Poly(L-co-D,L-lactide-co-trimethylene carbonate) Scaffolds

Lactide-based polymers have been widely investigated as materials for tissue engineering. However, characteristics such as low flexibility and elongation tend to limit particular applications, although these can be enhanced by adding plasticizers such as trimethylene carbonate (TMC) to the polymer chain of the copolymer poly(L-lactide-co-D,L-lactide) (PLDLA). The aim of this work was to synthesize and characterize a terpolymer of L-lactide, D,L-lactide, and TMC. The polymers were synthesized from 30% TMC by bulk polymerization and resulted in an average molar mass >105 g/mol. Thermal investigation of PLDLA-TMC showed a decrease in the glass transition and onset temperatures compared to PLDLA. PLDLA-TMC scaffolds stimulated the proliferation and normal phenotypic manifestations of cultured osteoblasts. These results show that it was possible to produce a terpolymer from L-lactide, D,L-lactide, and TMC. Scaffolds of this terpolymer had important characteristics that could be useful for applications in bone tissue engineering.

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(-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.

In vitro and in vivo cell tracking of PKH26-labeled osteoblasts cultured on PLDLA scaffolds

The importance of monitoring in vivo interaction that occurs between cells /bio/tissue recipient in the understanding of tissue regeneration processes becomes ever greater. This study aims to monitor and evaluate the influence of scaffold implants of poly (L-co-D, L lactic acid) PLDLA synthesized in the laboratory, previously cultured with primary osteoblastic cells heterologously stained with the fluorescent vital dye, PKH26, on the tissue regeneration process in 8 mm central critical defects of the Wistar rat calvaria. The results obtained by MTT assay and monitoring of cells stained with PKH26 dye over 14 days of culture showed that the dye was cytocompatible with osteoblastic cells and did not exert a negative influence on the growth of unstained cells. In the in vivo study, macroscopic observations made during deployment times corroborate the results in vitro, as no apparent signs of toxicity were observed in the implanted bone defect area. The use of mobile monitoring with the dye, PKH26 in vivo is an effective strategy for the understanding of cell behaviour in the presence of PLDLA polymer.

Development of a membrane of poly (L-co-D,L lactic acid-co-trimethylene carbonate) with aloe vera: An alternative biomaterial designed to improve skin healing:

The search for new therapies and drugs that act as topical agents to relieve pain and control the infectious processes in burns always attracted interest in clinical trials. As an alternative to synthetic drugs, the use of natural extracts is useful in the development of new strategies and formulations for improving the life quality. The aim of this study was to develop a wound dressing using Poly(L-co-D,L lactic acid-co-TMC) (PLDLA-co-TMC) containing aloe vera (AV). This natural plant extract is known for its modulatory effects under healing process. The membrane of PLDLA-co-TMC+aloe vera was prepared at different concentrations of AV (5, 10, 15 and 50%). The FTIR showed no change in the PLDLA-co-TMC spectrum after AV addition, while the swelling test showed changes only in PLDLA-co-TMC+AV at 50%. The wettability measurements showed decrease in the contact angle in all samples after the AV addition in the polymer, while the AV release test showed that PLDLA-co-TMC+50%AV sample has higher AV release rate than the sample with other AV concentrations. The SEM analysis showed that AV was homogeneously distributed at 5% only. Tensile tests demonstrated an increase in the Youngs modulus and a reduction in the elongation till rupture of the PLDLA-co-TMC after the addition of AV. Biocompatibility in vitro evaluation with fibroblast cells seeded in the membranes of PLDLA-co-TMC+AV showed that the cells were able to adhere, proliferate and maintain mitochondrial activity in all AV concentrations tested. Due to the known skin medicinal properties attributed to AV and the results here obtained, we suggest that after in vivo trials, the PLDLA-co-TMC+AV should be a promising biomaterial for application as a device for skin curative and healing agent.