Avaliação da degradação de matrizes poliméricas biodegradáveis (PLGA) associadas com hormônio do crescimento humano recombinante (RHGH) : estudo in vitro

Abstract

The PLGA is a bioabsorbable polymer derived from lactic and glycolic acids which has been used as drug release system . One of the drugs with the potential to use this type of vehicle is the recombinant human growth hormone (rhGH), because it has advantages such as speed up the bone integration process , bone maturation and remodeling around implants, in addition to stimulating osteogenesis. Objective: This study aims to evaluate the matrix degradation of PLGA and rhGH. Materials and Methods: 75:25 (Group I) and 50:50 (Group II): Two ratios of PLGA were used. The matrices were prepared by solvent evaporation technique as it follows: firstly, the PLGA was dissolved in dichloromethane and methanol and then it was mixed with a composed mixture of recombinant human growth hormone, zinc acetate, solution and deionized water. This mixture was poured into silicone circular shape moulds approximately 10 mm diameter which were placed in a solvent evaporation chamber at room temperature, where they were dried by nitrogen gas force action. The control samples were made just dissolving PLGA and pouring it into the silicone moulds. After the drying period, all the samples were weighed on a precision scale. Then, they were immersed in buffer solution and the hydrolytic degradation experiment was investigated and the samples remained for a predetermined period of time. After this process was finished, the solid sample portion was dried and weighed again. The supernatant went through pH analysis and later, by UV-visible absortion spectrophotometry analysis. Results:It was possible to calculate the concentration of rhGH released in the middle through the straight line obtained in a calibration curve.We observed that, from the first to the last day the released rhGH concentration in the medium was higher in Group II. The loss of mass percentage increased over the time in both groups. But this loss of mass was higher in group I compared to Group II. The pH showed a little variation over the time. The average was between 7.5 and 7.9. Conclusion:The matrices which were prepared with PLGA 50:50 showed the best results in relation to the ones prepared with PLGA 75:75.These are some advantages: easy handling, more uniform pores, less bubbles and the growth hormone was released slowly and gradually.