Avaliação in vitro de matrizes de PLGA com hormônio do crescimento recombinante humano : análise estrutural e dinâmica de liberação do hormônio

Abstract

Growth factors such as the recombinant human growth hormone are drawing attention on the field of bone reconstruction. However, due to the protein’s short half-life, biodegradable polymers, like PLGA, have been applied seeking a slower and controlled drug release for topical applications. Objective: To asses, in vitro, the behavior of PLGA matrices with 2 different rhGH concentrations. Materials and Methods: Three groups of triplicate samples were created: group I with pure PLGA (control), group II with PLGA loaded with a higher rhGH concentration and group III with PLGA loaded with a lower concentration of the hormone. Each group was analyzed macro and microscopically (SEM) and, by means of the hidrolitic degradation test, the dynamics of release of rhGH as well as the alterations on the pH of the incubation medium were evaluated, throughout 29 days. Results: Matrices from all groups showed indistinguishable macro and microscopic features. Group II released a higher quantity of rhGH, as expected, however there was no clear release pattern on both groups. rhGH release was observed until the 22° day and there was no statistically significant difference on weight loss between the 3 groups. pH values found were clinically viable. Conclusion: Morphological properties of the matrices must be assessed according to its applications and target-tissue to be substituted/regenerated and it was not possible to determine a pattern of rhGH distribution within PLGA matrices on this survey. The matrices can be used as rhGH carriers and were able to extend hormone release for a period of 22 days. Wheight loss showed equal patterns (statistically), despite the addition of rhGH to the polymer. The pH values were clinically viable and the reduction of rhGH concentrations on future researches should not be carried out using this methodology, possibly owing to limitations on screening with ultra-violet spectroscopy.