RESUMEN
PURPOSE: The extraction of proteins from PLGA/PLA microspheres by a two-immiscible liquid phases system with the addition of surfactants was investigated. METHODS: First, the extraction without surfactants and the interaction between proteins (IFN-α2b and EGF) and empty microspheres (PLGA or PLA) was studied. Next, proteins stability in presence of different surfactants was evaluated by: (1) bicinchoninic acid protein assay, (2) reversed phase-high performance liquid chromatography, and (3) enzyme-linked immunosorbent assay. Then, proteins were extracted with PBS/dichloromethane including selected surfactants and characterized by the above mentioned techniques, biological activity tests, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrospray ionization mass spectrometry. RESULTS: Without surfactants, protein recovery was only 27-43% for IFN-α2b and 58-73% for EGF. Protein content in solutions incubated with blank microspheres decreased to 66% for IFN-α2b and 86% for EGF. It was only possible to quantify the EGF and IFN-α2b in the same manner as in PBS alone when the surfactant added was Pluronic F-68 and SDS, respectively. Addition of these surfactants allowed the complete isolation of both biomolecules from the microspheres. The extraction procedure did not affect the encapsulated proteins. CONCLUSION: Proteins can be quantitatively extracted, without changes, from PLGA/PLA microspheres using PBS/dichloromethane system that include an appropriate surfactant.