Release of FITC-BSA from poly(l-lactic acid) microspheres analysis using flow cytometry

In this investigation, biodegradable polymer poly(l-lactic acid) (PLA) microspheres were prepared by the W1/O/W2 solvent evaporation method. The inner phase was aqueous solution (W1) that contained bovine serum albumin that was labeled with fluorescein isothiocyanate (FITC-BSA). PLA was dissolved in chloroform with emulsifier sorbitan monooleate (span 80) as the dispersed phase (O). These two solutions (W1/O) were emulsified by a homogenizer to form a primary emulsion. Polyvinyl alcohol (PVA) used as surfactant, was applied in the formation of microspheres (W2). 0.5% (w/v) PLA was stirred at 3000 rpm using a homogenizer. Microspheres with sizes of up to around 10 μm were produced. These microspheres were separated by the glycerol gradient method, and take microspheres at part of 25% glycerol gradient concentration was analyzed by flow cytometry, indicating a more homogeneous particle size distribution than that not separated. The microspheres were degraded using several enzymes, and around 40% was degraded by 72 h. This result reveals the effectiveness of drug delivery by PLA microspheres, which was evaluated by performing a drug release test and flow cytometric analysis. The FITC-BSA concentration in the supernatant increased with the experimental time. At the phagocytosis experiments, encapsulated with FITC-BSA drug of microspheres can be used by the cell, as particle size approximately 1 μm.