Evaluation of sucrose esters as alternative surfactants in microencapsulation of proteins by the solvent evaporation method.

Sucrose esters (SE) are surfactants with potential pharmaceutical applications because of their low toxicity, biocompatibility, and excellent biodegradability. The objective of the study was to investigate SE as alternative surfactants in stabilizing emulsions for the preparation of protein-loaded microparticles. To achieve this goal, using bovine serum albumin as model protein and 75/25 poly(d,l-lactide-co-glycolide) as polymer carrier, we have investigated the influence of the following formulation variables on particle characteristics: (1) SE concentration from 0.01% to 1% (wt/vol), (2) hydrophile-lipophile balance (HLB) value of SE from 6 to 15, and (3) the nature of emulsion stabilizer. The formulations were characterized using ATR-FTIR spectroscopy, bicinchoninic acid protein assay, optical microscopy and SDS-PAGE. Results showed that at 0.05% (wt/vol) surfactant concentration, SE with HLB of 6 to 15 provided discrete and spherical microparticles with the highest encapsulation efficiency compared with controls polyvinyl alcohol (PVA) and poloxamer 188. These results may be explained by the difference in critical micelle concentration, diffusion, and partition coefficient among the tested surfactants. HLB values were consistent with SE spectral data. The protein molecular weight was preserved after the encapsulation process. The effective SE concentration was far less (20- to 200-fold) than that is usually required for PVA in microencapsulation of proteins. However, the encapsulation efficiency was relatively lower (approximately 13.5%). These preliminary results suggest that it may be desirable to optimize such formulations in vitro and in vivo for SE to be eventually used as alternative surfactants in the development of microparticulate systems for parenteral delivery of protein and gene medicines.