Preparation of protein-loaded PEG-PLA micelles and the effects of ultrasonication on particle size

Poly(ethylene glycol)-poly(D,L-lactide) (PEG-PLA), a type of copolymer widely used for drug delivery, was synthesized in the present work based on previous studies, which is used for bovine serum albumin (BSA)-loaded micelle formulation. The micelles exhibited less than 100 nm in size with narrow polydispersity indices (PDI) of smaller than 0.3, and showed an encapsulation efficiency of 69%. BSA was encapsulated in the PEG-PLA micelle successfully exhibiting intact structure indicated by native polyacrylamide gel electrophoresis (Native-PAGE), fluorescence spectroscopy and fourier transform infrared spectroscopy (FTIR) analysis methods. It investigated the effects of freeze-drying, varying amount of cryoprotectants (sucrose, mannitol and lactose), and ultrasonication treatment on the size, and size distribution. The micelles were agglomerated in the freeze-drying process demonstrated by transmission electron microscope (TEM) and dynamic light scattering (DLS) analysis. Five percent of mannitol and ultrasonication for 90 s were found producing a significant reduction in agglomeration as well as a sharp decrease in size. The results demonstrated suitable cryoprotectant, and ultrasonication are beneficial to control the size and distribution of protein-loaded PEG-PLA micelle.