Amphiphilic polymer poly(monomethoxypolyethylene glycol-co-d,l-lactide) (mPEG-PLA, PELA), as a biomaterial, was widely utilized to improve the protein encapsulation efficiency in microspheres and decrease the burst release of protein from microspheres. Although PELA exhibits many advantages, its degree of hydrophilicity greatly effects protein drug release and stability profiles.Therefore, it is desirable to explore the mechanisms on a microcosmic level.

Researchers with Institute of Process Engineering (IPE) investigated the microcosmic mechanisms for protein incomplete release and stability profiles from amphiphilic copolymer PELA with various hydrophilic properties in detail.

In their work, PELA with different hydrophilicities (PELA-1, PELA-2, and PELA-3) based on various ratios of mPEG to PLA were employed to prepare microspheres exhibiting a narrow size distribution using a combined double emulsion and premix membrane emulsification method. It was found that increasing amounts of PLA enhanced the encapsulation efficiency of PELA microspheres but reduced both the release rate of rhGH and its stability.

Contact angle, atomic force microscope (AFM), and quartz crystal microbalance with dissipation (QCM-D) techniques were first combined to elucidate the mechanism on a microcosmic level. In addition, the pH change within the microsphere microenvironment was monitored by confocal laser scanning microscopy (CLSM) employing a pH-sensitive dye, which clarified the stability of rhGH during the release.

These results suggested that the PELA hydrophilicity played an important role in protein incomplete release and stability, thus offering an alternative to adjust these key parameters in the preparation of successful sustained protein formulations. This work also demonstrated the utility of several novel methods in the investigation of potential interactions between biomaterials and biomacromolecules, thus opening up a range of exciting potential applications in the biomedical field including drug delivery and tissue regeneration.

The paper was published in ACS Publications.