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Updated: May 19, 2026
Preparation and Characterization of Individual and Multi-drug Loaded Physically Entrapped Polymeric Micelles
Published on: August 28, 2015
Microcosmic mechanisms for protein incomplete release and stability of various amphiphilic mPEG-PLA microspheres
Yi Wei1, Yu Xia Wang, Wei Wang
1National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, PR China.
Abstract:
The microcosmic mechanisms of protein (recombinant human growth hormone, rhGH) incomplete release and stability from amphiphilic poly(monomethoxypolyethylene glycol-co-D,L-lactide) (mPEG-PLA, PELA) microspheres were investigated. 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. The morphology, rhGH encapsulation efficiency, in vitro release profile, and rhGH stability of PELA microspheres during the release were characterized and compared in detail. 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 microcosmic mechanism of incomplete release by measuring the hydrophilicity of the PELA film and its interaction with rhGH. 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 PELA hydrophilicity played an important role in rhGH incomplete release and stability. Thus, the selection of suitable hydrophilic polymers with adequate PEG lengths is critical in the preparation of optimum protein drug sustained release systems. This present work is a first report elucidating the microcosmic mechanisms responsible for rhGH stability and its interaction with the microspheres. Importantly, this research demonstrated the application of promising new experimental methods in investigating the interaction between biomaterials and biomacromolecules, thus opening up a range of exciting potential applications in the biomedical field including drug delivery and tissue regeneration.
Insights
Investigating poly(monomethoxypolyethylene glycol-co-D,L-lactide) (mPEG-PLA) microspheres revealed that increasing poly(D,L-lactide) content enhanced protein encapsulation but reduced recombinant human growth hormone (rhGH) release and stability. PELA hydrophilicity is key for drug delivery systems.
Area of Science:
- Biomaterials Science
- Drug Delivery Systems
- Protein Chemistry
Background:
- Amphiphilic poly(monomethoxypolyethylene glycol-co-D,L-lactide) (mPEG-PLA, PELA) microspheres are used for protein delivery.
- Understanding protein release and stability mechanisms is crucial for optimizing drug delivery systems.
Purpose of the Study:
- To investigate the microcosmic mechanisms of recombinant human growth hormone (rhGH) incomplete release and stability from PELA microspheres.
- To elucidate the role of PELA hydrophilicity in rhGH release kinetics and stability.
Main Methods:
- Preparation of PELA microspheres with varying mPEG/PLA ratios using double emulsion and premix membrane emulsification.
- Characterization of morphology, encapsulation efficiency, in vitro release, and rhGH stability.
- Combined use of contact angle, AFM, and QCM-D to study PELA film hydrophilicity and rhGH interaction.
- Monitoring of microsphere microenvironment pH using CLSM with a pH-sensitive dye.
Main Results:
- Increased PLA content enhanced rhGH encapsulation efficiency but decreased release rate and stability.
- PELA hydrophilicity was identified as a critical factor influencing rhGH incomplete release and stability.
- New experimental methods were successfully applied to study biomaterial-biomacromolecule interactions.
Conclusions:
- The hydrophilicity of PELA microspheres significantly impacts rhGH stability and release.
- Optimizing PEG length in hydrophilic polymers is essential for effective protein drug sustained release systems.
- This research provides insights into protein-drug interactions within microspheres, with potential applications in biomedicine.
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