Molecular Mechanism of Improved Structural Integrity of Protein in Polymer Based Microsphere Delivery System
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- 作者：Sanjay Rawat ; Nandita Kohli ; C. Raman Suri ; Debendra K. Sahoo
- 刊名：Molecular Pharmaceutics
- 出版年：2012
- 出版时间：September 4, 2012
- 年：2012
- 卷：9
- 期：9
- 页码：2403-2414
- 全文大小：626K
- 年卷期：v.9,no.9(September 4, 2012)
- ISSN：1543-8392
文摘
Polymer-based delivery systems provide a promising alternative to multidose intake of many drugs/vaccines. Protein aggregation and inactivation, however, are major problems associated with the encapsulation of proteins in microspheres. With this in mind, we investigated the structural integrity of a model protein bovine serum albumin (BSA) released from poly(lactide-co-glycolide) (PLGA) based microspheres. BSA was encapsulated using solid-in-oil-in-water (S/O/W) double emulsification method with different mixtures of surfactants (carboxymethyl cellulose (CMC):Tween 20/CMC:Tween 80/Tween 20:Tween 80) and with or without polyethylene glycol (PEG). The morphology of BSA-loaded microspheres was analyzed using dynamic light scattering (DLS) and scanning electron microscopy (SEM). BSA released from lyophilized microspheres was evaluated for the structural, conformational and thermal stability by using various spectroscopic and calorimetric techniques. Conformational analysis showed greater increase in secondary structural content of BSA in sample containing PEG and surfactant mixture of CMC and Tween 20 as compared to that containing other two mixtures of surfactants. The differential scanning calorimetric (DSC) analysis of released BSA from all PEG containing samples showed an increase in thermal stability of the protein. Furthermore, fluorescence spectra showed compactness of BSA. In conclusion our studies suggest macromolecular crowding, molecular confinement and increase in Gibbs free energy with strong electrostatic forces of repulsion between microspheres, the last phenomenon due to chosen surfactants, to be responsible for making the protein more compact and structurally integrated and result in a potential encapsulation process for improved protein integrity in final formulation.