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Stabilization of proteins encapsulated in injectable poly (lactide- co-glycolide)

Nature Biotechnology volume 18, pages 52–57 (2000)Cite this article

Abstract

Controlled release from biodegradable polymers is a novel approach to replace daily painful injections of protein drugs. A major obstacle to development of these polymers is the need to retain the structure and biological activity of encapsulated proteins during months of incubation under physiological conditions. We encapsulated bovine serum albumin (BSA) in injectable poly(DL-lactide- co-glycolide) (PLGA) 50/50 cylindrical implants and determined the mechanism of BSA instability. Simulations of the polymer microclimate revealed that moisture and acidic pH (<3) triggered unfolding of encapsulated BSA, resulting in peptide bond hydrolysis and noncovalent aggregation. To neutralize the acids liberated by the biodegradable lactic/glycolic acid-based polyester, we coincorporated into the polymer an antacid, Mg(OH)2, which increased microclimate pH and prevented BSA structural losses and aggregation for over one month. We successfully applied this stabilization approach in both cylinder- and microsphere-injectable configurations and for delivery of angiogenic basic fibroblast growth factor and bone-regenerating bone morphogenetic protein-2.

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Figure 1: Effect of Mg(OH)2 content on BSA release kinetics (A) and encapsulated BSA aggregation kinetics (B) during incubation of the PLGA implants at 37°C in PBST.
Figure 2: Structural analyses of BSA from incubated PLGA millicylinders by SDS–PAGE (A), IEF (B), CD spectra (C), and fluorescence emission spectra (D).
Figure 3: (A) Controlled release of bFGF.

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Acknowledgements

We thank Dr. John Wang of Synzyme Technologies (Irvine, CA) for his helpful suggestions. We are very grateful to Prof. Mark Coggeshall, from the Department of Microbiology of the Ohio State University for his help in the bFGF bioassay experiment. We thank Dr. Hanne Bentz from Orthogene and Prof. Jeffrey Hubbell from the Swiss Federal Technology Institute for their aid in the BMP-2 studies. We also thank Professor Gary Means from the Department of Biochemistry, and Dr. Jichao Kang of the College of Pharmacy at the Ohio State University for their helpful discussions and technical assistance, respectively. This work was supported by NIH DE 12183 and a PhRMA grant to S.P.S.

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  1. Gaozhong Zhu

    Present address: Department of Pharmaceutical Science and Technology, Biogen Inc., 14 Cambridge Center, Cambridge, MA, 02142

Authors and Affiliations

  1. Colleges of Pharmacy, The Ohio State University, Columbus, 43210, OH

    Gaozhong Zhu & Steven P. Schwendeman

  2. Colleges of Dentistry, The Ohio State University, Columbus, 43210, OH

    Susan R. Mallery

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Correspondence to Steven P. Schwendeman.

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Zhu, G., Mallery, S. & Schwendeman, S. Stabilization of proteins encapsulated in injectable poly (lactide- co-glycolide). Nat Biotechnol 18, 52–57 (2000). https://doi.org/10.1038/71916

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