Lack of a synergistic effect of arginine–glutamic acid on the physical stability of spray-dried bovine serum albumin

Abstract

Improving the physical stability of spray-dried proteins is essential for enabling pulmonary delivery of biotherapeutics as a noninvasive alternative to injections. Recently, a novel combination of two amino acids – l-arginine (l-Arg) and l-glutamic acid (l-Glu), has been reported to have synergistic protein-stabilizing effects on various protein solutions. Using spray-dried bovine serum albumin (BSA) reconstituted in solution as a model protein, we investigated the synergistic effect of these amino acids on the physical stability of proteins. Five BSA solutions were prepared: (1) BSA with no amino acids (control); (2) with 50 mM l-Arg; (3) with 200 mM l-Arg, (4) with 50 mM l-Glu and (5) with 25:25 mM of Arg:Glu. All solutions were spray-dried and accelerated studies at high temperatures were performed. Following accelerated studies, monomer BSA loss was measured using SE-HPLC. We found that l-Arg significantly improved the physical stability of spray-dried BSA even at low concentrations, however, when combined with l-Glu, was ineffective at reducing monomer BSA loss. Our findings demonstrate the limitations in using Arg–Glu for the stabilization of spray-dried BSA. Furthermore, we found that a low concentration of l-Glu enhanced monomer BSA loss. These findings may have significant implications on the design of future biotherapeutic formulations.

Keywords:

• Amino acids
• excipients
• physical stability
• protein aggregation
• spray-drying

Acknowledgements

The authors would like to acknowledge Dr. Nial Wheate for critical reading of the manuscript and the Faculty of Pharmacy for financial support.

Disclosure statement

The authors declare no financial or commercial declarations of interest.