Stabilization of monomeric
insulin is a primary requirement for preserving the efficacy of the final formulation. Degraded and/or aggregated
protein as well as the presence of any of the conventional
excipients can result in immunogenic or
anaphylactic reactions, and reduced bioavailability of the
protein drug. The aim of this work was to select novel
RNA-based stabilizers of bovine
insulin which would recognize and bind to the monomeric
protein and help retain its bioactivity.
RNA aptamers were selected by an in vitro selection method. They were screened for their ability to inhibit
insulin fibrillation using agitation as a stress condition. The in vitro activity of
insulin was determined by phosphorylation of downstream
proteins in the cell. In vivo bioactivity was determined in a diabetic rat model.
RNA aptamers, which bound to
insulin with very low dissociation constants and high specificity, were selected. These sequences were aligned and consensus regions were found. The RNA sequences had no effect on the signalling cascade initiated by
insulin. The bioactivity of
insulin, as measured by its ability to lower plasma
glucose level in a diabetic rat model, also remained unchanged.
RNA aptamers are a novel class of
protein stabilizers which have the ability to disrupt
protein-
protein interactions and hence inhibit
protein aggregation. Their non-toxic and non-immunogenic nature makes such formulations safe for use.