Investigation of the physicochemical and functional properties of poly(2-methacryloyloxyethyl phosphorylcholine)-conjugated aptamers

Abstract

Polymer conjugation is a common strategy to improve the pharmacokinetics of aptamers, yet its effects on aptamer properties are incompletely understood. Poly(ethylene glycol) (PEG) is the most widely used polymer for this purpose, but concerns about anti-PEG immune responses have prompted interest in alternative polymers. We previously reported that conjugation with the zwitterionic polymer poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) significantly prolongs the circulation time of a DNA aptamer while avoiding anti-PEG antibody recognition. In this study, we evaluated the physicochemical and functional consequences of PMPC conjugation of aptamers. Biophysical analyses suggested that the secondary structure and target-binding affinity of the aptamer were preserved, while functional consequences upon PMPC conjugation varied with the targets. The activity of a membrane receptor-targeting aptamer partially decreased, likely due to spatial constraints around the cell membrane, while RB005, targeting soluble activated coagulation factor IX, retained its full activity. In addition, PMPC conjugation significantly prolonged the in vivo plasma retention of RB005. By elucidating the effects of PMPC on aptamer properties and introducing another example that further supports the general applicability of PMPC conjugation in enhancing aptamer pharmacokinetics, these findings support PMPC as a promising alternative to PEG.