Conjugation of Biomolecules to PEG as a Strategy for Efficient Protein Aggregation Inhibition

Neurodegenerative diseases are a group of progressive disorders characterized by the degeneration of neurons with significant cognitive decline and motor and autonomic dysfunction. They are linked to protein aggregation that leads to cellular toxicity, neuronal death, and brain atrophy due to the accumulation of amyloid plaques and tau tangles in the brain. Recent advances in biomaterials have introduced several biocompatible polymers and conjugated biomolecules as potential inhibitors for protein aggregation. Conjugation to biocompatible polyethylene glycol (PEG) is the most widely used strategy for enhancing bioavailability, biocompatibility, and pharmacokinetic properties of small molecular drugs. In this work, we have designed and synthesized two biomolecule-polymer conjugates, namely, Tre-CA-mPEG and LA-CA-mPEG, by combining a biocompatible, nontoxic polymer monomethoxy PEG (mPEG), a steroid bile acid, cholic acid (CA), and a functional biomolecule, trehalose (Tre) or lipoic acid (LA). These building blocks have significant protein stabilization and neuroprotective attributes, which are important for protein aggregation inhibition. The size distributions of the self-assemblies formed by the Tre-CA-mPEG and LA-CA-mPEG bioconjugates were determined by dynamic light scattering (DLS) measurements. Both the PEGylated bioconjugate assemblies show promising results for inhibition of protein aggregation. The hydrophobic interactions provided predominantly by the steroidal core moiety, together with hydrogen bonding interactions within the PEG corona of the self-assemblies, play a crucial role in protein stabilization and fibrillation inhibition. LA-CA-mPEG bioconjugate exhibits superior effects in delaying aggregation kinetics and enhancing the inhibition of protein aggregation compared to the Tre-CA-mPEG bioconjugate. This enhanced protein fibrillation inhibition can be attributed to the larger hydrophobic surface and stronger interactions arising from the LA-CA-mPEG nanoassemblies.