PEGylation of polymerized albumin retains colloid osmotic pressure: Towards an enhanced potential plasma substitute

Plasma expanders (PEs) are commonly used to replace lost blood volume for septic shock patients with increased vascular permeability. Human serum albumin (HSA) is the preferred PE, due to its innate ability to restore blood colloid osmotic pressure (COP). However, HSA is susceptible to protein extravasation under endothelial dysfunction leading to edema and exposing tissue to toxic HSA-bound metabolites. To prevent extravasation, the molecular diameter of HSA has been previously increased through chemical polymerization to yield polymerized HSA (PHSA). In this study, we further optimize PHSA size and COP via polyethylene glycol (PEG) surface conjugation. Previously synthesized PHSA that was size fractionated via tangential flow filtration (TFF) into two brackets (bracket A [500 kDa-0.2 μm] and bracket B [50-500 kDa]) served as precursors for subsequent PEGylation. Each PHSA bracket was thiolated with 2-iminothiolane hydrochloride (IT) and PEGylated with monofunctional 5 kDa maleimide PEG to yield PEGylated PHSA (PPHSA). All PPHSA solutions exhibited increased molecular size, zeta potential, and osmolality compared to their non-PEGylated precursor PHSA. At the same total protein concentration, PPHSA viscosity decreased compared to the precursor PHSA, while the COP remained consistent with HSA, indicating their potential to serve as PEs.