Impact of Organic Solvents, Surfactants, and Nonfunctionalized PEGs on PEGylation Reaction Yield

The optimization of PEGylation reaction yield is critical for the efficient production of therapeutic bioconjugates. This study systematically investigates the influence of three distinct classes of additives -organic cosolvents, nonreactive poly-(ethylene glycols) (PEGs) of varying molecular weights, and surfactants- on the conjugation efficiency of a model protein. Quantitative analysis via SDS-PAGE densitometry revealed that the addition of 40% (v/v) DMSO significantly enhanced the reaction yield compared to the aqueous control, while methanol resulted in a marked decrease in efficiency. These results were rationalized using Hansen solubility parameters, which indicated that the high dispersion cohesion (18.4 MPa^1/2) of DMSO promotes superior solvation of PEG chains, thereby minimizing competitive hydrolysis pathways. Furthermore, the inclusion of nonfunctionalized PEGs (4 and 8 kDa) provided a marginal increase in conjugation, likely due to the excluded volume effect. In contrast, the anionic surfactant SDS severely inhibited the reaction, a phenomenon attributed to electrostatic repulsion between the charged SDS-PEG-protein complexes. The nonionic surfactant polysorbate 20 exhibited a neutral effect on yield, suggesting its utility primarily as a protein stabilizer without compromising conjugation. These findings provide a comprehensive framework for the strategic selection of additives to modulate the physicochemical environment and maximize PEGylation efficiency.