Development of an excipient polarity screening tool for protein formulations via solvatochromism

This investigation explored the use of solvatochromism to develop a novel polarity screening classification tool for assessing the polarity environment of key excipients (buffers, amino acids, sugars, and salts) commonly used in protein formulation development. The polarity screening classification tool was developed using multivariate analysis, principal component analysis, and K-means clustering algorithms based on the ultraviolet (UV) absorbance (235 - 335 nm) of a solvatochromic probe in aqueous excipient solutions. Thereafter, protein functionality was assessed, and the results were correlated with the polarity profiles generated by the classification tool. The underlying hypothesis was that similar polarity environments would yield comparable protein functionalities; while differing environments would result in greater protein functional variation. This approach effectively captured how differences in the polarity of commonly used protein formulation excipients correlated with functionality results for model proteins such as alcohol dehydrogenase, polyphenol oxidase, and β-galactosidase. Results underscore the sensitivity of the solvatochromic approach in detecting polarity variations that extend beyond conventional excipient chemical group classifications (e.g., salts, sugars, amino acids, and buffers) while revealing unique molecular properties in aqueous solutions that could alter protein functionality. Thus, this study contributes to the understanding of the role of excipients and their polarity in protein formulations and positions solvatochromism as an effective method to rationalize early preclinical excipient selection towards streamlining protein formulation development.