Synthetic polyelectrolytes are a broad class of vaccine adjuvants. Among them, polyacrylic acid (PAA), a polyanionic polymer, is currently evaluated by Sanofi Pasteur. As chain length is considered to be a critical quality attribute for adjuvant properties of PAA, measurement of precise and accurate molecular size parameters is important for these polymers. In the field of synthetic polymer chemistry, methods for determination of molecular size parameters are well defined. Specifically, high performance size-exclusion chromatography (HPSEC) with multi-detection system is a method of choice. This paper describes the development of HPSEC method to well characterize and precisely quantify PAA in different adjuvant formulations. A first set of characterizations were made, with determination of dn/dc coefficient, which enabled the determination of weight- and number-average molecular weight, viscosimetric radius, and intrinsic viscosity. In-depth characterization was also made with branching study through the use of Mark-Houwink parameter determination. The quantification method was also evaluated according to validation method-like criteria: limit of detection and limit of quantification, repeatability, accuracy, and specificity with recombinant surface glycoprotein gB from human cytomegalovirus (CMV-gB) as model antigen.
Keywords: Branching; Intrinsic viscosity; Molecular weight; Vaccine adjuvant; Viscosimetric radius.