Molecular weight determination of a newly synthesized guanidinylated disulfide-containing poly(amido amine) by gel permeation chromatography

A cationic gene delivery vector, guanidinylated disulfide-containing poly(amido amine) (CAR-CBA), was synthesized by Michael addition reaction between N,N′-cystaminebisacrylamide (CBA) and guanidine hydrochloride (CAR). Gel permeation chromatography (GPC) was used to evaluate the molecular weight of synthesized CAR-CBA. Polyethyleneimine (PEI) with molecular weight of 25 kDa was adopted as a reference, and polyethylene glycols (PEG) with different molecular weights were used to establish a standard curve for determining the molecular weight of CAR-CBA. The effects of two critical factors, namely columns and eluents, on the molecular weight measurement of CAR-CBA were investigated to optimize the GPC quantitative method. The results showed that Ultrahydrogel columns (120, 250) and HAc–NaAc (0.5 M, pH 4.5) buffer solution were the optimal column and GPC eluent, respectively. The molecular weight of the synthesized CAR-CBA was analyzed by the optimized GPC method and determined to be 24.66 kDa.