Quantitation of complexed versus free polymers in interpolyelectrolyte polyplex formulations

Xiaoling Wang, Sneha S. Kelkar, Amanda G. Hudson, Robert B. Moore, Theresa M. Reineke, Louis A. Madsen

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


The quantity of free polymer in a polymer/DNA complex (polyplex) formulation critically impacts its gene transfection efficiency, cellular uptake, and toxicity. In this study, the compositions of three interpolyelectrolyte polyplex formulations were quantified by a facile NMR method. Using careful integration of a 1D 1H NMR spectrum with a broad spectral width, the quantities of unbound polymer and polyplexes in solution were determined. Linear polyethyleneimine (PEI) mixed with DNA at polymer amine to DNA phosphate molar ratio (N/P ratio) of 5 revealed an effective binding N/P ratio of 3.5 without excess free polymer. This result is in strong agreement with the stoichiometric number of PEI/DNA binding obtained by isothermal titration calorimetry. The noninvasive nature of this method allows broad application to a range of polyelectrolyte coacervates, opening new opportunities for understanding and optimizing polyelectrolyte complex formation and providing quantitation of complex formation in a single measurement.

Original languageEnglish (US)
Pages (from-to)1038-1041
Number of pages4
JournalACS Macro Letters
Issue number11
StatePublished - Nov 19 2013


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