RESUMEN
Bis(diphenylphosphino)alkanes quantitatively react with excess 1-bromododecane to prepare novel phosphonium gemini surfactants with spacer lengths ranging from 2 to 4 methylenes (12-2/3/4-12P). Dodecyltriphenylphosphonium bromide (DTPP), a monomeric surfactant analog, was readily water soluble, however, in sharp contrast, phosphonium gemini surfactants were poorly soluble in water due to two hydrophobic tails and relatively hydrophobic cationic head groups containing phenyl substituents. Isothermal titration calorimetry did not reveal a measurable critical micelle concentration for the 12-2-12P phosphonium gemini surfactant in water at 25 °C. Subsequent studies in 50/50 v/v water-methanol at 25 °C showed a CMC of 1.0 mM for 12-2-12P. All phosphonium gemini surfactants effectively complexed nucleic acids, but failed to deliver nucleic acids in vitro to HeLa cells. The solution behavior of phosphonium gemini surfactants was investigated in chloroform, which is an organic solvent where reverse micellar structures are favored. Solution rheology in chloroform explored the solution behavior of the phosphonium gemini surfactants compared to DTPP. The 12-2-12P and 12-3-12P gemini surfactants were successfully electrospun from chloroform to generate uniform fibers while 12-4-12P gemini surfactant and DTPP only electrosprayed to form droplets.
RESUMEN
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.