SS-NMR applied to the structural characterization of poly(ethylenimine) (PEI) and related compounds

EMILSE LEAL; JUAN MANUEL LAZARO MARTINEZ; AGUSTÍN BYRNE; AYELEN CRESPI; GRACIELA BULDAIN

Santa Fé

Workshop; III Workshop de Resonancia Magnetica- NMR and EPR at the Forefront of Reserch; 2016

Departamento de Física de la Facultad de Bioquímica y Ciencias Biológicas de la Universidad Nacional del Litoral

Linear Poly(ethyleneimine hydrochloride) (PEI.HCl) polymer is a cationic polymer which binds DNA through electrostatic interactions, being a non-viral gene delivery vehicles widely used in transfection processes. Many factors, such as the molecular weight, surface charge, charge density, and hydrophilicity, affect the transfection efficiency of these polymers. Therefore, it is necessary to optimize and develop new agents or formulations to achieve high transfection efficiency in the process.1In the present study, we analyzed the impact of the lyophilization and deprotonation processes in PEI.HCl samples in the solid state. The main aim was to study the structural and dynamic homogeneity of three synthetic variants of linear PEI.HCl and PEIfree-base with different molecular weights (22, 87 and 217 KDa) in the crystallized or lyophilized states through 1D and 2D solid-state Nuclear Magnetic Resonance (ss-NMR) spectroscopy, together with X-ray photoelectron spectroscopy (XPS) and X-Ray Powder Diffraction (XRPD) measurements.1 In addition, changes after the uptake of Cu(II) ion by these polymeric matrices were explored, given the importance in the removal of heavy metal ions and the activation of hydrogen peroxide by the heterogeneous catalysts of Cu(II) for the degradation of pollutants with high environmental impact.2 Different 13C{1H} cross-polarization and magic angle spinning experiments using delayed contact time, 1H dipolar filter and 1H spin-lock filter were crucial to determine the different mobility domains in PEI samples. 13C direct polarization experiments allowed the quantification of the crystalline/amorphous segments in each sample. The lyophilization process produced an increase in the amorphous fraction, even when some ordered domains were present, whereas the coordination of copper/sulfate ions produced a significant decrease in the mobility of polymer chains, leading to homogeneous materials even when Cu was desorbed.