Preparation of DNA complexes with diblock copolymers of poly[N(2-hydroxypropyl)methacrylamide] and polycations

This study investigated the effects of the speed of component mixing, total concentration of polymers and ionic strength of solvents on formation of i nterpolyelectrolyte complexes (IPECs) of calf thymus DNA with diblock copol ymers of N-(2-hydroxypropyl)methacrylamide (HPMA) and 2-(trimethylammonio)e thyl methacrylate (TMAEMCl). The diblock copolymer consisting of a poly(HPM A) block (A) and poly(TMAEMCl) polycation block (B) with pendant quaternary ammonium groups acid with molecular weight of A block higher than that of B was used in the study. Poly(TMAEMCl) polycation were used for comparison. Static and dynamic light scattering methods were used for characterisation of complexes. The apparent mass-average molecular weights, M-w(a), and hyd rodynamic radii, R-H(a), of slightly overcompensated IPECs (phi = [cation u nits]/[DNA negative charges] = 1.1) prepared by fast mixing of components w ere found to be only slightly smaller than those prepared by slow mixing. B oth M-w(a) and R-H(a) of IPECs prepared under stoichiometric conditions(phi = 1) decreased with decreasing total polymer concentration, c(T), approach ing M-w and R-H of single DNA complexes which are the most suitable ones fo r DNA uptake into cells. The presence of NaCl in solutions resulted in a si gnificant increase in M-w(a) and R-H(a) of IPECS. (C) 1999 Elsevier Science S.A. All rights reserved.