Bioengineering functional copolymers. VIII. stimuli-responsive boron-containing graft copolymers and their poly(ethylene imine) macrocomplexes and DNA conjugates

Abstract

New boron-containing graft copolymers and their poly(ethylene imine) (PEI) macrocomplexes were synthesized by amidolysis of poly(N-isopropylacrylamide-co-maleic anhydride)s [poly(NIPA-co-MA)s] with ethanolamine ester of diphenylboronic acid (EAPB), and following complexation of graft copolymers with poly(ethylene imine) (PEI), respectively. The structure, compositions and properties (stimuli-responsive, polyelectrolyte and thermal behavior) of synthesized copolymers were characterized by FTIR, 1H {13C} NMR and UV spectroscopy, viscometry, DSC and TGA analyses. It was shown that under given conditions (pH, temperature and grafting degree), these H-bonding macrocomplexes with hydrophobic diphenylborate side chain groups in aqueous solutions undergo a reversible cooperative conformational transition which is provided a promising possibility of adjusting the hydophobic–hydrophilic balance in the studied graft copolymer systems. Fluorescence measurements indicated that poly[(NIPA-co-MA)-g- EAPB]/PEI macrocomplex easily transferred to the HELA tumor cells, and showed low cytotoxicity against a normal cell line. Obtained results, especially stimuli-responsive and very high transferable behavior allow use these boroncontaining graft copolymer systems as non-viral vectors in gene- and bioengineering processes and drug delivery systems, as well as in boron neutron capture therapy.