Redox sensitive cationic pullulan for efficient gene transfection and drug retention in C6 glioma cells
Thiolated cationic pullulan was synthesized by conjugating pullulan with polyethyleneimine (PEI) and mercaptosuccinic acid (MSA). The formed conjugate was oxidized to obtain disulfide linked cationic pullulan (PPMSS). PPMSS exhibited good buffering capacity and nanoplexes formulated were of size less than 150 nm. Nanoplexes formed with PPMSS are redox sensitive and susceptible to reductive cleavage by dithiothreitol (DTT) ensuring the intracellular release of DNA. In vitro, cytotoxic evaluation studies of polymers in C6 cell lines established its non-toxic nature. The studies using endocytosis inhibitors revealed the uptake pathways of nanoplexes. Further, the plasmid and polymer tracking studies indicated the successful unpacking of DNA from the nanoplexes and its nuclear localization. The gene transfection efficiency was established by the p53 gene expression studies. Furthermore, the ability of the polymer to inhibit efflux pumping in cancer cells has also been elucidated in terms of P-gp inhibition studies and drug retention kinetics using the anticancer drug, doxorubicin (DOX). Our results also suggest that greater retention of DOX was accompanied by the reduction of disulfide linkage by a ubiquitous intracellular stimulus, glutathione. Thus simultaneous gene and drug delivery using redox sensitive cationic polymers may have a promising potential in cancer therapy.