Quaternized chitosan oligomers as novel gene delivery vectors in epithelial cell lines

Quaternized modifications of chitosan present characteristics that might be useful in DNA condensing and efficient gene delivery. Trimethylated chitos an (TMO) was synthesized from oligomeric chitosan (< 20 monomer units). TMO s spontaneously formed complexes (chitoplexes) with RSV-alpha3 luciferase p lasmid DNA. These complexes were characterized by photon correlation spectr oscopy and were investigated for their ability to transfect COS-1 and Caco- 2 cell lines in the presence and absence of fetal calf serum and compared w ith DOTAP (N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium sulphate) lipoplexes. Additionally, their effect on the viability of the respective c ell cultures was investigated using the 3-[4,5-dimethylthiazol-2-yl]-2,5-di phenyI tetrazolium bromide (MTT) assay. Results showed that quaternized chi tosan oligomers were able to condense DNA and form complexes with a size ra nging from 200 to 500 nm. Chitoplexes proved to transfect COS-1 cells, howe ver, to a lesser extent than DOTAP-DNA lipoplexes. The quaternized oligomer derivatives appeared to be superior to oligomeric chitosan. The presence o f fetal calf serum (FCS) did not affect the transfection efficiency of the chitoplexes. whereas the transfection efficiency of DOTAP-DNA complexes was decreased. Cells remained 100% viable in the presence of chitosan oligomer s whereas viability of DOTAP treated cells decreased to similar to 50% in b oth cell lines. Both DOTAP-DNA lipoplexes and chitoplexes resulted in less transfection efficiency in Caco-2 cell cultures than in COS-1 cells; howeve r quaternized chitosan oligomers proved to be superior to DOTA-P. Effects o n the viability of Caco-2 cells were similar to the effects observed in COS A cells. We conclude that trimethylated chitosan-DNA complexes present suit able characteristics and the potential to be used as gene delivery vectors. (C) 2001 Elsevier Science Ltd, All rights reserved.