Self-assembling poly(L-lysine)/DNA complexes capable of integrin- mediated cellular uptake and gene expression

Abstract

Integrin-mediated delivery of genes is evaluated using a synthetic vector formed by self-assembly of DNA with an oligolysine- peptide sequence containing RGD (referred to as K16-RGD). The RGD peptide binds plasmid DNA effectively and inhibits ethidium bromide/DNA fluorescence at N-to-P ratios of less than 1.0. At N:P ratio 1.0, peptide/DNA complexes formed show a mixture of normal DNA migration and retention at the origin when analysed by agarose electrophoresis. At N:P ratio of 1.2, the complexes have a slight positive surface charge (5 mV) and in the absence of serum they show 10-fold increase uptake into 293 cells, compared with control poly(L-lysine)/DNA vectors, together with a 100-fold increase in transfection. In the presence of serum, RGD-mediated uptake is decreased about 3-fold, but the targeted vectors achieve over 150 times greater transfection than poly(L-lysine)/DNA controls. Transfection could be inhibited by addition of competing RGD, and to a lesser extent RGE, peptides. The targeted vector is believed to achieve cell uptake and transfection by binding av integrins in the cell surface, and the approach could be employed to promote internalisation of vectors following their binding to other, high affinity, receptors, in a system analogous to adenovirus entry.