PROTECTIVE INTERACTIVE NONCONDENSING (PINC) POLYMERS FOR ENHANCED PLASMID DISTRIBUTION AND EXPRESSION IN RAT SKELETAL-MUSCLE

We have developed protective interactive noncondensing (PINC) polymers , such as poly(N-vinyl pyrrolidone) (PVP) and poly(vinyl alcohol) (PVA ), to protect plasmids from extracellular nuclease degradation while a llowing the flexible complex to diffuse throughout the muscle tissue. Molecular modeling, zeta potential modulation, and ethidium bromide in tercalation studies were performed to assess the mechanism of interact ion between PVP and plasmid. The effect of salt concentration, pH, and polymer-plasmid ratios were investigated. We have correlated these va riables with beta-galactosidase (beta-gal) expression after intramuscu lar administration to rats. PVP can form hydrogen bonds with the base pairs within the major groove of DNA at pH 4.0. The PVP-plasmid intera ction results in a complex that is more hydrophobic (less negatively c harged) than the uncomplexed plasmid due to the vinyl backbone of PVP. Up to a ten-fold enhancement in gene expression in rat muscle over th e use of 'naked' DNA has been demonstrated using these systems. A line ar structure-activity relationship (SAR) was found between the percent vinyl pyrrolidone monomer content in poly(vinyl pyrrolidone-covinyl a cetate) polymers and beta-gal expression in muscle. Modulation of the interaction between PINC polymers and plasmid directly impacts the lev els of gene expression in vivo. The linear SAR is being used to design novel PINC polymers with enhanced binding affinity to plasmids. (C) 1 998 Elsevier Science B.V.