New hydrolyzable pH-responsive cationic polymers for gene delivery: a preliminary study

Here we want to report the synthesis and the characterization of 2-methylacrylic acid 2-(3-imidazol-1-yl-propionyloxy)ethyl ester (IPEMA), a new methacrylate derivative monomer bearing an hydrolyzable side chain terminated by an imidazole group. The kp/kt(1/2) value for its homopolymerization in N,N-dimethylformamide at 60 degrees C was found to be 0.120 mol(-1/2) x L(1/2) x s(-1/2). The free radical copolymerization of N,N-dimethylaminoethyl methacrylate and this monomer was studied in N,N-dimethylformamide at 60 degrees C, the reactivity ratios of this couple of monomers were determined to be r(DMAEMA) = 1.13 +/- 0.09 and r(IPEMA) = 0.82 +/- 0.09 (using distinct calculation methods). Molecular weights analysis, parallely with refractive index increments measurements, were performed to characterize the obtained polymers. Potentiometric titrations showed the ability of these copolymers to act as a 'proton sponge'. Preliminary study of the copolymers hydrolysis proved that imidazole units could be slowly cleaved from the polymer backbone at 37 degrees C in neutral aqueous buffer. Agarose gel electrophoresis of plasmid DNA/polymer complexes demonstrated the DNA complexing properties of these imidazole-based copolymers.