Towards DNA sensing polymers: interaction between acrylamide/3-(N,N-dimethylaminopropyl)-acrylamide and DNA phage λ at various N/P ratios

The present study strongly relates to ongoing research on the development of cationic polymers which are of great interest due to their enormous potential for biomedical applications, especially as non-viral vectors for gene therapy, antimicrobial agents and active components in DNA sensing devices. The current paper demonstrates that a functional group approach can be successfully realized in a free-radical copolymerization process to prepare cationic copolymers with a desired composition of amine groups, which can be protonated in water thus, providing electrostatic interactions between a polycation and DNA. Three replicas of the cationic copolymer, acrylamide/3-(N,N-dimethylaminopropyl)-acrylamide (AADMAPA), were synthesized using this strategy. The values of average molecular mass and polydispersity index, are similar for the replicas, averaged to 24 000 +/- 2000 g mol(-1) and 1.5 +/- 0.1, respectively. The copolymer composition according to H-1-NMR (D2O), was corresponded to the molar ratio of initial monomers. The dynamic light scattering studies and zeta potential measurements confirmed that in water positively charged AADMAPA/DNA polyplexes are formed at N/P > 2.2: the formed particles have bimodal distributions with the average diameters of 70 and 700 nm. Zeta potential measurements indicated that the point of zero charge (isoelectric point) is close to N/P congruent to 2.2. According to the atomic force microscopy positively charged AADMAPA/DNA polyplexes have axially symmetric shapes.