Polyelectrolyte functionalized magnetic emulsion for specific isolation of nucleic acids.

A magnetic oil in water (o/w) emulsion was cationized by adsorption of poly(ethyleneimine) (PEI). In a subsequent step, the cationic particles were derivatized with partially hydrolyzed poly(maleic anhydride-alt-methyl vinyl ether) copolymer (PMAMVE) to lead negatively charged colloids. The experimental conditions for the covalent grafting of the PMAMVE were selected on the basis of colloidal stability, charge inversion and absence of inhibition of the enzymatic DNA/RNA amplification reactions. Once the experimental conditions were selected, oligonucleotides (ODN) bearing particles were obtained according to the sequential process: (i) grafting of single stranded ODNs onto PMAMVE; (ii) grafting of the PMAMVE-ODN conjugates onto the cationic particles according to the conditions defined above. In this strategy, both steps could be independently controlled. The ODN-PMAMVE-particles conjugates were very stable with time, did not inhibit RT-PCR and were capable of hybridizing specifically with the complementary target.