In a previous paper [1], the synthesis of various polystyrenepoly[NIPAM] core-shell latexes bearing cationic amidino and/or amino charges has been described. Several colloidal properties of these cationic latexes have been characterized such as: particle size, surface charge density, electrophoretic mobility and finally colloidal stability. Due to the poly[NIPAM]-rich layer in the shell, it was found that temperature played a significant role on all these properties, a LCST around 33°C being exhibited. In addition, ionic strength was also found to affect the colloidal behavior of these latexes, the largest effect being observed with latexes having both amidino and amino surface charges. The critical coagulation concentrations (CCC) of the various latexes above and below the LCST were determined, highlighting the contribution of electrostatic and steric repulsive forces to the stability of these particles.

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The activation of various synthetic oligodeoxyribonucleotides (ODNs), bearing a hexamethylamine arm at their 5 0 -end, with the 2,4-phenylenediisothiocyanate (PDC) was studied. The activation reaction had to be performed within 40 min, because of competitive hydrolysis of the isothiocyanate functions. ODN modifications were then characterized by different analytical methods i.e. gel capillary electrophoresis, Matrix-Assisted Laser Desorption-Ionization-Time of Flight (MALDI-TOF) mass spectrometry. Moreover, activation of the amine groups of the nucleic bases was evidenced through the chemical analysis of the enzymatic-digested conjugate (PDC-ODN) by reverse phase HPLC. Preliminary results on the covalent grafting of activated ODN molecules onto the aminated latex particles showed that the amount of grafted ODNs was directly related to the number of potential grafting sites on the nucleic acid probe (primary amine group of hexamethyl arm and amine functions of the nucleic bases).

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