RNA nucleoside recognition by phthalocyanine-based molecularly imprinted polymers

Highly selective molecularly imprinted polymers (MIPs) having a phthalocyanine-based recognition centre as receptors for RNA nucleoside were prepared. In particular, a zinc phthalocyanine peripherally substituted with methacrylic groups was synthesized and utilized as functional monomer in combination with methacrylic acid (MAA) to form polymers with the aim to obtain MIPs having improved binding capacity and selectivity for nucleosides. Tri-O-acetyladenosine (TOAA) was utilized as model template in the preparation of the MIPs. The corresponding non metallated phthalocyanine was also prepared and used as functional monomer for the preparation of the MIPs in order to understand the role of the Zinc(II) ion in the binding capacity of the polymers towards the template molecule. The MIP prepared by using both the zinc phthalocyanine and MAA showed higher binding ability towards TOAA compared to the MIPs prepared using only MAA or its combination with the non metallated phthalocyanine. The results obtained suggest that the nucleoside is specifically bound to the polymer through multi-point interactions involving both the coordination of the nucleoside to the metal of the phthalocyanine and hydrogen bonding/electrostatic interactions with MAA and the modifiers linked to the phthalocyanines. As for the selectivity, the MIPs exhibited relative high binding affinities for TOAA while they did not show any binding capacity for the other RNA nucleosides.