Synthesis and evaluation of molecularly imprinted polymers for nucleic acid bases using aniline as a monomer

The formation of molecularly imprinted polymers in aqueous media is often less effective particularly when the non-covalent approach of molecular imprinting is followed. The reduced efficiency is said to be due to the interference of water molecules in the formation of H-bonding between the template molecules and monomers. The feasibility of the formation of imprinted polymers in water is demonstrated here using aniline as monomer. Nuclei acid bases namely, thymine, cytosine, adenine and uracil were used as the templates. Polyaniline (PAN) formed in the presence of the templates molecules subsequently showed affinity towards the respective bases. The interesting phenomenon observed was the considerable variation in the extent of adsorption of the template molecules by the respective imprinted PAN. The extent of uptake of thymine and uracil by the imprinted polymers was nearly identical and was much higher than the amount of cytosine or adenine adsorbed by the corresponding polymers. Since the polymers were prepared under similar conditions, the extent of adsorption of all the four template molecules was expected to be comparable. Infrared spectra showed the formation of H-bonding between CO groups of the templates and amino groups of the PAN. Thymine and uracil contain two CO groups enabling stronger H-bonding resulting in the formation of more affinity sites leading to improved adsorption. The uptake of adenine was found to be less since it does' not contain any CO groups to engage in H-bonding with PAN. The variation in adsorption of the print molecules by the respective molecularly imprinted polymers was attributed to the probability of forming H-bonding of the template molecules with the imprinted matrices. The equilibrium adsorption was found to attain with in an hour. The study shows that PAN is a suitable matrix for the creation of affinity sites for water soluble molecules through molecular imprinting.