Rapid sensing of Cu+2 in water and biological samples by sensitive molecularly imprinted based plasmonic biosensor

In this study, copper (II) ion (Cu+2) imprinted poly(hydroxyethyl methacrylate-N-metacryloyl-(L)-cysteine methyl ester [PHEMAC-Cu+2] nanoparticles were synthesized by two-phase mini-emulsion polymerization method and applied to the SPR sensor chip surface for the selective determination of the Cu+2 ions in both aqueous solution, Cu+2-spiked artificial urine and physiological serum samples to investigate the effects of metabolite residues during the analysis. The non imprinted [PHEMAC] nanoparticles were synthesized by applying the same procedure for the [PHEMAC-Cu+2] nanoparticle synthesis except the addition of Cu+2 ions as a control experiment to evaluate the selectivity of the [PHEMAC-Cu+2] nanoparticles. Roughness differences between [PHEMAC-Cu+2] and [PHEMAC] nanoparticles showed that the imprinting process of Cu+2 ions was performed successfully. [PHEMAC-Cu+2] and [PHEMAC] SPR biosensors prepared by attaching nanoparticles onto the surface of sensor chips, were characterized by atomic force microscope, ellipsometer, contact angle measurements. Langmuir adsorption model was found the most applicable model for this affinity system. Results showed that Cu+2 affinity regions on the surface of [PHEMAC-Cu+2] SPR biosensor were homogeneously distributed and have a monolayer structure. Having the high imprinting efficiency with the imprinting factor of 4.74, the [PHEMAC-Cu+2] SPR biosensor was found to show more selectivity towards the target Cu+2 than the non-imprinted [PHEMAC] SPR biosensor. The selectivity studies of [PHEMAC-Cu+2] SPR biosensors for Cu+2 detection were investigated by using Zn+2 and Ni+2 solutions selected as competitor molecules. The results of intraday and interday precision studies were carried out to ascertain the reproducibility of the proposed method and reported as percent relative standard deviation (%RSD) value.