Comparative syntheses of tetracycline-imprinted polymeric silicate and acrylate on CdTe quantum dots as fluorescent sensors

Abstract

The amphoteric drug molecule tetracycline, which contains groups with pKa 3.4–9.9, was used as a template for conjugating molecularly imprinted polymers (MIPs) and as a quencher for CdTe quantum dot (QD) fluorescence. Two MIP–QD composites were synthesized by a sol–gel method using a silicon-based monomer and a monomer linker between the MIP and QD, i.e., tetraethoxylsilane/3-mercaptopropyltriethoxysilane (MPS) and tetraethoxylsilane/3-aminopropyltriethoxysilane (APS). Another MIP–QD composite was synthesized by the chain-growth polymerization of methacrylic acid (MAA) and an allyl mercaptan linker. The prepared MIP–QDs were characterized by FTIR and SEM and utilized at 0.33mg/mL to determine the tetracycline content in phosphate buffers (pH 7.4, 50mM) through the Perrin and Stern−Volmer models of quenching fluorometry. The Perrin model was applied to tetracycline concentrations of 7.4μM–0.37mM for MIP–MPS–QD, 7.4μM–0.12mM for MIP–APS–QD, and 7.4μM–0.10mM for MIP–MAA–QD (R2=0.9988, 0.9978, and 0.9931, respectively). The Stern−Volmer model was applied to tetracycline concentrations of 0.12–0.37mM for MIP–APS–QD (R2=0.9983) and 0.10–0.37mM for MIP–MAA–QD (R2=0.9970). The detection limits were 0.45μM, 0.54μM, and 0.50μM for MIP–MPS–QD, MIP–APS–QD, and MIP–MAA–QD, respectively. Equilibrium times, differences between imprinted and nonimprinted polymers, and MIP–QD quenching mechanisms were discussed. Finally, specificity studies demonstrated that MIP–MAA–QD exhibited optimal recoveries of 96% from bovine serum albumin (n=5, RSD=3.6%) and 91% from fetal bovine serum (n=5, RSD=4.8%).