Thermosensitive molecularly imprinted core–shell CdTe quantum dots as a ratiometric fluorescence nanosensor for phycocyanin recognition and detection in seawater

Abstract

Versatile molecular imprinted fluorescence sensors have been prepared for various species, but the imprinting based fluorescence detection of target proteins upon different external stimulation is rarely reported. Herein, a novel phycocyanin-imprinted ratiometric fluorescence nanosensor was developed for the temperature regulated sensing and detection of a phycocyanin target based on fluorescence resonance energy transfer (FRET). The nanosensor was fabricated via simple facile copolymerization, with amino/carboxyl modified quantum dots (QDs) as a fluorescent support, N-isopropylacrylamide as a thermo-responsive functional monomer, N,N-methylenebisacrylamide as a cross-linker and phycocyanin as a template. Under temperature control at 20 °C and 45 °C, the fluorescence intensities of the QDs and phycocyanin were regularly decreased and enhanced, respectively, to a different extent as the concentration of phycocyanin increased, and thereby the ratio of the two fluorescence peak emission intensities of QDs and phycocyanin was used to determine the concentration of phycocyanin. Good linearity was obtained within the range of 0–1.8 μM (r = 0.9900) with a low detection limit of 3.2 nM, and excellent recognition selectivity towards the phycocyanin target was achieved over other proteins. Moreover, satisfactory recoveries of 92.0–106.8% were obtained in spiked seawater samples. This study provides a facile, fast and intelligent way to conduct identification analysis of trace proteins in complex water matrices, and can push forward protein imprinting and stimuli-responsive imprinting related research.