A thermosensitive macroporous hydrogel showing selectivity for the lysozyme was developed by an imprinting procedure that is based on metal coordinate interaction. A metal chelate monomer [N-(4-vinyl)-benzyl iminodiacetic acid] forming coordination complex with the template protein in the presence of Cu ions co-polymerized with N-isopropylacrylamide and acrylamide, using N,N-methylenebisacrylamide as the cross-linker to prepare the thermosensitive protein-imprinted hydrogel. The synergetic combination of the smart property of the macroporous thermosensitive hydrogel with the merits of the coordinate interaction improved the selectivity and adsorption capacity, with respect to template lysozyme. The macropores were created by the frozen polymerization, and the influences of frozen polymerization and the chelate monomer content on the hydrogel affinity were investigated. The imprinted hydrogel can respond not only to external stimuli, but also to the template protein with a certain degree of shrinking. In recognition of the protein, the interaction of the imprinted thermosensitive hydrogel to the protein can be switched between the coordinate effect and the electrostatic effect by adding or not adding Cu ions. Finally, this imprinted hydrogel was used to purify the template lysozyme from the mixture of proteins and the real sample, which demonstrated its high selectivity.

This work presented a novel strategy for the synthesis of the hybrid structure silica/CdTe/molecularly imprinted polymer (Si-NP/CdTe/MIP) to recognize and detect the template bovine hemoglobin (BHb). First, amino-functionalized silica nanoparticles (Si-NP) and carboxyl-terminated CdTe quantum dots (QDs) were assembled into composite nanoparticles (Si-NP/CdTe) using the EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride) chemistry. Next, Si-NP/CdTe/MIP was synthesized by anchoring molecularly imprinted polymer (MIP) layer on the surface of Si-NP/CdTe through the sol-gel technique and surface imprinting technique. The hybrid structure possessed the selectivity of molecular imprinting technique and the sensitivity of CdTe QDs as well as well-defined morphology. The binding experiment and fluorescence method demonstrated its special recognition performance toward the template BHb. Under the optimized conditions, the fluorescence intensity of the Si-NP/CdTe/MIP decreased linearly with the increase of BHb in the concentration range 0.02-2.1 μM, and the detection limit was 9.4 nM. Moreover, the reusability and reproducibility and the successful applications in practical samples indicated the synthesis of Si-NP/CdTe/MIP provided an alternative solution for special recognition and determination of protein from real samples.

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