Abstract
A new strategy for the design and construction of molecularly imprinted magnetic fluorescent nanocomposite-based-sensor is proposed. This multifunctional nanocomposite exhibits the necessary optics, magnetism and biocompatibility for use in the selective fluorescence detection of lysozyme. The magnetic fluorescent nanocomposites are prepared by combining carboxyl- functionalized Fe3O4 magnetic nanoparticles with l-cysteine-modified zinc sulfide quantum dots (MNP/QDs). Surface molecular imprinting technology was employed to coat the lysozyme molecularly imprinted polymer (MIP) layer on the MNP/QDs to form a core-shell structure. The molecularly imprinted MNP/QDs (MNP/QD@MIPs) can rapidly separate the target protein and then use fluorescence sensing to detect the protein; this reduces the background interference, and the selectivity and sensitivity of the detection are improved. The molecularly imprinted MNP/QDs sensor presented good linearity over a lysozyme concentration range from 0.2 to 2.0 μM and a detection limit of 4.53 × 10−3 μM for lysozyme. The imprinting factor of the MNP/QD@MIPs was 4.12, and the selectivity coefficient ranged from 3.19 to 3.85. Furthermore, the MNP/QD@MIPs sensor was applied to detect of lysozyme in human urine and egg white samples with recoveries of 95.40–103.33%. Experimental results showed that the prepared MNP/QD@MIPs has potential for selective magnetic separation and fluorescence sensing of target proteins in biological samples.
Highlights
Mn2+ -doped zinc sulfide quantum dots (Mn2+ : ZnS QDs) exhibit low toxicity and are synthesized by using Mn doped with non-heavy metal elements [1]
The selective binding of the imprinting site involves two aspects: (1) multiple weak interactions provided by the monomer, cross-linker, and Lyz molecule; and (2) the size, shape, and functional group complementarity between the imprinted cavities and template molecule in the imprinting process. These results showed that these new magnetic nanoparticles (MNPs)/QD@molecularly imprinted polymer (MIP) have the ability to act as a multifunctional biosensor for direct magnetic separation and it could transform molecular recognition events into fluorescence signals for selective recognition of the target protein molecule
The fluorescence intensity only slightly decreased after storage for 30 days. These results suggest that the MNP/QD@MIPs possessed good regeneration ability and stability, and have potential in practical application for sensing of Lyz
Summary
Mn2+ -doped zinc sulfide quantum dots (Mn2+ : ZnS QDs) exhibit low toxicity and are synthesized by using Mn doped with non-heavy metal elements [1]. Mn2+ : ZnS QDs have unique optical properties, such as symmetric emission, size-dependent emission-wavelength tunability, photochemical stability, and low biotoxicity [2,3,4,5]. These features of Mn2+ : ZnS QDs often result in their use as fluorescent nanosensors with improved sensitivities for the detection of biomacromolecules [6,7]. Fe3 O4 MNPs can automate and simplify the assay process using magnetic separation, which facilitates sample pretreatment and purification, and improves the efficiency of the assay process [10,11]. Fe3 O4 MNPs are widely used in biochemical separations, sensor applications and bioanalyses [12,13,14,15]
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