Magnetic Nanoparticle-Based Ligand Replacement Strategy for Chemical Luminescence Determination of Cholesterol

Abstract

Determination of serum cholesterol (Chol) is important for disease diagnosis, and has attracted great attention during the last few decades. Herein, a new magnetic nanoparticle-based ligand replacement strategy has been presented for chemical luminescence detection of Chol. The detection depends on ligand replacement from ferrocene (Fc) to Chol through a β-cyclodextrin (β-CD)-based host-guest interaction, which releases Fc-Hemin as a catalyst for the luminol/hydrogen peroxide chemical luminescence system. More importantly, the luminescence signal can be captured by the camera of a smartphone, thus realizing Chol detection with less instrument dependency. The limit of detection of this method is calculated to be 0.18 μM, which is comparable to some of the developed methods. Moreover, this method has been used successfully to quantify Chol from serum samples with a simple extraction process.

Keywords: Hemin; chemical luminescence assay; cholesterol detection; host-guest interaction; smartphone.

Scheme 1

Schematic figure shows Chol detection using magnetic nanoparticle-based ligand replacement strategy.

Scheme 2

Synthetic route of Fc–Hemin. (a) (Boc)₂O, triethylamine (TEA), ethanol, room temperature (rt); (b) 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide (EDC), 1-Hydroxybenzotriazole (HOBt), N,N-Dimethylformamide (DMF), rt; (c) Trifluoroacetic acid (TFA), Dichloromethane (DCM), rt; (d) EDC, HOBt, DMF, rt.

Figure 1

(A) The continual images of chemical luminescence from the reaction mixture in the presence of 1 μM. (B) Quantitative result shows that luminescence intensity decreases as time passes; the data were from (A). (C) Plots of luminescence intensity against the concentration of Hemin (0, 0.02, 0.05, 0.1, 0.2, 0.5, 1 μM). Photo images were taken using a smartphone with 8-s exposure for each.

Figure 2

(A) TEM image of synthetic Fe₃O₄ magnetic nanoparticle. (B) TEM image of Fe₃O₄@SiO₂-CD. (C) DLS result shows size distribution of Fe₃O₄@SiO₂-CD nanoparticle. (D) FTIR spectra of Fe₃O₄@SiO₂-CD and free β-CD. The arrow points to a typical signal from C-H stretching vibrations of β-CD.

Figure 3

(A) Schematic figure shows the procedure of Chol detection. (B) Photo images taken using a smartphone in the detection of Chol at different concentrations (0, 2, 5, 10, 20, 40 μM). (C) Luminescence intensity was analyzed by ImageJ and plotted as the function of concentration.

Figure 4

(A) Schematic figure shows the procedure of Chol extraction and detection. (B) Quantitative detection result from the presented method and a commercial kit. SE stands for human serum.