A Sensitive Immunochromatographic Test Strip Based on Hydrophobic Quantum Dots Incorporated into Mg/Fe Nanoflowers for HCG Detection

As the most widely used disposable paper-based diagnostic tool in the world, immunochromatographic test strips (ICTS) have occupied more and more positions in the field of rapid diagnosis due to their ease of operation and affordability. Therefore, the development of an easily prepared, sensitive, and accurate signal reporter is of great significance for the detection of some low-abundance biomarkers in clinical diagnosis. Herein, Mg/Fe layered double hydroxide nanoflowers (MF NFs) were selected as adsorption templates and sulfhydryl-functionalized, followed by one-step loading of hydrophobic CdSe/ZnS quantum dots in the organic phase via a metal-thiol covalent bond. After coating the reporter with branched polyethyleneimine (PEI), a novel ICTS fluorescent reporter was prepared. The modification of PEI not only improved the hydrophilicity of MF@CdSe/ZnS NFs but also introduced amino functional groups on the surface of the reporter for subsequent conjugation with antibodies. X-ray photoelectron spectroscopy, UV-vis absorption, X-ray diffraction, fluorescence spectroscopy, and infrared spectroscopy were used to characterize the composition of MF@CdSe/ZnS NFs. Under the optimal experimental conditions, the detection range of MF@CdSe/ZnS@PEI-ICTS for the model analyte HCG was 0.1–500 mIU/mL, and the limit of detection (LOD) reached was 0.1 mIU/mL. The potential for practical application was validated by the detection of HCG in spiked healthy human serum, showing overall recoveries between 90.48 and 116.1% with coefficients of variation that ranged from 3.66 to 12.91%