Nanobody-based fluorescent immunoassay using carbon dots anchored cobalt oxyhydroxide composite for the sensitive detection of fenitrothion

• DOI: 10.1016/j.jhazmat.2022.129701
• Publication Date: 2022-07-30T14:38:24Z
• Authors: Lin Luo; Shi-Qi Lin; Zhuo-Yu Wu; Hong Wang; Zi-Jian Chen; Hao Deng; Yu-Dong Shen; Wen-Feng Zhang; Hong-Tao Lei; Zhen-Lin Xu
• Keywords: Immunoassay; Tandem Mass Spectrometry; Humans; Oxides; Cobalt; Fenitrothion; Alkaline Phosphatase; 01 natural sciences; Carbon; 0104 chemical sciences; 3. Good health

Fenitrothion (FN) residue in food is a serious threat to public health. Consequently, a sensitive, cost-effective, and convenient immunoassay for FN urgently needs to be fabricated to safeguard human health. Herein, a nanobody-alkaline phosphatase fusion protein (Nb-ALP)-based fluorescent ELISA using red emissive carbon dots (r-CDs) anchored cobalt oxyhydroxide nanosheet (CoOOH NS) composite was developed for detecting FN. Briefly, a Nb-ALP was obtained by autoinduction expression and employed as a recognition, signal transduction, and amplification element. As the fluorescence signal source, r-CDs were assembled with CoOOH NS to yield the r-CDs@CoOOH NS composite, leading to the fluorescence quenching of r-CDs via Förster resonance energy transfer (FRET). After competitive immunoreaction, the Nb-ALP bounded to the immobilized antigen can mediate the production of ascorbic acid, which can reduce the CoOOH NS to Co2+, breaking the FRET between r-CDs and CoOOH NS, accompanied by the fluorescence recovery of r-CDs. This fluorescent ELISA is highly sensitive to FN with a detection limit of 0.14 ng mL-1, which is 25-fold lower than that of conventional colorimetric ELISAs. The recovery test of food samples and the validation by GC-MS/MS further demonstrated the proposed assay was an ideal tool for detecting FN.