Point-of-care testing of neuromyelitis optica spectrum disorder using a sonochemically enhanced bifunctional CdTe-ZIF-8 nanohybrids-labelled lateral flow immunoassay

Neuromyelitis optica spectrum disorder (NMOSD) is a neurological disease with rapid progression that can lead to severe visual impairment and paralysis. Rapid diagnosis at presentation significantly improves its prognosis, but there is a lack of available point-of-care testing (POCT) methods. Herein, for the first time, a colorimetric-fluorescent bifunctional nanoparticles (CFNPs)-based bimode lateral-flow immunoassay (LFIA) was developed for rapid and sensitive on-site diagnosis of NMOSD biomarker (AQP4-IgG). We first developed a novel sonochemistry-assisted strategy for the ordered self-assembly of CdTe quantum dots (QDs) using metal-organic framework (MOF) and polydopamine (PDA) flexible scaffold modification to fabricate CdTe@ZIF-8@PDA. Through rational design, the synthesis efficiency and fluorescence intensity of CdTe@ZIF-8 were 15-times and 9.67-times higher than those of the traditional synthesis method, respectively, and the colorimetric signal brightness and stability were significantly improved. The limit of detection of the CdTe@ZIF-8@PDA-labelled LFIA for AQP4-IgG titer detection by naked-eye colorimetric and smartphone-based fluorescence signal were 1:1.56 and 1:0.78, which were comparable to those of the gold standard cell-based assay (CBA). The diagnostic specificity and sensitivity for 121 clinical samples were 100 % and 82.35 % (colorimetric), and 100 % and 80.39 % (fluorescent). Our work has demonstrated an innovative strategy for constructing CFNPs and NMOSD on-site diagnostic approach that can be used for POCT.