Luminous silica colloids with carbon dot incorporation for sensitive immunochromatographic assay of Zika virus†
Here a novel strategy is reported of assembling silanized carbon dots (CDs) with porous silica templates to form fluorescent CD-based silica (FCS) colloids with uniformly packed CDs throughout the silica matrix. Dendritic silica spheres with highly accessible central−radial pores are adopted as a powerful absorbent host, which can form Si–O bonds with silane to directly fix the silanized CDs. The appropriate loading content of CDs on the inner surface of dendritic silica spheres is beneficial for the maximum fluorescence intensity of FCS colloids. High-quality silanized CDs endow multiple CD embedded silica spheres with excellent properties, including good fluorescence performance, excellent colloidal/optical stabilities and convenient biofunctionalization. The integration of these FCS colloids with a lateral flow strip platform provides an ultra-sensitive, specific and robust immunoassay method for the Zika NS1 protein with a visual detection limit of 10 pg mL−1, and has been successfully applied to the detection of Zika virus in clinical samples. In addition, we also prepared conventional Au NP-based lateral flow test strips and applied them to the detection of Zika NS1 protein. By comparison, the detection limit of immunofluorescent CD-based silica (iFCS)-based lateral flow test strips is 100-fold lower than that of Au NP-based lateral flow strips.