Human enterovirus 71 (EV71) is one of the pathogens that causes hand, foot, and mouth disease (HFMD), which generally leads to neurological diseases and fatal complications among children. Since the early clinical symptoms from EV71 infection are very similar to those from Coxsackievirus B3 (CVB3) infection, a robust and sensitive detection method that can be used to distinguish EV71 and CVB3 is urgently needed for prompting medical treatment of related diseases. Herein, based on immunomagnetic nanobeads and fluorescent semiconductor CdSe quantum dots (QDs), a method for simultaneous point-of-care detection of EV71 and CVB3 is proposed. The synchronous detection of EV71 and CVB3 virions was achieved within 45 min with high specificity and repeatability. The limits of detection are 858 copies/500 μL for EV71 and 809 copies/500 μL for CVB3.This proposed method was further validated with 20 human throat swab samples obtained from EV71 or CVB3 positive cases, with results 93.3% consistent with those by the real-time PCR method, demonstrating the potential of this method for clinical quantification of EV71 and CVB3. The method may also facilitate the prevention and treatment of the diseases.

On the basis of the supported protein layers (SPLs) substrate, the study presented an ultrasensitive and highly specific platform for single-molecule fluorescence detection of antibody using quantum dots (QDs) as probes. To construct the SPLs surface platform for antibody immobilization, bovine serum albumin (BSA), anti-BSA, and protein G were firstly attached to carboxyl-terminated substrate surfaces by turns. Then nonspecific adsorption of single antibody molecules on SPLs surfaces was investigated. Through the irreversible interaction between streptavidin and biotin, streptavidin-QD conjugates were employed to conjugate with biotinylated antibody, producing QD-antibody conjugates for generating fluorescent signals in fluorescent imaging. Epi-fluorescence microscopy equipped with an electron multiplying charge-coupled device was chosen as the tool for single-molecule fluorescence detection here. The concentration of antibody is quantified based on the direct counting of individual fluorescent spots, one by one. The generated fluorescent signals increased with the increasing concentration of immobilized antibody and were found to be proportional to antibody concentrations. The better brightness and photostability of QDs, and slower increase in the number of counted molecules make a large linear dynamic range of 1.0 × 10−14 to 3.0 × 10−12 mol L−1 between the number of single molecules and antibody concentrations, which is comparable to the previously reported surface-based SMD analysis.