Naked-Eye Enumeration of Single Chlamydia pneumoniae Based on Light Scattering of Gold Nanoparticle Probe

Single-virus-sensitive barcode qPCR mediated by the aggregation of gold nanoparticle probes

Herein, we developed a gold nanoparticle (GNP)-mediated barcode qPCR strategy with a sensitivity for a single virus particle per reaction for the detection of influenza virus H3N2. The analysis of the results for pure virus and real virus samples show that GNP-mediated barcode qPCR is ∼16 times more sensitive than conventional qPCR, demonstrating the potential to reduce false negatives and improve early diagnosis of viral infections.

Visual and Ultrasensitive Detection of a Coronavirus Using a Gold Nanorod Probe under Dark Field

Porcine epidemic diarrhea virus (PEDV), a coronavirus that causes highly infectious intestinal diarrhea in piglets, has led to severe economic losses worldwide. Rapid diagnosis and timely supervision are significant in the prophylaxis of PEDV. Herein, we proposed a gold-nanorod (GNR) probe-assisted counting method using dark field microscopy (DFM). The antibody-functionalized silicon chips were prepared to capture PEDV to form sandwich structures with GNR probes for imaging under DFM. Results show that our DFM-based assay for PEDV has a sensitivity of 23.80 copies/μL for simulated real samples, which is very close to that of qPCR in this study. This method of GNR probes combined with DFM for quantitative detection of PEDV not only has strong specificity, good repeatability, and a low detection limit, but it also can be implemented for rapid on-site detection of the pathogens.

Artificial intelligence-assisted enumeration of ultra-small viruses with dual dark-field plasmon resonance probes

Direct visual enumeration of viruses under dark-field microscope (DFM) using plasmon resonance probes (PRPs) is fast and convenient; however, it is greatly limited in the assay of real samples because of its inability to accurately identify false positives owing to non-specific adsorption. In this study, we propose an artificial intelligence (AI)-assisted DFM enumeration strategy for the accurate assay of Enterovirus A71 (an ultra-small human virus) using two PRPs; a 40 nm silver nanoparticle probe (SNP) that appears bright blue under DFM, and a 120 nm gold nanorod probe (GNP) that appears red under DFM. The capture chip was prepared by immobilizing the SNPs with antibodies on the glass to capture the target virus and to form dichromatic sandwich structures with the GNPs, followed by imaging under a dark field (DF). Subsequently, the DF images of the capture chip were subjected to a two-step screening: first, using image processing, and thereafter using the AI algorithm screening to eliminate false positive results and background noise. The results revealed that the data from the AI-assisted dual PRPs assay were highly consistent with those of quantitative PCR (qPCR), and that the sensitivity with a minimum detectable concentration of 3 copies/μL was 5 times higher than that of qPCR. The entire analysis was completed within 45 min. Therefore, our AI-assisted virus enumeration strategy with two DF PRPs holds great potential for ultra-sensitive and accurate quantification of viruses in real samples.