Sensitive Colorimetric Detection of Interleukin-6 via Lateral Flow Assay Incorporated Silver Amplification Method

Interleukin-6 (IL-6) is a pro/anti-inflammatory cytokine, the quantitative detection of which has been extensively considered for diagnosis of inflammatory associated diseases. However, there has not yet been a reliable, low-cost, and user-friendly platform developed for point-of-care (POC) detection of IL-6, which will eliminate the conventional costly, time-consuming, and complex assays. In this work, we developed a lateral flow assay for colorimetric detection of IL-6, using anti-IL-6 antibodies conjugated to gold nanoparticles (AuNPs) as the detection probes. Silver amplification technique was incorporated with the newly developed assay in order to enhance the obtained colorimetric signals, allowing sensitive detection of IL-6 in human serum in the desired physiological ranges (i.e., 5–1000 pg/mL). A limit of detection of 5 pg/mL could be achieved for IL-6 detection in serum with the amplification step which was not achievable in the standard assay. The corresponding specificity and reproducibility tests were all preformed to confirm the reliability of this assay for quantitative measurement of IL-6 in a POC manner.

Evaluation of a novel immunochromatographic assay using silver amplification technology for detection of Mycoplasma pneumoniae from throat swab samples in pediatric patients

Objectives Mycoplasma pneumoniae is one of the common causative pathogens of community-acquired respiratory tract infections mainly in children and young adults. Rapid and accurate diagnostic techniques for identifying the causative pathogen would be useful for initiating treatment with an appropriate antibiotic. The purpose of the present study was to evaluate the sensitivity and specificity of a novel immunochromatographic assay using silver amplification technology using FUJI DRI-CHEM IMMUNO AG2 and FUJI DRI-CHEM IMMUNO AG cartridge Myco (FUJIFILM Co., Tokyo, Japan) for detection of M. pneumoniae. Methods Throat swab samples were collected from 170 pediatric patients who were diagnosed with bronchitis or pneumonia. The silver amplification immunochromatographic (SAI) assay was performed using these samples and the results were compared with those of real-time PCR. The time required for the SAI assay is approximately 20 min (5 min for sample preparation and 15 min for waiting time after starting the assay). Results The sensitivity and specificity of the SAI assay for detection of M. pneumoniae were 85.2 and 99.1%, respectively, and the assay showed positive and negative predictive values of 98.1 and 92.3%, respectively, compared with the results of real-time PCR. The diagnostic accuracy was 94.1%. Conclusions FUJI DRI-CHEM IMMUNO AG2 and FUJI DRI-CHEM IMMUNO AG cartridge Myco are appropriate for clinical use. The optimal timing of this assay is five days or more after the onset of M. pneumoniae infection. However, PCR or other molecular methods are superior, especially with regard to sensitivity and negative predictive value.

SARS-CoV-2 antigen rapid diagnostic test enhanced with silver amplification technology

Rapid diagnosis of COVID-19 is essential for instituting measures to prevent viral spread. SARS-CoV-2 antigen rapid diagnostic test (Ag-RDT) based on lateral flow immunochromatography assay (LFIA) principle can visually indicate the presence of SARS-CoV-2 antigens as a band. Ag-RDT is clinically promising as a point-of-care testing because it can give results in a short time without the need for special equipment. Although various antigen capture LFIAs are now available for rapid diagnosis for SARS-CoV-2 infection, they face the problems of low sensitivity. We have previously developed highly specific monoclonal antibodies (mAb) against SARS-CoV-2 nucleocapsid protein (NP) and in this study, we have employed these mAbs to develop a new LFIA that can detect SARS-CoV-2 NP in nasopharyngeal swab samples with higher sensitivity by combining them with silver amplification technology. We also compared the performance of our Ag-RDT against the commercially available Ag-RDTs using clinical samples to find that our newly developed LFIA performed best among tested, highlighting the superiority of silver amplification technology.