Sensitive detection of respiratory syncytial virus based on a dual signal amplified plasmonic enzyme-linked immunosorbent assay

Overview on the Development of Alkaline-Phosphatase-Linked Optical Immunoassays

The drive to achieve ultrasensitive target detection with exceptional efficiency and accuracy requires the advancement of immunoassays. Optical immunoassays have demonstrated significant potential in clinical diagnosis, food safety, environmental protection, and other fields. Through the innovative and feasible combination of enzyme catalysis and optical immunoassays, notable progress has been made in enhancing analytical performances. Among the kinds of reporter enzymes, alkaline phosphatase (ALP) stands out due to its high catalytic activity, elevated turnover number, and broad substrate specificity, rendering it an excellent candidate for the development of various immunoassays. This review provides a systematic evaluation of the advancements in optical immunoassays by employing ALP as the signal label, encompassing fluorescence, colorimetry, chemiluminescence, and surface-enhanced Raman scattering. Particular emphasis is placed on the fundamental signal amplification strategies employed in ALP-linked immunoassays. Furthermore, this work briefly discusses the proposed solutions and challenges that need to be addressed to further enhance the performances of ALP-linked immunoassays.

Diagnostic plasmonic sensors: opportunities and challenges

The medical fraternity is currently burgeoned and stressed with a huge rush of patients who have inflammatory conditions, metabolite diseases, and cardiovascular diseases. In these circumstances, advanced sensing technologies could have a huge impact on the quality of life of patients. Given plasmonic resonance effects significantly improve the ability to rapidly and accurately detect biological markers, plasmonic technology is harnessed to develop a fast and accurate diagnosis that can provide timely intervention with the diseases and can also aid the recovery process by complementing the therapy stage. In this short review, we provide an overlook of how the field of plasmonic sensing has revolutionized the field of medical diagnostics. This article reviews the fundamentals and development of plasmonics. In addition, we highlight the sensitivity of various SPR and LSPR sensors. The chemistry for functionalizing plasmonic sensors is also discussed. This review also outlines some general suggestions for future directions that we feel might be useful to advance our understanding of the universe or speed up the development of plasmonic sensors in the future.

Advanced Point-of-Care Testing Technologies for Human Acute Respiratory Virus Detection

The ever-growing global threats to human life caused by the human acute respiratory virus (RV) infections have cost billions of lives, created a significant economic burden, and shaped society for centuries. The timely response to emerging RVs could save human lives and reduce the medical care burden. The development of RV detection technologies is essential for potentially preventing RV pandemic and epidemics. However, commonly used detection technologies lack sensitivity, specificity, and speed, thus often failing to provide the rapid turnaround times. To address this problem, new technologies are devised to address the performance inadequacies of the traditional methods. These emerging technologies offer improvements in convenience, speed, flexibility, and portability of point-of-care test (POCT). Herein, recent developments in POCT are comprehensively reviewed for eight typical acute respiratory viruses. This review discusses the challenges and opportunities of various recognition and detection strategies and discusses these according to their detection principles, including nucleic acid amplification, optical POCT, electrochemistry, lateral flow assays, microfluidics, enzyme-linked immunosorbent assays, and microarrays. The importance of limits of detection, throughput, portability, and specificity when testing clinical samples in resource-limited settings is emphasized. Finally, the evaluation of commercial POCT kits for both essential RV diagnosis and clinical-oriented practices is included.

Iodide/metal-organic frameworks (MOF) -mediated signal amplification strategy for the colorimetric detection of H2O2, Cr2O72- and H2S

The analytical methods based on colorimetric detection of various analytes have attracted intensive interest. However, most of them display relatively low sensitivity. Herein, a novel colorimetric strategy based on iodide/metal-organic frameworks (MOF)-mediated amplification was developed for low-cost, naked-eye detection and quantification of H₂O₂,Cr₂O₇^2-, and H₂S. Cu-MOFs could catalyze the oxidation of the colorless peroxidase substrate TMB to produce a blue product. The published researches mainly focused on the immobilization or integration of a macromolecule, such as natural enzymes, to enhance MOFs catalytic abilities. The use of small molecules to improve the catalytic performance of MOFs has rarely reported. Due to the negligible steric hindrance, iodide could easily be adsorbed in the framework pore of MOFs to conduct the synergic catalytic effect, and shows a high catalytic effect. As a result, the catalytic activity of Cu-MOFs was dramatically enhanced, and thus, the nanocatalyst could act as an amplifier system for target detection. The detection limits obtained by the amplified method are 25, 30, and 0.2 nM, respectively, which are about 200-fold lower than that of the unamplified colorimetric assays. The colorimetric strategy developed herein provides a novel system for the detection of low concentrations of analytes in complex biological samples.

Paper-based colorimetric detection of pathogenic bacteria in food through magnetic separation and enzyme-mediated signal amplification on paper disc

Herein, we report a colorimetric sensing system for the detection of highly virulent bacteria, Escherichiacoli O157:H7, in sausage by utilizing magnetic separation and enzyme-mediated signal amplification on paper disc. For magnetic separation, Poly-l-lysine coated starch magnetic particles (PLL@SMPs) were synthesized and utilized for the separation and concentration of the bacteria in sample suspension. Horseradish peroxidase-conjugated antibody (HRP-Antibody) and 3,3',5,5'- tetramethylbenzidine (TMB) were employed for the specific signal amplification in the presence of target bacteria. The synthesized PLL@SMPs showed an excellent capture efficiency (>90%) for the pathogenic bacteria in large volume sample suspension. The intrinsic problems associated with the non-specific binding of sensing components that lead to the high background signal and low sensitivity in colorimetric detection was successfully resolved by employing hyaluronic acid as a blocking agent. The effective separation and concentration of target bacteria by PLL@SMPs and target-specific signal amplification with exceptionally high signal to noise ratio enabled the detection of target bacteria with a detection limit in the single digit regime. The sensing system proposed in this study was successfully used for the detection of the target pathogenic bacteria, E. coli O157:H7, in sausage sample with the limit of detection (LOD) as low as 30.8 CFU/mL with 95% probability. The simple nature of paper-based detection system with a great sensitivity and specificity would provide an effective means of evaluating the safety of food and environmental samples.

Clinical Applications of Visual Plasmonic Colorimetric Sensing

Colorimetric analysis has become of great importance in recent years to improve the operationalization of plasmonic-based biosensors. The unique properties of nanomaterials have enabled the development of a variety of plasmonics applications on the basis of the colorimetric sensing provided by metal nanoparticles. In particular, the extinction of localized surface plasmon resonance (LSPR) in the visible range has permitted the exploitation of LSPR colorimetric-based biosensors as powerful tools for clinical diagnostics and drug monitoring. This review summarizes recent progress in the biochemical monitoring of clinical biomarkers by ultrasensitive plasmonic colorimetric strategies according to the distance- or the morphology/size-dependent sensing modes. The potential of colorimetric nanosensors as point of care devices from the perspective of naked-eye detection is comprehensively discussed for a broad range of analytes including pharmaceuticals, proteins, carbohydrates, nucleic acids, bacteria, and viruses such as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). The practical suitability of plasmonic-based colorimetric assays for the rapid visual readout in biological samples, considering current challenges and future perspectives, is also reviewed.

A Method To Prevent SARS-CoV-2 IgM False Positives in Gold Immunochromatography and Enzyme-Linked Immunosorbent Assays

We set out to investigate the interference factors that led to false-positive novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM detection results using gold immunochromatography assay (GICA) and enzyme-linked immunosorbent assay (ELISA) and the corresponding solutions. GICA and ELISA were used to detect SARS-CoV-2 IgM in 86 serum samples, including 5 influenza A virus (Flu A) IgM-positive sera, 5 influenza B virus (Flu B) IgM-positive sera, 5 Mycoplasma pneumoniae IgM-positive sera, 5 Legionella pneumophila IgM-positive sera, 6 sera of HIV infection patients, 36 rheumatoid factor IgM (RF-IgM)-positive sera, 5 sera from hypertensive patients, 5 sera from diabetes mellitus patients, and 14 sera from novel coronavirus infection disease 19 (COVID-19) patients.

We set out to investigate the interference factors that led to false-positive novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM detection results using gold immunochromatography assay (GICA) and enzyme-linked immunosorbent assay (ELISA) and the corresponding solutions. GICA and ELISA were used to detect SARS-CoV-2 IgM in 86 serum samples, including 5 influenza A virus (Flu A) IgM-positive sera, 5 influenza B virus (Flu B) IgM-positive sera, 5 Mycoplasma pneumoniae IgM-positive sera, 5 Legionella pneumophila IgM-positive sera, 6 sera of HIV infection patients, 36 rheumatoid factor IgM (RF-IgM)-positive sera, 5 sera from hypertensive patients, 5 sera from diabetes mellitus patients, and 14 sera from novel coronavirus infection disease 19 (COVID-19) patients. The interference factors causing false-positive reactivity with the two methods were analyzed, and the urea dissociation test was employed to dissociate the SARS-CoV-2 IgM-positive serum using the best dissociation concentration. The two methods detected positive SARS-CoV-2 IgM in 22 mid-to-high-level-RF-IgM-positive sera and 14 sera from COVID-19 patients; the other 50 sera were negative. At a urea dissociation concentration of 6 mol/liter, SARS-CoV-2 IgM results were positive in 1 mid-to-high-level-RF-IgM-positive serum and in 14 COVID-19 patient sera detected using GICA. At a urea dissociation concentration of 4 mol/liter and with affinity index (AI) levels lower than 0.371 set to negative, SARS-CoV-2 IgM results were positive in 3 mid-to-high-level-RF-IgM-positive sera and in 14 COVID-19 patient sera detected using ELISA. The presence of RF-IgM at mid-to-high levels could lead to false-positive reactivity of SARS-CoV-2 IgM detected using GICA and ELISA, and urea dissociation tests would be helpful in reducing SARS-CoV-2 IgM false-positive results.

Nanoparticles for Signaling in Biodiagnosis and Treatment of Infectious Diseases

Advances in nanoparticle-based systems constitute a promising research area with important implications for the treatment of bacterial infections, especially against multidrug resistant strains and bacterial biofilms. Nanosystems may be useful for the diagnosis and treatment of viral and fungal infections. Commercial diagnostic tests based on nanosystems are currently available. Different methodologies based on nanoparticles (NPs) have been developed to detect specific agents or to distinguish between Gram-positive and Gram-negative microorganisms. Also, biosensors based on nanoparticles have been applied in viral detection to improve available analytical techniques. Several point-of-care (POC) assays have been proposed that can offer results faster, easier and at lower cost than conventional techniques and can even be used in remote regions for viral diagnosis. Nanoparticles functionalized with specific molecules may modulate pharmacokinetic targeting recognition and increase anti-infective efficacy. Quorum sensing is a stimuli-response chemical communication process correlated with population density that bacteria use to regulate biofilm formation. Disabling it is an emerging approach for combating its pathogenicity. Natural or synthetic inhibitors may act as antibiofilm agents and be useful for treating multi-drug resistant bacteria. Nanostructured materials that interfere with signal molecules involved in biofilm growth have been developed for the control of infections associated with biofilm-associated infections.