Lateral flow immunoassay based on surface-enhanced Raman scattering using pH-induced phage-templated hierarchical plasmonic assembly for point-of-care diagnosis of infectious disease

In vitro diagnosis based on SERS-LFIA: research hotspots, increase sensitivities, combined detection, multimodal detection and related patents

In recent years, the SERS-LFIA platform has gained significant traction in in vitro diagnostics. However, a comprehensive review of its advancements and applications is still lacking. This review first employing a bibliometric approach to analyze research trends. It then outlines strategies to enhance sensitivity, focusing on Raman reporter molecules, SERS tags, coupling methods, detection instruments. Additionally, the review explores the use of SERS-LFIA for diagnosing multiple disease biomarkers, highlighting its potential to improve diagnostic accuracy. The review also synthesizes the application of multimodal SERS-LFIA technology, integrating signals such as colorimetric, magnetic, photothermal, fluorescent, and catalytic modalities. This approach enhances detection versatility and broadens diagnostic capabilities. Furthermore, it examines the current patent landscape, providing insights into the technology's commercial and technological progress. Lastly, the review discusses ongoing challenges, including stability and reproducibility and quantitative detection, while suggesting directions for future research. In summary, this review consolidates the latest advancements in SERS-LFIA technology for in vitro diagnostics over the past decade. Anticipated to furnish a robust scientific foundation and theoretical underpinning for the advancement of SERS-LFIA technology, this endeavor aims to enhance its efficacy in clinical diagnostics.

Field-Deployable Detection of Genetically Modified Organisms with an Integrated Method of Loop-Mediated Isothermal Amplification and CRISPR/FnCas12a

The detection of genetically modified organisms (GMOs) is crucial for regulatory compliance and consumer safety. This study presents a novel method combining loop-mediated isothermal amplification (LAMP) with CRISPR/Cas12a cleavage, termed Cas-pfLAMP, for sensitive and specific GMO detection. We developed assays for three GM events: maize DBN9936 and MON810 and soybean GTS40-3-2. By incorporating a universal protospacer adjacent motif (PAM) sequence into LAMP primers, we overcame the limitations of PAM site dependence. The Cas-pfLAMP assays demonstrated high specificity and sensitivity, with limits of detection as low as 10-12 copies per reaction. Furthermore, we developed a point-of-care testing platform integrating rapid DNA extraction, Cas-pfLAMP, and lateral flow strips for on-site GMO detection. This platform achieved comparable sensitivity to qPCR, detecting GM contents as low as 0.1% in simulated samples within 40 min. The Cas-pfLAMP method offers the advantages of PAM site independence, high specificity and sensitivity, and suitability for field testing without specialized equipment. This approach represents a promising new generation of GMO detection methods with potential applications in various scenarios.

Hot Nanogap Networks-In-Triangular Nanoframes: A Strategy for Positioning Adsorbates Near Hot Spots

This study reports the synthesis of plasmonic hot nanogap networks-in-triangular nanoframes (NITNFs), featuring narrow intraparticle nanogap networks embedded within triangular nanoframes. Starting from Au nanotriangles, Pt NITNFs are synthesized through a cascade reaction involving simultaneous Pt deposition and Au etching in a one-pot process. The Pt NITNFs are then transformed into plasmonically active Au NITNFs via Au coating. The near-field focusing capabilities of the Au NITNFs are tailored by fine-tuning the void area fraction down to 3.9%, resulting in the formation of narrow nanogaps of ≈1 nm. This optimization enables the successful implementation of single-particle surface-enhanced Raman scattering (SERS) measurements. Then, monolayer Au NITNFs films on Al substrates are prepared, which enabled weakly adsorbing species to be positioned close to the hot spots of the NITNFs by anchoring them to the underlying Al substrates. As a representative sensing application, the SERS-based detection of gas-phase dimethyl methylphosphonate (DMMP) using a film of plasmonic NITNFs on an Al substrate exhibits outstanding performances, achieving a limit of detection of 5 ppm and a detection time of 120 s.

Sensitive Colorimetric Lateral Flow Assays Enabled by Platinum-Group Metal Nanoparticles with Peroxidase-Like Activities

The last several decades have witnessed the success and popularity of colorimetric lateral flow assay (CLFA) in point-of-care testing. Driven by increasing demand, great efforts have been directed toward enhancing the detection sensitivity of CLFA. Recently, platinum-group metal nanoparticles (PGM NPs) with peroxidase-like activities have emerged as a type of promising colorimetric labels for enhancing the sensitivity of CLFA. By incorporating a simple and rapid post-treatment process, the PGM NP-based CLFAs are orders of magnitude more sensitive than conventional gold nanoparticle-based CLFAs. In this perspective, the study begins with introducing the design, synthesis, and characterization of PGM NPs with peroxidase-like activities. The current techniques for surface modification of PGM NPs are then discussed, followed by operation and optimization of PGM NP-based CLFAs. Afterward, opinions are provided on the social impact of PGM NP-based CLFAs. Lastly, this perspective is concluded with an outlook of future research directions in this emerging field, where the challenges and opportunities are discussed.

Magnetic-plasmonic blackbody enhanced lateral flow immunoassay of staphylococcal enterotoxin B

Staphylococcal enterotoxin B (SEB) in food is a serious health risk, making rapid and accurate detection methods essential. Herein, we synthesized a magnetic plasmonic blackbody, Fe3O4@Au/PDA, by coating a gold/polydopamine (Au/PDA) layer onto an Fe3O4 core. This Fe3O4@Au/PDA exhibits broadband absorption, excellent stability, and rapid magnetic response, making it ideal for use as a magnetic separation tool and colorimetric signal amplifier. We integrated Fe3O4@Au/PDA into a lateral flow immunoassay (LFIA) for ultrasensitive SEB detection, combining magnetic enrichment with enhanced colorimetric signal output. The Fe3O4@Au/PDA-based LFIA achieved a detection limit of 0.19 ng/mL, approximately 41 times lower than traditional gold nanoparticle-based LFIA. Its real-world applicability was tested in various food samples (milk, milk powder, apple juice, and lettuce) with recoveries between 82.4 % and 111.2 % and a coefficient of variation below 12.6 %. Collectively, the designed Fe3O4@Au/PDA shows great promise as a novel multifunctional signal amplification label, advancing the design and development of ultrasensitive LFIA for various fields, such as food safety detection.

Structured protein probes modified with selenium nanoparticle for 1-minute measurement of SARS-CoV-2 antigen

Conventional point-of-care lateral flow immunoassays are characterized by an antibody-tagged probe irregular coupling that can limit sensitivity and require a long assay's time. We synthesized polyethylene glycol-modified selenium nanoparticles (PEG-SeNPs) by template method and developed a strategy to set antibody probes targeted and orderly by using PEG-SeNPs. Synthesized PEG-SeNPs with high stability could immobilize antibodies in the "stand-up" orientation, resulting in a faster detection time of less than 1 min by direct observer visualization without instruments or equipment. Results showed that SARS-CoV-2 antibody could be systematically structured on the chip, resulting in a detection limit of 10 pg/mL, significantly higher than conventional chips. The new device has been validated on 192 clinical samples and we found 100% negative coincidence, 93.94% positive coincidence, and 95.83% overall coincidence with reverse transcriptional PCR test. The orderly arrayed probe's stability allowed to detect throat swabs, saliva, serum, fingertip blood samples, and mutant strains without cross-reactivity with common respiratory viruses or pathogenic strains, demonstrating promising potential for a universal colorimetric platform for ultrafast field-deployable diagnostics.

Integration of DNA-Decorated Hapten in Emergency Immunoassays for Antibody and Small-Molecule Detection: A Review

DNA-decorated hapten (DDH)-based immunoassays have emerged, demonstrating supreme advantages in sensing applications because of their excellent sensitivity, specificity, and reliability. DDH combines both a recognition element (hapten) and a signal transduction element (DNA portion) with its highly programmable DNA structure enabling the trigger of signal transduction following a recognition event, thereby introducing a novel signal transduction mechanism to immunoassays. In this review, we provide a critical overview of recent research in the DDH-based immunoassays, which are designed to detect specific small molecules and antibodies. On the basis of the following events after binding of antibodies to DDH, the reported studies involved with DDH-based immunoassays can be categorized into three groups: (i) DDH-based immunoassay based on DNA conformational switches induced by antibody binding, (ii) DDH-based immunoassay based on co-localization of nucleic acids induced by antibody binding, and (iii) DDH-based immunoassay based on antibody steric hindrance. We also focus on several fundamental elements of DDH-based immunoassays, including the designed DNA structure, principles of signal transformation, and platform of DDH-based immunoassays. Then, the representative applications of DDH-based immunoassays in areas such as food safety, medical diagnostics, and environmental monitoring as well as the challenges and perspectives of DDH-based immunoassays are also explored.

MXene Bimetallic Coating Synergistic Enhanced Colorimetric-Raman Dual Signal-Based Immunochromatographic Assay for Advancing Detection Performance

Herein, a three-dimensional thin film-like multifunctional MXene bimetallic coating material (Ti3C2@Au-Ag) with strong color intensity, high surface-enhanced Raman scattering (SERS) activity, and strong antibody affinity (1.00 × 108 M-1) was prepared. It was the first time that Ti3C2@Au-Ag-based colorimetric-SERS dual-signal immunochromatographic assay (ICA) was developed for the detection of dexamethasone, achieving the limits of detection of 0.0089, 0.14, and 0.084 μg/kg for milk, beef, and pork in colorimetric mode and 0.0015, 0.060, and 0.075 μg/kg in SERS mode. It was up to 200-fold more sensitive than the reported ICAs. The recoveries were 82.0%-112.6%, and the coefficients of variation were 1.4%-13.7%. The Ti3C2@Au-Ag-ICA was verified by LC-MS/MS in the application on 30 real samples with a correlation coefficient greater than 0.98. This study can provide efficient theoretical and practical value for the development of a colorimetric-SERS dual-signal immunoassay platform.

Enhanced Point-of-Care SARS-CoV-2 Detection: Integrating RT-LAMP with Microscanning

The COVID-19 pandemic has highlighted the urgent need for rapid and accurate diagnostic methods for various infectious diseases, including SARS-CoV-2. Traditional RT-PCR methods, while highly sensitive and specific, require complex equipment and skilled personnel. In response, we developed an integrated RT-LAMP-MS assay, which combines rapid reverse transcription loop-mediated isothermal amplification (RT-LAMP) with microscanning (MS) technology for detecting SARS-CoV-2. The assay uses magnesium pyrophosphate formed during LAMP amplification as a visual marker, allowing direct observation via microscopy without the need for additional chemical indicators or probes. For the SARS-CoV-2/IC RT-LAMP-MS assay, the sample-LAMP reagent mixture was added to a microchip with SARS-CoV-2 primers and internal controls, then incubated at 62 °C for 30 min in a heat block, followed by amplification analysis using a microscanner. In clinical tests, the RT-LAMP-MS assay showed 99% sensitivity and 100% specificity, which is identical to the RT-LAMP results and comparable to the commercial AllplexTM SARS-CoV-2 assay results. Additionally, the limit of detection (LOD) was determined to be 10-1 PFU mL-1 (dynamic range: 103~10-1 PFU mL-1). The assay delivers results in 30 min, uses low-cost equipment, and demonstrates 100% reproducibility in repeated tests, making it suitable for point-of-care use in resource-limited settings.

Recent advances towards point-of-care devices for fungal detection: Emphasizing the role of plasmonic nanomaterials in current and future technologies

Fungal infections are a significant global health problem, particularly affecting individuals with weakened immune systems. Moreover, as uncontrolled antibiotic and immunosuppressant use increases continuously, fungal infections have seen a dramatic increase, with some strains developing antibiotic resistance. Traditional approaches to identifying fungal strains often rely on morphological characteristics, thus owning limitations, such as struggles in identifying several strains or distinguishing between fungal strains with similar morphologies. This review explores the multifaceted impact of fungi infections on individuals, healthcare providers, and society, highlighting the often-underestimated economic burden and healthcare implications of these infections. In light of the serious constraints of traditional fungal identification methods, this review discusses the potential of plasmonic nanoparticle-based biosensors for fungal infection identification. These biosensors can enable rapid and precise fungal pathogen detection by exploiting several readout approaches, including various spectroscopic techniques, colorimetric and electrochemical assays, as well as lateral-flow immunoassay methods. Moreover, we report the remarkable impact of plasmonic Lab on a Chip technology and microfluidic devices, as they recently emerged as a class of advanced biosensors. Finally, we provide an overview of smartphone-based Point-of-Care devices and the associated technologies developed for detecting and identifying fungal pathogens.

Hierarchical Nanobiosensors at the End of the SARS-CoV-2 Pandemic

Nanostructures have played a key role in the development of different techniques to attack severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Some applications include masks, vaccines, and biosensors. The latter are of great interest for detecting diseases since some of their features allowed us to find specific markers in secretion samples such as saliva, blood, and even tears. Herein, we highlight how hierarchical nanoparticles integrated into two or more low-dimensional materials present outstanding advantages that are attractive for photonic biosensing using their nanoscale functions. The potential of nanohybrids with their superlative mechanical characteristics together with their optical and optoelectronic properties is discussed. The progress in the scientific research focused on using nanoparticles for biosensing a variety of viruses has become a medical milestone in recent years, and has laid the groundwork for future disease treatments. This perspective analyzes the crucial information about the use of hierarchical nanostructures in biosensing for the prevention, treatment, and mitigation of SARS-CoV-2 effects.