Development and Clinical Validation of a Hook Effect-Based Lateral Flow Immunoassay Sensor for Cerebrospinal Fluid Leak Detection.

BACKGROUND AND OBJECTIVES: Rapid detection of cerebrospinal fluid (CSF) leaks is vital for patient recovery after spinal surgery. However, distinguishing CSF-specific transferrin (TF) from serum TF using lateral flow immunoassays (LFI) is challenging due to their structural similarities. This study aims to develop a novel point-of-care diagnostic assay for precise CSF leak detection by quantifying total TF in both CSF and serum. METHODS: Capitalizing on the substantial 100-fold difference in TF concentrations between CSF and serum, we designed a diagnostic platform based on the well-known "hook effect" resulting from excessive analyte presence. Clinical samples from 37 patients were meticulously tested using the novel LFI sensor, alongside immunofixation as a reference standard. RESULTS: The hook effect-based LFI sensor exhibited outstanding performance, successfully discriminating positive clinical CSF samples from negative ones with remarkable statistical significance (positive vs negative t-test; P = 1.36E-05). This novel sensor achieved an impressive 100% sensitivity and 100% specificity in CSF leak detection, demonstrating its robust diagnostic capabilities. CONCLUSION: In conclusion, our study introduces a rapid, highly specific, and sensitive point-of-care test for CSF leak detection, harnessing the distinctive TF concentration profile in CSF compared with serum. This novel hook effect-based LFI sensor holds great promise for improving patient outcomes in the context of spinal surgery and postsurgical recovery. Its ease of use and reliability make it a valuable tool in clinical practice, ensuring timely and accurate CSF leak detection to enhance patient care.

One-Step Detection of Vancomycin in Whole Blood Using the Lateral Flow Immunoassay.

Vancomycin (VAN) is an effective antibiotic against Gram-positive bacteria and the first-line therapy to prevent and treat methicillin-resistant Staphylococcus aureus (MRSA) and severe infections. However, low concentrations of VAN can result in resistant strains. High doses of VAN can cause nephrotoxicity and ototoxicity; thus, VAN is a representative drug for which drug monitoring is recommended. Several methods have been proposed to detect VAN. Among them, lateral flow immunoassays (LFIAs) have advantages, such as simple and user-friendly operation, low sample volume requirement, and cost effectiveness. In this study, we developed an LFIA capable of rapid on-site detection such that the VAN concentration in plasma could be monitored within 20 min by a one-step detection process using whole blood without plasma separation. VAN can be detected in whole blood over a wide range of concentrations (20-10,000 ng/mL), and the LFIA reported here has a detection limit of 18 ng/mL. The applicability of the developed LFIA compared to the results of measuring VAN with a commercial enzyme-linked immunosorbent assay kit showed a satisfactory correlation (Spearman's rho, ρ = 0.891). Therefore, the developed LFIA enables rapid and wide-range VAN detection in whole blood and can aid in drug monitoring to evaluate patients' responses to treatment.

Plasmonic Approach to Fluorescence Enhancement of Mesoporous Silica-Coated Gold Nanorods for Highly Sensitive Influenza A Virus Detection Using Lateral Flow Immunosensor.

Rapid diagnostic tests based on the lateral flow immunoassay (LFI) enable early identification of viral infection, owing to simple interpretation, short turnaround time, and timely isolation of patients to minimize viral transmission among communities. However, the LFI system requires improvement in the detection sensitivity to match the accuracy of nucleic acid amplification tests. Fluorescence-based LFIs are more sensitive and specific than absorption-based LFIs, but their performance is significantly affected by fundamental issues related to the quantum yield and photobleaching of fluorophores. Metal-enhanced fluorescence (MEF), which is a plasmonic effect in the vicinity of metallic nanoparticles, can be an effective strategy to improve the detection sensitivity of fluorescence-based LFIs. The key factors for obtaining a strong plasmonic effect include the distance and spectral overlap of the metal and fluorophore in the MEF system. In this study, MEF probes were designed based on core-shell nanostructures employing a gold nanorod core, mesoporous silica shell, and cyanine 5 fluorophore. To optimize the efficiency of MEF probes incorporated on the LFI platform (MEF-LFI), we experimentally and theoretically investigated the distance dependence of plasmonic coupling between cyanine 5 and gold nanorods by adjusting the shell thickness, resulting in significant fluorescence enhancement. The proposed MEF-LFI enabled highly sensitive detection of influenza A virus (IAV) nucleocapsid protein with a detection limit of 0.52 pg mL-1 within 20 min and showed high specificity and accuracy for determining IAV clinical samples. Overall, our findings demonstrate the potential of this method as an effective tool for molecular diagnosis under emergency conditions.

Rapid PCR kit: lateral flow paper strip with Joule heater for SARS-CoV-2 detection.

Polymerase chain reaction (PCR)-based diagnostic kits for point-of-care (POC) testing are highly desirable to prevent the spread of infectious diseases. Here, we demonstrate a rapid PCR testing kit that involves integrating a lateral flow paper strip with a nichrome-based thin film heater. The use of a paper membrane as a PCR-solution container results in fast thermocycling without a cooler because the membrane can contain the solution with a high specific surface area where Joule heating is applied. After PCR, amplified products are simultaneously detected at the lateral flow paper strip with the naked eye. Severe acute respiratory syndrome ß-coronavirus RNA can be detected within 30 min after PCR solution injection. This work reveals that the paper membrane can act as not only a capillary flow channel but also as a promising platform for fast PCR and detection.

Multiple serum biomarkers for predicting suicidal behaviours in depressive patients receiving pharmacotherapy.

BACKGROUND: Predictive values of multiple serum biomarkers for suicidal behaviours (SBs) have rarely been tested. This study sought to evaluate and develop a panel of multiple serum biomarkers for predicting SBs in outpatients receiving a 12-month pharmacotherapy programme for depressive disorders. METHODS: At baseline, 14 serum biomarkers and socio-demographic/clinical characteristics including previous suicidal attempt and present suicidal severity were evaluated in 1094 patients with depressive disorders without a bipolar diagnosis. Of these, 884 were followed for increased suicidal severity and fatal/non-fatal suicide attempt outcomes over a 12-month treatment period. Individual and combined effects of serum biomarkers on these two prospective SBs were estimated using logistic regression analysis after adjustment for relevant covariates. RESULTS: Increased suicidal severity and fatal/non-fatal suicide attempt during the 12-month pharmacotherapy were present in 155 (17.5%) and 38 (4.3%) participants, respectively. Combined cortisol, total cholesterol, and folate serum biomarkers predicted fatal/non-fatal suicide attempt, and these with interleukin-1 beta and homocysteine additionally predicted increased suicidal severity, with clear gradients robust to adjustment (p values < 0.001). CONCLUSIONS: Application of multiple serum biomarkers could considerably improve the predictability of SBs during the outpatient treatment of depressive disorders, potentially highlighting the need for more frequent monitoring and risk appraisal.

Automated cell-type classification combining dilated convolutional neural networks with label-free acoustic sensing.

This study aimed to automatically classify live cells based on their cell type by analyzing the patterns of backscattered signals of cells with minimal effect on normal cell physiology and activity. Our previous studies have demonstrated that label-free acoustic sensing using high-frequency ultrasound at a high pulse repetition frequency (PRF) can capture and analyze a single object from a heterogeneous sample. However, eliminating possible errors in the manual setting and time-consuming processes when postprocessing integrated backscattering (IB) coefficients of backscattered signals is crucial. In this study, an automated cell-type classification system that combines a label-free acoustic sensing technique with deep learning-empowered artificial intelligence models is proposed. We applied an one-dimensional (1D) convolutional autoencoder to denoise the signals and conducted data augmentation based on Gaussian noise injection to enhance the robustness of the proposed classification system to noise. Subsequently, denoised backscattered signals were classified into specific cell types using convolutional neural network (CNN) models for three types of signal data representations, including 1D CNN models for waveform and frequency spectrum analysis and two-dimensional (2D) CNN models for spectrogram analysis. We evaluated the proposed system by classifying two types of cells (e.g., RBC and PNT1A) and two types of polystyrene microspheres by analyzing their backscattered signal patterns. We attempted to discover cell physical properties reflected on backscattered signals by controlling experimental variables, such as diameter and structure material. We further evaluated the effectiveness of the neural network models and efficacy of data representations by comparing their accuracy with that of baseline methods. Therefore, the proposed system can be used to classify reliably and precisely several cell types with different intrinsic physical properties for personalized cancer medicine development.

Absorption-Modulated SiO2@Au Core-Satellite Nanoparticles for Highly Sensitive Detection of SARS-CoV-2 Nucleocapsid Protein in Lateral Flow Immunosensors.

The worldwide spread of coronavirus disease 2019 (COVID-19) highlights the need for rapid, simple, and accurate tests to detect various variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The antigen test, based on the lateral flow immunoassay (LFI), is a suitable "first line of defense" test that enables early identification and timely isolation of patients to minimize viral transmission among communities. However, it is generally less accurate than nucleic acid testing, and its sensitivity needs improvement. Here, a novel rapid detection method is designed to sensitively detect SARS-CoV-2 using isolated gold nanoparticle (AuNP)-assembled SiO2 core-satellite nanoparticles (SiO2@Au CSNPs). Well-grown AuNP satellites in the synthesis of SiO2@Au CSNPs significantly enhanced their light absorption, increased the detection sensitivity, and lowered the detection limit by 2 orders of magnitude relative to conventional gold colloids. The proposed system enabled highly sensitive detection of the SARS-CoV-2 nucleocapsid protein with a detection limit of 0.24 pg mL-1 within 20 min. This is the first study to develop a highly sensitive antigen test using the absorption-modulated SiO2@Au CSNPs. Our findings demonstrate the capacity of this platform to serve as an effective sensing strategy for managing pandemic conditions and preventing the spread of viral infections.

Prospective associations of multimodal serum biomarkers with 12-week and 12-month remission in patients with depressive disorders receiving stepwise psychopharmacotherapy.

Prognostic biomarkers for depression treatment outcomes have yet to be elucidated. This study sought to evaluate whether a multi-modal serum biomarker panel was prospectively associated with 12-week and 12-month remission in outpatients with depressive disorders receiving stepwise psychopharmacotherapy. At baseline, 14 serum biomarkers and socio-demographic/clinical characteristics were evaluated in 1094 patients. They received initial antidepressant monotherapy followed, as required by a protocol of successive alternative pharmacological strategies administered in 3-week steps during the acute (3-12 week) phase (N = 1086), and in 3-month steps during the continuation (6-12 month) phase (N = 884). Remission was defined as a Hamilton Depression Rating Scale score of ≤ 7. Remission was achieved in 490 (45.1%) over the 12-week, and in 625 (70.7%) over the 12-month, treatment periods. Combination scores of four serum biomarkers (high-sensitivity C-reactive protein, interleukin-1 beta, interleukin-6, and leptin) were prospectively associated with 12-week remission; and four (high-sensitivity C-reactive protein, tumor necrosis factor-alpha, interleukin-1 beta, and brain-derived neurotrophic factor) were prospectively associated with 12-month remission in a clear gradient manner (P-values < 0.001) and after adjustment for relevant covariates. These associations were evident after the Step 1 treatment monotherapy but weakened with increasing treatment steps, falling below statistical significance after 4 + treatment steps. Application of combined multiple serum biomarkers, particularly on inflammatory markers, could improve predictability of remission at acute and continuation treatment phases for depressive disorders. Patients with unfavourable biomarkers might require alternative treatment regimes for better outcomes.

Wafer-Scale LSPR Substrate: Oblique Deposition of Gold on a Patterned Sapphire Substrate.

Label-free detection of biomolecules using localized surface plasmon resonance (LSPR) substrates is a highly attractive method for point-of-care (POC) testing. One of the remaining challenges to developing LSPR-based POC devices is to fabricate the LSPR substrates with large-scale, reproducible, and high-throughput. Herein, a fabrication strategy for wafer-scale LSPR substrates is demonstrated using reproducible, high-throughput techniques, such as nanoimprint lithography, wet-etching, and thin film deposition. A transparent sapphire wafer, on which SiO2-nanodot hard masks were formed via nanoimprint lithography, was anisotropically etched by a mixed solution of H2SO4 and H3PO4, resulting in a patterned sapphire substrate (PSS). An LSPR substrate was finally fabricated by oblique deposition of Au onto the PSS, which was then applied to label-free detection of the binding events of biomolecules. To the best of our knowledge, this paper is the first report on the application of the PSS used as an LSPR template by obliquely depositing a metal.

Plasmon color-preserved gold nanoparticle clusters for high sensitivity detection of SARS-CoV-2 based on lateral flow immunoassay.

Lateral flow immunoassays (LFI) have shown great promise for point-of-care (POC) sensing applications, however, its clinical translation is often hindered by insufficient sensitivity for early detection of diseases, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This is mainly due to weak absorption signals of single gold nanoparticles (AuNPs). Here, we developed AuNP clusters that maintain the red color of isolated individual AuNPs, but increase the colorimetric readout to improve the detection sensitivity. The plasmon color-preserved (PLASCOP) AuNP clusters is simply made by mixing streptavidin-coated AuNP core with satellite AuNPs coated with biotinylated antibodies. The biotinylated antibody-streptavidin linker forms a gap size over 15 nm to avoid plasmon coupling between AuNPs, thus maintaining the plasmonic color while increasing the overall light absorption. LFI sensing using PLASCOP AuNP clusters composed of 40 nm AuNPs showed a high detection sensitivity for SARS-CoV-2 nucleocapsid proteins with a limit of detection (LOD) of 0.038 ng mL-1, which was 23.8- and 5.9-times lower value than that of single 15 nm and 40 nm AuNP conjugates, respectively. The PLASCOP AuNP clusters-based LFI sensing also shows good specificity for SARS-CoV-2 nucleocapsid proteins from other influenza and coronaviruses. In a clinical feasibility test, we demonstrated that SARS-CoV-2 particles spiked in human saliva could be detected with an LOD of 54 TCID50 mL-1. The developed PLASCOP AuNP clusters are promising colorimetric sensing reporters that present improved sensitivity in LFI sensing for broad POC sensing applications beyond SARS-CoV-2 detection.

Reagent Filming for Universal Point-of-Care Diagnostics.

Simplifying assays while maintaining the robustness of reagents is a challenge in diagnostics. This problem is exacerbated when translating quality diagnostic assays to developing countries that lack resources and infrastructure such as trained health workers, high-end equipment, and cold-chain systems. To solve this problem, in this study, a simple solution that films assay reagents to simplify the operation of diagnostic assays and preserve the stability of diagnostic reagents without using cold chains is presented. A polyvinyl-alcohol-based water-soluble film is used to encapsulate premeasured and premixed reagents. The reagent film, produced through a simple and scalable cast-drying process, provides a glassy inner matrix with abundant hydroxyl groups that can stabilize various reagents (ranging from chemicals to biological materials) by restricting molecular mobility and generating hydrogen bonds. The reagent film is applied to an enzymatic glucose assay, a high-sensitivity immunoassay for cardiac troponin, and a molecular assay for viral RNA detection, to test its practicability and universal applicability. The film-based assays result in excellent analytical/diagnostic performance and stable long-term reagent storage at elevated temperatures (at 25 or 37 °C, for six months), demonstrating clinical readiness. This technology advances the development and distribution of affordable high-quality diagnostics to resource-limited regions.

Investigation of displacement of intracranial electrode induced by focused ultrasound stimulation.

Transcranial focused ultrasound (tFUS) is an emerging neuromodulation technique to modulate brain activity non-invasively with high spatial specificity and focality. Given the influence of tFUS on brain activity, combining tFUS with multi-channel intracranial electrophysiological recordings enables monitoring of the activity of large populations of neurons with high temporal resolution. However, the physical interactions between tFUS and the electrode may affect a reliable assessment of neuronal activity, which remains poorly understood. In this paper, high-frequency ultrasound (HFUS) system was developed and integrated into tFUS neuromodulation system. The performance of the HFUS-based displacement tracking and analysis was evaluated by the theoretical analysis in the literature. The effects of various pressure levels on the displacements of the silicon-based microelectrode array in ex vivo brain tissue were investigated. The developed approach was capable of tracking and measuring the motion of a solid sphere in a tissue-mimicking phantom and measured displacements were comparable to theoretical predictions. The significant changes in the averaged peak displacements of the microelectrode array in ex vivo brain were observed with a pulse duration of 200 µs and a peak-to-peak pressure from 131 kPa at a center frequency of 500 kHz compared with the values from the negative control group. The present results demonstrate the relationship between several pressure levels and displacements of the microelectrode array in ex vivo brain through the developed approach. This approach can be used to determine a vibration-free threshold of ultrasound parameters in multi-channel intracranial recordings for a reliable assessment of electrophysiological activities of living neurons.

Advanced trap lateral flow immunoassay sensor for the detection of cortisol in human bodily fluids.

Paper-based biosensors based on lateral flow immunoassay (LFI) are promising candidates for POC diagnosis because of their ease of use and rapid target detection. However, the low sensitivity of LFI limits its application, and signal amplification has been used in numerous studies to increase its sensitivity. We developed an advanced trap LFI (α-trapLFI), a simple-to-use sensor, with an additional step for signal amplification. Here, signal amplification is automatically implemented following delayed release of enhancement solution induced by water-soluble polyvinyl alcohol tape. As the polyvinyl alcohol tape is exposed to water, its polymer structure is perturbed (within 5 min), allowing ions to pass through. This new sensor was designed to have a short time delay between the flow of solutions used for the immunoassay and signal amplification. The α-trapLFI was subsequently used to detect cortisol with high sensitivity (9.1 pg∙mL-1) over a broad detection range (0.01-1000 ng∙mL-1) in bodily fluids. Furthermore, an excellent correlation was obtained by analyzing 20 human real saliva samples using this sensor and a conventional ELISA (R2 = 0.90). The new sensor will be helpful in detecting various small molecules for simple, rapid, and portable POC diagnosis of stress disorders.

A rapid assay provides on-site quantification of tetrahydrocannabinol in oral fluid.

Tetrahydrocannabinol (THC), the primary psychoactive ingredient of cannabis, impairs cognitive and motor function in a concentration-dependent fashion. Drug testing is commonly performed for employment and law enforcement purposes; however, available tests produce low-sensitive binary results (lateral flow assays) or have long turnaround (gas chromatography­mass spectrometry). To enable on-site THC quantification in minutes, we developed a rapid assay for oral THC analysis called EPOCH (express probe for on-site cannabis inhalation). EPOCH features distinctive sensor design such as a radial membrane and transmission optics, all contained in a compact cartridge. This integrated approach permitted assay completion within 5 min with a detection limit of 0.17 ng/ml THC, which is below the regulatory guideline (1 ng/ml). As a proof of concept for field testing, we applied EPOCH to assess oral fluid samples from cannabis users (n = 43) and controls (n = 43). EPOCH detected oral THC in all specimens from cannabis smokers (median concentration, 478 ng/ml) and THC-infused food consumers. Longitudinal monitoring showed a fast drop in THC concentrations within the first 6 hours of cannabis smoking (half-life, 1.4 hours).

Paper-Based Airborne Bacteria Collection and DNA Extraction Kit.

The critical risk from airborne infectious diseases, bio-weapons, and harmful bacteria is currently the highest it has ever been in human history. The requirement for monitoring airborne pathogens has gradually increased to defend against bioterrorism or prevent pandemics, especially via simple and low-cost platforms which can be applied in resource-limited settings. Here, we developed a paper-based airborne bacteria collection and DNA extraction kit suitable for simple application with minimal instruments. Airborne sample collection and DNA extraction for PCR analysis were integrated in the paper kit. We created an easy-to-use paper-based air monitoring system using 3D printing technology combined with an air pump. The operation time of the entire process, comprising air sampling, bacterial cell lysis, purification and concentration of DNA, and elution of the DNA analyte, was within 20 min. All the investigations and optimum settings were tested in a custom-designed closed cabinet system. In the fabricated cabinet system, the paper kit operated effectively at a temperature of 25-35 °C and 30-70% relative humidity for air containing 10-106 CFU Staphylococcus aureus. This paper kit could be applied for simple, rapid, and cost-effective airborne pathogen monitoring.

Neurogenic Flare Response following Image-Guided Focused Ultrasound in the Mouse Peripheral Nervous System in Vivo.

Focused ultrasound (FUS) has been used to non-invasively elicit or inhibit motor neuronal activity in the mouse peripheral nervous system in vivo. However, less is known about whether FUS elicits immune system responses associated with peripheral sensory neuronal activity. In this study, we sought to determine that non-invasive ultrasound image-guided FUS can elicit the neurogenic axon reflex of peripheral nerves in the mouse sciatic nerve. The local vasodilation in the plantar view of the hind paw detected with a high-resolution laser Doppler imager indicated neurogenic flare responses after FUS stimulation. The effects of FUS were compared with control groups, where a distinct pattern of blood flow changes was observed only in FUS-elicited neurogenic flare responses. The findings indicate that image-guided FUS elicits local axon reflexes in vivo with a high degree of specificity and penetration depth.

Electrochemiluminescence-Incorporated Lateral Flow Immunosensors Using Ru(bpy)32+-Labeled Gold Nanoparticles for the Full-Range Detection of Physiological C-Reactive Protein Levels.

C-reactive protein (CRP) is used as a general biomarker for inflammation and infection. During stroke and myocardial infarction, CRP increases and is present in a broad concentration range of 1-500 µg/mL. Therefore, full-range CRP detection is crucial to identify patients who need close follow-up or intensive treatment after a heart attack. Here, we report the first attempt to develop an electrochemiluminescent lateral flow immunosensor (ECL-LFI) that allows full-range CRP detection. Ru(bpy)32+-labeled gold nanoparticles (AuNPs) are used as a CRP-targeting probe and a signal generator; they form sandwich immunocomplexes at the test line of the strip and generate strong ECL emission via a Ru(bpy)32+/tripropylamine system. The ECL-LFI shows high sensitivity in detecting CRP in spiked serum, with a limit of detection of 4.6 pg/mL within 15 min, and a broad detection range of 0.01-1000 ng/mL, which is 2 orders of magnitude broader than that of conventional colorimetric LFI. The clinical usability of the ECL-LFI was evaluated using 30 clinical serum samples (200 ng/mL to 5 mg/mL), which showed a good linear correlation (R2 = 0.9896), with a clinical chemistry analyzer. The results suggest that the ECL-LFI holds great potential for CRP detection in point-of-care diagnostics.

Open-Shell and Closed-Shell Quinoid-Aromatic Conjugated Polymers: Unusual Spin Magnetic and High Charge Transport Properties.

While quinoidal moieties are considered as emerging platforms showing efficient charge transport and interesting open-shell diradical characteristics, whether these properties could be changed by extension to the conjugated polymer structure remains as a fundamental question. Here, we developed and characterized two conjugated polymers incorporating quinoids with different lengths, which have a stable close- and open-shell diradical character, respectively, namely, poly(quinoidal thiophene-thienylene vinylene) (PQuT-TV) and poly(quinoidal bithiophene-thienylene vinylene) (PQuBT-TV). A longer length of a quinoidal core led to enhanced diradical characteristics. Therefore, the longer core length of QuBT was favorable for the formation of an open-shell diradical structure in its monomer and in the quinoidal polymer. PQuBT-TV exhibited high spin characteristics observed by the strong ESR signal, a low band gap, and improved electrochemical stability. On the other hand, as QuT maintained a closed-shell quinoid structure, PQuT-TV exhibited high backbone coplanarity and strong intermolecular interaction, which was beneficial for charge transport and led to high hole mobility (up to 2.40 cm2 V-1 s-1) in organic field-effect transistors. This work successfully demonstrated how the control of the closed/open-shell character of quinoidal building blocks changes charge transport and spin properties of quinoidal conjugated polymers via quinoid-aromatic interconversion.

Reactant/polymer hybrid films on p-n junction photodetectors for self-powered, non-invasive glucose biosensors.

The portability of electronic-based biosensors is limited because of the use of batteries and/or solutions containing reactants such as enzymes for assay, which limits the utility of such biosensors in point-of-care (POC) testing. In this study, we report on the development of a self-powered biosensor composed of only portable components: a reactant-containing poly (ethylene glycol) (PEG) film for the colorimetric assay, and a self-powered n-InGaZnO/p-Si photodetector. The PEG film containing enzymes and color-developing agents was formed on a glass slide by spin coating. The self-powered biosensor was fabricated by placing the hybrid film on the p-n junction photodetector, and applied in non-invasive glucose detection (salivary glucose). Injection of the target-containing solution dissolved the PEG that led to the release of enzymes and color-developing agents, resulting in a colorimetric assay. The colorimetric assay could attenuate the light reaching the photodetector, thus facilitating target concentration verification by measuring the photocurrent. Our self-powered biosensor has two main advantages: (i) all components of the biosensor are portable and (ii) dilution of target concentration is avoided as the reagents are in the PEG film. Therefore, the self-powered biosensor, without solution-phase components, could be highly beneficial for creating portable, sensitive biosensors for POC testing.

Ultrasensitive Detection Platform of Disease Biomarkers Based on Recombinase Polymerase Amplification with H-Sandwich Aptamers.

The detection of trace protein biomarkers is essential in the diagnostic field. Protein detection systems ranging from widely used enzyme-linked immunosorbent assays to simple, inexpensive approaches, such as lateral flow immunoassays, play critical roles in medical and drug research. Despite continuous progress, current systems are insufficient for the diagnosis of diseases that require high sensitivity. In this study, we developed a heterogeneous sandwich-type sensing platform based on recombinase polymerase amplification using DNA aptamers specific to the target biomarker. Only the DNA bound to the target in the form of a heterogeneous sandwich was selectively amplified, and the fluorescence signal of an intercalating dye added before the amplification reaction was detected, thereby enabling high specificity and sensitivity. We applied this method for the detection of protein biomarkers for various infectious diseases including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and observed attomolar-level detection of biomarkers and low cross-reactivity between different viruses. We also confirmed detection efficiency of the proposed method using clinical samples. These results demonstrate that the proposed sensing platform can be used to diagnose various diseases requiring high sensitivity, specificity, and accuracy.