CRISPR-Based Multiplex Detection of Human Papillomaviruses for One-Pot Point-of-Care Diagnostics

The World Health Organization's global initiative toward eliminating high-risk Human Papillomavirus (hrHPV)-related cancers recommends DNA testing over visual inspection in all settings for primary cancer screening and HPV eradication by 2100. However, multiple hrHPV types cause different types of cancers, and there is a pressing need for an easy-to-use, multiplex point-of-care diagnostic platform for detecting different hrHPV types. Recently, CRISPR-Cas systems have been repurposed for point-of-care detection. Here, we established a CRISPR-Cas multiplexed diagnostic assay (CRISPRD) to detect cervical cancer-causing hrHPVs in one reaction (one-pot assay). We harnessed the compatibility of thermostable AapCas12b, TccCas13a, and HheCas13a nucleases with isothermal amplification and successfully detected HPV16 and HPV18, along with an internal control in a single-pot assay with a limit of detection of 10 copies and 100% specificity. This platform offers a rapid and practical solution for the multiplex detection of hrHPVs, which may facilitate large-scale hrHPV point-of-care screening. Furthermore, the CRISPRD platform programmability enables it to be adapted for the multiplex detection of any two nucleic acid biomarkers as well as internal control.

Pooled Pharyngeal, Rectal, and Urine Specimens for the Point-of-Care Detection of Chlamydia trachomatis and Neisseria gonorrhoeae by Lay Providers in Key Population-Led Health Services in Thailand

Routine testing for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) in people with heightened risk is lacking in Thailand. This study aimed to assess the performance of the Cepheid Xpert CT/NG assay, conducted by key population (KP) lay providers, for CT and NG detection on single-site and pooled specimens from the pharynx, rectum, and urine. Between August and October 2019, 188 men who have sex with men and 11 transgender women were enrolled. Participants collected urine specimens while trained KP lay providers obtained pharyngeal and rectal swabs. Compared to single-site testing with the Abbott RealTime CT/NG assay by medical technologists, the Xpert assay missed one pharyngeal NG infection out of 199 single-site specimens, giving a 93.3% sensitivity for pharyngeal NG and one missed pharyngeal NG infection out of fifty pooled specimens, giving an 88.9% sensitivity for pharyngeal NG. There was no discrepancy between the two assays for CT detection. The Cohen's Kappa coefficient of pooled specimen testing by the Xpert was 0.93 for NG and 1 for CT when compared to single-site testing by Abbott. Implementing pooled specimen testing by KP lay providers can be a cost-saving strategy to enhance the uptake of CT/NG services for populations facing increased risk.

Portable Surface Plasmon Resonance Detector for COVID-19 Infection

Methods based on nucleic acid detection are currently the most commonly used technique in COVID-19 diagnostics. Although generally considered adequate, these methods are characterised by quite a long time-to-result and the necessity to prepare the material taken from the examined person-RNA isolation. For this reason, new detection methods are being sought, especially those characterised by the high speed of the analysis process from the moment of sampling to the result. Currently, serological methods of detecting antibodies against the virus in the patient's blood plasma have attracted much attention. Although they are less precise in determining the current infection, such methods shorten the analysis time to several minutes, making it possible to consider them a promising method for screening tests in people with suspected infection. The described study investigated the feasibility of a surface plasmon resonance (SPR)-based detection system for on-site COVID-19 diagnostics. A simple-to-use portable device was proposed for the fast detection of anti-SARS-CoV-2 antibodies in human plasma. SARS-CoV-2-positive and -negative patient blood plasma samples were investigated and compared with the ELISA test. The receptor-binding domain (RBD) of spike protein from SARS-CoV-2 was selected as a binding molecule for the study. Then, the process of antibody detection using this peptide was examined under laboratory conditions on a commercially available SPR device. The portable device was prepared and tested on plasma samples from humans. The results were compared with those obtained in the same patients using the reference diagnostic method. The detection system is effective in the detection of anti-SARS-CoV-2 with the detection limit of 40 ng/mL. It was shown that it is a portable device that can correctly examine human plasma samples within a 10 min timeframe.

Conductive Thread-Based Immunosensor for Pandemic Influenza A (H1N1) Virus Detection

Infectious agents such as viruses pose significant threats to human health, being transmitted via direct contact as well as airborne transmission without direct contact, thus requiring rapid detection to prevent the spread of infectious diseases. In this study, we developed a conductive thread-based immunosensor (CT-IS), a biosensor to easily detect the presence of airborne viruses. CT-IS utilizes an antibody that specifically recognizes the HA protein of the pandemic influenza A (pH1N1) virus, which is incorporated into the conductive thread. The antigen-antibody interaction results in increased strain on the conductive thread in the presence of the pH1N1 virus, resulting in increased electrical resistance of the CT-IS. We evaluated the performance of this sensor using the HA protein and the pH1N1 virus, in addition to samples from patients infected with the pH1N1 virus. We observed a significant change in resistance in the pH1N1-infected patient samples (positive: n = 11, negative: n = 9), whereas negligible change was observed in the control samples (patients not infected with the pH1N1 virus; negative). Hence, the CT-IS is a lightweight fiber-type sensor that can be used as a wearable biosensor by combining it with textiles, to detect the pH1N1 virus in a person's vicinity.

Large-Scale Functionalized Metasurface-Based SARS-CoV-2 Detection and Quantification

Plasmonic metasurfaces consist of metal-dielectric interfaces that are excitable at background and leakage resonant modes. The sharp and plasmonic excitation profile of metal-free electrons on metasurfaces at the nanoscale can be used for practical applications in diverse fields, including optoelectronics, energy harvesting, and biosensing. Currently, Fano resonant metasurface fabrication processes for biosensor applications are costly, need clean room access, and involve limited small-scale surface areas that are not easy for accurate sample placement. Here, we leverage the large-scale active area with uniform surface patterns present on optical disc-based metasurfaces as a cost-effective method to excite asymmetric plasmonic modes, enabling tunable optical Fano resonance interfacing with a microfluidic channel for multiple target detection in the visible wavelength range. We engineered plasmonic metasurfaces for biosensing through efficient layer-by-layer surface functionalization toward real-time measurement of target binding at the molecular scale. Further, we demonstrated the quantitative detection of antibodies, proteins, and the whole viral particles of SARS-CoV-2 with a high sensitivity and specificity, even distinguishing it from similar RNA viruses such as influenza and MERS. This cost-effective plasmonic metasurface platform offers a small-scale light-manipulation system, presenting considerable potential for fast, real-time detection of SARS-CoV-2 and pathogens in resource-limited settings.

A Universal Fluorescent Immunochromatography Assay Based on Quantum Dot Nanoparticles for the Rapid Detection of Specific Antibodies against SARS-CoV-2 Nucleocapsid Protein

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the pathogenic agent leading to COVID-19. Due to high speed of transmission and mutation rates, universal diagnosis and appropriate prevention are still urgently needed. The nucleocapsid protein of SARS-CoV-2 is considered more conserved than spike proteins and is abundant during the virus’ life cycle, making it suitable for diagnostic applications. Here, we designed and developed a fluorescent immunochromatography assay (FICA) for the rapid detection of SARS-CoV-2-specific antibodies using ZnCdSe/ZnS QDs-conjugated nucleocapsid (N) proteins as probes. The nucleocapsid protein was expressed in E.coli and purified via Ni-NTA affinity chromatography with considerable concentration (0.762 mg/mL) and a purity of more than 90%, which could bind to specific antibodies and the complex could be captured by Staphylococcal protein A (SPA) with fluorescence displayed. After the optimization of coupling and detecting conditions, the limit of detection was determined to be 1:1.024 × 10⁵ with an IgG concentration of 48.84 ng/mL with good specificity shown to antibodies against other zoonotic coronaviruses and respiratory infection-related viruses (n = 5). The universal fluorescent immunochromatography assay simplified operation processes in one step, which could be used for the point of care detection of SARS-CoV-2-specific antibodies. Moreover, it was also considered as an efficient tool for the serological screening of potential susceptible animals and for monitoring the expansion of virus host ranges.

A Biocatalytic Cascade in an Ultrastable Mesoporous Hydrogen-Bonded Organic Framework for Point-of-Care Biosensing

Herein, we report the first example of using mesoporous hydrogen-bonded organic frameworks (MHOFs) as the protecting scaffold to organize a biocatalytic cascade. The confined microenvironment of MHOFs has robust and large transport channels, allowing the efficient transport of a wide range of biocatalytic substrates. This new MHOF-confined cascade system shows superior activity, extended scope of catalytic substrates, and ultrahigh stability that enables the operation of complex chemical transformations in a porous carrier. In addition, the advantages of MHOF-confined cascades system for point-of-care biosensing are also demonstrated. This study highlights the advantages of HOFs as scaffold for multiple enzyme assemblies, which has huge potential for mimicking complex cellular transformation networks in a controllable manner.

Advances in Biosensors for Continuous Glucose Monitoring Towards Wearables

Continuous glucose monitors (CGMs) for the non-invasive monitoring of diabetes are constantly being developed and improved. Although there are multiple biosensing platforms for monitoring glucose available on the market, there is still a strong need to enhance their precision, repeatability, wearability, and accessibility to end-users. Biosensing technologies are being increasingly explored that use different bodily fluids such as sweat and tear fluid, etc., that can be calibrated to and therefore used to measure blood glucose concentrations accurately. To improve the wearability of these devices, exploring different fluids as testing mediums is essential and opens the door to various implants and wearables that in turn have the potential to be less inhibiting to the wearer. Recent developments have surfaced in the form of contact lenses or mouthguards for instance. Challenges still present themselves in the form of sensitivity, especially at very high or low glucose concentrations, which is critical for a diabetic person to monitor. This review summarises advances in wearable glucose biosensors over the past 5 years, comparing the different types as well as the fluid they use to detect glucose, including the CGMs currently available on the market. Perspectives on the development of wearables for glucose biosensing are discussed.

Quantification of Methotrexate in Human Serum Using Surface-Enhanced Raman Scattering-Toward Therapeutic Drug Monitoring

Therapeutic drug monitoring (TDM) can improve clinical care when using drugs with pharmacokinetic variability and a narrow therapeutic window. Rapid, reliable, and easy-to-use detection methods are required in order to decrease the time of analysis and can also enable TDM in resource-limited settings or even at bedside. Monitoring methotrexate (MTX), an anticancer drug, is critical since it is needed to follow the drug clearance rate and decide how to administer the rescue drug, leucovorin (LV), in order to avoid toxicity and even death. We show that with the optimized nanopillar-assisted separation (NPAS) method using surface-enhanced Raman scattering, we were able to measure MTX in PBS and serum in the linear range of 5-150 μM and confirmed that MTX detection can be carried out even in the presence of LV. Additionally, when NPAS was combined with centrifugal filtration, a quantification limit of 2.1 μM for MTX in human serum sample was achieved. The developed detection method enables fast detection (10 min) and quantification of MTX from human serum (>90% accuracy). Furthermore, we show the potential of the developed method for TDM, when quantifying MTX from clinical samples, collected from patients who are undergoing high-dose MTX therapy.

CRISPR/Cas12-Based Ultra-Sensitive and Specific Point-of-Care Detection of HBV

Hepatitis B remains a major global public health challenge, with particularly high prevalence in medically disadvantaged western Pacific and African regions. Although clinically available technologies for the qPCR detection of HBV are well established, research on point-of-care testing has not progressed substantially. The development of a rapid, accurate point-of-care test is essential for the prevention and control of hepatitis B in medically disadvantaged rural areas. The development of the CRISPR/Cas system in nucleic acid detection has allowed for pathogen point-of-care detection. Here, we developed a rapid and accurate point-of-care assay for HBV based on LAMP-Cas12a. It innovatively solves the problem of point-of-care testing in 10 min, particularly the problem of sample nucleic acid extraction. Based on LAMP-Cas12a, visualization of the assay results is presented by both a fluorescent readout and by lateral flow test strips. The lateral flow test strip technology can achieve results visible to the naked eye, while fluorescence readout can achieve real-time high-sensitivity detection. The fluorescent readout-based Cas12a assay can achieve HBV detection with a limit of detection of 1 copy/μL within 13 min, while the lateral flow test strip technique only takes 20 min. In the evaluation of 73 clinical samples, the sensitivity and specificity of both the fluorescence readout and lateral flow test strip method were 100%, and the results of the assay were fully comparable to qPCR. The LAMP-Cas12a-based HBV assay relies on minimal equipment to provide rapid, accurate test results and low costs, providing significant practical value for point-of-care HBV detection.

A Colorimetric Immunosensor Based on Hemin@MI Nanozyme Composites, with Peroxidase-like Activity for Point-of-care Testing of Pathogenic E. coli O157:H7

Recently, nanozymes have become a topic of particular interest due to their high activity level, stability and biocompatibility. In this study, a visual, sensitive and selective point-of-care immunosensor was established to test the pathogen Escherichia coli O157:H7 (E. coli O157:H7). Hemin and magainin I (MI) hybrid nanocomposites (Hemin@MI) with peroxidase-mimicking activities were synthesized via a "one-pot" method, involving the simple mixing of an antimicrobial peptide (MI) against E. coli O157:H7 and hemin in a copper sulfate sodium phosphate saline buffer. Hemin@MI nanocomposites integrating target recognition and signal amplification were developed as signal probes for the point-of-care colorimetric detection of pathogenic E. coli O157:H7. Hemin@MI nanocomposites exhibit excellent peroxidase activity for the chromogenic reaction of ABTS, which allows for the visual point-of-care testing of E. coli O157:H7 in the range of 10² to 10⁸ CFU/mL, with a limit of detection of 85 CFU/mL. These data suggest this immunosensor provides accessible and portable assessments of pathogenic E. coli O157:H7 in real samples.

Rational Design of a User-Friendly Aptamer/Peptide-Based Device for the Detection of Staphylococcus aureus

The urgent need to develop a detection system for Staphylococcus aureus, one of the most common causes of infection, is prompting research towards novel approaches and devices, with a particular focus on point-of-care analysis. Biosensors are promising systems to achieve this aim. We coupled the selectivity and affinity of aptamers, short nucleic acids sequences able to recognize specific epitopes on bacterial surface, immobilized at high density on a nanostructured zirconium dioxide surface, with the rational design of specifically interacting fluorescent peptides to assemble an easy-to-use detection device. We show that the displacement of fluorescent peptides upon the competitive binding of S. aureus to immobilized aptamers can be detected and quantified through fluorescence loss. This approach could be also applied to the detection of other bacterial species once aptamers interacting with specific antigens will be identified, allowing the development of a platform for easy detection of a pathogen without requiring access to a healthcare environment.

Microfluidic-CFPA Chip for the Point-of-Care Detection of African Swine Fever Virus with a Median Time to Threshold in about 10 min

The outbreak of African swine fever has brought serious public safety problems to the world, and there is a need for reliable diagnostic tools to prevent and control the epidemic. Here, we successfully established a portable microfluidic-circular fluorescent probe-mediated isothermal nucleic acid amplification (CFPA) system for the rapid, high-throughput, accurate, and sensitive detection of African swine fever virus at point-of-care settings. This detection system has a detection limit of 10 copies/μL, good stability (C.V. < 5%), and 92.73% sensitivity, and 100% specificity when tested on 220 pig samples collected for the diagnosis of African swine fever virus, with a median time to threshold of 10.8 min. This novel integrated diagnostic tool is urgently needed and has promising applications for the monitoring and control of African swine fever epidemics worldwide and, in particular, the serious outbreak in China.

DNA Methylation-Based Point-of-Care Cancer Detection: Challenges and Possibilities

Eukaryotic cell DNA conserves a distinct genomic methylation pattern, which acts as a molecular switch to control the transcriptional machinery of the cell. However, pathological processes can alter this methylation pattern, leading to the onset of diseases such as cancer. Recent advances in methylation analysis provide a more precise understanding of the consequence of DNA methylation changes towards cancer progression. Consequently, the discoveries of numerous methylation-based biomarkers have inspired the development of simple tests for cancer detection. In this opinion article, we systematically discuss the benefits and challenges associated with the promising methylation-based approaches and develop a point-of-care index to evaluate their potential in terms of point-of-care cancer diagnostics.

Point-of-care Ratiometric Fluorescence Imaging of Tissue for the Diagnosis of Ovarian Cancer

During a minimally invasive tumor resection procedure, it is still a challenge to rapidly and accurately trace tiny malignant tumors in real time. Fluorescent molecular imaging is considered an efficient method of localizing tumors during surgery due to its high sensitivity and biosafety. On the basis of the fact that γ-glutamyltranspeptidase (GGT) is overexpressed in ovarian cancer, we herein designed a highly sensitive ratiometric fluorescent GGT-responsive probe Py-GSH for rapid tumor detection.

Methods: The GGT response probe (Py-GSH) was constructed by using GSH group as a response group and pyrionin B as a fluorescent reporter. Py-GSH was characterized for photophysical properties, response speed and selectivity of GGT and response mechanism. The anti-interference ability of ratiometric probe Py-GSH to probe concentration and excitation power was evaluated both in vitro and in tissue. The biocompatibility and toxicity of the ratiometric probe was examined using cytoxicity test. The GGT levels in different lines of cells were determined by ratiometric fluorescence imaging and cytometry analysis.

Results: The obtained probe capable to rapidly monitored GGT activity in aqueous solution with 170-fold ratio change. By ratiometric fluorescence imaging, the probe Py-GSH was also successfully used to detect high GGT activity in solid tumor tissues and small peritoneal metastatic tumors (~1 mm in diameter) in a mouse model. In particular, this probe was further used to determine whether the tissue margin following clinical ovarian cancer surgery contained tumor.

Conclusion: In combination of ratiometric fluorescence probes with imaging instrument, a point-of-care imaging method was developed and may be used for surgical navigation and rapid diagnosis of tumor tissue during clinical tumor resection.

Exponential Isothermal Amplification of Nucleic Acids and Assays for Proteins, Cells, Small Molecules, and Enzyme Activities: An EXPAR Example

Isothermal exponential amplification techniques, such as strand-displacement amplification (SDA), rolling circle amplification (RCA), loop-mediated isothermal amplification (LAMP), nucleic acid sequence based amplification (NASBA), helicase-dependent amplification (HDA), and recombinase polymerase amplification (RPA), have great potential for on-site, point-of-care, and in situ assay applications. These amplification techniques eliminate the need for temperature cycling, as required for the polymerase chain reaction (PCR), while achieving comparable amplification yields. We highlight here recent advances in the exponential amplification reaction (EXPAR) for the detection of nucleic acids, proteins, enzyme activities, cells, and metal ions. The incorporation of fluorescence, colorimetric, chemiluminescence, Raman, and electrochemical approaches enables the highly sensitive detection of a variety of targets. Remaining issues, such as undesirable background amplification resulting from nonspecific template interactions, must be addressed to further improve isothermal and exponential amplification techniques.