Point-of-care technologies for molecular diagnostics using a drop of blood

Assessment of Salivary MMP-8 and IL-1β for the Diagnosis of Periodontal Diseases in Pakistani Population

OBJECTIVE

 Clinical methods use the subjective diagnosis of periodontal diseases by visual observation that could result in differences and variability of diagnosis. The addition of specific markers could aid in the accurate diagnosis of the local population. The objective of the study was to target two of the major proteins for possible significance in such an approach.

MATERIALS AND METHODS

 Unstimulated saliva samples were collected from 60 participants aged between 18 and 70 years. Three groups each with twenty participants were recruited into periodontitis, gingivitis, and healthy control.

STATISTICAL ANALYSIS

 The samples were analyzed using human enzyme-linked immunosorbent assay kits for matrix metalloproteinase-8 (MMP-8) and interleukin-1β (IL-1β).

RESULTS

 SPSS version 20 was used to analyze the result. Posthoc analysis by Tukey's test revealed that MMP-8 levels were higher in gingivitis and periodontitis groups as compared with healthy controls. The test also revealed that IL-1β levels were higher in the periodontitis group compared with the healthy control and gingivitis group. Additionally, one-way analysis of variance analysis showed a significant effect on probing depth in gingivitis and periodontitis patients. The mean age of periodontitis group was significantly higher than other groups.

CONCLUSION

 Salivary biomarkers may provide useful diagnostic information and could be utilized as tests for periodontal disease screening, prognosis, and prediction.

Functional Green-Emitting Mn2+-doped Zinc Germanate Persistent Luminescent Nanoparticles for Dual-Mode Immunochromatographic Detection

Immunochromatography is a commonly used immediate detection technique, using signal labels to generate detection signals for rapid medical diagnosis. However, its detection sensitivity is affected by background fluorescence caused by the excitation light source. We have developed an immunochromatographic test strip using Zn2GeO4:Mn2+ (ZGM) persistent luminescent nanoparticles (PLNPs) for immediate fluorescence detection and highly sensitive persistent luminescence (PersL) detection without background fluorescence interference. ZGM emits a strong green light when exposed to ultraviolet (UV) excitation, and its green PersL can persist for over 30 min after the excitation light is turned off. We modified the surface of ZGM with heparin-binding protein (HBP) antibodies to create immunochromatographic test strips for the detection of HBP as the target analyte. Under UV excitation, the chromatography test paper can be visually observed at concentrations as low as 25 ng/mL. After the excitation light source is switched off, PersL can achieve a detection limit of 4.7 ng/mL without background interference. This dual-mode immunochromatographic detection, based on ZGM, shows great potential for in vitro diagnostic applications.

Acoustic separation and concentration of exosomes for nucleotide detection: ASCENDx

Efficient isolation and analysis of exosomal biomarkers hold transformative potential in biomedical applications. However, current methods are prone to contamination and require costly consumables, expensive equipment, and skilled personnel. Here, we introduce an innovative spaceship-like disc that allows Acoustic Separation and Concentration of Exosomes and Nucleotide Detection: ASCENDx. We created ASCENDx to use acoustically driven disc rotation on a spinning droplet to generate swift separation and concentration of exosomes from patient plasma samples. Integrated plasmonic nanostars on the ASCENDx disc enable label-free detection of enriched exosomes via surface-enhanced Raman scattering. Direct detection of circulating exosomal microRNA biomarkers from patient plasma samples by the ASCENDx platform facilitated a diagnostic assay for colorectal cancer with 95.8% sensitivity and 100% specificity. ASCENDx overcomes existing limitations in exosome-based molecular diagnostics and holds a powerful position for future biomedical research, precision medicine, and point-of-care medical diagnostics.

Multiplexed Biosensing of Proteins and Virions with Disposable Plasmonic Assays

Our growing ability to tailor healthcare to the needs of individuals has the potential to transform clinical treatment. However, the measurement of multiple biomarkers to inform clinical decisions requires rapid, effective, and affordable diagnostics. Chronic diseases and rapidly evolving pathogens in a larger population have also escalated the need for improved diagnostic capabilities. Current chemical diagnostics are often performed in centralized facilities and are still dependent on multiple steps, molecular labeling, and detailed analysis, causing the result turnaround time to be over hours and days. Rapid diagnostic kits based on lateral flow devices can return results quickly but are only capable of detecting a handful of pathogens or markers. Herein, we present the use of disposable plasmonics with chiroptical nanostructures as a platform for low-cost, label-free optical biosensing with multiplexing and without the need for flow systems often required in current optical biosensors. We showcase the detection of SARS-CoV-2 in complex media as well as an assay for the Norovirus and Zika virus as an early developmental milestone toward high-throughput, single-step diagnostic kits for differential diagnosis of multiple respiratory viruses and any other emerging diagnostic needs. Diagnostics based on this platform, which we term "disposable plasmonics assays," would be suitable for low-cost screening of multiple pathogens or biomarkers in a near-point-of-care setting.

Engineering Innovative Interfaces for Point-of-Care Diagnostics

The ongoing Coronavirus disease 2019 (COVID-19) pandemic illustrates the need for sensitive and reliable tools to diagnose and monitor diseases. Traditional diagnostic approaches rely on centralized laboratory tests that result in long wait times to results and reduce the number of tests that can be given. Point-of-care tests (POCTs) are a group of technologies that miniaturize clinical assays into portable form factors that can be run both in clinical areas --in place of traditional tests-- and outside of traditional clinical settings --to enable new testing paradigms. Hallmark examples of POCTs are the pregnancy test lateral flow assay and the blood glucose meter. Other uses for POCTs include diagnostic assays for diseases like COVID-19, HIV, and malaria but despite some successes, there are still unsolved challenges for fully translating these lower cost and more versatile solutions. To overcome these challenges, researchers have exploited innovations in colloid and interface science to develop various designs of POCTs for clinical applications. Herein, we provide a review of recent advancements in lateral flow assays, other paper based POCTs, protein microarray assays, microbead flow assays, and nucleic acid amplification assays. Features that are desirable to integrate into future POCTs, including simplified sample collection, end-to-end connectivity, and machine learning, are also discussed in this review.

Affinity-based electrochemical sensors for biomolecular detection in whole blood

The detection and/or quantification of biomarkers in blood is important for the early detection, diagnosis, and treatment of a variety of diseases and medical conditions. Among the different types of sensors for detecting molecular biomarkers, such as proteins, nucleic acids, and small-molecule drugs, affinity-based electrochemical sensors offer the advantages of high analytical sensitivity and specificity, fast detection times, simple operation, and portability. However, biomolecular detection in whole blood is challenging due to its highly complex matrix, necessitating sample purification (i.e., centrifugation), which involves the use of bulky, expensive equipment and tedious sample-handling procedures. To address these challenges, various strategies have been employed, such as purifying the blood sample directly on the sensor, employing micro-/nanoparticles to enhance the detection signal, and coating the electrode surface with blocking agents to reduce nonspecific binding, to improve the analytical performance of affinity-based electrochemical sensors without requiring sample pre-processing steps or laboratory equipment. In this article, we present an overview of affinity-based electrochemical sensor technologies that employ these strategies for biomolecular detection in whole blood.

Magnetically localized and wash-free fluorescence immunoassay (MLFIA): proof of concept and clinical applications

Immunoassays are used for many applications in various markets, from clinical diagnostics to the food industry, generally relying on gold-standard ELISAs that are sensitive, robust, and cheap but also time-consuming and labour intensive. As an alternative, we propose here the magnetically localized and wash-free fluorescence immunoassay (MLFIA): a no-wash assay to directly measure a biomolecule concentration, without mixing nor washing steps. To do so, a fluorescence no-wash measurement is performed to generate a detectable signal. It consists of a differential measurement between the fluorescence of fluorophores bound to magnetic nanoparticles specifically captured by micro-magnets against the residual background fluorescence of unbound fluorophores. Targeted biomolecules (antibodies or antigens) are locally concentrated on micro-magnet lines, with the number of captured biomolecules quantitatively measured without any washing step. The performance of the MLFIA platform is assessed and its use is demonstrated with several biological models as well as clinical blood samples for HIV, HCV and HBV detection, with benchmarking to standard analyzers of healthcare laboratories. Thus, we demonstrated for the first time the versatility of the innovative MLFIA platform. We highlighted promising performances with the successful quantitative detection of various targets (antigens and antibodies), in different biological samples (serum and plasma), for different clinical tests (HCV, HBV, HIV).

Biogenic Selenium Nanoparticles in Biomedical Sciences: Properties, Current Trends, Novel Opportunities and Emerging Challenges in Theranostic Nanomedicine

Selenium is an important dietary supplement and an essential trace element incorporated into selenoproteins with growth-modulating properties and cytotoxic mechanisms of action. However, different compounds of selenium usually possess a narrow nutritional or therapeutic window with a low degree of absorption and delicate safety margins, depending on the dose and the chemical form in which they are provided to the organism. Hence, selenium nanoparticles (SeNPs) are emerging as a novel therapeutic and diagnostic platform with decreased toxicity and the capacity to enhance the biological properties of Se-based compounds. Consistent with the exciting possibilities offered by nanotechnology in the diagnosis, treatment, and prevention of diseases, SeNPs are useful tools in current biomedical research with exceptional benefits as potential therapeutics, with enhanced bioavailability, improved targeting, and effectiveness against oxidative stress and inflammation-mediated disorders. In view of the need for developing eco-friendly, inexpensive, simple, and high-throughput biomedical agents that can also ally with theranostic purposes and exhibit negligible side effects, biogenic SeNPs are receiving special attention. The present manuscript aims to be a reference in its kind by providing the readership with a thorough and comprehensive review that emphasizes the current, yet expanding, possibilities offered by biogenic SeNPs in the biomedical field and the promise they hold among selenium-derived products to, eventually, elicit future developments. First, the present review recalls the physiological importance of selenium as an oligo-element and introduces the unique biological, physicochemical, optoelectronic, and catalytic properties of Se nanomaterials. Then, it addresses the significance of nanosizing on pharmacological activity (pharmacokinetics and pharmacodynamics) and cellular interactions of SeNPs. Importantly, it discusses in detail the role of biosynthesized SeNPs as innovative theranostic agents for personalized nanomedicine-based therapies. Finally, this review explores the role of biogenic SeNPs in the ongoing context of the SARS-CoV-2 pandemic and presents key prospects in translational nanomedicine.

miRNA probe integrated biosensor platform using bimetallic nanostars for amplification-free multiplexed detection of circulating colorectal cancer biomarkers in clinical samples

There is a critical need for sensitive and rapid detection technologies utilizing molecular biotargets such as microRNAs (miRNAs), which regulate gene expression and are a promising class of diagnostic biomarkers for disease detection. Here, we present the development and fabrication of a highly reproducible and robust plasmonic bimetallic nanostar biosensing platform to detect miRNA targets using surfaced-enhanced Raman scattering (SERS)-based gene probes called the inverse Molecular Sentinel (iMS). We investigated and optimized the integration of iMS gene probes onto this SERS substrate, achieving ultra-sensitive detection with limits of detection of 6.8 and 16.7 zmol within the sensing region for two miRNA sequences of interest. Finally, we demonstrated the biomedical usefulness of this nanobiosensor platform with the multiplexed detection of upregulated miRNA targets, miR21 and miR221, from colorectal cancer patient plasma. The resulting SERS data are in excellent agreement with PCR data obtained from patient samples and can distinguish between healthy and cancerous patient samples. These results underline the potential of the iMS-integrated substrate nanobiosensing platform for rapid and sensitive diagnostics of cancer biomarkers for point-of-care applications.

Mathematical Study of the Perturbation of Magnetic Fields Caused by Erythrocytes

The purpose of this chapter is the mathematical study of the perturbation of a homogeneous static magnetic field caused by the embedding of a red blood cell. Analytical expressions for the magnetic potential and the magnetic strength vector are derived. From the obtained results, it emerges that the magnetic field inside the red blood cell is not uniform and the magnitude depends on the orientation of the erythrocyte. The expressions for the magnetic field quantities are significant in applications such as the magnetic resonance imaging and in the magnetic resonance spectroscopy.

Clinical applications of plasma proteomics and peptidomics: Towards precision medicine

In the context of precision medicine, disease treatment requires individualized strategies based on the underlying molecular characteristics to overcome therapeutic challenges posed by heterogeneity. For this purpose, it is essential to develop new biomarkers to diagnose, stratify, or possibly prevent diseases. Plasma is an available source of biomarkers that greatly reflects the physiological and pathological conditions of the body. An increasing number of studies are focusing on proteins and peptides, including many involving the Human Proteome Project (HPP) of the Human Proteome Organization (HUPO), and proteomics and peptidomics techniques are emerging as critical tools for developing novel precision medicine preventative measures. Excitingly, the emerging plasma proteomics and peptidomics toolbox exhibits a huge potential for studying pathogenesis of diseases (e.g., COVID-19 and cancer), identifying valuable biomarkers and improving clinical management. However, the enormous complexity and wide dynamic range of plasma proteins makes plasma proteome profiling challenging. Herein, we summarize the recent advances in plasma proteomics and peptidomics with a focus on their emerging roles in COVID-19 and cancer research, aiming to emphasize the significance of plasma proteomics and peptidomics in clinical applications and precision medicine.

Fluorescence-polarization immunoassays within glass fiber micro-chambers enable tobramycin quantification in whole blood for therapeutic drug monitoring at the point of care

Many therapeutic drugs require monitoring of their concentration in blood followed by dose adjustments in order to ensure efficacy while minimizing adverse effects. It would be highly desirable to perform such measurements rapidly and with reduced sample volumes to support point-of-care testing. Here, we demonstrate that the concentration of small therapeutics can be determined in whole blood within paper-like membranes using Fluorescence Polarization Immunoassay (FPIA). Different types of paper-like materials such as glass microfibers, cellulose and filter paper were investigated for artefacts such as scattering or autofluorescence. Accurate determination of the fluorescence polarization of red-emitting fluorophores at sub-nanomolar concentrations was feasible within glass fiber membranes. This enabled the development of a competitive immunoassay for the quantification of the antibiotic tobramycin using only 1 μL of plasma in glass fiber micro-chambers. Furthermore, the same membrane was used for transversal separation of blood cells followed by accurate FPIA read-out at the bottom part of the micro-chamber. For quantification of tobramycin, 1 μL of whole blood was incubated with the immunoassay reagents during only 3 min before deposition in the micro-chamber and analysis. Within the therapeutic window, coefficients of variation were around 20% and recoveries between 80 and 105%. Owing to the simplified procedure requiring no centrifugation, the reduced blood sample volume and the rapid analysis time, we envision that this novel method supports the performance of therapeutic drug monitoring directly at the point of care.

Microfluidics-Based Urine Biopsy for Cancer Diagnosis: Recent Advances and Future Trends

Urine biopsy, allowing for the detection, analysis and monitoring of numerous cancer-associated urinary biomarkers to provide insights into cancer occurrence, progression and metastasis, has emerged as an attractive liquid biopsy strategy with enormous advantages over traditional tissue biopsy, such as noninvasiveness, large sample volume, and simple sampling operation. Microfluidics enables precise manipulation of fluids in a tiny chip and exhibits outstanding performance in urine biopsy owing to its minimization, low cost, high integration, high throughput and low sample consumption. Herein, we review recent advances in microfluidic techniques employed in urine biopsy for cancer detection. After briefly summarizing the major urinary biomarkers used for cancer diagnosis, we provide an overview of the typical microfluidic techniques utilized to develop urine biopsy devices. Some prospects along with the major challenges to be addressed for the future of microfluidic-based urine biopsy are also discussed.

A Review of the Nucleic Acid-Based Lateral Flow Assay for Detection of Breast Cancer from Circulating Biomarkers at a Point-of-Care in Low Income Countries

The current levels of breast cancer in African women have contributed to the high mortality rates among them. In South Africa, the incidence of breast cancer is also on the rise due to changes in behavioural and biological risk factors. Such low survival rates can be attributed to the late diagnosis of the disease due to a lack of access and the high costs of the current diagnostic tools. Breast cancer is asymptomatic at early stages, which is the best time to detect it and intervene to prevent high mortality rates. Proper risk assessment, campaigns, and access to adequate healthcare need to be prioritised among patients at an early stage. Early detection of breast cancer can significantly improve the survival rate of breast cancer patients, since therapeutic strategies are more effective at this stage. Early detection of breast cancer can be achieved by developing devices that are simple, sensitive, low-cost, and employed at point-of-care (POC), especially in low-income countries (LICs). Nucleic-acid-based lateral flow assays (NABLFAs) that combine molecular detection with the immunochemical visualisation principles, have recently emerged as tools for disease diagnosis, even for low biomarker concentrations. Detection of circulating genetic biomarkers in non-invasively collected biological fluids with NABLFAs presents an appealing and suitable method for POC testing in resource-limited regions and/or LICs. Diagnosis of breast cancer at an early stage will improve the survival rates of the patients. This review covers the analysis of the current state of NABLFA technologies used in developing countries to reduce the scourge of breast cancer.

Portable, Disposable, Biomimetic Electrochemical Sensors for Analyte Detection in a Single Drop of Whole Blood

Current diagnostics call for rapid, sensitive, and selective screening of physiologically important biomarkers. Point-of-care (POC) devices for the rapid, reliable, and easy acquisition of bioinformation at, or near the patient, offer opportunities for better healthcare management. Electrochemical biosensors with high sensitivity and ease of miniaturization are advantageous for such applications. We report a photolithographically micropatterned PEDOT:PSS and silk protein-based fully organic 3-electrode sensor (O3ES) for ultralow volume (single drop—10 µL) detection of analytes in whole blood. The O3ES produces reliable electrochemical signals in whole blood from a mouse model with minimal biofouling interference. The O3ES is demonstrated as a portable device for the simultaneous detection of dopamine, ascorbic acid and uric acid using voltammetry techniques. The O3ES displays excellent sensitivity towards each analyte in whole blood, and in the presence of each other. The water-based, ambient processing of the sensors allows the immobilization of enzymes in the organic working electrode. Amperometric detection of uric acid via uricase with high sensitivity in whole blood is demonstrated. Finally, the performance of the O3ES under enzymatic degradation is studied by monitoring sensitivity over an operating lifetime of ~14 days. This work demonstrates the realization of low-cost, disposable POC sensors capable of detecting blood metabolites using ultralow sample volumes.

Fluorescence Signal Enhancement by a Spray-Assisted Layer-by-Layer Technique on Aluminum Tape Devices for Biosensing Applications

Layer-by-layer (LbL) self-assembled polyelectrolyte multilayer (PEM) films are a simple yet elegant bottom-up technology to create films at the nano-microscale. This low-cost technology has been widely used as a universal functionalization technique on a broad spectrum of substrates. Biomolecules under investigation can be incubated onto films based on complementary charge interactions between the films and biomolecules. There is a great demand for developing an ultralow-cost biosensing device, which can optimally enhance the fluorescence signal of the adsorbed biomolecules from the traditional labeled sensing platforms. In this work, we have incorporated a blend of the conventional metal enhanced fluorescence technology and the PEM as a dielectric spacer and functionalized film, coated on an aluminum paper (tape)-based substrate. These device has been found to be capable of holding biomolecules in three-dimensional PEM space. The devices fabricated by the proposed spray LbL technique provide significant fluorescence signal enhancement by holding a relatively higher mass per volume of the adsorbed biomolecules, when compared to traditional spin- and dip-coating techniques. Interestingly, our proposed device has expressed a fluorescence enhancement factor, which is 9 times higher than PEM-functionalized glass-based devices. To demonstrate the practical utility of our devices, we also compared our devices to Whatman FAST slides. Our experimental fluorescence results are almost comparable to Whatman FAST slides. Such PEM devices fabricated on top of low-cost aluminum tape using a spray LbL technique give new insights into the future development of ultralow-cost, high-throughput, and disposable lab-on-chip diagnostic applications.

Nanomaterial-assisted microfluidics for multiplex assays

Simultaneous detection of different biomarkers from a single specimen in a single test, allowing more rapid, efficient, and low-cost analysis, is of great significance for accurate diagnosis of disease and efficient monitoring of therapy. Recently, developments in microfabrication and nanotechnology have advanced the integration of nanomaterials in microfluidic devices toward multiplex assays of biomarkers, combining both the advantages of microfluidics and the unique properties of nanomaterials. In this review, we focus on the state of the art in multiplexed detection of biomarkers based on nanomaterial-assisted microfluidics. Following an overview of the typical microfluidic analytical techniques and the most commonly used nanomaterials for biochemistry analysis, we highlight in detail the nanomaterial-assisted microfluidic strategies for different biomarkers. These highly integrated platforms with minimum sample consumption, high sensitivity and specificity, low detection limit, enhanced signals, and reduced detection time have been extensively applied in various domains and show great potential in future point-of-care testing and clinical diagnostics.

Recent advances in porous microneedles: materials, fabrication, and transdermal applications

In the past two decades, microneedles (MNs), as a painless and simple drug delivery system, have received increasing attention for various biomedical applications such as transdermal drug delivery, interstitial fluid (ISF) extraction, and biosensing. Among the various types of MNs, porous MNs have been recently researched owing to their distinctive and unique characteristics, where porous structures inside MNs with continuous nano- or micro-sized pores can transport drugs or biofluids by capillary action. In addition, a wide range of materials, including non-polymers and polymers, were researched and used to form the porous structures of porous MNs. Adjustable porosity by different fabrication methods enables the achievement of sufficient mechanical strength by optimising fluid flows inside MNs. Moreover, biocompatible porous MNs integrated with biosensors can offer portable detection and rapid measurement of biomarkers in a minimally invasive manner. This review focuses on several aspects of current porous MN technology, including material selection, fabrication processes, biomedical applications, primarily covering transdermal drug delivery, ISF extraction, and biosensing, along with future prospects as well as challenges.

Visible-light and near-infrared fluorescence and surface-enhanced Raman scattering point-of-care sensing and bio-imaging: a review

This review article deals with the concepts, principles and applications of visible-light and near-infrared (NIR) fluorescence and surface-enhanced Raman scattering (SERS) in in vitro point-of-care testing (POCT) and in vivo bio-imaging. It has discussed how to utilize the biological transparency windows to improve the penetration depth and signal-to-noise ratio, and how to use surface plasmon resonance (SPR) to amplify fluorescence and SERS signals. This article has highlighted some plasmonic fluorescence and SERS probes. It has also reviewed the design strategies of fluorescent and SERS sensors in the detection of metal ions, small molecules, proteins and nucleic acids. Particularly, it has provided perspectives on the integration of fluorescent and SERS sensors into microfluidic chips as lab-on-chips to realize point-of-care testing. It has also discussed the design of active microfluidic devices and non-paper- or paper-based lateral flow assays for in vitro diagnostics. In addition, this article has discussed the strategies to design in vivo NIR fluorescence and SERS bio-imaging platforms for monitoring physiological processes and disease progression in live cells and tissues. Moreover, it has highlighted the applications of POCT and bio-imaging in testing toxins, heavy metals, illicit drugs, cancers, traumatic brain injuries, and infectious diseases such as COVID-19, influenza, HIV and sepsis.

Plasmonic Nanoparticle Conjugation for Nucleic Acid Biosensing

This chapter details the use of gold nanorods conjugated with peptide nucleic acid probes for sequence-specific detection of circulating tumor DNA (ctDNA). ctDNA is gaining increased attention as a biomarker for liquid biopsy, the process of detecting molecules in the peripheral blood rather than a tissue sample. It has wide ranging applications as a diagnostic and prognostic biomarker with a similar mutational profile as the tumor. Plasmonic nanoparticles offer a relatively rapid, amplification-free method for detection of ctDNA through the use of sequence-specific peptide nucleic acid (PNA) probes. In this chapter, we discuss methods for probe design, conjugation to plasmonic particles, and ctDNA quantitation with the resulting sensor. This chapter is a resource for those looking to use plasmonic gold particles for sensing in a solution format for a range of applications.

A Universal Boronate-Affinity Crosslinking-Amplified Dynamic Light Scattering Immunoassay for Point-of-Care Glycoprotein Detection

Herein, we report a universal boronate-affinity crosslinking-amplified dynamic light scattering (DLS) immunoassay for point-of-care (POC) glycoprotein detection in complex samples. This enhanced DLS immunoassay consists of two elements, i.e., antibody-coated magnetic nanoparticles (MNP@mAb) for target capture and DLS signal transduction, and phenylboronic acid-based boronate-affinity materials as crosslinking amplifiers. Upon the addition of targets, glycoproteins are first captured by MNP@mAb and amplified by target-induced crosslinking stemming from the selective binding between the boronic acid ligand and cis-diol-containing glycoprotein, thereby resulting in a remarkably increased DLS signal in the average nanoparticle size. Benefiting from the multivalent binding and fast boronate-affinity reaction between glycoproteins and crosslinkers, the proposed immunosensing strategy has achieved the ultrasensitive and rapid quantitative assay of glycoproteins at the fM level within 15 min. Overall, this work provides a promising and versatile design strategy for extending the DLS technique to detect glycoproteins even in the field or at POC.

A Fluorescent Biosensor for Sensitive Detection of Salmonella Typhimurium Using Low-Gradient Magnetic Field and Deep Learning via Faster Region-Based Convolutional Neural Network

In this study, a fluorescent biosensor was developed for the sensitive detection of Salmonella typhimurium using a low-gradient magnetic field and deep learning via faster region-based convolutional neural networks (R-CNN) to recognize the fluorescent spots on the bacterial cells. First, magnetic nanobeads (MNBs) coated with capture antibodies were used to separate target bacteria from the sample background, resulting in the formation of magnetic bacteria. Then, fluorescein isothiocyanate fluorescent microspheres (FITC-FMs) modified with detection antibodies were used to label the magnetic bacteria, resulting in the formation of fluorescent bacteria. After the fluorescent bacteria were attracted against the bottom of an ELISA well using a low-gradient magnetic field, resulting in the conversion from a three-dimensional (spatial) distribution of the fluorescent bacteria to a two-dimensional (planar) distribution, the images of the fluorescent bacteria were finally collected using a high-resolution fluorescence microscope and processed using the faster R-CNN algorithm to calculate the number of the fluorescent spots for the determination of target bacteria. Under the optimal conditions, this biosensor was able to quantitatively detect Salmonella typhimurium from 6.9 × 10¹ to 1.1 × 10³ CFU/mL within 2.5 h with the lower detection limit of 55 CFU/mL. The fluorescent biosensor has the potential to simultaneously detect multiple types of foodborne bacteria using MNBs coated with their capture antibodies and different fluorescent microspheres modified with their detection antibodies.

Precise Microfluidic Luminescent Sensor Platform with Controlled Injection System

Efforts have been devoted to screening various prevalent diseases, such as severe acute respiratory syndrome (SARS) and coronavirus disease 2019 (COVID-19). Real-time polymerase chain reaction (RT-PCR), which is currently the most widely used, has high accuracy, but it requires several facilities and takes a relatively long time to check; so, new testing technology is necessary for a higher test efficiency. A chemiluminescence (CL) sensor is a relatively simple device and suitable as an alternative because it can detect very precise specimens. However, in measurements via CL, the quantitative formulation of reagents that cause color development is important. In the case of mixing using micropipettes, precise analysis is possible, but this technique is limited by uncontrollable errors or deviations in detection amounts. In addition, in using a microfluidic chip to increase field applicability, a syringe pump or other quantification injection tools are required, so problems must be overcome for practical use. Therefore, in this study, a microchip was designed and manufactured to supply a sample of a certain volume by simply blowing air and injecting a sample into the chamber. By utilizing the luminescence reaction of luminol, CuSO4 and H2O2 the performance of the prepared chip was confirmed, and the desired amount of the sample could be injected with a simple device with an error rate of 2% or less. For feasible applications, an experiment was performed to quantitatively analyze thrombin, a biomarker of heart disease. Results demonstrated that biomarkers could be more precisely detected using the proposed microchips than using micropipettes.

Current diagnostic approaches to detect two important betacoronaviruses: Middle East respiratory syndrome coronavirus (MERS-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)

Middle East respiratory syndrome coronavirus (MERS-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are two common betacoronaviruses, which are still causing transmission among the human population worldwide. The major difference between the two coronaviruses is that MERS-CoV is now causing sporadic transmission worldwide, whereas SARS-CoV-2 is causing a pandemic outbreak globally. Currently, different guidelines and reports have highlighted several diagnostic methods and approaches which could be used to screen and confirm MERS-CoV and SARS-CoV-2 infections. These methods include clinical evaluation, laboratory diagnosis (nucleic acid-based test, protein-based test, or viral culture), and radiological diagnosis. With the presence of these different diagnostic approaches, it could cause a dilemma to the clinicians and diagnostic laboratories in selecting the best diagnostic strategies to confirm MERS-CoV and SARS-CoV-2 infections. Therefore, this review aims to provide an up-to-date comparison of the advantages and limitations of different diagnostic approaches in detecting MERS-CoV and SARS-CoV-2 infections. This review could provide insights for clinicians and scientists in detecting MERS-CoV and SARS-CoV-2 infections to help combat the transmission of these coronaviruses.

Biomarkers and Lung Cancer Early Detection: State of the Art

Simple Summary

Lung cancer is the leading cause of cancer death worldwide. Detecting lung malignancies promptly is essential for any anticancer treatment to reduce mortality and morbidity, especially in high-risk individuals. The use of liquid biopsy to detect circulating biomarkers such as RNA, microRNA, DNA, proteins, autoantibodies in the blood, as well as circulating tumor cells (CTCs), can substantially change the way we manage lung cancer patients by improving disease stratification using intrinsic molecular characteristics, identification of therapeutic targets and monitoring molecular residual disease. Here, we made an update on recent developments in liquid biopsy-based biomarkers for lung cancer early diagnosis, and we propose guidelines for an accurate study design, execution, and data interpretation for biomarker development.

Abstract

Lung cancer burden is increasing, with 2 million deaths/year worldwide. Current limitations in early detection impede lung cancer diagnosis when the disease is still localized and thus more curable by surgery or multimodality treatment. Liquid biopsy is emerging as an important tool for lung cancer early detection and for monitoring therapy response. Here, we reviewed recent advances in liquid biopsy for early diagnosis of lung cancer. We summarized DNA- or RNA-based biomarkers, proteins, autoantibodies circulating in the blood, as well as circulating tumor cells (CTCs), and compared the most promising studies in terms of biomarkers prediction performance. While we observed an overall good performance for the proposed biomarkers, we noticed some critical aspects which may complicate the successful translation of these biomarkers into the clinical setting. We, therefore, proposed a roadmap for successful development of lung cancer biomarkers during the discovery, prioritization, and clinical validation phase. The integration of innovative minimally invasive biomarkers in screening programs is highly demanded to augment lung cancer early detection.

Nucleic Acid Tests for Clinical Translation

Nucleic acids, including deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are natural biopolymers composed of nucleotides that store, transmit, and express genetic information. Overexpressed or underexpressed as well as mutated nucleic acids have been implicated in many diseases. Therefore, nucleic acid tests (NATs) are extremely important. Inspired by intracellular DNA replication and RNA transcription, in vitro NATs have been extensively developed to improve the detection specificity, sensitivity, and simplicity. The principles of NATs can be in general classified into three categories: nucleic acid hybridization, thermal-cycle or isothermal amplification, and signal amplification. Driven by pressing needs in clinical diagnosis and prevention of infectious diseases, NATs have evolved to be a rapidly advancing field. During the past ten years, an explosive increase of research interest in both basic research and clinical translation has been witnessed. In this review, we aim to provide comprehensive coverage of the progress to analyze nucleic acids, use nucleic acids as recognition probes, construct detection devices based on nucleic acids, and utilize nucleic acids in clinical diagnosis and other important fields. We also discuss the new frontiers in the field and the challenges to be addressed.

Saliva as a Source of Biomarkers for Periodontitis and Periimplantitis

Saliva has the potential to be used as a diagnostic and monitoring tool for various diseases if biomarkers of an adequate sensitivity and specificity could be identified. Several reviews and even meta-analyses have been performed in recent years, which have found some candidate biomarkers for periodontitis, like macrophage inflammatory protein-1 alpha, interleukin-1ß, interleukin-6, matrix metalloproteinase-8, or hemoglobin. However, none of those are currently in use to replace conventional periodontal diagnostics with a periodontal probe. For periimplantitis, to date, heterogeneity of different study protocols and implant types did not permit to discover clear biomarkers, which were able to distinguish between healthy and diseased implants. Few proinflammatory cytokines, similar to periodontitis, have been characterized as adjunct tools to clinical diagnosis. The additional determination of antimicrobial peptides, bone turnover markers, and bacteria could help to enhance sensitivity and specificity in a combined model for periodontitis and periimplantitis. Furthermore, proteomic approaches might be preferred over single biomarker determinations. A global consensus is also needed to harmonize salivary sampling methods as well as procedures of biomarker analysis to ensure future comparability.

Aptamer-Integrated Multianalyte-Detecting Paper Electrochemical Device

On-site detection of multiple small-molecule analytes in complex sample matrixes would be highly valuable for diverse biosensing applications. Paper electrochemical devices (PEDs) offer an especially appealing sensing platform for such applications due to their low cost, portability, and ease of use. Using oligonucleotide-based aptamers as biorecognition elements, we here for the first time have developed a simple, inexpensive procedure for the fabrication of aptamer-modified multiplex PEDs (mPEDs), which can robustly and specifically detect multiple small molecules in complex samples. These devices are prepared via an ambient vacuum filtration technique using carbon and metal nanomaterials that yields precisely patterned sensing architecture featuring a silver pseudo-reference electrode, a gold counter electrode, and three gold working electrodes. The devices are user-friendly, and the fabrication procedure is highly reproducible. Each working electrode can be readily modified with different aptamers for sensitive and accurate detection of multiple small-molecule analytes in a single sample within seconds. We further demonstrate that the addition of a PDMS chamber allows us to achieve detection in microliter volumes of biological samples. We believe this approach should be highly generalizable, and given the rapid development of small-molecule aptamers, we envision that facile on-site multi-analyte detection of diverse targets in a drop of sample should be readily achievable in the near future.

A centrifugal microfluidic cross-flow filtration platform to separate serum from whole blood for the detection of amphiphilic biomarkers

The separation of biomarkers from blood is straightforward in most molecular biology laboratories. However, separation in resource-limited settings, allowing for the successful removal of biomarkers for diagnostic applications, is not always possible. The situation is further complicated by the need to separate hydrophobic signatures such as lipids from blood. Herein, we present a microfluidic device capable of centrifugal separation of serum from blood at the point of need with a system that is compatible with biomarkers that are both hydrophilic and hydrophobic. The cross-flow filtration device separates serum from blood as efficiently as traditional methods and retains amphiphilic biomarkers in serum for detection.

Gradient-Based Rapid Digital Immunoassay for High-Sensitivity Cardiac Troponin T (hs-cTnT) Detection in 1 μL Plasma

Rapid and sensitive detection of biomarkers is the key to the diagnosis of acute diseases. One example is the detection of troponin in myocardial infarction. Here, we report a gradient-based digital immunoassay method, which can achieve high-sensitivity cardiac troponin T (hs-cTnT) detection with only 1 μL of plasma sample. We designed a multizone microfluidic channel functionalized with capture antibody specific to troponin. Taking advantage of limited sample volume, a troponin concentration gradient is created along the channel because of binding induced depletion. We quantified the concentration gradient by counting the detection antibody conjugated gold nanoparticles bound to different test zones with optical imaging. Differential counting between the zones removes most common noises and nonspecific bindings. The total analytical time is about 30 min, and the limit of quantification is 6.2 ng/L. We examined 41 clinical plasma samples from 15 patients and the change in hs-cTnT concentration in serial samples showed good linear correlation with clinical results (R² = 0.98). Therefore, this simple and sensitive gradient-based digital immunoassay method is a promising technology for clinical hs-cTnT detection and could be adapted for detection of other biomarkers.

Gas-propelled biosensors for quantitative analysis

Gas-propelled biosensors display a simple gas-based signal amplification with quantitative detection features based on the target recognition event in combination with gas propulsion. Due to the liquid-gas conversion, the gas not only pushes the ink bar forward in the microchannel, but also serves as the power to propel the micromotors in the liquid. Thus, this continuous motion leads to a shift in distances which is associated with the target amount. Therefore, gas-propelled biosensors provide a visual quantification based on distance or speed signals without the need for expensive instruments. In this review, we focus on current developments in gas-propelled biosensors for quantitative analysis. First, we list the types of gas utilized as actuators in biosensors. Second, we review the representative gas-propelled biosensors, including the propulsion mechanisms and fabrication methods. Moreover, gas-propelled quantification based on distance and speed is summarized. Finally, we cover applications and provide a future perspective of gas-propelled biosensors.

Oriented Immobilization of Protein Templates: A New Trend in Surface Imprinting

In this Review, we have summarized recent trends in protein template imprinting. We emphasized a new trend in surface imprinting, namely, oriented protein immobilization. Site-directed proteins were assembled through specially selected functionalities. These efforts resulted in a preferably oriented homogeneous protein construct with decreased protein conformation changes during imprinting. Moreover, the maximum functionality for protein recognition was utilized. Various strategies were exploited for oriented protein immobilization, including covalent immobilization through a boronic acid group, metal coordinating center, and aptamer-based immobilization. Moreover, we have discussed the involvement of semicovalent as well as covalent imprinting. Interestingly, these approaches provided additional recognition sites in the molecular cavities imprinted. Therefore, these molecular cavities were highly selective, and the binding kinetics was improved.

Picosecond Laser Processing of Photosensitive Glass for Generation of Biologically Relevant Microenvironments

Various material processing techniques have been proposed for fabrication of smart surfaces that can modulate cellular behavior and address specific clinical issues. Among them, laser-based technologies have attracted growing interest due to processing versatility. Latest development of ultrashort pulse lasers with pulse widths from several tens of femtoseconds (fs) to several picoseconds (ps) allows clean microfabrication of a variety of materials at micro- and nanoscale both at surface and in volume. In this study, we addressed the possibility of 3D microfabrication of photosensitive glass (PG) by high repetition rate ps laser-assisted etching (PLAE) to improve the fabrication efficiency for the development of useful tools to be used for specific biological applications. Microfluidic structures fabricated by PLAE should provide the flow aspects, 3D characteristics, and possibility of producing functional structures to achieve the biologically relevant microenvironments. Specifically, the microfluidic structures could induce cellular chemotaxis over extended periods in diffusion-based gradient media. More importantly, the 3D characteristics could reproduce capillaries for in vitro testing of relevant organ models. Single cell trapping and analysis by using the fabricated microfluidic structures are also essential for understanding individual cell behavior within the same population. To this end, this paper demonstrates: (1) generation of 3D structures in glass volume or on surface for fabrication of microfluidic channels, (2) subtractive 3D surface patterning to create patterned molds in a controlled manor for casting polydimethylsiloxane (PDMS) structures and developing single cell microchambers, and (3) designing glass photo-masks to be used for sequel additive patterning of biocompatible nanomaterials with controlled shapes, sizes, and periodicity. Mesenchymal stem cells grown on laser-processed glass surfaces revealed no sign of cytotoxicity, while a collagen thin coating improved cellular adhesion.

Multiplexed Nanobiosensors: Current Trends in Early Diagnostics

The ever-growing demand for fast, cheap, and reliable diagnostic tools for personalised medicine is encouraging scientists to improve existing technology platforms and to create new methods for the detection and quantification of biomarkers of clinical significance. Simultaneous detection of multiple analytes allows more accurate assessment of changes in biomarker expression and offers the possibility of disease diagnosis at the earliest stages. The concept of multiplexing, where multiple analytes can be detected in a single sample, can be tackled using several types of nanomaterial-based biosensors. Quantum dots are widely used photoluminescent nanoparticles and represent one of the most frequent choices for different multiplex systems. However, nanoparticles that incorporate gold, silver, and rare earth metals with their unique optical properties are an emerging perspective in the multiplexing field. In this review, we summarise progress in various nanoparticle applications for multiplexed biomarkers.

CRISPR-Cas12a-Assisted Multicolor Biosensor for Semiquantitative Point-of-Use Testing of the Nopaline Synthase Terminator in Genetically Modified Crops by Unaided Eyes

Existing methods of detecting foreign genes and their expression products from genetically modified organisms (GMOs) suffer from the requirement of professional equipment and skillful operators. The same problem stays for the CRISPR-Cas12a system, although it has been emerging as a powerful tool for nucleic acid detection due to its remarkable sensitivity and specificity. In this report, a portable platform for the visible detection of GMOs based on CRISPR-Cas12a was established, which relies on a color change of gold nanorods (GNRs) caused by the invertase-glucose oxidase cascade reaction and the Fenton reaction for signal readout. A nopaline synthase (NOS) terminator was employed as a model target commonly existing in foreign genes of GMOs. With the help of recombinase-aided amplification, this platform achieved comparable sensitivity of DNA targets (1 aM) with that of a fluorescence reporting assay. As low as 0.1 wt % genetically modified (GM) content in Bt-11 maize was visually observed by unaided eyes, and the semiquantitation of GM ingredients can be obtained within the range of 0.1 to 40 wt % through the absorption measurement of GNRs. Furthermore, five real samples were tested by our method, and the results indicated that the GM ingredient percentages of GMO samples were 2.24 and 24.08 wt %, respectively, while the other three samples were GMO-free. With the advantages of a simple procedure, no need for large or professional instruments, high sensitivity, and selectivity, this platform is expected to provide reasonable technical support for the safe supervision of GMOs.

Scalable Signature-Based Molecular Diagnostics Through On-chip Biomarker Profiling Coupled with Machine Learning

Molecular diagnostics have traditionally relied on discrete biological substances as diagnostic markers. In recent years however, advances in on-chip biomarker screening technologies and data analytics have enabled signature-based diagnostics. Such diagnostics aim to utilize unique combinations of multiple biomarkers or diagnostic 'fingerprints' rather than discrete analyte measurements. This approach has shown to improve both diagnostic accuracy and diagnostic specificity. In this review, signature-based diagnostics enabled by microfluidic and micro-/nano- technologies will be reviewed with a focus on device design and data analysis pipelines and methodologies. With increasing amounts of data available from microfluidic biomarker screening, isolation, and detection platforms, advanced data handling and analytics approaches can be employed. Thus, current data analysis approaches including machine learning and recent advances with image processing, along with potential future directions will be explored. Lastly, the needs and gaps in current literature will be elucidated to inform future efforts towards development of molecular diagnostics and biomarker screening technologies.

Colorimetric Diagnostic Capillary Enabled by Size Sieving in a Porous Hydrogel

Handy and disposable point-of-care diagnostics facilitate the early screening of severe diseases in resource-limited areas. To address urgent needs in inconvenient sites, a simple colorimetric diagnostic device equipped with a capillary tube with porous hydrogel and immunocomplex particles was developed for the rapid detection of biomarkers (16 min). In this device, probe particles attach to capture particles (dp = 40 µm) and form sandwiched immunocomplexes in the presence of target biomarkers, and a red color progressively emerges when the sandwiched immunocomplex particles are blocked by the porous hydrogel embedded inside the glass capillary. Colorimetric aggregation was recorded using a smartphone and analyzed with imaging software. The limit of detection reached 1 ng/mL and showed a maximum of 79% accuracy compared with that obtained through a conventional spectrophotometric technique. The level of a diabetic retinopathy (DR) biomarker, lipocalin-1 (LCN-1), was measured in 1 µL of a human tear sample and used in testing the practicability of the proposed device. All healthy subjects showed lower intensity levels than the other diabetic counterparts (proliferative DR or nonproliferative DR patients), implying the potential of this device in clinical applications. Overall, the diagnostic device facilitates point-of-care-testing and provides a low-cost (~1 USD), compact, and reliable tool for early diagnosis in resource-limited areas.

Magnetic Levitation Systems for Disease Diagnostics

Magnetic levitation (MagLev) is a well-documented, robust technique for density measurements and separations. Although the potential of MagLev as an emerging tool in biotechnology has been recently investigated, the practical use of MagLev in diagnosis and disease detection merits further attention. This review highlights the diagnostic capacity of a simple and portable MagLev system and the possibilities and limitations of the MagLev technique for density-based separation, classification, and manipulation of soft matter and biological systems (e.g., cells, proteins), which in turn may pave the way for the discovery of disease-specific biomarkers.

Development of a sensitive HPLC-MS/MS method for 25-hydroxyvitamin D2 and D3 measurement in capillary blood

Background

Measurement of 25‐hydroxyvitamin D [25(OH)D)] levels is important. The current method requires a relatively large volume of serum. To minimize the amount of serum needed, we established a high‐performance liquid chromatography‐tandem mass spectrometry (HPLC‐MS/MS) method to measure 25(OH)D in capillary serum.

Methods

Venous blood and fingertip blood were collected from 90 participants. Volumes of 100 µL of venous serum and 20 µL of capillary serum were collected. The serum samples were pretreated by protein removal, extraction and concentration, and an HPLC‐MS/MS method based on chromatographic separation and multi reactive ion monitoring was conducted. The intra‐ and inter‐batch variation coefficients were less than 10% for both 25‐hydroxyvitamin D₃[25(OH)D₃] and 25‐hydroxyvitamin D₂[25(OH)D₂)]. For venous specimens, the accuracies were 3.87% and 4.91%, respectively. For capillary specimens, the accuracies were 1.65% and 5.32%, respectively.

Results

The limit of detection (LOD) of 25(OH)D₃ was 0.01 ng/mL, and the LOD of 25(OH)D₂ was 0.05 ng/mL. The results showed that the mean concentration of 25(OH)D in venous blood was 22.56 ± 9.50 ng/mL, while the mean concentration of 25(OH)D in capillary blood was 18.14 ± 7.86 ng/mL. Furthermore, the adjusted capillary blood 25(OH)D level was 22.99 ± 10.24 ng/mL by the correction formula in our study. Similarly, the mean concentration of 25(OH)D₃ in capillary blood was 17.98 ± 7.98 ng/mL. The adjusted capillary blood 25(OH)D₃ level was 22.85 ± 10.42 ng/mL. No difference in the content of 25(OH)D or 25(OH)D₃ was found between venous serum and corrected capillary serum. The correlation coefficients between venous and corrected capillary concentrations of 25(OH)D and 25(OH)D₃ were 0.7941 and 0.8103, respectively, and the areas under the receiver operating characteristic curve were 0.9367 and 0.9565, respectively.

Conclusions

This capillary blood method requires minimal sample preparation and is suitable for routine use in the 25(OH)D detection.

Direct DNA Methylation Profiling with an Electric Biosensor

DNA methylation is one of the principal epigenetic mechanisms that control gene expression in humans, and its profiling provides critical information about health and disease. Current profiling methods require chemical modification of bases followed by sequencing, which is expensive and time-consuming. Here, we report a direct and rapid determination of DNA methylation using an electric biosensor. The device consists of a DNA-tweezer probe integrated on a graphene field-effect transistor for label-free, highly sensitive, and specific methylation profiling. The device performance was evaluated with a target DNA that harbors a sequence of the methylguanine-DNA methyltransferase, a promoter of glioblastoma multiforme, a lethal brain tumor. The results show that we successfully profiled the methylated and nonmethylated forms at picomolar concentrations. Further, fluorescence kinetics and molecular dynamics simulations revealed that the position of the methylation site(s), their proximity, and accessibility to the toe-hold region of the tweezer probe are the primary determinants of the device performance.

A strip test for the optical determination of influenza virus H3 subtype using gold nanoparticle coated polystyrene latex microspheres

A strip test is described for the optical determination of influenza virus H3 subtype. It utilizes gold nanoparticle (AuNP) coated polystyrene latex microspheres (PS) as the label and a sandwich format. The AuNP and PS particles were linked using monoclonal antibodies against influenza virus as the bridge. Under the optimal conditions, the visual detection limit of the AuNP-PS-based strip test was as low as 1/16 hemagglutination unit (HAU). It was 64 times higher than that of 10 nm (4 HAU) AuNP-based strip tests. Quantitative analysis showed that the detection limit of the AuNP-PS-based strip is 0.016 HAU. The AuNP-PS-based strip test showed no cross-reactivity to the other subtypes (H1, H5, H7, or H9) of influenza viruses. Graphical abstract .

Microfabricated electrochemical sensing devices

Electrochemistry provides possibilities to realize smart microdevices of the next generation with high functionalities. Electrodes, which constitute major components of electrochemical devices, can be formed by various microfabrication techniques, and integration of the same (or different) components for that purpose is not difficult. Merging this technique with microfluidics can further expand the areas of application of the resultant devices. To augment the development of next generation devices, it will be beneficial to review recent technological trends in this field and clarify the directions required for moving forward. Even when limiting the discussion to electrochemical microdevices, a variety of useful techniques should be considered. Therefore, in this review, we attempted to provide an overview of all relevant techniques in this context in the hope that it can provide useful comprehensive information.