Recent developments of point-of-care (POC) testing platform for biomolecules

Deep Learning Enabled Universal Multiplexed Fluorescence Detection for Point-of-Care Applications

There is a significant demand for multiplexed fluorescence sensing and detection across a range of applications. Yet, the development of portable and compact multiplexable systems remains a substantial challenge. This difficulty largely stems from the inherent need for spectrum separation, which typically requires sophisticated and expensive optical components. Here, we demonstrate a compact, lens-free, and cost-effective fluorescence sensing setup that incorporates machine learning for scalable multiplexed fluorescence detection. This method utilizes low-cost optical components and a pretrained machine learning (ML) model to enable multiplexed fluorescence sensing without optical adjustments. Its multiplexing capability can be easily scaled up through updates to the machine learning model without altering the hardware. We demonstrate its real-world application in a probe-based multiplexed Loop-Mediated Isothermal Amplification (LAMP) assay designed to simultaneously detect three common respiratory viruses within a single reaction. The effectiveness of this approach highlights the system's potential for point-of-care applications that require cost-effective and scalable solutions. The machine learning-enabled multiplexed fluorescence sensing demonstrated in this work would pave the way for widespread adoption in diverse settings, from clinical laboratories to field diagnostics.

Seamless integration of Internet of Things, miniaturization, and environmental chemical surveillance

IoT is a game-changer across all fields, including chemistry. Embracing sustainable practices and green chemistry, the miniaturization and automation of systems, and their integration into IoT is key to achieving these principles, as a rising trend with momentum. Particularly, IoT and analytical chemistry are linked in the rapid exchange of analytical data for environmental, industrial, healthcare, and educational applications. Meanwhile, cooperation with other fields of science is evident, and there is a prompt and subjective analysis of information related to analytical systems and methodologies. This paper will review the concepts, requirements, and architecture of IoT and its role in the miniaturization and automation of analytical tools using electronic modules and sensors. The aim is to explore the standards and perspectives of IoT and its interaction with different aspects of analytical chemistry. Additionally, it aimed to explain the basics and applications of IoT for chemists, and its relevance to different subfields of analytical chemistry, particularly in the field of environmental chemical surveillance. The article also covers updating IoT devices and creating DIY-based degradation devices to enhance the educational aspect of chemistry and reduce barriers to lab facilities and equipment. Lastly, it will explore how IoT is really important and how it's going to significantly impact analytical chemistry.

Cascaded nanozyme-based high-throughput microfluidic device integrating with glucometer and smartphone for point-of-care pheochromocytoma diagnosis

The development of point-of-care (POC) diagnostics devices for circulating tumor cells (CTCs) detection plays an important role in the early diagnosis of pheochromocytoma (PCC), especially in a low-resource setting. To further realize the rapid, portable, and high-throughput detection of CTCs, an Au@CuMOF cascade enzyme-based microfluidic device for instant point-of-care detection of CTCs was constructed by combining a smartphone application and a commercial portable glucose meter (PGM). In this microfluidic system, DOTA and norepinephrine (NE) modified Au@CuMOF signal probes and Fe3O4@SiO2 capture probes were used for the dual recognition and capture of rare PCC-CTCs. Then, the targeted binding of the Au@CuMOF cascade nanozymes to the CTCs endowed the cellular complexes with multienzyme mimetic activities (i.e., glucose oxidase-like and peroxidase-like activity) to catalyze glucose reduction as signal output for colorimetric and personal glucose meter (PGM) dual-mode detection of CTCs. The developed method has a linear range of 4 to 105 cells mL-1 and a detection limit of 3 cells mL-1. This method allows the simultaneous detection of six samples and demonstrates good applicability for CTCs detection in whole blood samples. More importantly, the combination of PGM, smartphone app and array microfluidic chips enables the rapid, portable, and high-throughput diagnoses of PCC, and providing provide a convenient and reliable alternative to traditional liquid biopsy diagnosis of various cancers.

An IoT-based aptasensor biochip for the diagnosis of periodontal disease

Severe periodontitis affects nearly 1 billion individuals worldwide, highlighting the need for early diagnosis. Here, an integrated system consisting of a microfluidic chip and a portable point-of-care (POC) diagnostic device is developed using a polymethyl methacrylate (PMMA) chip fabrication and a three-dimensional printing technique, which is automatically controlled by a custom-designed smartphone application to routinely assess the presence of a specific periodontitis biomarker, odontogenic ameloblast-associated protein (ODAM). A sandwich-type fluorescence aptasensor is developed on a microfluidic chip, utilizing aptamer pair (MB@OD64 and OD35@FAM) selectively binding to target ODAM. Then this microfluidic chip is integrated into an automated Internet of Things (IoT)-based POC device, where fluorescence intensity, as a signal, from the secondary aptamer binding to ODAM in a sandwich-type binding reaction on the microfluidic chip is measured by a complementary metal oxide semiconductor (CMOS) camera with a 488 nm light-emitting diode (LED) excitation source. Obtained signals are processed by a microprocessor and visualized on a wirelessly connected smartphone application. This integrated biosensor system allows the rapid and accurate detection of ODAM within 30 min with a remarkable limit of detection (LOD) of 0.011 nM under buffer conditions. Clinical application is demonstrated by successfully distinguishing between low-risk and high-risk individuals with 100 % specificity. A strong potential in the translation of this fluorescence-based microfluidic aptasensor integrated with an IoT-based POC system is expected to be employed for non-invasive, on-site, rapid, and accurate ODAM detection, facilitating periodontitis diagnosis.

Three-dimensional DNA biomimetic networks (B-3D Net)-based ratiometric fluorescence platform for cancer-related gene biosensing

Efficient detection of cancer-related nucleic acids is pivotal for early cancer diagnosis. This study introduces a target induced three-dimensional DNA biomimetic networks (B-3D Net)-based ratiometric fluorescence platform using manganese dioxide nanosheets (MnO2 NS)/o-phenylenediamine in combination with hybridization chain reaction to detect cancer-related genes (p53 gene). The incorporation of multiple signals within the B-3D networks can significantly enhance catalytic activity and amplify the output signals, enabling a high sensitivity. Compared with traditional ratio fluorescence platforms, there is no demand to synthesize fluorescent nanoprobes due to the in-situ formation of fluorescence species, which is simple and cost-effective. The corresponding assay demonstrated exceptional sensitivity (with a detection limit as low as 2 fM), selectivity, reproducibility, and accuracy, which mitigates disturbances caused by instrument errors, an inaccurate probe count, and the microenvironment. Furthermore, the ease and straightforwardness of discerning changes in fluorescent brightness and colour by the naked eye are evident. Using the relevant software, a linear relationship between fluorescent images using a smartphone and target concentration was obtained. Hence, the novel ratiometric sensing system will demonstrate new opportunities on determination of target DNA samples in complex biological environments.

S-Doping Regulated Iron Spin States in Fe-N-C Single-Atom Material for Enhanced Peroxidase-Mimicking Activity at Neutral pH

Designing biomimetic nanomaterials with peroxidase (POD)-like activity at neutral pH remains a significant challenge. An S-doping strategy is developed to afford an iron single-atom nanomaterial (Fe1@CN-S) with high POD-like activity under neutral conditions. To the best of knowledge, there is the first example on the achievement of excellent POD-like activity under neutral conditions by regulating the active site structure. S-doping not only promotes the dissociation of the N─H bond in 3,3″,5,5″-tetramethylbenzidine (TMB), but also facilitates the desorption of OH* by the transformation of iron species' spin states from middle-spin (MS FeII) to low-spin (LS FeII). Meanwhile, LS FeII sites typically have more unfilled d orbitals, thereby exhibiting stronger interactions with H2O2 than MS FeII, which can enhance POD-like activity. Finally, a one-pot visual detection of glucose at pH 7 is performed, demonstrating the best selectivity and sensitivity than previous reports.

Evaluation of Fluid Behaviors in a Pushbutton-Activated Microfluidic Device for User-Independent Flow Control

Although numerous studies have been conducted to realize ideal point-of-care testing (POCT), the development of a user-friendly and user-independent power-free microfluidic platform is still a challenge. Among various methods, the finger-actuation method shows a promising technique that provides a user-friendly and equipment-free way of delivering fluid in a designated manner. However, the design criteria and elaborate evaluation of the fluid behavior of a pushbutton-activated microfluidic device (PAMD) remain a critical bottleneck to be widely adopted in various applications. In this study, we have evaluated the fluid behavior of the PAMD based on various parameters, such as pressing velocity and depth assisted by a press machine. We have further developed a user-friendly and portable pressing block that reduces user variation in fluid behavior based on the evaluation.

Low-Cost Arduino Reverse Transcriptase Loop-Mediated Isothermal Amplification (RT-LAMP) for Sensitive Nucleic Acid Detection

This work presents a low-cost transcription loop-mediated isothermal amplification (RT-LAMP) instrument for nucleic acid detection, employing an Arduino Nano microcontroller. The cooling system includes customized printed circuit boards (PCBs) that serve as electrical resistors and incorporate fans. An aluminum block is designed to accommodate eight vials. The system also includes two PCB heaters-one for sample heating and the other for vial lid heating to prevent condensation. The color detection system comprises a TCS3200 color 8-sensor array coupled to one side of the aluminum heater body and a white 8-LED array coupled to the other side, controlled by two Multiplexer/Demultiplexer devices. LED light passes through the sample, reaching the color sensor and conveying color information crucial for detection. The top board is maintained at 110 ± 2 °C, while the bottom board is held at 65 ± 0.5 °C throughout the RT-LAMP assay. Validation tests successfully demonstrated the efficacy of the colorimetric RT-LAMP reactions using SARS-CoV-2 RNA amplification as a sample viability test, achieving 100% sensitivity and 97.3% specificity with 66 clinical samples. Our instrument offers a cost-effective (USD 100) solution with automated result interpretation and superior sensitivity compared to visual inspection. While the prototype was tested with SARS-CoV-2 RNA samples, its versatility extends to detecting other pathogens using alternative primers, showcasing its potential for broader applications in biosensing.

In-droplet cell lysis of AC16 human cardiomyocyte cells via surface acoustic waves

Although several lysis methods are available, biomedical applications are pushing the demand for miniaturised systems and thus for new ways to lyse cells in small volumes. In this work, we demonstrate in-droplet cell lysis of AC16 human cardiomyocyte cells in 20 μL droplets using high frequency surface acoustic waves. The acoustic streaming leads to high shear flow creating porous or breaking the cell membrane and releasing intracellular material. Contrary to previous work where the lysis efficiency is measured by a cell-permeant dye that can be used to determine cell viability, here we propose to quantify the DNA extracted from the cells as a measure of the lysis efficiency. This reagent-free method provides a valuable cell lysis alternative for many biological and biomedical applications, particularly for the development of point-of-care platforms.

Recent Advances in Skin-Interfaced Wearable Sweat Sensors: Opportunities for Equitable Personalized Medicine and Global Health Diagnostics

Recent advances in skin-interfaced wearable sweat sensors enable the noninvasive, real-time monitoring of biochemical signals associated with health and wellness. These wearable platforms leverage microfluidic channels, biochemical sensors, and flexible electronics to enable the continuous analysis of sweat-based biomarkers such as electrolytes, metabolites, and hormones. As this field continues to mature, the potential of low-cost, continuous personalized health monitoring enabled by such wearable sensors holds significant promise for addressing some of the formidable obstacles to delivering comprehensive medical care in under-resourced settings. This Perspective highlights the transformative potential of wearable sweat sensing for providing equitable access to cutting-edge healthcare diagnostics, especially in remote or geographically isolated areas. It examines the current understanding of sweat composition as well as recent innovations in microfluidic device architectures and sensing strategies by showcasing emerging applications and opportunities for innovation. It concludes with a discussion on expanding the utility of wearable sweat sensors for clinically relevant health applications and opportunities for enabling equitable access to innovation to address existing health disparities.

Exploring the Clinical Utility of Raman Spectroscopy for Point-of-Care Cardiovascular Disease Biomarker Detection

A variety of innovative point-of-care (POC) solutions using Raman systems have been explored. However, the vast effort is in assay development, while studies of the characteristics required for Raman spectrometers to function in POC applications are lacking. In this study, we tested and compared the performance of eight commercial Raman spectrometers ranging in size from benchtop Raman microscopes to portable and handheld Raman spectrometers using paper fluidic cartridges, including their ability to detect cardiac troponin I and heart fatty acid binding protein, both of which are well-established biomarkers for evaluating cardiovascular health. Each spectrometer was evaluated in terms of excitation wavelength, laser characteristics, and ease of use to investigate POC utility. We found that the Raman spectrometers equipped with 780 and 785 nm laser sources exhibited a reduced background signal and provided higher sensitivity compared to those with 633 and 638 nm laser sources. Furthermore, the spectrometer equipped with the single acquisition line readout functionality showed improved performance when compared to the point scan spectrometers and allowed measurements to be made faster and easier. The portable and handheld spectrometers also showed similar detection sensitivity to the gold standard instrument. Lastly, we reduced the laser power for the spectrometer with single acquisition line readout capability to explore the system performance at a laser power that change the classification from a Class 3B laser device to a Class 3R device and found that it showed comparable performance. Overall, these findings show that portable Raman spectrometers have the potential to be used in POC settings with accuracy comparable to laboratory-grade instruments, are relatively low-cost, provide fast signal readout, are easy to use, and can facilitate access for underserved communities.

Programmable magnetic robot (ProMagBot) for automated nucleic acid extraction at the point of need

Upstream sample preparation remains the bottleneck for point-of-need nucleic acid testing due to its complexity and time-consuming nature. Sample preparation involves extracting, purifying, and concentrating nucleic acids from various matrices. These processes are critical for ensuring the accuracy and sensitivity of downstream nucleic acid amplification and detection. However, current sample preparation methods are often laboratory-based, requiring specialized equipment, trained personnel, and several hours of processing time. As a result, sample preparation often limits the speed, portability, and cost-effectiveness of point-of-need nucleic acid testing. A universal, field-deployable sample preparation device is highly desirable for this critical need and unmet challenge. Here we reported a handheld, battery-powered, reconfigurable, and field-deployable nucleic acid sample preparation device. A programmable electromagnetic actuator was developed to drive a magnetic robot (ProMagBot) in X/Y 2D space, such that various magnetic bead-based sample preparations can be readily translated from the laboratory to point-of-need settings. The control of the electromagnetic actuator requires only a 3-phase unipolar voltage in X and Y directions, and therefore, the motion space is highly scalable. We validated the ProMagBot device with a model application by extracting HIV viral RNAs from plasma samples using two widely used magnetic bead kits: ChargeSwitch and MagMAX beads. In both cases, the ProMagBot could successfully extract viral RNAs from 50 μL plasma samples containing as low as 102 copies of viral RNAs in 20 minutes. Our results demonstrated the ability of ProMagBot to prepare samples from complex mediums at the point of need. We believe such a device would enable rapid and robust sample preparation in various settings, including resource-limited or remote environments, and accelerate the development of next-generation point-of-need nucleic acid testing.

Metal ions-regulated chemical vapor generation of Hg2+:mechanism and application in miniaturized point discharge atomic emission spectrometry assay of oxalate in clinical urolithiasis samples

It is well known that the coexisting metal ions could significantly influence the atomic spectroscopy (AS) analysis. In this work, a cation-modulated mercury ions (Hg²⁺) strategy via chemical vapor generation (CVG) was developed for oxalate assay due to the phenomenon that the Ag ⁺ can significantly reduce the Hg²⁺ signal. The regulation effect was studied in depth via experimental investigations. Since Ag ⁺ can be reduced to silver nanoparticles (Ag NPs) by reductant SnCl₂, the decrease of the Hg²⁺ signal is attributed to the formation of a silver-mercury (Ag-Hg) amalgam. Due to the oxalate can react with Ag ⁺ to generate Ag₂C₂O₄, which can reduce the generation of Ag-Hg amalgam, a portable and low-power point discharge chemical vapor generation atomic emission spectrometry (PD-CVG-AES) system was constructed to quantify the content of oxalate via monitoring the signal of Hg²⁺. Under optimal conditions, the limit of detection (LOD) was as low as 40 nM in the range of 0.1-10 μM for oxalate assay, while exhibiting good specificity. This method was applied to quantitative oxalate in 50 clinical urine samples of urinary stones patients. The levels of oxalate detected in clinical samples were consistent with clinical imaging results, which is promising for point-of-care testing in clinical diagnosis.

Fluorescence-Based Portable Assays for Detection of Biological and Chemical Analytes

Fluorescence-based detection techniques are part of an ever-expanding field and are widely used in biomedical and environmental research as a biosensing tool. These techniques have high sensitivity, selectivity, and a short response time, making them a valuable tool for developing bio-chemical assays. The endpoint of these assays is defined by changes in fluorescence signal, in terms of its intensity, lifetime, and/or shift in spectrum, which is monitored using readout devices such as microscopes, fluorometers, and cytometers. However, these devices are often bulky, expensive, and require supervision to operate, which makes them inaccessible in resource-limited settings. To address these issues, significant effort has been directed towards integrating fluorescence-based assays into miniature platforms based on papers, hydrogels, and microfluidic devices, and to couple these assays with portable readout devices like smartphones and wearable optical sensors, thereby enabling point-of-care detection of bio-chemical analytes. This review highlights some of the recently developed portable fluorescence-based assays by discussing the design of fluorescent sensor molecules, their sensing strategy, and the fabrication of point-of-care devices.

Recent advances in lab-on-a-chip systems for breast cancer metastasis research

Breast cancer is the leading cause of cancer-related deaths in women. Multiple molecular subtypes, heterogeneity, and their ability to metastasize from the primary site to distant organs make breast cancer challenging to diagnose, treat, and obtain the desired therapeutic outcome. As the clinical importance of metastasis is dramatically increasing, there is a need to develop sustainable in vitro preclinical platforms to investigate complex cellular processes. Traditional in vitro and in vivo models cannot mimic the highly complex and multistep process of metastasis. Rapid progress in micro- and nanofabrication has contributed to soft lithography or three-dimensional printing-based lab-on-a-chip (LOC) systems. LOC platforms, which mimic in vivo conditions, offer a more profound understanding of cellular events and allow novel preclinical models for personalized treatments. Their low cost, scalability, and efficiency have resulted in on-demand design platforms for cell, tissue, and organ-on-a-chip platforms. Such models can overcome the limitations of two- and three-dimensional cell culture models and the ethical challenges involved in animal models. This review provides an overview of breast cancer subtypes, various steps and factors involved in metastases, existing preclinical models, and representative examples of LOC systems used to study and understand breast cancer metastasis and diagnosis and as a platform to evaluate advanced nanomedicine for breast cancer metastasis.

Ultra-small highly fluorescent zinc-based metal organic framework nanodots for ratiometric visual sensing of tetracycline based on aggregation induced emission

Color tonality by intrinsic fluorescent metal-organic frameworks (MOFs) is highly desirable in bioanalytical applications due to its stability, low-cost and robustness with no need for functionalization and/or encapsulation of fluorophores. In the present work, ultra-small and higly fluorescent zinc-based MOFs (FMOF-5) were synthesized. The prepared FMOFs were around 5 nm in size, and gave strong blue emission at 440 nm when excited at 350 nm. Interestingly, tetracycline (TC) selectively tuned the blue emission of FMOF-5 to greenish-yellow emission (520 nm) with dramatic enhancement through aggregation induced emission (AIE). The fluorimetric analysis of TC was carried out through the ratiometric peak intensities of F520/F440, with detection limit (LOD) of 5 nM. To realize quantitative point-of-care based on color tonality, a smartphone integrated with the ratiometric visual platform was thereby design. Hence, TC was visually detected with LOD of 10 nM. The prepared FMOF-5-based probe showed high stability (3 months) and reusability (∼10 times). The developed visual-based platform presents great promise for practical point of care testing due to its low-cost, robustness, ruggedness, simple operation, and excellent selectivity and repeatability.

Threaded 3D microfluidic paper analytical device-based ratiometric fluorescent sensor for background-free and visual detection of organophosphorus pesticides

With the increasing concerns of food safety and environmental protection, it is desirable to develop reliable, effective, and portable sensors for detection of organophosphorus pesticides (OPs). Here, a cascade reaction system integrated with threaded 3D microfluidic paper analytical device (3D μPAD) was firstly developed for background-free and visual detection of OPs in agricultural samples. Butyrylcholinesterase (BChE) hydrolyzed acetylcholine into thiocholine (TCh), which reduced MnO₂ nanosheets into Mn²⁺. With addition of OPs, BChE activity was irreversibly inhibited, and the generation of TCh and the reduction of MnO₂ nanosheets were prevented. Then the remaining MnO₂ nanosheets oxidized o-phenylenediamine into 2,3-diaminophenazine with yellow-emission fluorescence, which quenched the fluorescence intensity of red-emission carbon dots (RCDs) via inner-filter effect. Based on above mechanism, a ratiometric fluorescent system was established for OPs detection. Threaded 3D μPAD consisted of 4 layers, which allowed to load and/or add reagents to trigger the cascade reaction system for OPs detection. The fluorescent images presented distinguishable color variations from red to yellow with dichlorvos concentrations ranging from 2.5 to 120 μg L^-1, and the limit of detection was 1.0 μg L^-1. In the practical samples testing, threaded 3D μPAD can eliminate background influence on fluorescent signal for OPs detection. Threaded 3D μPAD integrated with ratiometric sensing platform has merits of accuracy response, facile operation, and background-free detection, which supplies a new alternative approach for on-site pesticide detection.

A Review of Magnetic Nanoparticle-Based Surface-Enhanced Raman Scattering Substrates for Bioanalysis: Morphology, Function and Detection Application

Surface-enhanced Raman scattering (SERS) is a kind of popular non-destructive and water-free interference analytical technology with fast response, excellent sensitivity and specificity to trace biotargets in biological samples. Recently, many researches have focused on the preparation of various magnetic nanoparticle-based SERS substrates for developing efficient bioanalytical methods, which greatly improved the selectivity and accuracy of the proposed SERS bioassays. There has been a rapid increase in the number of reports about magnetic SERS substrates in the past decade, and the number of related papers and citations have exceeded 500 and 2000, respectively. Moreover, most of the papers published since 2009 have been dedicated to analytical applications. In the paper, the recent advances in magnetic nanoparticle-based SERS substrates for bioanalysis were reviewed in detail based on their various morphologies, such as magnetic core-shell nanoparticles, magnetic core-satellite nanoparticles and non-spherical magnetic nanoparticles and their different functions, such as separation and enrichment, recognition and SERS tags. Moreover, the typical application progress on magnetic nanoparticle-based SERS substrates for bioanalysis of amino acids and protein, DNA and RNA sequences, cancer cells and related tumor biomarkers, etc., was summarized and introduced. Finally, the future trends and prospective for SERS bioanalysis by magnetic nanoparticle-based substrates were proposed based on the systematical study of typical and latest references. It is expected that this review would provide useful information and clues for the researchers with interest in SERS bioanalysis.

Angiotensin-Converting Enzyme 2-Based Biosensing Modalities and Devices for Coronavirus Detection

Rapid and cost-effective diagnostic tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are a critical and valuable weapon for the coronavirus disease 2019 (COVID-19) pandemic response. SARS-CoV-2 invasion is primarily mediated by human angiotensin-converting enzyme 2 (hACE2). Recent developments in ACE2-based SARS-CoV-2 detection modalities accentuate the potential of this natural host-virus interaction for developing point-of-care (POC) COVID-19 diagnostic systems. Although research on harnessing ACE2 for SARS-CoV-2 detection is in its infancy, some interesting biosensing devices have been developed, showing the commercial viability of this intriguing new approach. The exquisite performance of the reported ACE2-based COVID-19 biosensors provides opportunities for researchers to develop rapid detection tools suitable for virus detection at points of entry, workplaces, or congregate scenarios in order to effectively implement pandemic control and management plans. However, to be considered as an emerging approach, the rationale for ACE2-based biosensing needs to be critically and comprehensively surveyed and discussed. Herein, we review the recent status of ACE2-based detection methods, the signal transduction principles in ACE2 biosensors and the development trend in the future. We discuss the challenges to development of ACE2-biosensors and delineate prospects for their use, along with recommended solutions and suggestions.

Emergence of infectious diseases and role of advanced nanomaterials in point-of-care diagnostics: a review

Infectious outbreaks are the foremost global public health concern, challenging the current healthcare system, which claims millions of lives annually. The most crucial way to control an infectious outbreak is by early detection through point-of-care (POC) diagnostics. POC diagnostics are highly advantageous owing to the prompt diagnosis, which is economical, simple and highly efficient with remote access capabilities. In particular, utilization of nanomaterials to architect POC devices has enabled highly integrated and portable (compact) devices with enhanced efficiency. As such, this review will detail the factors influencing the emergence of infectious diseases and methods for fast and accurate detection, thus elucidating the underlying factors of these infections. Furthermore, it comprehensively highlights the importance of different nanomaterials in POCs to detect nucleic acid, whole pathogens, proteins and antibody detection systems. Finally, we summarize findings reported on nanomaterials based on advanced POCs such as lab-on-chip, lab-on-disc-devices, point-of-action and hospital-on-chip. To this end, we discuss the challenges, potential solutions, prospects of integrating internet-of-things, artificial intelligence, 5G communications and data clouding to achieve intelligent POCs.

Cilostazol-imprinted polymer film-coated electrode as an electrochemical chemosensor for selective determination of cilostazol and its active primary metabolite

An electrochemical chemosensor for cilostazol (CIL) determination was devised, engineered, and tested. For that, a unique conducting film of the functionalized thiophene-appended carbazole-based polymer, molecularly imprinted with cilostazol (MIP-CIL), was potentiodynamically deposited on a Pt disk electrode by oxidative electropolymerization. Thanks to electro-oxidation potentials lower than that of CIL, the carbazole monomers outperformed pyrrole, thiophene, and phenol monomers, in this electropolymerization. The pre-polymerization complexes quantum-mechanical and molecular dynamics analysis allowed selecting the most appropriate monomer from the three thiophene-appended carbazoles examined. The electrode was then used as a selective CIL chemosensor in the linear dynamic concentration range of 50 to 924 nM with a high apparent imprinting factor, IF = 10.6. The MIP-CIL responded similarly to CIL and CIL's pharmacologically active primary metabolite, 3,4-dehydrocilostazol (dhCIL), thus proving suitable for their determination together. Simulated models of the MIP cavities binding of the CIL, dhCIL, and interferences' molecules allowed predicting chemosensor selectivity. The MIP film sorption of CIL and dhCIL was examined using DPV by peak current data fitting with the Langmuir (L), Freundlich (F), and Langmuir-Freundlich (LF) isotherms. The LF isotherm best described this sorption with the sorption equilibrium constant (K_LF) for CIL and dhCIL of 12.75 × 10^-6 and 0.23 × 10^-6 M, respectively. Moreover, the chemosensor cross-reactivity to common interferences study resulted in the selectivity to cholesterol and dehydroaripiprazole of 1.52 and 8.0, respectively. The chemosensor proved helpful in determining CIL and dhCIL in spiked human plasma with appreciable recovery (99.3-134.1%) and limit of detection (15 nM).

Portable, multi-modal Raman and fluorescence spectroscopic platform for point-of-care applications

SIGNIFICANCE

Point-of-care (POC) platforms utilizing optical biosensing strategies can achieve on-site detection of biomarkers to improve the quality of care for patients in low-resource settings.

AIM

We aimed to develop a portable, multi-modal spectroscopic platform capable of performing Raman and fluorescence measurements from a single sample site.

APPROACH

We designed the spectroscopic platform in OpticStudio using commercial optical components and built the system on a portable optical breadboard. Two excitation and collection arms were utilized to detect the two optical signals. The multi-modal functionality was validated using ratiometric Raman/fluorescence samples, and the potential utility was demonstrated using a model bioassay for cardiac troponin I.

RESULTS

The designed spectroscopic platform achieved a spectral resolution of 0.67 ± 0.2 nm across the Raman detection range (660 to 770 nm). The ratiometric Raman/fluorescence samples demonstrated no crosstalk between the two detector arms across a gradient of high molar concentrations. Testing of the model bioassay response showed that the integrated approach improved the linearity of the calibration curve from (R² = 0.977) for the Raman only and (R² = 0.972) for the fluorescence only to (R2 = 0.988) for the multi-modal approach.

CONCLUSION

These findings demonstrate the potential impact of a multi-modal POC spectroscopic platform to improve the sensitivity and robustness necessary for biomarker detection.

Intradermal Glycine Detection with a Wearable Microneedle Biosensor: The First In Vivo Assay

Glycine (GLY) is gaining importance in medical diagnoses due to its relationship with multiple physiological functions. Today, GLY is exclusively analyzed using instrumentation centralized in clinical labs, and a tangible point-of-care tool that gathers real-time data from the patient for effective and fast evaluations is lacking. Relevant clinical advances are expected as soon as the rapid provision of both punctual and continuous measurements is possible. In that context, this work presents a microneedle (MN)-based biosensor for intradermal GLY detection in interstitial fluid (ISF). The MN tip is externally tailored to detect GLY levels through the hydrogen peroxide formed in its reaction with a quinoprotein-based GLY oxidase enzyme. The analytical performance of the MN biosensor indicates a fast response time (<7 s); acceptable reversibility, reproducibility, and stability; as well as a wide linear range of response (25–600 μM) that covers the physiological levels of GLY in ISF. The MN biosensor conveniently exhibits high selectivity for GLY over other compounds commonly found in ISF, and the response is not influenced by temperature, pH, or skin insertions. Validated intradermal measurements of GLY were obtained at the in vitro (with pieces of rat skin), ex vivo (on-body tests of euthanized rats) and in vivo (on-body tests of anesthetized rats) levels, demonstrating its ability to produce accurate physiological data. The developed GLY MN biosensor is skin-wearable and provides reliable, real-time intradermal GLY measurements in ISF by means of a minimally invasive approach.

Asymmetric Mach–Zehnder Interferometric Biosensing for Quantitative and Sensitive Multiplex Detection of Anti-SARS-CoV-2 Antibodies in Human Plasma

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic has once more emphasized the urgent need for accurate and fast point-of-care (POC) diagnostics for outbreak control and prevention. The main challenge in the development of POC in vitro diagnostics (IVD) is to combine a short time to result with a high sensitivity, and to keep the testing cost-effective. In this respect, sensors based on photonic integrated circuits (PICs) may offer advantages as they have features such as a high analytical sensitivity, capability for multiplexing, ease of miniaturization, and the potential for high-volume manufacturing. One special type of PIC sensor is the asymmetric Mach–Zehnder Interferometer (aMZI), which is characterized by a high and tunable analytical sensitivity. The current work describes the application of an aMZI-based biosensor platform for sensitive and multiplex detection of anti-SARS-CoV-2 antibodies in human plasma samples using the spike protein (SP), the receptor-binding domain (RBD), and the nucleocapsid protein (NP) as target antigens. The results are in good agreement with several CE-IVD marked reference methods and demonstrate the potential of the aMZI biosensor technology for further development into a photonic IVD platform.

Laser-assisted surface activation for fabrication of flexible non-enzymatic Cu-based sensors

A rapid and effective technique has been develped for the fabrication of sensor-active copper-based materials on the surface of such flexible polymers as terephthalate, polyethylene naphthalate, and polyimide using the method of laser surface modification. For this purpose, we optimized the polymer surface activation parameters using laser sources with a picosecond pulse duration for subsequent selective metallization within the activated region. Furthermore, the fabricated copper structures were modified with gold nanostructures and by electrochemical passivation to produce copper-gold and oxide-containing copper species, respectively. As a result, in comparison with pure copper electrodes, these composite materials exhibit much better electrocatalytic performance concerning the non-enzymatic identification of biologically important disease markers such as glucose, hydrogen peroxide, and dopamine.

Microfluidics-based strategies for molecular diagnostics of infectious diseases

Traditional diagnostic strategies for infectious disease detection require benchtop instruments that are inappropriate for point-of-care testing (POCT). Emerging microfluidics, a highly miniaturized, automatic, and integrated technology, are a potential substitute for traditional methods in performing rapid, low-cost, accurate, and on-site diagnoses. Molecular diagnostics are widely used in microfluidic devices as the most effective approaches for pathogen detection. This review summarizes the latest advances in microfluidics-based molecular diagnostics for infectious diseases from academic perspectives and industrial outlooks. First, we introduce the typical on-chip nucleic acid processes, including sample preprocessing, amplification, and signal read-out. Then, four categories of microfluidic platforms are compared with respect to features, merits, and demerits. We further discuss application of the digital assay in absolute nucleic acid quantification. Both the classic and recent microfluidics-based commercial molecular diagnostic devices are summarized as proof of the current market status. Finally, we propose future directions for microfluidics-based infectious disease diagnosis.

Hydrogel-Involved Colorimetric Platforms Based on Layered Double Oxide Nanozymes for Point-of-Care Detection of Liver-Related Biomarkers

Monitoring the liver status in a convenient and low-cost way is significant for obtaining a warning about drug-indued liver diseases promptly. Herein, we designed a novel colorimetric point-of-care (POC) platform for the determination of three liver-related biomarkers─aspartate transaminase (AST), alanine transaminase (ALT), and alkaline phosphatase (ALP). This platform integrated agarose hydrogels into a portable device, where hydrogels were loaded with nanozymes and different reaction substances for triggering specific reactions and generating colorimetric signals. Typically, Au-decorated CoAl-layered double oxide (Au/LDO) was for the first time developed as the nanozyme with peroxidase (POD) mimic activity, which can accelerate the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxTMB with the coexistence of hydrogen peroxide (H₂O₂). The detection mechanism of AST and ALT is based on the fact that they can cause individual cascade reactions to generate H₂O₂, and H₂O₂ further activates the Au/LDO nanozyme to catalyze the chromogenic reaction of TMB. As for ALP, it can catalytically hydrolyze l-ascorbic acid-2-phosphate to ascorbic acid. The latter then discolored the oxTMB that was produced with the assistance of Au/LDO. Teaming up with a smartphone, the color information of hydrogels can be converted to hue values, which allow quantitative analysis of ALT, AST, and ALP with detection limits of 15, 10, and 5 U/L, respectively. Moreover, the simple and cost-effective platform was successfully applied for the simultaneous determination of the three analytes in human plasma. Additionally, since the hydrogel is disposable and can be replaced by new ones loaded with different reaction regents, the platform is expected to serve the POC testing of various chem/bio targets.

Comparative Study of Four Coloured Nanoparticle Labels in Lateral Flow Immunoassay

The detection limit of lateral flow immunoassay (LFIA) is largely determined by the properties of the label used. We compared four nanoparticle labels differing in their chemical composition and colour: (1) gold nanoparticles (Au NPs), red; (2) Au-core/Pt-shell nanoparticles (Au@Pt NPs), black; (3) latex nanoparticles (LPs), green; and (4) magnetic nanoparticles (MPs), brown. The comparison was carried out using one target analyte—Erwinia amylovora, the causal bacterial agent of fire blight. All nanoparticles were conjugated with antibodies through methods that provide maximum functional coverage like physical adsorption (Au NPs, Au@Pt NPs) and covalent bonding (LPs, MPs). All conjugates demonstrated the same ability to bind with E. amylovora through enzyme-linked immunosorbent assay where optical properties of the nanoparticles do not determine the registered signal. However, half-maximal binding was achieved at different numbers of nanoparticles because they differ in size. All conjugates based on four nanoparticle labels were used for lateral flow assays. As a result, Au@Pt NPs provided the minimal detection limit that corresponded to 10³ CFU/mL. Au NPs and LPs detected 10⁴ CFU/mL, and MPs detected 10⁵ CFU/mL. The results highlight that simply choosing a coloured label can significantly affect the detection limit of LFIA.

Lanthanide upconversion and downshifting luminescence for biomolecules detection

Biomolecules play critical roles in biological activities and are closely related to various disease conditions. The reliable, selective and sensitive detection of biomolecules holds much promise for specific and rapid biosensing. In recent years, luminescent lanthanide probes have been widely used for monitoring the activity of biomolecules owing to their long luminescence lifetimes and line-like emission which allow time-resolved and ratiometric analyses. In this review article, we concentrate on recent advances in the detection of biomolecule activities based on lanthanide luminescent systems, including upconversion luminescent nanoparticles, lanthanide-metal organic frameworks, and lanthanide organic complexes. We also introduce the latest remarkable accomplishments of lanthanide probes in the design principles and sensing mechanisms, as well as the forthcoming challenges and perspectives for practical achievements.

Integrated Microfluidic-Based Platforms for On-Site Detection and Quantification of Infectious Pathogens: Towards On-Site Medical Translation of SARS-CoV-2 Diagnostic Platforms

The rapid detection and quantification of infectious pathogens is an essential component to the control of potentially lethal outbreaks among human populations worldwide. Several of these highly infectious pathogens, such as Middle East respiratory syndrome (MERS) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), have been cemented in human history as causing epidemics or pandemics due to their lethality and contagiousness. SARS-CoV-2 is an example of these highly infectious pathogens that have recently become one of the leading causes of globally reported deaths, creating one of the worst economic downturns and health crises in the last century. As a result, the necessity for highly accurate and increasingly rapid on-site diagnostic platforms for highly infectious pathogens, such as SARS-CoV-2, has grown dramatically over the last two years. Current conventional non-microfluidic diagnostic techniques have limitations in their effectiveness as on-site devices due to their large turnaround times, operational costs and the need for laboratory equipment. In this review, we first present criteria, both novel and previously determined, as a foundation for the development of effective and viable on-site microfluidic diagnostic platforms for several notable pathogens, including SARS-CoV-2. This list of criteria includes standards that were set out by the WHO, as well as our own "seven pillars" for effective microfluidic integration. We then evaluate the use of microfluidic integration to improve upon currently, and previously, existing platforms for the detection of infectious pathogens. Finally, we discuss a stage-wise means to translate our findings into a fundamental framework towards the development of more effective on-site SARS-CoV-2 microfluidic-integrated platforms that may facilitate future pandemic diagnostic and research endeavors. Through microfluidic integration, many limitations in currently existing infectious pathogen diagnostic platforms can be eliminated or improved upon.

Nanobiotechnology as a platform for the diagnosis of COVID-19: a review

A sensitive method for diagnosing coronavirus disease 2019 (COVID-19) is highly required to fight the current and future global health threats due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV 2). However, most of the current methods exhibited high false‐negative rates, resulting in patient misdiagnosis and impeding early treatment. Nanoparticles show promising performance and great potential to serve as a platform for diagnosing viral infection in a short time and with high sensitivity. This review highlighted the potential of nanoparticles as platforms for the diagnosis of COVID-19. Nanoparticles such as gold nanoparticles, magnetic nanoparticles, and graphene (G) were applied to detect SARS-CoV 2. They have been used for molecular-based diagnosis methods and serological methods. Nanoparticles improved specificity and shorten the time required for the diagnosis. They may be implemented into small devices that facilitate the self-diagnosis at home or in places such as airports and shops. Nanoparticles-based methods can be used for the analysis of virus-contaminated samples from a patient, surface, and air. The advantages and challenges were discussed to introduce useful information for designing a sensitive, fast, and low-cost diagnostic method. This review aims to present a helpful survey for the lesson learned from handling this outbreak to prepare ourself for future  pandemic.