Afterglow Nanoprobe-Enabled Quantitative Lateral Flow Immunoassay by a Palm-Size Device for Household Healthcare.

Lateral flow immunoassay (LFIA), a classical point-of-care testing (POCT) technique, plays an important role in disease screening and healthcare monitoring. However, traditional LFIA is either designed for qualitative analysis or requires expensive equipment for quantification, limiting its use in household diagnosis. In this study, we proposed a new generation of LFIA for household health monitoring by using ultralong organic phosphorescence (UOP) nanomaterials as afterglow nanoprobes with a self-developed palm-size sensing device. The UOP nanoprobes exhibit a phosphorescence signal with a second-level lifetime, which completely avoids the interference from excitation light and biological background fluorescence. Therefore, an ultraminiaturized and low-cost UOP nanosensor was successfully designed by eliminating the complex optical path and filtering systems. We chose an inflammatory factor, C-reactive protein (CRP), for household POCT validation. The whole analysis was completed within 9 min. A limit of detection (LOD) of 0.54 ng/mL of CRP antigen was achieved with high stability and good specificity, which is comparable to laboratory instruments and fully satisfying the clinical diagnosis requirement.

Portable dual-channel blood enzyme analyzer for point-of-care liver function detection.

Because the liver is an important metabolic center in the human body, the reliability and timeliness of chronic liver disease diagnosis are particularly important. Alanine aminotransferase and aspartate transaminase are the two most important liver function indicators, and their test results are crucial in the diagnosis of liver diseases. However, the simultaneous detection of these two indicators is currently restricted by the need for expensive equipment and complicated detection processes. This study proposes a portable dual-channel blood enzyme analyzer (BEA) for point-of-care-testing. The device uses photometric reflectance to quantify the enzyme concentration by evaluating the reflected light intensity. The BEA also precisely controls and maintains the temperature at 37 °C ± 0.1 °C in the dual-channel assay. We assessed the responses of this system within a clinically relevant range by testing blood samples from a local hospital. The test verified that BEA for ALT and AST achieved a detection limit of 3.5 U L-1 and 4 U L-1, detection range of 4-350 U L-1 and 4-250 U L-1, coefficients of variation (CV) that were both less than 10%, and a linear correlation coefficient of 0.9827 and 0.9714 compared with a high-precision clinical biochemistry analyzer (Roche Cobas C702), respectively. We realized remote data analysis and storage through connection with smartphones, which can be applied to remote diagnostics and preventative personal disease management. Therefore, BEA has broad application prospects in the future internet of medical things.

Surface plasmonic biosensors: principles, designs and applications.

Recently, surface plasmon resonance (SPR) biosensors have been widely used in environmental monitoring, food contamination detection and diagnosing medical conditions due to their superior sensitivity, label-free detection and rapid analysis speed. This paper briefly elaborates on the development history of SPR technology and introduces SPR signal sensing principles. A summary of recent applications of SPR sensors in different fields is highlighted, including their figures of merit and limitations. Finally, the personal perspectives and future development trends about sensor preparation and design are discussed in detail, which may be critical for improving the performance of SPR sensors.

Magnetic nanoprobe-enabled lateral flow assays: recent advances.

In recent years, magnetic nanoparticle sensor technologies have attracted considerable interest in the point-of-care-testing (POCT) field, especially in lateral flow immunoassays (LFIAs). Although the visual signal of magnetic nanoparticles is reduced during an inspection, it can be compensated for by magnetic induction, and detection results can be quantified by magnetic sensors. Sensors that use magnetic nanoparticles (MNPs) as markers can overcome the high background noise of complex samples. In this study, MNP signal detection strategies are described from the perspectives of magnetoresistance, magnetic flux, frequency mixing technology, and magnetic permeability, and the principles and development of each technology are introduced in detail. Typical applications of magnetic nanoparticle sensor technologies are introduced. By describing the advantages and limitations of different sensing strategies, we highlight the development and improvement directions of different sensing strategies. In general, the future development of magnetic nanoparticle sensor technologies will be toward intelligent, convenient, and mobile high-performance detection equipment.

A lab-on-disc centrifugal microfluidic system for ultraprecise plasma separation.

As the medical community puts forward higher requirements for the speed and convenience of disease diagnosis, point-of-care testing has become a hot research topic to overcome various kinds of healthcare problems. Blood test is considered to be highly sensitive and accurate in clinical diagnosis. However, conventional plasma separation system tends to be bulky and needs professional operations. Moreover, imprecise separation may cause residual biochemical substances such as blood cells to affect the detection results. In this work, to solve these problems, we designed a portable centrifugal microfluidic platform for automatic, rapid and ultraprecise blood separation. The disc consists of multichambers and multi-microchannels where a plasma reservoir and a cell reservoir are connected to each other and collinear with the center of the circle. This structure overcomes the weakness of low separation efficiency (when hematocrit increases) under the traditional blood separation structure (bifurcation structure). As a result, the proposed system achieved 99.9% plasma purity, 99.9% separation efficiency (with a blood hematocrit of 48%) and 32.5% plasma recovery rate in the 50s, which provides a strong guarantee for rapid blood diagnosis and analysis, especially in areas where medical resources are limited.

A low-cost compact blood enzyme analyzer based on optical sensing for point-of-care liver function testing.

Serum alanine aminotransferase (ALT) is the most sensitive indicator of liver function; therefore, in clinical practice, its detection has diagnostic significance. However, hepatotoxicity monitoring is constrained in resource-limited areas due to the high cost and expensive equipment. This article describes a low-cost, compact blood enzyme analyzer (BEA) for point-of-care (PoC) liver function testing that uses reflection photometry to quantitate the colorimetric enzyme assay results. Moreover, the analyzer incorporates rapid and constant 37 °C temperature control to ensure that human serum enzymes remain active. The BEA was used to evaluate ALT in 50 whole blood samples using PoC photochemical test strips. The test results showed a linear correlation coefficient of 0.9749 compared with a clinical-specific biochemical analyzer and coefficients of variation (CV)% less than 5%. It has a low detection limit of 3.62 U L-1 and a wide detection range of 4-480 U L-1. In addition, the BEA enables smartphone access to the Internet of Medical Things (IoMT) via Bluetooth to facilitate active chronic disease management or remote diagnosis in PoC settings. Therefore, the BEA is a promising system for health management using the IoMT.

An automatic whole blood analyzer for renal function analysis with a centrifugal microfluidic device.

In recent years, chronic kidney disease (CKD) has received widespread attention as one of the fastest growing non-communicable diseases (NCD) worldwide. Here, a clinical biochemical detection system based on a centrifugal microfluidic chip was designed to simplify the rapid detection of renal function indices. A photosensor was used to design an optical signal acquisition structure that can detect products or substrates after enzymatic reactions of uric acid, creatinine, and urea. The weak optical signals collected from this structure were processed using a pre-designed amplifying circuit and a software algorithm to calculate absorbance. The relationship between absorbance and concentration was established according to the Beer-Lambert law. The results indicated good stability and accuracy of the system, which is 21.3 cm × 16.5 cm × 19 cm in size as compared to other detection systems due to the adoption of a centrifugal microfluidic chip. It was portable and easy to operate, in addition to its ability to rapidly detect renal function indices. This system exhibits great potential for the detection of highly integrated point-of-care testing in the future.

3D printed microfluidic Coulter counter for blood cell analysis.

Coulter counters are ubiquitous in everyday life; however, with reduced orifice size shrinkage, there is an increased risk of clogging. Herein, a 3D microfluidic printing-based single-use kit is presented for analyzing biological samples and performing accurate Coulter cell count analysis (e.g., white blood cells in the blood). The gem hole eliminates the traditional design concept of integration inside the detection instrument, innovatively causing it to be independent from the analysis instrument. Further, integrating the hole in the analysis box enables the design of a separate detection module. The analysis box is disposable, convenient, and hygienic; avoids cross-infection; solves the problem of clogging of tiny holes from a new perspective; and no longer requires uneconomical and inconvenient methods, such as flushing, cauterization, and fluid focusing, through solid water flow. Further development of the newly designed 3D printing analysis box can enable its extensive use in POCT (point-of-care) detection scenarios. Moreover, through mass production, the issue of cost will be eliminated.

Integrated electrochemical lateral flow immunoassays (eLFIAs): recent advances.

The discovery of electroactive nano-biomaterials and the development of flexible electrodes have increased the interest in applications of integrated electrochemical lateral flow immunoassays (eLFIAs), which integrate electrochemical nanotags and flexible electrodes on test strips that can easily detect small biomolecules. Compared with colorimetric, optical, magnetic and other highly sensitive detection methods, the electrochemical detection technique is well developed with high sensitivity, selectivity and repeatability. Moreover, the increasing compatibility of interfaces with miniature potentiometers has allowed electrochemical sensors to become more integrated, automated and intelligent, highlighting their huge potential in future developments. This review discusses the relevant eLFIA research over the past 20 years. The basic principles, electrode assemblies, electrochemical labeling strategies and electrical signal detection methods are summarized and analyzed in detail. Finally, perspectives on the current challenges facing eLFIA and its future outlook are presented.

Self-propelled Janus nanomotor as active probe for detection of pepsinogen by lateral flow immunoassay.

The feasibility of using nanomotors as active probes for lateral flow immunoassay (LFIA) is demonstrated. We synthesized Au@mSiO2@Pt Janus nanomotor, where nanolayer of Pt was deposited on the half side surface of the Au@mSiO2 nanoparticles, which can catalyze the decomposition of H2O2 to produce driving force for the nanomotor. Subsequently, the motion characteristics of the Au@mSiO2@Pt nanomotor in static fluidic environment and dynamic flow field was studied to pave the way for its practical application in lateral flow immunoassay (LFIA). At last, the Au@mSiO2@Pt nanomotor was modified with antibody and then used as active immunoassay probe in LFIA. We chose gastric function index, pepsinogen II (PG II) and pepsinogen II (PG II), as the target analytes. The results indicated that, compared with traditional Au nanoprobe, the nanomotor-based probe can significantly improve the sensitivity by increasing the probability and efficiency of antigen and antibody binding. A limit of detection (LOD) of 2.2 ng/mL for PGI, and 2.1 ng/mL for PG II was achieved. This work provides a new solution for enhancing the capability of immune detection, and we believe the nanomotor-based LFIA will have great potential in high-sensitivity point-of-care-testing in the future.

Application of centrifugal microfluidics in immunoassay, biochemical analysis and molecular diagnosis.

Rapid diagnosis plays a vital role in daily life and is effective in reducing treatment costs and increasing curability, especially in remote areas with limited availability of resources. Among the various common methods of rapid diagnosis, centrifugal microfluidics has many unique advantages, such as less sample consumption, more precise valve control for sequential loading of samples, and accurately separated module design in a microfluidic network to minimize cross-contamination. Therefore, in recent years, centrifugal microfluidics has been extensively researched, and it has been found to play important roles in biology, chemistry, and medicine. Here, we review the latest developments in centrifugal microfluidic platforms in immunoassays, biochemical analyses, and molecular diagnosis, in recent years. In immunoassays, we focus on the application of enzyme-linked immunosorbent assay (ELISA); in biochemical analysis, we introduce the application of plasma and blood cell separation; and in molecular diagnosis, we highlight the application of nucleic acid amplification tests. Additionally, we discuss the characteristics of the methods under each platform as well as the enhancement of the corresponding performance parameters, such as the limit of detection, separation efficiency, etc. Finally, we discuss the limitations associated with the existing applications and potential breakthroughs that can be achieved in this field in the future.

A review on microfluidics in the detection of food pesticide residues.

This paper briefly explains the food safety problems related to pesticide residues and introduces microfluidics technology as a pesticide residue detection method. Three mainstream microfluidic detection devices are detailed: one driven by liquid surface tension, one by motor siphon drive, and one by centrifugal force. The advantages and disadvantages of each are considered in an analysis of future trends in microfluidic technology for pesticide detection.

µ-NMR at the point of care testing.

NMR shows strong analytical capability for obtaining molecular information on materials and is used in a variety of fields. Micro-NMR (µNMR) is mainly based on low-field NMR (LF-NMR), which makes NMR detection portable and inexpensive. Point-of-care testing (POCT) has gradually become an area of major concern, and scientists have made much progress in applying µNMR systems for POCT. To the best of our knowledge, this is the first review of the latest development in miniaturization of µNMR systems. Then, we discuss cutting-edge µNMR-based applications in POCT and the outlook for future developments.

Flexible Antenna Design on PDMS Substrate for Implantable Bioelectronics Applications.

In the current field of biomedical engineering, the research on implanted antennas has attracted more and more attention. This paper presents a flexible terrestrial radiating antenna with circular polarization characteristics that satisfy various requirements for biomedical implantable antennas. The new type of flexible material is adopted and a novel model is proposed. The square ground with small gap is implemented in the proposed antenna. The passive components can match the impedance and meet the requirements of the circular polarization wave. Simulation is carried out in a single layer tissue model to estimate the performance of the antenna and compared with multilayer tissue model. In addition, the flexible circularly polarized antenna has low profile characteristics and a wide axial ratio bandwidth of 250 MHz, ranging from 2.28 GHz to 2.53 GHz. This paper uses pork to simulate single layer and multi layer tissue model. The flexible circular polarized antenna prototype is placed in the organization model for performance simulation test, and the measurement impedance bandwidth of 500 MHz is realized in the industrial scientific medical frequency band of 2.4GHz-2.48 GHz. This article is protected by copyright. All rights reserved.

Multi-modal nanoprobe-enabled biosensing platforms: a critical review.

Nanomaterials show great potential for applications in biosensing due to their unique physical, chemical, and biological properties. However, the single-modal signal sensing mechanism greatly limits the development of single-modal nanoprobes and their related sensors. Multi-modal nanoprobes can realize the output of fluorescence, colorimetric, electrochemical, and magnetic signals through composite nanomaterials, which can effectively compensate for the defects of single-modal nanoprobes. Following the multi-modal nanoprobes, multi-modal biosensors break through the performance limitation of the current single-modal signal and realize multi-modal signal reading. Herein, the current status and classification of multi-modal nanoprobes are provided. Moreover, the multi-modal signal sensing mechanisms and the working principle of multi-modal biosensing platforms are discussed in detail. We also focus on the applications in pharmaceutical detection, food and environmental fields. Finally, we highlight this field's challenges and development prospects to create potential enlightenment.

A Low-cost Creatinine Biosensor by Differential Optical Signal Readout for the Whole Blood Analysis.

This study developed a low-cost paper-based biosensor for point-of-care (POC) detection of blood creatinine by using differential optical signal readout. Dual-channel photochemical paper-based test strips were fabricated with stackable multilayer films containing pre-immobilized enzymes and reagents for the identification and conversion of creatinine and creatine. Enzyme-linked reactions generated hydrogen peroxide (H2O2), which formed a blue oxidized condensate with aniline derivatives. The color depth was quantified via the differential optical signal of the two channels and positively correlated with the concentration of the analyte. This method was first proposed to address the issue of endogenous interferences in the enzymatic assay of creatinine, greatly improving the detection accuracy. The proposed biosensor was calibrated with spiked blood samples, and achieved a wide detection range of 31-1483 µmol/L, showing superior detection performance to general enzymatic methods, especially in the low concentration range. Creatine interference testing demonstrated that the biosensor could resist the interference of ≤ 300 µmol/L endogenous creatine. It is believed that the proposed optical differential biosensor for blood creatinine could enable to pave the way for a daily monitoring system for renal diseases.Clinical Relevance- This stackable multilayer paper-based biosensor provides an enzymatic colorimetric assay of creatinine in whole blood, which can be read out by the differential optical signal to exclude interference from endogenous creatine.

Up-Conversion Luminescence System for Quantitative Detection of IL-6.

Interleukin-6 (IL-6) is a very important cytokine and an early predictor of survival in febrile patients (eg, patients with COVID-19). With the outbreak of the COVID-19 in the world, the significance of medical detection of interleukin 6 has gradually become prominent. A method to point-of-care(POCT) diagnosis and monitoring of IL-6 levels in patients is urgently needed. In this work, an up-conversion luminescence system (ULS) based on upconverting nanoparticles (UCNs) for quantitative detection of IL-6 was designed. The ULS consists of Micro Controller Units (MCU), transmission device, laser, image acquisition module, Bluetooth module, etc. Through hardware system acquisition and image software algorithm processing, we obtain a limit of detection (LOD) of IL-6 at 1 ng/mL, and the quantitative range is from 1 to 200 ng/mL. The system is handheld and has great detection accuracy. The detection time is 10 minutes. In addition, the system can access mobile device terminals (smartphones, personal computers, etc.) or 5G cloud servers via Bluetooth and WIFI. Patients and family members can view medical data through mobile terminals, and the data stored in the 5G cloud server can be used for edge computing and big data analysis. It is suitable for the early diagnosis of infectious diseases such as COVID-19 and has good application prospects.

A smartphone-connected point-of-care photochemical biosensor for the determination of whole blood creatinine by differential optical signal readout.

The level of creatinine in the human body has clinical implications with regard to a potential association with kidney, muscle, and thyroid dysfunction, hence necessitating fast and accurate detection, especially at the point-of-care (POC) level. This paper presents the design, fabrication, and feasibility of a compact, low-cost and reliable POC photochemical biosensor connected to a smartphone for the determination of whole blood creatinine by differential optical signal readout. Disposable, dual-channel paper-based test strips were fabricated using stackable multilayer films pre-immobilized with enzymes and reagents for the identification and conversion of creatinine and creatine, resulting in dramatic colorimetric signals. A handheld optical reader was integrated with dual-channel differential optical readout to address endogenous interferences in the enzymatic assay of creatinine. We demonstrated this differential concept with spiked blood samples, obtaining a wide detection range of 20-1483 µmol/L and a low detection limit of 0.03 µmol/L. Further interference experiments displayed the differential measuring system's excellent performance against endogenous interference. Furthermore, the sensor's high reliability was confirmed through comparison with the laboratory method, with the results of 43 clinical tests consistent with the bulky automatic biochemical analyzer, with its correlation coefficient R2 = 0.9782. Additionally, the designed optical reader is Bluetooth-enabled and can connect to a cloud-based smartphone to transmit test data, enabling active health management or remote monitoring. We believe the biosensor has the potential to be an alternative to the current creatinine analysis conducted in hospitals and clinical laboratories, and it has promising prospects for contributing to the development of POC devices.

Single-molecule immunoassay technology: Recent advances.

Detecting diseases at the molecular level aids in early diagnosis and treatment. However, traditional immunological detection techniques, such as enzyme-linked immunosorbent assay (ELISA) and chemiluminescence, have detection sensitivities between 10-16 and 10-12 mol/L, which are inadequate for early diagnosis. Single-molecule immunoassays can reach detection sensitivities of 10-18 mol/L and can detect biomarkers that are difficult to measure using conventional detection techniques. It can confine molecules to be detected in a small spatial area and provide absolute counting of the detected signal, offering the advantage of high efficiency and accuracy. Herein, we demonstrate the principles and equipment of two single-molecule immunoassay techniques and discuss their applications. It is shown that the detection sensitivity can be improved by 2-3 orders of magnitude compared to common chemiluminescence or ELISA assays. The microarray-based single-molecule immunoassay technique can test 66 samples in 1 h, which is more efficient than conventional immunological detection techniques. In contrast, microdroplet-based single-molecule immunoassay techniques can generate 107 droplets in 10 min, which is more than 100 times faster than a single droplet generator. By comparing the two single-molecule immunoassay techniques, we highlight our personal perspectives on the current limitations of point-of-care applications and future development trends.

Minimally invasive electrochemical continuous glucose monitoring sensors: Recent progress and perspective.

Diabetes and its complications are seriously threatening the health and well-being of hundreds of millions of people. Glucose levels are essential indicators of the health conditions of diabetics. Over the past decade, concerted efforts in various fields have led to significant advances in glucose monitoring technology. In particular, the rapid development of continuous glucose monitoring (CGM) based on electrochemical sensing principles has great potential to overcome the limitations of self-monitoring blood glucose (SMBG) in continuously tracking glucose trends, evaluating diabetes treatment options, and improving the quality of life of diabetics. However, the applications of minimally invasive electrochemical CGM sensors are still limited owing to the following aspects: i) invasiveness, ii) short lifespan, iii) biocompatibility, and iv) calibration and prediction. In recent years, the performance of minimally invasive electrochemical CGM systems (CGMSs) has been significantly improved owing to breakthrough developments in new materials and key technologies. In this review, we summarize the history of commercial CGMSs, the development of sensing principles, and the research progress of minimally invasive electrochemical CGM sensors in reducing the invasiveness of implanted probes, maintaining enzyme activity, and improving the biocompatibility of the sensor interface. In addition, this review also introduces calibration algorithms and prediction algorithms applied to CGMSs and describes the application of machine learning algorithms for glucose prediction.