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.

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.

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.

Combination of medical and health care based on digital smartphone-powered photochemical dongle for renal function management.

Currently, the global healthcare market is increasing at high speed with the impendent global aging issue. Healthcare Industry 4.0 has emerged as an efficient solution towards the aging issue since it was integrated with ubiquitous medical sensors, big health processing platform, high bandwidth, speed technologies, and medical services, etc. It is believed to fulfil the requirement of the tremendously growing health market. The acquisition of medical data acts as the dominant precondition to implement the Healthcare Industry 4.0. In the same way, the widely available smartphone could serve as the best biomedical information collect station. In this study, a smartphone-powered photochemical dongle is demonstrated to precisely estimate blood creatinine from the fingertip blood, which works as a highly compact reflectance spectral analyzer with an enzymatically dry chemical test strip. Comparing with conventional laboratory facility for the evaluation and treatment of chronic kidney disease (CKD), it implemented the platform of point care with agreed accuracy. In order to estimate the efficiency of treatment and recovery of the CKD, the proposed photochemical dongle would provide a flexible and rapid platform for point of care. Furthermore, the proposed measured technology is very promising method for remote CKD management.

A miniaturized giant magnetic resistance system for quantitative detection of methamphetamine.

Point-of-care testing (POCT) systems have been greatly developed in recent years. Among them, lateral flow immunoassay (LFIA) based on magnetic nanoparticles (MNPs) is widely used in various fields due to the advantages of small background noise and good biocompatibility. This paper designed an ultra-sensitive giant magnetic resistance (GMR) system for the quantitative detection of methamphetamine (MET). The system uses GMRs to detect the distribution of the magnetic field intensity of MNPs captured by the test (T) and control (C) lines on LFIA. A special external interference cancellation (EIC) method and a weak-signal waveform reconstruction method were used to improve the accuracy of the detection. Finally, the T/C ratio was calculated to realize the quantitative detection of MET. The result showed good linear performance with a detection limit of 0.1 ng mL-1. The system can also be used in other fields such as disease detection, food analysis, and environmental testing.

Quantitative detection of morphine based on an up-conversion luminescent system.

An up-conversion luminescent material converts low-frequency excitation light into high-frequency emission light through photons and has the advantages of long fluorescence lifetime, narrow emission peak and low toxicity; thus, this material has many unique applications in the detection and identification of biomolecules. In this study, an ultrasensitive up-conversion luminescent system for the quantitative detection of morphine was developed. The principle of this system is based on infrared light as an excitation light source to convert light with lower energy into excitation light with higher energy. The up-conversion luminescent material is used as a label and through the processing and analysis of the excitation light intensity, the quantitative detection of morphine concentration is achieved. At the same time, the excitation light can avoid the interference and scattering phenomenon of the autofluorescence of the biological sample, which improves the system's detection sensitivity. An algorithm for light intensity processing is added to process image data, reduce the interference caused by noise during image acquisition and improve the accuracy of morphine detection. The T/C value is calculated to achieve the quantitative detection of morphine with a detection limit of 0.1 ng mg-1 and detection time within 0.5 min. The up-conversion luminescent system has the advantages of quantitative detection, convenience, portability, short detection time and low price. Thus, the system can be used for the detection of other biomolecules or for other applications such as food analysis, environmental detection, national security, etc.

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.

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.

Cytomorphology-based microchip with contour extraction processing for bioparticle analysis.

In this paper, we demonstrated an integrated digital image processing framework that is training-free for high throughput beads or biological cells detection and enumeration by the bead aggregation splitting algorithm. By making contour extraction processing, the aggregated beads can be clearly split for precise counting. It can be potentially embedded on-chip in a miniaturized medical equipment to automatically adjust illumination condition and de-noise. This study demonstrates that the existing hematological analysis can be updated from manual classification and counting by high-speed and precise machine-based programs.

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.

Anti-SARS-CoV-2 IgG and IgM detection with a GMR based LFIA system.

Since December 2019, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has caused millions of deaths and seriously threatened the safety of human life; indeed, this situation is worsening and many people are infected with the new coronavirus every day. Therefore, it is very important to understand patients' degree of infection and infection history through antibody testing. Such information is useful also for the government and hospitals to formulate reasonable prevention policies and treatment plans. In this paper, we develop a lateral flow immunoassay (LFIA) method based on superparamagnetic nanoparticles (SMNPs) and a giant magnetoresistance (GMR) sensing system for the simultaneously quantitative detection of anti-SARS-CoV-2 immunoglobulin M (IgM) and G (IgG). A simple and time-effective co-precipitation method was utilized to prepare the SMNPs, which have good dispersibility and magnetic property, with an average diameter of 68 nm. The Internet of Medical Things-supported GMR could transmit medical data to a smartphone through the Bluetooth protocol, making patient information available for medical staff. The proposed GMR system, based on SMNP-supported LFIA, has an outstanding advantage in cost-effectiveness and time-efficiency, and is easy to operate. We believe that the suggested GMR based LFIA system will be very useful for medical staff to analyze and to preserve as a record of infection in COVID-19 patients.

Increasing straw surface functionalities for enhanced adsorption property.

A simple low-temperature partial-oxidation process was demonstrated as an effective technology for reed straw modification towards environmental remediation. At an optimal temperature of 180 °C, the straw materials exhibited a remarkable colour change from light yellow to dark brown, increased methylene blue (MB) uptake by 1.8 times, enhanced removal efficiency from 34.5% to 92.8%, and a high yield of 77.2%. Spectroscopic characterization and Boehm titration proved that the amount of surface oxygen (O)-containing functional groups significantly increased after modification. A strong linear correlation (R2 = 0.93) existed between total amounts of O-containing functional groups and MB uptake for modification temperatures below 180 °C, whereas blockage of the pore entrances and competition with metallic cations must be taken into account for samples generated from excess heating (>180 °C). These results provided insights into designing promising technologies for sustainable environmental management through reutilization of agricultural waste.

Biomarkers detection with magnetoresistance-based sensors.

Biosensing platforms for detecting and quantifying biomarkers have played an important role in the past decade. Among them, platforms based on magnetoresistance (MR) sensing technology are attractive. The resistance value of the material changes with the externally applied magnetic field is the core mechanism of MR sensing technology. A typical MR-based sensor has the characteristics of cost-effective, simple operation, high compactness, and high sensitivity. Moreover, using magnetic nanoparticles (MNPs) as labels, MR-based sensors have the ability to overcome the high background noise of complex samples, so they are particularly suitable for point-of-care testing (POCT). However, the problem still exists. How to obtain high-throughput, that is, multiple detections of biomarkers in MR-based sensors, thereby improving detection efficiency and reducing the burden on patients is an important issue in future work. This paper reviews three MR-based detection technologies for the detection of biomarkers, i.e., anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), and tunneling magnetoresistance (TMR). Based on these three common technologies, different typical applications that include biomedical diagnosis, food safety, and environmental monitoring are presented. Furthermore, the existing MR-based detection method is better expanded to make it more in line with present detection needs by combining different advanced technologies including microfluidics, Microelectromechanical systems (MEMS), and Immunochromatographic test strips (ICTS). And then, a brief discussion of current challenges and perspectives of MR-based sensors are pointed out.

Palm-Sized Uric Acid Test Lab Powered by Smartphone for Proactive Gout Management.

A simple and convenient photochemical system based on a smartphone-powered photochemical dongle and disposable photochemical test strips was proposed in this paper. The components of the system were only connected with each other in a simple hot-plug way, but provided a convenient function of biological sample detection. The photochemical dongle working as a highly rigorous reflectance spectral analyzer was used to evaluate the uric acid levels of the fingertip whole blood with the participation of the photochemical test strip for the point of care, which showed good agreement (linear regression coefficient of 0.99338) as compared to the results from the specific and bulky biochemical analyzer in the clinical test. Furthermore, combined with the widespread smartphone and well-developed Internet, the photochemical dongle could provide a flexible and portable platform for the evaluation and treatment of chronic diseases, such as gout, and it is promising to be applied in the remote chronic disease management.

Blood Cholesterol Monitoring With Smartphone as Miniaturized Electrochemical Analyzer for Cardiovascular Disease Prevention.

Currently, cardiovascular diseases become one of the major threat to human's life. The early prevention of cardiovascular diseases plays a critical role in the healthcare engineering. Point of care monitoring the blood lipid level is capable of making the positive contribution to the prevention of cardiovascular disease. Ubiquitous smartphones paved the way as the flexible and widespread platform for the interaction of various health information. In this manuscript, we report the world's first medical smartphone as an electrochemical analyzer for blood lipid monitoring. Integrating an electrochemical analyzer into a smartphone allows us to measure the current generated by the enzymatic reaction with the total cholesterol test strip. The disposable test strip is used to convert the biochemical signal to electrical signal through the electrochemical reaction. The proposed medical smartphone can provide accurate evaluation of patient's blood lipid level as compared to the clinical biochemical analyzer. The proposed medical smartphone system is a promising platform as a point-of-care device for blood total cholesterol (TC) monitoring, which can be applied for long-term prevention of cardiovascular disease due to its portability, reliability, lower cost, convenience, and internet-based medical data interaction.