Electrochemical biosensors for point-of-care testing

Point-of-care testing(POCT)is the practice of diagnosing and monitoring diseases where the patient is located,as opposed to traditional treatment conducted solely in a medical laboratory or other clinical setting.POCT has been less common in the recent past due to a lack of portable medical devices capable of facilitating effective medical testing.However,recent growth has occurred in this field due to advances in diagnostic technologies,device miniaturization,and progress in wearable electronics.Among these developments,electrochemical sensors have attracted interest in the POCT field due to their high sensitivity,compact size,and affordability.They are used in various applications,from disease diagnosis to health status monitoring.In this paper we explore recent advancements in electrochemical sensors,the methods of fabricating them,and the various types of sensing mechanisms that can be used.Furthermore,we delve into methods for immobilizing specific biorecognition elements,including enzymes,antibodies,and aptamers,onto electrode surfaces and how these sensors are used in real-world POCT settings.

Wave-shaped microfluidic chip assisted point-of-care testing for accurate and rapid diagnosis of infections

Background:Early diagnosis and classification of infections increase the cure rate while decreasing complications,which is significant for severe infections,especially for war surgery.However,traditional methods rely on laborious operations and bulky devices.On the other hand,point-of-care(POC)methods suffer from limited robustness and accuracy.Therefore,it is of urgent demand to develop POC devices for rapid and accurate diagnosis of infections to fulfill on-site militarized requirements.Methods:We developed a wave-shaped microfluidic chip(WMC)assisted multiplexed detection platform(WMC-MDP).WMC-MDP reduces detection time and improves repeatability through premixing of the samples and reaction of the reagents.We further combined the detection platform with the streptavidin–biotin(SA-B)amplified system to enhance the sensitivity while using chemiluminescence(CL)intensity as signal readout.We realized simultaneous detection of C-reactive protein(CRP),procalcitonin(PCT),and interleukin-6(IL-6)on the detection platform and evaluated the sensitivity,linear range,selectivity,and repeatability.Finally,we finished detecting 15 samples from volunteers and compared the results with commercial ELISA kits.Results:Detection of CRP,PCT,and IL-6 exhibited good linear relationships between CL intensities and concentrations in the range of 1.25–40μg/ml,0.4–12.8 ng/ml,and 50–1600 pg/ml,respectively.The limit of detection of CRP,PCT,and IL-6 were 0.54μg/ml,0.11 ng/ml,and 16.25 pg/ml,respectively.WMC-MDP is capable of good adequate selectivity and repeatability.The whole detection procedure takes only 22 min that meets the requirements of a POC device.Results of 15 samples from volunteers were consistent with the results detected by commercial ELISA kits.Conclusions:WMC-MDP allows simultaneous,rapid,and sensitive detection of CRP,PCT,and IL-6 with satisfactory selectivity and repeatability,requiring minimal manipulation.However,WMC-MDP takes advantage of being a microfluidic device showing the coefficients of variation less than 10%enabling WMC-MDP to be a type of point-of-care testing(POCT).Therefore,WMC-MDP provides a promising alternative to POCT of multiple biomarkers.We believe the practical application of WMC-MDP in militarized fields will revolutionize infection diagnosis for soldiers.

A smartphone-based automated fluorescence analysis system for point-of-care testing of Hg(Ⅱ)

This work demonstrates a smartphone-based automated fluorescence analysis system(SAFAS)for point-of-care testing(POCT)of Hg(Ⅱ).This system consists of three modules.The smartphone module is used to provide an excitation light source,and to collect and analyze fluorescent images.The dark box module is applied to integrate the desired optical elements and offers a dark environment.The cost of the integrated dark box mainly includes the upper cover,box body,lower bottom,¯xture and some optical elements which is about$109.The chip module is used for fluorescence sensing,which is composed of an upper plate,bottom plate and cloth-based chip.Due to the integration of multiple smartphone functions,the SAFAS eliminates the need for additional power sources,light sources and analysis systems.The dark box and upper and bottom plates are made by 3D printer.The cloth-based chip(about$0.005 for each chip)is fabricated using the wax screenprinting technique,with no need for expensive and complex fabrication equipments.To our knowledge,the cloth-based microfluidic fluorescence detection method combined with smartphone functions is first reported.By using optimal conditions,the designed system can realize the quantitative detection of Hg(Ⅱ),which has a linear range of 0.001–100μgmL^(-1)and a detection limit of 0.5 ngmL^(-1).Additionally,the SAFAS has been successfully applied for detecting Hg(Ⅱ)in actual water samples,with recoveries of 100.1%–111%,RSDs of 3.88%–9.74%,and fast detection time of about 1 min.Obviously,the proposed SAFAS has the advantages of high sensitivity,wide dynamic range,acceptable reproducibility,good stability and low cost.Therefore,it is believed that the presented SAFAS has great potential to perform the POCT of Hg(II)in different water samples.

Point-of-Care Testing vs. Laboratory Testing during High Patient Volume Situations

Introduction: Our aim was to determine what patient volume, if any, in-laboratory testing provides results faster than Point-of-Care-Testing (POCT). Methods: To evaluate POCT effectiveness during high volume situations, POCT was compared to in-laboratory testing during busy periods with large numbers of patients. Our setting was an urban level 1 trauma center with an academic emergency medicine department (ED) and annual patient volume of 70,000. Patients seen requiring laboratory testing during peak volume between 11 a.m. and 7 p.m. were enrolled over a five-week period. One tube of blood was sent to the laboratory and the other tube was run in the ED using POCT. Turnaround time was recorded as time from when the tube was received to when the result was available. We also completed a time-motion study to assess the number of POCT machines that would be needed to process the entire average hourly hospital laboratory volume. Results: We collected 539 hematology and chemistry specimens. The POCT group was significantly faster than in-laboratory testing, with mean POCT [complete blood count (CBC) and chemistry] 3.5 minutes compared to in-laboratory CBC test time of 30.9 minutes and chemistry test time of 55 minutes. As the volume of samples peaked, there was a slight but insignificant decrease in POCT turnaround time. If POCT was used to process the entire average hospital laboratory volume which approached 54 samples an hour, 3 POCT machines would be necessary to maintain turnaround times. Conclusion: Even during ED high volume situations, POCT provided results significantly faster than in-laboratory testing.

Point-of-Care Testing Using Three Dimensional Optical Biosensor Based on Microfluidic Technology

We have presented a three dimensional optical protein chip that fulfills the demanding for point-of-care diagnostics in terms of ease-of-use (one step assay), miniaturization (5 μl). The artful combination of magnetic nanoparticles on chip and total internal reflection imaging (TIRI) technology permits the sensitive and rapid detection of hs-CRP (high-sensitivity C-reactive protein). The whole test was complete within 10 min using “all in one step” assay with a limit of detection of 0.1 ng/mL hs-CRP. The measuring range for hs-CRP could be extended to 10 ng/mL. The chip can also be used to detect more parameters in blood samples.

Recent progress on rapid diagnosis of COVID-19 by point-of-care testing platforms

The outbreak of COVID-19 has drawn great attention around the world.SARS-CoV-2 is a highly infectious virus with occult transmission by many mutations and a long incubation period.In particular,the emergence of asymptomatic infections has made the epidemic even more severe.Therefore,early diagnosis and timely management of suspected cases are essential measures to control the spread of the virus.Developing simple,portable,and accurate diagnostic techniques for SARS-CoV-2 is the key to epidemic prevention.The advantages of point-of-care testing technology make it play an increasingly important role in viral detection and screening.This review summarizes the point-of-care testing platforms developed by nucleic acid detection,immunological detection,and nanomaterial-based biosensors detection.Furthermore,this paper provides a prospect for designing future highly accurate,cheap,and convenient SARS-CoV-2 diagnostic technology.

A Point-of-Care Test System for Biochemical Blood Analysis Based on ADUC824

A point-of-care test system has been studied in this paper.It was used to determine substances in blood such as Hemoglobin (HB),Aspartate Aminotransferase (AST),Creatine Kinase (CK) and so on.Based on the principle of amperometric determination,the research on detecting weak current signals was carried on.At the same time as to the weak signals (nA level),magnifying,sampling and processing the signals were also studied.Controlled by ADUC824 and assisted by other units, every substance could be determined automatically and rapidly integrated with the corresponding biosensor.In the experiment, the minimum detectable current of the instrument (YT2005-1) is 0.2 nA.With regard to the 1 nA which the experiment demanded,it could be up to the mustard.And the system can provide results in 180 s with a long term stability.

Recent Advances and Applications in Paper-Based Devices for Point-of-Care Testing

Point-of-care testing(POCT),as a portable and user-friendly technology,can obtain accurate test results immediately at the sampling point.Nowadays,microfluidic paper-based analysis devices(μPads)have attracted the eye of the public and accelerated the development of POCT.A variety of detection methods are combined withμPads to realize precise,rapid and sensitive POCT.This article mainly introduced the development of electrochemistry and optical detection methods onμPads for POCT and their applications on disease analysis,environmental monitoring and food control in the past 5 years.Finally,the challenges and future development prospects ofμPads for POCT were discussed.

Determination of inhibitory activity of Salvia miltiorrhiza extracts on xanthine oxidase with a paper-based analytical device

A novel paper-based analytical device(PAD)was prepared and applied to determine the xanthine oxidase(XOD)inhibitory activity of Salvia miltiorrhiza extracts(SME).First,polycaprolactone was 3D printed on filter paper and heated to form hydrophobic barriers.Then the modified paper was cut according to the specific design.Necessary reagents including XOD for the colorimetric assay were immobilized on two separate pieces of paper.By simply adding phosphate buffer,the reaction was performed on the double-layer PAD.Quantitative results were obtained by analyzing the color intensity with the specialized device system(consisting of a smartphone,a detection box and sandwich plates).The 3Dprinted detection box was small,with a size of 9.0 cm×7.0 cm×11.5 cm.Color component G performed well in terms of linearity and detection limits and thus was identified as the index.The reaction conditions were optimized using a definitive screening design.Moreover,a 10%glycerol solution was found to be a suitable stabilizer.When the stabilizer was added,the activity of XOD could be maintained for at least 15 days under 4℃ or-20℃ storage conditions.The inhibitory activity of SME was investigated and compared to that of allopurinol.The results obtained with the PAD showed agreement with those obtained with the microplate method.In conclusion,the proposed PAD method is simple,accurate and has a potential for point-of-care testing.It also holds promise for use in rapid quality testing of medicinal herbs,intermediate products,and preparations of traditional Chinese medicines.

Paper-Based Electrochemical Biosensors for Point-of-Care Testing of Neurotransmitters

Abstract Neurotransmitters are important biological molecules related to several nervous system diseases(NSDs).Point-of-care test-ing(POCT)of neurotransmitters is of great importance in preclinical research and early diagnosis of NSDs.Among various POCT platforms,paper-based electrochemical biosensors have achieved great advances in detection of neurotransmitters,thus taking a significant role in POCT of neurotransmitters nowadays.This review gives an overview of the recent advances of paper-based electrochemical biosensors for POCT of neurotransmitters.We first introduce the types of neurotransmitters and biological sample sources mainly used for neurotransmitter detection.Second,we review the components and the traditional fabrication technologies for paper-based electrochemical POCT biosensors,and then the functional modification methods of biosensor surfaces and three-dimensional fabrication methods for further enhancement of their detection performance.Then,we list examples of paper-based electrochemical biosensors used for detecting different neurotransmitters in biologi-cal samples.Last,we give a conclusion and promising development direction of paper-based electrochemical biosensors for neurotransmitters detection.The purpose of this review is to introduce the paper-based electrochemical biosensors as an emerging technology for POCT of neurotransmitters,offering a reference for readers and researchers for early diagnosis of NSDs using POCT technologies.

Point-of-care ultrasound for critically-ill patients: A mini-review of key diagnostic features and protocols

Point-of-care ultrasonography(POCUS)for managing critically ill patients is increasingly performed by intensivists or emergency physicians.Results of needs surveys among intensivists reveal emphasis on basic cardiac,lung and abdominal ultrasound,which are the commonest POCUS modalities in the intensive care unit.We therefore aim to describe the key diagnostic features of basic cardiac,lung and abdominal ultrasound as practised by intensivists or emergency physicians in terms of accuracy(sensitivity,specificity),clinical utility and limitations.We also aim to explore POCUS protocols that integrate basic cardiac,lung and abdominal ultrasound,and highlight areas for future research.

Literature Review of the Use of Zinc and Zinc Compounds in Paper-Based Microfluidic Devices

Zinc and its compounds, alloys and composites play an important role in the modern day world and find application in almost every aspect that can improve the quality of our lives. This ranges from supplements and pharmaceuticals that are meant to improve our health and wellbeing to additives meant to guard or reduce corrosion in metals. However, over the past several years, a new area of technology has been garnering a great deal of attention and has made use of zinc and its compounds. This is with reference to paper-based microfluidic technology that offers several advantages and that keeps expanding in the amount of applications it covers. In this paper, a review is offered for the applications that have used zinc or zinc compounds in paper-based microfluidic devices.

Point-of-care testing for lysine concentration in swine serum via blue-emissive carbon dot-entrapped microfluidic chip

Lysine is one of the essential amino acids and plays a vital role in the growth,development and health of pigs.Blood lysine concentration is a direct indication of lysine status;however,current methods can not satisfy the demands for rapid and on-site lysine concentration measurement of swine serum.Here,we developed blue-emissive nitrogen-doped carbon dots as a fluorescence probe for the determination of lysine with high fluorescence quantum yield,stability,sensitivity and specificity.The carbon dots were entrapped within hydrogel microstructures to fabricate microfluidic chips for rapid assay for lysine quantification.We further developed an imaging attachment to integrate the microfluidic chip and a smartphone into a portable point-of-care testing platform.This platform requires only 3μL sample and has a linear detection range of 25 to 300μmol/L with a limit of detection less than 16μmol/L,which covers the normal range of lysine concentration in swine serum.We tested lysine concentration in swine serum using this platform with high accuracy,low sample consumption,and within 3 min.Together,these results may provide a rapid and portable platform for dynamic monitoring of swine lysine status and contribute to precise feed formula modulation with low-protein diet strategy.

Microalbuminuria sensitive near-infrared AIE probe for point-of-care evaluating kidney diseases

Urinary microalbumin(mALB)serves as an exceptionally sensitive indicator for the early detection of kidney damage,playing a pivotal role in identifying chronic renal failure and kidney lesions in individuals.Nevertheless,the currentfluores-cent methodologies for point-of-care(POC)diagnosis of mALB in real urine still exhibit suboptimal performance.Herein,the development and synthesis of QM-N2,an albumin-activated near-infrared(NIR)aggregation-induced emission(AIE)fluorescent probe,are presented.The strategic incorporation and positioning of quaternary ammonium salts within the quinoline-malononitrile(QM)scaffold sig-nificantly influence solubility and luminescence characteristics.Specifically,the quaternary ammonium salt-free variant,QM-OH,and the quaternary ammonium salt integrated at the donor function group(DFG)site,QM-N1,display limited solubility in aqueous solutions while demonstrating a distinctfluorescence signal.Conversely,the incorporation of quaternary ammonium salt at the conformational functional group(CFG)site in QM-N2 imparts superior dispersibility in water and reduces the initialfluorescence.Furthermore,the integration of a well-defined D-π-A struc-ture within QM-N2 enables itself with near-infrared emission,which is crucial for mitigating interference from autofluorescence present in urine samples.Upon inter-action with albumin,QM-N2 forms a tight bond with the IIA site of the subdomain of human serum albumin(HSA),inducing alterations in protein configuration and constraining the intrinsic motion offluorescent molecules.This interaction inducesfluorescence,facilitating the sensitive detection of trace albumin.Ultimately,QM-N2 is applied for POC testing of mALB using portable equipment,particularly in the diagnosis of mALB-related diseases,notably chronic renal failure.This positioning underscores its potential as an ideal candidate for self-health measurement at home or in community hospitals.

The point-of-care-testing of nucleic acids by chip, cartridge and paper sensors

Point-of-care nucleic acid testing(POCNAT) has played an important role in the outbreak of infectious diseases(e.g., COVID-19) over recent years. POCNAT aims to realize the rapid, simple and automatic detection of nucleic acid. Thanks to the development of manufacturing technology, electronic information technology, artificial intelligence technology, and biological information technology in recent years, the development of the POCNAT device has led to significant advancement. Instead of the normal nucleic acid detection methods used in the laboratory, some novel experimental carriers have been applied, such as chips, cartridges and papers. The application of these experimental carriers has realized the automation and integration of nucleic acid detection. The entire process of nucleic acid detection is normally divided into three steps(nucleic acid extraction, target amplification and signal detection). All of the reagents required by the process can be pre-stored on these experimental carriers, without unnecessary manual operation. Furthermore, all of the processes are carried out in this experimental carrier, with the assistance of a specific control device. Although they are complicated to manufacture and precise in design,their application provides a significant step forwards in nucleic acid detection and realizes the integration of nucleic acid detection. This technology has great potential in the field of point-of-care molecular diagnostics in the future. This paper focuses on the relevant content of these experimental carriers.

Novel screening test for celiac disease using peptide functionalised gold nanoparticles

AIM To develop a screening test for celiac disease based on the coating of gold nanoparticles with a peptide sequence derived from gliadin, the protein that triggers celiac disease.METHODS20 nm gold nanoparticles were first coated with NeutrAvidin. A long chain Polyethylene glycol(PEG) linker containing Maleimide at the Ω-end and Biotin group at the α-end was used to ensure peptide coating to the gold nanoparticles. The maleimide group with the thiol(-SH) side chain reacted with the cysteine amino acid in the peptide sequence and the biotinylated and PEGylated peptide was added to the NeutrAvidin coated gold nanoparticles. The peptide coated gold nanoparticles were then converted into a serological assay. We used the peptide functionalised gold nanoparticle-based assay on thirty patient serum samples in a blinded assessment and compared our results with the previously run serologicaland pathological tests on these patients.RESULTS A stable colloidal suspension of peptide coated gold nanoparticles was obtained without any aggregation. An absorbance peak shift as well as color change was caused by the aggregation of gold nanoparticles following the addition of anti-gliadin antibody to peptide coated nanoparticles at levels associated with celiac disease. The developed assay has been shown to detect anti-gliadin antibody not only in quantitatively spiked samples but also in a small-scale study on real non-hemolytic celiac disease patient's samples.CONCLUSION The study demonstrates the potential of gold nanoparticlepeptide based approach to be adapted for developing a screening assay for celiac disease diagnosis. The assay could be a part of an exclusion based diagnostic strategy and prove particularly useful for testing high celiac disease risk populations.

Scalable Methods for Device Patterning as an Outstanding Challenge in Translating Paper-Based Microfluidics from the Academic Benchtop to the Point-of-Care

Paper-based microfluidic devices offer unparalleled adaptability for the development of low-cost,point-of-care analytical tests.The potential for these devices to drastically improve access to healthcare around the globe is obvious,but very few tests have found success in clinical environments.Here,we identify manufacturing-specifically,methods to pattern paper devices at large scales-as a major barrier to translating prototype paper-based devices from the academic benchtop to the field.We introduce current methods used to pattern papers and discuss their utility as means to prototype and manufacture paper-based devices.

Rapid Absolute Determination Platform of Nucleic Acid for Point-of-care Testing

Nowadays nucleic acid tests are promising to be considered as point-of-care testing（POCT）. However, no such devices are currently available that can perform all the functions, including absolute nucleic acid determination, worldwide on-site detection, rapid analysis and real-time results reporting via ubiquitous mobile networks simultaneously with full package and automated means of measurement. In this study, we presented a compact low-cost portable POC automated testing platform with all attributes mentioned above. A disposable self-priming compartmentalization（SPC） microfluidic chip is used to conduct isothermal amplification. The platform also includes a micro-computer controlled heating unit, an inexpensive optical imaging setup, and a mobile device with customized software. It may become a useful tool for the rapid on-site detection of infectious diseases as well as other pathogens.

RhIr@MoS2 nanohybrids based disposable microsensor for the point-of-care testing of NADH in real human serum

Dihydronicotinamide adenine dinucleotide(NADH)is an important enzyme in all living cells,which is found to be abnormally expressed in cancer cells.Since it is redox-active,an electrochemical detection method would be suitable for monitoring its concentration in biological fluids.Here we present a strategy for specific determination of NADH in real human serum by using RhIr@MoS2 nanohybrids based microsensor.To implement the protocol,RhIr nanocrysrals are in-situ grown onto MoS2 interlayers forming a nanohybrid structure(RhIr@MoS2).After being locally deposited on an electrochemical microsensor,it could be used for the analysis of NADH.The developed RhIr@MoS2 nanohybrids based microsensor possesses the ability for analyzing NADH at the applied potential of 0.07 V(much lower than most reported values).The detection limit is evaluated as low as 1 nmol/L even in bovine serum albumin(BSA)media.In addition,the sampling analysis of human serum from cancer patients and health controls shows that the microsensor displays good diagnostic sensitivity and specificity,illustrating that this developed detection technique is a relatively accurate method for measuring NADH in biological fluids.The proposed electrochemical microsensor assay also owns the benefits of convenience,disposable and easy processing,which make it a great possibility for future point-of-care cancer diagnosis.

Personal glucose meters coupled with signal amplification technologies for quantitative detection of non-glucose targets:Recent progress and challenges in food safety hazards analysis

Ensuring food safety is paramount worldwide.Developing effective detection methods to ensure food safety can be challenging owing to trace hazards,long detection time,and resource-poor sites,in addition to the matrix effects of food.Personal glucose meter(PGM),a classic point-of-care testing device,possesses unique application advantages,demonstrating promise in food safety.Currently,many studies have used PGM-based biosensors and signal amplification technologies to achieve sensitive and specific detection of food hazards.Signal amplification technologies have the potential to greatly improve the analytical performance and integration of PGMs with biosensors,which is crucial for solving the challenges associated with the use of PGMs for food safety analysis.This review introduces the basic detection principle of a PGM-based sensing strategy,which consists of three key factors:target recognition,signal transduction,and signal output.Representative studies of existing PGM-based sensing strategies combined with various signal amplification technologies(nanomaterial-loaded multienzyme labeling,nucleic acid reaction,DNAzyme catalysis,responsive nanomaterial encapsulation,and others)in the field of food safety detection are reviewed.Future perspectives and potential opportunities and challenges associated with PGMs in the field of food safety are discussed.Despite the need for complex sample preparation and the lack of standardization in the field,using PGMs in combination with signal amplification technology shows promise as a rapid and cost-effective method for food safety hazard analysis.