Coagulation monitoring devices: Past, present, and future at the point of care

Artificial Intelligence in Point-of-Care Biosensing: Challenges and Opportunities

The integration of artificial intelligence (AI) into point-of-care (POC) biosensing has the potential to revolutionize diagnostic methodologies by offering rapid, accurate, and accessible health assessment directly at the patient level. This review paper explores the transformative impact of AI technologies on POC biosensing, emphasizing recent computational advancements, ongoing challenges, and future prospects in the field. We provide an overview of core biosensing technologies and their use at the POC, highlighting ongoing issues and challenges that may be solved with AI. We follow with an overview of AI methodologies that can be applied to biosensing, including machine learning algorithms, neural networks, and data processing frameworks that facilitate real-time analytical decision-making. We explore the applications of AI at each stage of the biosensor development process, highlighting the diverse opportunities beyond simple data analysis procedures. We include a thorough analysis of outstanding challenges in the field of AI-assisted biosensing, focusing on the technical and ethical challenges regarding the widespread adoption of these technologies, such as data security, algorithmic bias, and regulatory compliance. Through this review, we aim to emphasize the role of AI in advancing POC biosensing and inform researchers, clinicians, and policymakers about the potential of these technologies in reshaping global healthcare landscapes.

Electrochemical Monitoring in Anticoagulation Therapy

The process of blood coagulation, wherein circulating blood transforms into a clot in response to an internal or external injury, is a critical physiological mechanism. Monitoring this coagulation process is vital to ensure that blood clotting neither occurs too rapidly nor too slowly. Anticoagulants, a category of medications designed to prevent and treat blood clots, require meticulous monitoring to optimise dosage, enhance clinical outcomes, and minimise adverse effects. This review article delves into the various stages of blood coagulation, explores commonly used anticoagulants and their targets within the coagulation enzyme system, and emphasises the electrochemical methods employed in anticoagulant testing. Electrochemical sensors for anticoagulant monitoring are categorised into two types. The first type focuses on assays measuring thrombin activity via electrochemical techniques. The second type involves modified electrode surfaces that either directly measure the redox behaviours of anticoagulants or monitor the responses of standard redox probes in the presence of these drugs. This review comprehensively lists different electrode compositions and their detection and quantification limits. Additionally, it discusses the potential of employing a universal calibration plot to replace individual drug-specific calibrations. The presented insights are anticipated to significantly contribute to the sensor community's efforts in this field.

Viscoelastic blood coagulation testing system enabled by a non-contact triboelectric angle sensor

Thromboelastography (TEG) remains a convenient and effective viscoelastic blood coagulation testing device for guiding blood component transfusion and assessing the risk of thrombosis. Here, a TEG enabled by a non-contact triboelectric angle sensor (NTAS) with a small size (∼7 cm3) is developed for assessing the blood coagulation system. With the assistance of a superelastic torsion wire structure, the NTAS-TEG realizes the detection of blood viscoelasticity. Benefiting from a grating and convex design, the NTAS holds a collection of compelling features, including accurate detection of rotation angles from -2.5° to 2.5°, high linearity (R 2 = 0.999), and a resolution of 0.01°. Besides, the NTAS exhibits merits of low cost and simplified fabrication. Based on the NTAS-TEG, a viscoelastic blood coagulation detection and analysis system is successfully constructed, which can provide a graph and parameters associated with clot initiation, formation, and stability for clinicians by using 0.36 mL of whole blood. The system not only validates the feasibility of the triboelectric coagulation testing sensor, but also further expands the application of triboelectric sensors in healthcare.

Role of Electrode Configuration and Morphology in Printed Prothrombin Time Sensors

Patients on long-term anticoagulation therapy require frequent testing of prothrombin time/international normalized ratio (PT/INR) to ensure therapeutic efficacy. Point-of-care (POC) PT tests for at-home monitoring eliminate the burden of visiting the clinic, but realizing a cost-effective and robust at-home POC test for PT has remained elusive. Recent demonstrations of printed PT sensors show promise for addressing the cost concerns; however, the printed sensors have lacked quality control to ensure reliability between tests. In this work, on-chip redundancy is introduced with fully printed impedimetric PT sensors by incorporating simultaneous testing with a single fingerstick volume of blood (8 μL). The influence of electrode dimensions and composition were studied, revealing an optimal electrode spacing of 200 μm and an unexpected dependence on the morphology of the electrodes. Three distinct silver morphologies were studied: aerosol jet printed silver nanoparticles (AgNPs), aerosol jet printed silver nanowires (AgNWs), and evaporated silver (Ag). In general, AgNPs exhibited the best PT sensor performance, due to relatively low conductance and high porosity. Overall, the printed impedimetric PT sensor functionalization was improved by incorporating simultaneous testing and, when combined with a handheld control device, shows promise for leading to a system that overcomes the challenges of commercial PT/INR coagulometers.

Polymethyl Methacrylate-Based Smart Microfluidic Point-of-Care Testing of Prothrombin Time and International Normalized Ratio through Optical Detection

The mechanical heart valve is a crucial solution for many patients. However, it cannot function on the state of blood as human tissue valves. Thus, people with mechanical valves are put under anticoagulant therapy. A good measurement of the state of blood and how long it takes blood to form clots is the prothrombin time (PT); moreover, it is an indicator of how well the anticoagulant therapy is, and of whether the response of the patient to the drug is as needed. For a more specific standardized measurement of coagulation time, an international normalized ratio (INR) is established. Clinical testing of INR and PT is relatively easy. However, it requires the patient to visit the clinic for evaluation purposes. Many techniques are therefore being developed to provide PT and INR self-testing devices. Unfortunately, those solutions are either inaccurate, complex, or expensive. The present work approaches the design of an anticoagulation self-monitoring device that is easy to use, accurate, and relatively inexpensive. Hence, a two-channel polymethyl methacrylate-based microfluidic point-of-care (POC) smart device has been developed. The Arduino based lab-on-a-chip device applies optical properties to a small amount of blood. The achieved accuracy is 96.7%.

Micro-mechanical blood clot testing using smartphones

Frequent prothrombin time (PT) and international normalized ratio (INR) testing is critical for millions of people on lifelong anticoagulation with warfarin. Currently, testing is performed in hospital laboratories or with expensive point-of-care devices limiting the ability to test frequently and affordably. We report a proof-of-concept PT/INR testing system that uses the vibration motor and camera on smartphones to track micro-mechanical movements of a copper particle. The smartphone system computed the PT/INR with inter-class correlation coefficients of 0.963 and 0.966, compared to a clinical-grade coagulation analyzer for 140 plasma samples and demonstrated similar results for 80 whole blood samples using a single drop of blood (10 μl). When tested with 79 blood samples with coagulopathic conditions, the smartphone system demonstrated a correlation of 0.974 for both PT/INR. Given the ubiquity of smartphones in the global setting, this proof-of-concept technology may provide affordable and effective PT and INR testing in low-resource environments.

Therapy with anticoagulants requires frequent monitoring. Here the authors describe a proof-of-concept study of a simple and affordable blood clot test that uses a smartphone’s vibration motor and camera to track micro-movements in a single drop of blood.

Simultaneous multiparameter whole blood hemostasis assessment using a carbon nanotube-paper composite capacitance sensor

Rapid and accurate clinical assessment of hemostasis is essential for managing patients who undergo invasive procedures, experience hemorrhages, or receive antithrombotic therapies. Hemostasis encompasses an ensemble of interactions between the cellular and non-cellular blood components, but current devices assess only partial aspects of this complex process. In this work, we describe the development of a new approach to simultaneously evaluate coagulation function, platelet count or function, and hematocrit using a carbon nanotube-paper composite (CPC) capacitance sensor. CPC capacitance response to blood clotting at 1.3 MHz provided three sensing parameters with distinctive sensitivities towards multiple clotting elements. Whole blood-based hemostasis assessments were conducted to demonstrate the potential utility of the developed sensor for various hemostatic conditions, including pathological conditions, such as hemophilia and thrombocytopenia. Results showed good agreements when compared to a conventional thromboelastography. Overall, the presented CPC capacitance sensor is a promising new biomedical device for convenient non-contact whole-blood based comprehensive hemostasis evaluation.

Validation of a Point-of-Care Analyzer for Determining Anticoagulation Status During Air Transport

OBJECTIVE

We evaluated a point-of-care prothrombin time (PT)/international normalized ratio (INR) cartridge-based analyzer for its feasibility, accuracy, and value in critical care air transport.

METHODS

In this prospective study, blood samples from 10 randomly selected adult patients were tested with the cartridge during transport to determine feasibility. The cartridge results were compared with the laboratory results for the same samples. Similarly, blood samples from an additional 20 randomly selected adult patients were tested to determine test accuracy. A chart review identified 110 adult patients with PT/INR cartridge results to determine the clinical value of those results.

RESULTS

Data from the first group of 10 patients showed that vibration did not affect use of the cartridge. The average bias between the 2 testing methods was 0.0 INR units. A comparison of the PT/INR cartridge results and the laboratory results from the group of 20 patients showed that 73% of the cartridge values were within 0.2 of the laboratory values, 83% were within 0.4, and 93% were within 0.6. Of the 110 patients whose charts showed PT/INR cartridge results, 23% received blood products (45 trauma patients and 65 medical patients).

CONCLUSION

The PT/INR cartridge withstands the rigors of rotor wing transport and provides accurate, valuable results for making clinical decisions.

Development of an Optical Method for the Evaluation of Whole Blood Coagulation

Blood coagulation is a defense mechanism, which is activated in case of blood loss, due to vessel damage, or other injury. Pathological cases arise from malfunctions of the blood coagulation mechanism, and rapid growth of clots results in partially or even fully blocked blood vessel. The aim of this work is to characterize blood coagulation, by analyzing the time-dependent structural properties of whole blood, using an inexpensive design and robust processing approaches. The methods used in this work include brightfield microscopy and image processing techniques, applied on finger-prick blood samples. The blood samples were produced and directly utilized in custom-made glass microchannels. Color images were captured via a microscopy-camera setup for a period of 35 min, utilizing three different magnifications. Statistical information was extracted directly from the color components and the binary conversions of the images. The main advantage in the current work lies on a Boolean classification approach utilized on the binary data, which enabled to identify the interchange between specific structural elements of blood, namely the red blood cells, the plasma and the clotted regions, as a result of the clotting process. Coagulation indices produced included a bulk coagulation index, a plasma-reduction based index and a clot formation index. The results produced with the inexpensive design and the low computational complexity in the current approach, show good agreement with the literature, and a great potential for a robust characterization of blood coagulation.

Evaluating a Rapid Field Assessment System for Anticoagulant Rodenticide Exposure of Raptors

Anticoagulant rodenticides (ARs) are commonly used to control rodent pests. However, worldwide, their use is associated with secondary and tertiary poisoning of nontarget species, especially predatory and scavenging birds. No medical device can rapidly test for AR exposure of avian wildlife. Prothrombin time (PT) is a useful biomarker for AR exposure, and multiple commercially available point-of-care (POC) devices measure PT of humans, and domestic and companion mammals. We evaluated the potential of one commercially available POC device, the Coag-Sense^® PT/INR Monitoring System, to rapidly detect AR exposure of living birds of prey. The Coag-Sense device delivered repeatable PT measurements on avian blood samples collected from four species of raptors trapped during migration (Intraclass Correlation Coefficient > 0.9; overall intra-sample variation CV: 5.7%). However, PT measurements reported by the Coag-Sense system from 81 ferruginous hawk (Buteo regalis) nestlings were not correlated to those measured by a one-stage laboratory avian PT assay (r = - 0.017, p = 0.88). Although precise, the lack of agreement in PT estimates from the Coag-Sense device and the laboratory assay indicates that this device is not suitable for detecting potential AR exposure of birds of prey. The lack of suitability may be related to the use of a mammalian reagent in the clotting reaction, suggesting that the device may perform better in testing mammalian wildlife.

Correlation between thromboelastography and rotational thromboelastometry values in adult liver transplant recipients

Background and Aims:

Viscoelastic haemostatic assays (VHA) namely Thromboelastogram (TEG) and Rotational thromboelastometry (ROTEM) are used for global assessment of coagulopathy and guiding transfusion during living donor liver transplant (LDLT).We conducted a study to compare the interchangeability of the values obtained from these devices in patients with End stage liver disease (ESLD) undergoing LDLT.

Methods:

In 76 patients undergoing LDLT, ROTEM and TEG were performed and assessed for interchangeability using Spearman Correlation. The direction and strength of correlation between equivalent parameters was calculated using Inter Class Correlation (ICC) and Bland Altman analysis.

Results:

The correlation ρ between CT (clotting time) of ROTEM and R of TEG was 0.16 (P = 0.19).The ICC was 0.15, with 95% confidence interval (CI) of -0.38-0.48 (P = 0.25).The ρ of CFT (ROTEM) with K (TEG) was 0.425 (P=<0.001). The ICC was0.49 with 95% CI of 0.17-0.69, P = 0.003.Alpha of ROTEM correlated with Angle of TEG with ρ of 0.475 (P=<0.001). The ICC was 0.61, with 95% CI of 0.36-0.76, P=<0.001.Maximum Clot firmness (MCF) correlated with maximum amplitude (MA) with ρ=0.76 (P=<0.001).The ICC was 0.86, with 95% CI of 0.77-0.92, P=<0.001. Lysis index (L30) of ROTEM correlated clot lysis (CL30) of TEG with ρ of 0.16 (P = 0.18).However, the ICC was 0.45, with 95% CI of 0.11-0.66, P = 0.08. The correlation between CT of ROTEM and R of TEG as well as L30 of ROTEM and CL30 of TEG was not significant.The strongest correlation was found between MCF and MA (P < 0.001). However the MCF/MA showed an agreement of only 86% (ICC = 0.86).

Conclusion:

Values from ROTEM and TEG were not found to be interchangeable.

Microfluidics in Haemostasis: A Review

Haemostatic disorders are both complex and costly in relation to both their treatment and subsequent management. As leading causes of mortality worldwide, there is an ever-increasing drive to improve the diagnosis and prevention of haemostatic disorders. The field of microfluidic and Lab on a Chip (LOC) technologies is rapidly advancing and the important role of miniaturised diagnostics is becoming more evident in the healthcare system, with particular importance in near patient testing (NPT) and point of care (POC) settings. Microfluidic technologies present innovative solutions to diagnostic and clinical challenges which have the knock-on effect of improving health care and quality of life. In this review, both advanced microfluidic devices (R&D) and commercially available devices for the diagnosis and monitoring of haemostasis-related disorders and antithrombotic therapies, respectively, are discussed. Innovative design specifications, fabrication techniques, and modes of detection in addition to the materials used in developing micro-channels are reviewed in the context of application to the field of haemostasis.

Point-of-Care Assessment of Hemostasis with a Love-Mode Surface Acoustic Wave Sensor

Monitoring of the hemostasis status is essential for therapeutic anticoagulants, undergoing surgery, cardiovascular diseases, etc. Although the clinical values of conventional blood coagulation tests have been well demonstrated, these devices have limitations such as large and expensive equipment, excessive sample volumes, long turnaround times, and difficulty in miniaturization for point-of-care use. Here, we present a novel strategy to evaluate blood hemostasis using the single-port Love-mode surface acoustic wave (SLSAW) sensor. The SLSAW sensor was designed as a plug-and-play-type unit for disposable use and operated under the harmonic resonant mode to produce frequency response to the blood coagulation cascade. Compared with a quartz crystal microbalance, Lamb wave, and film bulk acoustic resonator, the frequency shift of SLSAW was significantly increased, ranging from approximately 8960 to 10 368 kHz, which indicated enhancement of the signal-to-noise ratio. To demonstrate the feasibility of the SLSAW, studies were carried out to examine the effects of temperature and clotting reagents on coagulation times and kinetics. Activated partial thromboplastin times of plasma were validated by comparing with SYSMEX CA-7000 with the correlation (R²) as 0.996. In terms of coagulation kinetics, reaction time, clot formation time, maximum frequency shift, and clot formation rate of whole blood correlated well with corresponding parameters of the standard thromboelastography (TEG) analyzer (R² = 0.9942, 0.9868, 0.9712, and 0.9939, respectively). The SLSAW sensor, with the advantages of low cost, small size, little sample consumption (1 μL), disposable use, and simple operation, is a promising tool for point-of-care diagnosis of hemostasis.

Temperature Monitorable Kinetics Study of Human Blood Coagulation by Utilizing a Dual-Mode AlN-Based Acoustic Wave Resonator

In this study, we reported an acoustic wave resonator for temperature monitorable kinetic analysis of human blood coagulation. The resonator is operated in both Lamb wave mode at 860 MHz and Rayleigh wave mode at 444 MHz. The electrical parameter variation of the resonator induced by the increased plasma viscosity can be used to monitor the coagulation process. The Lamb mode of the resonator is sensitive to both plasma viscosity and plasma temperature, while the Rayleigh mode responds only to the temperature which is not affected by viscosity. These unique characteristics of the two modes are due to different spatial distributions of the acoustic energy. Taking advantage of the aforementioned features, an acoustic wave resonator to study the human blood coagulation is designed to simultaneously monitor the temperature and plasma viscosity. The coagulation time and plasma temperature were provided by fitting the time-frequency curves. Our design holds great promise for biological reaction monitoring with possible temperature changes.

Technology Advancements in Blood Coagulation Measurements for Point-of-Care Diagnostic Testing

In recent years, blood coagulation monitoring has become crucial to diagnosing causes of hemorrhages, developing anticoagulant drugs, assessing bleeding risk in extensive surgery procedures and dialysis, and investigating the efficacy of hemostatic therapies. In this regard, advanced technologies such as microfluidics, fluorescent microscopy, electrochemical sensing, photoacoustic detection, and micro/nano electromechanical systems (MEMS/NEMS) have been employed to develop highly accurate, robust, and cost-effective point of care (POC) devices. These devices measure electrochemical, optical, and mechanical parameters of clotting blood. Which can be correlated to light transmission/scattering, electrical impedance, and viscoelastic properties. In this regard, this paper discusses the working principles of blood coagulation monitoring, physical and sensing parameters in different technologies. In addition, we discussed the recent progress in developing nanomaterials for blood coagulation detection and treatments which opens up new area of controlling and monitoring of coagulation at the same time in the future. Moreover, commercial products, future trends/challenges in blood coagulation monitoring including novel anticoagulant therapies, multiplexed sensing platforms, and the application of artificial intelligence in diagnosis and monitoring have been included.

Chromatic Properties of Blood During Coagulation

This paper proposes a method of detecting blood clots by analyzing the chromatic properties of blood. Measurements are performed with a Basler camera on blood during coagulation to determine the changes in red, green, and blue (RGB) values. Results show that there is a significant change in the red value that can be exploited for real-time, early detection of blood clots.

Anticoagulant Polyethylene Terephthalate Surface by Plasma-Mediated Fucoidan Immobilization

Biomaterial-based blood clot formation is one of the biggest drawbacks of blood-contacting devices. To avoid blood clot formation, their surface must be tailored to increase hemocompatibility. Most synthetic polymeric biomaterials are inert and lack bonding sites for chemical agents to bond or tailor to the surface. In this study, polyethylene terephthalate was subjected to direct current air plasma treatment to enhance its surface energy and to bring oxidative functional binding sites. Marine-sourced anticoagulant sulphated polysaccharide fucoidan from Fucus vesiculosus was then immobilized onto the treated polyethylene terephthalate (PET) surface at different pH values to optimize chemical bonding behavior and therefore anticoagulant performance. Surface properties of samples were monitored using the water contact angle; chemical analyses were performed by FTIR and X-ray photoelectron spectroscopy (XPS) and their anticoagulant activity was tested by means of prothrombin time, activated partial thromboplastin time and thrombin time. On each of the fucoidan-immobilized surfaces, anticoagulation activity was performed by extending the thrombin time threshold and their pH 5 counterpart performed the best result compared to others.

Viscosity monitoring during hemodiluted blood coagulation using optical coherence elastography

Rapid and accurate clot diagnostic systems are needed for the assessment of hemodiluted blood coagulation. We develop a real-time optical coherence elastography (OCE) system, which measures the attenuation coefficient of a compressional wave induced by a piezoelectric transducer (PZT) in a drop of blood using optical coherence tomography (OCT), for the determination of viscous properties during the dynamic whole blood coagulation process. Changes in the viscous properties increase the attenuation coefficient of the sample. Consequently, dynamic blood coagulation status can be monitored by relating changes of the attenuation coefficient to clinically relevant coagulation metrics, including the initial coagulation time and the clot formation rate. This system was used to characterize the influence of activator kaolin and the influence of hemodilution with either NaCl 0.9% or hydroxyethyl starch (HES) 6% on blood coagulation. The results show that PZT-OCE is sensitive to coagulation abnormalities and is able to characterize blood coagulation status based on viscosity-related attenuation coefficient measurements. PZT-OCE can be used for point-of-care testing for diagnosis of coagulation disorders and monitoring of therapies.

Fibrinogen Motif Discriminates Platelet and Cell Capture in Peptide-Modified Gold Micropore Arrays

Human blood platelets and SK-N-AS neuroblastoma cancer-cell capture at spontaneously adsorbed monolayers of fibrinogen-binding motifs, GRGDS (generic integrin adhesion), HHLGGAKQAGDV (exclusive to platelet integrin α_IIbβ₃), or octanethiol (adhesion inhibitor) at planar gold and ordered 1.6 μm diameter spherical cap gold cavity arrays were compared. In all cases, arginine/glycine/aspartic acid (RGD) promoted capture, whereas alkanethiol monolayers inhibited adhesion. Conversely only platelets adhered to alanine/glycine/aspartic acid (AGD)-modified surfaces, indicating that the AGD motif is recognized preferentially by the platelet-specific integrin, α_IIbβ₃. Microstructuring of the surface effectively eliminated nonspecific platelet/cell adsorption and dramatically enhanced capture compared to RGD/AGD-modified planar surfaces. In all cases, adhesion was reversible. Platelets and cells underwent morphological change on capture, the extent of which depended on the topography of the underlying substrate. This work demonstrates that both the nature of the modified interface and its underlying topography influence the capture of cancer cells and platelets. These insights may be useful in developing cell-based cancer diagnostics as well as in identifying strategies for the disruption of platelet cloaks around circulating tumor cells.

ClotChip: A Microfluidic Dielectric Sensor for Point-of-Care Assessment of Hemostasis

This paper describes the design, fabrication, and testing of a microfluidic sensor for dielectric spectroscopy of human whole blood during coagulation. The sensor, termed ClotChip, employs a three-dimensional, parallel-plate, capacitive sensing structure with a floating electrode integrated into a microfluidic channel. Interfaced with an impedance analyzer, the ClotChip measures the complex relative dielectric permittivity, ϵ_r , of human whole blood in the frequency range of 40 Hz to 100 MHz. The temporal variation in the real part of the blood dielectric permittivity at 1 MHz features a time to reach a permittivity peak, , as well as a maximum change in permittivity after the peak, , as two distinct parameters of ClotChip readout. The ClotChip performance was benchmarked against rotational thromboelastometry (ROTEM) to evaluate the clinical utility of its readout parameters in capturing the clotting dynamics arising from coagulation factors and platelet activity. exhibited a very strong positive correlation ( r = 0.99, p < 0.0001) with the ROTEM clotting time parameter, whereas exhibited a strong positive correlation (r = 0.85,  p < 0.001) with the ROTEM maximum clot firmness parameter. This paper demonstrates the ClotChip potential as a point-of-care platform to assess the complete hemostatic process using <10 μL of human whole blood.

Coagulation measurement from whole blood using vibrating optical fiber in a disposable cartridge

In clinics, blood coagulation time measurements are performed using mechanical measurements with blood plasma. Such measurements are challenging to do in a lab-on-a-chip (LoC) system using a small volume of whole blood. Existing LoC systems use indirect measurement principles employing optical or electrochemical methods. We developed an LoC system using mechanical measurements with a small volume of whole blood without requiring sample preparation. The measurement is performed in a microfluidic channel where two fibers are placed inline with a small gap in between. The first fiber operates near its mechanical resonance using remote magnetic actuation and immersed in the sample. The second fiber is a pick-up fiber acting as an optical sensor. The microfluidic channel is engineered innovatively such that the blood does not block the gap between the vibrating fiber and the pick-up fiber, resulting in high signal-to-noise ratio optical output. The control plasma test results matched well with the plasma manufacturer's datasheet. Activated-partial-thromboplastin-time tests were successfully performed also with human whole blood samples, and the method is proven to be effective. Simplicity of the cartridge design and cost of readily available materials enable a low-cost point-of-care device for blood coagulation measurements.

ZnO Film Bulk Acoustic Resonator for the Kinetics Study of Human Blood Coagulation

Miniaturized and rapid blood coagulation assay technologies are critical in many clinical settings. In this paper, we present a ZnO film bulk acoustic resonator for the kinetic analysis of human blood coagulation. The resonator operated in thickness shear resonance mode at 1.4 GHz. When the resonator contacted the liquid environment, the viscous loading effect was considered as the additional resistance and inductance in the equivalent circuits, resulting in a linear relationship with a slope of approximately −217 kHz/cP between the liquid viscosity and the frequency of the resonator. The downshift of the resonant frequency and the viscosity change during the blood coagulation were correlated to monitor the coagulation process. The sigmoidal trend was observed in the frequency response for the blood samples activated by thromboplastin and calcium ions. The coagulation kinetics involving sequential phases of steady reaction, growth and saturation were revealed through the time-dependent frequency profiles. The enzymatic cascade time, the coagulation rate, the coagulation time and the clot degree were provided by fitting the time-frequency curves. The prothrombin times were compared with the results measured by a standard coagulometer and show a good correlation. Thanks to the excellent potential of integration, miniaturization and the availability of direct digital signals, the film bulk acoustic resonator has promising application for both clinical and personal use coagulation testing technologies.

Micro-electromechanical film bulk acoustic sensor for plasma and whole blood coagulation monitoring

Monitoring blood coagulation is an important issue in the surgeries and the treatment of cardiovascular diseases. In this work, we reported a novel strategy for the blood coagulation monitoring based on a micro-electromechanical film bulk acoustic resonator. The resonator was excited by a lateral electric field and operated under the shear mode with a frequency of 1.9GHz. According to the apparent step-ladder curves of the frequency response to the change of blood viscoelasticity, the coagulation time (prothrombin time) and the coagulation kinetics were measured with the sample consumption of only 1μl. The procoagulant activity of thromboplastin and the anticoagulant effect of heparin on the blood coagulation process were illustrated exemplarily. The measured prothrombin times showed a good linear correlation with R²=0.99969 and a consistency with the coefficient of variation less than 5% compared with the commercial coagulometer. The proposed film bulk acoustic sensor, which has the advantages of small size, light weight, low cost, simple operation and little sample consumption, is a promising device for miniaturized, online and automated analytical system for routine diagnostics of hemostatic status and personal health monitoring.

Point-of-care diagnostics for niche applications

Point-of-care or point-of-use diagnostics are analytical devices that provide clinically relevant information without the need for a core clinical laboratory. In this review we define point-of-care diagnostics as portable versions of assays performed in a traditional clinical chemistry laboratory. This review discusses five areas relevant to human and animal health where increased attention could produce significant impact: veterinary medicine, space travel, sports medicine, emergency medicine, and operating room efficiency. For each of these areas, clinical need, available commercial products, and ongoing research into new devices are highlighted.

The simultaneous occurrence of both hypercoagulability and hypofibrinolysis in blood and serum during systemic inflammation, and the roles of iron and fibrin(ogen)

Although the two phenomena are usually studied separately, we summarise a considerable body of literature to the effect that a great many diseases involve (or are accompanied by) both an increased tendency for blood to clot (hypercoagulability) and the resistance of the clots so formed (hypofibrinolysis) to the typical, 'healthy' or physiological lysis. We concentrate here on the terminal stages of fibrin formation from fibrinogen, as catalysed by thrombin. Hypercoagulability goes hand in hand with inflammation, and is strongly influenced by the fibrinogen concentration (and vice versa); this can be mediated via interleukin-6. Poorly liganded iron is a significant feature of inflammatory diseases, and hypofibrinolysis may change as a result of changes in the structure and morphology of the clot, which may be mimicked in vitro, and may be caused in vivo, by the presence of unliganded iron interacting with fibrin(ogen) during clot formation. Many of these phenomena are probably caused by electrostatic changes in the iron-fibrinogen system, though hydroxyl radical (OH˙) formation can also contribute under both acute and (more especially) chronic conditions. Many substances are known to affect the nature of fibrin polymerised from fibrinogen, such that this might be seen as a kind of bellwether for human or plasma health. Overall, our analysis demonstrates the commonalities underpinning a variety of pathologies as seen in both hypercoagulability and hypofibrinolysis, and offers opportunities for both diagnostics and therapies.

Test of hirudin activity by tracking the binding of hirudin to thrombin in the presence of BS3 cross-linking

Hirudin has a great potential in inhibiting thrombin, and its antithrombin activity has direct bearing on its clinical application. Using bovine alpha-thrombin and recombinant hirudin of Poecilobdella javanica purified from Phichia pastoris as materials, this study introduced a novel method to testing antithrombin activity of hirudin visually and dynamically by tracking the binding of hirudin to thrombin. After incubating the mixture of thrombin and hirudin at 37 °C for 5 min, the binding of hirudin to thrombin was cross-linked by bis[sulfosuccinimidyl] suberate for 30 min and visualized by SDS-polyacrylamide gel electrophoresis. With the aid of image analysis on the basis of INRA-Noésis E1D analysis software, antithrombin activity of hirudin was calculated through intensity variations of protein bands of either thrombin-hirudin compound, unbound thrombin, or unbound hirudin. In this regard, activity of the given hirudin was tested to be 5625 ATU/mg based on a single reaction, and 5675.3 ATU/mg based on a series of reactions in a stepwise manner, close to the result of 6000 ATU/mg concluded by titration method. The superiorities of the method include good accuracy (the minimum testable concentration of hirudin is 1.5 μg/ml) and little sample consumption (sample consumption of hirudin is generally 1-11.5 μl using the apparatus of Mini Protean 3 Cell). Easy operation, low input, and equipment requirement also grant it as an effective way.

A cartridge based sensor array platform for multiple coagulation measurements from plasma

This paper proposes a MEMS-based sensor array enabling multiple clot-time tests for plasma in one disposable microfluidic cartridge. The versatile LoC (Lab-on-Chip) platform technology is demonstrated here for real-time coagulation tests (activated Partial Thromboplastin Time (aPTT) and Prothrombin Time (PT)). The system has a reader unit and a disposable cartridge. The reader has no electrical connections to the cartridge. This enables simple and low-cost cartridge designs and avoids reliability problems associated with electrical connections. The cartridge consists of microfluidic channels and MEMS microcantilevers placed in each channel. The microcantilevers are made of electroplated nickel. They are actuated remotely using an external electro-coil and the read-out is also conducted remotely using a laser. The phase difference between the cantilever oscillation and the coil drive is monitored in real time. During coagulation, the viscosity of the blood plasma increases resulting in a change in the phase read-out. The proposed assay was tested on human and control plasma samples for PT and aPTT measurements. PT and aPTT measurements from control plasma samples are comparable with the manufacturer's datasheet and the commercial reference device. The measurement system has an overall 7.28% and 6.33% CV for PT and aPTT, respectively. For further implementation, the microfluidic channels of the cartridge were functionalized for PT and aPTT tests by drying specific reagents in each channel. Since simultaneous PT and aPTT measurements are needed in order to properly evaluate the coagulation system, one of the most prominent features of the proposed assay is enabling parallel measurement of different coagulation parameters. Additionally, the design of the cartridge and the read-out system as well as the obtained reproducible results with 10 μl of the plasma samples suggest an opportunity for a possible point-of-care application.

Ultra-sensitive detection of heparin via aPTT using plastic antibodies on QCM-D platform

One of the challenges faced by today's clinics is unavailability of practical, precise and accurate determination of the most commonly used anti-coagulant ‘heparin’ in human blood/plasma in surgery.

A sample-to-result system for blood coagulation tests on a microfluidic disk analyzer

In this report, we describe in detail a microfluidic analyzer, which is able to conduct blood coagulation tests using whole blood samples. Sample preparation steps, such as whole blood aliquoting and metering, plasma separation, decanting, and mixing with reagents were performed in sequence through microfluidic functions integrated on a disk. Both prothrombin time (PT) and activated partial thromboplastin time (aPTT) were carried out on the same platform and the test results can be reported in 5 min. Fifty clinical samples were tested for both PT and aPTT utilizing the microfluidic disk analyzer and the instrument used in hospitals. The test results showed good correlation and agreement between the two instruments.