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

A surface-functionalized whole blood-based dielectric microsensor for assessment of clot firmness in a fibrinolytic environment

Accurate assessment of fibrin clot stability can predict bleeding risk in coagulopathic conditions such as thrombocytopenia and hypofibrinogenemia. Hyperfibrinolysis - a clinical phenotype characterized by an accelerated breakdown of the fibrin clot - makes such assessments challenging by obfuscating the effect of hemostatic components including platelets or fibrinogen on clot stability. In this work, we present a biofunctionalized, microfluidic, label-free, electronic biosensor to elicit unique, specific, and differential responses from the multifactorial processes of blood coagulation and fibrinolysis ex vivo. The microsensor tracks the temporal variation in the normalized real part of the dielectric permittivity of whole blood (<10 μL) at 1 MHz as the sample coagulates within a three-dimensional, parallel-plate, capacitive sensing area. Surface biofunctionalization of the microsensor's electrodes with physisorption of tissue factor (TF) and aprotinin permits real-time assessment of the coagulation and fibrinolytic outcomes. We show that surface coating with TF and manual addition of TF result in a similar degree of acceleration of coagulation kinetics in human whole blood samples. We also show that surface coating with aprotinin and manual addition of aprotinin yield similar results in inhibiting tissue plasminogen activator (tPA)-induced upregulated fibrinolysis in human whole blood samples. Validated through a clinically relevant, complementary assay - rotational thromboelastometry for clot viscoelasticity - we finally establish that a microsensor dual-coated with both TF and aprotinin detects the hemostatic rescue in the tPA-induced hyperfibrinolytic profile of whole blood and the hemostatic dysfunction due to concurrent platelet depletion in the blood sample, thus featuring enhanced ability in evaluating complex, combinatorial coagulopathies.

CMOS Point-of-Care Diagnostics Technologies: Recent Advances and Future Prospects

This review provides a comprehensive overview of point-of-care (PoC) devices across several key diagnostic applications, including blood analysis, infectious disease detection, neural interfaces, and commercialized integrated circuits (ICs). In the blood analysis section, the focus is on biomarkers such as glucose, dopamine, and aptamers, and their respective detection techniques. The infectious disease section explores PoC technologies for detecting pathogens, RNA, and DNA, highlighting innovations in molecular diagnostics. The neural interface section reviews advancements in neural recording and stimulation for therapeutic applications. Finally, a survey of commercialized ICs from companies such as Abbott and Medtronic is presented, showcasing existing PoC devices already in widespread clinical use. This review emphasizes the role of complementary metal-oxide-semiconductor (CMOS) technology in enabling compact, efficient diagnostic systems and offers insights into the current and future landscape of PoC devices.

Multiplex digital microfluidics using serial controls and its applications in glucose sensing

Digital microfluidics (DMF) has found great applications in vitro diagnostics (IVD). Compared to the microfabrication-based DMF, printed circuit board (PCB)-based DMF is more economical and compatible with existing IVD instruments. Despite that, current PCB-based DMF is oftentimes limited by the available droplets that can be controlled simultaneously, compromising their throughput and applications as point-of-care tools. In this work, a platform that simultaneously controls multiple PCB-based DMF plates was constructed. The software and hardware were first developed, followed by the reliability tests. Colorimetric analysis of glucose was applied to the PCB-based DMF, demonstrating the capability of this platform. With the high throughput enabled by simultaneous operations of multiple plates, this PCB-based DMF can potentially allow point-of-care testing with low cost for resource-limited settings.

Foldable low-cost point-of-care device for testing blood coagulation using smartphones

Cardiovascular diseases (CVDs) caused by thrombotic events are a significant global health concern, affecting millions of people worldwide. The international normalized ratio (INR) is the most widely used measure of coagulation status, and frequent testing is required to adjust blood-thinning drug dosage, requiring hospital visits and experts to perform the test. Here we present a low-cost and portable smartphone-based device for screening INR levels from whole blood samples at the point of care. Our device uses a 3D printed platform and light-emitting diode backlight modules to create a uniform optical environment, and its foldable design allows for easy transport. Our device also features an algorithm that allows users to acquire and process video of sample flow in a microfluidic channel on their smartphone, providing a cost-effective and convenient option for blood coagulation monitoring at the point of care. We tested the performance of our smartphone-based INR device using both commercially available control samples and clinical human blood samples, demonstrating high accuracy and reliability. Our device has the potential to improve patient outcomes by enabling more frequent monitoring and, as appropriate, dosage adjustments of blood-thinning drugs, providing an affordable and portable option for screening INR levels at the point of care.

A Multichannel Portable Platform With Embedded Thermal Management for Miniaturized Dielectric Blood Coagulometry

This article presents a standalone, multichannel, miniaturized impedance analyzer (MIA) system for dielectric blood coagulometry measurements with a microfluidic sensor termed ClotChip. The system incorporates a front-end interface board for 4-channel impedance measurements at an excitation frequency of 1 MHz, an integrated resistive heater formed by a pair of printed-circuit board (PCB) traces to keep the blood sample near a physiologic temperature of 37 °C, a software-defined instrument module for signal generation and data acquisition, and a Raspberry Pi-based embedded computer with 7-inch touchscreen display for signal processing and user interface. When measuring fixed test impedances across all four channels, the MIA system exhibits an excellent agreement with a benchtop impedance analyzer, with rms errors of ≤0.30% over a capacitance range of 47-330 pF and ≤0.35% over a conductance range of 2.13-10 mS. Using in vitro-modified human whole blood samples, the two ClotChip output parameters, namely, the time to reach a permittivity peak (Tpeak) and maximum change in permittivity after the peak (Δϵr,max) are assessed by the MIA system and benchmarked against the corresponding parameters of a rotational thromboelastometry (ROTEM) assay. Tpeak exhibits a very strong positive correlation (r = 0.98, p < 10-6, n = 20) with the ROTEM clotting time (CT) parameter, while Δϵr,max exhibits a very strong positive correlation (r = 0.92, p < 10-6, n = 20) with the ROTEM maximum clot firmness (MCF) parameter. This work shows the potential of the MIA system as a standalone, multichannel, portable platform for comprehensive assessment of hemostasis at the point-of-care/point-of-injury (POC/POI).

Development of Novel Paper-Based Assay for Direct Serum Separation

Background: Many conventional laboratory tests require serum separation using a clot activator/gel tube, followed by centrifugation in an equipped laboratory. The aim of this study is development of novel, equipment-free, paper-based assay for direct and efficient serum separation. Methods: Fresh blood was directly applied to wax-channeled filter paper treated with clotting activator/s and then observed for serum separation. The purity, efficiency, recovery, reproducibility, and applicability of the assay were validated after optimization. Results: Serum was successfully separated using activated partial thromboplastin time (APTT) reagent and calcium chloride-treated wax-channeled filter paper within 2 min. The assay was optimized using different coagulation activators, paper types, blood collection methods, and incubation conditions. Confirmation of serum separation from cellular components was achieved by direct visualization of the yellow serum band, microscopic imaging of the pure serum band, and absence of blood cells in recovered serum samples. Successful clotting was evaluated by the absence of clotting of recovered serum by prolonged prothrombin time and APTT, absence of fibrin degradation products, and absence of Staphylococcus aureus-induced coagulation. Absence of hemolysis was confirmed by undetectable hemoglobin from recovered serum bands. The applicability of serum separated in paper was tested directly by positive color change on paper using bicinchoninic acid protein reagent, on recovered serum samples treated with Biuret and Bradford reagents in tubes, or measurement of thyroid-stimulating hormone and urea compared to standard serum samples. Serum was separated using the paper-based assay from 40 voluntary donors and from the same donor for 15 days to confirm reproducibility. Dryness of coagulants in paper prevents serum separation that can be re-stored by a re-wetting step. Conclusions: Paper-based serum separation allows for development of sample-to-answer paper-based point-of-care tests or simple and direct blood sampling for routine diagnostic tests.

Advances in Microfluidics for Single Red Blood Cell Analysis

The utilizations of microfluidic chips for single RBC (red blood cell) studies have attracted great interests in recent years to filter, trap, analyze, and release single erythrocytes for various applications. Researchers in this field have highlighted the vast potential in developing micro devices for industrial and academia usages, including lab-on-a-chip and organ-on-a-chip systems. This article critically reviews the current state-of-the-art and recent advances of microfluidics for single RBC analyses, including integrated sensors and microfluidic platforms for microscopic/tomographic/spectroscopic single RBC analyses, trapping arrays (including bifurcating channels), dielectrophoretic and agglutination/aggregation studies, as well as clinical implications covering cancer, sepsis, prenatal, and Sickle Cell diseases. Microfluidics based RBC microarrays, sorting/counting and trapping techniques (including acoustic, dielectrophoretic, hydrodynamic, magnetic, and optical techniques) are also reviewed. Lastly, organs on chips, multi-organ chips, and drug discovery involving single RBC are described. The limitations and drawbacks of each technology are addressed and future prospects are discussed.

Point-of-Care Blood Coagulation Assay Based on Dynamic Monitoring of Blood Viscosity Using Droplet Microfluidics

Monitoring of the coagulation function has applications in many clinical settings. Routine coagulation assays in the clinic are sample-consuming and slow in turnaround. Microfluidics provides the opportunity to develop coagulation assays that are applicable in point-of-care settings, but reported works required bulky sample pumping units or costly data acquisition instruments. In this work, we developed a microfluidic coagulation assay with a simple setup and easy operation. The device continuously generated droplets of blood sample and buffer mixture and reported the temporal development of blood viscosity during coagulation based on the color appearance of the resultant droplets. We characterized the relationship between blood viscosity and color appearance of the droplets and performed experiments to validate the assay results. In addition, we developed a prototype analyzer equipped with simple fluid pumping and economical imaging module and obtained similar assay measurements. This assay showed great potential to be developed into a point-of-care coagulation test with practical impact.

Assessment of fibrinolytic status in whole blood using a dielectric coagulometry microsensor

Rapid assessment of the fibrinolytic status in whole blood at the point-of-care/point-of-injury (POC/POI) is clinically important to guide timely management of uncontrolled bleeding in patients suffering from hyperfibrinolysis after a traumatic injury. In this work, we present a three-dimensional, parallel-plate, capacitive sensor - termed ClotChip - that measures the temporal variation in the real part of blood dielectric permittivity at 1 MHz as the sample undergoes coagulation within a microfluidic channel with <10 μL of total volume. The ClotChip sensor features two distinct readout parameters, namely, lysis time (LT) and maximum lysis rate (MLR) that are shown to be sensitive to the fibrinolytic status in whole blood. Specifically, LT identifies the time that it takes from the onset of coagulation for the fibrin clot to mostly dissolve in the blood sample during fibrinolysis, whereas MLR captures the rate of fibrin clot lysis. Our findings are validated through correlative measurements with a rotational thromboelastometry (ROTEM) assay of clot viscoelasticity, qualitative/quantitative assessments of clot stability, and scanning electron microscope imaging of clot ultrastructural changes, all in a tissue plasminogen activator (tPA)-induced fibrinolytic environment. Moreover, we demonstrate the ClotChip sensor ability to detect the hemostatic rescue that occurs when the tPA-induced upregulated fibrinolysis is inhibited by addition of tranexamic acid (TXA) - a potent antifibrinolytic drug. This work demonstrates the potential of ClotChip as a diagnostic platform for rapid POC/POI assessment of fibrinolysis-related hemostatic abnormalities in whole blood to guide therapy.

Combinatorial Polyacrylamide Hydrogels for Preventing Biofouling on Implantable Biosensors

Biofouling on the surface of implanted medical devices and biosensors severely hinders device functionality and drastically shortens device lifetime. Poly(ethylene glycol) and zwitterionic polymers are currently considered "gold-standard" device coatings to reduce biofouling. To discover novel anti-biofouling materials, a combinatorial library of polyacrylamide-based copolymer hydrogels is created, and their ability is screened to prevent fouling from serum and platelet-rich plasma in a high-throughput parallel assay. It is found that certain nonintuitive copolymer compositions exhibit superior anti-biofouling properties over current gold-standard materials, and machine learning is used to identify key molecular features underpinning their performance. For validation, the surfaces of electrochemical biosensors are coated with hydrogels and their anti-biofouling performance in vitro and in vivo in rodent models is evaluated. The copolymer hydrogels preserve device function and enable continuous measurements of a small-molecule drug in vivo better than gold-standard coatings. The novel methodology described enables the discovery of anti-biofouling materials that can extend the lifetime of real-time in vivo sensing devices.

Combinatorial Polyacrylamide Hydrogels for Preventing Biofouling on Implantable Biosensors

Biofouling on the surface of implanted medical devices and biosensors severely hinders device functionality and drastically shortens device lifetime. Poly(ethylene glycol) and zwitterionic polymers are currently considered "gold-standard" device coatings to reduce biofouling. To discover novel anti-biofouling materials, a combinatorial library of polyacrylamide-based copolymer hydrogels is created, and their ability is screened to prevent fouling from serum and platelet-rich plasma in a high-throughput parallel assay. It is found that certain nonintuitive copolymer compositions exhibit superior anti-biofouling properties over current gold-standard materials, and machine learning is used to identify key molecular features underpinning their performance. For validation, the surfaces of electrochemical biosensors are coated with hydrogels and their anti-biofouling performance in vitro and in vivo in rodent models is evaluated. The copolymer hydrogels preserve device function and enable continuous measurements of a small-molecule drug in vivo better than gold-standard coatings. The novel methodology described enables the discovery of anti-biofouling materials that can extend the lifetime of real-time in vivo sensing devices.

Point-of-care blood coagulation assay enabled by printed circuit board-based digital microfluidics

The monitoring of coagulation function has great implications in many clinical settings. However, existing coagulation assays are simplex, sample-consuming, and slow in turnaround, making them less suitable for point-of-care testing. In this work, we developed a novel blood coagulation assay that simultaneously assesses both the tendency of clotting and the stiffness of the resultant clot using printed circuit board (PCB)-based digital microfluidics. A drop of blood was actuated to move back and forth on the PCB electrode array, until the motion winded down as the blood coagulated and became thicker. The velocity tracing and the deformation of the clot were calculated via image analysis to reflect the coagulation progression and the clot stiffness, respectively. We investigated the effect of different hardware and biochemical settings on the assay results. To validate the assay, we performed assays on blood samples with hypo- and hyper-coagulability, and the results confirmed the assay's capability in distinguishing different blood samples. We then examined the correlation between the measured metrics in our assays and standard coagulation assays, namely prothrombin time and fibrinogen level, and the high correlation supported the clinical relevance of our assay. We envision that this method would serve as a powerful point-of-care coagulation testing method.

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.

Point of care whole blood microfluidics for detecting and managing thrombotic and bleeding risks

Point-of-care diagnostics of platelet and coagulation function present demanding challenges. Current clinical diagnostics often use centrifuged plasmas or platelets and frozen plasma standards, recombinant protein standards, or even venoms. Almost all commercialized tests of blood do not recreate the in vivo hemodynamics where platelets accumulate to high densities and thrombin is generated from a procoagulant surface. Despite numerous drugs that target platelets, insufficient coagulation, or excess coagulation, POC blood testing is essentially limited to viscoelastic methods that provide a clotting time, clot strength, and clot lysis, while used mostly in trauma centers with specialized capabilities. Microfluidics now allows small volumes of whole blood (<1 mL) to be tested under venous or arterial shear rates with multi-color readouts to follow platelet function, thrombin generation, fibrin production, and clot stability. Injection molded chips containing pre-patterned fibrillar collagen and lipidated tissue factor can be stored dry for 6 months at 4C, thus allowing rapid blood testing on single-use disposable chips. Using only a small imaging microscope and micropump, these microfluidic devices can detect platelet inhibitors, direct oral anticoagulants (DOACs) and their reversal agents. POC microfluidics are ideal for neonatal surgical applications that involve small blood samples, rapid DOAC testing in stroke or bleeding or emergency surgery situations with patients presenting high risk cofactors for either bleeding or thrombosis.

Blood Flow Velocimetry in a Microchannel During Coagulation Using Particle Image Velocimetry and Wavelet-Based Optical Flow Velocimetry

This article describes novel measurements of the velocity of whole blood flow in a microchannel during coagulation. The blood is imaged volumetrically using a simple optical setup involving a white light source and a microscope camera. The images are processed using particle image velocimetry (PIV) and wavelet-based optical flow velocimetry (wOFV), both of which use images of individual blood cells as flow tracers. Measurements of several clinically relevant parameters such as the clotting time, decay rate, and blockage ratio are computed. The high-resolution wOFV results yield highly detailed information regarding thrombus formation and corresponding flow evolution that is the first of its kind.

Microfluidic electrical impedance assessment of red blood cell-mediated microvascular occlusion

Alterations in the deformability of red blood cells (RBCs), occurring in hemolytic blood disorders such as sickle cell disease (SCD), contribute to vaso-occlusion and disease pathophysiology. There are few functional in vitro assays for standardized assessment of RBC-mediated microvascular occlusion. Here, we present the design, fabrication, and clinical testing of the Microfluidic Impedance Red Cell Assay (MIRCA) with embedded capillary network-based micropillar arrays and integrated electrical impedance measurement electrodes to address this need. The micropillar arrays consist of microcapillaries ranging from 12 μm to 3 μm, with each array paired with two sputtered gold electrodes to measure the impedance change of the array before and after sample perfusion through the microfluidic device. We define RBC occlusion index (ROI) and RBC electrical impedance index (REI), which represent the cumulative percentage occlusion and cumulative percentage impedance change, respectively. We demonstrate the promise of MIRCA in two common red cell disorders, SCD and hereditary spherocytosis. We show that the electrical impedance measurement reflects the microvascular occlusion, where REI significantly correlates with ROI that is obtained via high-resolution microscopy imaging of the microcapillary arrays. Further, we show that RBC-mediated microvascular occlusion, represented by ROI and REI, associates with clinical treatment outcomes and correlates with in vivo hemolytic biomarkers, lactate dehydrogenase (LDH) level and absolute reticulocyte count (ARC) in SCD. Impedance measurement obviates the need for high-resolution imaging, enabling future translation of this technology for widespread access, portable and point-of-care use. Our findings suggest that the presented microfluidic design and the integrated electrical impedance measurement provide a reproducible functional test for standardized assessment of RBC-mediated microvascular occlusion. MIRCA and the newly defined REI may serve as an in vitro therapeutic efficacy benchmark for assessing the clinical outcome of emerging RBC-modifying targeted and curative therapies.

Monitoring DOACs with a Novel Dielectric Microsensor: A Clinical Study

BACKGROUND

 There are acute settings where assessing the anticoagulant effect of direct oral anticoagulants (DOACs) can be useful. Due to variability among routine coagulation tests, there is an unmet need for an assay that detects DOAC effects within minutes in the laboratory or at the point of care.

METHODS

 We developed a novel dielectric microsensor, termed ClotChip, and previously showed that the time to reach peak permittivity (T _peak) is a sensitive parameter of coagulation function. We conducted a prospective, single-center, pilot study to determine its clinical utility at detecting DOAC anticoagulant effects in whole blood.

RESULTS

 We accrued 154 individuals: 50 healthy volunteers, 49 rivaroxaban patients, 47 apixaban, and 8 dabigatran patients. Blood samples underwent ClotChip measurements and plasma coagulation tests. Control mean T _peak was 428 seconds (95% confidence interval [CI]: 401-455 seconds). For rivaroxaban, mean T _peak was 592 seconds (95% CI: 550-634 seconds). A receiver operating characteristic curve showed that the area under the curve (AUC) predicting rivaroxaban using T _peak was 0.83 (95% CI: 0.75-0.91, p < 0.01). For apixaban, mean T _peak was 594 seconds (95% CI: 548-639 seconds); AUC was 0.82 (95% CI: 0.73-0.91, p < 0.01). For dabigatran, mean T _peak was 894 seconds (95% CI: 701-1,086 seconds); AUC was 1 (p < 0.01). Specificity for all DOACs was 88%; sensitivity ranged from 72 to 100%.

CONCLUSION

 This diagnostic study using samples from "real-world" DOAC patients supports that ClotChip exhibits high sensitivity at detecting DOAC anticoagulant effects in a disposable portable platform, using a miniscule amount of whole blood (<10 µL).

Geometry-on-demand fabrication of conductive microstructures by photoetching and application in hemostasis assessment

Photo-corrosion is a common phenomenon observed in the photocatalytic semiconductor materials, which can seriously harm the photoelectric properties and performances in the energy applications. However, in this paper, we demonstrated that the photo-corrosion effects can be used for the microfabrication of conductive structures on a photocatalytic film like zinc oxide (ZnO), named as "photoetching". Our results demonstrated that microstructures can be prepared within seconds with a precision at an order of tens of micrometers using our current devices. Different from the previous work, the etching process was achieved free of conducting layer under the ZnO film, avoiding the short-circuit of the conductive micro-patterns and enabling the use for the impedance sensing. We demonstrated the fabricated ZnO microelectrode pairs can work for the electrochemical impedance measurements like assessment of hemostasis integrated with a microfluidic chip. Compared to the noble metal microelectrodes, the ZnO conductive microelectrodes can be fabricated within seconds and the low costs make it possible as a disposable diagnostic device. Besides, the photoetching technique can be performed without a cleanroom reducing the technical barriers, possibly helpful for the low resources areas. We believe the simplicity of device, low costs and fast fabrication can be useful in the relevant fields such as biomedical and energy harvesting, especially for low resources areas.

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.

A novel, point-of-care, whole-blood assay utilizing dielectric spectroscopy is sensitive to coagulation factor replacement therapy in haemophilia A patients

BACKGROUND

Reliable monitoring of coagulation factor replacement therapy in patients with severe haemophilia, especially those with inhibitors, is an unmet clinical need. While useful, global assays, eg thromboelastography (TEG), rotational thromboelastometry (ROTEM) and thrombin generation assay (TGA), are cumbersome to use and not widely available.

OBJECTIVE

To assess the utility of a novel, point-of-care, dielectric microsensor - ClotChip - to monitor coagulation factor replacement therapy in patients with haemophilia A, with and without inhibitors.

METHODS

The ClotChip T_peak parameter was assessed using whole-blood samples from children with severe haemophilia A, with (n = 6) and without (n = 12) inhibitors, collected pre- and postcoagulation factor replacement therapy. ROTEM, TGA and chromogenic FVIII assays were also performed. Healthy children (n = 50) served as controls.

RESULTS

ClotChip T_peak values exhibited a significant decrease for samples collected postcoagulation factor replacement therapy as compared to baseline (pretherapy) samples in patients with and without inhibitors. A difference in T_peak values was also noted at baseline among severe haemophilia A patients with inhibitors as compared to those without inhibitors. ClotChip T_peak parameter exhibited a very strong correlation with clotting time (CT) of ROTEM, endogenous thrombin potential (ETP) and peak thrombin of TGA, and FVIII clotting activity.

CONCLUSIONS

ClotChip is sensitive to coagulation factor replacement therapy in patients with severe haemophilia A, with and without inhibitors. ClotChip T_peak values correlate very well with ROTEM, TGA and FVIII assays, opening up possibilities for its use in personalized coagulation factor replacement therapy in haemophilia.

Assessment of whole blood coagulation with a microfluidic dielectric sensor

Essentials ClotChip is a novel microsensor for comprehensive assessment of ex vivo hemostasis. Clinical samples show high sensitivity to detecting the entire hemostatic process. ClotChip readout exhibits distinct information on coagulation factor and platelet abnormalities. ClotChip has potential as a point-of-care platform for comprehensive hemostatic analysis.

SUMMARY

Background Rapid point-of-care (POC) assessment of hemostasis is clinically important in patients with a variety of coagulation factor and platelet defects who have bleeding disorders. Objective To evaluate a novel dielectric microsensor, termed ClotChip, which is based on the electrical technique of dielectric spectroscopy for rapid, comprehensive assessment of whole blood coagulation. Methods The ClotChip is a three-dimensional, parallel-plate, capacitive sensor integrated into a single-use microfluidic channel with miniscule sample volume (< 10 μL). The ClotChip readout is defined as the temporal variation in the real part of dielectric permittivity of whole blood at 1 MHz. Results The ClotChip readout exhibits two distinct parameters, namely, the time to reach a permittivity peak (Tpeak ) and the maximum change in permittivity after the peak (Δεr,max ), which are, respectively, sensitive towards detecting non-cellular (i.e. coagulation factor) and cellular (i.e. platelet) abnormalities in the hemostatic process. We evaluated the performance of ClotChip using clinical blood samples from 15 healthy volunteers and 12 patients suffering from coagulation defects. The ClotChip Tpeak parameter exhibited superior sensitivity at distinguishing coagulation disorders as compared with conventional screening coagulation tests. Moreover, the ClotChip Δεr,max parameter detected platelet function inhibition induced by aspirin and exhibited strong positive correlation with light transmission aggregometry. Conclusions This study demonstrates that ClotChip assesses multiple aspects of the hemostatic process in whole blood on a single disposable cartridge, highlighting its potential as a POC platform for rapid, comprehensive hemostatic analysis.

Carbon Nanotube Strain Sensor Based Hemoretractometer for Blood Coagulation Testing

Coagulation monitoring is essential for perioperative care and thrombosis treatment. However, existing assays for coagulation monitoring have limitations such as a large footprint and complex setup. In this work, we developed a miniaturized device for point-of-care blood coagulation testing by measuring dynamic clot retraction force development during blood clotting. In this device, a blood drop was localized between a protrusion and a flexible force-sensing beam to measure clot retraction force. The beam was featured with micropillar arrays to assist the deposition of carbon nanotube films, which served as a strain sensor to achieve label-free electrical readout of clot retraction force in real time. We characterized mechanical and electrical properties of the force-sensing beam and optimized its design. We further demonstrated that this blood coagulation monitoring device could obtain results that were consistent with those using an imaging method and that the device was capable of differentiating blood samples with different coagulation profiles. Owing to its low fabrication cost, small size, and low consumption of blood samples, the blood coagulation testing device using carbon nanotube strain sensors holds great potential as a point-of-care tool for future coagulation monitoring.