Blood Plasma Coagulation Research Articles

Resonant Acoustic Tweezing Spectroscopy for Small-Volume Noncontact Assessment of Blood Coagulation

Introduction: Measurement and interpretation of mechanical properties of whole blood and blood plasma are important diagnosis and treatment monitoring of various conditions like coagulopathy, hemophilia, sickle cell disease and many cardiovascular disorders. Many of the current techniques like thromboelastography, micro-viscometry or microfluidic devices used for this purpose require a large sample volume and/or may be prone to measurement errors due to sample contact with device walls. To address these issues, we developed a single-drop non-contact method for blood rheological analysis, referred to as “acoustic tweezing rheometry”. With sample volume as small as 4 μL, our innovative technology has been successfully applied for assessment of whole blood and blood plasma coagulation. Here, we present the extension of this technology to resonant spectroscopic measurement of blood viscoelasticity.Materials and Methods: The schematic of the acoustic tweezing device is shown in (Figure 1A). The standing acoustic wave field between the transducer and reflector generates the acoustic radiation force on the biological sample that traps it in a host fluid (e.g., air). Sample tweezing (force-induced deformation and translational motion of the trapped sample) is achieved by amplitude modulation of the acoustic tweezing signal at high frequency and then decrease the frequency continuously until the lower limit for sample trapping is reached. During this frequency sweep, shape changes of the sample were recorded (Figure 1B) by a photodetector and a high-speed camera (Figure 1A). The amplitude-frequency response of the sample was obtained from raw data analysis, with the amplitude being the maximum deflection of the sample height from its equilibrium value. Dynamic (shear) viscosity and elasticity of the sample were assessed from the quality factor of the amplitude-frequency response (Figure 1C) and the resonance frequency, respectively.Results and Discussion: The quality factor analysis predicted that the dynamic viscosity of commercial normal control blood plasma was 1.5 mPa·s at room temperature, which agreed with previous large-sample-volume measurements. Once re-calcified, the resonance frequency of blood plasma and thus its shear elasticity increased due to clot formation until reaching a plateau in 5 min (Figure 1D). Using this graphical output (referred to as “tweezograph”), the following coagulation parameters can be extracted: clot initiation time, clotting rate, clotting time, and maximum clot elasticity.Conclusions: Resonant acoustic tweezing spectroscopy can accurately measure dynamic viscosity and elasticity of whole blood and blood plasma with a small drop of the sample and without artefacts or measurement errors due to sample contact with device walls. This technique can be applied for rapid assessment of whole blood and blood plasma coagulation.Acknowledgments: This study has been supported by U.S. National Science Foundation grant 1438537, American Heart Association Grant-in-Aid 13GRNT17200013, and Tulane University intramural grants. The acoustic tweezing technology is protected by pending patents PCT/US14/55559 and PCT/US2018/014879. [Display omitted] DisclosuresKhismatullin:Levisonics Inc: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties.

Synthetic anionic surfaces can replace microparticles in stimulating burst coagulation of blood plasma.

Biomaterials are frequently evaluated for pro-coagulant activity but usually in the presence of microparticles (MPs), cell-derived vesicles in blood plasma whose phospholipid surfaces allow coagulation factors to set up as functional assemblies. We tested the hypothesis that synthetic anionic surfaces can catalyze burst thrombin activation in human blood plasma in the absence of MPs. In a thromboelastography (TEG) assay with plastic sample cups and pins, recalcified human citrated platelet-poor plasma spontaneously burst-coagulated but with an unpredictable clotting time whereas plasma depleted of MPs by ultracentrifugation failed to coagulate. Coagulation of MP-depleted plasma was restored in a dose-dependent manner by glass microbeads, hydroxyapatite nanoparticles (HA NPs), and carboxylic acid-containing anionic nanocoatings of TEG cups and pins (coated by glow-discharge plasma-polymerized ethylene containing oxygen, L-PPE:O with 4.4 and 6.8 atomic % [COOH]). Glass beads lost their pro-coagulant activity in MP-depleted plasma after their surfaces were nanocoated with hydrophobic plasma-polymerized hexamethyl disiloxane (PP-HMDSO). In FXII-depleted MP-depleted plasma, glass microbeads failed to induce coagulation, however, FXIa was sufficient to induce coagulation in a dose-dependent manner, with no effect of glass beads. These data suggest that anionic surfaces of crystalline, organic, and amorphous solid synthetic materials catalyze explosive thrombin generation in MP-depleted plasma by activating the FXII-dependent intrinsic contact pathway. The data also show that microparticles are pro-coagulant surfaces whose activity has been largely overlooked in many coagulation studies to-date. These results suggest a possible mechanism by which anionic biomaterial surfaces induce bone healing by contact osteogenesis, through fibrin clot formation in the absence of platelet activation.

Coagulation and fibrinolytic potential of blood plasma in patients with stage VD CKD, treated by program hemodialysis, as the markers of thrombotic risk

Thrombotic complications, associated with hemostatic system disturbances in patients with stage VD chronic kidney disease (CKD), occur rather frequently. Hence, the search of early available biological markers in diagnosis of this complication is of great significance. Objective – to study coagulation potential of blood plasma in patients with stage VD CKD, treated by program hemodialysis, and to determine the markers of thrombotic risk. 88 patients (aged 26–65) with stage VD CKD, treated by program hemodialysis, were studied. Hemostatic potential of blood was determined by spectrophotometry; soluble fibrin level — by two-site enzyme-linked immune-sorbent quantitative assay; D-dimer — by enzyme immunoassay using monoclonal antibodies to D-dimer epitopes; protein C activity — by spectrophotometry with wavelength 405 nm; fibrinogen contents — by spectrophotometry with wavelength 280 nm. Statistical processing was performed by methods of variation statistics and correlation analysis. All patients were found to have significant increase of soluble fibrin level (4.03±0.15÷4.62±0.31 mg/ml) (р <0.001), but there was a group of patients (n=25), who demonstrated increased coagulation potential, (р <0.001), significantly prolonged fibrinolysis (р <0.001) and increased soluble fibrin concentration (5.36±0.61÷5.78±0.82 µg/ml) (р <0.001) along with the tendency to decreased C protein level and no response of D-dimer to increased soluble fibrin level. Detected changes in coagulation properties of blood plasma can serve the markers of thrombotic risk. Thus, the patients with stage VD CKD, treated by program hemodialysis, have high risk of thrombosis, associated with high concentration of soluble fibrin and fibrinogen. But in this category of patients, rather low fibrinolytic potential, as well as the level of natural anticoagulant — C protein — is observed. The studied homeostatic parameters can be used as the markers of thrombotic risk.

Frequent, short bouts of light-intensity exercises while standing decreases systolic blood pressure: Breaking Up Sitting Time after Stroke (BUST-Stroke) trial.

Stroke survivors sit for long periods each day. Uninterrupted sitting is associated with increased risk of cardiovascular disease. Breaking up uninterrupted sitting with frequent, short bouts of light-intensity physical activity has an immediate positive effect on blood pressure and plasma clotting factors in healthy, overweight, and type 2 diabetic populations. We examined the effect of frequent, short bouts of light-intensity physical activity on blood pressure and plasma fibrinogen in stroke survivors. Prespecified secondary analyses from a three-armed randomized, within-participant, crossover trial. Participants were 19 stroke survivors (nine female, aged 68 years old, 90% able to walk independently). The experimental conditions were sitting for 8 h uninterrupted, sitting with 3 min bouts of light-intensity exercise while standing every 30 min, or sitting with 3 min of walking every 30 min. Blood pressure was measured every 30 min over 8 h and plasma fibrinogen at the beginning, middle, and end of each day. Intention-to-treat analyses were performed using linear mixed models including fixed effects for condition, period, and order, and a random intercept for participant to account for repeated measures and missing data. Sitting with 3 min bouts of light-intensity exercise while standing every 30 min decreased systolic blood pressure by 3.5 mmHg (95% CI 1.7-5.4) compared with sitting for 8 h uninterrupted. For participants not taking antihypertensive medications, sitting with 3 min of walking every 30 min decreased systolic blood pressure by 5.0 mmHg (95% CI -7.9 to 2.0) and sitting with 3 min bouts light-intensity exercise while standing every 30 min decreased systolic blood pressure by 4.2 mmHg (95% CI -7.2 to -1.3) compared with sitting for 8 h uninterrupted. There was no effect of condition on diastolic blood pressure (p = 0.45) or plasma fibrinogen levels (p = 0.91). Frequent, short bouts of light-intensity physical activity decreases systolic blood pressure in stroke survivors. However, before translation into clinical practice, the optimal duration and timing of physical activity bouts needs to be determined. Australian and New Zealand Clinical Trials Registry http://www.anzctr.org.au ANZTR12615001189516.

Evaluation of Blood Plasma Coagulability by Laser Speckle Correlation

The process of blood plasma coagulation was studied using the laser speckle correlation technique. Coagulation times measured in samples of different volumes using the Minilab 701 commercial coagulometer and the laser speckle correlation technique were compared. It was shown that the laser speckle correlation technique provides comparable accuracy of measurement, while allowing the sample volume to be considerably reduced.

Phenolic fractions from nine Trifolium species modulate the coagulant properties of blood plasma in vitro without cytotoxicity towards blood cells.

The study covers an evaluation of the influence of extracts (1-50 μg/ml), isolated from aerial parts of nine Trifolium L. species (i.e. T. alexandrinum, T. fragiferum, T. hybridum, T. incarnatum, T. pallidum, T. pratense, T. resupinatum var. majus, T. resupinatum var. resupinatum and T. scabrum) on haemostatic properties of blood plasma. The clot formation and fibrinolysis assay (CFF), blood clotting times, the extrinsic and intrinsic coagulation pathway-dependent polymerization of plasma fibrin were measured. The effects of plant extracts on amidolytic activity of thrombin were also evaluated and compared with argatroban, an antithrombotic drug. Cytotoxicity was assessed in a model of blood platelets and as the viability of peripheral blood mononuclear cells. While no changes in blood clotting times or fibrinolytic properties of blood plasma were found, some fractions impaired the blood plasma coagulation induced by the intrinsic coagulation pathway. Reduction in the maximal velocity of fibrin polymerization was also observed in the clot formation and fibrinolysis assay. No cytotoxicity of Trifolium extracts towards the investigated cells was recorded. The most efficient anticoagulant activity in plasma was found for T. fragiferum and T. incarnatum extracts, while the T. alexandrinum fraction was the most effective inhibitor of thrombin amidolytic activity.

Peripheral Blood Plasma Clot as a Local Antimicrobial Drug Delivery Matrix.

Platelet-free blood plasma clots were loaded either with antibiotics (vancomycin, gentamicin, or linezolid) at concentrations of 5-300 μg/mL or with silver ions (silver acetate) at concentrations of 3.3-129 μg/mL. The release of antibiotics or silver from the clot matrix was analyzed after repeated immersion of the plasma clots using reversed-phase high-performance liquid chromatography (RP-HPLC) or atomic absorption spectroscopy (AAS). The antimicrobial activity was tested against Staphylococcus aureus; tissue cell compatibility was analyzed using human mesenchymal stem cells (hMSC). Fibrin fiber thickness of the clots was analyzed by scanning electron microscopy. While addition of linezolid and vancomycin did not significantly change the fibrin fiber thickness, gentamicin and silver ions led to an increase in fiber thickness. All antibiotics showed a concentration-dependent burst-like release from the plasma clots within 1 h followed by a general decay in elution. The release of vancomycin and gentamicin, or silver lasted up to 7 days (depending on initial concentrations), but lasted only up to 4 h for linezolid. A correlation (p < 0.0001) was noted between the concentration of released antibiotics analyzed by HPLC and antimicrobial activity (agar diffusion test). A decrease in antibacterial activity of gentamicin- and vancomycin-containing clots occurred within 4 or 5 days. In contrast, the corresponding antibacterial activity of plasma clots containing linezolid was limited to 3 h. Antibacterial activity of plasma clots containing silver at the highest concentrations decreased after day 3, but clots with lower concentrations induced incomplete bacterial lysis or displayed no antibacterial activity. The antibiotic-containing clots did not induce cytotoxic effects on the embedded hMSC in contrast to all clots containing silver. Our results indicate that an autologous plasma clot can be used to deliver antibiotics such as vancomycin and gentamicin in combination with hMSC and the antibacterial effects persist for days without inducing cytotoxic effects on the embedded stem cells.

Effect of Xylan Sulfates on Coagulation of Human Blood Plasma.

Sulfated derivatives of xylan (isolated from Bétula pubéscens wood) with average molecular weight ~34 kDa, sulfur content of 11.3-17.5%, a degree of substitution of 0.74-1.64 are anticoagulants of direct type of action. Antithrombin and antifactor Xa activities in three tested xylan samples did not differ and reached 30.8-31.8 and 13.5-14.3 U/mg, respectively.

Quasi-static acoustic tweezing for low-volume blood coagulation analysis

Available contact assays for blood plasma and whole blood coagulation have low predictive power in patients with coagulopathy or take a significant amount of time and blood volume to obtain diagnostic data. We have developed an innovative low-volume non-contact technology for real-time assessment of blood coagulation, referred to as “Quasi-static Acoustic Tweezing Thromboelastometry”(QATT). In our method, human blood drops with volume less than 5 microliter (~100 times smaller than the volume required by current coagulation technologies) are levitated in air by acoustic radiation forces. The sample drop location and deformation are induced by a quasi-static change in the acoustic pressure. By extracting a linear regime slope, the samples exhibit a unique elasticity profile over time (tweezograph) less than 20 minutes, characterized by clot initiation time (CIT), time to firm clot formation (TFCF), and maximum clot strength (MCS). The exposure of blood samples to pro- or anti-thrombotic agents (Fibrinogen ...

Biophysical mechanisms of contact activation of blood-plasma clotting

This review considers the biochemical and biophysical mechanisms that trigger blood clotting upon contact of blood with an alien surface and leads via a cascade of enzymatic reactions to fibrin polymerization and the formation of a blood plasma clot, which permeates a primary platelet aggregate to produce a dense hemostatic clot. In spite of the substantial number of experimental and theoretical studies on the subject, there is still no consistent opinion as to what processes occur as the blood plasma contacts a surface. This review discusses the role that plasma protein factor XII and various surfaces play in triggering the contact pathway in vivo and in vitro. Current views of the molecular events that underlie the process are described.

Co-ordinated spatial propagation of blood plasma clotting and fibrinolytic fronts.

Fibrinolysis is a cascade of proteolytic reactions occurring in blood and soft tissues, which functions to disintegrate fibrin clots when they are no more needed. In order to elucidate its regulation in space and time, fibrinolysis was investigated using an in vitro reaction-diffusion experimental model of blood clot formation and dissolution. Clotting was activated by a surface with immobilized tissue factor in a thin layer of recalcified blood plasma supplemented with tissue plasminogen activator (TPA), urokinase plasminogen activator or streptokinase. Formation and dissolution of fibrin clot was monitored by videomicroscopy. Computer systems biology model of clot formation and lysis was developed for data analysis and experimental planning. Fibrin clot front propagated in space from tissue factor, followed by a front of clot dissolution propagating from the same source. Velocity of lysis front propagation linearly depended on the velocity clotting front propagation (correlation r2 = 0.91). Computer model revealed that fibrin formation was indeed the rate-limiting step in the fibrinolysis front propagation. The phenomenon of two fronts which switched the state of blood plasma from liquid to solid and then back to liquid did not depend on the fibrinolysis activator. Interestingly, TPA at high concentrations began to increase lysis onset time and to decrease lysis propagation velocity, presumably due to plasminogen depletion. Spatially non-uniform lysis occurred simultaneously with clot formation and detached the clot from the procoagulant surface. These patterns of spatial fibrinolysis provide insights into its regulation and might explain clinical phenomena associated with thrombolytic therapy.

Blood coagulation evaluation of N-alkylated chitosan

N-Alkylated chitosan (NACS) may improve the haemostatic efficiency of chitosan (CS). To study its coagulation capability and function, a series of NACS with various carbon chain lengths and substitution degrees (SD) of alkyl groups were synthesized and characterized by FTIR, NMR, and elemental analysis. Haemolysis and toxicity assays revealed that NACS showed good biocompatibility. In vitro blood clotting tests indicated that NACS had better haemostatic activity than CS, of which N-octadecyl CS with 3.85% SD showed the best results. Blood plasma coagulation tests showed that NACS was not favourable for activating coagulation factors. Platelet adhesion, intracellular Ca2+, and CD62p measurements demonstrated that the coagulation properties of NACS were not related to platelet activation. Erythrocyte adhesion examination indicated that blood coagulation of NACS may be attributable to its effects on erythrocytes. This study suggests that NACS is an ideal candidate for clotting.

Surface dependent contact activation of factor XII and blood plasma coagulation induced by mixed thiol surfaces.

Studies of the activation of FXII in both platelet poor plasma and in neat buffer solutions were undertaken for a series of mixed thiol self-assembled monolayers spanning a broad range of water wettability. A wide spectrum of carboxyl/methyl-, hydroxyl/methyl-, and amine/methyl-thiol modified surfaces were prepared, characterized, and then utilized as the procoagulant materials in a series of FXII activation studies. X-ray photoelectron spectroscopy was utilized to verify the sample surface's thiol composition and contact angles measured to determine the sample surface's wettability. These samples were then used in in vitro coagulation assays using a 50% mixture of recalcified plasma in phosphate buffered saline. Alternatively, the samples were placed into purified FXII solutions for 30 min to assess FXII activation in neat buffer solution. Plasma coagulation studies supported a strong role for anionic surfaces in contact activation, in line with the traditional models of coagulation, while the activation results in neat buffer solution demonstrated that FXIIa production is related to surface wettability with minimum levels of enzyme activation observed at midrange wettabilities, and no statistically distinguishable differences in FXII activation seen between highly wettable and highly nonwettable surfaces. Results demonstrated that the composition of the solution and the surface properties of the material all contribute to the observation of contact activation, and the activation of FXII is not specific to anionic surfaces as has been long believed.

Abstract 520: Acoustic Tweezing Thromboelastometry

Background: Critical care patients such as trauma and major surgery patients often develop coagulopathy due to depletion of both pro- and anti-coagulants. They are at high risk of both bleeding and thrombotic complications and require monitoring of their coagulation status. The contact of a blood sample with artificial surfaces and its exposure to clot activators, which happen in all commercially available coagulation analyzers, may lead to improper assessment of blood coagulation and thus errors in predicting bleeding/thrombosis risks. Objective: Real-time assessment of whole blood or blood plasma coagulation by novel non-contact acoustic tweezing technology. Method: 4-5 microliter drops of whole blood collected from healthy volunteers or commercial control plasma were levitated in air by acoustic radiation forces. Their coagulation kinetics including reaction time, fibrin network formation time (FNFT), clot formation time and maximum clot strength was assessed from mechanical (drop shape) and photo-optical (light intensity) data. FNFT was determined as a difference between mechanical and photo-optical reaction times. Results: Whole blood samples were exposed to pro- or anti-coagulants during levitation in the acoustic tweezing device. Changes in the coagulation status between different experimental groups were detected within 10 minutes. Similarly, less than 7 minutes was required to detect significant changes in reaction time, clot formation time and maximum clot strength between low, normal, and high fibrinogen level control plasma samples. FNFT was shown to be significantly reduced in plasma samples with a higher level of Factor XIII. Conclusions: The acoustic tweezing technology integrates photo-optical tests used in plasma coagulation assays with viscoelastic tests used in whole blood analysis. Its key disruptive features are the increased reliability and accuracy due to non-contact measurement, small sample volume requirement, relatively short procedure time (&lt;10 minutes), and the ability to assess the level of Factor XIII function from FNFT measurements. Our technology addresses a current lack of reliable methods to measure blood coagulation in patients with coagulopathy.

Activation of the contact pathway of blood coagulation on the circulating microparticles may explain blood plasma coagulation induced by dilution

Recent studies have shown that the contact activation of blood coagulation can be initiated on the surface of circulating microparticles–particles formed as a result of the activation or apoptosis of blood cells or endothelial cells. In the present work, by means of a mathematical model, we investigated the mechanism of the activation of contact pathway of blood plasma coagulation. The model describes membrane-dependent reactions of the activation of factors XII and XI with account of the presence of blood plasma inhibitors. All reactions were described by ordinary differential equations integrated by an implicit multistep method. The current mathematical model is based on our previous model of factor XII activation on the platelet surface. The initial model is modified by the addition of factor XI, kallikrein, and blood plasma inhibitors. We show that the amidolytic activity of the contact pathway factors associated with the microparticles is proportional to the concentration of microparticles. In previous studies, an increase in the overall solution amidolytic activity after the dilution of plasma was observed. Computational analysis of the contact pathway activation in the diluted plasma shows that the increase in the activation appears from the dilution of blood plasma inhibitors. Thus, a well-known experimental phenomenon of the hypercoagulability of plasma after dilution can be explained by an increased activation of the blood plasma coagulation through the contact pathway on the circulating microparticles. In addition, the computational analysis reveals that a rapid stop of the contact pathway activation on the microparticles observed in the experiments could be explained by the rapid depletion of the free activation surface.

Terminalia methanol extracts inhibit the amidolytic activity of human activated factor XII (Hageman factor)

The long‐term goal of this study is to develop the selective inhibitors of FXIIa based on traditional medicine, which might be safe, and effective. There are positive correlations between increased plasma FXIIa levels with coronary heart disease as well as increased risk of recurrent coronary events. Although they maintain a normal hemostasis, FXII knockout mice (FXII−/−) display defective arterial thrombus formation. In addition, FXII−/− mice are protected from development of cerebral ischemia and pulmonary embolism. Thus, inhibition of FXIIa would help prevent cardiovascular diseases. The present study examines the effects of different but related herbal medicines that impact on the plasma blood coagulation FXII. While it initiates the activation of blood coagulation to stop any bleeding, FXII helps the remaining blood clotting factors and platelets to keep certain circulating pathogenic microorganism close to the phagocytes. The negative charge on the microorganism surface or platelet polyphosphate (poly P) binds readily to zymogen FXII, resulting in the activation of FXII. Evidence indicates that poly P containing pathogens promote FXII‐mediated blood coagulation independent of factor XI, reflecting a novel poly P‐induced thrombus formation. The methanol extracts of T. chebula fruit, T. bellirica fruit, T. arjuna fruit, and T. arjuna bark blocked FXIIa activity with IC50 values of 30, 50, 190, 190 and 27 mg/ml, respectively. Two isolated compounds from Terminalia, Arjunoglucoside II and arjunic acid blocked FXIIa activity with IC50 values of 370 and 780 μM, respectively. T. chebula fruit, T. and arjuna fruit extracts at 50 mg/ml did not affect endothelial cells viability. Overall, T. chebula fruit and T. arjuna fruit extracts might be useful to improve symptoms of FXIIa‐dependent inflammation and thrombosis.

The mechanisms and kinetics of initiation of blood coagulation by the extrinsic tenase complex

The system of hemostasis includes coagulation of blood plasma and formation of platelet aggregate. Plasma clotting is a cascade of proteolytic reactions, triggered by the contact of blood plasma with any tissue except the normal vessel endothelium. During the contact an enzymatic complex is formed of the soluble blood plasma protein, factor VIIa, and a membrane-anchored protein, tissue factor. This complex is called extrinsic tenase; it is the key initiator of blood coagulation. The main substrates of extrinsic tenase are blood plasma factors X and IX. During the reaction they undergo proteolytic cleavage and become active serine proteases, factors Xa and IXa, respectively. Factor Xa in complex with its cofactor factor Va catalyzes formation of the key coagulation enzyme, thrombin, which leads to fibrin polymerization and plasma gelation. Although all of the proteins that participate in this process have been known for a long time, several questions remain unanswered. As an example, what is the role of the reaction surface on which the complex is formed, what is the role of membrane-bound multimeres of factor X (Xa), and in what way does the activation of the factor VII proceed? Here, we review recent theoretical and experimental works focused on the biophysical mechanisms of extrinsic tenase functioning and discuss some of these problems.

A Biodegradable Hemostatic Gelatin/Polycaprolactone Composite for Surgical Hemostasis.

Massive bleeding is the leading cause of battlefield-related deaths and the second leading cause of deaths in civilian trauma centers. One of the challenges of managing severe wounds is the need to promote hemostasis as quickly as possible, which can be achieved by using hemostatic dressings. In this study, we fabricated 2 kinds of gelatin/polycaprolactone composites with 2 ratios of gelatin/polycaprolactone, 1:1 and 2:1 (GP11 and GP21, respectively). Scanning electron microscopy revealed that the GP11 composite exhibited rougher and more porous structure than the GP21 composite did. Furthermore, both composites showed similar biocompatibility as that of tissue culture polystyrene. Moreover, both GP composites tended to show a gradual decrease in contact angle to zero within 40 minutes. The in vitro blood plasma coagulation assay revealed that the prothrombin time was significantly longer for the GP composites than it was for the Quikclot composite, whereas the activated partial thromboplastin time of the GP11 composite was significantly shorter than that of the gauze. Furthermore, the GP11 had the largest platelet adsorption of all the composites. The in vivo coagulation test showed an obvious shortening of the bleeding time with the Quikclot and GP21 compared with gauze sample. In conclusion, the GP composites showed superior biocompatibility and hemostasis to the gauze and comparable effects with the Qickclot composite. Therefore, the GP composites have the potential for development as biodegradable surgical hemostatic agents.

Quasi-Static Acoustic Tweezing Thromboelastometry

Acutely unwell patients often develop coagulopathy due to depletion of both pro- and anti-coagulants. They are at high risk of both bleeding and thrombotic complications and require monitoring of their coagulation status. Available contact assays for blood plasma and whole blood coagulation have low predictive power in patients with coagulopathy or take a significant amount of time to obtain diagnostic data. We have developed quasi-static acoustic tweezing thromboelastometry (QATT) as a noncontact method for real-time assessment of blood coagulation. In our method, 4-5 microliter human blood drops are levitated in air by the acoustic radiation force. The sample drop location and deformation are controlled by quasi-statically changing the acoustic pressure. Time-dependent rheological properties of the samples (e.g. sample elasticity) are determined from digital images at each pressure level. Results of our study show that increasing elasticity during coagulation causes blood drops to deform less, leading to steeper deformation/location curves. By extracting a linear regime slope, the samples exhibit a unique slope profile (tweezograph) as they begin to clot. By using tweezographs, we were able to measure the reaction time, coagulation rate and maximum clot stiffness. The exposure of whole blood samples to pro- or anti-coagulants led to significant changes in tweezographs within 10 minutes of sample tweezing, thus allowing detection of hyper- or hypo-coagulable states. Similarly, we detected significant changes between low, normal, and high fibrinogen level control plasma samples, which points out to the ability of our method to measure the fibrinogen level. We demonstrated that QATT can rapidly yield information about coagulation properties of human blood and requires a very small sample volume (∼4 microliter). The advantages of small sample size, non-contact and rapid measurement make this technique desirable for real-time monitoring of blood coagulation in acutely unwell patients.

Effect of construction of TiO2 nanotubes on platelet behaviors: Structure-property relationships.

To realize optimal design and construction of biomaterials with desired properties for blood contact materials, a comprehensive understanding of structure-property relationships is required. In the existing literature, TiO2 nanotube has been reported to be a good candidate for biomedical applications. However, it is noticeable that the blood compatibility of TiO2 nanotubes (TNTs) remains obscure or even inconsistent in the previously published works. The inconsistency could derive from different research protocols, material properties or blood sources. Thus, a thorough investigation of the effect of surface properties on blood compatibility is crucial to the development of titanium based materials. In this paper, we explored the effect of surface properties on the response of platelet-rich plasma, especially surface morphology, chemistry, wettability and crystalline phase. The results indicated that crystalline phase was a dominant factor in platelet behaviors. Reduced adhesion and activation of platelets were observed on amorphous and rutile dominated TNTs, whereas anatase dominated TNTs activated the formation of fibrin network. We further proposed a hypothetical mechanism for better understanding of how surface properties affect the response of platelet-rich plasma. Therefore, this study expands the fundamental understanding of the structure-property relationships of titanium based materials.