The Experts below are selected from a list of 198 Experts worldwide ranked by ideXlab platform
James M. Courtney - One of the best experts on this subject based on the ideXlab platform.
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Blood interface biomaterials
Biomaterials and Devices for the Circulatory System, 2010Co-Authors: X. Zhao, James M. Courtney, H. QianAbstract:Abstract: In this chapter, the Blood Response to the biomaterial is reviewed, focusing on the use of plasticised poly(vinyl chloride) (PVC) as an example for Blood interaction. Hypotheses on designing an ideal Blood-compatible biomaterial are reviewed. Based on these hypotheses, different approaches for modification of biomaterial surfaces to achieve improved Blood compatibility are reviewed. Future trends in developing a Blood compatible biomaterial are discussed.
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Monitoring of the Blood Response in Blood purification
Artificial organs, 2008Co-Authors: James M. Courtney, Sumuk Sundaram, N. M. K. Lamba, Charles D. ForbesAbstract:A principal objective of monitoring the Blood Response in procedures such as hemodialysis and cardiopulmonary bypass is to achieve an enhanced understanding of the relationship between Blood component alterations and the biomaterials employed. The aim in a study of Blood-biomaterial interactions of deriving a correlation between a characteristic of the biomaterial and a representative parameter of the Blood Response can be influenced in a clinical situation by antithrombotic agents, multimaterial contact, device utilization, Blood condition, drug therapy, and the nature of the application. The selection of parameters representative of the Blood Response may require a compromise between the advantages of multiparameter assessment and the benefit of measuring a single parameter by a consistent methodology. Representative parameters are protein adsorption, platelet reactions, intrinsic coagulation and the contact activation phase, fibrinolysis, leukocyte alterations, and complement activation. Assessment during clinical application can be approached by consideration of Blood Response patterns.
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Blood interactions with plasticised poly (vinyl chloride): influence of surface modification
Journal of materials science. Materials in medicine, 2007Co-Authors: Xiaobin Zhao, James M. Courtney, Hua Q. Yin, Robin H. West, Gordon D.o. LoweAbstract:Surface modification of plasticised poly (vinyl chloride) (PVC), with di-(2-ethylhexyl) phthalate (DEHP) as plasticiser, for the improvement of Blood compatibility in potential clinical use such as cardiopulmonary bypass was achieved by heparinisation. The influence of surface modification on Blood compatibility was assessed in terms of the influence on fibrinogen and factor XII adsorption in vitro, and the generation of thrombin-antithrombin III complex (TAT) and the complement component C3a, in vitro and ex vivo. Electron spectroscopy for chemical analysis (ESCA) was used to characterise the heparinised surface in order to correlate the surface properties with the Blood Response. Results indicate that at the plasticised PVC surface there is a higher content of heparin than that of the PVC and the DEHP content is lower than that present at the surface of standard plasticised PVC. The Blood compatibility assessment confirms the importance of surface modification for the improvement of Blood compatibility.
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Modification of plasticised poly (vinyl chloride)
2006Co-Authors: Xiaobin Zhao, James M. CourtneyAbstract:Surface modification of plasticised poly (vinyl chloride) (PVC), with di-(2-ethylhexyl) phthalate (DEHP) as plasticiser, for the improvement of Blood compatibility in potential clinical use such as cardiopulmonary bypass was achieved by heparinisation. The influence of surface modification on Blood compatibility was assessed in terms of the influence on fibrinogen and factor XII adsorption in vitro, and the generation of thrombin-antithrombin III complex (TAT) and the complement component C3a, in vitro and ex vivo. Electron spectroscopy for chemical analysis (ESCA) was used to characterise the heparinised surface in order to correlate the surface properties with the Blood Response. Results indicate that at the plasticised PVC surface there is a higher content of heparin than that of the PVC and the DEHP content is lower than that present at the surface of standard plasticised PVC. The Blood compatibility assessment confirms the importance of surface modification for the improvement of Blood compatibility.
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Blood Response to plasticized poly(vinyl chloride): Dependence of fibrinogen adsorption on plasticizer selection and surface plasticizer level
Journal of Materials Science: Materials in Medicine, 2003Co-Authors: Xiaobin Zhao, James M. CourtneyAbstract:The high level of plasticizer in plasticized poly(vinyl chloride) (PVC) ensures that plasticizer selection has an important influence on the suitability of PVC to function in Blood-contacting applications. In this study, three types of plasticized PVC in sheet form, with di-(2-ethylhexyl)phthalate (DEHP), tri-(2-ethylhexyl)trimellitate (TEHTM) and n-butyryltri-n-hexyl citrate (BTHC) as plasticizer, were selected for assessment and single solute fibrinogen adsorption was utilized as an initial index of interactions with Blood components. Fibrinogen adsorption behavior shows a strong dependence on the plasticizer selection, plasticizer level at the surface and the adsorption conditions, such as adsorption time and fibrinogen solution concentration. Results indicate that BTHC plasticized PVC possesses the lowest adsorption capacity in the three types of plasticized PVC, while TEHTM plasticized PVC seems to have the strongest reactivity in certain fibrinogen solution concentrations. The alteration of surface plasticizer level was achieved by a methanol-cleaning treatment with a variety of cleaning times and the fibrinogen adsorption on plasticized PVC decreases with the reduction of surface plasticizer level. The migration behavior of two phthalate esters (DEHP and TEHTM) was evaluated using UV-Spectrophotometer to determine the plasticizer level at the surfaces. In addition, the fibrinogen adsorption mechanism was examined with Freundlich adsorption modeling.
Gordon D.o. Lowe - One of the best experts on this subject based on the ideXlab platform.
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Blood interactions with plasticised poly (vinyl chloride): influence of surface modification
Journal of materials science. Materials in medicine, 2007Co-Authors: Xiaobin Zhao, James M. Courtney, Hua Q. Yin, Robin H. West, Gordon D.o. LoweAbstract:Surface modification of plasticised poly (vinyl chloride) (PVC), with di-(2-ethylhexyl) phthalate (DEHP) as plasticiser, for the improvement of Blood compatibility in potential clinical use such as cardiopulmonary bypass was achieved by heparinisation. The influence of surface modification on Blood compatibility was assessed in terms of the influence on fibrinogen and factor XII adsorption in vitro, and the generation of thrombin-antithrombin III complex (TAT) and the complement component C3a, in vitro and ex vivo. Electron spectroscopy for chemical analysis (ESCA) was used to characterise the heparinised surface in order to correlate the surface properties with the Blood Response. Results indicate that at the plasticised PVC surface there is a higher content of heparin than that of the PVC and the DEHP content is lower than that present at the surface of standard plasticised PVC. The Blood compatibility assessment confirms the importance of surface modification for the improvement of Blood compatibility.
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In vitro investigation of the Blood Response to medical grade PVC and the effect of heparin on the Blood Response.
Biomaterials, 2000Co-Authors: N. M. K. Lamba, James M. Courtney, John D. S. Gaylor, Gordon D.o. LoweAbstract:This paper reports the results of an investigation into the Blood Response of polymers in vitro, using non-anticoagulated and heparinised Blood and plasma. The materials studied were regenerated cellulose, (Cuprophan), an acrylonitrile-allyl sulphonate copolymer (AN69S), and medical grade polyvinyl chloride plasticised with di-2-ethyl-hexyl-phthalate (PVC/DEHP). Blood-material or plasma-material contact was achieved using a parallel plate flow cell, and C3a generation and FXII-like activity measured. The results of the study with non-anticoagulated human Blood show that PVC/DEHP is a high complement activator. C3a concentration in the Blood was higher after contact with PVC/DEHP than after contact with regenerated cellulose. The introduction of heparin in the Blood induced complex alterations in the Blood Response. C3a generation could be elevated, decreased, or remain the same, depending on the material. The FXII-like activity on the surface of the PVC/DEHP after contact with plasma was also higher than the other two polymers. The introduction of heparin could increase or decrease FXII-like activity, depending on material. The patterns of Response obtained with non-anticoagulated Blood in vitro for AN69S and Cuprophan bore a strong resemblance with patterns of Response obtained in the clinic, whereas those obtained with heparinised Blood in vitro did not.
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Biocompatibility of cardiopulmonary bypass: influence on Blood compatibility of device type, mode of Blood flow and duration of application.
The International journal of artificial organs, 1994Co-Authors: Sumuk Sundaram, James M. Courtney, David P. Taggart, David J. Wheatley, A. C. Tweddel, W. Martin, Gordon D.o. LoweAbstract:The biocompatibility of artificial organs is recognised as an area presenting difficulties in terms of the complexity of the situation. The nature of the Blood Response involving interactions of systems, pattern and extent of change, patient status and the influence of the whole device contribute to the complexity. Recognising these, the profile of the Blood Response to cardiopulmonary bypass (CPB), with respect to type of device, mode of Blood flow, duration of the procedure and patient status, has been evaluated by monitoring contact phase activation [Factor XII-like activity (FXIIA)], fibrinolytic activity [Fibrin degradation products (X-FDP's)], complement activation (C3a, C5a), leucocyte activation [Granulocyte elastase (GE)] and platelet and white cell imaging. FXIIA, X-FDP's, and GE rose gradually during CPB, with levels remaining elevated post-operatively for up to 48 h. In contrast, C3a levels rose sharply with no significant elevation in the post-operative period, while C5a did not show significant changes during bypass. The use of pulsatile perfusion resulted in lesser activation of the parameters, although these were significantly less only for GE. The alterations in FXIIA, X-FDP's, C3a and GE correlated positively with the duration of CPB, with this effect pronounced in the post-operative period for FXIIA, X-FDP's and GE. However, these changes had no apparent influence on clinical outcome and the majority of patients had uncomplicated post-operative recoveries. With respect to the use of bubble/membrane oxygenators, platelet and white cell deposition and the patterns of change for FXIIA and C3a were similar in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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Patterns of Blood Response during cardiopulmonary bypass.
The International journal of artificial organs, 1992Co-Authors: Sumuk Sundaram, James M. Courtney, L. Irvine, David P. Taggart, David J. Wheatley, Gordon D.o. LoweAbstract:Monitoring of cardiopulmonary bypass (CPB) in terms of alterations to the concentrations of selected Blood constituents leads to contrasting patterns of Response. This has been verified by determining the influence of CPB on the activation of fibrinolysis, complement, leucocytes and the contact phase of coagulation. Fibrinolytic activity was determined by fibrin degradation products (X-FDP's), complement activation by C3a and C5a, leucocyte activation by granulocyte elastase and contact activation by factor XII-like activity (FXIIA). Five patients undergoing elective coronary artery surgery using a bubble oxygenator and pulsatile perfusion were studied. X-FDP's rose gradually during CPB and remained elevated. Similar patterns were observed for elastase and FXIIA. In contrast, C3a rose sharply with peak values at 1 1/2-2h of bypass while C5a did not show significant changes during bypass. The data obtained have enabled the establishment of Response patterns for parameters in CPB which will provide information relevant to the clinical application of biomaterials.
G. D. O. Lowe - One of the best experts on this subject based on the ideXlab platform.
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Blood interactions with plasticized poly(vinyl chloride): relevance of plasticizer selection
Journal of Materials Science: Materials in Medicine, 1999Co-Authors: H. Q. Yin, X. B. Zhao, J. M. Courtney, C. R. Blass, R. H. West, G. D. O. LoweAbstract:An investigation has been made of Blood interactions with plasticized poly(vinyl chloride) (PVC) biomaterials in tubular form, taking into account the influence on the Blood Response of the polymer, antithrombotic agent, Blood condition and test procedure. In vitro and ex vivo procedures were used to achieve a comparison between PVC plasticized with di- (2-ethylhexyl)phthalate (DEHP) and with tri-(2-ethylhexyl)trimellitate (TEHTM). The Blood Response was monitored in terms of the measurement of fibrinogen adsorption capacity, thrombin–antithrombin III complex (TAT) and the complement component C3a. Surface characterization of the polymers was performed by X-ray photoelectron spectroscopy (XPS). The data obtained indicate that in comparison with DEHP-PVC, there is a higher reactivity for TEHTM-PVC, which correlates with the plasticizer distribution at the polymer surface. © 1999 Kluwer Academic Publishers
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Complement activation by cellulose: investigation of the effects of time, area, flow rate, shear rate and temperature on C3a generation in vitro, using a parallel plate flow cell.
Journal of materials science. Materials in medicine, 1998Co-Authors: N. M. K. Lamba, James M. Courtney, J.d.s. Gaylor, G. D. O. LoweAbstract:The development and utilization of a parallel plate flow system to study the Blood Response to flat sheet biomaterials, is described. Unlike most other parallel plate flow systems, which have been used to study cellular interactions with biomaterials, the controlled flow test cell described below employs the test materials on both sides of the channel through which the Blood flows. The flow cell is used to conduct an investigation into the in vitro generation of C3a by a regenerated cellulose membrane, Cuprophan. The effects of experimental variables such as temperature, Blood flow rate, contact area and wall shear rate on C3a generation by Cuprophan were studied. The results show that C3a generation by Cuprophan is lower at 12 °C than at 22 °C, which is in turn lower than C3a generation at 37 °C. Furthermore, a decrease in contact area, and increase in wall shear rate and Blood flow rate, can produce a decrease in C3a concentration.
Tetsuji Yamaoka - One of the best experts on this subject based on the ideXlab platform.
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Endothelial cell adhesion and Blood Response to hemocompatible peptide 1 (HCP-1), REDV, and RGD peptide sequences with free N-terminal amino groups immobilized on a biomedical expanded polytetrafluorethylene surface.
Biomaterials science, 2021Co-Authors: Yihua Liu, Atsushi Mahara, Yusuke Kambe, Yu-i Hsu, Tetsuji YamaokaAbstract:Blood compatibility generally requires two contradictory characteristics: reduced protein/platelet adhesion and excellent endothelium-related cell affinity. To understand the effect of cell adhesion peptides on Blood compatibility, the peptides REDV, RGD, and hemocompatible peptide-1 (HCP-1) were immobilized on an expanded polytetrafluorethylene (ePTFE) surface and evaluated in vitro, in situ, and in vivo. Since the terminal amino groups of functional peptides often have an important effect, a cysteine residue was added to the C terminal and used for immobilization to keep the terminal amino groups free. Maleimide groups were added to carboxylic groups of highly hydrophilic and biologically inert (bioinert) polymer chains grafted onto ePTFE and coupled with cysteine residues. In vitro tests revealed that free N-terminal HCP-1 and RGD-immobilized surfaces improved the adhesion and spread of human umbilical vein endothelial cells (HUVECs), while, unexpectedly, a free N-terminal adjacent to REDV suppressed cell affinity. In situ evaluation with a porcine closed-circuit system for 2 h showed that no platelets adhered to the modified ePTFE sutures due to the bioinert graft chain containing phosphorylcholine groups. Simultaneously, leukocyte-related and endothelium-related cells were observed on RGD-immobilized ePTFE sutures because RGD was recognized by broad types of cells. These cells were not observed on the HCP-1- and REDV-immobilized ePTFE sutures, which may be due to insufficient exposure time. HCP-1-modified ePTFE graft implantation in a porcine femorofemoral (FF) bypass model for 10 days showed that the thrombus layer was clearly mitigated by HCP-1 immobilization. This study suggests that the HCP-1-immobilized ePTFE surface has potential for long-term application by mitigating thrombus and supporting endothelial cell adhesion.
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Small-Diameter Synthetic Vascular Graft Immobilized with the REDV Peptide Reduces Early-Stage Fibrin Clot Deposition and Results in Graft Patency in Rats.
Biomacromolecules, 2020Co-Authors: Atsushi Mahara, Yuichi Ohya, Tetsuji YamaokaAbstract:Early-stage hemocompatibility is indispensable for manufacturing tissue-engineered vascular grafts used in regenerative medicine. In this study, we report the in vivo Blood Response and patency of small-diameter synthetic vascular grafts modified with the Arg-Glu-Asp-Val (REDV) peptide. Vascular grafts were prepared by casting REDV-conjugated poly(depsipeptide-co-caprolactone) on a stainless-steel mandril (diameter: 1.8 mm). After implanting the grafts into the abdominal aorta of rats for 24 h, all three control grafts without the peptide and three out of the four REDV (control sequence) peptide-modified grafts showed occlusion. The luminal surfaces of these grafts were covered with thick thrombi. In contrast, all the grafts containing the REDV peptide were patent, and their luminal surfaces were covered with a thin layer of fibrin. These results indicated that the REDV peptide on the luminal surface effectively reduced early-stage fibrin clot deposition and formed the pseudo-endothelium layer in a peptide sequence-specific manner, resulting in graft patency.
Xiaobin Zhao - One of the best experts on this subject based on the ideXlab platform.
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Blood interactions with plasticised poly (vinyl chloride): influence of surface modification
Journal of materials science. Materials in medicine, 2007Co-Authors: Xiaobin Zhao, James M. Courtney, Hua Q. Yin, Robin H. West, Gordon D.o. LoweAbstract:Surface modification of plasticised poly (vinyl chloride) (PVC), with di-(2-ethylhexyl) phthalate (DEHP) as plasticiser, for the improvement of Blood compatibility in potential clinical use such as cardiopulmonary bypass was achieved by heparinisation. The influence of surface modification on Blood compatibility was assessed in terms of the influence on fibrinogen and factor XII adsorption in vitro, and the generation of thrombin-antithrombin III complex (TAT) and the complement component C3a, in vitro and ex vivo. Electron spectroscopy for chemical analysis (ESCA) was used to characterise the heparinised surface in order to correlate the surface properties with the Blood Response. Results indicate that at the plasticised PVC surface there is a higher content of heparin than that of the PVC and the DEHP content is lower than that present at the surface of standard plasticised PVC. The Blood compatibility assessment confirms the importance of surface modification for the improvement of Blood compatibility.
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Modification of plasticised poly (vinyl chloride)
2006Co-Authors: Xiaobin Zhao, James M. CourtneyAbstract:Surface modification of plasticised poly (vinyl chloride) (PVC), with di-(2-ethylhexyl) phthalate (DEHP) as plasticiser, for the improvement of Blood compatibility in potential clinical use such as cardiopulmonary bypass was achieved by heparinisation. The influence of surface modification on Blood compatibility was assessed in terms of the influence on fibrinogen and factor XII adsorption in vitro, and the generation of thrombin-antithrombin III complex (TAT) and the complement component C3a, in vitro and ex vivo. Electron spectroscopy for chemical analysis (ESCA) was used to characterise the heparinised surface in order to correlate the surface properties with the Blood Response. Results indicate that at the plasticised PVC surface there is a higher content of heparin than that of the PVC and the DEHP content is lower than that present at the surface of standard plasticised PVC. The Blood compatibility assessment confirms the importance of surface modification for the improvement of Blood compatibility.
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Blood Response to plasticized poly(vinyl chloride): Dependence of fibrinogen adsorption on plasticizer selection and surface plasticizer level
Journal of Materials Science: Materials in Medicine, 2003Co-Authors: Xiaobin Zhao, James M. CourtneyAbstract:The high level of plasticizer in plasticized poly(vinyl chloride) (PVC) ensures that plasticizer selection has an important influence on the suitability of PVC to function in Blood-contacting applications. In this study, three types of plasticized PVC in sheet form, with di-(2-ethylhexyl)phthalate (DEHP), tri-(2-ethylhexyl)trimellitate (TEHTM) and n-butyryltri-n-hexyl citrate (BTHC) as plasticizer, were selected for assessment and single solute fibrinogen adsorption was utilized as an initial index of interactions with Blood components. Fibrinogen adsorption behavior shows a strong dependence on the plasticizer selection, plasticizer level at the surface and the adsorption conditions, such as adsorption time and fibrinogen solution concentration. Results indicate that BTHC plasticized PVC possesses the lowest adsorption capacity in the three types of plasticized PVC, while TEHTM plasticized PVC seems to have the strongest reactivity in certain fibrinogen solution concentrations. The alteration of surface plasticizer level was achieved by a methanol-cleaning treatment with a variety of cleaning times and the fibrinogen adsorption on plasticized PVC decreases with the reduction of surface plasticizer level. The migration behavior of two phthalate esters (DEHP and TEHTM) was evaluated using UV-Spectrophotometer to determine the plasticizer level at the surfaces. In addition, the fibrinogen adsorption mechanism was examined with Freundlich adsorption modeling.