Study on complex formation between recombinant human thrombomodulin fragment and thrombin using surface plasmon resonance

Improvement of blood compatibility on polysulfone-polyvinylpyrrolidone blend films as a model membrane of dialyzer by physical adsorption of recombinant soluble human thrombomodulin (ART-123)

ART-123 is a recombinant soluble human thrombomodulin (hTM) with potent anticoagulant activity, and is available for developing antithrombogenic surfaces by immobilization. We focused on improving blood compatibility on the dialyzer surface by the physical adsorption of ART-123 as a safe yet simple method without using chemical reagents. The physical adsorption mechanism and anticoagulant activities of adsorbed hTM on the surface of a polysulfone (PSF) membrane containing polyvinylpyrrolidone (PVP) as a model dialyzer were investigated in detail. The PVP content of the PSF-PVP films was saturated at 20 wt% after immersion in Tris-HCl buffer, even with the addition of over 20 wt% PVP. The surface morphology of the PSF-PVP films was strongly influenced by the PVP content, because PVP covered the outermost surface of the PSF-PVP films. The adsorption speed of hTM slowed dramatically with increasing PVP content up to 10 wt%, but the maximum adsorption amount of hTM onto the PSF-PVP film surface was almost the same, regardless of the PVP content. The PSF-PVP film with the physically adsorbed hTM showed higher protein C activity as compared to the PSF film, it showed excellent blood compatibility due to the protein C activity and the inhibition properties of platelet adhesion. The physical adsorption of hTM can be useful as a safe yet simple method to improve the blood compatibility of a dialyzer surface.

Inactivation of thrombomodulin by ionizing radiation in a cell-free system: possible implications for radiation responses in vascular endothelium

Normal tissue radiation injury is associated with loss of vascular thromboresistance, notably because of deficient levels of endothelial thrombomodulin (TM). TM is located on the luminal surface of most endothelial cells and has critical anticoagulant and anti-inflammatory functions. Chemical oxidation of a specific methionine residue (Met388) at the thrombin-binding site in TM reduces its main functional activity, i.e., the ability to activate protein C. We examined whether exposure to ionizing radiation affects TM in a similar manner. Full-length recombinant human TM, a construct of epidermal growth factor-like domains 4-6, which are involved in protein C activation, and a synthetic peptide containing the methionine of interest were exposed to gamma radiation in a cell-free system, i.e., a system not confounded by TM turnover or ectodomain shedding. The influence of radiation on functional activity was assessed with the protein C activation assay; formation of a TM-thrombin complex was assessed with surface plasmon resonance (Biacore), and oxidation of Met388 was assessed by HPLC and confirmed by mass spectroscopy. Exposure to radiation caused a dose-dependent reduction in protein C activation, impaired TM-thrombin complex formation, and oxidation of Met388. These results demonstrate that ionizing radiation adversely affects the TM molecule. Our findings may have relevance to normal tissue toxicity in clinical radiation therapy as well as to the development of radiation syndromes in the non-therapeutic radiation exposure setting.

Physical adsorption of human thrombomodulin (ART-123) onto polymeric biomaterials for developing an antithrombogenic blood-contacting material

Human thrombomodulin (hTM) is an endothelial cell-associated protein with potent natural anticoagulant activity by converting thrombin from a procoagulant protease to an anticoagulant. ART-123 is a recombinant soluble hTM (amino acid residues 1-498), and we focused on the physical adsorption of ART-123 onto a polymeric biomaterial surface to develop an antithrombogenic blood-contacting material with preventing the denaturation of hTM and the remaining chemical reagents. The adsorption of hTM onto polysulfone (PSF) films was analyzed quantitatively by quartz crystal microbalance analysis. The adsorption constant and the maximum adsorption amount, calculated by the assumption of a Langmuir-type adsorption, showed that hTM adsorbed with a relatively weak interaction onto the PSF film. The hydrophilic protein lysozyme also showed a Langmuir-type monolayer adsorption, although hydrophobic catalase and fibrinogen showed multilayer adsorption accompanying the denaturation. The physically adsorbed hTM showed high coenzymatic activity for the activation of protein C, as well as anticoagulant activity. Furthermore, the surface wettability of the PSF film was easily controllable by the physical adsorption of hydrophobic and hydrophilic bioactive proteins. The physical adsorption of hTM or bioactive proteins onto polymeric biomaterials will be instrumental for developing an antithrombogenic blood-contacting biomaterial, and for controlling the surface properties of biomaterials.

Survey of the year 2000 commercial optical biosensor literature

We have compiled a comprehensive list of the articles published in the year 2000 that describe work employing commercial optical biosensors. Selected reviews of interest for the general biosensor user are highlighted. Emerging applications in areas of drug discovery, clinical support, food and environment monitoring, and cell membrane biology are emphasized. In addition, the experimental design and data processing steps necessary to achieve high-quality biosensor data are described and examples of well-performed kinetic analysis are provided.