PubMed Health⌕ Search

Biomedical subjects

Wansik Cha

Publications and source records attributed to Wansik Cha.

4 recordsLinked to original sources
PubMed2006

S-nitrosothiol detection via amperometric nitric oxide sensor with surface modified hydrogel layer containing immobilized organoselenium catalyst.

A novel electrochemical device for the direct detection of S-nitrosothiol species (RSNO) is proposed by modifying an amperometric nitric oxide (NO) gas sensor with thin hydrogel layer containing an immobilized organoselenium catalyst. The diselenide, 3,3'-dipropionicdiselenide, is covalently coupled to primary amine groups in polyethylenimine (PEI), which is further cross-linked to form a hydrogel layer on a dialysis membrane support. Such a polymer film containing the organoselenium moiety is capable of decomposing S-nitrosothiols to generate NO(g) at the distal tip of the NO sensor. Under optimized conditions, various RSNOs (e.g., nitrosocysteine (CysNO), nitrosoglutathione (GSNO), etc.) are reversibly detected at </=0.1 microM levels, with sensor lifetimes of at least 10 days. The presence of reducing agents (e.g., glutathione) added to the test solution enhances the amperometric dynamic range output to approximately 25 microM levels of RSNO species. Sensitivities observed for different small molecule RSNO species are nearly equivalent, in sharp contrast to the behavior observed previously for a similar RSNO sensing configuration based on an immobilized Cu(I/II) catalytic layer. It is further shown that the new RSNO sensors can be used to assess the "NO-generating" ability of fresh blood samples by effectively detecting the total level of reactive low molecular-weight RSNO species present in such samples.

Animals↗
PubMed2006

Catalytic generation of nitric oxide from S-nitrosothiols using immobilized organoselenium species.

Novel nitric oxide (NO) generating polymeric materials possessing immobilized organoselenium species are described. These materials mimic the capability of small organoselenium molecules as well as a known selenium-containing enzyme, glutathione peroxidase (GPx), by catalytically decomposing S-nitrosothiols (RSNO) into NO and the corresponding free thiol. Model polymeric materials, e.g., cellulose filter paper and polyethylenimine, are modified with an appropriate diselenide species covalently linked to the polymeric structures. Such organoselenium (RSe)-derivatized polymers are shown to generate NO from RSNO species in the presence of an appropriate thiol reducing agent (e.g., glutathione). The likely involvement of both immobilized selenol/selenolate and diselenide species for NO production is suggested via a catalytic pathway, as deduced in separate homogeneous solution phase experiments using non-immobilized forms of small organodiselenide species. Preliminary experiments with the new RSe-polymers clearly demonstrate the ability of such materials to generate NO from RSNO species even after the contact with fresh animal plasma. It is anticipated that such NO generation from endogenous S-nitrosothiols in blood could render RSe-containing polymeric materials more thromboresistant when in contact with flowing blood, owing to NO's ability to inhibit platelet adhesion and activation.

Animals↗
PubMed2005

Direct detection of S-nitrosothiols using planar amperometric nitric oxide sensor modified with polymeric films containing catalytic copper species.

The direct amperometric detection of S-nitrosothiol species (RSNOs) is realized by modifying a previously reported amperometric nitric oxide gas sensor with thin hydrophilic polyurethane films containing catalytic Cu(II)/(I) sites. Catalytic Cu(II)/(I)-mediated decomposition of S-nitrosothiols generates NO(g) in the thin polymeric film at the distal tip of the NO sensor. Three different species are examined to create the catalytic layer: (1) a lipophilic Cu(II)-ligand complex; (2) Cu(II)-phosphate salt; and (3) small (3-microm) metallic Cu(0) particles. All three catalytic layers yield reversible amperometric response in proportion to the concentration of S-nitrosothiols (e.g., nitrosocysteine, nitrosoglutathione, S-nitroso-N-acetylcysteine, S-nitrosoalbumin) present in the aqueous test solution. Sensitivity toward the different RSNO species is dependent on the respective catalytic rates of decomposition of the RSNO species by reactive Cu(I), accessibility of the species into the polyurethane layer containing the catalyst, the level of reducing agents (ascorbate) used in solution to help generate reactive Cu(I) species, and the concentration of metal ion complexing agents present in the test solution (e.g., EDTA). Under optimized conditions, all RSNO species can be detected at < or =1 microM levels, with sensor lifetimes of at least 10 days for the sensors based on Cu(II)-phosphate and Cu0 particles. It is further shown that the new RSNO sensors can be used to assess the "NO-generating" ability of fresh blood samples by effectively detecting the total level of reactive RSNO species present in such samples.

Animals↗