RESUMO

Electrochemical ethanol oxidation was performed at an innovative hybrid architecture electrode containing TEMPO-modified linear poly(ethylenimine) (LPEI) and oxalate oxidase (OxOx) immobilized on carboxylated multi-walled carbon nanotubes (MWCNT-COOH). On the basis of chromatographic results, the catalytic hybrid electrode system completely oxidized ethanol to CO2 after 12 h of electrolysis. The fact that the developed system can catalyze ethanol electrooxidation at a carbon electrode confirms that organic oxidation catalysts combined with enzymatic catalysts allow up to 12 electrons to be collected per fuel molecule. The Faradaic efficiency of the hybrid system investigated herein lies above 87%. The combination of OxOx with TEMPO-LPEI to obtain a novel hybrid anode to oxidize ethanol to carbon dioxide constitutes a simple methodology with useful application in the development of enzymatic biofuel cells.

Assuntos

Eletrólise , Etanol/química , Dióxido de Carbono/química , Catálise , Óxidos N-Cíclicos/química , Eletrodos , Eletrólise/métodos , Enzimas Imobilizadas/química , Nanotubos de Carbono/química , Oxirredução , Oxirredutases/química , Polietilenoimina/química

RESUMO

MWCNT-COOH, TEMPO-modified linear poly(ethylenimine), and alcohol (ADH) and aldehyde (AldDH) dehydrogenase immobilization on electrode surfaces yields a hybrid, tri-catalytic architecture that can catalyze complete ethanol electro-oxidation. The chromatographic results obtained for the tri-catalytic hybrid electrode system show that ethanol is totally oxidized to CO2 after 12 h of electrolysis, confirming that organic oxidation catalysts combined with enzymatic catalysts enable collection of up to 12 electrons from ethanol. The Faradaic efficiency lies above 60% for all of the electrode systems investigated herein. Overall, this study illustrates that surface-immobilized, polymer hydrogel-based hybrid multi-catalytic systems exhibit high oxidation rates and constitute a simple methodology with useful application in the development of enzymatic biofuel cells.

Assuntos

Biocombustíveis , Eletroquímica , Etanol/metabolismo , Dióxido de Carbono/química , Catálise , Eletrodos , Enzimas Imobilizadas/metabolismo , Etanol/química , Oxirredução

RESUMO

Transplantation of kidneys from donors over the age of 60 yr is controversial. However, as the demand for cadaveric kidneys far exceeds the supply, exploration of the usefulness of kidneys outside the currently accepted donor pool is necessary. Between January 1987 and July 1989, 31 (5.5%) of the 558 cadaveric renal transplants performed at the University of Pittsburgh utilized organs from donors older than 60 yr. Median recipient age was 41 yr (range 24-71 yr); 4 recipients were diabetic and 6 had panel-reactive antibody levels greater than 20% at the time of transplant. All recipients were treated with cyclosporine, prednisone and azathioprine. The 1-yr allograft survival was 65% which was less than but not statistically different from the graft survival of 80% in a retrospective selected control group who received grafts from younger donors aged 11 to 50 yr. However, the 1-yr graft survival of older donor kidneys with cold ischemia time greater than 48 hours was 38%, which was significantly poorer than the 78% 1-yr graft survival seen with cold ischemia times less than 48 h (p=0.04 Breslow). The mean serum creatinine was significantly higher in the older donor kidneys at 1, 3, and 12 months post-transplant than in the control kidneys even when kidneys with greater than 48 h of cold ischemia time were excluded. In summary, transplantation of cadaver kidneys from donors older than 60 yr results in acceptable graft survival rates. These kidneys are more susceptible to cold ischemic injury and function with a higher serum creatinine than kidneys from younger donors. Expansion of the donor pool by the use of older donor kidneys in selected recipients could have an impact on alleviating the chronic national cadaver kidney shortage.