CHEMICALLY MODIFIED ELECTRODES AS BIOSENSORS: AMPEROMETRIC GLUCOSE SENSOR FOR FLOW INJECTION ANALYSIS

An amperometric biosensor was constructed for glucose blood serum determinations with flow injection analysis. A platinized, reticulated vitreous carbon (RVC) electrode is used as an enzyme support, reactor, and detector. A partial platinum coating provided an increased current response from the oxidation of hydrogen peroxide, as compared with a bare RVC electrode. It also allowed the electrode to operate at a much lower potential (+0.6 vs +0.9 volts vs SCE), thus resulting in an increased signal to noise ratio. However, carbonaceous sites were still available for enzyme immobilization. Glucsseloxidase (E.eC2 1T.1IE 3.4) is immobilized on the surface of the RVC electrode to provide selectivity for glucose and to produce an electroactive product, hydrogen peroxide. The enzyme is immobilized by either covalent attachment with carbodiimide or cross-linking with glutaraldehyde. The enzyme remained active for over three months with almost daily use. An electropolymerized film of 1,2-diaminobenzene was incorporated on the sensor to eliminate the effects of electrochemically active interferences present in serum samples. The polymer film also virtually eliminated electrode fouling caused by large proteins. The working lifetime of the sensor, as well as, the thermal stability of the immobilized glucose oxidase were increased by the polymer film

Genetic Diversity among Clinical Isolates of Acremonium strictum Determined during an Investigation of a Fatal Mycosis

Primarily saprophytic in nature, fungi of the genus Acremonium are a well-documented cause of mycetoma and other focal diseases. More recently, a number of Acremonium spp. have been implicated in invasive infections in the setting of severe immunosuppression. During the course of routine microbiological studies involving a case of fatal mycosis in a nonmyeloablative hematopoietic stem cell transplant patient, we identified a greater-than-expected variation among strains previously identified as Acremonium strictum by clinical microbiologists. Using DNA sequence analysis of the ribosomal DNA intergenic transcribed spacer (ITS) regions and the D1-D2 variable domain of the 28S ribosomal DNA gene (28S), the case isolate and four other clinical isolates phenotypically identified as A. strictum were found to have <99% homology to the A. strictum type strain, CBS 346.70, at the ITS and 28S loci, while a sixth isolate phenotypically identified only as Acremonium sp. had >99% homology to the type strain at both loci. These results suggest that five out of the six clinical isolates belong to species other than A. strictum or that the A. strictum taxon is genetically diverse. Based upon these sequence data, the clinical isolates were placed into three genogroups