A planar amperometric creatinine biosensor employing an insoluble oxidizing agent for removing redox-active interferences.

A planar microchip-based creatinine biosensor employing an oxidizing layer (e.g., a PbO2 film), where interfering redox-active substances are broken (i.e., oxidized) to redox-inactive products, was developed to facilitate the microfabrication of the sensor and to provide improved, reliable determination of creatinine in physiological samples. The feasibility of using hydrophilic polyurethanes in permselective barrier membranes for creatinine biosensors and the effect of adding a silanizing agent (adhesion promoter) on the sensor performance (e.g., sensitivity, stability, and lifetime) are described. The proposed creatinine microsensor with a three-layer configuration, i.e., enzyme, protecting, and oxidizing layers, exhibits good electrochemical performance in terms of response time (t95% = 98 s at 100-->200 microM creatinine change), linearity (1-1000 microM, r = 0.9997), detection limit (0.8 microM), and lifetime (approximately 35 days). The creatinine biosensor devised in a differential sensing arrangement that compensates the erroneous results from creatine is considered to be suitable for assay of serum specimens.

Receptor activator of NF-kappaB recruits multiple TRAF family adaptors and activates c-Jun N-terminal kinase.

Receptor activator of NF-kappaB (RANK) is a recently cloned member of the tumor necrosis factor receptor (TNFR) superfamily, and its function has been implicated in osteoclast differentiation and dendritic cell survival. Many of the TNFR family receptors recruit various members of the TNF receptor-associated factor (TRAF) family for transduction of their signals to NF-kappaB and c-Jun N-terminal kinase. In this study, the involvement of TRAF family members and the activation of the JNK pathway in signal transduction by RANK were investigated. TRAF1, 2, 3, 5, and 6 were found to bind RANK in vitro. Association of RANK with each of these TRAF proteins was also detected in vivo. Expression of RANK in cultured cells also induced the activation of JNK, which was blocked by a dominant-negative form of JNK. Furthermore, by employing various C-terminal deletion mutants of RANK, the regions responsible for TRAF interaction and JNK activation were identified. TRAF5 was determined to bind to the C-terminal 11 amino acids and the other TRAF members to a region N-terminal to the TRAF5 binding site. The domain responsible for JNK activation was localized to the same region where TRAF1, 2, 3, and 6 bound, which suggests that these TRAF molecules might mediate the RANK-induced JNK activation.