Bioelectrode systems

The future of ISEs in the clinical chemistry instrumentation is quite exciting. As described in subsequent sections of this article, the coupling of enzyme and immunological reagents to ISE detectors to form bioelectrode systems appears to offer manufacturers a new approach toward the detection of metabolites such as creatinine and urea directly in blood and urine samples. Ultimately, such biosensors will be placed into complete electrode-based automated clinical analyzers. In addition, continued research on new membrane formulations, particularly liquid membrane ionophore systems, will result in the development of addition electrodes which can be incorporated into current analyzer systems to expand the electrolyte menu. Indeed, recent efforts have indicated that membranes selective fi)r bicarbonate (F5) and lithium (Z2) are likely additions in the near future. 

Little SJ, Ralph SF, Mano N, Chen J, Wallace GG. A novel enzymatic bioelectrode system combining a redox hydrogel with a carbon NanoWeb. Chem Commun 2011 47 8886-8888. 

Electrical Stimulation Devices. Bioelectrodes that transmit electrical signals into the body are generally known as electrical stimulation devices, examples of which include cardiac pacemakers, transcutaneous electronic nerve stimulators (TENs) for pain suppression, and neural prostheses such as auditory stimulation systems for the deaf and phrenic nerve stimulators for artificial respiratory control. In these, and other similar devices, electrodes transmit current to appropriate areas of the body for direct control of, or indirect influence over, target cells. 

Immobilized /3-glucosidase served for enzymatically catalyzed hydrolysis of benzene metabolites in urine. End analysis of phenol was by RP-HPLC with ELD at 0.85 V vi. Ag/AgCl electrode. ELD avoids interference from other componnds present in urine. LOD was 10 p.gL" (20 p,L injection, 0.2 ng), with RSD 1.16% and 3.38% for 1.2 ng and 2.0 ng, respectively. A stndy was carried out of two FIA systems for enzymatically catalyzed determination of dopamine (10a). Thus, a combination of a packed bed reactor containing immobilized tyrosinase followed by photometric detection was compared with ELD based on a graphite electrode with its surface covered by immobilized tyrosinase. The former configuration was linear up to 0.75 mM while the latter reached 1 mM. LC separation and post-column detection with the bioelectrode was applied to analysis of spiked serum samples. ... 

FIGURE 5.5 Schematic diagram of the flow system developed for the multiplexed detection of glucose, fructose, and sucrose using enzyme bioelectrodes as ampero-metric biosensors. (Reprinted from Vargas, E. et al. 2013. Talanta 105 93-100. With permission.)... 

---