Most important biomedical applications of ion-selective electrodes

2 Most important biomedical applications of ion-selective electrodes 

Clinical chemistry, particnlarly the determination of the biologically relevant electrolytes in physiological flnids, remains the key area of ISEs application [15], as billions of rontine measnrements with ISEs are performed each year all over the world [16]. The concentration ranges for the most important physiological ions detectable in blood flnids with polymeric ISEs are shown in Table 4.1. Sensors for pH and for ionized calcinm, potassinm and sodinm are approved by the International Federation of Clinical Chemistry (IFCC) and implemented into commercially available clinical analyzers [17]. Moreover, magnesinm, hthium, and chloride ions are also widely detected by corresponding ISEs in blood liquids, urine, hemodialysis solutions, and elsewhere. Sensors for the determination of physiologically relevant polyions (heparin and protamine), dissolved carbon dioxide, phosphates, and other blood analytes, intensively studied over the years, are on their way to replace less reliable and/or awkward analytical procedures for blood analysis (see below). 

In contrast to other analytical methods, ion-selective electrodes respond to an ion activity, not concentration, which makes them especially attractive for clinical applications as health disorders are usually correlated to ion activity. While most ISEs are used in vitro, the possibility to perform measurements in vivo and continuously with implanted sensors could arm a physician with a valuable diagnostic tool. In-vivo detection is stiU a challenge, as sensors must meet two strict requirements first, minimally perturb the in-vivo environment, which could be problematic due to injuries and inflammation often created by an implanted sensor and also due to leaching of sensing materials second, the sensor must not be susceptible to this environment, and effects of protein adsorption, cell adhesion, and extraction of lipophilic species on a sensor response must be diminished [13]. Nevertheless, direct electrolyte measurements in situ in rabbit muscles and in a porcine beating heart were successfully performed with microfabricated sensor arrays [18]. 

The relative simplicity of the sensor setup allows them to be implemented into portable automated devices or bed-side analyzers (Fig. 4.2), which are easily installed at patient beds, eliminating the time-consuming laboratory analyses. On the other hand, modem high throughput clinical analyzers may process more than 1000 samples per hour and simultaneonsly determine dozens of analytes, using a handful of analytical methods. Blood electrolyte analysis, however, remains one of the most important in 

Electrochemical Sensors, Biosensors and Their Biomedical Applications 

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