Simultaneous Electrochemical Evaluation of Ascorbic Acid, Epinephrine and Uric Acid at Disposable Pencil Graphite Electrode: Highly Sensitive Determination in Pharmaceuticals and Biological Liquids by Differential Pulse Voltammetry

AIM AND OBJECTIVE

As is known, AA, EP and UA can also coexist in biological fluids. Therefore, the determination of the levels of these compounds in biological fluids is extremely important both for the diagnosis and treatment of the related diseases. In the presence of many interfering substances in biological fluids such as blood and urine samples, it is very important that these compounds can be selectively analyzed.

MATERIALS AND METHODS

All electrochemical experiments were performed using an Autolab PGSTAT 128N potentiostat. Before beginning the electrochemical measurements, the PGE was activated. The electrochemical pretreatment of PG was exercised by anodically +1.40 V for 60 s. Then, measurements were performed with CV (-0.4 V to 1.2 V) and DPV (-0.2 V to 0.7 V) for single and simultaneous voltammetric behaviour of AA, EP, and UA in the electrochemical method.

RESULTS

The anodic peak potentials of AA and UA were observed at about +0.32 V and +0.62 V, respectively. On the other hand, for EP, while anodic peak potential was observed at about +0.53 V, in the reverse scan, cathodic peak potentials were observed at about +0.41 V and +0.007 V. The reduction peak observed at +0.3 V with the oxidation peak observed at +0.53 V are the reversible peaks. In the method developed for the electrochemical simultaneous determination of AA, EP and UA using PGE with DPV technique in BR buffer solution (pH 4.0), the anodic peak potentials are sufficiently separated from each other.

CONCLUSION

A voltammetric method was developed for the simultaneous determination of AA, EP and UA with PGE for the first time. Here, the most important thing is that the simultaneous determination of AA, EP and UA was successfully achieved with that targeted voltammetric method which was sensitive, low-cost, practical and well-repeated; and that these were proven to be selectively applicable in pharmaceutical products and biological liquids.

Liquid-liquid phase separation in biology

Cells organize many of their biochemical reactions in non-membrane compartments. Recent evidence has shown that many of these compartments are liquids that form by phase separation from the cytoplasm. Here we discuss the basic physical concepts necessary to understand the consequences of liquid-like states for biological functions.

A Realtime and Continuous Assessment of Cortisol in ISF Using Electrochemical Impedance Spectroscopy

This study describes the functioning of a novel sensor to measure cortisol concentration in the interstitial fluid (ISF) of a human subject. ISF is extracted by means of vacuum pressure from micropores created on the stratum corneum layer of the skin. The pores are produced by focusing a near infrared laser on a layer of black dye material attached to the skin. The pores are viable for approximately three days after skin poration. Cortisol measurements are based on electrochemical impedance (EIS) technique. Gold microelectrode arrays functionalized with Dithiobis (succinimidyl propionate) self-assembled monolayer (SAM) have been used to fabricate an ultrasensitive, disposable, electrochemical cortisol immunosensor. The biosensor was successfully used for in-vitro measurement of cortisol in ISF. Tests in a laboratory setup show that the sensor exhibits a linear response to cortisol concentrations in the range 1 pm to 100 nM. A small pilot clinical study showed that in-vitro immunosensor readings, when compared with commercial evaluation using enzyme-linked immunoassay (ELISA) method, correlated well with cortisol levels in saliva and ISF. Further, circadian rhythm could be established between the subject's ISF and the saliva samples collected over 24 hours time-period. Cortisol levels in ISF were found reliably higher than in saliva. This Research establishes the feasibility of using impedance based biosensor architecture for a disposable, wearable cortisol detector. The projected commercial in-vivo real-time cortisol sensor device, besides being minimally invasive, will allow continuous ISF harvesting and cortisol monitoring over 24 hours even when the subject is asleep. Forthcoming, this sensor could be interfaced to a wireless health monitoring system that could transfer sensor data over existing wide-area networks such as the internet and a cellular phone network to enable real-time remote monitoring of subjects.