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Biosensors are systems that can perform a quantitative and/or qualitative analysis of substances in a liquid or gas environment through their biological recognition sites and transform the acquired data into detectable signals. Biosensors are able to detect physical changes (i.e. as density, mass concentration, etc.) by means of recognition sites and correlate them with electrical or optical quantities (i.e. current, voltage and impedance). In this study, three molecularly imprinted pencil graphite electrodes (PGE) with differing numbers of choline recognition sites, at E-1 M, E-3 M and E-5 M concentration, were used as electrochemical biosensors. An increase in choline receptor concentration on the electrode surface was expected to correlate with an increase in PGE surface bound choline and thus lead to electrical changes. The study was conducted in a three-electrode cell with Ag/AgCl as the reference electrode, platinum wire as the counter electrode and PGE as the working electrode. Cyclic voltammetry and electrochemical impedance measurements were conducted in 10 mM phosphate buffer solution (PBS) containing 5mM K3[FeCN6]-3/-4 redox pair. As expected, as increasing amount of choline was bound to the complementary recognition sites on choline imprinted PGEs, a correlating change in current, voltage and impedance on PGEs was observed. The dynamic detection range for choline expanded as the choline concentration imprinted on the PGE electrode increased. Using the E-1 M PGE electrode, 72 pM limit of detection, up to 7.2 nM limit of linearity was attained.

In present work, gold nanorods were used for amplification of electrochemical sensing of anti-HIV replication drug i.e. deferiprone. Gold nanorods (nano Au) deposited onto pencil graphite electrode (PGE) has been utilized for covalent immobilization of horse radish peroxidase (HRP), via glutaraldehyde (Glu), for deferiprone detection using impedimetric technique. Gold nanorods (nano Au) prepared were characterized by TEM and XRD. The resulting nano Au sensor exhibited a good response to deferiprone with a wide linear range (0.005–1000 µM) and a low detection limit 0.005 µM. The biosensor also showed a short response time (within 15 s). In addition, the biosensor exhibited high reproducibility, good storage stability and anti-interference ability. The applicability of the nano Au sensor is to determine deferiprone level in spiked urine and serum samples. [ABSTRACT FROM AUTHOR]