• Nano
• /
• v.13 no.11
• /
• pp.1850131.1-1850131.19
• /
• 2018

In this paper, an electrochemical sensor for epinephrine (EP), a neurotransmitter was developed by anchoring molecularly imprinted polymeric matrix (MIP) on the surface of gold-coated quartz crystal electrode of electrochemical quartz crystal microbalance (EQCM) using starch nanoparticles (Starch NP) - reduced graphene oxide (RGO) nanocomposite as polymeric format for the first time. Use of EP in therapeutic treatment requires proper dose and route of administration. Proper follow-up of neurological disorders and timely diagnosis of them has been found to depend on EP level. The MIP sensor was developed by electrodeposition of starch NP-RGO composite on EQCM electrode in presence of template EP. As the imprinted sites are located on the surface, high specific surface area enables good accessibility and high binding affinity to template molecule. Differential pulse voltammetry (DPV) and piezoelectrogravimmetry were used for monitoring binding/release, rebinding of template to imprinted cavities. MIP-coated EQCM electrode were characterized by contact angle measurements, AFM images, piezoelectric responses including viscoelasticity of imprinted films, and other voltammetric measurements including direct (DPV) and indirect (using a redox probe) measurements. Selectivity was assessed by imprinting factor (IF) as high as 3.26 (DPV) and 3.88 (EQCM). Sensor was rigorously checked for selectivity in presence of other structurally close analogues, real matrix (blood plasma), reproducibility, repeatability, etc. Under optimized conditions, the EQCM-MIP sensor showed linear dynamic ranges ($1-10{\mu}M$). The limit of detection 40 ppb (DPV) and 290 ppb (EQCM) was achieved without any cross reactivity and matrix effect indicating high sensitivity and selectivity for EP. Hence, an eco-friendly MIP-sensor with high sensitivity and good selectivity was fabricated which could be applied in "real" matrices in a facile manner.

• Journal of Biosystems Engineering
• /
• v.32 no.5
• /
• pp.348-353
• /
• 2007

A solid state ion sensor module has been developed and evaluated for hydroponic nutrients analysis. The sensor module consisted of five ion-selective electrodes (ISE) fabricated by screen-printing technology. The electrochemical responses of ion sensors for nitrate, ammonium, potassium, calcium, and pH were measured with specially designed 7-channel low voltage signal transducers. The analytical characteristics of the sensors were comparable with those of conventional ISE sensors. The solid state ion sensors exhibit linear relationships over five concentration decades. Detection limit of the sensors were $5.6{\times}10^{-5}{\sim}1.6{\times}10^{-7}M$ depends on ions. Performance test results showed that relative errors of measured ion concentrations were less than 5% for $NO_3{^-},\;K^+,\;Ca^{2+}$ ion, and pH. The concentration of $NO_3{^-},\;NH_4{^+},\;K^+,\;Ca^{2+}$, and pH ion in standard solution and nutrient solutions could be determined by direct potentiometric measurements without any conditioning before measurements.