Integrated potentiostat for electrochemical sensing of urinary 3-hydroxyanthranilic acid with molecularly imprinted poly(ethylene-co-vinyl alcohol).

Changing demographics, the rise of personalized medicine and increased identification of biomarkers for diagnosis and management of chronic disease have increased the demand for portable bioanalytical instrumentation and point-of-care. The recent development of molecularly imprinted polymers enables production of low cost and highly stable sensing chips; however, the commercially available and full functional instruments employed for electrochemical analysis have shortcomings in actual homecare applications. In this work, integrated circuits (ICs) for monolithic implementation of voltammeter potentiostat with a large dynamic current range (5 nA to 1.2 mA) and short conversion time (10 ms) were fabricated in a 0.35 µm complementary metal-oxide-semiconductor (CMOS) process. The new instrumentation was tested with molecular imprinted sensors for 3-hydroxyanthranilic acid (3HAA) in urine. The sensor consisted of molecular imprinted of poly(ethylene-co-vinyl alcohol)s (abbreviated as EVALs) for implementation in a flow injection analysis system. The EVAL containing 32 ethylene mol% had the highest imprinting effectiveness for the target molecules. Fit-for-purpose figures of merit were achieved with a limit-of-detection (LOD) of 3.06 pg/mL. The measurements obtained in real undiluted urine samples fell within the reference concentration range of 50-550 ng/mL.

A portable electrochemical sensor for caffeine and (-)epigallocatechin gallate based on molecularly imprinted poly(ethylene-co-vinyl alcohol) recognition element.

The U.S. Food and Drug Administration allows a maximum of 72 mg of caffeine per 12 oz. serving (6 mg/oz). Consuming 400 mg of caffeine 3 times daily for 7 days may develop sleep disruption effects. However, it is still very hard for people to estimate how much caffeine is intake daily. Moreover, (-)epigallocatechin gallate (EGCG) is studied a potent antioxidant that may have therapeutic properties for anti-aging and cancer. Conventionally, both caffeine and EGCG could be measured by the protocols of high performance liquid chromatography; however, high precision instruments are required. In this work, the caffeine and EGCG are used as the template molecules and imprinted into poly(ethylene-co-vinyl alcohol), EVAL, via solvent evaporation. The EVAL membrane is then used as the sensing element for electrochemical analysis after templates removal. From the cyclic voltammetry measurement of the caffeine, the peak oxidation potential is shifted from 0.36 to 0.46 V when the final concentration of caffeine is from 0.01 to 1 mg/mL, and the highest current density is about 0.18 microA/cm2. The caffeine and EGCG concentrations measured in three real samples are about 0.10-0.13 mg/mL and 0.49-1.74 mg/mL, respectively. This molecularly imprinted polymeric coated electrode is potential employed as a home-care system.

Urinalysis with molecularly imprinted poly(ethylene-co-vinyl alcohol) potentiostat sensors.

Among many important biomarkers excreted in urine are albumin, uric acid, glucose, urea, creatine and creatinine. In the growing elderly population, these biomarkers may be useful correlates with kidney dysfunction, infection and related problems such as glomerular, proximal, and distal convoluted tubule functions, diabetes, hypertension and proteinuria. This study employed solvent evaporation processing of poly(ethylene-co-vinyl alcohol), (EVAL) to form molecularly imprinted polymers (MIPs) that recognize creatinine, urea, and lysozyme. The mole ratio of ethylene to vinyl alcohol affected the performance: 27 mol% ethylene gave the highest imprinting effectiveness for creatinine and urea, while 44 mol% gave the highest effectiveness for lysozyme. Electrochemical examination using a home made potentiostat and imprinted polymer electrode showed electrical signals responsive to the target molecules. Finally, an actual urine sample was tested using the electrode. The test results were compared with those of the commercial instrument ARCHITECT ci 8200 system to precisely determine the accuracy of the molecularly imprinted polymer electrode for urinalysis.

A portable potentiostat for the bilirubin-specific sensor prepared from molecular imprinting.

A portable amperometric potentiostat was designed and implemented in this work. It was developed to acquisit the current signals produced from bilirubin by an electrochemical sensor. Based on an SOC-based chip, this potentiostat has the merits of moderate accuracy, small size, low cost, and high portability. The bilirubin electrode was prepared by synthesizing a thin layer of bilirubin imprinted poly(methacrylic acid-co-ethylene glycol dimethacrylate) onto the Au layer. With the molecularly imprinted polymer (MIP) film, specific detection of bilirubin was successfully achieved. The cyclic voltammogram of the electrode was measured from this assembled potentiostat. The performance from a commercial potentiostat was considered rather stable and was used as a reference to examine and evaluate the performance of the assembled potentiostat. The detected current signals by the bilirubin sensing were obtained. Linear calibration with a sensitivity of 1.344+/-0.38 microA/mg dl was achieved. Our experimental results showed that the proposed potentiostat's performance could achieve sufficient performance. The evaluation was also made from the aspects such as reset time and steady-response time. The self-assembled potentiostat thus demonstrated its ability in precise detection of bilirubin from an electrode layered with the imprinted polymer film.

Telemetric electrochemical sensor.

A telemetric system was designed and constructed to sense pH and ethanol variation in aqueous solutions. The measured signals were transferred by software digitally and transmitted wirelessly by the telemeter, personal digital assistant (PDA), through the General Packet Radio Service (GPRS) protocol. The pH sensing electrode was designed to measure a chemical potential induced by a proton concentration gradient on the electrode's surface which exhibits internal Donnon diffusion behavior, and a linear relationship between the electrical potential and pH was found. The result shows that the wireless sensing system allowed not only long-term usage and long-distance transmission but also with high accuracy (e.g. S.D. less than +/-2%). The telemetric system can also be modified to measure ethanol concentration in aqueous solution amperometrically. It was found that the sensitivity of that ex situ measurements matched those of in field measurements with negligible deviation, less than 4%.