Screen-printed Biosensor Research Articles

Screen-printed electrode based on AChE for the detection of pesticides in presence of organic solvents

A screen-printed biosensor for the detection of pesticides in water miscible organic solvents is described based on the use of p-aminophenyl acetate as acetylcholinesterase substrate. The oxidation of p-aminophenol, product of the enzymatic reaction was monitored at 100 mV vs. Ag/AgCl screen-printed reference electrode. Miscible organic solvents as ethanol and acetonitrile were tested. The acetylcholinesterase (AChE) was immobilised on a screen-printed electrode surface by entrapment in a PVA-SbQ polymer and the catalytic activity of immobilised AChE was studied in the presence of different percentages of organic solvents in buffer solution. The sensor shows good characteristics when experiments were performed in concentrations of organic solvents below 10%. No significant differences were observed when working with 1 and 5% acetonitrile in the reaction media. Detection limits as low as 1.91×10 −8 M paraoxon and 1.24×10 −9 M chlorpyrifos ethyl oxon were obtained when experiments are carried out in 5% acetonitrile.

Screen-printed biosensors for the control of wine quality based on lactate and acetaldehyde determination

Biosensors for d-lactate and acetaldehyde were developed, based on screen-printed electrodes and NAD +-dependent dehydrogenases. Modification of screen-printed electrodes with the mediator Meldola Blue or with Meldola Blue-Reinecke salt resulted in sensitive, low cost and reliable NADH detectors. The biosensors were realised in two configurations, as disposable and reusable devices. Single-use sensors were obtained by simple deposition of enzyme and cofactor on the surface of mediator-modified electrodes. Chronoamperometry was used for the detection of substrates in small volumes of samples (25 μl). Immobilisation of dehydrogenases by entrapment in poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ) allowed sensors to be obtained with sufficient operational stability. Amperometry in stirred solutions was the detection technique with biosensors for multiple use. The 3 σ detection limits for acetaldehyde were 1 μM by amperometry and 6 μM by chronoamperometry and for d-lactate-0.03 μM and 0.05 μM for reusable and disposable biosensors respectively. The biosensors were applied in the analysis of some French and Romanian wines.

Development of a screen-printed amperometric biosensor for the determination of l-lactate dehydrogenase level

We attempted to develop a screen-printed biosensor for the amperometric determination of l-lactate dehydrogenase (LDH) level on the basis of NAD +/NADH-dependent dehydrogenase reaction. The printing ink for the working electrode consisted of l-lactate, NAD +, composite polymer of hydroxyethyl cellulose with ethylene glycol, 3,4-dihydroxybenzaldehyde (3,4-DHB) as an electron transferring mediator, and graphite as the conducting material. The 3,4-DHB was electropolymerized on the carboneous working electrode by potential cycling between −200 and +300 mV vs. Ag/AgCl reference electrode. Through the electrocatalytic reaction with immobilized 3,4-DHB, the NADH generated by the LDH reaction could be efficiently oxidized at lower potential than the unmodified carbon electrode. The analytical performance of the electrode was characterized in terms of linear sensing range and detection limit for LDH. The response from the developed biosensor was linear up to 500 U/l of LDH, and the detection limit of 50 U/l was observed at the signal-to-noise ratio of 3.

Screen-printed biosensors using different alcohol oxidases

Low-cost screen-printed sensors consisting of a platinum working electrode, a carbon counter electrode, and an Ag/AgCl pseudo-reference electrode were fabricated for the development of alcohol oxidase biosensors. The sensors were fabricated as amperometric transducers for the detection of alcohols in batch systems. A mixture of alcohol oxidase (AOD) with poly(carbamoyl)sulfonate (PCS) hydrogel was used for enzyme immobilization onto the platinum electrodes. Alcohol oxidases from different sources such as from Hansenula sp., from Candida boidinii and from Pichia pastoris were used for immobilization. The performances of the resulting different sensors has been compared and characterized with respect to enzyme load, pH and temperature dependence, response time, recovery time, linear range and sensitivity. The relative response of sensors for different alcohols was measured to evaluate the selectivity of the sensors. The effect of ascorbic acid and sodium sulfite as electrochemical interferents on the sensor’s performance was investigated. The continuous operation and storage stability of the sensors were also evaluated. Most of the characterization parameters were found to be superior for sensors with immobilized AOD from Hansenula sp. The sensors were also tested with wine samples. The results obtained by the newly developed biosensors were compared to results obtained by pycnometry, the well-established reference method as well as gas chromatograph method.

SIMULTANEOUS DETERMINATION OF GLUCOAMYLASE ACTIVITY AND GLUCOSE IN FERMENTATION PROCESS BASED ON SCREEN-PRINTED DISPOSABLE BIOSENSOR

Screen-printed disposable biosensor with dualcarbon working electrodes and an Ag/AgCl reference electrode was developed for simultaneous determination of glucoamylase (GA) activity and glucose. Such determination can be accomplished in 1 min by immobilizing glucose oxidase (GOD) and GOD/starch onto different working electrodes. The method was based on electrochemical detection of glucoamylase-catalyzed glucose from the starch layer coupling with mediator oxidation. Cyclic voltammetry was employed to demonstrate the principle. Chronoamperometry at + 0.4 V versus Ag/AgCl was performed without incubation time. The linear response ranges were up to 20-mmol/l glucose and 150-U/ml GA. The method was applied to the measurements of glucose and GA activity in fungal fermentation process, and exhibited good agreement with the reference method.

Recent developments towards disposable screen-printed biosensors incorporating a carbon ink modified with the redox mediotor. Meldola's Blue

Screen-printed carbon electrodes (SPCEs) can be mass-produced at low cost and are readily adaptable as base transducers for incorporation into disposable biosensors. As biological recognition elements, the NAD + -dependent dehydrogenase enzymes have wide ranging application for the determination of many analytes in biological samples. In order to achieve the desired selectivity, it has proved necessary to reduce the overpotential required to electrochemically regenerate the cofactor, NAD + , by incorporating redox mediators into the carbon ink prior to screen-printing. One such electrocatalyst, Meldola's Blue (MB), has been used successfully and has been combined with dehydrogenase enzymes for the determination of some important biological analytes, including lactate, alcohol and ammonia. These examples from our laboratory using MB-modified SPCEs will be reviewed in this article, together with a recent application to determine aspartate aminotransferase (AST) in serum.

Application of dual-step potential on single screen-printed modified carbon paste electrodes for detection of amino acids and proteins

A novel screen-printed biosensor for protein and amino acid (AA) estimation is reported. A rhodinised carbon paste working electrode (WE) was used in the three-electrode configuration. Bromine was generated by the electrolysis of an acidic potassium bromide electrolyte on the working electrode when poised at an appropriate potential. The consumption of bromine by the protein and amino acid was then measured at a lower potential. This sensor was used to detect most of the amino acids and some common proteins. The method is highly sensitive and can even detect L- and D- proline which give no response with enzyme electrodes. This sensor has also been used to detect protein/amino acid in fruit juice, milk, and urine. The unique feature of the sensor is that it does not require any reagent/chemical other than buffer. No surface treatment or modification of the WE is necessary and hence the sensor is stable for the lifetime of the basic screen-printed electrode, which is about a year. A very small amount of analyte (10 μL) is required for direct detection. The sensor is inexpensive and disposable and may also be used for continuous-flow systems. This sensor may have useful application in process monitoring and control during the production of amino acids.

Disposable screen-printed enzyme sensor for simultaneous determination of starch and glucose

A disposable screen-printed biosensor with dual working electrodes was first established for simultaneous determination of starch and glucose. The electrochemical behavior of the sensor was assessed using cyclic voltammetry and chronoamperometry. The linear response ranges of the sensor were up to 0.4% (w/v) starch and 20 mmol glucose 1−1. Real samples were analysed using the proposed method and the reference method and the correlation coefficient was 0.997.

Disposable ruthenized screen-printed biosensors for pesticides monitoring

A disposable choline biosensor based on ruthenized carbon screen-printed electrodes has been prepared and its use for monitoring organophosphorus pesticides and carbamates is described. The presence of 0.5% ruthenium on activated carbon mixed to form a simple graphite-based ink for the working electrode surface increased the sensitivity towards hydrogen peroxide. The choline biosensor is based on such an electrode coupled with choline oxidase immobilized by adsorption. The inhibition effect of carbamates and organophosphorus pesticides on acetylcholinesterase was detected using this biosensor. With the optimized procedure described (pH, buffer composition, incubation time, substrate concentration) we are able to detect concentrations of pesticides (carbofuran) as low as 1 nM.

Development of one-shot biosensors for the measurement of uric acid and cholesterol

This paper is a case study in the design, fabrication and characterization of screen-printed biosensors for the measurement of uric acid and cholesterol. Four different detection strategies, namely direct oxidation, direct mediation, direct enzyme-linked mediation and indirect electrochemical oxidation are discussed with their accompanying selectivity profiles. The work culminates in the production of disposable, printed biosensors for uric acid and cholesterol; the merits and demerits of each system are outlined. Such biosensors are based on novel solid-phase biochemistry and are likely to enable simple, reagentless and convenient near-patient testing. The potentialities of such a decentralized approach to analysis are also described.

USA — Screen-printed biosensors based on ruthenium-dispersed carbon inks : In ANAL. CHIM. ACTA (300/1–3 (111–116) 1995) J. Wang, Q. Chen, M. Pedrero & J.M. Pingarron of New Mexico State University report on “Screen-printed amperometric biosensors for glucose and alcohols based on ruthenium-dispersed carbon inks”

USA — Screen-printed biosensors based on ruthenium-dispersed carbon inks : In ANAL. CHIM. ACTA (300/1–3 (111–116) 1995) J. Wang, Q. Chen, M. Pedrero & J.M. Pingarron of New Mexico State University report on “Screen-printed amperometric biosensors for glucose and alcohols based on ruthenium-dispersed carbon inks”

Fabrication and characterization of a screen-printed, disposable, amperometric cholesterol biosensor

A single-use, reagentless, screen-printed biosensor strip for the measurement of free cholesterol was fabricated and its performance characteristics were evaluated by cyclic voltammetry and under steady-state conditions. Cholesterol oxidase was adsorbed on the surface of an H2O2-sensing cobalt phthalocyanine screen-printed carbon electrode and retained at the sensory interface with a solvent-cast cellulose acetate membrane. The device, operated in the amperometric mode, provides an inexpensive, reliable and rapid means of quantifying this clinically significant sterol. Its analytical utility is further augmented by its ease of fabrication and favourable storage properties. The biosensor exhibits a wide functional range (6 × 10–5–5.0 × 10–3 mol dm–3) and the sensitivities of the devices (slopes of the calibration graphs) were used to derive optimum solution conditions. Several analytical parameters were also investigated to optimize and enhance the response time and sensitivity of the sensor and these are also discussed.