This review describes recent advances in the fabrication of electrochemical (bio)sensors based on screen-printing technology involving carbon materials and their application in biomedical, agri-food and environmental analyses. It will focus on the various strategies employed in the fabrication of screen-printed (bio)sensors, together with their performance characteristics; the application of these devices for the measurement of selected naturally occurring biomolecules, environmental pollutants and toxins will be discussed.

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Disclaimer UWE has obtained warranties from all depositors as to their title in the material deposited and as to their right to deposit such material. UWE makes no representation or warranties of commercial utility, title, or fitness for a particular purpose or any other warranty, express or implied in respect of any material deposited. UWE makes no representation that the use of the materials will not infringe any patent, copyright, trademark or other property or proprietary rights.UWE accepts no liability for any infringement of intellectual property rights in any material deposited but will remove such material from public view pending investigation in the event of an allegation of any such infringement. The biosensor was fabricated by sequentially depositing the components on the surface of the transducer (MB-SPCE) in a layer-by-layer process, details of which are included in the paper. Each layer was optimized to construct the reagentless device.The biosensor was used in conjunction with amperometry in stirred solution using an applied potential of +0.1V (vs. Ag/AgCl). Optimum conditions for the analysis of glutamate were found to be: temperature, 35°C; phosphate buffer, pH 7 (0.75 mM, containing 0.05 M NaCl).The linear range of the reagentless biosensor was found to be 7.5 µM to 105 µM, and limit of detection was found to be 3 µM (based on n = 5, CV: 8.5% based on three times signal to noise) and the sensitivity was 0.39 nA/µM (± 0.025, coefficient of variation (CV) of 6.37%, n = 5). The response time of the biosensor was 20 -30 seconds.A food sample was analysed for monosodium glutamate (MSG). The endogenous content of MSG was 90.56 mg/g with a CV of 7.52%.The reagentless biosensor was also used to measure glutamate in serum. The endogenous concentration of glutamate was found to be 1.44 mM (n = 5), CV: 8.54%. The recovery of glutamate in fortified serum was 104% (n = 5), CV of 2.91%.

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This paper describes a simple, convenient approach to the fabrication of microband electrodes and microband biosensors based on screen printing technology. These devices were printed in a three‐electrode configuration on one strip; a silver/silver chloride electrode and carbon counter electrode served as reference and counter electrodes respectively. The working electrodes were fabricated by screen‐printing a water‐based carbon ink containing cobalt phthalocyanine for hydrogen peroxide detection. These were converted into a glucose microband biosensor by the addition of glucose oxidase into the carbon ink. In this paper, we discuss the fabrication and application of glucose microband electrodes for the determination of glucose in cell media. The dimensions (100–400 microns) of the microband electrodes result in radial diffusion, which results in steady state responses in the absence of stirring. The microband biosensors were investigated in cell media containing different concentrations of glucose using chronoamperometry. The device shows linearity for glucose determination in the range 0.5 mM to 2.5 mM in cell media. The screen‐printed microband biosensor design holds promise as a generic platform for future applications in cell toxicity studies.

A reagentless biosensor has been successfully developed to measure glutamate in food and clinical samples. The enzyme, glutamate dehydrogenase (GLDH) and the cofactor, nicotinamide adenine dinucleotide (NAD) are fully integrated onto the surface of a Meldola's Blue screen-printed carbon electrode (MB-SPCE). The biological components are immobilized by utilizing unpurified multi-walled carbon nanotubes (MWCNT's) mixed with the biopolymer chitosan (CHIT), which are drop-coated onto the surface of the MB-SPCE in a layer-by-layer fashion. Meldola's Blue mediator is also incorporated into the biosensor cocktail in order to increase and facilitate electron shuttling between the reaction layers and the surface of the electrode. The loadings of each component are optimized by using amperometry in stirred solution at a low fixed potential of +0.1 V. The optimum temperature and pH are also determined using this technique. Quantification of glutamate in real samples is performed using the method of standard addition. The method of standard addition involves the addition of a sample containing an unknown concentration of glutamate, followed by additions of known concentrations of glutamate to a buffered solution in the cell. The currents generated by each addition are then plotted and the resulting line is extrapolated in order to determine the concentration of glutamate in the sample (Pemberton et al., Biosens Bioelectron 24:1246-1252, 2009). This layer-by-layer approach holds promise as a generic platform for the fabrication of reagentless biosensors.

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Disclaimer UWE has obtained warranties from all depositors as to their title in the material deposited and as to their right to deposit such material. UWE makes no representation or warranties of commercial utility, title, or fitness for a particular purpose or any other warranty, express or implied in respect of any material deposited. UWE makes no representation that the use of the materials will not infringe any patent, copyright, trademark or other property or proprietary rights. UWE accepts no liability for any infringement of intellectual property rights in any material deposited but will remove such material from public view pending investigation in the event of an allegation of any such infringement. A mixture of the enzyme glutamate dehydrogenase (GLDH), cofactor nicotinamide adenine dinucleotide (NAD + ) and the biopolymer chitosan (CHIT) were drop-coated onto the surface of the transducer (MB-SPCE) in a simple one step fabrication process.The reagentless biosensor was used with amperometry in stirred solution at an applied potential of +0.1 V (vs. Ag/AgCl). All experiments were carried out at the following conditions: pH 7, temperature 37ºC, atmosphere 5% CO 2 .The linear range of the device was found to be 25 -125 μM in phosphate buffer (75 mM, containing 0.05 M NaCl) and 25 -150 μM in cell culture medium. The limits of detection (LOD) were found to be 1.2 µM and 4.2 µM based on three times signal to noise, using PBS and culture medium respectively. The sensitivity was calculated to be 106 nA µM -1 cm -2 and 210 nA µM -1 cm -2 in PBS and cell medium respectively. The response time was ~60s in an agitated solution.HepG2 cells were exposed to various concentrations of paracetamol (1 mM, 5 mM and 10 mM) in order to investigate the drug-induced release of glutamate into the culture medium in real time. Two toxicity studies were investigated using different methods of exposure and analysis.The first method consisted of a single measurement of the glutamate concentration, using the method of standard addition, after 24 hours incubation. The concentrations of glutamate were 3 found to be 52µM, 93µM and 177µM, released on exposure to 1mM, 5mM and 10mM paracetamol respectively.The second method involved the continuous monitoring of glutamate released from HepG2 cells upon exposure to paracetamol over 8 hours. The concentrations of glutamate released in the presence of 1mM, 5mM and 10mM paracetamol, increased in proportion to the drug concentration, ie: 16µM, 28µM and 62µM respectively. This result demonstrates the feasibility of using this approach to monitor early metabolic changes after exposure to a model toxic compound.