A Biosensor for the Detection of Acetylcholine and Diazinon.

Acetylcholine is a neurotransmitter and a neuromodulator found in the autonomic, peripheral and central nervous systems. Diazinon is a pesticide with toxic effects on humans, such as the inhibition of acetylcholine. In this paper, a biosensor is proposed for the detection of acetylcholine (range 70 - 1000 µM) and diazinon (range 0.3 - 20000 ppb). This biosensor combines a pH-sensitive layer of reduced graphene oxide functionalized with 4-aminobenzoic acid and acetylcholinesterase. This enzyme was immobilized on reduced graphene oxide and it catalyzed the conversion of acetylcholine into choline and acetic acid, locally decreasing the pH value and triggering the sensor response. The limit of detection for the acetylcholine and diazinon were 70 µM and 0.3 ppb, respectively.

A graphene-based pH sensor on paper for human plasma and seawater.

The relevance of pH assessment in clinical analysis, environmental and industrial control, has raised the demand for the development of portable, low cost and easy-to-use monitoring systems. This paper proposes a pH sensor printed on a paper support passivated with a solid-ink coating. The sensor exploits the pH sensitivity of a reduced graphene oxide functionalized with 3-(4-aminophenil)propionic acid. The sensor responded in the pH range [4], [10] and had a sensitivity of 46 mV/pH. Tests on human plasma and seawater proved this pH sensor to have similar performances than those of a commercial pH-meter with an uncertainty of 0.1 and 0.2 pH unit in plasma and seawater, respectively.

Temperature and pH sensors based on graphenic materials.

Point-of-care applications and patients' real-time monitoring outside a clinical setting would require disposable and durable sensors to provide better therapies and quality of life for patients. This paper describes the fabrication and performances of a temperature and a pH sensor on a biocompatible and wearable board for healthcare applications. The temperature sensor was based on a reduced graphene oxide (rGO) layer that changed its electrical resistivity with the temperature. When tested in a human serum sample between 25 and 43°C, the sensor had a sensitivity of 110±10Ω/°C and an error of 0.4±0.1°C compared with the reference value set in a thermostatic bath. The pH sensor, based on a graphene oxide (GO) sensitive layer, had a sensitivity of 40±4mV/pH in the pH range between 4 and 10. Five sensor prototypes were tested in a human serum sample over one week and the maximum deviation of the average response from reference values obtained by a glass electrode was 0.2pH units. For biological applications, the temperature and pH sensors were successfully tested for in vitro cytotoxicity with human fibroblast cells (MRC-5) over 24h.

A graphene oxide pH sensor for wound monitoring.

This article describes the fabrication and characterization of a pH sensor for monitoring the wound status. The pH sensitive layer consists of a graphene oxide (GO) layer obtained by drop-casting 5 µÎ of GO dispersion onto the working electrode of a screen-printed substrate. Sensitivity was 31.8 mV/pH with an accuracy of 0.3 unit of pH. Open-circuit potentiometry was carried out to measure pH in an exudate sample. The GO pH sensor proved to be reliable as the comparison with results obtained from a standard glass electrode pH-meter showed negligible differences (<; 0.09 pH units in the worst case) for measurements performed over a period of 4 days.