Potassium ion-sensitive field effect transistors using valinomycin doped photoresist membrane

Ion-Selective Carbon Nanotube Field-Effect Transistors for Monitoring Drug Effects on Nicotinic Acetylcholine Receptor Activation in Live Cells

We developed ion-selective field-effect transistor (FET) sensors with floating electrodes for the monitoring of the potassium ion release by the stimulation of nicotinic acetylcholine receptors (nAChRs) on PC12 cells. Here, ion-selective valinomycin-polyvinyl chloride (PVC) membranes were coated on the floating electrode-based carbon nanotube (CNT) FETs to build the sensors. The sensors could selectively measure potassium ions with a minimum detection limit of 1 nM. We utilized the sensor for the real-time monitoring of the potassium ion released from a live cell stimulated by nicotine. Notably, this method also allowed us to quantitatively monitor the cell responses by agonists and antagonists of nAChRs. These results suggest that our ion-selective CNT-FET sensor has potential uses in biological and medical researches such as the monitoring of ion-channel activity and the screening of drugs.

Vapour-generation analytical chemistry: from Marsh to multimode sample-introduction system

The history and state of knowledge of techniques available to analysts before the development of modern spectrometric techniques are surveyed in this paper. A variety of evaluative methods developed in the 19th century, with relatively minor improvements, remain in the repertoire of analysts even though they are at best semi-quantitative. Interferences with the vapour-generation reaction were identified early, as were the advantages and drawbacks of electrochemical vapour generation. This review attempts to present the earliest descriptions of vapour generation of elements and of the devices that have been used for their determination; phase-separation devices, in particular, are described.

Producing "self-plasticizing" ion-selective membranes

Polymer membranes have been explored for the analysis of ions that do not require plasticizers and with photocurable properties. This work was focused on investigating the viability of the methacrylic-acrylic copolymers as new self-plasticizing membrane matrixes for ion-selective electrodes or other ion-sensor applications. Copolymers with glass transition temperatures ranging from -20 to -44 degrees C could be prepared without added plasticizer and were found to be functional as ion-selective membranes. Both free-radical solution polymerization and photopolymerization could be used, and "self-plasticizing" behavior of copolymers was observed with a high alkylacrylate (R = C4) content. This was found to be compatible with most commercially available ionophores, and sensors for potassium, sodium, calcium and pH were fabricated entirely by photocure procedures; single-step procedures for the immobilization of benzo-15-crown-5 ionophore on these self-plasticizing copolymer matrixes were also developed. Even though the ionophore was immobilized, potentiometric studies revealed that the ionophore remained functional, and thus, these copolymers have the advantage of suffering neither leaching of ionophore nor plasticizers. All these sensors exhibited a Nernstian or near Nernstian response with selectivity comparable to plasticized PVC membranes or other plasticized and photocurable polymer membranes. The long-term response of the potassium sensor with immobilized ionophore and the sodium sensor showed little deterioration for as long as one month and three months, respectively, under continuous use.