Solid-state Biosensor Research Articles

Development of an Integrated Solid-State Urea Biosensor Based on Measurement of pH and Ammonium Ions

Development of an Integrated Solid-State Urea Biosensor Based on Measurement of pH and Ammonium Ions

Fully electronic DNA hybridization detection by a standard CMOS biochip

A novel solid-state biosensor for label-free detection of DNA hybridization is presented. The new device is realized in a standard CMOS process, thus allowing the realization of low-cost, portable, fully integrated devices. The detection mechanism is based on the field-effect of the intrinsic negative electric charge of DNA molecules which modulates the threshold voltage of a floating-gate MOS transistor. A fluid cell was developed for delivering DNA samples on the active surface of the chip. The device has an integrated, individual counter-electrode, so dry measurements are possible increasing lifetime of the chip and speeding up the experiment. Successful measurements on a first prototype of the chip, hosting 16 sensors individually addressable, are provided as proof of concept.

Solid-state urea biosensor based on the differential method

In this paper, the solid-state urea biosensor was successfully fabricated based on the differential method, which contains three parts: the SnO/sub 2//ITO glass electrode used as the pseudoreference electrode; the SnO/sub 2//ITO glass electrode used as the contrast electrode; and the urease/SnO/sub 2//ITO glass electrode used as the enzyme electrode. Correspondingly, this solid-state urea biosensor was fabricated based on the SnO/sub 2//ITO glass electrode, whose simple fabrication process reduces the cost of fabricating the solid-state biosensor. Additionally, as revealed in the experimental results, the solid-state urea biosensor has good sensing characteristics between 5 and 80 mg/dl. After fabricating a successful solid-state urea biosensor, an array sensing system was designed to enhance the precision of the solid-state urea biosensor, which comprises four parts: the biosensor system, the input buffer circuit, the differential circuit, and the weighted sum circuit. As indicated in the experimental results of the array sensing system, the sensing characteristic of the array sensing system is similar to the mean sensing characteristic from four solid-state biosensors. Therefore, the sensing signal of the solid-state urea biosensor can be averaged using the array sensing system. In summary, this study successfully investigated a solid-state urea biosensor and designed an array sensing system to increase the precision of solid-state urea biosensors.

A New Solid-State pH Sensor and Its Application in the Construction of all Solid-State Urea Biosensor

A New Solid-State pH Sensor and Its Application in the Construction of all Solid-State Urea Biosensor

Urea solid-state biosensor suitable for continuous dialysis control

A solid state potentiometric biosensor for urea determination was assembled coupling a nonactin-based ISE without an internal solution with immobilized urease. The system proved to be useful for continuous monitoring of urea during dialysis treatment using the ultrafiltrate of blood as sample. A noticeable shift of potential occurred during the dialysis (probably due to continuous extraction of ionophore by the ultrafiltrate). Therefore a flow injection analysis assembly was necessary to control the shift of electrode potential.

Organophosphorus pesticide (Paraoxon) analysis using solid state sensors

A comparison of two new solid-state biosensors for organophosphorus pesticide analysis is presented, both of which employ the inhibiting action of these toxic compounds versus the enzyme butyrylcholinesterase. The indicating sensor used was a graphite electrode, or a FET, coated with an ion-selective polymeric membrane sensitive to pH containing tridodecylamine as exchanger. The former was coupled to the enzyme butyrylcholinesterase immobilised on a functionalized nylon net, while the latter employed the same enzyme coated on the polymeric membrane by means of polyazetidine prepolymer. The responses of the two biosensors to the substrate, i.e. butyrylcholine (BuCh), and to the inhibitor, i.e. Paraoxon, one of the most common organophosphorus pesticides, were tested.

Lactate solid-state biosensor with multilayer of electrodeposited polymers for flow-injection clinical analysis

In the lactate biosensor, electrodeposited poly( o-phenylenediamine) serves as a convenient matrix for the immobilization of lactate oxidase, but does not provide sufficient discrimination from several interfering species present in physiological fluids. Their effect, however, can be eliminated by additional modification of the working Pt electrode with a bilayer of electrodeposited polypyrrole/polyphenol. Despite continued decrease in biosensor sensitivity, the newly developed three-layer solid-state biosensor was successfully applied in flow-injection determination of lactate in both undiluted and diluted human blood serum samples over a 10 day period. For the lactate concentration range 0·2−5·0 mM in several series of measurements the correlation coefficient values for comparison with photometric determination using a DuPont dimension clinical analyzer were between 0·96 and 0·99. The reproducibility measured for 1:10 diluted serum was 0·6%. The detection limit was estimated as 2 μM.

An optical biosensor based upon glucose oxidase immobilized in sol-gel silicate matrix.

Glucose oxidase immobilized in a transparent silicate gel prepared by a sol-gel method was used as a simple solid-state optical biosensor for glucose. The sensor was based upon the measurement of initial rates of reduction of the FAD prosthetic group of the enzyme in the presence of various concentrations of glucose. The analytical range of the sensor was 1-100 mM, and the measurement time was 2 min. The enzyme was considerably protected by the silicate matrix against leaching, thermal inactivation and even H2O2-dependent inactivation. The sensor was stable in daily use for 6 months.

21] Enzymatically sensitive field effect transistors

Publisher Summary Enzymatically coupled field effect transistors (ENFETs) are the only true potentiometric solid-state biosensor. They are similar to potentiometric enzyme electrodes and are subject to the same limitations in their lifetime, detection limits, sensitivity, and time response. Photolithographic encapsulation allows fabrication of ENFETs with closely defined parameters, particularly the enzyme layer thickness. This enables to model both transient and steady-state response of ENFETs with a pH-independent, one-substrate enzymatic system (penicillin) and with the more complicated, two-substrate, pH-dependent kinetics (glucose). The key assumption in the model is that the solution is well stirred so that the concentration profile on the solution side of the membrane/solution interface is flat. The excellent agreement of the theoretical model with the experiments allows extrapolating the theoretical response parameters of these sensors. Although this analysis is done for the ENFET, it is also valid for other potentiometric enzymatic sensors.