Disposable Dna Biosensors Based On Screenprinted Electrodes

Recent progress in screen-printing technology with PC-controlled, fully automatic, and sophisticated instruments enabled the large-scale fabrication of the SPEs in various electrode layout designs. The printing patterns of conductors and insulators onto the surface of plastic or ceramic planar substrates can be designed and controlled by the software of these instruments. The most suitable substrate material as well as the conducting and insulating ink materials should be chosen for the purpose of the electrochemical test. The most commonly applied conducting inks are the carbon- and Au-based ones. There are mainly four steps involved in the screen-printing process. First, the conducting ink suspension is deposited onto the screen, followed by the loading of the screen mesh with the conducting ink, then the ink is forced through the screen with the help of a squeegee. Finally, the printed pattern is dried and cured. The printing of the insulating layer and the other cover layers, which can vary according to the electrochemical test, is also performed as described above onto the conducting ink-printed surface. However, the overall performance of the SPEs is greatly influenced by the chemical composition of the ink materials and the printing conditions such as applied pressure and temperature.

Screen-printed electrode is the commonly used electrode type in reports not only for clinical but also environmental and food monitoring purposes. As for the clinical applications, Lucarelli et al.[21] have recently reported carbon SPEs for the detection of SNPs related to apolipoprotein E from PCR-amplified samples. The duplex formation was detected by measuring the guanine oxidation signal. The biosensor format involved the immobilization of an inosine-substituted probe onto a SPE and the voltammetric detection of the duplex formation with the appearance of the guanine signal.

Recently, gold electrode-based indicator-free DNA hybridization detection has been reported by using a conventional-type gold electrode.[22] Figure 3 shows the oxidation signal of guanine at about ~ + 0.73 V by using differential pulse voltammetry on self-assembled L-cysteine monolayer (SAM)-modified screen-printed gold electrode (AuSPE). The electrochemical determination of hybridization between an inosine-substituted probe (Fig. 3b) and native target DNA (Fig. 3a) was accomplished. The indicator-free detection of hybridization on AuSPE is greatly advantageous over the existing carbon-based materials, because of its potential applicability to microfabrication techniques.

Indicator-free, disposable electrochemical DNA-mod-ified carbon SPEs have also been successfully applied to environmental monitoring. The device of Chiti et al.[23]

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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