Transducers, single-walled carbon nanotubes

AuNPs, magnetic nanoparticles, single-wall carbon nanotubes (SWNTs), and QDs have been used in immunosen-sors. According to the different types of transducers, immunosensors can be classified as electrochemical, mass-sensitive, and optical sensors. Some interesting examples are discussed herein. 

Novel technologies using CNTs coupled to ME have also explored in food analysis. Single-walled carbon nanotube press-transferred electrodes (SWPTEs) are new disposable electrodes where CNTs act as exclusive electrochemical transducer [54, 55], being... 

In the last 5 years, our attention has been paid to the development of novel electrochemical DNA biosensors based on carbon-based transducers as substrates for immobilization of DNA. Among others, following four electrodes exhibited the best properties for these purposes GCE (supplied by Metrohm, Herisau, Switzerland), microcrystalline natural graphite-polystyrene composite film-modified electrode (CFE), SPCE (supplied by Food Research Institute, Bratislava, Slovakia), and SPCE modified with single-walled carbon nanotubes (SWCNTs). 

In one of the representative work, Patolsky et al. [24] demonstrated the reconstitution of apo-GOx on FAD cofactor electrically contacted to the electrode via single-walled carbon nanotubes (SWCNTs), which act as conductive nanoneedles that electrically wire the enzyme redox-active site to the transducer surface (Fig. 4A). Before immobilisation, the commercially obtained SWCNTs were chemically shortened by treatment with strong acids. The formation of carboxylic (and phenolic) groups at the nanotube ends (and sidewall defect sites) as a result of acid treatment allowed the covalent immobilisation of the SWCNTs on thioethanol/ cysteamine-modified Au electrode in the presence of the coupling reagent 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) as depicted in Fig. 4A. The incorporation of 2-thioethanol in the mixed monolayer prevented... 

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