Nanosensor

Their great strength and conductivity have led to the use of nanotubes in submicroscopic electronic components such as transistors. The rigidity of nanotubes may also allow them to be used as minute molds for other elements. For example, they can be filled with molten lead to create lead wires one atom in diameter and can serve as tiny test tubes that hold individual molecules in place. Nanotubes that are filled with biomolecules such as cytochrome c hold the promise of acting as nanosensors for medical applications. 

With the complex where L = pyridine an optical nanosensor was developed [135-137], the method used to fix the vapochromic material to the optical fiber was the electrostatic self assembling method (ESA) and the light source used was an 850 nm LED. The sensor was tested for two different alcohols (ethanol and methanol) and it was possible to distinguish between different concentrations. It was also possible to discriminate between the two different alcohols. 

Volatile alcoholic compounds fiber optic nanosensor. Sensors and Actuators B, 115, 444- 9. 

All the STM results from our group presented in this chapter employed the variable temperature STM, with tips made by electrochemical etching of tungsten wire. For noncontact AFM (NC-AFM), we employ commercial conducting silicon cantilevers with force constants of approximately 2-14 rn 1 and resonant frequencies of approximately 60-350kHz (Nanosensors and Mikromasch). The NC-AFM images we present here were recorded in collaboration with Professor Onishi at Kobe University and employed a UHV JEOL (JSPM-4500A) microscope. 

Beyond protein-protein interactions—development and use of FRET-based nanosensors... 

FRET-based nanosensors have been successfully used to monitor steady state levels of metabolites, nutrients, and ions in mammalian cells [74, 87], Recently FRET-based glucose, sucrose, and amino acid nanosensors have been developed to study the metabolism of glucose, sucrose, and amino acid uptake and metabolism in plant cells [80,89, 91]. The enormous potential of these nanosensors will be crucial for understanding ion (e.g., calcium), metabolite (e.g., sugars), hormone (e.g., auxins, gibberellins etc.), and nutrient (e.g., nitrogen, potassium, phosphorus) requirements and homeostasis in living plant tissues. 

Fehr, M., Frommer, W. B. and Lalonde, S. (2002). Visualization of maltose uptake in living yeast cells by fluorescent nanosensors. Proc. Natl. Acad. Sci. USA 99, 9846-51. 

Fehr, M., Takanaga, H., Ehrhardt, D. W. and Frommer, W. B. (2005b). Evidence for high-capacity bidirectional glucose transport across the endoplasmic reticulum membrane by genetically encoded fluorescence resonance energy transfer nanosensors. Mol. Cell. Biol. 25, 11102-12. 

Deuschle, K., Chaudhuri, B., Okumoto, S., Lager, I., Lalonde, S. and Frommer, W. B. (2006). Rapid metabolism of glucose detected with FRET glucose nanosensors in epidermal cells and intact roots of Arabi-dopsis RNA-silencing mutants. Plant Cell 18, 2314-25. 

Kopelman et al.73 have prepared fiber optic sensors that are selective for nitric oxide and do not respond to most potential interferents. Both micro-and nanosensors have been prepared, and their response is fast (<1 s), reversible, and linear up to 1 mM concentrations of nitric oxide. The respective "chemistry" at the fiber tip was contacted with the sample, light was guided to the sample through the microfiber, and emitted light was collected by a microscope (without the use of fibers, however). 

Petersons pH probe also was modified in order to give a miniature fiber optic sensor potentially suitable for glucose measurements90. Kopelman et al.91 developed a fiber-optic pH nanosensor for physiological measurements using a dual-emission sensitive dye. The performance of a pH sensor was reported92. An unclad fiber was dip-coated with a thin layer of porous cladding within which a pH-sensitive dye was entrapped. The fundamental... 

Clark H.A., Kopelman R., Tjalkens R., Philbert M.A., Optical Nanosensors for Chemical Analysis inside Single Living Cells. 1. Fabrication, Characterization, and Methods for Intracellular Delivery of PEBBLE Sensors, Anal. Chem. 1999 71 4831— 4836. 

FIGURE 1.2 Illustration of WPI s ISO-NOPNM lOOnm combination NO nanosensor. (Reprinted with permission from Elsevier Publishing [45].)... 

FIGURE 1.5 Amperometric response of an NO nanosensor upon addition of lOOnM NO and lpM oxyhemoglobin to a stirred 0.1 M phosphate buffer solution (pH 7.4). 

Y. Cui, Q. Wei, H. Park, and C.M. Lieber, Nanowire nanosensors for highly sensitive and selective detection of biological and chemical species. Science 293, 1289-1292 (2001). 

X. Zhang, J. Wang, B. Ogorevc, and U.E. Spichiger, Glucose nanosensor based on Prussian-blue modified carbon-fiber cone nanoelectrode and an integrated reference electrode. Electroanalysis 11, 945-949 (1999). 

Hahm, J.-i. Lieber, C. M. 2004. Direct ultrasensitive electrical detection of DNA and DNA sequence variations using nanowire nanosensors. Nano Lett. 4 51-54. 

It is often desirable to immobilize different biomolecules on different sensing elements in close proximity on the same nanophotonic sensor in the development of a multiplexed sensor. This is the case in the example of parallel ID photonic crystal resonators described in Sect. 16.4. Cross-contamination of biomolecules must be avoided in order to preserve high specificity. We have found that a combination of parylene biopatteming and polydimethylsiloxane (PDMS) microfluidics is a convenient means to immobilized multiple biomolecules in close proximity without cross-contamination as shown in Fig. 16.8. Parylene biopatteming is first used to expose only the regions of highest optical intensity of the nanosensor for functionalization. Second, a set of PDMS microfluidics is applied to the parylene-pattemed nanophotonic sensor, and the biomolecules to be attached... 

Nanoscale oxides, as fillers, 11 316 Nanosecond excitation pulses, 14 619 Nanosensors, 17 64 Nanostrip, 18 406... 

Montalti M, Prodi L, Zaccheroni N (2005) Fluorescence quenching amplification in silica nanosensors for metal ions. J Mater Chem 15 2810-2814... 

Riu J, Maroto A, Rius FX (2006) Nanosensors in environmental analysis. Talanta 69 288-301... 

Some bead materials possess porous structure and, therefore, have very high surface to volume ratio. The examples include silica-gel, controlled pore glass, and zeolite beads. These inorganic materials are made use of to design gas sensors. Indicators are usually adsorbed on the surface and the beads are then dispersed in a permeation-selective membrane (usually silicone rubbers). Such sensors possess high sensitivity to oxygen and a fast response in the gas phase but can be rather slow in the aqueous phase since the gas contained in the pores needs to be exchanged. Porous polymeric materials are rarer and have not been used so far in optical nanosensors. 

Dye-doped polymeric beads are commonly employed in different formats (Fig. 5), namely as water-dispersible nanosensors, labels and in composite materials (DLR-referenced and multianalyte sensors, sensor arrays, magnetic materials, etc.). The sensing properties of the dye-doped beads are of little or no relevance in some more specific materials, e.g., the beads intended for photodynamic therapy (PDT). The different formats and applications of the beads will be discussed in more detail in the following section, and the relative examples of sensing materials will be given. 

These are introduced directly into the analyzed medium or even into the cells to measure analytical parameters there. Compared to dissolved indicators nanosensors are usually significantly less toxic and are less prone to interferences and quenching. On the other hand, similarly to the dissolved indicators, nanosensors... 

Similarly to bulk oxygen sensors, optical nanosensors rely on dynamic quenching of luminescence. Numerous indicators and polymeric materials were found suitable... 

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