Sensors nanosensors

All AFM measurements were carried out by means of a NanoScope Ilia - Multimode (Veeco, USA). The instrument was equipped with an electrically conducting cantilever with a silicon tip (Pointprobe EFM sensor, NanoSensors, Wetzlar, Germany). An overall metallic... 

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. 

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. 

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... 

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. 

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

Bychkova and Shvarev [16] recently prepared nanosensors (0.2-20 pm) for sodium, potassium and calcium using the precipitation method. Similarly to the previous works, the plasticized poly(vinyl chloride) included a phenoxazine chro-moionophore, a lipophilic ion exchanger and a cation-selective ionophore. The dynamic range of the very selective sensors was 5 x 10 4-0.5 M for sodium, 1 x 10 5-0.1 M for potassium and 2 x 10 4 - 0.05 M for calcium. As was demonstrated by Bakker and co-workers [45] a particle caster can be used can be used for preparation of much larger beads (011 pm). 

Clark HA, Hoyer M, Philbert MA, Kopelman R (1999) Optical nanosensors for chemical analysis inside single living cells. 1. Fabrication, characterization, and methods for intracellular delivery of PEBBLE sensors. Anal Chem 71 4831 1836... 

Brasuel M, Kopelman R, Miller TJ, Tjalkens R, Philbert MA (2001) Fluorescent nanosensors for intracellular chemical analysis decyl methacrylate liquid polymer matrix and ion-exchange-based potassium PEBBLE sensors with real-time application to viable rat C6 glioma cells. Anal Chem 73 2221-2228... 

Figure 14.4 Function and properties of a QD FRET-based nanosensor. Generalized QD bioconjugate nanosensor schematic. Each QD is surrounded by an average of —10—15 protein molecules. Formation of QD-protein-analogue assembly results in quenching of the QD emission. Adding preferred analyte to the solution displaces dye-labeled analogue from the sensor assembly, resulting in an increase in direct QD emission.

Clark HA, Kopelman R, Tjalkens R, Philbert MA. Optical nanosensors for chemical analysis inside single hving cells. 2. Sensors for pH and calcium and the intracellular appbcation of PEBBLE sensors. Analytical Chemistry 1999, 71, 4837 1843. 

Sumner JP, Westerberg NM, Stoddard AK, Fierke CA, Kopelman R. Cu+- and Cu +-sensitive PEBBLE fluorescent nanosensors using DsRed as the recognition element. Sensors Actuators B-Chem. 2006 113 760-767. 

In order to demonstrate a useful intracellular nanosensor, it is crucial to show that introduction of the sensor to the cell has no detrimental effects on normal cell physiology. This final section describes an investigation of nanoshell uptake, pathway of uptake, and cellular response. 

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