Fluorescent reporter/sensors

Their distinguishing feature is the high speed of response. This response develops on the scale of fluorescence lifetime of photophysical or photochemical events that provide the response and can be as short as 10 x-10 10 s. Because of that, the fluorescence reporting is never time-limiting, so that this limit comes from other factors, such as the rate of target - sensor mutual diffusion and the establishment of dynamic equilibrium between bound and unbound target. 

Bergamini G, Marchi E, Ceroni P (2010) Luminescent dendrimers as ligands and sensors of metal ions. In Demchenko AP (ed) Advanced fluorescence reporters in chemistry and biology. II. Springer Ser Fluoresc 8 253-284... 

The fluorescent molecular sensors will be presented with a classification according to the nature of the photoinduced process (mainly photoinduced electron or charge transfer, and excimer formation) that is responsible for photophysical changes upon cation binding. Such a classification should help the reader to understand the various effects of cation binding on the fluorescence characteristics reported in many papers. In most of these papers, little attention is often paid to the origin of cation-induced photophysical changes. 

Polyphenylene and polyfluorene have been extensively used as fluorescence-based sensors, and several chromogenic forms of these polymers have been reported. Incorporation of monomers with additional coordination sites into these polymers has led to the development of a variety of different anion sensors, mostly for halide ions (Lee et al. 2004 Zhou et al. 2005 Vetrichelvan et al. 2006 Kim et al. 2007). Extension of these materials toward recognition of more complex analytes should be possible. 

PEBBLEs are water-soluble nanoparticles based on biologically inert matrices of cross-linked polymers, typically poly(acrylamide), poly(decylmethacrylate), silica, or organically modified silicates (ORMOSILs), which encapsulate a fluorescent chemo-sensor and, often, a reference dye. These matrices have been used to make sensors for pH, metal ions, as well as for some nonionic species. The small size of the PEBBLE sensors (from 20 to 600 nm) enables their noninvasive insertion into a living cell, minimizing physical interference. The semipermeable and transparent nature of the matrix allows the analyte to interact with the indicator dye that reports the interaction via a change in the emitted fluorescence. Moreover, when compared to naked chemosensors, nanoparticles can protect the indicator from chemical interferences and minimize its toxicity. Another important feature of PEBBLEs, particularly valuable in intracellular sensing applications, is that the polymer matrix creates a separate... 

The suitability of fluorescent PET systems for use in the emerging field of molecular switching devices was pointed out in Sect. 4 due to their natural on-off action induced by ion input. Discussions in Sect. 6 have also illustrated the value of PET sensor ideas in the design of reagents and also of reporters on receptor-guest interactions. Such versatility of the fluorescent PET sensor logic makes this research worthwhile. 

A series of multifunctional anthrylboranes with up to six boron centers and divergently extended itt-conjugation have been reported. Trianthrylborane itself is bright orange, whereas the extended system (157) is dark red colored. This bathochromic shift was attributed to the more extended delocalization in the starbust oligomer (157). Two reversible reduction waves were found for the two different boron environments in (157). The anthrylboranes have also been studied as fluorescent fluoride sensors (see Section 7.2.1). 

In comparison to equivalent optical detection methods using whole cell biosensors for water toxicity detection, these results proved to be more sensitive and produce faster response time. Concentrations as low as 1% of ethanol and 1.6 ppm of phenol could be detected in less than 10 min of exposure to the toxic chemical, whilst a recent study [11] which utilized bioluminescent E.coli sensor cells, detected 0.4 M (2.35%) ethanol after 220 min. An additional study [1] based on fluorescent reporter system (GFP), enabled detection of 6% ethanol and 295 ppm phenol after more than one hour. Cha et al [12] used optical detection methods of fluorescent GFP proteins, detected 1 g of phenol per liter (1,000 ppm) and 2% ethanol after 6 hours. Other studies [13] could not be directly compared due to different material used however their time scale for chemicals identification is hours. 

Most MIP optical sensors reported in the literature utilize fluorescence as the detectable signal [215, 216]. With fluorescent analytes, the fluorescence of the MIP will increase upon binding [217, 218]. With non-fluorescent analytes, a fluorescent reporter molecule can be applied. The reporter molecule competes with or is displaced by the analyte [219-221]. Alternatively, a fluorescent monomer can be incorporated in the polymer network [222]. Upon binding of the analyte, the fluorescence of the MIP is altered. 

A fluorescence optical sensor for dansyl-L-phenylalanine has been reported [17]. In the optical sensor, the imprinted polymer was held in front of a fiber-optic device by a nylon net. Although the system worked well, there are some inherent problems that need to be addressed the... 

Other fluorescent pressure sensors have also been suggested, but are used less frequently than ruby. Wavelength calibrations with pressure have been reported for alexandrite [97,98],Sm + Y3Al50i2 (YAG) [99-101],Sm + MFCl (M = Ba,Sr) [102,103],Sm2+ SrB407 [104,105],Eu + YAG [106],Tm + YAG [107],Nd + YAIO3 [108], and V + MgO [109]. Fluorescence lifetime calibrations have also been re-... 

As a typical example, the fluorescent ion sensor reported by Silva et al. (10T8544) could be developed in an enantiomerically pure form to produce... 

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