Signaling Recognition Events with Fluorescent Sensors and Switches.

基礎講座 電気泳動(Electrophoresis)

Temperature (T) is probably the most fundamental parameter in all kinds of science. Respective sensors are widely used in daily life. Besides conventional thermometers, optical sensors are considered to be attractive alternatives for sensing and on-line monitoring of T. This Review article focuses on all kinds of luminescent probes and sensors for measurement of T, and summarizes the recent progress in their design and application formats. The introduction covers the importance of optical probes for T, the origin of their T-dependent spectra, and the various detection modes. This is followed by a survey on (a) molecular probes, (b) nanomaterials, and (c) bulk materials for sensing T. This section will be completed by a discussion of (d) polymeric matrices for immobilizing T-sensitive probes and (e) an overview of the various application formats of T-sensors. The review ends with a discussion on the prospects, challenges, and new directions in the design of optical T-sensitive probes and sensors.

Luminescent probes and sensors for temperature.

Non-invasive precise thermometers working at the nanoscale with high spatial resolution, where the conventional methods are ineffective, have emerged over the last couple of years as a very active field of research. This has been strongly stimulated by the numerous challenging requests arising from nanotechnology and biomedicine. This critical review offers a general overview of recent examples of luminescent and non-luminescent thermometers working at nanometric scale. Luminescent thermometers encompass organic dyes, QDs and Ln3+ions as thermal probes, as well as more complex thermometric systems formed by polymer and organic–inorganic hybrid matrices encapsulating these emitting centres. Non-luminescent thermometers comprise of scanning thermal microscopy, nanolithography thermometry, carbon nanotube thermometry and biomaterials thermometry. Emphasis has been put on ratiometric examples reporting spatial resolution lower than 1 micron, as, for instance, intracellular thermometers based on organic dyes, thermoresponsive polymers, mesoporous silica NPs, QDs, and Ln3+-based up-converting NPs and β-diketonate complexes. Finally, we discuss the challenges and opportunities in the development for highly sensitive ratiometric thermometers operating at the physiological temperature range with submicron spatial resolution.

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Thermometry at the nanoscale

Luminescent sensors and switches in the early 21st century

We illustrate a general polymeric design of fluorescent logic gates, for example, AND, using temperature and pH as inputs.

Fluorescent polymeric AND logic gate with temperature and pH as inputs.

Poly(N-isopropylacrylamide) in aqueous solution undergoes a phase transition at ∼32 °C. The fluorescence properties of benzofurazans are affected by solvent polarity. We combine these two characteristics for the first time to develop sensitive fluorescent molecular thermometers. Five fluorescent monomers having a benzofurazan skeleton were synthesized, and the copolymers of N-isopropylacrylamide (NIPAM) and a small quantity of the fluorescent monomer were obtained to investigate their fluorescence properties. With increase in temperature, the copolymers in water showed the temperature-induced phase transition at ∼32 °C and the fluorescence intensities of the copolymers concurrently increased. Especially, for the copolymer of 4-N-(2-acryloyloxyethyl)-N-methylamino-7-N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole and NIPAM, the fluorescence intensity at 37 °C was 13.3-fold that seen at 29 °C. The sensitive range of temperature of these fluorescent molecular thermometers is changed by the replacement of the ...

Fluorescent molecular thermometers based on polymers showing temperature-induced phase transitions and labeled with polarity-responsive benzofurazans.

Fluorescent molecular thermometers based on thermo-responsive linear polymer molecules such as poly(N-isopropylacrylamide)
				(PNIPAM) labelled with a polarity-responsive fluorescent molecule benzofurazan (BD) are the most sensitive known. Thermo-responsive PNIPAM and some related polymer microgel particles labelled with BD by emulsion polymerization have been prepared and their fluorescence properties in water as fluorescent thermometers studied. All the cross-linked polymer microgel particles dispersed in water fluoresce strongly as soon as each threshold temperature is exceeded. The nine kinds of microgel dispersion developed in this work thoroughly cover the sensitivity range from 18 to 47 °C. They are not only more sensitive than the previous fluorescent molecular thermometers based on other principles but also highly reproducible in their behaviour.

Development of fluorescent microgel thermometers based on thermo-responsive polymers and their modulation of sensitivity range

Molecular computation is fashionable because of the small device sizes that should be possible. For instance, information processing in nanospaces is widespread in biology. However, experimental cases with computing molecules occupy rather large volumes until now (ca. 1012 nm3). Now we demonstrate small-scale computation using a designed logic gate in spheres of 3 nm radius (volume = ca. 102 nm3) which are produced by detergent micelles. The logic gate accommodated in the small nanospace fluoresces only when both H+ and Na+ ions are available.

Membrane media create small nanospaces for molecular computation.

Fluorescent molecular thermometers based on polymers showing a temperature-induced phase transition and labeled with polarity-sensitive fluorescent benzofurazans are the most sensitive known. Here we show a simple and effective method for modulating the sensitive temperature ranges of fluorescent molecular thermometers based on such temperature-responsive polymers. 4-N-(2-Acryloyloxyethyl)-N-methylamino-7-N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole was adopted as a polarity-sensitive fluorescent benzofurazan, and nine copolymers of two kinds of acrylamide derivative (N-n-propylacrylamide, N-isopropylacrylamide, and/or N-isopropylmethacrylamide) with a small amount of DBD-AE were obtained. The fluorescence intensities of these copolymers in aqueous solution sharply increased with increasing temperature over a small range (6−7 °C). In contrast, these fluorescent molecular thermometers differed from one another in the sensitive temperature range (between 20 and 49 °C). Moreover, the sensitive temperature ...

Kaoru Iwai

Papers

Fluorescent polymeric AND logic gate with temperature and pH as inputs.

Fluorescent molecular thermometers based on polymers showing temperature-induced phase transitions and labeled with polarity-responsive benzofurazans.

Development of fluorescent microgel thermometers based on thermo-responsive polymers and their modulation of sensitivity range

Membrane media create small nanospaces for molecular computation.

Modulation of the sensitive temperature range of fluorescent molecular thermometers based on thermoresponsive polymers.