Precise Proton Mapping near Ionic Micellar Membranes with Fluorescent Photoinduced-Electron-Transfer Sensors

One of the challenges for fluorescent sensors is to reduce their target environment size from a micrometer scale, such as biological cells, to a nanometer scale. Proton maps near membranes are of importance in bioenergetics and are the first goal in nanometer-scale analysis with fluorescent sensors. Thirty-three fluorescent photoinduced-electron-transfer pH sensors bearing an environment-sensitive benzofurazan fluorophore and having different hydrophobicity/hydrophilicity and hydrogen-bonding abilities were prepared. These sensors were scattered in nanospaces associated with anionic and cationic micelles as model membranes to indicate proton availability and polarity in local spaces. Gathering the data from the sensors allowed the successful drawing of proton maps near anionic and cationic micelles, in which electrostatic attraction/repulsion of protons by the charged head groups of micelles and dielectric suppression of protons were clearly observed.     

Micro- and nanomechanical sensors for environmental, chemical, and biological detection

Micro- and nanoelectromechanical systems, including cantilevers and other small scale structures, have been studied for sensor applications. Accurate sensing of gaseous or aqueous environments, chemical vapors, and biomolecules have been demonstrated using a variety of these devices that undergo static deflections or shifts in resonant frequency upon analyte binding. In particular, biological detection of viruses, antigens, DNA, and other proteins is of great interest. While the majority of currently used detection schemes are reliant on biomarkers, such as fluorescent labels, time, effort, and chemical activity could be saved by developing an ultrasensitive method of label-free mass detection. Micro- and nanoscale sensors have been effectively applied as label-free detectors. In the following, we review the technologies and recent developments in the field of micro- and nanoelectromechanical sensors with particular emphasis on their application as biological sensors and recent work towards integrating these sensors in microfluidic systems.     

Liquid polymer nano-PEBBLEs for Cl- analysis and biological applications

The first nanometer scale anion sensing fluorescent spherical nanosensors, or PEBBLEs (probes encapsulated by biologically localized embedding) have been developed for the intracellular monitoring of chloride. The general scheme for the polymerization and introduction of sensing components creates a matrix that allows for the utilization of the highly selective ionophores used in poly(vinyl chloride) and poly(decyl methacrylate) ion-selective electrodes. We have demonstrated that our previously developed scheme for cation sensors can be utilized to tailoring selective submicron sensors for use in intracellular measurements of biologically relevant anions for which selective enough fluorescent probes do not exist. Three schemes were attempted for the development of chloride sensitive PEBBLEs. The first two used the Chloride ionophore indium(III) octaethylporphyrin chloride (In(OEP)Cl) (1) as an ionophore working in tandem with a chromoionophore and (2) as a chromoionophore with a peak shift generated by chloride mediated breaking of hydroxide ion-bridged porphyrin dimer. The third method used the optically silent Chloride ionophore III (ETH 9033) working in tandem with chromoionophore III (ETH 5350) to indirectly monitor Cl- activity by reporting the H+ coextracted into the matrix. Method 3 gave the most promising results, at a pH of 7.2 these PEBBLEs have a limit of detection of 0.2 mM Cl- with a linear dynamic range of 0.4 mM-190 mM Cl-. These PEBBLEs were delivered into C6 glioma cells, utilizing a gene gun, and intracellular chloride levels were monitored during ion-channel stimulation by kainic acid.     

Recent progress in fluorescent and colorimetric sensors for the detection of ions and biomolecules

Optical sensors are widely used in the field of analytical sensing and optical imaging because of their high sensitivity, fast response time, and technical simplicity. This review focuses on recent contributions concerning the ions, neutral molecules and especially tumor micro-environment-related parameters based fluorescent or colorimetric sensors and is organized according to their target classifications.     

Sol-gel-derived micron scale optical fibers for chemical sensing

We report for the first time on the preparation of organically-doped room temperature processed sol-gel-derived micron scale optical fibers as platforms for chemical- and bio-sensors. Micron scale optical fibers are drawn from fluorescent dye-doped tetraethoxysilane (TEOS)-derived sol-gel solution processed under ambient conditions. Such a simple methodology to entrap organic and even bioactive species within the optical fiber offers many advantages over more conventional ways of immobilizing organic probes for the development of optical sensors. Specifically, we report on the photophysical properties of fluorescein (a pH sensitive fluorescent dye) and rhodamine 6G (R6G; laser dye) entrapped within sol-gel-derived optical fibers. We present the preliminary results on the viability of such doped optical fibers for chemical sensing. Our results demonstrate that a fluorescein-doped sol-gel-derived optical fiber responds to ammonia and acid vapors with a response time of 1–2 seconds.     

香豆素类荧光传感器

荧光传感器能够将分子识别的信息转换成荧光信号,荧光法在灵敏度、选择性和实时原位检测等方面优势突出。实时检测被分析物的水平已引起包括化学家、生物学家、临床生物化学家和环境学家的极大兴趣。以香豆素为基础的荧光传感器近年来已成为一个新兴的研究热点。本文综述了香豆素类荧光传感器在阳离子、阴离子、中性分子识别检测中的分子设计、作用机理和应用效果,展望了该领域的发展方向。     

手性荧光传感器的研究进展

随着手性化合物在制药、不对称合成、生物科学及临床医学等领域应用的增长,迫切需要发展一种快速、灵敏的对映异构体检测技术。手性荧光传感器引起了人们的高度关注。近年来,发展了很多手性荧光传感器并对手性化合物表现出较高的选择性和灵敏度。该文综述了以1,1'-联-2-萘酚衍生物、杯芳烃衍生物、高分子聚合物、纳米材料、金属有机多孔材料为骨架的手性荧光传感器,总结了其在手性化合物识别中的应用,并展望了手性荧光传感器的发展方向。     

Enantioselective recognition of mandelic acid by a 3,6-dithiophen-2-yl-9H-carbazole-based chiral fluorescent bisboronic acid sensor

We have prepared chiral fluorescent bisboronic acid sensors with 3,6-dithiophen-2-yl-9H-carbazole as the fluorophore. The thiophene moiety was used to extend the π-conjugation framework of the fluorophore in order to red-shift the fluorescence emission and, at the same time, to enhance the novel process where the fluorophore serves as the electron donor of the photoinduced electron transfer process (d-PET) of the boronic acid sensors; i.e., the background fluorescence of the sensor 1 at acidic pH is weaker compared to that at neutral or basic pH, in stark contrast to the typical a-PET boronic acid sensors (where the fluorophore serves as the electron acceptor of the photoinduced electron transfer process). The benefit of the d-PET boronic acid sensors is that the recognition of the hydroxylic acids can be achieved at acidic pH. We found that the thiophene moiety is an efficient π-conjugation linker and electron donor; as a result, the d-PET contrast ratio of the sensors upon variation of the pH is improved 10-fold when compared to the previously reported d-PET sensors without the thiophene moiety. Enantioselective recognition of tartaric acid was achieved at acid pH, and the enantioselectivity (total response K(D)I(F)(D)/K(L)I(F)(L)) is 3.3. The fluorescence enhancement (I(F)(Sample)/I(F)(Blank)) of sensor 1 upon binding with tartaric acid is 3.5-fold at pH 3.0. With the fluorescent bisboronic acid sensor 1, enantioselective recognition of mandelic acid was achieved for the first time. To the best of our knowledge, this is the first time that the mandelic acid has been enantioselectively recognized using a chiral fluorescent boronic acid sensor. Chiral monoboronic acid sensor 2 and bisboronic acid sensor 3 without the thiophene moiety failed to enantioselectively recognize mandelic acid. Our findings with the thiophene-incorporated boronic acid sensors will be important for the design of d-PET fluorescent sensors for the enantioselective recognition of α-hydroxylic acids such as mandelic acid, given that it is currently a challenge to recognize these analytes with boronic acid fluorescent molecular sensors.     

液相爆炸物荧光化学传感器研究进展

溶液中爆炸物的快速灵敏检测对于防恐、反恐和环境质量监测等都具有十分重要的意义。本文在介绍液相爆炸物探测用均相荧光传感器、薄膜荧光传感器和颗粒荧光传感器的基础上,简要评述了各种方法的优缺点,指出新型化学薄膜荧光传感器的开发和基于这些薄膜的低成本、多功能和高品质液相专用爆炸物探测仪的研制将成为未来液相爆炸物探测研究的一个重...     

硼-二吡咯亚甲基染料类分子荧光传感器

分子荧光传感器以其灵敏度高、使用方便等优点备受人们的关注，近年来得到了迅速的发展。本文介绍了分子荧光传感器的构成、分类、传感机制以及设计原理,重点介绍了基于硼-二吡咯亚甲基(BDP)染料类分子荧光传感器的制备、识别机理和应用展望。     

Turning fluorescent dyes into Cu(II) nanosensors

There is great interest in the self-organization of the proper subunits as a new strategy for the realization of fluorescent chemosensors. In this article, it is shown that commercially available fluorescent dyes, functionalized with triethoxysilane moieties, can be converted into fluorescent chemosensors by simple inclusion into silica nanostructures. Dye-doped silica nanoparticles and thin films detect Cu(II) ions in the micromolar range by the quenching of fluorescence emission. The different response toward Zn(II), Ni(II), and Co(II) metal ions was also investigated and is reported. The self-organization of the silica structures leads, at the same time, to the formation of metal ion binding sites as well as to the linking of a fluorescent reporter in their proximity. Structural features of the materials, particularly particle size and network porosity, strongly affect their ability to act as fluorescent sensors.     

Targetable fluorescent sensors for advanced cell function analysis

Chemistry-based bioimaging techniques have contributed to the elucidation of intracellular physiological events. During the last few decades, many fluorescent sensors have been developed and used in live cell experiments. Owing to immense efforts by numerous research groups, several strategies have been developed to design fluorescent sensors based on various components such as small molecules and fluorescent proteins. Recently, site-specific targeting of fluorescent sensors has attracted increasing attention. Strategies for fluorescent sensor targeting were surveyed in this review with the aims to expand current knowledge on chemistry-based bioimaging and aid in the emergence of related innovative technologies. The first discussed strategy is based on the intrinsic properties of small molecules for localization at specific organelles, such as mitochondria, nuclei, and lysosomes. As a further elaboration of the topic, our recent study about in vivo targeting of pH sensors was briefly introduced. The second strategy exploits genetically encoded tags and their specific ligands. Here, fluorescent sensors with commercially available tags and corresponding ligands were mainly reviewed. As the final topic, our original protein labeling technique, which enables fluorogenic labeling as an advanced technology, was introduced.     

A unique approach to development of near-infrared fluorescent sensors for in vivo imaging

Near-infrared (NIR) fluorescent sensors have emerged as promising molecular tools for imaging biomolecules in living systems. However, NIR fluorescent sensors are very challenging to be developed. Herein, we describe the discovery of a new class of NIR fluorescent dyes represented by 1a/1c/1e, which are superior to the traditional 7-hydroxycoumarin and fluorescein with both absorption and emission in the NIR region while retaining an optically tunable hydroxyl group. Quantum chemical calculations with the B3LYP exchange functional employing 6-31G(d) basis sets provide insights into the optical property distinctions between 1a/1c/1e and their alkoxy derivatives. The unique optical properties of the new type of fluorescent dyes can be exploited as a useful strategy for development of NIR fluorescent sensors. Employing this strategy, two different types of NIR fluorescent sensors, NIR-H(2)O(2) and NIR-thiol, for H(2)O(2) and thiols, respectively, were constructed. These novel sensors respond to H(2)O(2) or thiols with a large turn-on NIR fluorescence signal upon excitation in the NIR region. Furthermore, NIR-H(2)O(2) and NIR-thiol are capable of imaging endogenously produced H(2)O(2) and thiols, respectively, not only in living cells but also in living mice, demonstrating the value of the new NIR fluorescent sensor design strategy. The new type of NIR dyes presented herein may open up new opportunities for the development of NIR fluorescent sensors based on the hydroxyl functionalized reactive sites for biological imaging applications in living animals.     

Rapid exchange luminescence: nitroxide quenching and implications for sensor applications

The quenching of terbium emission in the sensitized complex Tb3+-cs124-DTPA by nitroxide radical TEMPO derivatives in aqueous solutions has been studied with time-averaged and time-resolved methods. The time-resolved results show more quenching than the time-averaged values, opposite to the behavior expected for static quenching. A rapid exchange model with a slightly fluorescent fluorophore/quencher complex is proposed. Due to the long time scale of Tb3+ emission, dynamical averaging must be considered in the interpretation of experiments. The rapid exchange limit is shown to be consistent with the present results. The utility of these observations in the design of sensors that are not limited by a background level is noted.     

9-Aryl-1,2-dihydropyrrolo[3,4-b]indolizin-3-one (Seoul-Fluor) as a smart platform for colorful ratiometric fluorescent pH sensors

In this communication, we report that 9-aryl-1,2-dihydropyrrolo[3,4-b]indolizin-3-one (Seoul-Fluor) can serve as a potential platform for colorful ratiometric fluorescent pH sensors by simple incorporation of pH responsive elements on Seoul-Fluor. Seoul-Fluor-based fluorescent pH sensors allow the emission- and pH-tuning ability upon protonation by varying their pK(a) values and electronic characteristics of substituents by a rational design.     

Nanoengineered glycan sensors enabling native glycoprofiling for medicinal applications: towards profiling glycoproteins without labeling or liberation steps

Nanoengineered glycan sensors may help realize the long-held goal of accurate and rapid glycoprotein profiling without labeling or glycan liberation steps. Current methods of profiling oligosaccharides displayed on protein surfaces, such as liquid chromatography, mass spectrometry, capillary electrophoresis, and microarray methods, are limited by sample pretreatment and quantitative accuracy. Microarrayed platforms can be improved with methods that better estimate kinetic parameters rather than simply reporting relative binding information. These quantitative glycan sensors are enabled by an emerging class of nanoengineered materials that differ in their mode of signal transduction from traditional methods. Platforms that respond to mass changes include a quartz crystal microbalance and cantilever sensors. Electronic response can be detected from electrochemical, field effect transistor, and pore impedance sensors. Optical methods include fluorescent frontal affinity chromatography, surface plasmon resonance methods, and fluorescent carbon nanotubes. After a very brief primer on glycobiology and its connection to medicine, these emerging systems are critically reviewed for their potential use as core sensors in future glycoprofiling tools.     

喹啉衍生物锌离子荧光传感器*

本文综述了近年来用于锌离子检测的喹啉衍生物荧光传感器的研究进展,介绍了基于喹啉、8-羟基喹啉和8-氨基喹啉合成的锌离子荧光传感器的结构和设计原理,概述了锌离子对喹啉衍生物荧光传感器光学性能的影响,分析了喹啉衍生物锌离子荧光传感器在检测过程中的优点及其实际应用价值,并展望了这类锌离子荧光传感器的研究和发展方向。     

Building fluorescent sensors by template polymerization: the preparation of a fluorescent sensor for D-fructose

[formula: see text] The application of molecular imprinting in making fluorescent sensors has been hampered by the lack of suitable fluorescent tags, which would respond to the binding event with significant fluorescence intensity changes. We have designed and synthesized a fluorescent monomer which allows for the preparation of fluorescent sensors of cis diols using molecular imprinting methods. This monomer was used for the preparation of sensitive fluorescent sensors for D-fructose.     

Fluorescent and colorimetric sensors for detection of lead, cadmium, and mercury ions

Exposure to even very low levels of lead, cadmium, and mercury ions is known to cause neurological, reproductive, cardiovascular, and developmental disorders, which are more serious problems for children particularly. Accordingly, great efforts have been devoted to the development of fluorescent and colorimetric sensors, which can selectively detect lead, cadmium, and mercury ions. In this critical review, the fluorescent and colorimetric sensors are classified according to their receptors into several categories, including small molecule based sensors, calixarene based chemosensors, BODIPY based chemosensors, polymer based chemosensors, DNA functionalized sensing systems, protein based sensing systems and nanoparticle based sensing systems (197 references).     

A New Trend on Biosensor for Neurotransmitter Choline/Acetylcholine—an Overview

Technology always has been an indispensible part in the development of biosensors. The performance of biosensors is being tremendously improved using new materials as transducer as well as binding material in their construction. The use of new materials allowed innovation on transduction technology in biosensor preparations. Because of the submicron dimensions of these sensors, simple and rapid analyses in vitro as well as in vivo are now possible. Portable instruments capable of analysing multiple components are becoming available, too. Sensors that provide excellent temporal and spatial resolution for in vivo monitoring such as for measurement of neurotransmitters have become prominent. The interest to improve the stability, sensitivity and selectivity of the sensors is paramount. This study tries to give an overview of the present status of the material-based biosensor design and new generation of choline/acetylcholine neurotransmitter biosensors.