Yuming Yang,†,§ Qiang Zhao,‡,§ Wei Feng,† and Fuyou Li*,† †Department of Chemistry and State Key Laboratory of Molecular Engineering of Polymers and Institutes of Biomedical Sciences, Fudan University, Shanghai 200433, P. R. China ‡Key Laboratory for Organic Electronics and Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, Nanjing 210046, P. R. China.

Luminescent chemodosimeters for bioimaging.

The long wavelength (far-red to NIR) analyte-responsive fluorescent probes are advantageous for in vivo bioimaging because of minimum photo-damage to biological samples, deep tissue penetration, and minimum interference from background auto-fluorescence by biomolecules in the living systems. Thus, great interest in the development of new long wavelength analyte-responsive fluorescent probes has emerged in recent years. This review highlights the advances in the development of far-red to NIR fluorescent probes since 2000, and the probes are classified according to their organic dye platforms into various categories, including cyanines, rhodamine analogues, BODIPYs, squaraines, and other types (240 references).

Far-red to near infrared analyte-responsive fluorescent probes based on organic fluorophore platforms for fluorescence imaging

Design strategies for water-soluble small molecular chromogenic and fluorogenic probes.

Near-infrared (NIR) fluorescent dyes have emerged as promising modalities for monitoring the levels of various biologically relevant species in cells and organisms. The use of NIR probes enables deep photon penetration in tissue, minimizes photo-damage to biological samples, and produces low background auto-fluorescence from biomolecules present in living systems. The number of new analyte-responsive NIR fluorescent probes has increased substantially in recent years as a consequence of intense research efforts. In this tutorial review, we highlight recent advances (2010–2013) made in the development and applications of NIR fluorescent probes. The review focuses on NIR fluorescent probes that have been devised to sense various biologically important species, including ROS/RNS, metal ions, anions, enzymes and other related species, as well as intracellular pH changes. The basic principles involved in the design of functional NIR fluorescent probes and suggestions about how to expand applications of NIR imaging agents are also described.

Recent progress in the development of near-infrared fluorescent probes for bioimaging applications

Fluorescent chemosensors for ions and neutral analytes have been widely applied in many diverse fields such as biology, physiology, pharmacology, and environmental sciences. The field of fluorescent chemosensors has been in existence for about 150 years. In this time, a large range of fluorescent chemosensors have been established for the detection of biologically and/or environmentally important species. Despite the progress made in this field, several problems and challenges still exist. This tutorial review introduces the history and provides a general overview of the development in the research of fluorescent sensors, often referred to as chemosensors. This will be achieved by highlighting some pioneering and representative works from about 40 groups in the world that have made substantial contributions to this field. The basic principles involved in the design of chemosensors for specific analytes, problems and challenges in the field as well as possible future research directions are covered. The application of chemosensors in various established and emerging biotechnologies, is very bright.

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Fluorescent chemosensors: The past, present and future

Fluorescence imaging has emerged as a powerful tool for monitoring biomolecules within the context of living systems with high spatial and temporal resolution. Researchers have constructed a large number of synthetic intensity-based fluorescent probes for bio-imaging. However, intensity-based fluorescent probes have some limitations: variations in probe concentration, probe environment, and excitation intensity may influence the fluorescence intensity measurements. In principle, the use of ratiometric fluorescent probes can alleviate this shortcoming. Forster resonance energy transfer (FRET) is one of the most widely used sensing mechanisms for ratiometric fluorescent probes. However, the development of synthetic FRET probes with favorable photophysical properties that are also suitable for biological imaging applications remains challenging. In this Account, we review the rational design and biological applications of synthetic FRET probes, focusing primarily on studies from our laboratory. To construct useful FRET probes, it is a pre-requisite to develop a FRET platform with favorable photophysical properties. The design criteria of a FRET platform include (1) well-resolved absorption spectra of the donor and acceptor, (2) well-separated emission spectra of the donor and acceptor, (3) donors and acceptors with comparable brightness, (4) rigid linkers, and (5) near-perfect efficiency in energy transfer. With an efficient FRET platform in hand, it is then necessary to modulate the donor-acceptor distance or spectral overlap integral in an analyte-dependent fashion for development of FRET probes. Herein, we emphasize our most recent progress on the development of FRET probes by spectral overlap integral, in particular by changing the molar absorption coefficient of the donor dyes such as rhodamine dyes, which undergo unique changes in the absorption profiles during the ring-opening and -closing processes. Although partial success has been obtained in design of first-generation rhodamine-based FRET probes via modulation of acceptor molar absorption coefficient, further improvements in terms of versatility, sensitivity, and synthetic accessibility are required. To address these issues with the first-generation rhodamine-based FRET probes, we have proposed a strategy for the design of second-generation probes. As a demonstration, we have developed FRET imaging probes for diverse targets including Cu²⁺, NO, HOCl, cysteine, and H₂O₂. This discussion of the methods for successfully designing synthetic FRET probes underscores the rational basis for further development of new FRET probes as a molecular toolbox for probing and manipulating a wide variety of biomolecules in living systems.

FRET-based small-molecule fluorescent probes: rational design and bioimaging applications.

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-H2O2 and NIR-thiol, for H2O2 and thiols, respectively, were constructed. These novel sensors respond to H2O2 or thiols with a...

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

Hydrogen peroxide (H(2)O(2)) acts as a signaling molecule in a wide variety of signaling transduction processes and an oxidative stress marker in aging and disease However, excessive H(2)O(2) production is implicated with various diseases Nitric oxide (NO) serves as a secondary messenger inducing vascular smooth muscle relaxation However, mis-regulation of NO production is associated with various disorders To disentangle the complicated inter-relationship between H(2)O(2) and NO in the signal transduction and oxidative pathways, fluorescent reporters that are able to display distinct signals to H(2)O(2), NO, and H(2)O(2)/NO are highly valuable Herein, we present the rational design, synthesis, spectral properties, and living cell imaging studies of FP-H(2)O(2)-NO, the first single-fluorescent molecule, that can respond to H(2)O(2), NO, and H(2)O(2)/NO with three different sets of fluorescence signals FP-H(2)O(2)-NO senses H(2)O(2), NO, and H(2)O(2)/NO with a fluorescence signal pattern of blue-black-black, black-black-red, and black-red-red, respectively Significantly, we have further demonstrated that FP-H(2)O(2)-NO, a single fluorescent probe, is capable of simultaneously monitoring endogenously produced NO and H(2)O(2) in living macrophage cells in multicolor imaging We envision that FP-H(2)O(2)-NO will be a unique molecular tool to investigate the interplaying roles of H(2)O(2) and NO in the complex interaction networks of the signal transduction and oxidative pathways In addition, this work establishes a robust strategy for monitoring the multiple ROS and RNS species (H(2)O(2), NO, and H(2)O(2)/NO) using a single fluorescent probe, and the modularity of the strategy may allow it to be extended for other types of biomolecules

Single fluorescent probe responds to H2O2, NO, and H2O2/NO with three different sets of fluorescence signals

A new NIR fluorescent probe for monitoring hydrazine in blood samples and live cells was designed and synthesized.

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Development of a near-infrared fluorescent probe for monitoring hydrazine in serum and living cells

Based on a novel coumarin-quinolinium platform, probe 2 was rationally designed and synthesized as a novel ratiometric fluorescent sensor for sulfite anions. The probe exhibited a wide dynamic concentration range for sulfite anions in a PBS buffer (containing 1 mg mL−1 BSA). More importantly, the probe was suitable for ratiometric fluorescence imaging in living cells with high sensitivity, favorable selectivity, and minimal cytotoxicity.

Sasa Zhu

Papers

FRET-based small-molecule fluorescent probes: rational design and bioimaging applications.

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

Single fluorescent probe responds to H2O2, NO, and H2O2/NO with three different sets of fluorescence signals

Development of a near-infrared fluorescent probe for monitoring hydrazine in serum and living cells

A coumarin-quinolinium-based fluorescent probe for ratiometric sensing of sulfite in living cells