Reactive oxygen species (ROS) play an essential role in regulating various physiological functions of living organisms. The intrinsic biochemical properties of ROS, which underlie the mechanisms ne...

Reactive Oxygen Species (ROS)-Based Nanomedicine.

In this review we will explore recent advances in the design and application of excited-state intramolecular proton-transfer (ESIPT) based fluorescent probes. Fluorescence based sensors and imaging agents (probes) are important in biology, physiology, pharmacology, and environmental science for the selective detection of biologically and/or environmentally important species. The development of ESIPT-based fluorescence probes is particularly attractive due to their unique properties, which include a large Stokes shift, environmental sensitivity and potential for ratiometric sensing.

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Excited-state intramolecular proton-transfer (ESIPT) based fluorescence sensors and imaging agents

Biophotonics as a highly interdisciplinary frontier often requires the assistance of optical agents to control the light pathways in cells, tissues and living organisms for specific biomedical applications. Organic semiconducting materials (OSMs) composed of π-conjugated building blocks as the optically active components have recently emerged as a promising category of biophotonic agents. OSMs possess common features including excellent optical properties, good photostability and biologically benign composition. This review summarizes the recent progress in the development of OSMs based on small-molecule fluorophores, aggregation-induced emission (AIE) dyes and semiconducting oligomer/polymer nanoparticles (SONs/SPNs) for advanced biophotonic applications. OSMs have been exploited as imaging agents to transduce biomolecular interactions into second near-infrared fluorescence, chemiluminescence, afterglow or photoacoustic signals, enabling deep-tissue ultrasensitive imaging of biological tissues, disease biomarkers and physiological indexes. By fine-tuning the molecular structures, OSMs can also convert light energy into cytotoxic free radicals or heat, allowing for effective cancer phototherapy. Due to their instant light response and efficient light-harvesting properties, precise regulation of biological activities using OSMs as remote transducers has been demonstrated for protein ion channels, gene transcription and protein activation. In addition to highlighting OSMs as a multifunctional platform for a wide range of biomedical applications, current challenges and perspectives of OSMs in biophotonics are discussed.

Development of organic semiconducting materials for deep-tissue optical imaging, phototherapy and photoactivation

Surgical resection of solid tumors is currently the gold standard and preferred therapeutic strategy for cancer. Chemotherapy drugs also make a significant contribution by inhibiting the rapid growth of tumor cells and these two approaches are often combined to enhance treatment efficacy. However, surgery and chemotherapy inevitably lead to severe side effects and high systemic toxicity, which in turn results in poor prognosis. Precision medicine has promoted the development of treatment modalities that are developed to specifically target and kill tumor cells. Advances in in vivo medical imaging for visualizing tumor lesions can aid diagnosis, facilitate surgical resection, investigate therapeutic efficacy, and improve prognosis. In particular, the modality of fluorescence imaging has high specificity and sensitivity and has been utilized for medical imaging. Therefore, there are great opportunities for chemists and physicians to conceive, synthesize, and exploit new chemical probes that can image tumors and release chemotherapy drugs in vivo. This review focuses on small molecular ligand-targeted fluorescent imaging probes and fluorescent theranostics, including their design strategies and applications in clinical tumor treatment. The progress in chemical probes described here suggests that fluorescence imaging is a vital and rapidly developing field for interventional surgical imaging, as well as tumor diagnosis and therapy.

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Fluorescent chemical probes for accurate tumor diagnosis and targeting therapy

Fluorescent carbon dots (CDs) are a new class of carbon nanomaterials and have demonstrated excellent optical properties, good biocompatibility, great aqueous solubility, low cost, simple synthesis, etc. Since their discovery, various synthesis methods using different precursors have been developed, and are mainly classified as top-down and bottom-up approaches. For the mechanistic origin of CDs photoluminescence, three mechanisms have been proposed such as quantum confinement effect, surface state and molecule state. CDs have presented many applications, and this review article mainly focuses on the development of CDs based fluorescent sensors in recent 5 years. The sensing mechanisms, senor design and sensing properties to various targets are summarized. A broad range of analytes including cations, anions, small molecules, macromolecules, cells and bacteria have been discussed. In addition, the challenges and future directions for CDs as sensing materials are also presented.

Fluorescent carbon dots and their sensing applications

Reactive oxygen (ROS) and nitrogen (RNS) species cause oxidative and nitrosative stresses, respectively. These stresses are implicated not only in diverse physiological processes but also in various pathological processes, including cancer and neurodegenerative disorders. In addition, some ROS and RNS in the environment are pollutants that threaten human health. As a consequence of these effects, sensitive methods, which can be employed to selectively monitor ROS and RNS in live cells, tissues and organisms as well as in environmental samples, are needed so that their biological roles can be understood and their concentrations in environmental samples can be determined. In this review, fluorescent, luminescent and colorimetric ROS and RNS probes, which have been developed since 2011, are comprehensively discussed.

Recent progress in the development of fluorescent, luminescent and colorimetric probes for detection of reactive oxygen and nitrogen species

We have developed a ratiometric fluorescent probe for hypochlorite detection with high selectivity and sensitivity. The probe 1 can rapidly turn into an oxidized form accompanied by the fluorescence changes from yellow to blue only upon the addition of hypochlorite among various reactive oxygen species (ROS) and reactive nitrogen species (RNS). The limit of detection was calculated to be as low as 8.9 nM, which showed good sensitivity to hypochlorite. Furthermore, the confocal laser scanning micrographs of HeLa cells confirmed good cell permeability of probe 1 and its application to selective detecting hypochlorite in living cells.

Benzothiazole-based fluorescent sensor for hypochlorite detection and its application for biological imaging

Aluminum is the third (after O and Si) most abundant metal in the earth’s crust and associates with neurological diseases when abnormal level of Al3+ occurs in nervous center. Developing highly sensitive and selective methods for Al3+ detection is of significant interest. In this work, we developed an excited state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) active fluorescent probe for ratiometric detection of Al3+ in aqueous medium and living cells. The BTZ-SF can detect Al3+ with high selectivity and a good linear relationship (R2 = 0.9911) between fluorescence intensity ratio (I476 nm/I568 nm) and Al3+ concentration (0–100 μM). In addition, the detection limit was calculated as low as 2.2 μM. The single crystal structure of BTZ-SF–Al clearly exhibited the interaction between BTZ-SF and Al3+ with a hexa-coordinated structure. Furthermore, confocal fluorescence images of HeLa cell indicated that BTZ-SF could be used for monitoring Al3+ in living cells. Finally, a test s...

A Benzothiazole-Based Fluorescent Probe for Ratiometric Detection of Al3+ in Aqueous Medium and Living Cells

Organic solid materials with color-tunable emissions have been extensively applied in various fields. However, a rational design and facile synthesis of an ideal fluorophore are still challenging due to the undesirable aggregation-caused quenching effect in concentrated solution and solid form. Herein, we have developed a series of 2-(2'-hydroxyphenyl)benzothiazole (HBT)-derived color-tunable solid emitters by switching functional groups at the ortho-position of a hydroxyl group via formylation and an aldol condensation reaction. By tuning the electron-withdrawing ability and the π-conjugated framework introduced by the functional groups, fluorophores emit light covering the full-color range from blue to near-infrared regions with high quantum yields in their solid form and show a significant solvatochromic effect in polar solvents. The aggregation-induced emission (AIE) or aggregation-induced emission enhancement (AIEE) and excited-state intramolecular proton transfer (ESIPT) involving fluorescence mechanism, along with their inter/intramolecular interactions in crystals, are elucidated to depict the key factors for tunable emissions and high emitting efficiency. Furthermore, high-quality white-light-emitting materials are obtained in various solvents and polydimethylsiloxane (PDMS) films with combined fluorophores. Overall, these studies report a promising strategy for the construction of organic solid materials with color-tunable emission and shed light on methods for obtaining desirable emission efficiency.

Color-Tunable and ESIPT-Inspired Solid Fluorophores Based on Benzothiazole Derivatives: Aggregation-Induced Emission, Strong Solvatochromic Effect, and White Light Emission.

Enhanced response speed and selectivity of fluorescein-based H2S probe via the cleavage of nitrobenzene sulfonyl ester assisted by ortho aldehyde groups.

Jian Qiang

Papers

Recent progress in the development of fluorescent, luminescent and colorimetric probes for detection of reactive oxygen and nitrogen species

Benzothiazole-based fluorescent sensor for hypochlorite detection and its application for biological imaging

A Benzothiazole-Based Fluorescent Probe for Ratiometric Detection of Al3+ in Aqueous Medium and Living Cells

Color-Tunable and ESIPT-Inspired Solid Fluorophores Based on Benzothiazole Derivatives: Aggregation-Induced Emission, Strong Solvatochromic Effect, and White Light Emission.

Enhanced response speed and selectivity of fluorescein-based H2S probe via the cleavage of nitrobenzene sulfonyl ester assisted by ortho aldehyde groups.