Recent progress on small molecule-based fluorescent imaging probes for hypochlorous acid (HOCl)/Hypochlorite (OCl−)

The current review describes advances in the use of fluorescent 2,1,3-benzothiadiazole (BTD) derivatives after nearly one decade since the first description of bioimaging experiments using this class of fluorogenic dyes. The review describes the use of BTD-containing fluorophores applied as, inter alia, bioprobes for imaging cell nuclei, mitochondria, lipid droplets, sensors, markers for proteins and related events, biological processes and activities, lysosomes, plasma membranes, multicellular models, and animals. A number of physicochemical and photophysical properties commonly observed for BTD fluorogenic structures are also described.

Fluorescent Benzothiadiazole Derivatives as Fluorescence Imaging Dyes: A Decade of New Generation Probes.

Recent advances in Carbon Dots/2-D hybrid materials

The detection of changes in the reactive oxygen species (ROS)/reactive sulfur species (RSS) couple is important for studying the cellular redox state. Herein, we developed a 1,8-naphthalimide-based fluorescence probe (NI) for the reversible detection of bisulfite (HSO3- ) and hydrogen peroxide (H2 O2 ) in vitro and in vivo. NI has been designed with a reactive ethylene unit which specifically reacts with HSO3- by a Michael addition reaction mechanism, resulting in the quenching of yellow fluorescence at 580 nm and the appearing of green fluorescence at 510 nm upon excitation at 500 nm and 430 nm, respectively. The addition product (NI-HSO3 ) could be specifically oxidized to form the original C=C bond of NI, recovering the fluorescence emission and color. The detection limits of NI for HSO3- and NI-HSO3 for H2 O2 were calculated to be 2.05 μM and 4.23 μM, respectively. The reversible fluorescence response of NI towards HSO3- /H2 O2 couple can be repeated for at least five times. NI is reliable at a broad pH range (pH 3.0-11.5) and features outstanding selectivity, which enabled its practical applications in biological and food samples. Monitoring the reversible and dynamic inter-conversion between HSO3- and H2 O2 in vitro and in vivo has been verified by fluorescence imaging in live HeLa cells, adult zebrafish and nude mice. Moreover, NI has been successfully applied to detect of HSO3- levels in food samples.

A Novel Fluorescence Probe for the Reversible Detection of Bisulfite and Hydrogen Peroxide Pair in Vitro and in Vivo.

Emergent Carbonized Polymer Dots as Versatile Featured Nanomaterial for Latent Fingerprints, Colorimetric Sensor, and Photocatalysis Applications

It is highly desired and challenging to construct integrated (all-in-one) single semiconducting-polymer-derived dot (Pdot) without any postmodification but with desired performances for bioapplications. In this work, eight hypochlorous acid (HClO)-sensitive integrated polymers and corresponding polymer-derived Pdots are designed through molecular engineering to comparatively study their analytical performances for detecting and imaging HClO. The optimized polymers-derived Pdots are obtained through regulating donor-acceptor structure, the content of HClO-sensitive units, and the position of HClO-sensitive units in the polymer backbone. The designed Pdots display distinguished characteristics including multicolours with blue, yellow, and red three primary fluorescence colors, determination mode from single-channel to dual-channel (ratiometric) quantification, ultrafast response, low detection limit, and high selectivity for ClO- sensing based on specific oxidation of ClO--sensitive unit 10-methylphenothiazine (PT) accompanied by altering the intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET) processes in Pdots. The prepared integrated Pdots are also applied for two-photon ClO- imaging in HeLa cells and one- and two-photon ClO- imaging produced in acute inflammation in mice with satisfactory results. We believe that the present study not only provides excellent integrated fluorescent nanoprobes for ClO- monitoring in living systems but also extends a general strategy for designing integrated semiconducting polymers and Pdots with desired performances for biological applications.

General Strategy to Achieve Color-Tunable Ratiometric Two-Photon Integrated Single Semiconducting Polymer Dot for Imaging Hypochlorous Acid.

In this study, a novel reaction-based A-A-A (acceptor-acceptor-acceptor) type two-photon fluorescent probe, BTC, is prepared using the benzothiadiazole (BTD) scaffold as the two-photon fluorophore and electron-accepting centre. Two β-chlorovinyl aldehyde moieties are symmetrically connected to both ends of the BTD scaffold and act as reaction groups to recognize SO2 and quenching groups to make the dis-activated probe stay at off-state due to their weak electron-withdrawing effect. In the presence of SO2 derivatives, the aldehyde groups are consumed through aldehyde addition, resulting in the activation of intramolecular charge transfer (ICT) processes and therefore recovering the fluorescence of the probe. The designed probe shows excellent two-photon properties including large two-photon absorption cross-sections (TPA) of 91 GM and photostability. Beyond these, the BTC probe exhibits a fast response to SO2 within 30 s, high specificity without foreign interference and a broad detection range from 500 nM to 120 μM with a detection limit of 190 nM. The designed fluorescent probe is further applied to the two-photon imaging of exogenous and endogenous SO2 derivatives under different physiological processes in HeLa cells and zebrafish with satisfactory results. We believe that the proposed design strategy can be extended to fabricate versatile BTD-based two-photon fluorescent probes through molecular engineering for further applications in bioassays and two-photon imaging.

A photostable reaction-based A-A-A type two-photon fluorescent probe for rapid detection and imaging of sulfur dioxide.

Dual-Emission Carbonized Polymer Dots for Ratiometric pH Sensing, pH-Dependent Generation of Singlet Oxygen, and Imaging-Guided Dynamics Monitoring of Photodynamic Therapy

Dual stimulus-responsive core-satellite SERS nanoprobes for reactive oxygen species sensing during autophagy.

Mitochondria-targeted and multistage synergistic ROS-elevated drug delivery system based on surface decorated MnO2 with CeO2 for enhanced chemodynamic/chemotherapy

Xiaoxiao Hu

Papers

General Strategy to Achieve Color-Tunable Ratiometric Two-Photon Integrated Single Semiconducting Polymer Dot for Imaging Hypochlorous Acid.

A photostable reaction-based A-A-A type two-photon fluorescent probe for rapid detection and imaging of sulfur dioxide.

Dual-Emission Carbonized Polymer Dots for Ratiometric pH Sensing, pH-Dependent Generation of Singlet Oxygen, and Imaging-Guided Dynamics Monitoring of Photodynamic Therapy

Dual stimulus-responsive core-satellite SERS nanoprobes for reactive oxygen species sensing during autophagy.

Mitochondria-targeted and multistage synergistic ROS-elevated drug delivery system based on surface decorated MnO2 with CeO2 for enhanced chemodynamic/chemotherapy