Imaging and Detection of Carboxylesterase in Living Cells and Zebrafish Pretreated with Pesticides by a New Near-Infrared Fluorescence Off–On Probe

A new near-infrared fluorescence off–on probe was developed and applied to fluorescence imaging of carboxylesterase in living HepG-2 cells and zebrafish pretreated with pesticides (carbamate, organophosphorus, and pyrethroid). The probe was readily prepared by connecting (4-acetoxybenzyl)­oxy as a quenching and recognizing moiety to a stable hemicyanine skeleton that can be formed via the decomposition of IR-780. The fluorescence off–on response of the probe to carboxylesterase is based on the enzyme-catalyzed spontaneous hydrolysis of the carboxylic ester bond, followed by a further fragmentation of the phenylmethyl unit and thereby the fluorophore release. Compared with the only existing near-infrared carboxylesterase probe, the proposed probe exhibits superior analytical performance, such as near-infrared fluorescence emission over 700 nm as well as high selectivity and sensitivity, with a detection limit of 4.5 × 10^–3 U/mL. More importantly, the probe is cell membrane permeable, and its applicability has been successfully demonstrated for monitoring carboxylesterase activity in living HepG-2 cells and zebrafish pretreated with pesticides, revealing that pesticides can effectively inhibit the activity of carboxylesterase. The superior properties of the probe make it of great potential use in indicating pesticide exposure

Benzoyl Peroxide Detection in Real Samples and Zebrafish Imaging by a Designed Near-Infrared Fluorescent Probe

A novel near-infrared fluorescence off–on probe, (<i>E</i>)-3,3-dimethyl-1-propyl-2-(2-(6-(2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)­benzyloxy)-2,3-dihydro-1<i>H</i>-xanthen-4-yl)­vinyl)-3<i>H</i>-indolium (<b>1</b>), is developed and applied to benzoyl peroxide (BPO) detection in real samples and fluorescence imaging in living cells and zebrafish. When arylboronate as the recognition unit is connected to a stable hemicyanine skeleton, the probe is readily prepared, which exhibits superior analytical performance, such as near-infrared fluorescence emission over 700 nm and high sensitivity with a low detection limit of 47 nM. Upon reaction with BPO, phenylboronic acid pinacol ester is oxidized, followed by hydrolysis and 1,4-elimination of <i>o</i>-quinone methide to release fluorophore. In addtion, the probe displays high selectivity toward BPO over other common substances, which makes it of great potential use in quantitative and simple detection of BPO in wheat flour and antimicrobial agent. More importantly, the probe has been successfully demonstrated for monitoring BPO in living HeLa cells and zebrafish. The probe with superior properties could be of great potential use in other biosystems and <i>in vivo</i> studies

Semiconductor Plasmon Induced Up-Conversion Enhancement in mCu_2–<i>x</i>S@SiO₂@Y₂O₃:Yb³⁺/Er³⁺ Core–Shell Nanocomposites

The ability to modulate the intensity of electromagnetic field by semiconductor plasmon nanoparticles is becoming attractive due to its unique doping-induced local surface plasmon resonance (LSPR) effect that is different from metals. Herein, we synthesized mCu_2–<i>x</i>S@SiO₂@Y₂O₃:Yb³⁺/Er³⁺ core–shell composites and experimentally and theoretically studied the semiconductor plasmon induced up-conversion enhancement and obtained 30-fold up-conversion enhancement compared with that of SiO₂@Y₂O₃:Yb³⁺/Er³⁺ composites. The up-conversion enhancement was induced by the synthetic effect: the amplification of the excitation field and the increase of resonance energy transfer (ET) rate from Yb³⁺ ions to Er³⁺ ions. The experimental results were analyzed in the light of finite-difference time-domain (FDTD) calculations, confirming the effect of the amplification of the excitation field. In addition, up-conversion luminescence (UCL) spectra, up-conversion enhancement, and dynamics dependent on concentration (Yb³⁺ and Er³⁺ ions) were investigated, and it was found that the resonance ET rate from Yb³⁺ ions to Er³⁺ ions increased ∼25% in the effect of LSPR waves. Finally, the power dependence of fingerprint identification was successfully performed based on the mCu_2–<i>x</i>S@SiO₂@Y₂O₃:Yb³⁺/Er³⁺ core–shell composites, the color of which can change from green to orange with excitation power increasing. Our work opens up a new concept to design and fabricate the up-conversion core–shell structure based on semiconductor plasmon nanoparticles (NPs) and provides applications for up-conversion nanocrystals (UCNPs) and semiconductor plasmon NPs in photonics

Semiconductor Plasmon Induced Up-Conversion Enhancement in mCu_2–<i>x</i>S@SiO₂@Y₂O₃:Yb³⁺/Er³⁺ Core–Shell Nanocomposites

The ability to modulate the intensity of electromagnetic field by semiconductor plasmon nanoparticles is becoming attractive due to its unique doping-induced local surface plasmon resonance (LSPR) effect that is different from metals. Herein, we synthesized mCu_2–<i>x</i>S@SiO₂@Y₂O₃:Yb³⁺/Er³⁺ core–shell composites and experimentally and theoretically studied the semiconductor plasmon induced up-conversion enhancement and obtained 30-fold up-conversion enhancement compared with that of SiO₂@Y₂O₃:Yb³⁺/Er³⁺ composites. The up-conversion enhancement was induced by the synthetic effect: the amplification of the excitation field and the increase of resonance energy transfer (ET) rate from Yb³⁺ ions to Er³⁺ ions. The experimental results were analyzed in the light of finite-difference time-domain (FDTD) calculations, confirming the effect of the amplification of the excitation field. In addition, up-conversion luminescence (UCL) spectra, up-conversion enhancement, and dynamics dependent on concentration (Yb³⁺ and Er³⁺ ions) were investigated, and it was found that the resonance ET rate from Yb³⁺ ions to Er³⁺ ions increased ∼25% in the effect of LSPR waves. Finally, the power dependence of fingerprint identification was successfully performed based on the mCu_2–<i>x</i>S@SiO₂@Y₂O₃:Yb³⁺/Er³⁺ core–shell composites, the color of which can change from green to orange with excitation power increasing. Our work opens up a new concept to design and fabricate the up-conversion core–shell structure based on semiconductor plasmon nanoparticles (NPs) and provides applications for up-conversion nanocrystals (UCNPs) and semiconductor plasmon NPs in photonics

Self-Stabilized Quasi-2D Perovskite with an Ion-Migration-Inhibition Ligand for Pure Green LEDs

Perovskite light-emitting diodes (PeLEDs) have recently achieved a great breakthrough in external quantum efficiency (EQE). However, the operational stability of pure primary color PeLEDs lags far behind because of serious ion migration. Herein, a self-stabilized quasi-2D perovskite is constructed with a strategically synthesized ion-migration-inhibition ligand (IMIligand) to realize highly stable and efficient pure green PeLEDs approaching the standard green light of Rec. 2020. The IMIligand takes the role to not only eliminate migration pathways and anchor halide ions to suppress the ion migration but to also further enhance the crystalline orientation and energy transfer in quasi-2D perovskites. Meanwhile, the self-stabilized quasi-2D perovskite overcomes the degradation of electrical performance caused by conventional exogenous passivation additives. Ultimately, the figure of merit of the pure green quasi-2D PeLEDs is at least double that of previous works. The devices achieve an EQE of 26.2% and operational stability of 920 min at initial luminance of 1000 cd m–2

Stable and Size-Tunable Aggregation-Induced Emission Nanoparticles Encapsulated with Nanographene Oxide and Applications in Three-Photon Fluorescence Bioimaging

Organic fluorescent dyes with high quantum yield are widely applied in bioimaging and biosensing. However, most of them suffer from a severe effect called aggregation-caused quenching (ACQ), which means that their fluorescence is quenched at high molecular concentrations or in the aggregation state. Aggregation-induced emission (AIE) is a diametrically opposite phenomenon to ACQ, and luminogens with this feature can effectively solve this problem. Graphene oxide has been utilized as a quencher for many fluorescent dyes, based on which biosensing can be achieved. However, using graphene oxide as a surface modification agent of fluorescent nanoparticles is seldom reported. In this article, we used nanographene oxide (NGO) to encapsulate fluorescent nanoparticles, which consisted of a type of AIE dye named TPE-TPA-FN (TTF). NGO significantly improved the stability of nanoparticles in aqueous dispersion. In addition, this method could control the size of nanoparticles’ flexibly as well as increase their emission efficiency. We then used the NGO-modified TTF nanoparticles to achieve three-photon fluorescence bioimaging. The architecture of ear blood vessels in mice and the distribution of nanoparticles in zebrafish could be observed clearly. Furthermore, we extended this method to other AIE luminogens and showed it was widely feasible

Aggregation-Induced Emission Luminogen with Near-Infrared-II Excitation and Near-Infrared‑I Emission for Ultradeep Intravital Two-Photon Microscopy

Currently, a serious problem obstructing the large-scale clinical applications of fluorescence technique is the shallow penetration depth. Two-photon fluorescence microscopic imaging with excitation in the longer-wavelength near-infrared (NIR) region (>1100 nm) and emission in the NIR-I region (650–950 nm) is a good choice to realize deep-tissue and high-resolution imaging. Here, we report ultradeep two-photon fluorescence bioimaging with 1300 nm NIR-II excitation and NIR-I emission (peak ∼810 nm) based on a NIR aggregation-induced emission luminogen (AIEgen). The crab-shaped AIEgen possesses a planar core structure and several twisting phenyl/naphthyl rotators, affording both high fluorescence quantum yield and efficient two-photon activity. The organic AIE dots show high stability, good biocompatibility, and a large two-photon absorption cross section of 1.22 × 10³ GM. Under 1300 nm NIR-II excitation, <i>in vivo</i> two-photon fluorescence microscopic imaging helps to reconstruct the 3D vasculature with a high spatial resolution of sub-3.5 μm beyond the white matter (>840 μm) and even to the hippocampus (>960 μm) and visualize small vessels of ∼5 μm as deep as 1065 μm in mouse brain, which is among the largest penetration depths and best spatial resolution of <i>in vivo</i> two-photon imaging. Rational comparison with the AIE dots manifests that two-photon imaging outperforms the one-photon mode for high-resolution deep imaging. This work will inspire more sight and insight into the development of efficient NIR fluorophores for deep-tissue biomedical imaging

Aggregation-Induced Emission Luminogen with Near-Infrared-II Excitation and Near-Infrared‑I Emission for Ultradeep Intravital Two-Photon Microscopy

Currently, a serious problem obstructing the large-scale clinical applications of fluorescence technique is the shallow penetration depth. Two-photon fluorescence microscopic imaging with excitation in the longer-wavelength near-infrared (NIR) region (>1100 nm) and emission in the NIR-I region (650–950 nm) is a good choice to realize deep-tissue and high-resolution imaging. Here, we report ultradeep two-photon fluorescence bioimaging with 1300 nm NIR-II excitation and NIR-I emission (peak ∼810 nm) based on a NIR aggregation-induced emission luminogen (AIEgen). The crab-shaped AIEgen possesses a planar core structure and several twisting phenyl/naphthyl rotators, affording both high fluorescence quantum yield and efficient two-photon activity. The organic AIE dots show high stability, good biocompatibility, and a large two-photon absorption cross section of 1.22 × 10³ GM. Under 1300 nm NIR-II excitation, <i>in vivo</i> two-photon fluorescence microscopic imaging helps to reconstruct the 3D vasculature with a high spatial resolution of sub-3.5 μm beyond the white matter (>840 μm) and even to the hippocampus (>960 μm) and visualize small vessels of ∼5 μm as deep as 1065 μm in mouse brain, which is among the largest penetration depths and best spatial resolution of <i>in vivo</i> two-photon imaging. Rational comparison with the AIE dots manifests that two-photon imaging outperforms the one-photon mode for high-resolution deep imaging. This work will inspire more sight and insight into the development of efficient NIR fluorophores for deep-tissue biomedical imaging

Aggregation-Induced Emission Luminogen with Near-Infrared-II Excitation and Near-Infrared‑I Emission for Ultradeep Intravital Two-Photon Microscopy

Currently, a serious problem obstructing the large-scale clinical applications of fluorescence technique is the shallow penetration depth. Two-photon fluorescence microscopic imaging with excitation in the longer-wavelength near-infrared (NIR) region (>1100 nm) and emission in the NIR-I region (650–950 nm) is a good choice to realize deep-tissue and high-resolution imaging. Here, we report ultradeep two-photon fluorescence bioimaging with 1300 nm NIR-II excitation and NIR-I emission (peak ∼810 nm) based on a NIR aggregation-induced emission luminogen (AIEgen). The crab-shaped AIEgen possesses a planar core structure and several twisting phenyl/naphthyl rotators, affording both high fluorescence quantum yield and efficient two-photon activity. The organic AIE dots show high stability, good biocompatibility, and a large two-photon absorption cross section of 1.22 × 10³ GM. Under 1300 nm NIR-II excitation, <i>in vivo</i> two-photon fluorescence microscopic imaging helps to reconstruct the 3D vasculature with a high spatial resolution of sub-3.5 μm beyond the white matter (>840 μm) and even to the hippocampus (>960 μm) and visualize small vessels of ∼5 μm as deep as 1065 μm in mouse brain, which is among the largest penetration depths and best spatial resolution of <i>in vivo</i> two-photon imaging. Rational comparison with the AIE dots manifests that two-photon imaging outperforms the one-photon mode for high-resolution deep imaging. This work will inspire more sight and insight into the development of efficient NIR fluorophores for deep-tissue biomedical imaging

Aggregation-Induced Emission Luminogen with Near-Infrared-II Excitation and Near-Infrared‑I Emission for Ultradeep Intravital Two-Photon Microscopy

Currently, a serious problem obstructing the large-scale clinical applications of fluorescence technique is the shallow penetration depth. Two-photon fluorescence microscopic imaging with excitation in the longer-wavelength near-infrared (NIR) region (>1100 nm) and emission in the NIR-I region (650–950 nm) is a good choice to realize deep-tissue and high-resolution imaging. Here, we report ultradeep two-photon fluorescence bioimaging with 1300 nm NIR-II excitation and NIR-I emission (peak ∼810 nm) based on a NIR aggregation-induced emission luminogen (AIEgen). The crab-shaped AIEgen possesses a planar core structure and several twisting phenyl/naphthyl rotators, affording both high fluorescence quantum yield and efficient two-photon activity. The organic AIE dots show high stability, good biocompatibility, and a large two-photon absorption cross section of 1.22 × 10³ GM. Under 1300 nm NIR-II excitation, <i>in vivo</i> two-photon fluorescence microscopic imaging helps to reconstruct the 3D vasculature with a high spatial resolution of sub-3.5 μm beyond the white matter (>840 μm) and even to the hippocampus (>960 μm) and visualize small vessels of ∼5 μm as deep as 1065 μm in mouse brain, which is among the largest penetration depths and best spatial resolution of <i>in vivo</i> two-photon imaging. Rational comparison with the AIE dots manifests that two-photon imaging outperforms the one-photon mode for high-resolution deep imaging. This work will inspire more sight and insight into the development of efficient NIR fluorophores for deep-tissue biomedical imaging