In Situ Visualizing Carboxylesterase Activity in Type 2 Diabetes Mellitus Using an Activatable Endoplasmic Reticulum Targetable Proximity Labeling Far-Red Fluorescent Probe.

Carboxylesterase (CE), an enzyme widely present in organisms, is involved in various physiological and pathological processes. Changes in the levels of CEs in the liver may predict the presence of type 2 diabetes mellitus (T2DM). Here, a novel dicyanoisophorone (DCI)-based proximity-labeled far-red fluorescent probe DCI2F-Ac with endoplasmic reticulum targeting was proposed for real-time monitoring and imaging of the CEs activity. DCI2F-Ac featured very low cytotoxicity and biotoxicity and was highly selective and sensitive for CEs. Compared with traditional CEs probes, DCI2F-Ac was covalently anchored directly to CEs, thus effectively reducing the loss of in situ fluorescent signals due to diffusion. Through the "on-off" fluorescence signal readout, DCI2F-Ac was able to distinguish cell lines and screen for CEs inhibitors. In terms of endoplasmic reticulum (ER) stress, it was found that thapsigargin (Tg) induced upregulation of CEs levels but not tunicamycin (Tm), which was related to the calcium homeostasis of the ER. DCI2F-Ac could efficiently detect downregulated CEs in the livers of T2DM, and the therapeutic efficacy of metformin, acarbose, and a combination of these two drugs was assessed by tracking the fluctuation of CEs levels. The results showed that combining metformin and acarbose could restore CEs levels to near-normal levels with the best antidiabetic effect. Thus, the DCI2F-Ac probe provides a great opportunity to explore the untapped potential of CEs in liver metabolic disorders and drug efficacy assessment.

A Fluorescent Probe with Zwitterionic ESIPT Feature for Ratiometric Monitoring of Peroxynitrite In Vitro and In Vivo.

Peroxynitrite (ONOO-), as a short-term reactive biological oxidant, could lead to a series of effects in various physiological and pathological processes due to its subtle concentration changes. In vivo monitoring of ONOO- and relevant physiological processes is urgently required. Herein, we describe a novel fluorescent probe termed HBT-Fl-BnB for the ratiometric detection of ONOO- in vitro and in vivo. The probe consists of an HBT core with Fl groups at the ortho and para positions responding to the zwitterionic excited-state intramolecular proton-transfer (zwitterionic ESIPT) process and a boronic acid pinacol ester with dual roles that block the zwitterionic ESIPT and recognize ONOO-. Thanks to the specificity as well as low cytotoxicity, success in imaging of endogenous and exogenous ONOO- in living cells by HBT-Fl-BnB was obtained. Additionally, the applicability of HBT-Fl-BnB to tracking the abnormal expression of ONOO- in vivo induced by inactivated Escherichia coli was also explored. This is the first report of a fluorescent probe for ONOO- sensing via a zwitterionic ESIPT mechanism.

The effect of thionation of the carbonyl group on the photophysics of compact spiro rhodamine-naphthalimide electron donor-acceptor dyads: intersystem crossing, charge separation, and electron spin dynamics.

Herein, a spiro rhodamine (Rho)-thionated naphthalimide (NIS) electron donor-acceptor orthogonal dyad (Rho-NIS) was prepared to study the formation of a long-lived charge separation (CS) state via the electron spin control approach. The transient absorption (TA) spectra of Rho-NIS indicated that the intersystem crossing (ISC) occurs within 7-42 ps to produce the 3NIS state via the spin orbit coupling ISC (SOC-ISC). The energy order of 3CS (2.01 eV in n-hexane, HEX) and 3LE states (1.68 eV in HEX) depended on the solvent polarity. The 3NIS state having n-π* character and a lifetime of 0.38 µs was observed for Rho-NIS in toluene (TOL). Alternatively, in acetonitrile (ACN), the long-lived 3CS state (0.21 µs) with a high CS state quantum yield (ΦCS, 97%) was produced with the 3NIS state as the precursor and the CS took 134 ps. On the contrary, in the case of the reference Rho-naphthalimide (NI) Rho-NI dyad without thionation of its carbonyl group, a long-lived CS state (0.94 µs) with a high energy level (ECS = 2.12 eV) was generated even in HEX with a lower ΦCS (49%). In the presence of an acid, the Rho unit in the Rho-NIS adopted an open form (Rho-o) and the 3NIS state was produced within 24-47 ps with the 1Rho-o state as the precursor. Subsequently, slow intramolecular triplet-triplet energy transfer (TTET, 0.11-0.60 µs) produced the 3Rho-o state (9.4-13.6 µs). According to the time-resolved electron paramagnetic resonance (TREPR) spectra of NIS-NH2, the zero-field splitting (ZFS) parameter |D| and E of the triplet state were determined to be 6165 MHz and -1233 MHz, respectively, indicating that its triplet state has significant nπ* character, which was supported by its short triplet state lifetime (6.1 µs).

The effect of dark states on the intersystem crossing and thermally activated delayed fluorescence of naphthalimide-phenothiazine dyads.

A series of 1,8-naphthalimide (NI)-phenothiazine (PTZ) electron donor-acceptor dyads were prepared to study the thermally activated delayed fluorescence (TADF) properties of the dyads, from a point of view of detection of the various transient species. The photophysical properties of the dyads were tuned by changing the electron-donating and the electron-withdrawing capability of the PTZ and NI moieties, respectively, by oxidation of the PTZ unit, or by using different aryl substituents attached to the NI unit. This tuning effect was manifested in the UV-vis absorption and fluorescence emission spectra, e.g., in the change of the charge transfer absorption bands. TADF was observed for the dyads containing the native PTZ unit, and the prompt and delayed fluorescence lifetimes changed with different aryl substituents on the imide part. In polar solvents, no TADF was observed. For the dyads with the PTZ unit oxidized, no TADF was observed as well. Femtosecond transient absorption spectra showed that the charge separation takes ca. 0.6 ps, and admixtures of locally excited (3LE) state and charge separated (1CS/3CS) states formed (in n-hexane). The subsequent charge recombination from the 1CS state takes ca. 7.92 ns. Upon oxidation of the PTZ unit, the beginning of charge separation is at 178 fs and formation of 3LE state takes 4.53 ns. Nanosecond transient absorption (ns-TA) spectra showed that both 3CS and 3LE states were observed for the dyads showing TADF, whereas only 3LE or 3CS states were observed for the systems lacking TADF. This is a rare but unambiguous experimental evidence that the spin-vibronic coupling of 3CS/3LE states is crucial for TADF. Without the mediating effect of the 3LE state, no TADF is resulted, even if the long-lived 3CS state is populated (lifetime τCS ≈ 140 ns). This experimental result confirms the 3CS → 1CS reverse intersystem crossing (rISC) is slow, without coupling with an approximate 3LE state. These studies are useful for an in-depth understanding of the photophysical mechanisms of the TADF emitters, as well as for molecular structure design of new electron donor-acceptor TADF emitters.

Indication of Dynamic Peroxynitrite Fluctuations in the Rat Epilepsy Model with a Near-Infrared Two-Photon Fluorescent Probe.

Epilepsy is a chronic neurodegenerative disease that has seriously threatened human health. Accumulating evidence reveals that the pathological progression of epilepsy is closely related to peroxynitrite (ONOO-). Unfortunately, understanding the physiological roles of ONOO- in epilepsy is still challenging due to the lack of powerful imaging probes for the determination of the level of fluctuations of ONOO- in the epileptic brain. Herein, a near-infrared (NIR) two-photon (TP) fluorescent probe [dicyanomethylene-4H-pyran (DCM)-ONOO] is presented to trace ONOO- in living cells and in kainate (KA)-induced rat epilepsy models with satisfactory sensitivity and selectivity. The probe is composed of a NIR TP DCM fluorophore and a recognition moiety diphenylphosphinamide. The phosphoramide bond of the probe is interrupted after reacting with ONOO- for 10 min, and then, the released amino groups emit strong fluorescence due to the restoration of the intramolecular charge transfer process. The probe can effectively detect the changes of endogenous ONOO- with excellent temporal and spatial resolution in living cells and in rat epileptic brain. The imaging results demonstrate that the increasing level of ONOO- is closely associated with epilepsy and severe neuronal damage in the brain under KA stimulation. In addition, the low-dose resveratrol can effectively inhibit ONOO- overexpression and further relieve neuronal damage. With the assistance of TP fluorescence imaging in the epileptic brain tissue, we hypothesize that the abnormal levels of ONOO- may serve as a potential indicator for the diagnosis of epilepsy. The TP fluorescence imaging based on DCM-ONOO provides a great potential approach for understanding the epilepsy pathology and diagnosis.

Rational Design of a Highly Selective Near-Infrared Two-Photon Fluorogenic Probe for Imaging Orthotopic Hepatocellular Carcinoma Chemotherapy.

Selective fluorescence imaging of biomarkers in vivo and in situ for evaluating orthotopic hepatocellular carcinoma (HCC) chemotherapy remains a great challenge due to current imaging agents suffering from the potential interferences of other hydrolases. Herein, we observed that carbamate unit showed a high selectivity toward the HCC-related biomarker carboxylesterase (CE) for evaluation of treatment. A near-infrared two-photon fluorescent probe was developed to not only specially image CE activity in vivo and in situ but also target orthotopic liver tumor after systemic administration. The in vivo signals of the probe correlate well with tumor apoptosis, making it possible to evaluate the status of treatment. The probe enables the imaging of CE activity in situ with a high-resolution three-dimensional view for the first time. This study may promote advances in optical imaging approaches for precise imaging-guided diagnosis of HCC in situ and its evaluation of treatment.

Detection of Selenocysteine with a Ratiometric near-Infrared Fluorescent Probe in Cells and in Mice Thyroid Diseases Model.

The pathological progression of thyroid diseases poses a serious threat to human health. Because thyroid diseases are closely related to selenocysteine (Sec), it is necessary to investigate the relationship between Sec and thyroid diseases. Herein, we design and synthesize a ratiometric near-infrared fluorescent probe (Mito-Cy-Sec) to analyze the fluctuations and roles of Sec in cells and in mice thyroid diseases model. The probe is composed of a near-infrared heptamethine cyanine fluorophore, an acrylamide as the response moiety, and a lipophilic triphenylphosphonium cation as the mitochondrial localization group. After reacting with Sec for 5 min, the probe Mito-Cy-Sec exhibits a distinct ratiometric fluorescence signal accompanied by a color change from green to blue. The applicability of Mito-Cy-Sec in mitochondrial localization is assessed via the super-resolution imaging. Mito-Cy-Sec has been successfully applied to detect the fluctuations of Sec concentration in human thyroid epithelial/cancer cell lines (Nthy-ori-3 cells/BHT101 cells) and mice thyroid disease (thyroiditis and thyroid cancer) models. Besides, both of our probes Mito-Cy-Sec and commercial ROSGreen H2O2 are employed to examine the interrelationship between H2O2 and Sec in cells and in mice models. The results demonstrate that the relevant-levels between H2O2 and Sec are exactly negative correlation. The related-levels of Sec and H2O2 may be identified as diagnostic indicators for the auxiliary diagnosis of thyroid diseases. We suppose that our probe Mito-Cy-Sec can be employed as a promising chemical tool for the diagnosis of thyroid diseases.

Imaging of Endogenous Hydrogen Peroxide during the Process of Cell Mitosis and Mouse Brain Development with a Near-Infrared Ratiometric Fluorescent Probe.

Hydrogen peroxide (H2O2) is emerging as a new second messenger, which plays vital roles in intracellular signaling, thereby triggering physiological variations in terms of proliferation, differentiation, and migration. As known, cell mitosis has close association to the intracellular level of H2O2, which contribute to the significant effects on brain development, especially during the critical period of immaturity. Unfortunately, imaging H2O2 in a mammalian brain is still challenging. Herein, to further investigate the biological roles of endogenous H2O2 in cell mitosis, we develop a near-infrared ratiometric fluorescent probe Cy-PFS for specifically imaging endogenous H2O2 in cells and in vivo. Employing the probe Cy-PFS, we examine the critical effects of endogenous H2O2 on proliferation of cells in live hippocampal neurons cells, and our results provide strong evidence for H2O2 signaling in cell mitosis through growth factor signaling. Furthermore, we successfully demonstrate the close association of endogenous H2O2 level changes with the brain development at various stages. We envision that this present probe has potential as a promising useful chemical imaging tool for exploring the roles of H2O2 in cell mitosis.

Evaluation of Glutathione S-Transferase Inhibition Effects on Idiopathic Pulmonary Fibrosis Therapy with a Near-Infrared Fluorescent Probe in Cell and Mice Models.

Idiopathic pulmonary fibrosis (IPF) is a lung-limited and progressive fibrotic disease. The early diagnosis and therapies of IPF are still full of clinical challenges. Glutathione S-transferase (GSTs) plays significant roles in promoting the formation of pulmonary fibrosis. Herein, we report a fluorescent probe (Cy-GST) for the detection of GSTs concentration fluctuations in cells and in mice models. The probe can selectively and sensitively respond to GSTs with an "off-on" type fluorescence switch. Our results demonstrated that the level of intracellular GSTs increase in the pulmonary fibrosis cells and mice models. And the IPF patients hold high levels of GSTs concentrations. Thus, GSTs are likely to play important roles in pulmonary fibrosis. The inhibitor of GSTs TLK117 can reduce the severity of pulmonary fibrosis. The synergistic treatment of TLK117 and pirfenidone have better therapeutic effects than only using pirfenidone in pulmonary fibrosis mice models. The level of GSTs in IPF may be a new potential marker for IPF diagnosis. And the inhibition of GSTs may be a new therapeutic strategy for IPF treatment.

Sequential Detection of Superoxide Anion and Hydrogen Polysulfides under Hypoxic Stress via a Spectral-Response-Separated Fluorescent Probe Functioned with a Nitrobenzene Derivative.

Chronic hypoxic stress disrupts the intracellular redox homeostasis, leads to a series of physiological dysfunction, and finally results in many diseases including cancer and inflammatory and cardiovascular diseases. The intracellular redox status is related to the homeostasis between reactive oxygen species (ROS) and cellular antioxidant species. Superoxide anion (O2•-) is considered to be a precursor of ROS. As a member of reactive sulfur species, hydrogen polysulfides (H2S n) are a class of antioxidants in cells, which act as an important regulator for the intracellular redox state. Therefore, trapping the cross-talk of O2•- and H2S n is a benefit for further understanding the physiological and pathological effects. Herein, we conceive a fluorescent probe HCy-ONO for sequential detection of O2•- and H2Sn in cells and in mouse models. Based on a tandem reaction, the probe HCy-ONO can be used to detect O2•- and H2S n in different fluorescence collection windows without spectral overlap interference with limits of detection 90 and 100 nM, respectively. The strategy affords high sensitivity and selectivity for our detection in living cell models under continuous hypoxic and intermittent hypoxic conditions, revealing the reason for ischemia-reperfusion injury. Moreover, the probe can distinguish the inflamed tissue from normal tissue in acute peritonitis mouse model. Finally, our probe is successfully applied for imaging of O2•- and H2S n in the SH-SY5Y tumor-bearing mouse model, which is helpful to elucidate the physiological and pathological processes. These data demonstrated that different hypoxic status lead to different concentrations between H2S n and O2•-.

Detection of phosphorus species in water: technology and strategies.

Phosphorus species are the sum of naturally evolved phosphorus elements with diverse forms of existence and unique properties. The detection and analysis of the optical properties of unknown phosphorus species via direct or indirect strategies offers unique advantages in understanding the growth processes and existence characteristics of various chemicals and microorganisms in water environments. This review highlights recent advances and future trends in methods of detection of total phosphorus in water, including photoelectric strategies, spectroscopy techniques, and modeling algorithms. These methods effectively explore the dynamic changes of total phosphorus content in complex water environments to reveal important signals in water, which is of great guiding significance for achieving accurate detection of water quality and promoting social development. We also discuss some extended strategies for its measurement and prediction via rational design and cross-combination, which may help inspire future design of more accurate and intelligent detection models or systems. The strategies based on these types of total phosphorus detection methods provide a versatile platform for novel sensors and thereby show great potential in the development of future water quality detection applications.

SERS-based immunoassay using gold-patterned array chips for rapid and sensitive detection of dual cardiac biomarkers.

Cardiac troponin I (cTnI) and creatine kinase-MB (CK-MB) are important diagnostic biomarkers for acute myocardial infarction (AMI). Many efforts have been undertaken to develop highly sensitive detection methods for the quantitative analysis of these dual targets. However, current immunoassay methods are inadequate for accurate measurement of cTnI and CK-MB, due to their limited detection sensitivity. Thus, there is still an urgent demand for a new technique that will enable ultrahigh sensitive detection of these biomarkers. In this study, we developed a surface-enhanced Raman scattering (SERS)-based sandwich immunoassay platform for the ultrasensitive detection of cTnI and CK-MB. In this study, a monoclonal-antibody-immobilized gold-patterned chip was used as a SERS active template. Target samples and polyclonal-antibody-conjugated Au@Ag core-shell nanoparticles were then added. Using this SERS platform, the concentration of biomarkers could be quantified by monitoring the characteristic Raman peak intensity of Raman reporter molecules. Under optimized conditions, the limits of detection (LODs) were estimated to be 8.9 pg mL-1 and 9.7 pg mL-1 for cTnI and CK-MB, respectively. Thus, the proposed SERS-based immunoassay has great potential to be an effective diagnostic tool for the rapid and accurate detection of cTnI and CK-MB.

Evaluation Selenocysteine Protective Effect in Carbon Disulfide Induced Hepatitis with a Mitochondrial Targeting Ratiometric Near-Infrared Fluorescent Probe.

As important active sites of oxidoreductase in mitochondria, selenocysteine (Sec) takes the responsibility for cytoprotective effect and intracellular redox homeostasis. Carbon disulfide (CS2) is a common solvent in industry, which can inhibit the activities of oxidoreductase and induce oxidative stress. It is necessary to investigate the cytoprotective effect of Sec against CS2 exposure. After integrated, the response moiety 2,4-dinitrobenzenesulfonamide and mitochondrial targeting moiety into the near-infrared heptamethine cyanine fluorophore, we develop a mitochondrial targeting near-infrared ratiometric fluorescent probe Mito- diNO2 for the selective and sensitive analysis of Sec concentration fluctuations in living cells and in mice models under the stimulation of CS2. The probe can effectively accumulate in mitochondria and selectively detect the endogenous Sec concentrations in BRL 3A, RH-35, HL-7702, HepG2, and SMMC-7721 cell lines. The results indicate that CS2 exposure can lead to a decrease of Sec level and result in mitochondrial related acute inflammation. The exogenous supplement of Sec can protect cells from oxidative damage and reduce the symptoms of inflammation. We also establish CS2 induced acute and chronic hepatitis mice models to examine the tissue toxicity of CS2 and cytoprotection of Sec in liver. The organism can increase the concentration of Sec to deal with the damage caused by CS2 in acute hepatitis mice model. Also the exogenous supplement of Sec for the two mice models can effectively defend the CS2 induced liver damage. The real-time imaging of Sec concentrations in liver can be used to assess the degrees of liver injury during CS2 poisoning. The above applications make our probe a potential candidate for the clinical accurate diagnosis and treatment of CS2 poisoning.

Ratiometric Near-Infrared Fluorescent Probe for Synergistic Detection of Monoamine Oxidase B and Its Contribution to Oxidative Stress in Cell and Mice Aging Models.

As new biomarkers, monoamine oxidases (MAOs) play important roles in maintaining the homeostasis of biogenic amines via catalyzing the oxidation of biogenic amines to corresponding aldehydes with the generation of reactive oxygen species (ROS). MAOs have two isoforms, MAO-A and MAO-B. MAO-A is considered to be a major factor of neuropsychiatric and depressive disorders. However, MAO-B is thought to be involved in several neurodegenerative diseases. Therefore, to explore their distinct roles in different diseases, the selective detection of MAOs is essential. Herein, two new types of near-infrared (NIR) fluorescent probes, MitoCy-NH2 and MitoHCy-NH2, are provided for synergistic imaging of MAO-B and its contribution to oxidative stress in cells and in mice aging models. These probes are composed of three moieties: heptamethine cyanine as fluorophore, propanamide as recognition group, and triphenylphosphonium cation as mitochondrial targeting group. The amine oxidation and ß-elimination reaction can lead to obvious fluorescence increase and color changes from green to blue. The probe MitoHCy-NH2 can be used to synergistically detect MAO-B and its contribution to oxidative stress in the replicative senescence model. And the probe MitoCy-NH2 can offer ratiometric near-infrared fluorescence for the selective detection of MAO-B in the H2O2-induced cell aging model and in mice aging models. The results reveal that there are different MAO-B levels in different ages of mice models. MitoCy-NH2 also can evaluate therapeutic effects of pargyline and selegiline in mice models. The desirable analytical behaviors of our probes make them useful chemical tools for the selective detection of MAO-B and its contribution to oxidative stress in biosystems.

Associated Detection of Superoxide Anion and Mercury(II) under Chronic Mercury Exposure in Cells and Mice Models via a Three-Channel Fluorescent Probe.

As a cytotoxic heavy metal ion, mercury(II) ion (Hg2+) induces severe oxidative stress and further results in physiological dysfunction. Although mercury poisoning can be treated with many drugs, such as sodium selenite, the therapeutic effect is relatively poor, and it seems that the damage to human health continues. However, the interpretation for the pathogenesis has not been clarified yet. We supposed that the reason is attributed to Hg2+-caused intracellular oxidative stress. To confirm our hypothesis, we strived to design a three-channel ratio fluorescent probe, HCy-SeH, for superoxide anion (O2•-) and Hg2+ combined detection. O2•- is a vital precursor for other reactive oxygen species (ROS), which is involved in many physiological and pathological processes. However, until now there is no efficient chemical tool for O2•- and Hg2+ combined detection in cells and in vivo. The fluorescence response of our probe is initiated by a hydrogen abstraction reaction from the hydrocyanine fluorophore moiety. Once oxidized by O2•-, HCy-SeH recovers its π-conjugated system back to a heptamethine cyanine derivative, Cy-SeH. Cy-SeH coexists with its conjugate base, Cy═Se. One emits red fluorescence, and the other one emits green fluorescence. The response unit, -SeH, can trap Hg2+ via a Se-Hg antagonism reaction to afford an orange-emitting final product, Keto-Cy. The probe offers high selectivity and sensitivity toward O2•- and Hg2+. When applied for O2•- and Hg2+ detection in HEK 293 cells, the imaging results indicate that our probe can provide a combined response for O2•- and Hg2+ in real time and in situ. Flow cytometry analysis is well-consistent with the results from fluorescence imaging. When applied to image O2•- and Hg2+ in mice models, we find that Hg2+ dominantly accumulates in the kidney and induces a burst of O2•-. We confirm that chronic mercurialism can cause severe oxidative damage and renal fibrosis. HCy-SeH further provides a new information that, even when intracellular Hg2+ has been antagonized, the outbreak of O2•- caused by mercury poisoning still lasts.

A reversible fluorescent probe based on C[double bond, length as m-dash]N isomerization for the selective detection of formaldehyde in living cells and in vivo.

Formaldehyde (FA) is an endogenously produced reactive carbonyl species (RCS) through biological metabolic processes whose concentration is closely related to human health and disease. Noninvasive and real-time detection of FA concentration in organisms is very important for revealing the physiological and pathological functions of FA. Herein, we design and synthesize a reversible fluorescent probe BOD-NH2 for the detection of FA in living cells and in vivo. The probe is composed of two moieties: the BODIPY fluorophore and the primary amino group response unit. The probe undergoes an intracellular aldimine condensation reaction with FA and forms imine (C[double bond, length as m-dash]N) which will result in C[double bond, length as m-dash]N isomerization and rotation to turn-off the fluorescence of the probe. It is important that the probe can show a reversible response to FA. The probe BOD-NH2 has been successfully applied for detecting and imaging FA in the cytoplasm of living cells. BOD-NH2 is capable of detecting fluctuations in the levels of endogenous and exogenous FA in different types of living cells. The probe can be used to visualize the FA concentration in fresh hippocampus and the probe can further qualitatively evaluate the FA concentrations in ex vivo-dissected organs. Moreover, BOD-NH2 can also be used for imaging in mice. The above applications make our new probe a potential chemical tool for the study of physiological and pathological functions of FA in cells and in vivo.

Fluorescent chemical probes for accurate tumor diagnosis and targeting therapy.

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.

Wide-Acidity-Range pH Fluorescence Probes for Evaluation of Acidification in Mitochondria and Digestive Tract Mucosa.

The cells control their pH change in a very accurate range. pH plays important roles in cell autophagy and apoptosis. Previous evidence implies that the internal milieu of a tumor is acidified. Although the acidification in cells is investigated, the biological effects from multiple stimulating factors under the complex intracellular environment have not been thoroughly elaborated yet. Currently, there are few pH probes that perform in a wide acidity range, and a probe that is capable of measuring a wide pH range needs to be developed. Herein, we report two new fluorescent probes (BHNBD and CM-BHNBD) for the detection of mitochondrial and intramucosal acidification. The two probes respond to pH via an H+-driven TICT (twist intramolecular charge transfer) mechanism, and they can linearly report pH within a wide pH range: 7.00-2.00 following ∼148-fold fluorescence increase. The two probes also possess excellent membrane permeability, good photostability, and negligible cytotoxicity. The probes are successfully applied for quantifying the acidification in HeLa cells under the simultaneous stimulation of nutrient deprivation and oxidative stress. Our results demonstrate that the mitochondrial pH is in a dynamic fluctuating state during the acidification process, which suggests a potential cross-talk effect between cell autophagy and apoptosis. We also use the probes for quantifying the intramucosal pH variation in stomach and esophagus via manipulating cellular proton pump. The development of our probes is potentially expected to be used to monitor the intracellular/intramucosal acidification for biomedical research.

In situ quantification and evaluation of ClO-/H2S homeostasis in inflammatory gastric tissue by applying a rationally designed dual-response fluorescence probe featuring a novel H+-activated mechanism.

Homeostasis of ClO-/H2S plays a crucial role in the damage and repair of gastric tissue, but has rarely been investigated due to the challenge of in situ analysis in the highly acidic gastric environment. Herein, we designed a new H+-activated optical mechanism, involving controllable photoinduced electron transfer (PET) and switch of electron push-pull (SEPP), to develop the simple yet multifunctional probe (Z)-4-(2-benzylidenehydrazinyl)-7-nitrobenzo[c][1,2,5]oxadiazole (BNBD). First, the BNBD probe (Off) was protonated by the highly acidic media to trigger strong fluorescence (On). Then, the analytes ClO- and H2S reacted with the protonated BNBD, leading to ultrasensitive (ClO-: 2.7 nM and H2S: 6.9 nM) fluorescence quenching via the rapid oxidation of C[double bond, length as m-dash]N (50 s) and nitro reduction (10 s), respectively. With the logical discrimination by absorbance/colour (ClO-: 300 nm/colorless and H2S: 400 nm/orange), a strategy for the in situ quantification of ClO-/H2S in gastric mucosa and juice was developed. For the first time, the in situ quantitative monitoring of endogenous H2S and ClO-/H2S homeostasis as well as the pathologic manifestation in gastric mucosa were realized, thus overcoming the challenge of ClO-/H2S analysis under highly acidic conditions and enabling the in situ tissue quantification of ClO-/H2S. In combination with the assessment of mucosal damage, this study confirms the injurious/rehabilitative effects of ClO-/H2S on gastric mucosa (at 50-90 µm depth), which may facilitate the auxiliary diagnosis of stomach diseases induced by oxidative stress.