An ESIPT-based ratiometric fluorescent probe for detecting H2O2 in water environment and biosystems

A near-infrared fluorescent probe with thiadiazole unit as key skeleton for ICT and ESIPT mechanism and effective detection of Cu2

Fluorescent probe L-I was synthesized to demonstrate that 1,3,4-thiadiazole is an attractive moiety and could be utilized as positive hydrogen bond acceptor for excited state intramolecular proton transfer (ESIPT) processes, guider of electrons movement for intramolecular charge transfer (ICT) process and identify group for mental ions. Furthermore, dicyanoisophorone framework was employed to improve the fluorescence characteristics and near-infrared (NIR) fluorescent emission at 695 nm accompanied by a Stoke's shift as large as 260 nm was obtained. L-I could selectively detect Cu2+ over other analytes taking advantages of high sensitivity, fast response within 30 s and low detection limit (0.026 μM). More important, L-I exhibited good performance for detection of Cu2+ in actual water samples, food products, traditional Chinese medicine and for cell imaging which demonstrates practical significance in the fields of environmental monitor, food safety and biotechnology.

Discovery of a highly selective fluorescent probe for hydrogen peroxide and its biocompatibility evaluation and bioimaging applications in cells and zebrafish

As one of the most widely distributed reactive oxygen species in vivo, hydrogen peroxide plays divergent and important roles in cell growth, differentiation and aging. When the level of hydrogen peroxide in the body is abnormal, it will lead to genome mutation and induce irreversible oxidative modification of proteins, lipids and polysaccharides, resulting in cell death or even disease. Therefore, it is significant to develop a sensitive and specific probe for real-time detection of hydrogen peroxide in vivo. In this study, the response mechanism between hydrogen peroxide and probe QH was investigated by means of HRMS and the probe showed good optical properties and high selectivity to hydrogen peroxide. Note that the evaluating of probe biocompatibility resulted from cytotoxicity test, behavioral test, hepatotoxicity test, cardiotoxicity test, blood vessel toxicity test, immunotoxicity test and neurotoxicity test using cell and transgenic zebrafish models with more than 20 toxic indices. Furthermore, the detection performance of the probe for hydrogen peroxide was evaluated by multiple biological models and the probe was proved to be much essential for the monitoring of hydrogen peroxide in vivo.

Ratiometric luminescence detection of H2O2 in food samples using a terbium coordination polymer sensitized with 3-carboxyphenylboronic acid

A ratiometric luminescent probe was fabricated using adenosine monophosphate (AMP) as a bridging ligand and 3-carboxyphenylboronic acid (3-CPBA) as the sensitizer and functional ligand that allowed the probe to recognize hydrogen peroxide (H2O2). The probe was labeled AMP-Tb/3-CPBA. Adding H2O2 caused the nonluminescent 3-CPBA to be converted into 3-hydroxybenzoic acid, which strongly luminesces at 401 nm. This meant that adding H2O2 decreased the AMP-Tb/3-CPBA luminescence intensity at 544 nm and caused luminescence at 401 nm. The 401 and 544 nm luminescence intensity ratio (I401/I544) was strongly associated with the H2O2 concentration between 0.1 and 60.0 μM, and the detection limit was 0.23 μM. Dual emission reverse-change ratio luminescence sensing using the probe allowed environmental effects to be excluded and the assay to be very selective. We believe that the results pave the way for the development of new functionalized lanthanide coordination polymers for use in luminescence assays.

Dissecting lysosomal viscosity fluctuations in live cells and liver tissues with an ingenious NIR fluorescent probe

Viscosity is a pivotal component in the cell microenvironment, while lysosomal viscosity fluctuation is associated with various human diseases, such as tumors and liver diseases. Herein, a near-infrared fluorescent probe (BIMM) based on merocyanine dyes was designed and synthesized for detecting lysosomal viscosity in live cells and liver tissue. The increase in viscosity restricts the free rotation of single bonds, leading to enhanced fluorescence intensity. BIMM exhibits high sensitivity and good selectivity, and is applicable to a wide pH range. BIMM has near-infrared emission, and the fluorescent intensity shows an excellent linear relationship with viscosity. Furthermore, BIMM possessing excellent lysosomes-targeting ability, and can monitor viscosity changes in live cells stimulated by dexamethasone, lipopolysaccharide (LPS), and nigericin, and differentiate between cancer cells and normal cells. Noticeably, BIMM can accurately analyze viscosity changes in various liver disease models with HepG2 cells, and is successfully utilized to visualize variations in viscosity on APAP-induced liver injury. All the results demonstrated that BIMM is a powerful wash-free tool to monitor the viscosity fluctuations in living systems.

Advances in fluorescent probe development for bioimaging of potential Parkinson's biomarkers

Parkinson's disease (PD) is a common neurodegenerative disease. The clinical symptoms of PD are usually related to motor symptoms, including postural instability, rigidity, bradykinesia, and resting tremors. At present, the pathology of PD is not yet clear. Therefore, revealing the underlying pathological mechanism of PD is of great significance. A variety of bioactive molecules are produced during the onset of Parkinson's, and these bioactive molecules may be a key factor in the development of Parkinson's. The emerging fluorescence imaging technology has good sensitivity and high signal-to-noise ratio, making it possible to deeply understand the pathogenesis of PD through these bioactive molecules. Currently, fluorescent probes targeting PD biomarkers are widely developed and applied. This article categorizes and summarizes fluorescent probes based on different PD biomarkers, systematically introduces their applications in the pathological process of PD, and finally briefly elaborates on the challenges and prospects of these probes. We hope that this review will provide in-depth reference insights for designing fluorescent probes, and contribute to study of the pathogenesis and clinical treatment of PD.

Engineering an activatable fluorescent probe for studying ONOO- in pyroptotic process

Pyroptosis, a recently discovered form of programmed cell death, plays a pivotal role in oncological treatment. Howbeit, the mechanisms underlying pyroptosis in tumor treatment remain unclear. Previous research has demonstrated that the occurrence of pyroptosis generally accompanies a surge of reactive oxygen species (ROS) generation, with ONOO- being one of these ROS and closely linked to numerous diseases. Therefore, it is imperative to investigate the potential association between ONOO- and pyroptosis. Herein, a highly sensitive and rapidly responsive near-infrared (NIR) probe, Rd700-PN, is fabricated for exploring unrevealed relationships between ONOO- and pyroptosis. We successfully harness Rd700-PN to detect ONOO- fluctuation during cellular pyroptosis for the first time. Furthermore, the results demonstrate that Rd700-PN can scout the chemotherapeutic drug's induction ability of tumor pyroptosis in vivo. Notably, this study provides an excellent means to shed light on the correlation between ONOO- and pyroptosis and to screen antitumor drugs activating pyroptosis.

Screening and optimization of a water-soluble near-infrared fluorescent probe for drug-induced liver injury monitoring

Peroxynitrite (ONOO-) is a potential biomarker of drug-induced liver injury (DILI) and is involved in the process of DILI. Therefore, developing a reliable detection method for ONOO- will greatly contribute to ensuring drug safety and improving treatment efficiency. Here, based on the previous work, two kinds of NIR fluorescence probes PN and SPN were developed with phenyl-hydrazine as the ONOO- recognition group, which based on two fluorophores RN and SRN that are stable to ONOO-. A sensitive NIR probe SPN with good water solubility, low detection limit and good biocompatibility was selected through in vitro spectral property screening. Further experimental results show that there is a good linear relationship between the response intensity of probe SPN to ONOO- and the concentration of ONOO-, and the detection limit can reach 19.7 nM. At the cellular level, probe SPN can achieve a good and specific response to endogenous and exogenous ONOO-. Also, the probe SPN can be used for imaging and detection of DILI in zebrafish level and small animal level, indicating that probe SPN can be used as a powerful tool for diagnosis of DILI and efficacy evaluation of therapeutic drugs.

A robust activatable two-photon fluorescent probe for endogenous formaldehyde biomarker visualization diagnosis and evaluation of diabetes mellitus

Diabetes mellitus and its complications are one of the largest healthcare burdens in the world and are increasing every year. However, the lack of effective biomarkers and non-invasive real-time monitoring tools remains a great challenge for the early diagnosis of diabetes mellitus. Endogenous formaldehyde (FA) represents a key reactive carbonyl species in biological systems, and altered metabolism and functions of FA have been closely related to the pathogenesis and maintenance of diabetes. Among various noninvasive biomedical imaging techniques, the identification-responsive fluorescence (FL) imaging could greatly benefit the comprehensive multi-scale assessment of some diseases such as diabetes. Herein, we have designed a robust activatable two-photon probe DM-FA for the first highly selective monitoring of fluctuations in FA levels during diabetes mellitus. Through the density functional theory (DFT) theoretical calculations, we elucidated the rationality of the activatable fluorescent probe DM-FA turning on the FL before and after the reaction with FA. In addition, DM-FA has excellent high selectivity, high growth factor and good photostability in the process of recognizing FA. Due to the brilliant two-photon and one-photon FL imaging capabilities of DM-FA, it has been successfully used to visualize of exogenous and endogenous FA in cells and mice. Remarkably, as a powerful FL imaging visualization tool, DM-FA was introduced for the first time to visually diagnose and explore diabetes through the fluctuation of FA content. The successful application of DM-FA in two-photon and one-photon FL imaging experiments found elevated FA levels in high glucose-stimulated diabetic cell models. We successfully visualized upregulation of FA levels in diabetic mice and decreased of FA levels in diabetic mice scavenged by NaHSO₃ from multiple perspectives using multiple imaging modalities. This work may provide a novel strategy for the initial diagnosis of diabetes mellitus and the evaluation of the efficacy of drug therapy for treating diabetes mellitus, which will likely have a positive impact on clinical medicine.