Fast detection of sodium dithionite in sugar using a xanthylium-based fluorescent probe.

Dithionite remained in the foodstuff may pose a great threat to the health of consumers. Three xanthylium-based probes were synthesized and their responses to dithionite were explored. Probe SH-1 could respond to dithionite selectively in PBS buffer (15% DMSO, 10 mM, pH = 7.4). Upon the addition of dithionite, the fluorescent emission of SH-1 at 684 nm dropped quickly (within 10 s) and the fluorescence decline was proportional to the concentration of dithionite (0-7.0 µM). The limit of detection was determined to be 0.139 µM. Then, the sensing mechanism was tentatively presented and the structure of resulted adduct (SH-1-SO3-) which was the reaction product of SH-1 and dithionite via a Micheal addition reaction followed by an oxidation reaction was verified. Moreover, white granulated sugar was subjected to the standard spike experiments and the results demonstrated a great potential of SH-1 for the quantitative monitoring of dithionite in foodstuffs.

Identification of the first selective bioluminescent probe for real-time monitoring of carboxylesterase 2 in vitro and in vivo.

Carboxylesterase (CES), a main hydrolysis enzyme family in the human body, plays a crucial role in drug metabolism. Among them, CES1 and CES2 are the primary subtypes, and each exhibits distinct distribution and functions. However, convenient and non-invasive methods for distinguishing them and the real-time monitoring of CES2 are relatively rare, hindering the further understanding of physiological functions and underlying mechanisms. In this study, we have designed, synthesized, and evaluated the first selective bioluminescent probe (CBP 1) for CES2 with high sensitivity, high specificity and rapid reactivity. This probe offers a promising approach for the real-time detection of CES2 and its dynamic fluctuations both in vitro and in vivo.

Clinically Translatable Solid-State Dye for NIR-II Imaging of Medical Devices.

Medical devices are commonly implanted underneath the skin, but how to real-time noninvasively monitor their migration, integrity, and biodegradation in human body is still a formidable challenge. Here, the study demonstrates that benzyl violet 4B (BV-4B), a main component in the FDA-approved surgical suture, is found to produce fluorescence signal in the first near-infrared window (NIR-I, 700-900 nm) in polar solutions, whereas BV-4B self-assembles into highly crystalline aggregates upon a formation of ultrasmall nanodots and can emit strong fluorescence in the second near-infrared window (NIR-II, 1000-1700 nm) with a dramatic bathochromic shift in the absorption spectrum of ≈200 nm. Intriguingly, BV-4B-involved suture knots underneath the skin can be facilely monitored during the whole degradation process in vivo, and the rupture of the customized BV-4B-coated silicone catheter is noninvasively diagnosed by NIR-II imaging. Furthermore, BV-4B suspended in embolization glue achieves hybrid fluorescence-guided surgery (hybrid FGS) for arteriovenous malformation. As a proof-of-concept study, the solid-state BV-4B is successfully used for NIR-II imaging of surgical sutures in operations of patients. Overall, as a clinically translatable solid-state dye, BV-4B can be applied for in vivo monitoring the fate of medical devices by NIR-II imaging.

Design, Synthesis, and Bioevaluation of Dexmedetomidine Prodrug.

Dexmedetomidine is commonly used in clinical practice as an anesthetic adjuvant and sedative. Unfortunately, major side effects include significant blood pressure fluctuation and bradycardia. Herein, we report the design and synthesis of four series of dexmedetomidine prodrugs aimed to alleviate hemodynamic fluctuations and simplify the administration procedure. From the in vivo experiments, all the prodrugs took effect within 5 min and did not cause significant recovery delay. The increase in blood pressure generated by one bolus of most of the prodrugs (14.57%-26.80%) was similar to that resulting from a 10 min infusion of dexmedetomidine (15.54%), which is significantly lower than the effect from a single dose of dexmedetomidine (43.55%). The decrease in heart rate induced by some prodrugs (-22.88% to -31.10%) was significantly alleviated compared with dexmedetomidine infusion (-41.07%). Overall, our work demonstrates that the prodrug strategy is useful to simplify administration procedures and mitigate hemodynamic fluctuations induced by dexmedetomidine.

New ε-N-thioglutaryl-lysine derivatives as SIRT5 inhibitors: Chemical synthesis, kinetic and crystallographic studies.

SIRT5 has been implicated in various physiological processes and human diseases, including cancer. Development of new highly potent, selective SIRT5 inhibitors is still needed to investigate disease-related mechanisms and therapeutic potentials. We here report new ε-N-thioglutaryllysine derivatives, which were designed according to SIRT5-catalysed deacylation reactions. These ε-N-thioglutaryllysine derivatives displayed potent SIRT5 inhibition, of which the potential photo-crosslinking derivative 8 manifested most potent inhibition with an IC50 value of 120 nM to SIRT5, and low inhibition to SIRT1-3 and SIRT6. The enzyme kinetic assays revealed that the ε-N-thioglutaryllysine derivatives inhibit SIRT5 by lysine-substrate competitive manner. Co-crystallographic analyses demonstrated that 8 binds to occupy the lysine-substate binding site by making hydrogen-bonding and electrostatic interactions with SIRT5-specific residues, and is likely positioned to react with NAD+ and form stable thio-intermediates. Compound 8 was observed to have low photo-crosslinking probability to SIRT5, possibly due to inappropriate position of the diazirine group as observed in SIRT5:8 crystal structure. This study provides useful information for developing drug-like inhibitors and cross-linking chemical probes for SIRT5-related studies.

A fluorescent probe for alkylating agents and its quantification of triflate as a genotoxic impurity.

The responses of a reaction-based fluorescent probe BI-Py towards alkyl halide, epoxide, carbonate, sulfate, sulphonate and triflate were evaluated and the probe achieved selective detection of ethyl triflate in acetonitrile with a LOD of 1.08 µM. BI-Py exhibited great potential for detecting triflate as a genotoxic impurity in drug substances.

A colorimetric and fluorometric probe for phenylhydrazine and its application in real samples.

A fluorescent probe for phenylhydrazine detection was developed with aldehyde as the recognition group and good selectivity towards phenylhydrazine over hydrazine, hydroxylamine and other amines was observed. Its application in real water samples and fast visualization of phenylhydrazine using a probe-loaded paper strip were demonstrated.

A Michael addition reaction-based fluorescent probe for malononitrile detection and its applications in aqueous solution, living cells and zebrafish.

It is highly desirable to detect malononitrile in organisms and human bodies owning to its inherent toxicity. With dicyanovinyl as the recognition site, a Michael addition reaction-based fluorescent probe Hcy-DCV was developed for malononitrile detection. A notable advantage of this probe is that it responds quickly to malononitrile without any additive to speed the sensing reaction. It has a good water solubility and the detection limit was determined to be 6.92 ppb in 100% aqueous solution. In particular, Hcy-DCV exhibited good selectivity towards malononitrile over other interfering substances including hydrazine and other active methylene compounds. The probe was applied successfully to quantitate malononitrile in pure water with satisfying recovery and relative standard deviation. Additionally, the ability of visualizing malononitrile by using probe-coated strip papers was displayed, which may facilitate the on-site detection of malononitrile. Moreover, the bioimaging of malononitrile in living H1975 cells and zebrafish larvae was also demonstrated. All the experimental results suggested the potential of Hcy-DCV for practical detection of malononitrile in both environmental and biological samples.

A selective and sensitive near-infrared fluorescent probe for real-time detection of Cu(i).

The disruption of copper homeostasis (Cu+/Cu2+) may cause neurodegenerative disorders. Thus, the need for understanding the role of Cu+ in physiological and pathological processes prompted the development of improved methods of Cu+ analysis. Herein, a new near-infrared (NIR) fluorescent turn-on probe (NPCu) for the detection of Cu+ was developed based on a Cu+-mediated benzylic ether bond cleavage mechanism. The probe showed high selectivity and sensitivity toward Cu+, and was successfully applied for bioimaging of Cu+ in living cells.

A novel dual-function fluorescent probe for the rapid detection of bisulfite and hydrogen peroxide in aqueous solution and living cells.

In this work, Hcy-OB, a novel hemicyanine-based biocompatible dual-function fluorescence probe for bisulfite and H2O2 detection is designed and synthesized. Based on a 1,4-addition reaction, Hcy-OB can be used for bisulfite detection with fast response, high sensitivity and low detection limit (120 nM). In addition, the probe is successfully applied to the detection of bisulfite in aqueous solution. Furthermore, Hcy-OB shows excellent performance for hydrogen peroxide detection with the oxidation of phenylboronic acid. Hcy-OB shows excellent selectivity to H2O2 over other interfering substances with detection limit of H2O2 is calculated to be 70 nM. Most importantly, due to its good cell membrane permeability and low cytotoxicity, Hcy-OB has been applied to monitor and image H2O2 in living cells and mice.

Gold Nanoclusters for NIR-II Fluorescence Imaging of Bones.

Fluorescence imaging in the second near-infrared window (NIR-II, 1000-1700 nm) holds great promise for deep tissue visualization. Development of novel clinical translatable NIR-II probes is crucial for realizing the medical applications of NIR-II fluorescence imaging. Herein, the glutathione-capped gold nanoclusters (AuNCs, specifically Au25 (SG)18 ) demonstrate highly efficient binding capability to hydroxyapatite in vitro for the first time. Further in vivo NIR-II fluorescence imaging of AuNCs indicate that they accumulate in bone tissues with high contrast and signal-background ratio. AuNCs are also mainly and quickly excreted from body through renal system, showing excellent ribs and thoracic vertebra imaging because of no background signal in liver and spleen. The deep tissue penetration capability and high resolution of AuNCs in NIR-II imaging render their great potential for fluorescence-guided surgery like spinal pedicle screw implantation. Overall, AuNCs are highly promising and clinical translatable NIR-II imaging probe for visualizing bone and bone related abnormalities.

A selective and sensitive near-infrared fluorescent probe for in vivo real time tracking of exogenous and metabolized hydrazine, a genotoxic impurity.

Hydrazine is a well-known genotoxic impurity which may be present in some important drugs, such as isoniazid and hydralazine. It may be ingested along with the drug or generated as a metabolite in the human body. Hence, monitoring the level of hydrazine in the human body is of great importance. A hemicyanine-based NIR fluorescent probe, Hcy-DB, was designed and synthesized for hydrazine detection. This probe exhibited a dramatic off-on NIR fluorescence response toward hydrazine in PBS-DMSO buffer and the detection limit was calculated to be 4.38 ppb. The bioimaging of hydrazine in living H1975 cells was successfully demonstrated. Moreover, the real time imaging of hydrazine, either injected as a foreign agent or generated as a metabolite of isoniazid, was demonstrated in mice and the results clearly disclosed the hydrazine level variation in the liver and kidneys. The injected exogenous hydrazine was mainly distributed in the kidneys and then excreted slowly. After the intragastric administration of isoniazid, hydrazine was quickly generated as a metabolite in the liver and reached a maximum in about 20 min, and then it was excreted slowly through the kidneys. Generally, the investigation provided a promising tool to monitor the level of hydrazine in vivo and thus help to evaluate and control its toxicity more rationally.

Design, Synthesis, and Activity Study of Water-Soluble, Rapid-Release Propofol Prodrugs.

In this work, a series of water-soluble propofol prodrugs were synthesized, and their propofol release rate and pharmacodynamic characteristics were measured. We found that inserting glycolic acid as a linker between propofol and the cyclic amino acid accelerated the release of propofol from prodrugs into the plasma while preserving its safety. In animal experiments, prodrugs (3e, 3g, and 3j) were significantly better than fospropofol (the only water-soluble propofol prodrug that has been used clinically) in terms of safety, onset, and duration time of anesthesia. Their molar dose, onset time, and anesthesia duration time were comparable to those of propofol, helping to maintain the clinical benefits of propofol. The experimental results showed the potential of such compounds as water-soluble prodrugs of propofol.

Fast Noninvasive Measurement of Brown Adipose Tissue in Living Mice by Near-Infrared Fluorescence and Photoacoustic Imaging.

Aberrant brown adipose tissue (BAT) metabolism is linked to obesity as well as other metabolic disorders. However, the paucity of imaging tools limits the study of in vivo BAT metabolism in animal models. The current work evaluated a heptamethine dye (CyHF-8) in living mice as a dual-modality BAT-avid molecular probe for two imaging approaches, including near-infrared fluorescence imaging (NIRF) and photoacoustic imaging (PAI). CyHF-8 exhibited favorable spectral properties in the near-infrared window (786/787/805 nm) and accumulated in the subcellular mitochondria of brown adipocytes. After intravenous injection of CyHF-8, NIRF and PAI were both capable of noninvasively detecting interscapular BAT at early time points in living mice. Quantitative analysis of NIRF and PAI images showed that CyHF-8 signals respond to dynamic BAT changes in mice stimulated by norepinephrine (NE) and in diabetic mice induced by streptozotocin (STZ). In summary, dual-modality NIRF/PAI probe CyHF-8 can be used for both NIRF and PAI to noninvasively assess BAT metabolism in living animals.

The synthesis and bioimaging of a biocompatible hydrogen sulfide fluorescent probe with high sensitivity and selectivity.

Hydrogen sulfide (H2S), a well-known poisonous gas, has been recognized as a critical endogenous gas transmitter in the past decade. To provide a quick and efficient detection method for hydrogen sulfide, a novel fluorescent probe DCI-NCN was designed based on an isophoronitrile scaffold featured with the cyanoxy group as the detection group. DCI-NCN shows promising results including high selectivity, high sensitivity, good linear relationship and pH stability in vitro. In addition, good biosystem imaging performance of DCI-NCN is observed in Kunming mice.

A sensitive and selective fluorescent probe for hydrazine with a unique nonaromatic fluorophore.

To achieve sensitive, selective and facile detection of hydrazine in environmental and biological systems, a fluorescent probe (Che-Dcv) with a unique nonaromatic fluorophore was developed. Upon hydrazine addition in 20% DMSO-PBS buffer (pH = 7.4, 10 mM, v/v) at room temperature, the probe displayed a strong emission at 496 nm along with a color change from brown-red to yellow. The response was attributed to the reaction of dicyanovinyl groups with hydrazine to afford hydrazone, which was supported by 1H NMR and HRMS. The detection limit of Che-Dcv for hydrazine was estimated to be as low as 1.08 ppb and good selectivity over amines including hydroxylamine was observed. Then, the potential of probe-coated test papers to detect hydrazine in solution and vapor phase was demonstrated. Moreover, the bioimaging of hydrazine in living H1975 cells was performed successfully.

An effective biocompatible fluorescent probe for bisulfite detection in aqueous solution, living cells, and mice.

Sulfur dioxide, an air pollutant, is easily hydrated to sulfites and bisulfites and extremely harmful to human health. On the other hand, endogenous sulfur dioxide is the fourth gasotransmitter. In view of the above, it is worth developing an effective method for the detection of these compounds. In this paper, a novel colorimetric fluorescent probe (Hcy-Mo), based on hemi-cyanine, for bisulfites is reported. Hcy-Mo shows excellent selectivity for bisulfites over various other species including cysteine, glutathione, CN-, and HS-, and undergoes 1,4-addition reactions at the C-4 atom of the ethylene group. The reaction can be completed in 30 s in a PBS buffer solution and displays high sensitivity (limit of detection is 80 nM) for bisulfites. Test paper experiments show that the probe can be used for bisulfite detection in aqueous solutions. In addition, Hcy-Mo exhibits excellent cell permeability and low cytotoxicity for the successful detection of bisulfites in living MDA-MB-231 cells and in living mice, implying that this probe would be of great benefit to biological researchers for investigating the detailed biological and pharmacological functions of bisulfites in biological systems.

Synthesis and evaluation of pyrazine and quinoxaline fluorophores for in vivo detection of cerebral tau tangles in Alzheimer's models.

A series of pyrazine and quinoxaline probes (QNNs) were synthesized and evaluated. The quinoxaline derivative 3b, with high affinity and selectivity for tau aggregates, favorable fluorescence turn-on capability and brain kinetics, was successfully applied to the detection of tau tangles both in vitro and in mice in vivo.

Synthesis and characterization of a glycine-modified heptamethine indocyanine dye for in vivo cancer-targeted near-infrared imaging.

Near-infrared (NIR) fluorescent sensors have emerged as promising molecular tools for cancer imaging and detection in living systems. However, cancer NIR fluorescent sensors are very challenging to develop because they are required to exhibit good specificity and low toxicity as an eligible contrast agent. Here, we describe the synthesis of a new heptamethine indocyanine dye (NIR-27) modified with a glycine at the end of each N-alkyl side chain, and its biological characterization for in vivo cancer-targeted NIR imaging. In addition to its high specificity, NIR-27 also shows lower cytotoxicity than indocyanine green, a nonspecific NIR probe widely used in clinic. These characteristics suggest that NIR-27 is a promising prospect as a new NIR fluorescent sensor for sensitive cancer detection.

A multifunctional heptamethine near-infrared dye for cancer theranosis.

Personalized oncology significantly relies on the development of cancer theranostic agents to integrate cancer therapeutics and diagnostics. Current most common strategy for development of such multifunctional agents requires multistep chemical conjugation with cancer targeted ligands, contrast agents and therapeutic agents. Here we report the chemical synthesis and biological characterization of a new heptamethine dye, termed as IR-808DB, natively with multifunctional characteristics of cancer targeting, near-infrared fluorescence imaging, and efficient anticancer activity. The tumor inhibition effect of IR-808DB is higher than that of cyclophosphamide (CTX) toward a broad spectrum of tumor xenograft models. These findings provide IR-808DB a promising prospect as a new cancer theranostic agent that would enable integration of cancer targeted therapeutics and diagnostics without requirement of multi-component chemical conjugation.