Tumor Microenvironment Activatable Nanoprodrug System for In Situ Fluorescence Imaging and Therapy of Liver Cancer.

The development of new imaging and treatment nanoprodrug systems is highly demanded for diagnosis and therapy of liver cancer, a severe disease characterized by a high recurrence rate. Currently, available small molecule drugs are not possible for cancer diagnosis because of the fast diffusion of imaging agents and low efficacy in treatment due to poor water solubility and significant toxic side effects. In this study, we report the development of a tumor microenvironment activatable nanoprodrug system for the diagnosis and treatment of liver cancer. This nanoprodrug system can accumulate in the tumor site and be selectively activated by an excess of hydrogen peroxide (H2O2) in the tumor microenvironment, releasing near-infrared solid-state organic fluorescent probe (HPQCY-1) and phenylboronic acid-modified camptothecin (CPT) prodrug. Both HPQCY-1 and CPT prodrugs can be further activated in tumor sites for achieving more precise in situ near-infrared (NIR) fluorescence imaging and treatment while reducing the toxic effects of drugs on normal tissues. Additionally, the incorporation of hydrophilic multivalent chitosan as a carrier effectively improved the water solubility of the system. This research thus provides a practical new approach for the diagnosis and treatment of liver cancer.

Activatable fluorescent probes for early diagnosis and evaluation of liver injury.

With the increase in people's living standards, the number of patients suffering from liver injury keeps on increasing. Traditional diagnostic methods can no longer meet the needs of early and accurate diagnosis due to their limitations in application. However, fluorescent probes based on different fluorophores and nanomaterials have been gradually lighting up medical research due to their unique properties, such as high specificity and non-invasiveness. In addition, accurate identification of the different types of liver injury biomarkers can significantly improve the level of early diagnosis. Therefore, this review reviews the fluorescent probes used in the detection of biomarkers of liver injury over recent years and briefly summarizes the corresponding biomarkers of different types of liver injury. Impressively, this review also lists the structures and the response mechanisms of the different probes, and concludes with an outlook, suggesting directions in which improvements can be made. Finally, we hope that this review will contribute to the further development of fluorescent probes for the early diagnosis and assessment of liver injury.

The Application of Hydrogen Sulfide Fluorescent Probe in Food Preservation, Detection and Evaluation.

This work primarily reviewed the response mechanism of fluorescent probes for H2S detection in foodstuffs in recent years, as well as the methodologies employed for detecting foodstuffs. Firstly, the significance of studying H2S gas as an important signaling molecule is introduced. Subsequently, a review of the response mechanism of the scientific community on how to detect H2S in foodstuffs samples by fluorescent probe technology is carried out. Secondly, the methods commonly used for detecting foodstuffs samples are discussed, including the test strip method and the spiking recovery methods. Nevertheless, despite the significant advancements in this field, there remain some research gaps. Finally, the article identifies the remaining issues that require further attention in current research and proposes avenues for future investigation. More importantly, this work identifies the current limitations of research in this field and proposes future applications of fluorescent probes for H2S in assessing food freshness and determining food spoilage. Therefore, this review will provide robust technical support for the protection of consumer health and the advancement of the sustainable development of the food industry and also put forward some new ideas and suggestions for future research.

Rationally Constructed De Novo Fluorescent Nanosensor for Nitric Oxide Detection and Imaging in Living Cells and Inflammatory Mice Models.

For the early diagnosis and effective evaluation of treatment effects of inflammation, a de novo bioanalytical method is urgently needed to monitor the metabolite nitric oxide (NO) associated with inflammatory diseases. However, developing a reliable detection method with excellent water solubility, biocompatibility, long retention time, and blood circulation is still challenging. In this work, we reported for the first time a de novo host-guest self-assembled nanosensor CTA for the quantitative detection and visualization of NO levels in inflammatory models. CTA mainly consists of two parts: (i) an adamantyl-labeled guest small-molecule RN-adH containing a classical response moiety o-phenylenediamine for a chemical-specific response toward NO and fluorophore rhodamine B with excellent optical properties as an internal reference for self-calibration and (ii) a remarkable water-soluble and biocompatible supramolecular ß-cyclodextrin polymer (Poly-ß-CD) host. In the presence of NO, the o-phenylenediamine unit was reacted with NO at a low pH value of ∼7.0, accompanied by changes in the intensity of the two emission peaks corrected for each other and the change in fluorescence color of the CTA solution from fuchsia to pink. Furthermore, CTA was an effective tool for NO detection with a fast response time (∼60 s), high selectivity, and sensitivity (LOD: 22.3 nM). Impressively, the CTA nanosensor has successfully achieved the targeted imaging of NO in living inflammatory RAW 264.7 cells and mice models with satisfactory results, which can provide a powerful molecular tool for the visualization and assessment of the occurrence and development of NO-related inflammatory diseases in complex biosystems.

Activated Two-Photon Near-Infrared Ratiometric Fluorescent Nanoprobe for ONOO- Detection and Early Diagnosis and Assessment of Liver Injury.

Liver injury poses a serious threat to human health and growing evidence suggests that it is closely associated with a biomarker (peroxynitrite, ONOO-). Therefore, considering that the relationship of ONOO- levels with the occurrence and development of liver injury disease remains a challenge, an urgent need exists to develop a reliable and robust tool for its visual rapid diagnosis and assessment. Herein, a two-photon near-infrared (TP-NIR) ratiometric fluorescent nanoprobe (NTC) based on a fluorescence resonance energy transfer (FRET) strategy was designed, synthesized, and characterized, which had the advantages of good water solubility, low background interference, deep tissue penetration, and high imaging resolution. Specially, NTC was constructed by self-assembly of an alkynyl group of a small-molecule fluorescent probe (NR) via click chemistry grafting onto azide chitosan (natural polymeric nanomaterial). NR contained acceptor 1 (NIR fluorophore) and donor 3 (D-π-A structure of naphthalimide derivative fluorophore) with outstanding TP properties that could be activated by ONOO- for the ratiometric detection of ONOO-. Furthermore, in the presence of ONOO-, NTC exhibited a short response time (∼10 s) and high selectivity and sensitivity toward ONOO- with an excellent detection limit as low as 15.3 nM over other reactive oxygen/nitrogen species. Notably, NTC has been successfully employed for ONOO- detection and imaging in living HepG2 cells, liver injury mice tissues, and mice models with satisfactory results. Thus, the construction of this NTC nanoprobe can provide a robust molecule tool for enabling early diagnosis and assessment of liver injury in the future.

A Review for In Vitro and In Vivo Detection and Imaging of Gaseous Signal Molecule Carbon Monoxide by Fluorescent Probes.

Carbon monoxide (CO) is a vital endogenous gaseous transmitter molecule involved in the regulation of various physiological and pathological processes in living biosystems. In order to investigate the biological function of CO, many technologies have been developed to monitor the level of endogenous CO in biosystems. Among them, the fluorescence detection technology based on the fluorescent probe has the advantages of high sensitivity, excellent selectivity, simple operation, especially non-invasive damage to biological samples, and the possibility of real-time in situ detection, etc., which is considered to be one of the most effective and applicable detection techniques. Therefore, in the last few years, a lot of work has been carried out on the design, synthesis and in vivo fluorescence imaging studies of CO fluorescent probes. Furthermore, using fluorescent probes to detect the changes in CO concentrations in living cells and tissues as well as in organisms has been one of the hot research topics in recent years. However, it is still a challenge to rationally design CO fluorescent probe with excellent optical performance, structural stability, low background interference, good biocompatibility, and excellent water solubility. Therefore, this review focuses on the research progress of CO fluorescent probes in the detection mechanism and biological applications in recent years. However, this popular and leading topic has rarely been summarized comprehensively to date. Thus, the research progress of CO fluorescent probes in recent years is reviewed in terms of their design concept, detection mechanism, and their biological applications. In addition, the relationship between the structure and performance of the probes was also discussed. More significantly, we hope that more excellent optical properties fluorescent probes for gaseous transmitter molecule CO detection and imaging will overcome the current problems of high biotoxicity and limited water solubility in future.

Artificial Base zT as Functional "Element" for Constructing Photoresponsive DNA Nanomolecules.

In contrast to small molecules, DNA and RNA macromolecules can be accurately formulated with base "elements" abbreviated as A, T, U, C, and G. However, the development of functionally artificial bases can result in the generation of new biomaterials with unique properties and applications. Therefore, we herein report the design and synthesis of a photoresponsive base as a new functional or molecular "element" for constructing DNA nanomolecules. The new base is made by fusion of an azobenzene with a natural T base (zT). zT, a new molecular element, is not only the most size-expanded T analogue but also a photoresponsive base capable of specific self-assembly through hydrogen bonding. Our results showed that stable and selective self-assembly of double-stranded DNAs occurred through zT-A base pairing, but it could still be efficiently dissociated by light irradiation. The photoresponsive DNA bases will provide the versatility required for constructing desired DNA nanomolecules and nanodevices.

Rational Development of Near-Infrared Fluorophores with Large Stokes Shifts, Bright One-Photon, and Two-Photon Emissions for Bioimaging and Biosensing Applications.

Fluorophores with near-infrared emissions play a crucial role in numerous bioimaging and biosensing applications, owing to their deep penetration depths, low auto-fluorescence, and minimal tissue damages. Herein, the rational development of a new class of near-infrared fluorophores with bright one-photon and two-photon emissions at ≈740 nm, large Stokes shifts (≈80 nm), significant two-photon action absorption cross-section (≈185 GM at 820 nm), excellent water solubility, outstanding photostability, and low toxicity is reported. Their biological applications in mitochondrial labelling, deep tissue imaging, and H2 S detection in live cells and mice are also demonstrated. In addition, a rational design strategy for enlarging the Stokes shifts and enhancing two-photon emissions of these fluorophores is presented. These fluorophores will serve as a useful platform for developing novel imaging and sensing agents, and the design methodologies will inspire the molecular engineering of abundant high-performance near-infrared fluorophores.

Through-bond energy transfer-based ratiometric two-photon probe for fluorescent imaging of Pd(2+) ions in living cells and tissues.

Palladium can cause severe skin and eye irritation once it enters the human body. Ratiometric two-photon fluorescent probes can both eliminate interference from environmental factors and realize deep-tissue imaging with improved spatial localization. To quantitatively track Pd(2+) in biosystems, we report here a colorimetric and two-photon ratiometric fluorescent probe, termed Np-Rh-Pd, which consists of a two-photon fluorophore (naphthalene derivative with a D-π-A structure) and a rhodamine B dye. The two fluorophores are directly linked to form a two-photon ratiometric fluorescent probe for Pd(2+) based on a through-bond energy transfer (TBET) strategy. It exhibits highly efficient energy transfer (90%) with two well-resolved emission peaks (wavelength difference of 100 nm), which could efficiently diminish the cross talk between channels and is especially favorable for ratiometric bioimaging applications. A signal-to-background ratio of 31.2 was observed for the probe, which affords a high sensitivity for Pd(2+) with a detection limit of 2.3 × 10(-7) M. It was also found that acidity does not affect the fluorescent response of the probe to Pd(2+), which is favorable for its applications in practical samples. The probe was further used for fluorescence imaging of Pd(2+) ions in live cells and tissue slices under two-photon excitation, which showed significant tissue-imaging depths (90-270 µm) and a high resolution for ratiometric imaging.

Localizable and photoactivatable fluorophore for spatiotemporal two-photon bioimaging.

Photoactivatable probe-based fluorescent imaging has become an efficient and attractive technique for spatiotemporal microscopic studies of biological events. However, almost all previously reported photoactivatable organic probes have been based on hydrosoluble precursors, which have produced water-soluble active fluorophores able to readily diffuse away from the photocleavage site, thereby dramatically reducing spatial resolution. Hydroxyphenylquinazolinone (HPQ), a small organic dye known for its classic luminescence mechanism through excited-state intramolecular proton transfer (ESIPT), shows strong light emission in the solid state, but no emission in solution. In this work, HPQ was employed as a precursor to develop a localizable, photoactivatable two-photon probe (PHPQ) for spatiotemporal bioimaging applications. After photocleavage, PHPQ releases a precipitating HPQ fluorophore which shows both one-photon and two-photon excited yellow-green fluorescence, thereby producing a localizable fluorescence signal that affords high spatial resolution for bioimaging, with more than 200-fold one-photon and 150-fold two-photon fluorescence enhancement.

An efficient ratiometric fluorescent probe for tracking dynamic changes in lysosomal pH.

Lysosomes are acidic organelles (approximately pH 4.5-5.5) and tracking the changes in lysosomal pH is of great biological importance. To address this issue, quite a few of fluorescent probes have been developed. However, few of these probes can realize the tracking of dynamic changes in lysosomal pH. Herein, we report a new lysosome-targeted ratiometric fluorescent probe (FR-Lys) by hybridizing morpholine with a xanthane derivative and an o-hydroxy benzoxazole group. In this probe, the morpholine group serves as a targeting unit for lysosome, the xanthane derivative exhibits a pH-modulated open/close reaction of the spirocycle, while the o-hydroxy benzoxazole moiety shows a pH modulated excited-state intramolecular proton transfer (ESIPT) process. Such a design affords the probe a ratiometric fluorescence response towards pH with pH values ranging from 4.0 to 6.3. The response of the probe to pH was fast and reversible with high selectivity. Moreover, this probe possesses further advantages such as easy synthesis, high photostability and low cytotoxicity. These features are favorable for tracking dynamic pH changes in biosystems. It was then applied for dynamic imaging pH changes in lysosomes with satisfactory results.

Molecular engineering of a TBET-based two-photon fluorescent probe for ratiometric imaging of living cells and tissues.

In contrast to one-photon microscopy, two-photon probe-based fluorescent imaging can provide improved three-dimensional spatial localization and increased imaging depth. Consequently, it has become one of the most attractive techniques for studying biological events in living cells and tissues. However, the quantitation of these probes is primarily based on single-emission intensity change, which tends to be affected by a variety of environmental factors. Ratiometric probes, on the other hand, can eliminate these interferences by the built-in correction of the dual emission bands, resulting in a more favorable system for imaging living cells and tissues. Herein, for the first time, we adopted a through-bond energy transfer (TBET) strategy to design and synthesize a small molecular ratiometric two-photon fluorescent probe for imaging living cells and tissues in real time. Specifically, a two-photon fluorophore (D-π-A-structured naphthalene derivative) and a rhodamine B fluorophore are directly connected by electronically conjugated bond to form a TBET probe, or Np-Rh, which shows a target-modulated ratiometric two-photon fluorescence response with highly efficient energy transfer (93.7%) and two well-resolved emission peaks separated by 100 nm. This novel probe was then applied for two-photon imaging of living cells and tissues and showed high ratiometric imaging resolution and deep-tissue imaging depth of 180 µm, thus demonstrating its practical application in biological systems.

Alkyne-functionalized superstable graphitic silver nanoparticles for Raman imaging.

Noble metals, especially gold, have been widely used in plasmon resonance applications. Although silver has a larger optical cross section and lower cost than gold, it has attracted much less attention because of its easy corrosion, thereby degrading plasmonic signals and limiting its applications. To circumvent this problem, we report the facile synthesis of superstable AgCu@graphene (ACG) nanoparticles (NPs). The growth of several layers of graphene onto the surface of AgCu alloy NPs effectively protects the Ag surface from contamination, even in the presence of hydrogen peroxide, hydrogen sulfide, and nitric acid. The ACG NPs have been utilized to enhance the unique Raman signals from the graphitic shell, making ACG an ideal candidate for cell labeling, rapid Raman imaging, and SERS detection. ACG is further functionalized with alkyne-polyethylene glycol, which has strong Raman vibrations in the Raman-silent region of the cell, leading to more accurate colocalization inside cells. In sum, this work provides a simple approach to fabricate corrosion-resistant, water-soluble, and graphene-protected AgCu NPs having a strong surface plasmon resonance effect suitable for sensing and imaging.

Bispyrene-fluorescein hybrid based FRET cassette: a convenient platform toward ratiometric time-resolved probe for bioanalytical applications.

Pyrene excimer possesses a large Stokes shift and long fluorescence lifetime and has been widely applied in developing time-resolved biosensing systems to solve the autofluorescence interference problems in biological samples. However, only a few of pyrene excimer-based small molecular probes have been reported so far. Ratiometric probes, on the other hand, can eliminate interferences from environmental factors such as instrumental efficiency and environmental conditions by a built-in correction of the dual emission bands but are ineffective for endogenous autofluorescence in biosystems. In this work, by combining the advantages of time-resolved fluorescence technique with ratiometric probe, we reported a bispyrene-fluorescein hybrid FRET cassette (PF) as a novel ratiometric time-resolved sensing platform for bioanalytical applications, with pH chosen as a biorelated target. The probe PF showed a fast, highly selective, and reversible ratiometric fluorescence response to pH in a wide range from 3.0 to 10.0 in buffered solution. By employing time-resolved fluorescence technique, the pH-induced fluorescence signal of probe PF can be well-discriminated from biological autofluorescence background, which enables us to detect pH in a range of 4.0-8.0 in cell media within a few seconds. It has also been preliminarily applied for ratiometric quantitative monitoring of pH changes in living cells with satisfying results. Since many fluorescein-based fluorescence probes have been developed, our strategy might find wide applications in design ratiometric time-resolved probes for detection of various biorelated targets.

Construction of an effective near-infrared fluorescence "turn-on" probe for hydrogen sulfide detection and imaging in living inflammatory cell and zebrafish models.

Hydrogen sulfide (H2S) can act as a gaseous signaling mediator closely associated with inflammation development. In this work, we designed a fluorescence turn-on near-infrared (NIR) fluorescent probe CIT-H2S based on Intermolecular Charge Transfer (ICT) for the detection of H2S in living inflammatory cells and zebrafish. On this basis, a dicyanoisophorone fluorophore was chosen as the fluorescence signal reporting group of CIT-H2S, and an azide group was constructed as the recognition group of H2S. CIT-H2S is characterized by high selectivity and sensitivity for H2S over other interference species. The fluorescence intensity at 661 nm showed good linearity in the range of H2S concentration from 0 to 10 µM, with an excellent limit of detection (LOD) as low as 81.52 nM. Impressively, CIT-H2S has been visualized for detecting H2S in drug-induced inflammatory cell and zebrafish models, thus indicating that CIT-H2S is a robust tool with the ability to study the occurrence and development of hydrogen sulfide and inflammation.

A high-fidelity dual-channel fluorescence probe for benzoyl peroxide detection and toxicity early warning in food, zebrafish, and mice.

Benzoyl peroxide (BPO), as a widely used organic peroxide, has attracted widespread attention from all sectors of society for its environmental hazards and potential risks to human health. Herein, we employed a Förster resonance energy transfer (FRET) strategy to construct a novel ratiometric fluorescent probe CY-DCI for BPO detection in food, zebrafish, and mice. Specifically, a hemicyanine fluorophore and a dicyanoisophorone fluorophore were connected with a piperazine group as donor and acceptor, respectively, and an olefinic unsaturated bond as the reaction site. CY-DCI has favorable selectivity and an excellent detection limit as low as 58.1 nM, and the recovery rates for real-sample detection ranged from 95.8 % to 104 %, with relative standard deviations (RSD) less than 2.58 %. To further improve its practicality, silica gel plates and test strips containing CY-DCI (0-50 µM) were developed for naked-eye detection of BPO with satisfactory results. Additionally, this novel probe was then applied for ratiometric imaging of living zebrafish and mice and showed high ratiometric imaging resolution in the green and red channels, thus demonstrating its practical application for BPO detection and toxicity early warning in food and biosystems.

Construction of a double-increasing emission fluorescent probe and its application in food detection of benzoyl peroxide and biosystem imaging.

In this work, based on the Förster resonance energy transfer (FRET) mechanism strategy, a new dual-increasing emission proportional near-infrared (NIR) fluorescent probe Lay-1 was designed for fast benzoyl peroxide (BPO) detection in real food samples and biosystems. Specifically, it employed a naphthylimide derivative and a NIR fluorophore dicyanoisophorone derivative as the energy transfer donor and acceptor, respectively, and a phenylboronic acid (Ph-B(OH)2) as the responding group of BPO. In addition, the results exhibited that the fluorescence color of Lay-1 was changed from red to orange in the absence and the presence of BPO with a fast response time (∼120 s), high sensitivity, and an excellent limit of detection as low as 60.8 nM. Impressively, Lay-1 has been successfully used for BPO detection in real food samples and biosystems with satisfactory results. Therefore, Lay-1 can be a robust molecular tool to further investigate the physiological and pathological function of BPO.

Nanomaterials-based aptasensors for rapid detection and early warning of key food contaminants: A review.

The frequent occurrence of food safety incidents has aroused public concern about food safety and key contaminants. Foodborne pathogen contamination, pesticide residues, heavy metal residues, and other food safety problems will significantly impact human health. Therefore, developing efficient and sensitive detection method to ensure food safety early warning is paramount. The aptamer-based sensor (aptasensor) is a novel analytical tool with strong targeting, high sensitivity, low cost, etc. It has been extensively utilized in the pharmaceutical industry, biomedicine, environmental engineering, food safety detection, and in other diverse fields. This work reviewed the latest research progress of aptasensors for food analysis and detection, mainly introducing their application in detecting various key food contaminants. Subsequently, the sensing mechanism and performance of aptasensors are discussed. Finally, the review will examine the challenges and opportunities related to aptasensors for detecting major contaminants in food, and advance implementation of aptasensors in food safety and detection.

Molecular engineering of a new method for effective removal of cadmium from water.

Cadmium (Cd) is a widespread and highly toxic environmental pollutant, seriously threatening animal and plant growth. Therefore, monitoring and employing robust tools to enrich and remove Cd from the environment is a major challenge. In this work, by conjugating a fluorescent indicator (CCP) with a functionalized glass slide, a special composite material (CCPB) was constructed to enrich, remove, and monitor Cd2+ in water rapidly. Then Cd2+ could be effectively eluted by immersing the Cd-enriched CCPB in an ethylenediaminetetraacetic acid (EDTA) solution. With this, the CCPB was continuously reused. Its recovery of Cd2+was above and below 100 % after multiple uses by flame atomic absorption spectrometry (FAAS), which was excellent for practical use in enriching and removing Cd2+ in real aqueous samples. Therefore, CCPB is an ideal material for monitoring, enriching, and removing Cd2+ in wastewater, providing a robust tool for future practical applications of Cd enrichment and removal in the environment.

Neo-construction of a SO2-tunable near-infrared ratiometric fluorescent probe for high-fidelity diagnosis and evaluation hazards of Cd2+-induced liver injury.

Cadmium-contaminated water and food are seriously hazardous to the human health, especially liver injury. To understand the entanglement relationship between cadmium ion (Cd2+)-induced liver injury and the biomarker sulfur dioxide (SO2), a reliable bioanalytical tool is urgently needed, detecting SO2 to diagnose and evaluate the extent of liver injury in vivo. Herein, based on the Förster resonance energy transfer (FRET) mechanism, a novel SO2-tunable NIR ratiometric fluorescent probe (SMP) was developed, it was used to diagnose and treat liver injury induced by Cd2+ in biosystems. Specifically, it was constructed by conjugating a NIR dicyanoisophorone with a NIR benzopyranate as the donor and acceptor, respectively, and the ratiometric response of SO2- regulated by the Michael addition reaction. In addition, SMP exhibits rapid reaction time (<15 s), two well-resolved emission peaks (68 nm) with less cross-talk between channels for high imaging resolution, superior selectivity, and low limit of detection (LOD=80.3 nM) for SO2 detection. Impressively, SMP has been successfully used for intracellular ratiometric imaging of Cd2+-induced SO2 and diagnostic and therapeutic evaluation in liver injury mice models with satisfactory results. Therefore, SMP may provide a powerful molecular tool for revealing the occurrence and development relationship between SO2 and Cd2+-induced liver injury. ENVIRONMENTAL IMPLICATION: Cadmium ions are one of the well-known toxic environmental pollutants, which are enriched in the human body through inhalation of cadmium-contaminated air or from the food chain, leading to damage in various organs, especially liver injury. Therefore, we developed a novel fluorescent probe that can specifically detect SO2 in Cd2+-induced liver injury, which is critically important for the diagnosis and evaluation of Cd2+-induced liver injury diseases. The specific detection of SO2 of this probe has been successfully demonstrated in live HepG2 cells and Cd2+-induced liver injury mice.