Naphthalimide Fluorophore Research Articles

A fluorescent pH probe for evaluating the freshness of chicken breast meat

A fluorescent probe, Nap-MOR, based on the naphthalimide fluorophore, was designed and developed for pH measurement in aqueous solutions. Nap-MOR had a close linear relationship between fluorescence intensity and pH, in the range 4.5–8, which covers the full range of pH found in normal fresh, defective and spoiled meat. pH measurement with Nap-MOR was free from interference by a wide range of ions and biochemicals found in meat and the results were not significantly different in comparison with a pH meter. Therefore, Nap-MOR is a robust and convenient way to evaluate the freshness of chicken breast meat by measuring its pH.

A biomarker (ONOO-)-activated multicolor fluorescent probe for early detection and assessment of arthritis

To understand the entangled relationship between reactive oxygen species (ROS) and arthritis, it is of great interest to urgently need an effective bioanalytical method to detect biomarker peroxynitrite (ONOO-) of arthritis in vivo. In contrast to the previously reported ONOO- fluorescent probes, multicolor fluorescent probe could be applied to complex environments for multi-component analysis and provide multichannel imaging results. However, multicolor fluorescent probes for ONOO- detecting have not been reported so far. Herein, an ONOO--activated multicolor fluorescent probe (MULTI-ONOO) based on FRET was developed for quantitative detecting and visualization of ONOO- levels in arthritis. This probe mainly contained an acceptor (near-infrared xanthane fluorophore) and a donor (naphthalimide fluorophore). In the presence of ONOO-, the oxonium ion undergoes a strong nucleophilic response between ONOO- and xanthane to generate coumarin (CM) and naphthimide (NP) fluorophores with multicolor signal output. Impressively, MULTI-ONOO has a rapid response time (~20 s) and outstanding detection limits as low as 11.6 nM. Finally, this probe was successfully adopted to detect endogenous ONOO- in living cells, arthritis tissues and rat model. Thus, this ONOO--activated multicolor probe could provide a robust tool for investigating the role of ONOO- between in different inflamed diseases.

A supersensitive fluorescent probe for biothiols by regulating the click reaction and its application in glutathione detection in food samples

A new fluorescent molecular probe (NAM2) with extending conjugation system between the recognition group and naphthalimide fluorophore group was developed for selective and sensitive detection of biothiols. The conjugation system of a phenyl ring with the naphthalimide group improved the efficiency of photoinduced electron transfer (PET). The molecular probe showed a supersensitive “off-on’’ response to glutathione (GSH) and homocysteine (Hcy), and it allowed detecting GSH and Hcy linearly in a range of 0–3 μM with detection limits of 0.0011 μM and 0.0032 μM, respectively. Significantly, the new sensor was applied in accurate detection of GSH in vegetables and fruits with recoveries of 87.26–96.72% (RSDs<3.5%, n = 3), and it was validated by a phthalaldehyde-derivatisation method. The fluorescence spectrometry based on the sensor NAM2 is a high-quality and promising analytical tool for GSH analysis in food samples.

Design of a naphthalimide-based probe for acrolein detection in foods and cells

Acrolein is a highly toxic agent that can be generated exogenously and endogenously. Therefore, a highly specific and sensitive probe for acrolein with potential applications in acrolein detection must be developed. In this research, a novel fluorescent probe named “probe for acrolein detection” (Pr-ACR) was designed and synthesized based on a naphthalimide fluorophore skeleton, and a thiol group (-SH) was introduced into its structure for acrolein recognition. The -SH traps acrolein via Michael addition and the resultant interaction product of the probe inhibits the photoinduced electron transfer process and produce a strong fluorescence at 510 nm. The probe showed high sensitivity and specificity for acrolein. HPLC-MS/MS analysis verified that it can be used to quantify acrolein in foods, such as soda crackers, red wine, and baijiu, with a fluorescence spectrophotometer. After methyl esterification, the methyl esterified probe (mPr-ACR) successfully visualised acrolein in Hela cells under a laser scanning confocal microscope. This finding proved that Pr-ACR and mPr-ACR are potential tools for the detection and visualisation of acrolein from different sources.

Photodiagnosis and photodynamic effects of bacteriochlorin-naphthalimide conjugates on tumor cells and mouse model.

Photo-induced cytotoxicity and antitumor activity of a series of dual function agents for photodynamic therapy (PDT) and fluorescent imaging based on bacteriochlorin photosensitizer conjugated with various naphthalimide fluorophores was studied in vitro using murine tumor cells of S37 sarcoma and in vivo on mice bearing murine S37 sarcoma. Upon irradiation at the absorption maximum of the photosensitizer, the activity of conjugates was as high as in the case of individual bacteriochlorin, while an additional excitation of the naphthalimide fragment led to an increase in the PDT efficacy due to resonance energy transfer from the fluorophore to photosensitizer. The fluorescence contrast and specific cytotoxic activity measurements indicate that the conjugate of bacteriochlorin with 3,4-dimethoxestyrene-substituted naphthalimide is the most promising agent for the application as theranostic in PDT.

An acid-base responsive linear-cyclic polymer rotaxane molecular shuttle with fluorescence signal output

The preparation of intelligent-responsive materials with controllable topology structure has long been a significant objective for chemists in the field of materials science. In this paper, we designed and prepared a linear-cyclic reversible topological structure polymer based on the bistable [1]rotaxane molecular shuttle. A ferrocene-functionalized [1]rotaxane and naphthalimide fluorophore group are introduced into the both ends of the polymer, which exhibit distance-induced photo-electron transfer effect. The structural transformation between linear and cyclic state of polymer is demonstrated by simple acid-base stimuli, accompanying visual fluorescence changes. The transformation process was characterized by 1H NMR spectra and fluorescence spectra. This work provides a novel strategy to construct functionalized polymers with topological structure.

Fluorescence Probe for Imaging N-Methyl-d-aspartate Receptors and Monitoring GSH Selectively Using Two-Photon Microscopy.

N-Methyl-d-aspartate (NMDA) is an excitotoxic amino acid used to identify a specific subset of glutamate receptors. The activity of NMDA receptors is closely related to the redox level of the biological system. Glutathione (GSH) as an antioxidant plays a key role with regard to modulation of the redox environment. In this work we designed and developed a GSH-specific fluorescent probe with the capability of targeting NMDA receptors, which was composed of a two-photon naphthalimide fluorophore, a GSH-reactive group sulfonamide, and an ifenprodil targeting group for the NMDA receptor. This probe exhibited high selectivity toward GSH in comparison to other similar amino acids. Two-photon fluorescence microscopy allowed this probe to successfully monitor GSH in neuronal cells and hippocampal tissues with an excitation at 750 nm. It could serve as a potential practical imaging tool to explore the function of GSH and related biological processes in the brain.

The Mechanochemical Release of Naphthalimide Fluorophores from β-Carbonate and β-Carbamate Disulfide-Centered Polymers

The covalent attachment of cargo molecules (e.g., drugs and fluorophores) in β-position to a disulfide moiety through carbamate and carbonate bonds finds many applications in responsiverelease syst...

A smart TP-FRET-based ratiometric fluorescent sensor for bisulfite/formaldehyde detection and its imaging application

Bisulfite (HSO3−) and formaldehyde (FA) are hazardous environmental pollutants that pose serious risks to human health. Herein, we report for the first time a novel TP-FRET-based TP-ratiometric reversible fluorescence sensor NPXH, which is based on combining TP naphthalimide fluorophore with a deep red-emitting xanthene fluorophore via a nonconjugated linker, for reversible detection of bisulfite/formaldehyde. In presence of HSO3−, NPXH shows a significant ratio enhancement (∼6-fold) in I535/I630, ultra-fast response (less than 8 s) and super low detection limit (7.48 nM). In addition, the fluorescence signal of NPXH is easily and rapidly recovered by FA within 1 min. More impressively, NPXH has shown excellent detection capability in food and water samples and has been successfully applied to HSO3−/FA detection in liver tissue, zebrafish and mice.

Multi-functional fluorescence cellulose composites based on a modified amphiphilic waterborne polyurethane by covalent suspension of the triazine groups

Multi-functional fluorescent composites with maximal fluorescence emission are desirable in advanced materials and composites. We synthesized an amphiphilic fluorescent waterborne polyurethane (WPU) by covalent linking of a naphthalimide fluorophore (NF) containing a monochlorotriazine group. The synergy of the NF and triazine group improved absorption in the A- and B-range ultraviolet (UV). We obtained corresponding fluorescent cellulose composites by coating a cellulose matrix with modified amphiphilic WPU. We measured the fluorescence intensity and fluorescence quantum yield of modified WPU emulsions and films that contained various proportions of NF. In accordance with increasing proportion of NF in the WPU–NF, the emission peak exhibited a gradual bathochromic shift and the fluorescence intensity considerably increased. Compared with a physical blend of WPU and NF, covalent linking greatly enhanced the fluorescence intensity and fluorescence quantum yield of WPU–NF films. When the proportion of the fluorescent group was 0.200% and 0.400% (w/w), the fluorescence intensities of the covalently cross-linked polymer were 4.29× and 7.27× higher, respectively, than those of the physically mixed polymers. The cellulose composites exhibited excellent fluorescence and good UV protection. The monochlorotriazine formed covalent bonds with the cellulose matrix and in so doing improved the bonding stability. Our amphiphilic fluorescent polyurethane polymer and fluorescent cellulose composites have great potential for applications in advanced composites, biomaterials, and UV protection materials.

Palladium Probe Consisting of Naphthalimide and Ethylenediamine for Selective Turn-On Sensing of CO and Cell Imaging.

An assay to detect carbon monoxide (CO), one of the gaseous signaling molecules, has been prepared using a new palladium complex probe. The ethylenediamine group linked to the naphthalimide fluorophore coordinates to Pd(II) which intramolecularly quenches the emission. Upon treatment with CO, the absorbance of the turn-on fluorescent sensor changes due to the formation of a complex between Pd(II) and CO at room temperature in a phosphate buffer. As the concentration of CO increases, the probe peak emission intensity at 527 nm gradually increases. Other analyte controls, such as K+, Mg2+, Al3+, Zn2+, Cr3+, Hg2+, Fe3+, alanine, glycine, leucine, lysine, serine, threonine, tyrosine, F-, Cl-, Br-, NO, NO2-, NO3-, HCO3-, CH3COO-, H2O2, •OH, and tBuOO•, exhibit no significant effect on emission intensity. The response time of the probe to CO was quite fast because of the relatively weak coordination of Pd(II) to the pendent ethylenediamine group. The Pd probe is capable of detecting CO in aqueous buffer as well as in living cells with high selectivity and stability, providing a potential real-time indicator for studying CO-involved reactions in biological systems.

Carbon Dot/Naphthalimide Based Ratiometric Fluorescence Biosensor for Hyaluronidase Detection.

Bladder cancer is the leading cause of death in patients with genitourinary cancer. An elevated level of hyaluronidase (HAase) was found in bladder cancer, which acts as an important biomarker for the early diagnosis of bladder cancer. Hence, there is a need to develop a simple enzymatic assay for the early recognition of HAase. Herein, we report a simple, sensitive, and ratiometric fluorescence assay for HAase detection under physiological conditions. The fluorescence assay was constructed by the adsorption of cationic carbon dots and positively charged naphthalimide on negatively charged hyaluronic acid and the development of a Förster resonance energy transfer (FRET) mechanism from carbon dots to a naphthalimide fluorophores. The hyaluronidase enzyme cleaves the hyaluronic acid in this assay, and breaking down the FRET mechanism induces ratiometric changes. A detection limit of 0.09 U/mL was achieved, which is less than the HAase level found in normal human body fluids. Moreover, this assay may be used for diagnosing HAase-related diseases.

An assembly-regulated SNAP-tag fluorogenic probe for long-term super-resolution imaging of mitochondrial dynamics

Super-resolution fluorescence microscopy has emerged as a powerful tool for studying mitochondrial dynamics in living cells. However, the lack of photostable and chemstable probe makes long-term super-resolution imaging of mitochondria still a challenging work. Herein, we reported a 4-azetidinyl-naphthliamide derived SNAP-tag probe AN-BG exhibiting excellent fluorogenicity and photostability for long-term super-resolution imaging of mitochondrial dynamics. The azetidinyl group and naphthalimide fluorophore are in a flat conformation which can effectively suppress twisted intramolecular charge transfer and then effectively improve the brightness and photostability. This planarized molecular structure is conducive to the formation of fluorescence-quenched J-aggregates, and the protein labeling process will depolymerize the probes and restore fluorescence. Fluorescent labeling mitochondrial inner membrane proteins via SNAP tags overcomes the shortcomings that variations in mitochondrial inner membrane potential will release probes attached to mitochondria by electrostatic interactions. Therefore, AN-BG realized the stable labeling of mitochondria and the long-term imaging of mitochondrial dynamics under super-resolution microscopy.

Naphthalimide-based probe with strong two-photon excited fluorescence and high specificity to cell membranes

By introducing a long alkyl chain and a quaternary ammonium on the two sides of naphthalimide fluorophore, we have developed an amphiphilic probe NA with a high specificity toward cell membranes and strong two-photon excited fluorescence. Due to these advantageous features, NA demonstrates wash-free staining and high quality two-photon imaging of live cells.

Covalent and non-covalent albumin binding of Au(i) bis-NHCs via post-synthetic amide modification.

Recent decades have witnessed the emergence of Au(i) bis-N-heterocyclic carbenes (NHCs) as potential anticancer agents. However, these systems exhibit little interaction with serum proteins (e.g., human serum albumin), which presumably impacts their pharmacokinetic profile and tumor exposure. Anticancer drugs bound to human serum albumin (HSA) often benefit from significant advantages, including longer circulatory half-lives, tumor targeted delivery, and easier administration relative to the drug alone. In this work, we present Au(i) bis-NHCs complexes, 7 and 9, capable of binding to HSA. Complex 7 contains a reactive maleimide moiety for covalent protein conjugation, whereas its congener 9 contains a naphthalimide fluorophore for non-covalent binding. A similar drug motif was used in both cases. Complexes 7 and 9 were prepared from a carboxylic acid functionalized Au(i) bis-NHC (complex 2) using a newly developed post-synthetic amide functionalization protocol that allows coupling to both aliphatic and aromatic amines. Analytical, and in vitro techniques were used to confirm protein binding, as well as cellular uptake and antiproliferative activity in A549 human lung cancer cells. The present findings highlight a hitherto unexplored approach to modifying Au(i) bis-NHC drug candidates for protein ligation and serve to showcase the relative benefits of covalent and non-covalent HSA binding.

A GSH-responsive PET-based fluorescent probe for cancer cells imaging

An efficient PET-based probe, in which the ferrocene quencher and the naphthalimide fluorophore are linked by a disulfide bond, has been developed. This probe can be activated by GSH with fluorescence a turn-on response for blocking the PET process. In addition, it was successfully applied for distinguishing cancer cells from normal cells

A FRET-ICT Dual-Modulated Ratiometric Fluorescence Sensor for Monitoring and Bio-Imaging of Cellular Selenocysteine.

Since the fluctuation of cellular selenocysteine (Sec) concentration plays an all-important role in the development of numerous human disorders, the real-time fluorescence detection of Sec in living systems has attracted plenty of interest during the past decade. In order to obtain a faster and more sensitive small organic molecule fluorescence sensor for the Sec detection, a new ratiometric fluorescence sensor Q7 was designed based on the fluorescence resonance energy transfer (FRET) strategy with coumarin fluorophore as energy donor and 4-hydroxy naphthalimide fluorophore (with 2,4-dinitrobenzene sulfonate as fluorescence signal quencher and Sec-selective recognition site) as an energy acceptor. The sensor Q7 exhibited only a blue fluorescence signal, and displayed two well distinguished emission bands (blue and green) in the presence of Sec with ∆λ of 68 nm. Moreover, concentrations ranging of quantitative detection of Sec of Q7 was from 0 to 45 μM (limit of detection = 6.9 nM), with rapid ratiometric response, high sensitivity and selectivity capability. Impressively, the results of the living cell imaging test demonstrated Q7 has the potentiality of being an ideal sensor for real-time Sec detection in biosystems.

Thiethylated naphthalimide functional silica nanomaterials: A fluorescent nanosensor for detection of HClO in living cells

In this work, a new type of silica nanoparticles fluorescent probe (N–Si) was successfully synthesized by grafting the naphthalimide fluorophore to the surface of silica nanoparticles. XRD and scanning electron microscopy were used to characterize N–Si, the results illustrated that we have obtained expected silica nanoparticles. What's more, spectral results indicate that the probe N–Si can be used to quickly detect HClO and shows excellent specificity for it. Importantly, the probe N–Si has been successfully demonstrated for monitoring HOCl in living cells. Our work provided strong evidence for the detection of HOCl in fluorescence imaging.

A rational design of fluorescent probes for specific detection and imaging of endogenous formaldehyde in living cells

Formaldehyde (FA) plays important roles in many physiological processes and closely relates to human health. However, the specific detection of FA remains a great challenge. Herein, we report a rational strategy for specific detection and imaging of FA through combining characteristic structure of a fluorophore merged with the modified ortho-phenylenediamine as a recognition moiety. After the reaction of FA and the propyl-modified ortho-phenylenediamine, the probe NP1 and NP2 based on naphthalimide fluorophore exhibited the turn-on fluorescence response for the detection of FA. In particular, the probe NP2 with the greater steric hindrance presented superior specificity for imaging the endogenous FA in living cells. This work may serve as a general strategy to design specific recognition moieties for FA probes.

A reactive probe for Co2+ ion detection based on a catalytic decomposition process and its fluorescence imaging in living cells.

A novel reactive fluorescent probe for cobalt ions was prepared based on integration of thiourea functional groups, coumarin, and naphthalimide fluorophores. There was no fluorescence observed for the probe itself, however, in the presence of cobalt ions, catalytic decomposition occurred for the probe and coumarin molecular fragments were produced that emitted blue fluorescence. This enabled the probe to be used as a 'turn on' reagent for detection of cobalt ions. Under physiological pH conditions and in appropriate solvent systems, an obvious fluorescence enhancement for cobalt ions was observed in selective experiments. Competition experiments indicated that cobalt ions could still induce fluorescence enhancement in the presence of other metal ions. Sensitivity experiments showed that the detection limit for cobalt ions was 6.0 nM. Dynamics research demonstrated that the catalytic process was a pseudo-first-order reaction and the reaction constant (kobs ) was calculated to be 1.49 × 10-2 min-1 . In addition, the mechanism of catalytic decomposition could be demonstrated using electrospray ionization mass spectrometry and thin layer chromatography experiments. Cell fluorescence imaging experiments demonstrated that the probe could be used to detect cobalt ions in living HeLa cells.