Research Progress in 1, 8-Naphthalimide-Based Fluorescent Probes for Two-Photon Imaging

Synthesis and Application of 1,8-Naphthalimide Derivatives Fluorescent Probe for Sequential Recognition of Cu2+ and H2PO4. J Fluoresc 2024:10.1007/s10895-024-03692-y. [PMID: 38613712 DOI: 10.1007/s10895-024-03692-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

A naphthalimide Schiff base fluorescent probe (BSS) was designed and synthesized from 4-bromo-1,8-naphthalic anhydride, and its structure was characterized by 1HNMR, 13CNMR, FTIR, and MS. Fluorescence emission spectra showed that probe BSS could realize the "turn-off" detection of Cu2+ in acetonitrile solution, detection process with strong specificity and excellent anti-interference of other metal ions. In the fluorescence titration experiments, fluorescence intensity of BSS showed a good linear relationship with the Cu2+ concentration (0-10 µmol/L), and the detection limit was up to 7.0 × 10- 8 mol/L. Meanwhile, BSS and Cu2+ could form a 1:1 complex (BSS-Cu2+) during the reaction process. Under the same detection conditions, complex BSS-Cu2+ had specific fluorescence recovery properties for H2PO4- and the whole process was not only fast (6 s) but also free of interference from other anions, with a detection limit was as low as 5.7 × 10- 8 mol/L. In addition, complex BSS-Cu2+ could be successfully applied to the detection of H2PO4- in actual water samples, which with excellent application prospects.

A novel fluorescent probe for the detection of formaldehyde in real food samples, animal serum samples and gaseous formaldehyde

Formaldehyde (FA) is widely used as an adhesion promoter and dyeing aid in industrial production. Ingestion of a certain amount of formaldehyde may cause corrosive burns in the mouth, throat, and digestive tract. Therefore, it is very necessary to use simple and effective detection methods to ensure human health and food safety. Herein, a novel fluorescent probe NFD based on naphthalimide for the detection of formaldehyde in food was designed and synthesized. The probe had a remarkable fluorescence response to formaldehyde at 554 nm. And it exhibited fascinating advantages of good selectivity, high sensitivity, and low detection limit. In addition, the solid sensor prepared by loading the probe on the filter paper was successfully realized the visual detection of liquid and gaseous formaldehyde. More importantly, the probe possessed excellent stability in the detection of formaldehyde in real food samples and animal serum samples.

Activatable fluorescence molecular imaging and anti-tumor effects investigation of GSH-sensitive BRD4 ligands

Overexpression of bromodomain 4 (BRD4) is closely correlated with a variety of human cancers by regulating the histone post-translational modifications, which renders BRD4 a promising target for pharmacological discoveries of novel therapeutic agents for cancer therapy. We herein present the design, chemical synthesis, cellular imaging and biological assessment of a novel tumor-sensitive BRD4 ligand (compound 4) by introducing anticancer BRD4 inhibitor into naphthalimide moiety (fluorescent reporter) via a sulfonamide unit as glutathione (GSH)-specific cleavable linker. Upon reaction with abundant intramolecular GSH in cancer cells or free GSH in aqueous solution (pH = 7.4), sulfonamide cleavage of 4 occurs, leading to the release of BRD4 inhibitor and concomitant fluorescence-on. This activatable fluorescence molecular imaging was demonstrated to preferentially occur in tumor cells. Moreover, towards cancer cell lines MGC-803 cells and THP-1, compound 4 was identified to show better antitumor efficacy than net BRD4 inhibitor. Collectively, this study presents a drug delivery strategy, wherein the drug release can be directly monitored in the cellular content by fluorescence imaging, and provides a valuable compound 4 as a potential antitumor agent. Compound 4 may represent a useful tool for explorative studies of BRD4 inhibition, such as an improved understanding of BRD4 inhibitor release-related information.

A 1,8-naphthalimide-based lysosome-targeting dual-analyte fluorescent probe for the detection of pH and palladium in biological samples

Fluorescent probes containing 1,8-naphthalimide dyes have been used to detect biomolecules in the environmental and biological fields. However, most of the probes only exhibit single fluorescent output to one analyte, making them insufficient for detection of more analytes. Herein, we developed a novel 1,8-naphthalimide-based lysosome-targeting dual-analyte sensitive fluorescent probe (DPPP) for the detection of pH and palladium (Pd⁰) using two different emissive channels. The probe showed high selectivity, large Stokes shifts (Δλ ≥ 100 nm) and enhanced response to pH, with blue emission at 485 nm via a morpholine group, and responsive to Pd⁰ concentration, with yellow emission at 545 nm via an allylcarbamate group. The effect of DPPP was successfully observed for sensitive visualizing pH and Pd⁰ concentration in the lysosome of HeLa cells and zebrafish using fluorescence microscopy. This work provides guidance for the design of dual-analyte fluorescent probes.

1,8-Naphthalimide-Based Multifunctional Compounds as Cu2+ Probes, Lysosome Staining Agents, and Non-viral Vectors

A series of multifunctional compounds (MFCs) 1a-1d based on 1,8-naphthalimide moiety were designed and synthesized. Due to the good fluorescence property and nucleic acid binding ability of 1,8-naphthalimide, these MFCs were applied in Cu2+ ion recognition, lysosome staining as well as RNA delivery. It was found that these MFCs exhibited highly selective fluorescence turn-off for Cu2+ in aqueous solution. The fluorescence emission of 1a-1d was quenched by a factor of 116-, 20-, 12-, and 14-fold in the presence of Cu2+ ions, respectively. Most importantly, 1a-Cu and 1b-Cu could be used as imaging reagents for detection of lysosome in live human cervical cancer cells (HeLa) using fluorescence microscopy. Furthermore, in order to evaluate the RNA delivery ability of 1a-1d, cellular uptake experiments were performed in HeLa, HepG2, U2Os, and MC3T3-E1 cell lines. The results showed that all the materials could deliver Cy5-labled RNA into the targeted cells. Among them, compound 1d modified with long hydrophobic chain exhibited the best RNA delivery efficiency in the four tested cell lines, and the performance was far better than lipofectamine 2000 and 25 kDa PEI, indicating the potential application in non-viral vectors.