Cationic Probe Research Articles

A cationic AIE luminutesogen TBPD2+-6C as a potential bacterial detection agent and bactericide for plants bacterium

The rise of plant bacterial pathogens poses a significant threat to the yield and quality of essential food crops and cash crops globally. Our research introduced a versatile cationic AIE fluorescent probe for detecting and eliminutesating plant bacteria. With its unique aggregation-induced emission property, TBPD2+-6C can effectively detect plant bacteria by causing a fluorescence quenching effect and enables bacterial imaging under green fluorescence channels. Additionally, TBPD2+-6C demonstrates outstanding antibacterial effectiveness, with EC50 values of 0.27, 3.86, 0.47, and 11.5 μg/mL against Xanthomonas oryzae pv. oryzicola (Xoc), X. oryzae pv. oryzae (Xoo), Pseudomonas syringae pv. actinidiae (Psa), and X. axonopodis pv. citri (Xac), respectively. In vivo testing against Xoc revealed TBPD2+-6C showed better activity than commercial thiodiazole copper (TC) and bismerthiazol (BT). Furthermore, the investigation into the antibacterial mechanism revealed that the cationic compound can effectively integrate into the bacterial membrane, disrupt the membrane structure, trigger ROS accumulation, and inhibit biofilm formation. In conclusion, the development of multifunctional, broad-spectrum antimicrobial system molecular designs for rapid real-time detection, imaging, and elimination of resistant microbes could play a vital role in combating pathogens.

Probing Electrostatic and Hydrophobic Associative Interactions in Cells.

Weak nonspecific interactions between biomacromolecules determine the cytoplasmic organization. Despite their importance, it is challenging to determine these interactions in the intracellular dense and heterogeneous mixture of biomacromolecules. Here, we develop a method to indicate electrostatic and hydrophobic associative interactions and map these interactions. The method relies on a genetically encoded probe containing a sensing peptide and a circularly permuted green fluorescent protein that provides a ratiometric readout. Inside bacterial and mammalian cells, we see that the cytoplasmic components interact strongly with cationic and hydrophobic probes but not with neutral hydrophilic probes, which remain inert. The Escherichia coli cytoplasm interacts strongly with highly negatively charged hydrophilic probes, but the HEK293T cytoplasm does not. These associative interactions are modulated by ATP depletion. Hence, the nonspecific associative interaction profile in cells is condition- and species-dependent.

Deciphering Doping Effects in a V-Doped Ni Catalyst for Hydrogen Electrooxidation.

The improved performance of soluble metal-doped Ni catalysts is perplexed by the evolvable surface structures in the alkaline electrolytes for hydrogen oxidation reaction (HOR). Herein, V-doped Ni nanoparticles, as a proof of concept, were carefully evaluated to explore the intrinsic function of the enthetic V-species in assisting the HOR kinetic improvement. As expected, it exhibits a mass-normalized kinetic current density of 50.34 mA mgNi-1, more than 12 times that of the Ni counterpart without the introduction of V. Systematic investigations prove that the surface V-species, including the V-oxides and the doped V atoms at the outmost layer, would be dissolved into the electrolytes during the alkaline HOR process. The remaining V-dopants inside the nanoparticles would rationally weaken the hydroxyl binding energy (OHBE) of the Ni-based surfaces, thereby accelerating the formation of water molecules. We also uncover that Ni is located at the overstrong branch of the OHBE-described volcano plot through theoretical calculations and alkali-metal cation probe experiments, and weakening the OHBE by internal V-doping can leave the activity to the volcanic apex.

Molecular-Scale Interactions in the Choline Chloride-Ethylene Glycol Deep Eutectic Solvent System: The Importance of Chromophore Charge in Mediating Rotational Dynamics.

We report on the rotational diffusion dynamics of three chromophores (disodium fluorescein, oxazine 725, and perylene) in a series of choline chloride-ethylene glycol (ChCl:EG) deep eutectic solvent (DES) systems. We observe behavior independent of DES bulk viscosity for the cationic and neutral probes and behavior that is consistent with stick-limit interactions for the modified Debye-Stokes-Einstein model for the anionic probe. This finding indicates that the anionic species is integral to the interactions between DES constituent species that are responsible for local organization, consistent with previous MD simulations that showed higher interaction energies associated with both the hydrogen bond donor (EG) and hydrogen bond acceptor (Ch+) interactions with Cl- in ChCl:EG mixtures. The reorientation data reported here also indicate a region around 15 mol % ChCl where the stoichiometric relationship between the species gives rise to changes in the details of intermolecular interactions.

Mitochondrial STED Imaging and Membrane Potential Monitoring with a Cationic Molecular Probe.

Mitochondria are essential organelles that not only undergo dynamic morphological changes but also exhibit functional activities such as mitochondrial membrane potential (MMP). While super-resolution techniques such as stimulated emission depletion (STED) nanoscopy can visualize the ultrastructure of mitochondria and the MMP probe can monitor mitochondria function, few dyes meet both demands. Here, a small molecule (MitoPDI-90) based on perylene diimide with cationic groups is reported and used for mitochondrial STED imaging and MMP indication. Characterized by excellent photostability, biocompatibility, and high quantum yield, MitoPDI-90 exhibits STED imaging compatibility, facilitating visualization of mitochondrial cristae and time-lapse imaging of highly dynamic mitochondria in living cells. Besides, MitoPDI-90 targets the mitochondria through electrical potential, also enabling live-cell MMP monitoring. MitoPDI-90 allows for super-resolution visualization and time-lapse imaging of mitochondria, and more importantly, indication of changes in MMP, providing insight into the functional activity of live-cell mitochondria.

Benzo-Crown-Ether Functionalized O-BODIPY Probes for Cations - A Selective Fluorescent Probe for Ba2.

Herein, we report the synthesis and sensing characteristics of 4,4'-methoxy-substituted BODIPY fluorescent probes (O-BODIPYs) 3, 4 and 5 equipped with differently sized benzo-crown ethers (cf. Scheme 1, 3 (benzo-15-crown-5), 4 (benzo-18-crown-6) and 5 (benzo-21-crown7)). O-BODIPYs 3, 4 and 5 exhibited in comparison to their known F-BODIPY analogues 3a, 4a and 5a (cf. Scheme 1) an improved solubility in aqueous medium and higher fluorescence quantum yields. Fluorometric study in aqueous solutions of 3, 4 and 5 in the presence of different cations show cation induced fluorescence enhancements (FE). Compared to the benzo-crown ether substituted F-BODIPY analogues 3a, 4a and 5a, we found for the free O-BODIPYs 3, 4 and 5 higher fluorescence quantum yields (φf) but lower cation induced FEs. We show that in aqueous medium the fluorescence quenching process (OFF switching), a photoinduced electron transfer, in O-BODIPYs 3, 4 and 5 is less effective and consequently sensitive and selective ON switching of the fluorescence by cations, too. Albeit these observations the novel benzo-21-crown-7 equipped fluorescent probe 5 exhibits a good fluorometric Ba2+ selectivity and Ba2+ sensitivity in conjunction to their aqueous solubility.

Aerosol-assisted fabrication of mesoporous CeO2 nanoparticles for cargo controlled delivery application

This study presents a spray pyrolysis technique for fabricating mesoporous cerium oxide nanoparticles (MCNs) with tunable properties. The MCNs were extensively characterized by their morphology, crystallinity, optical properties, and surface area through transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy, UV−vis spectroscopy, and BET adsorption isotherms. We manipulated synthesis parameters to tailor these characteristics, and subsequently evaluated the ability of MCNs to load and release the cationic probe Rhodamine 6G, demonstrating their responsiveness to pH variations. The particles showed high entrapment efficiency (up to 40 %), pH-responsive release, and pore-size-dependent release performance. Additionally, the biocompatibility of MCNs was confirmed by assessing their impact on the viability of HEK293 cells. The findings indicate that the fabricated MCNs hold promise for targeted nano-therapeutic applications, particularly within acidic microenvironments such as tumor sites.

An Emission-Based Probe for the Detection and Quantification of DNA and RNA.

Sequence-independent detection of low concentrations of nucleic acids is important for applications in forensics and diagnostics. An emission-based probe for detecting and quantifying DNA and RNA utilizing a water-soluble dicationic tetraphenylethene (TPE) derivativewas developed. The recognition is based on the electrostatic and other non-covalent interactions between the phosphate backbone of nucleic acids and the cationic probe, which cause the restriction of rotation of the aryl units of the probe, ensuing in the enhancement of the fluorescence signal. The binding was validated by different spectroscopic techniques and also by electrophoretic mobility shift assay. The probable mode of binding with the nucleic acids was studied by blind-docking studies that correlated well with the experimental results.

Development and Application of Cationic Nile Blue Probes in Live-Cell Super-Resolution Imaging and Specific Targeting to Mitochondria.

Mitochondria are essential organelles involved in various metabolic processes in eukaryotes. The imaging, targeting, and investigation of cell death mechanisms related to mitochondria have garnered significant interest. Small-molecule fluorescent probes have proven to be robust tools for utilizing light to advance the study of mitochondrial biology. In this study, we present the rational design of cationic Nile blue probes carrying a permanent positive charge for these purposes. The cationic Nile blue probes exhibit excellent mitochondrial permeability, unique solvatochromism, and resistance to oxidation. We observed weaker fluorescence in aqueous solutions compared to lipophilic solvents, thereby minimizing background fluorescence in the cytoplasm. Additionally, we achieved photoredox switching of the cationic Nile blue probes under mild conditions. This enabled us to demonstrate their application for the first time in single-molecule localization microscopy of mitochondria, allowing us to observe mitochondrial fission and fusion behaviors. Compared to conventional cyanine fluorophores, this class of dyes demonstrated prolonged resistance to photobleaching, likely due to their antioxidation properties. Furthermore, we extended the application of cationic Nile blue probes to the mitochondria-specific delivery of taxanes, facilitating the study of direct interactions between the drug and organelles. Our approach to triggering cell death without reliance on microtubule binding provides valuable insights into anticancer drug research and drug-resistance mechanisms.

Accelerated Activity-Based Sensing by Fluorogenic Reporter Engineering Enables to Rapidly Determine Unstable Analyte.

Accurate detection of labile analytes through activity based fluorogenic sensing is meaningful but remains a challenge because of nonrapid reaction kinetic. Herein, we present a signaling reporter engineering strategy to accelerate azoreduction reaction by positively charged fluorophore promoted unstable anion recognition for rapidly sensing sodium dithionite (Na2S2O4), a kind of widespread used but harmful inorganic reducing agent. Its quick decomposition often impedes application reliability of traditional fluorogenic probes in real samples because of their slow responses. In this work, four azo-based probes with different charged fluorophores (positive, zwitterionic, neutral, and negative) were synthesized and compared. Among of them, with sequestration effect of positively charged anthocyanin fluorophore for dithionite anion via electrostatic attraction, the cationic probe Azo-Pos displayed ultrafast fluorogenic response (∼2 s) with the fastest response kinetic (kpos' = 0.373 s-1) that is better than other charged ones (kzwi' = 0.031 s-1, kneu' = 0.013 s-1, kneg' = 0.003 s-1). Azo-Pos was demonstrated to be capable to directly detect labile Na2S2O4 in food samples and visualize the presence of Na2S2O4 in living systems in a timely fashion. This new probe has potential as a robust tool to fluorescently monitor excessive food additives and biological invasion of harmful Na2S2O4. Moreover, our proposed accelerating strategy would be versatile to develop more activity-based sensing probes for quickly detecting other unstable analytes of interest.

Construction of a human serum albumin site II-targeting supramolecular fluorescent probe for cell imaging and drug delivery

Two cationic probes (named TAB2 and TAB6) specifically for binding to site II in human serum albumin (HSA) were designed and synthesized. Both probes exhibited selective fluorescence “turn-on” responsiveness to site II in HSA, though minor differences in their cationic terminals resulted in notable variations in their albumin responsiveness. TAB2 and TAB6 also exhibited strong binding affinity toward HSA. The presence of phenylbutazone, ibuprofen, and lidocaine had minimal impact on the albumin responsiveness of these probes. Furthermore, the complex formed by TAB2/6 and water-soluble pillar[5]arene (WP5) showed enhanced HSA site II-targeting fluorescence responsiveness. More importantly, the WP5-TAB2/6 complex self-assembled into vesicular supramolecular probes in aqueous solution (pH=7.4). Those supramolecular probes were promising for HSA-mediated cell imaging and act as a pH-sensitive drug-delivery platform to enhance the anticancer efficiency of doxorubicin (DOX).

Effect of Pore Confinement of Ionic Liquids on Solute Diffusion within Mesoporous Silica Microparticles.

The transport properties of the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) confined within silica microparticles with well-ordered, accessible mesopores (5.4 or 9 nm diameter) were investigated. [BMIM][PF6] confinement was confirmed by using differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. The transport properties of the confined IL were studied using the neutral and cationic fluorescent probes 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) and rhodamine 6G, respectively, through fluorescence recovery after photobleaching (FRAP) in confocal microscopy. The diffusivity of DCM in 9 nm pores is 0.026 ± 0.0091 μm2/s, which is 2 orders of magnitude less than in the bulk ionic liquid. The pore size did not affect the diffusivity of DCM in unmodified silica nanopores. The diffusivity of the cationic probe is reduced by 63% relative to that of the neutral probe. Diffusivity is increased with water content, where equilibrium hydration of the system leads to a 37% increase in DCM diffusivity. The most dramatic impact on diffusivity was caused by tethering an IL-like methylimidazolium chloride group to the pores, which increased the pore hydrophobicity and resulted in 3-fold higher diffusivity of DCM compared to bare silica pores. Subsequent exchange of the chloride anion from the tethering group with PF6- decreased the diffusivity to half that of bare silica. The diffusion of probe molecules is affected most strongly by the pore wall effects on probe interactions rather than by the pore size itself, which suggests that understanding pore wall diffusion is critical to the design of nanoconfined ILs for separations, catalysis, and energy storage.

Investigations of the relationships between structure and electrochemical properties of fullerenol nanoaggregates

Hybrid materials containing fullerenols have been used as electrodes in many applications, such as electrochemical biosensors for different targets or in hydrogen and oxygen reduction reactions. However, electrodes modified with fullerenols and without other electroactive materials are not much explored, and the electrochemical behavior of fullerenols themselves is not well-established in the literature. Herein, we report the basic electrochemical characterization of electrode modified with fullerenol and some correlations between material structure and electrochemical behavior. The prepared fullerenol is composed of nanoaggregates dispersed in an organic solvent. Although the electrode modified with pristine fullerene is slightly less active to [Fe(CN)6]3−/4− concerning bare glassy carbon electrode (GCE), the fullerenol-based electrode presents a much lower activity that is slightly increased after electrochemical reduction. The drying process greatly influences the electrochemical performance of the electrodes modified with fullerenol, and fast drying can form ruptures with micrometric dimensions that provide a particular behavior towards the anionic probe. The reduction process increases the number and sizes of these ruptures and changes the electrochemical response. Moreover, the fullerenol-based electrode is more active for [Ru(NH3)6]3+ than the bare GCE, and the activity was increased after reduction. However, the electrochemical response to the cationic probe is characteristic of macroelectrodes regardless of the drying process or reduction. This work opens new perspectives in the electrochemical studies of modified carbon nanomaterials, with the possibility of producing carbon-based electrodes selective to charged probes by controlling the carbon materials' molecular and microscale structures.

Exploring the probing capacities of MSA capped CdTe semiconductor quantum dots as optical chemsensors via analytical and isotherms modeling for selective Hg2+ detection

Heavy metal ions bioaccumulation can cause severe damage to environment and human health. Hence, the development of an effective detection assay of trace amounts of these ions is of great importance. Here, CdTe quantum dots (QDs) capped with mercaptosuccinic acid (MSA) ligands have been synthesized in aqueous solution with significant stability and good fluorescence properties. Photophysical characterization was performed using FTIR, XRD, HRTEM and UV–Vis. Absorption, PL and PLRT techniques, seeking their subsequent application as fluorescent probes for metal cations. CdTe-MSA QDs showed selective sensitivity toward Hg2+ ions by monitoring quantitative fluorescence quenching with increasing analyte content. Under optimal conditions, the linear range for the detection was 0.2–6 μM with a detection limit of 0.05 μM. According to the Stern–Volmer model, it can be inferred that a static quenching mechanism via Hg2+ selective binding to MSA carboxylate groups is operating with electron transfer process. Excess of mercuric ions further decreased and red shifted the fluorescence possibly due to competitive cation exchanges. To further explain the corresponding ligation mechanisms, adsorption behavior study was conducted via several isotherms as well as statistical physics models. The pseudo-first-order model can describe the adsorption kinetics of Hg2+ on CdTe-MSA QDs more accurately and the experimental data fitted well the Langmuir isotherm model of monolayer adsorption on homogeneous surface. Furthermore, this spontaneous process conforms to the Hill model as a physisorption with an adsorption energy of 32 kJ.mol−1 associated with the electrostatic interactions and hydrogen bonding. The developed system was assayed in the Hg2+ trace amount detection in real tap water and showed satisfactory accuracy performance meeting analytical requirements. The relevant results demonstrated that CdTe-MSA QDs could be deployed as promising Hg2+ fluorescent chemosensing system with high sensitivity and selectivity over wide linear detection range that have great potential for real water samples analysis.

Rigidify styryl-pyridinium dyes to benzo[h]coumarin-based bright two-photon fluorescent probes for cellular bioimaging.

Fluorescence imaging of organelles at the cellular level is important for studying biological processes. The development of a highly emissive fluorescent probe that operates under a suitable excitation light source is a key step in high-quality fluorescence imaging. For long-term, high-fidelity fluorescence imaging of mitochondria-related cellular processes using two-photon microscopy and stimulated emission depletion microscopy, we developed a new benzocoumarin-based cationic fluorescent probe (BS-CN) that is far-red emitting, water-soluble, photostable, and very bright in cells. BS-CN showed a remarkably high quantum yield of 0.35 and a large two-photon excited fluorescence action cross-section of 76 GM, enabling the long-term tracking of mitochondria in live cells. In addition, BS-CN exhibited a certain affinity for RNA and stained nucleoli in fixed cells. A comparative assessment of the photophysical properties and bioimaging performance of benzo[h]coumarin-pyridinium and the structurally similar styryl-pyridinium (BS-MN) clearly indicated the importance of structural rigidity for fluorescence efficiency.

Super-resolution fluorescence imaging of PEDOT:PSS films.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a popular conduction polymer and widely used in organic electronics, bioelectronics and printed electronics. It is believed that PEDOT:PSS has a core-shell colloidal structure dispersed in the formulation. However, the size and surface functional groups of the PEDOT:PSS dispersion and films remain to be visualized. Here, we have introduced the concept of aggregation-induced emission (AIE) to super-resolution imaging for designing the cationic probe TPE-4N+ and accomplished the nanoscale optical visualization of PEDOT:PSS films through reversible electrostatic interactions. Information on the PEDOT:PSS size and surface charge has been successfully collected via super-resolution imaging. The full-width at half-maximum (FWHM) of PSS nanoparticles was observed to be approximately 30-40 nm. The super-resolution fluorescence imaging method can also be used to monitor the PEDOT:PSS film after acid treatment. It was observed that PSS chains were washed away when exposed to concentrated sulfuric acid, which explains why concentrated sulfuric acid treatment greatly improves the conductivity of the PEDOT:PSS film. Super-resolution imaging is promising as an effective method for characterizing PEDOT:PSS films.

Bioisostere-conjugated fluorescent probes for live-cell protein imaging without non-specific organelle accumulation.

Specific labeling of proteins using membrane-permeable fluorescent probes is a powerful technique for bioimaging. Cationic fluorescent dyes with high fluorescence quantum yield, photostability, and water solubility provide highly useful scaffolds for protein-labeling probes. However, cationic probes generally show undesired accumulation in organelles, which causes a false-positive signal in localization analysis. Herein, we report a design strategy for probes that suppress undesired organelle accumulation using a bioisostere for intracellular protein imaging in living cells. Our design allows the protein labeling probes to possess both membrane permeability and suppress non-specific accumulation and has been shown to use several protein labeling systems, such as PYP-tag and Halo tag systems. We further developed a fluorogenic PYP-tag labeling probe for intracellular proteins and used it to visualize multiple localizations of target proteins in the intracellular system. Our strategy offers a versatile design for undesired accumulation-suppressed probes with cationic dye scaffolds and provides a valuable tool for intracellular protein imaging.

Controlled Surface Functionalization Using Aryldiazonium Salts for the Development of Aptasensing Platforms

It is well known that both the aptamer surface density and surface chemistry can have a strong influence on the analytical performance of aptasensors based on target-induced conformational changes1. In this context, we report here an improved protocol for obtaining aptasensing platforms which allows fine-tuning the DNA aptamer surface coverage. First, glassy carbon substrates were functionalized with ethynylphenyl groups through the electrochemical reduction of silyl-protected ethynylphenyl diazonium tetrafluoroborates followed by deprotection with tetrabutylammonium fluoride2. The successful removal of the protecting groups (triisopropylsilyl-, triphenylsilyl- and tris(biphen-4-yl)silyl-) was confirmed by X-ray photoelectron spectroscopy and cyclic voltammetry in the presence of Fe(CN)6 3-/4- as soluble redox probe. Following “click” post-modification with suitable derivatization reagents, the surface coverage with ethynylphenyl groups was assessed using complementary techniques such as XPS, cyclic voltammetry and chronocoulometry. For example, the F/C surface ratio of substrates derivatized with 1-(2,2,2-trifluoroethoxy)-6-azidohexane provided an indication of the functionalization degree, and the integration of Fc/Fc+ voltammetric peaks for substrates modified with N-(6-azidohexyl)ferrocenecarboxamide allowed a quantitative determination of the surface coverage. Both techniques showed a good correlation between the protective group size and the surface coverage with alkyne groups. Likewise, we observed a similar trend for substrates derivatized with azide-modified oligonucleotides, where the surface packing density was determined based on the chronocoulometric response of Ru(NH3)6 3+, a cationic redox probe which binds with the negatively charged phosphate groups from the oligonucleotide backbone. As proof of concept, we further developed an electrochemical molecular beacon aptasensor employing a ferrocene-labeled quinine aptamer. We demonstrate that the aptamer surface density, and ultimately the analytical performance of molecular beacon aptasensors, can be effectively fine-tuned by employing silyl protecting groups of different sizes.Acknowledgements This work was supported by a grant from the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P4-ID-PCE-2020-2474, within PNCDI III. References Onaş, A. M., Dascălu, C., Raicopol, M. D. & Pilan, L. Critical Design Factors for Electrochemical Aptasensors Based on Target-Induced Conformational Changes: The Case of Small-Molecule Targets. Biosensors 12, (2022).Leroux, Y. R., Fei, H., Noël, J.-M. M., Roux, C. & Hapiot, P. Efficient covalent modification of a carbon surface: Use of a silyl protecting group to form an active monolayer. J. Am. Chem. Soc. 132, 14039–14041 (2010).

Investigation of sorption capacity of AMPS-(PHE-Ce)/MC hydrogel for effective removal of basic red 2 dye

Using toxic and non-biodegradable dyes in various industries has resulted in severe environmental issues and is detrimental to living organisms. To reduce the harmful effects of these contaminants, it is essential to develop efficient effluent treatment methods. Hydrogel sorbents are a promising solution to this problem due to their high efficacy, easy synthesis, quick recovery, and potential for future reuse. In this study, a hydrogel sorbent using 2-acrylamido-2-methylepropanesulfonic acid, polyhydroxyethyl cellulose, and moisiv type 5A 1/16th inches pellet (moisiv clay) [AMPS-(PHE-Ce)/MC] was synthesized. The hydrogel composite material achieved equilibrium in 24 hours by Fickian diffusion, absorbing water and expanding in size. To investigate the sorption potential of the hydrogel sorbent, the cationic probe dye basic red 2 (BR-2) was used as the target pollutant. Different isotherm and kinetic models were applied to analyze the sorption data. The analysis of the sorption data revealed that the hydrogel facilitated the chemisorption of BR-2 through the ionic interaction with the dye. The hydrogel exhibited impressive sorption capacities (1331 mg g−1), which suggests that it holds promise as an efficient solution for eliminating cationic dyes in various industrial and environmental settings.

Research Progress on Naphthalimide Fluorescent Probes

AbstractNaphthalimide derivatives are attracting increasing attention as fluorescent probes due to their excellent modifiability and photophysical properties. Their large, rigid coplanar structures and conjugated systems enable easy generation of fluorescence. The imide units and bromonaphthalene functionality offer facile and concise modification pathways in preparing amenable probes for different metal cations, anions, small molecules, and organelles. Therefore, naphthalimide probes have great potential for application in research fields, such as analytical chemistry, cell biology, and clinical diagnosis.