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PEGylated 2-(2-(6-(dimethylamino)benzooxazol-2-yl)vinyl)quinolin-8-ol (BQ-mPEG) was synthesized, which exhibited strong fluorescence at 610 nm (φf = 0.11) and a large Stoke's shift (Δλ = 202 nm) in the aqueous solution. The fluorophore displayed a two-photon absorption characteristic and a strong red emission (λem = 625 nm) was observed with NIR (950 nm) irradiation. The feasibility of using BQ-mPEG as a fluorescent imaging reagent suggested that the fluorophore targets mitochondria, and with 950 nm excitation, bright fluorescence images in HeLa live cells were observed. Furthermore, the fluorophore exhibited some advantages of high photostability and pH stability, as well as low cytotoxicity. [ABSTRACT FROM AUTHOR]

In this paper, nitrogen-doped carbon dots (NCDs) were synthesized via a facile hydrothermal method using gum arabic (GA) and tris(hydroxymethyl)methyl aminomethane (tris) as precursors. The resultant NCDs show uniform size distribution and stable optical performance. Then a fluorescent signal quenching probe based on NCDs was proposed for the quantitative detection of mercury ions (Hg2+). The developed fluorescent nanoprobe based on NCDs demonstrated a good linear relationship in the range of 10 to 120 μM (R² = 0.99265) for toxic mercury(II), with a detection limit of 4.87 μM. Additionally, the present assay system could be efficiently used for the detection of Hg2+ in real water samples with a satisfactory recovery rate (96.11-104.04%). The metal-free NCDs, which exhibited little cytotoxicity, were successfully applied to in vitro fluorescence imaging of human triple negative breast cancer (TNBC) cells, achieving visualization of Hg2+ in cells. With good water solubility and biocompatibility, the nitrogen-doped carbon dots synthesized by this economical and ecologically friendly process are suitable for use in analytical testing and biological research. [ABSTRACT FROM AUTHOR]

A novel supramolecular system based on calix[4]arene linked with rhodamine B was designed and synthesized, incorporating different alkoxy side chains. All four supramolecular compounds (3a–3d) synthesized using this approach exhibited nematic-type liquid crystalline properties. Detailed analyses using polarizing optical microscopy, differential scanning calorimetry, the X-ray diffraction technique, and thermogravimetry were performed to investigate the microscopic, molecular arrangement pattern, and thermal behavior of the compounds. The well-known Schlieren and threaded-type texture pattern was observed in all four bi-substituted calixarene derivatives. They displayed unique texture patterns supporting the idea of a well-organized supramolecular structure. Additionally, these materials demonstrated enantiotropy-type mesophase with a wide temperature range and good thermal stability. Notably, they exhibited light-emitting properties in both solution and solid thin film states, showing the intriguing aggregation-induced emission effect. All four compounds adopted a cone conformation with two side substitution on the calix[4]arene rigid core. Compound 3c was utilized to stain nematode samples using a solution-state aggregation approach. The fluorescent supramolecule effectively allowed visualization and tracking of the staining patterns within the nematode organisms. This methodology enabled the examination of cellular and subcellular structures, further offering valuable insights into the behavior and morphology of nematodes. [ABSTRACT FROM AUTHOR]

Traditional chemotherapy faces challenges related to limited drug efficacy and adverse reactions. Intelligent nanocarrier drug delivery systems (INDDSs) promise improved treatment outcomes with reduced toxicity. However, several clinical challenges persist in achieving rapid drug release and real-time monitoring. Herein, a ROS-responsive amphiphilic copolymer was synthesized: polyethylene glycol (mPEG-TK-OH) with ROS-responsive thioketal (TK) as the macromolecular initiator, and enzymatic ring-opening polymerization of caprolactone was performed. Small molecules of tetraphenylethylene (TPE) with aggregation-induced emission (AIE) properties were added to the polymer's terminus to enable fluorescence imaging and the ROS-responsive amphiphilic copolymer mPEG-TK-PCL-TPE with AIE properties is formed and enhances drug release monitoring through fluorescence resonance energy transfer (FRET) between TPE and the hydrophobic anti-cancer drug DOX. Leveraging distinct ROS levels between tumor and normal cells, these ROS-responsive nanomicelles effectively respond to high intracellular redox-active species and release DOX. The mPEG-TK-PCL-TPE micelles displayed a suitable size, high drug loading, and excellent imaging quality. In vitro cell experiments confirmed their biocompatibility and efficacy in inhibiting 4T1 tumor cells. This ROS-responsive amphiphilic copolymer, incorporating the AIE structure, introduces new opportunities for cancer treatment, enabling real-time drug release tracking and improving therapeutic outcomes. [ABSTRACT FROM AUTHOR]

This study focuses on the use of carbon quantum dots (CQDs) from Syzygium cumini seeds prepared through hydrothermal synthesis for anti-oxidant, bioimaging, and anti-neoplastic activities. Syzygium cumini seeds were incorporated with various biomass-sourced precursors to enhance their physicochemical properties, and doping of folic acid was performed to create surface passivated folate receptors for better anti-neoplastic activity exhibiting minimal toxicity, excellent biocompatibility, outstanding luminosity, and optical features. The concentration of CQDs required to inhibit the proliferation of cells by 50% (at 500 μg mL−1 concentration) was calculated by applying the dose–response curve applied to the HeLa cell line, and the conclusion was computed by means of an augmented mimicking approach, leading to roughly identical inhibition by folic acid doped S. cumini seeds (40.926%) and doxorubicin (DOX) (43.39%) justifying better anti-neoplastic activity. The anti-oxidant potency of the prepared CQDs was assessed to be exceedingly excellent, with an index of up to 98.99%, implying resilient surface passivation. CQDs utilized for in vitro photoluminescence and live cell imaging of S. cerevisiae displayed green and blue fluorescence images with stabilized luminescence with extraordinary quantum yield (50.74%). [ABSTRACT FROM AUTHOR]

When designing sensors for optoelectronic devices, fluorescent materials are always the choice of material chemists. Among the existing fluorescent molecules, the most widely used sensing materials are colloidal nanocrystals, which are classified as quantum dots (QDs). Photoluminescence and tuning of the band gap are the two domains that are explored while engineering optically active crystals. The selection of dopants in a host lattice is the initial step towards achieving the material of choice and designing tailor-made stable materials. Among various QD materials, doped ZnS quantum dots have emerged as a fascinating class, showcasing distinctive characteristics resulting from both transition and non-transition metal doping. This work reviews recent developments in the synthesis, structural characterization, and applications of transition and non-transition metal-doped ZnS quantum dots. Transition metal doping, involving elements such as Mn, Co, and Cu, imparts remarkable photoluminescence properties to QDs, rendering them suitable for optoelectronic devices, such as light-emitting diodes and displays. Non-transition metal doping, involving elements such as Al, Mg, and Ga, facilitates bandgap engineering, paving the way for enhanced light absorption and utilization in photovoltaics and photocatalysis. Transition and non-transition metal-doped ZnS quantum dots exhibit diverse applications across multiple domains. In the field of biomedicine, their biocompatibility, tunable fluorescence, and ability to generate reactive oxygen species under light irradiation present opportunities for cellular imaging and photodynamic therapy. Moreover, their integration into composite materials holds the potential for enhanced electronic and optoelectronic device performance. Challenges in this field include achieving precise control over dopant concentrations, uniformity, and stability, while also addressing scalability issues for large-scale production. Future directions include exploring novel doping strategies, co-doping schemes, and surface functionalization techniques to further enhance the properties of doped ZnS quantum dots. In conclusion, transition and non-transition metal-doped zinc sulphide quantum dots showcase a realm of exciting possibilities for technological innovation. Their unique properties, enabled by judicious dopant incorporation, make them valuable materials for applications spanning optoelectronics, energy conversion, and biomedical sciences. As research in this field advances, these doped quantum dots are poised to significantly contribute to the progression of next-generation technologies. [ABSTRACT FROM AUTHOR]

Here, we report the design and synthesis of a Schiff base probe, DBNHC ((E)-2-(2,4-dihydroxybenzylidene)-N-(naphthalen-1-yl)hydrazine-1-carbothioamide), and its interaction with bovine serum albumin (BSA). In ∼100% PBS buffer, the probe DBNHC can self-assemble into nonfluorescent nanoaggregates due to the aggregation caused quenching (ACQ) effect. However, it becomes highly fluorescent (∼14 fold) in the presence of BSA which facilitates the disassembly of nanoaggregates into its monomer. The site-selective fluorescence displacement assay and molecular docking simulations reveal that mainly hydrogen bonding, π⋯sulphur and π⋯alkyl interactions are responsible for the disassembly of nanoaggregates leading to encapsulation of DBNHC monomer at site II in BSA, resulting in a cyan green emission. The detection limit determined by the 3σ/slope method was found to be 58 nM, and the lower dissociation constant [Kd = (1.506 ± 0.196) μM] value suggests strong binding between the probe and BSA. Further, DBNHC was used for cell incubation and in vitro fluorescence imaging of BSA. [ABSTRACT FROM AUTHOR]

Replacement of electron-donating N,N-dialkyl groups with azacyclic groups has been described as a promising auxochrome to improve the low fluorescent quantum yields (ΦF) of conventional fluorophores. However, the insufficient brightness and poor solubility of fluorophores pose a significant bottleneck for bioimaging. A new type of fluorescent coumarin dye was designed and synthesized using 7-azaspiroketals as the electron-donating auxochrome group. Such modifications resulted in high-quality coumarin fluorophores with improved solubility and brightness. To the best of our knowledge, this is the first report of using apex-N-substituted azaspiroketals as an electron donor group in any class of donor–acceptor dye. Furthermore, the successful application of these new dyes in biological imaging for living cells has been demonstrated. [ABSTRACT FROM AUTHOR]

A series of new 2-(indol-3-yl)-6-(hetero)aryl substituted pyridines, 2-(indol-3-yl)-5-phenyl-substituted 2,2′-bipyridine and 5-aryl-6-(pyrrol-2-yl) substituted 2,2′-bipyridines were synthesized as push–pull fluorophores/probes by using a sequence of nucleophilic substitution reaction of hydrogen (SNH) and inverse-demand Diels–Alder reaction. For the obtained compounds, photophysical properties were studied. All the compounds displayed ICT-activity with a large Stokes shift (up to 197 nm) and PLQY up to 0.28. Due to dual emission in polar solvents, one specific probe was able to respond to the action of the local pH changes in the microenvironment and exhibit AIE-activity. The fluorescence titration data at different pH were analyzed to estimate a pKa value of 4.50 for that specific probe. The AIE behavior was further confirmed by means of time-resolved fluorescence lifetime measurements as well as UV-vis spectroscopic studies. The correlation of the influence of the nature of substituents on the degree of ICT state was established based on the analysis of charge transfer (CT) indices and the calculated interfragment charge transfer (IFCT) values. Finally, the fluorophores reported in this study were successfully applied for cellular imaging. [ABSTRACT FROM AUTHOR]

Almost all types of proteins in biology are composed of L -amino acids, and very few contain D -amino acids. Therefore, chiral recognition, especially for the detection of L -amino acids, is of great importance. In this work, luminescent zinc-doped carbon dots (Zn-CDs) were successfully synthesized through a one-step hydrothermal method using [Zn(EDA)3]Cl2 (EDA = ethylenediamine) complex as a precursor, exhibiting superior water stability, low cytotoxicity and good photobleaching stability. It can be used as an "on–off–on" fluorescence probe in aqueous solution to sequentially detect Fe2+ ions and enantiomeric L -Lysine (L -Lys) molecules with the corresponding limit of detection (LOD) of 0.092 and 0.204 μM, respectively. Also, the sequential on–off–on fluorescent changes of Zn-CDs upon the addition of Fe2+ and L -Lys can be applied in living cell imaging, as observed by the contrast of images in confocal microscopy. In addition, two distinct multi-input molecular logic gates, involving distinguishing the effect of L -Lys and D -Lys on the fluorescence of Zn-CDs, and the regulation of fluorescence quenching and recovery of Zn-CDs by Fe2+ ions and L -Lys are established. The Zn-CDs also exhibits a linearly temperature-dependent fluorescence performance with high temperature sensitivity (Sr) of 1.10% °C−1 in 10–90 °C, demonstrating its great potential for biological temperature sensing applications. This work provides a new strategy for exploring novel metal-doped carbon dots with outstanding biocompatibility and multifunctionality in biological applications. [ABSTRACT FROM AUTHOR]

Aza-BODIPY biotin-based nano-self-assembly has been designed with a biotin receptor for selective NIR turn-on fluorescence activity against cancer cells. The nanostructured aza-BODIPY assemblies exhibit distinctive fluorescence characteristics via an avidin-induced partial disintegration process. The in vitro studies for nanoprobes NSA-DPR1a and NSA-DPR1b showed effective recognition and can discriminate biotin receptor-positive cancer cells (MDA-MB-231 and MCF7) compared to non-cancerous cells (MCF10A). [ABSTRACT FROM AUTHOR]

Donor–acceptor substituted aromatic systems are highly regarded organic fluorophores with unique photophysical and electrochemical properties. These molecules offer a wide range of opportunities for advancing modern science through easily modifiable molecular structures. In recent years, there has been growing interest in developing convenient methodologies for synthesising these fluorescent compounds. The carbanion-induced ring transformation of α-pyranones is one such approach that has yielded numerous D–π–A dyads based on aromatic systems with widespread applications as effective fluorophores. Moreover, this method provides explicit functionalization options, allowing fine-tuning of optoelectronic properties according to specific requirements without requiring complex reaction setups or transition metal catalysts/reagents, which makes it more advantageous over other conventional approaches. This review discusses the synthesis of polycyclic aromatic compounds functionalized with donor–acceptor groups via ring transformation reactions of α-pyranone derivatives induced with various carbon nucleophiles, along with their applications in OLEDs, chemosensors, and cell imaging. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) produced and metabolized by mitochondria is closely associated to human physiological function, but its mechanism is not fully revealed due to the difficulty in determining the dose of hydrogen sulfide. Therefore, fluorescent probes with both excellent mitochondrial targeting ability and rapid H2S detection are urgently needed. In this work, a novel fluorescent probe, TPAS-TN, was developed to detect H2S in mitochondria. TPAS-TN with a D–π–A structure had a large Stokes shift (213 nm), and possessed low background interference in cell imaging. By introducing a twisted triphenylamine group as the donor, TPAS-TN was endowed with AIE properties, and the positively charged pyridium unit was the acceptor, so that TPAS-TN exhibited good mitochondrial targeting ability and biocompatibility. Meanwhile, the π-bridge was composed of phenyl and dinitrophenyl (DNP) ether to make TPAS-TN exhibit "off–on" properties, low detection limit (69.5 nM), and high sensitivity and selectivity. Besides, TPAS-TN with the above characteristics was successfully applied to high-contrast H2S imaging in mitochondria. [ABSTRACT FROM AUTHOR]

In this report, we develop a drug delivery system by binding Argyreia sharadchandrajii (A. S.) biomass-derived carbon encapsulated on the surface of zinc oxide (ZnO) nanorods by a two-step method. Firstly, we prepared mesoporous carbon (MC) by pyrolysis under an inert atmosphere at 800 °C for 3 h. Simultaneously, hydrothermal synthesis of ZnO nanorods was performed, followed by composite formation with surface modification of ZnO nanorods with carbon particles. The physicochemical properties of the mesoporous carbon encapsulated ZnO nanorods were studied by using X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, Brunauer–Emmett–Teller (BET) analysis, etc. The mesoporous carbon encapsulated ZnO nanorods revealed a wurtzite hexagonal crystal structure. The SEM image showed the mesoporous carbon covered on the surface of the ZnO nanorod-like morphology with an average diameter of 300–400 nm and an average length of 1.2 μm. Based on these characterizations, we have reported several bioactivities like antioxidant, antimicrobial, anticancer, and drug delivery. The carbon/ZnO composite (C@Z) loaded with doxorubicin (DOX) (C@Z-DOX) manifested sustained drug release to live cancer cells. Taking into consideration the ubiquitous availability of carbon sources and the facile synthetic strategy of composites for promising drug delivery studies and bioactivities, this approach could acquire remarkable results in biomedical research. [ABSTRACT FROM AUTHOR]

The analysis of trace Fe(III) ions in water is of vital importance in the fields of biology, environment and health. The fluorescent switch technique based on photoluminescent carbon dots (CDs) is highly favorable due to their bio-adaptability, safety and economy, but it is hindered in the highly specific recognition at the trace level. In this work, oxytetracycline-derived CDs (denoted as OCDs) with a uniform size (ca. 2.04 nm), nitrogen dopant, and rich hydroxyl-/carboxyl- groups have been successfully fabricated via a bottom-up hydrothermal carbonization approach. The as-prepared OCDs have displayed excellent photoluminescence characteristics and fluorescence switch performance for the rapid detection of Fe(III) within 2 min with the limit of detection (LOD) as low as 0.440 μM (24.6 ppb) and the second highest sensitivity of 3.52 × 10−2 μM−1 among reported CDs-based Fe(III) fluorescent switch materials. This detection system is stable in the analysis matrix with many interfering metal ions, at least with the help of the masking agent cysteine, realizing the specific detection of Fe(III) in real water environments. The contributions from the fluorophore concentration and the affinity between fluorophore and quencher have been revealed by the numerical model, providing a roadmap for the design of metal ion fluorescence switch materials based on a complex formation quenching mechanism. Fluorescence cell imaging in plant cells has also been performed successfully with the as-synthesized OCDs. This work presents a high-performing CDs-based Fe(III) fluorescence switch derived from the environmentally-risky oxytetracycline, as well as a feasible strategy for recycling waste antibiotics. [ABSTRACT FROM AUTHOR]

Lipid droplets (LDs), owing to their involvement in various physiological processes and diseases such as fatty liver disease, diabetes, and cancer, have attracted considerable attention. Live cell imaging of lipid droplets allows researchers to visualize and track the movement of these organelles within living cells in real time. In this study, we synthesized trifluoromethyl-substituted cyanostilbene fluorophores containing naphthalene or julolidine groups to visualize lipid droplets in live cells and investigate the changes in the size and number of LDs upon oleic acid stimulation. The fluorophores with donor (D) and acceptor (A) substituents show strong solvatochromism due to intramolecular charge transfer (ICT). In addition, these fluorophores show enhanced aggregation-induced emission (AIE) in water, and the lipophilic trifluoromethyl substitution aids the formation of stable organogels. The morphology and size of the aggregates obtained were characterized through scanning electron microscopy and dynamic light scattering experiments. Rheology and differential scanning calorimetry were used to further characterize the organogels. Our findings suggest that these D–π–A-substituted cyanostilbenes are valuable probes for understanding live-cell LD dynamics. [ABSTRACT FROM AUTHOR]

Herein, we report two soluble and highly fluorescent triazine-based conjugated polymer networks (TCPNs) by conjugating a thiophene (donor) unit with a triazine ring (acceptor) through a phenyl linker. The 3-substituted thiophene moiety with alkyl and oligoethylene glycol side chains is rationally introduced into the polymeric network to improve its solubility and the effect of the side chain polarity on its optical, band gap, conductivity and biological activities was also investigated. When both TCPNs were reacted with a Lewis acid and base respectively, significant optical switching and a conductivity change were observed, indicating efficient non-oxidative doping/de-doping. Both TCPNs exhibit remarkable stability after several switching cycles from their neutral to doped states and vice versa. Doping of the TCPN through the addition of a Lewis acid is also studied via DFT, which clearly shows a narrowing of the band gap. To the best of our knowledge, this may be the first demonstration of the non-oxidative doping of a triazine-based CPN to control the conjugation, color and conductivity. Furthermore, these TCPNs show gelation after doping with a Lewis acid, resulting in the formation of a conducting gel. It is also observed that both TCPNs can enter cells to simultaneously exhibit abilities of fluorescence imaging and cancer cell inhibition. Thus, the described study showcases the potential scope of tuning the optical properties of triazine-based conjugated polymer networks for electronic and optoelectronic applications, as well as the probable use of these polymers for cell imaging and chemotherapeutic applications. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) prepared from biomass exhibit excellent potential for use in sensing and bioimaging due to their charming properties. In this paper, CDs were successfully synthesized from Plumeria alba flowers as the raw material by a low-cost and green hydrothermal method for the first time and exhibited good water solubility. Ammonia and sodium hydroxide were added to the biomass solution to regulate the luminescence of the CDs. Among them, blue fluorescent CDs (B-paCDs) synthesized with ammonia as the solvent were used to specifically identify and detect Cu2+ in water. Linearity within a range of 0.1–100 μM was achieved, with an LOD of 0.08 μM. Green fluorescent CDs (G-paCDs) synthesized in a sodium hydroxide solvent were applied for pH detection. When the pH increased from 2 to 9, the green fluorescence emission region showed significant linear enhancement. In addition, a smartphone-based handheld platform was employed to directly capture and analyse fluorescence photographs, which could be further extended to the analysis of river water samples. Finally, two kinds of CDs were applied for the fluorescence imaging of living cells (HepG2 cells). The constructed platform indicates that the as-synthesized CDs have promise for applications in the fields of sensing and bioimaging. [ABSTRACT FROM AUTHOR]

Mercury ion (Hg2+) contamination is very hazardous and harmful to the natural environment and human health. The development of small molecule fluorescent probes for the rapid detection of Hg2+ is of great significance. In the present work, an "AIE + ESIPT" mechanism-based benzothiazole derived fluorescent probe was applied to Hg2+ detection and displayed excellent selectivity, good anti-interference ability, low detection limit (2.85 × 10−9 M), and a large Stokes shift (170 nm) in the DMF/H2O mixture solution with fw = 60% H2O volume fraction. The fluorescence response mechanism, involving the desulfurization reaction of O-(2-(benzo[d]thiazol-2-yl)-6-formyl-4-methylphenyl)dimethylcarbamothioate (probe L) with Hg2+ to release the "AIE + ESIPT" fluorophore, was well established based on the UV-vis, 1H NMR, and HRMS spectral analyses. The practical application evaluation indicates that probe L could be used to precisely determine Hg2+ in live cell imaging, natural water, and seafood samples. [ABSTRACT FROM AUTHOR]

A novel strategy for the construction of functionalized N-arylamino-3,5′-biquinoline has been developed. The reaction involves base-mediated Knoevenagel condensation between 2-chloro-3-formylquinoline and α,α-dicyanoolefines followed by a Michael addition and [1,5]-H shift, then the occurrence of intramolecular cyclization and an aromatization tandem reaction in the presence of Et3N to make the target products. The reaction proceeds smoothly in EtOH at mild temperature to give the target compounds in modest to high yields (up to 92%) under ultrasonic irradiation. Single-crystal X-ray analysis was performed to confirm the structure of one of the typical products. In addition, the photophysical characteristics of the products were investigated through absorption and emission spectroscopy. This analysis reveals that the new heterocyclic system has impressive fluorescence characteristics. The anticancer activity in vitro was evaluated to determine anti-proliferative activity and toxicity against breast cancer for the target products. Moreover, the results show that the obtained IC50 value for the 3c compound was lower than the others for MCF-7 cells than the untreated group that exhibited anti-proliferative activity and high toxicity against breast cancer cells. Furthermore, the 3c compound has high potential for use in cellular imaging with excellent photostability and chemical stability. [ABSTRACT FROM AUTHOR]

Carbon polymer dots are a kind of emerging carbon dots and generally synthesized by a bottom-up method. Because of the diversity of the reaction processes and product structures, the luminescence of carbon polymer dots is different, which induces indeterminate luminescence mechanisms. Hence, confirming the luminescence mechanism of carbon polymer dots is significant for developing applications. In this work, the prepared carbon polymer dots exhibited solvatochromism after dissolution in different solvents. Then, after theoretical model analyses, it was found that the emission of carbon polymer dots was derived from molecular luminescence related to hydrogen bond effects. In addition, the luminescence of carbon polymer dots was mainly affected by hydrogen bonds between the surface groups of carbon polymer dots and the solvent molecules. Moreover, detection of trace water in organic solvents was realized based on the super sensitivity of carbon polymer dots to the polarity of organic solvents. And, using different polymers, which had different strengths of hydrogen bonding, modified carbon polymer dots were prepared for multi-color cell imaging. This work not only reveals the luminescence mechanism of carbon polymer dots synthesized using phenylenediamine as the precursor but also explores the detection and bio-imaging applications of carbon polymer dots synthesized from small molecules. [ABSTRACT FROM AUTHOR]

A series of fluorescent mono- (1–4) and bis-pyrene derivatives (5–7) were synthesized and their photophysical and self-aggregation properties in solution were fully investigated by UV-vis and fluorescence spectroscopies and dynamic light scattering (DLS). While in dilute DMSO mono-pyrene derivatives 1–4 show the characteristic features of monomer emission, bis-pyrene derivatives 5–7 display both monomer and excimer emissions, the latter attributable to a dynamic process. The gelation behaviour of these compounds was also studied, and only mono-pyrene leucine derivative 1 was found to display efficient gelation in aromatic solvents, such as toluene and p-xylene, and in a polar solvent mixture, water/DMSO (4 : 1 v/v). Finally, mono-pyrenes 1–4 showed no apparent cytotoxic impact on A549 and RD cell lines; derivatives 1–5 showed accumulation within both live and fixed cells, and macropinocytosis was found to be the main pathway for 5 to enter into the cells. [ABSTRACT FROM AUTHOR]

A highly sensitive, reversible, reusable and fluorogenic "turn-on" probe (HBTC) is fabricated for the sole detection of Al3+. On incremental addition of Al3+ in a solution of HBTC in ACN : H2O (4 : 1), a sharp "turn-on" emission enhancement is observed at 480 nm. The reversibility of the probe (HBTC) was displayed on the addition of F− solution. The detection limit is found to be of the order of 10−9 M which suggests that HBTC can detect Al3+ at a very minute level. The mechanism for Al3+ detection in ACN : H2O (4 : 1) is attributed to forbidding C＝N isomerization and ESIPT process simultaneously turning on the chelation-enhanced fluorescence process. The reusability and real-time application of the probe are also studied. Bioimaging study reveals that HBTC can detect Al3+ in human breast cancer cells (MDA-MB-231). Electronic structure of the probe is explained by density functional theory. [ABSTRACT FROM AUTHOR]

Exploring the changes in intracellular viscosity in response to inflammatory stress is of great significance for the detection and treatment of various diseases. For this purpose, we synthesized a viscosity-sensitive fluorescent probe VisP, which was constructed with carbazole as the fluorophore and indole salt as the rotor. The probe VisP emitted weak red fluorescence in low viscosity media, and strong red fluorescence in highly viscous solvents, exhibiting a drastic viscosity dependence and linear correlation (R2 = 0.996). The spectral tests and cell imaging experiments jointly confirmed the satisfactory photostability of the VisP. In addition, the MTT test results showed that the probe has low cytotoxicity, further supporting the application prospect of the probe in biological systems. By using the probe VisP, changes in the viscosity in nystatin and monensin-induced cells were tracked in situ, revealing the phenomenon of increased physiological viscosity in response to inflammatory stress. Moreover, the fluctuation of viscosity in dexamethasone sodium phosphate treated inflamed cells has also been sensed. This work not only provides an important tool for inflammation research, but also provides a new perspective for the study of viscosity-related diseases. [ABSTRACT FROM AUTHOR]

Selenite (SeO32−), as the most toxic form of selenium in water, is a great threat to water quality and human health, which also has been closely associated with various physiological and pathological processes. The sensitive detection and quantification of SeO32− are imperative for the early diagnosis and prevention of selenite-associated disease. Herein, we constructed novel o-phenylenediamine functionalized carbon quantum dots (OPD-CQDs) by a one-step hydrothermal method. The OPD-CQDs exhibited good water solubility, high quantum yield, strong photostability, excellent biocompatibility and cell imaging capabilities, and also displayed high selectivity and sensitivity to SeO32− with an excellent linear relationship and a low limit of detection (86 nM). Moreover, the OPD-CQDs were successfully employed for the quantitative determination of SeO32− in tap water and human serum with high accuracy and recovery rate. In particular, the designed OPD-CQDs were successfully applied for intracellular SeO32− detection with excellent biocompatibility and cellular imaging capability. The present research demonstrated that OPD-CQDs provided a novel approach for imaging and detecting SeO32− in live cells and in vivo. Based on these excellent properties and comprehensive applications, OPD-CQDs illustrated great potential to offer a scientific and effective method for SeO32− detection in complex environments and clinical early diagnosis of SeO32− related diseases. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) are carbon nanomaterials with fluorescent properties. Due to their unique structure and optical properties, CQDs have become a research hotspot in recent years. In this paper, iodine-doped CQDs (I-CQDs) with high photoluminescence (PL) (fluorescence quantum yield ∼ 36.2%) were innovatively prepared using a self-doping method with p-iodobenzoic acid as the only precursor. The average particle size of the I-CQDs is 6.42 nm, the maximum excitation wavelength is 330 nm, and the maximum emission wavelength is 408 nm. Fluorescence-sensing experiments showed that the I-CQDs could be used as a 'turn-off' fluorescence sensor for Fe3+, with a detection limit of 0.47 μM. The cause of the fluorescence quenching can be attributed to dynamic quenching and the inner filter effect. When the sensor detects ferric ions in actual water samples, the spiked recoveries are 99.2% to 107.5%, with good reproducibility and high accuracy. Moreover, I-CQDs with their lower cytotoxicity could be used for the imaging of HeLa cells over longer times and as a new type of fluorescent labeling material for environment monitoring, cell labeling, and cellular imaging. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) with good biosafety can be doped with metals to construct multimodal imaging probes with a wide range of applications in fluorescence and molecular imaging. However, developing CQDs with both long-wavelength emission and a variety of imaging modes remains a challenge. In this article, novel bismuth- and gadolinium-codoped carbon quantum dots (Bi,Gd-CQDs) were developed using a hydrothermal method for green and red fluorescence imaging, X-ray computed tomography (CT) imaging, and T1-weighted magnetic resonance imaging (T1-weighted MRI). In addition to exceptional water solubility, strong steady fluorescence characteristics, and great biocompatibility, the obtained Bi,Gd-CQDs have a high X-ray attenuation coefficient and a short magnetic resonance T1 relaxation time. Additionally, cell imaging involved red fluorescence imaging with deep penetration. Therefore, the prepared Bi,Gd-CQDs with green and red dual-emissions can be used as nanoprobes for fluorescence, CT, and T1-weighted MR imaging, expanding their application prospects in the field of biomedicine. [ABSTRACT FROM AUTHOR]

Interlinked aggregation induced emissive (AIE) fluorophores (triphenylamine (TPA) donor (D) and indanedione acceptor (A)) via non-conjugated spacers (1–3) showed concentration-dependent tunable fluorescence from blue to deep red/NIR in solution and deep red emission in the solid-state. 1–3 exhibited weak broad solid-state fluorescence covering the blue to deep red region (433 to 706 nm, ΦF = 2.3 to 5.3%). It is noted that the non-interlinked TPA-indanedione fluorophore was non-emissive in solution but showed strong solid-state fluorescence at 611 nm (ΦF = 17.7%). In contrast, 1–3 showed strong fluorescence in the solution state (ΦF = 0.001 to 0.09 compared to fluorescein). Importantly, 1–3 exhibited concentration-dependent tunable fluorescence from blue (457 nm) to deep red/NIR (720 nm) in CHCl3 due to varied aggregation of fluorophores. Dynamic light scattering (DLS) studies confirmed the molecular aggregation even at very low concentrations (10−7 M). The increasing concentration lowered the solubility and produced bigger aggregates with wide size distribution that caused tunable fluorescence. The deep red fluorescence of 1 was utilized for live-cell imaging applications using E. coli cells. Fluorescence microscopic images revealed clear red fluorescent E. coli cells with a rod morphology. Furthermore, the non-toxic nature of 1 was confirmed by in vitro as well as in vivo studies. Thus, deep red/NIR emissive fluorophores were achieved by interlinking two AIEgens using a non-conjugated spacer and utilized for live cell imaging. [ABSTRACT FROM AUTHOR]

A new strongly luminescent homodinuclear Eu2III-based bioprobe, [Eu2(tta)6(μ-pz(tpy)2)] (1), was developed, where piperazine-4-methyl-phenyl terpyridine (L) (μ-pz(tpy)2) acts as a bridging ligand containing piperazine (pz) as a linker between two N3-donor phenyl-terpyridine ends and thenoyltrifluroacetone (tta) acts as a capping antenna ligand. The Eu2III bioprobe 1 was designed to show pH responsiveness via its acid-sensitive β-diketonate (tta) ligand and to be a fluorescent cell imaging agent, utilizing the characteristic dual-antenna-sensitized red luminescence of EuIII ions via intraconfigurational f → f transitions. The structure of the μ-pz(tpy)2 ligand utilizes the ideal disposition and potential binding capabilities of the terminal N3-donor tpy moieties toward EuIII ions. The dinuclear complex 1 is characterized using ESI-MS, FT-IR, and other spectroscopic methods; therein, each EuIII atom is coordinated to six oxygen atoms from three anionic tta− ligands and one N3-donor terminal terpyridine to achieve the proposed nine-coordinated {EuN3O6}-geometry. The coordinative saturation, thermodynamic stability, absence of exchangeable labile H2O molecules (q < 1), and the presence of C–F oscillators in the tta ligands minimize possible emission quenching via non-radiative vibrational energy transfer (VET). These design features of 1 result in bright luminescence, photostability, and a long luminescence lifetime in aqueous media, which are desirable for cellular imaging applications. It shows efficient binding interactions with CT-DNA (Kb: ∼106 M−1) and serum albumin protein (BSA) (KBSA: ∼106 M−1) under physiological conditions. The subcellular localization of the Eu2III bioprobe 1 was evaluated using the MCF-7 and MDA-MB-231 cancer cell lines via confocal laser scanning microscopy (CLSM). It showed significant cellular uptake and preferential nucleolus localization, utilizing intrinsic red emission derived from the f–f transitions of the EuIII ions of the Eu2III bioprobe 1. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2), as a biomarker in a series of physiological processes, plays a crucial role in investigating the pathogenesis of some diseases. The highly sensitive and selective detection of H2O2 release from living cells has aroused tremendous research interests. Herein, a non-enzymatic electrochemical H2O2 biosensor was constructed based on AgPt bimetallic nanoparticle-structured MoS2 nanohybrid (AgPt/MoS2) as an electrocatalyst. The AgPt/MoS2 nanohybrid was successfully synthesized by a facile wet-chemical method. Compared with AgPt nanoparticles, the AgPt/MoS2 nanohybrid exhibited significant enhancement in catalytic performance towards H2O2. The main factor is that MoS2 nanosheets as a supporting material promote AgPt nanoparticles to expose more active sites. The electrochemical response of the AgPt/MoS2 hybrid-based biosensor to H2O2 was linear in the range of 20 μM–4 mM, and the detection limit was calculated as 1.0 μM. To prove practicality, the biosensor was further applied to detect H2O2 release from living SMMC-7721 cells. These results indicate the potential applications of the developed biosensor in monitoring physiological processes. [ABSTRACT FROM AUTHOR]

Four novel compounds (S-DCM-1O, S-DCM-2O, S-DCM-3O, and S-DCM-4O) based on sulfur-substituted dicyanomethylene-4H-chromene (S-DCM) and diarylethene were synthesized. The detailed investigations on the fluorescence spectra, absorption spectra, and time-dependent density functional theory calculations (DFT/TD-DFT) were presented. The encapsulation of mPEG2000-DSPE effectively increased the solubility of all the as-prepared samples. The results of TEM showed that the nanoparticles had a good dispersion coefficient. All the nanomaterials (S-DCM-1O@PEG, S-DCM-2O@PEG, S-DCM-3O@PEG, and S-DCM-4O@PEG) exhibited near-infrared emission (650–900 nm) and thus reduced light damage and light scattering for cell imaging in biological applications. Furthermore, PLL (poly- L -lysine hydrobromide) was used to modify the surface of nanoparticles to facilitate easy uptake by A549 cells by changing their electronegativity. The results suggested that S-DCM-2O@PEG@PLL was a highly suitable candidate for cell imaging because of its low toxicity and excellent biocompatibility. [ABSTRACT FROM AUTHOR]

For the purpose of turning waste into treasure, acid orange 7 (AO7), a commonly used azo dye, has been explored as a precursor to synthesize carbon nanodots (CNDs) by a simple, green and economical route, without the utilization of strong acids or other oxidizers. Detailed characterization of the synthesized CNDs reveals their good water dispersibility, with a mean particle size of 3.54 nm and a thickness of 0.5–1.6 nm (2–4 layers). Importantly, the much-reduced biotoxicity and excellent fluorescence properties of the synthesized CNDs lead to their further potential applications in both bioimaging and selective detection of Fe3+ ions. [ABSTRACT FROM AUTHOR]

Four new 9,10-dithienylanthracene-based triphenylamine derivatives (TPA-DTAs) were designed and synthesized by adjusting the linkage model of the phenylacetonitrile group with different substituents. They all displayed aggregation-induced emission enhancement (AIEE) features and large Stokes shifts (>150 nm), as well as reversible mechanofluorochromic (MFC) behaviors upon grinding-dichloromethane fuming. Substituent effects indicate that the electron-donating methoxy can efficiently increase the fluorescence quantum yield and shorten the maximum emission wavelength, while the electron-withdrawing trifluoromethyl can induce a remarkable red-shift of the emission wavelength due to the twisted intramolecular charge transfer (TICT) effect. Additionally, the TPA-DTAs displayed low cytotoxicity and have been successfully applied to living cell imaging. This work will provide a reference for the design and development of functional AIEE dyes in a wide range of applications based on the TPA-DTA-skeleton. [ABSTRACT FROM AUTHOR]

Facile and accurate detection of dopamine (DA) in biological samples is crucial for diagnostic needs. This study reports a portable colorimetric fluorescent probe for the tracing of DA based on orange-red emitting Au nanoclusters (AuNCs). The AuNCs were reduced and stabilized with L -methionine by strictly controlling the reaction conditions. The resultant L -methionine capped AuNCs (M-AuNCs) exhibit bright and stable orange-red emission with a quantum yield of 31.08%. The excitation/emission wavelength is located at 420 nm/610 nm, and the large Stoke's shift of 190 nm endows the M-AuNCs with great potential as a late-model sensing probe for life studies and environmental science. The M-AuNCs exhibit unique specificity and excellent sensitivity for tracing DA by an "on–off" strategy with a lower limit of detection (LOD) of 3.96 nM (S/N = 3) within a linear range of 10–100 nM. Notably, the colorimetric detection results can be explored as a visual sensor for sensitive, reliable and real-time/on-site detection of DA with the assistance of a smartphone. The LOD can be determined as 81.94 nM within a wide linear range of 0.1–1.0 μM by a smartphone. Furthermore, the M-AuNCs as a late-model potable probe allow simple and rapid discrimination of DA in serum, and the cellular imaging of the M-AuNCs indicated that the detection of DA can also be achieved in living cells, demonstrating their great feasibility for the tracing of DA in real samples. [ABSTRACT FROM AUTHOR]

Tyrosinase (TYR), a copper-containing oxidase, has emerged as a predictive biomarker for certain cancers. It is still challenging to develop highly sensitive and selective fluorescent probes for monitoring TYR in biological systems. In this study, we designed a novel fluorescent probe to detect TYR through the nucleophilic substitution reaction of 3-bromomethylphenol with the fluorescent dye 4-methylumbelliferone. Under the catalytic oxidation of TYR, the recognition group of the probe was oxidized to o-benzoquinone, and then a cleavage reaction took place to remove the recognition group and release the fluorophore, so that the fluorescence recovered. The enhancement of the fluorescence intensity was directly related to the activity of TYR. The probe showed high selectivity and sensitivity to TYR with a LOD of 0.2 U mL−1. The feasibility of this probe in real sample assays and cell imaging was also investigated with satisfactory results, providing a practical strategy for detecting TYR activity in biological systems. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) fluorescence imaging with the merits of deep tissue penetration and high signal to background ratio is widely adopted in disease diagnosis, controlled drug delivery and the in situ and real time monitoring of biological procedures. In particular, the use of aggregation-induced emission luminogens (AIEgens), which feature a large Stokes shift, superior photostability and high brightness, has further expanded the practical application of fluorescence imaging. Here in this article, we utilized 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC) as the electron acceptor (A) and aromatic aldehydes as the electron donor (D) to fabricate NIR AIEgens. Accordingly, six AIEgens, namely, NIC, 6-MNIC, 6-HNIC, 4-MNIC, DMPIC and DMNIC, were obtained. The photophysical properties plus theoretical calculation results verified that the introduction of D–A interactions successfully redshifted the emission maxima of the obtained AIEgens. DMNIC, with a 4-(dimethylamino)naphthalen-1-yl group as the electron donor moiety, exhibited the longest emission maximum at 694 nm in pure DMSO. The low cytotoxicity and good cell imaging ability toward HeLa cells further guaranteed that DMNIC would provide good prospects for future applications in chemo/biosensing, disease theranostics or diagnosis, controlled drug delivery and release, and deep tissue imaging. [ABSTRACT FROM AUTHOR]

The combination of complementary optical imaging and magnetic resonance imaging (MRI) techniques evolved to provide an even more powerful tool to simultaneously obtain both molecular information and anatomical information as well as to dramatically improve the accuracy of detection. Herein, we report a new tumor-targetable bimodal time-gated luminescence (TGL)–MRI nanoprobe for tracing cancer cells in vitro and in vivo. The nanoprobe was constructed by coating superparamagnetic Fe3O4 nanoparticles with functional silica shells that encapsulated luminescent Eu3+ complexes and were decorated with tumor-targeting molecules, folic acid (FA), on the surface. The fabricated nanoprobe possesses strong long-lived luminescence and excellent magnetic properties, as well as outstanding stability, biocompatibility and dispersibility in water. Furthermore, the nanoprobe can specifically bind to FA receptor-overexpressed cancer cells, allowing it to be accumulated in these cells. These features enable the nanoprobe to be successfully used for TGL imaging of cultured cancer cells and bimodal TGL–MR imaging of tumors in tumor-bearing mice with high sensitivity and accuracy. The research outcomes will contribute to the development of a new bimodal optical/MR imaging nanoprobe for the tracing and precise detection of cancerous cells. [ABSTRACT FROM AUTHOR]

An efficient protocol has been developed for the synthesis of a novel fluorescent probe, 1,2-disubstituted-indeno[1,2,3-gh]phenanthridine, derived from a series of a-oxo-ketene dithioacetals (OKDTAs) and indenoquinoline under essential conditions via a [4+2] annulation in excellent yield. All the synthesized indenophenathridine derivatives were well characterized by NMR and mass spectrometry. One of the synthesized indenophenanthridine derivatives, 4b, has been involved in acidochromism studies, selectively sensing Fe3+ ions in non-aqueous solution with a low detection limit (7.5 - 10-7 M) applied in live-cell bio-imaging. [ABSTRACT FROM AUTHOR]

Numerous SO3²-/HSO3- fluorescent probes have been reported based on various mechanisms. However, most probes are constructed from classic dyes such as coumarin, BODIPY, and cyanine. The development of a new fluorophore with excellent performance is still required. CRL-1, a turn-on fluorescent probe based on indolizines, was developed for the detection of sulfite. Compared with other analytes, probe CRL-1 showed a short response time (within 10 s) and excellent selectivity and had strong fluorescence emission at 458 nm. The probe's LOD was 8.1 mM. Furthermore, cell imaging experiments suggested that the probe can be useful in biological systems. [ABSTRACT FROM AUTHOR]

An azo armed Schiff base chemosensor was synthesized based on a naphthalene fluorophore, which transduces greenish-yellow emission by complexing with Al3+. It emits greenish-yellow fluorescence through restricted C＝N isomerization, chelation-enhanced fluorescence, and the photo-induced electron transfer mechanism. The clear visible transformation of the achromatic ligand to a chromatic ligand by the 1 : 1 complexation with Al3+ is substantiated by ESI-MS spectra. 1H NMR, 13C NMR, and FTIR spectroscopies are used to characterize the HL. The selectivity of the HL for Al3+ in the presence of other metal ions was investigated through absorbance and fluorescence spectroscopies. The average lifetimes of HL and L–Al3+ have been evaluated using a time-resolved photoluminescence experiment to explore the sensing mechanism. The Al3+ sensing mechanism was also established by density functional theory calculations. A reversibility experiment was performed, demonstrating that Al3+ binding to HL is reversible. The pH variation on luminescence affirms that the HL can survive in physiological pH. Finally, the lower limit of detection of 5.4 × 10−7 and a good response in a cytotoxicity and cell imaging study confirm the usability of the ligand as an indelible signature of an effective biosensor for target Al3+. [ABSTRACT FROM AUTHOR]

This work describes the design and synthesis of three new Tröger's base appended bis-carbazole units via the oxidative coupling method aiming to achieve solid-state luminescent materials. We envisaged that the TB-appended bis-carbazolic unit will induce more twists in the molecule thereby affecting the optical properties, especially in the solid state, by preventing intermolecular π–π close stacking interactions. The careful control of the electronic attributes of these molecules by the systematic variation of the terminal rotatable groups allowed the preparation of novel luminescent materials possessing high thermal stabilities and favorable bandgaps for electron mobility indicating their potential applications as sensory materials or in optoelectronic devices. Consequently, one of the bis-TB materials demonstrated high biocompatibility against Escherichia coli and was found to effectively stain dead bacterial cells over live cells. Thus, this provides a promising strategy to assess bacterial cell death based on fluorescence on the addition of any antibacterial agent. [ABSTRACT FROM AUTHOR]

As a highly toxic organic compound, malononitrile can cause serious harm to human health and environment. However, methods for the rapid detection of malononitrile are rarely reported. Hence, this study provides a convenient and effective method for the detection of malononitrile using cinnamaldehyde compounds as a fluorescent probe DC-Mal. The fluorescence intensity of the probe has excellent linearity with the concentration of malononitrile, and the detection limit is as low as 18 nM. In addition, the probe has good selectivity and anti-interference, and only has good recognition effect on malononitrile. The color of the probe changed from light green to light pink for naked eye observation after the reaction. Most importantly, the probe can be used for the biological imaging of living cells and zebrafish. These results indicate that the probe can be used for the detection of malononitrile in organisms and environment. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) have been studied for years as one of the most promising fluorescent nanomaterials. Herein, fluorescent CDs excited by visible light emitted red fluorescence with a quantum yield of 32.8% via a facile hydrothermal treatment. In addition to being applied in cell imaging, the as-prepared CDs were also utilized in the detection of ammonia and formaldehyde in aqueous solutions because of their pH-dependent properties, with a low limit of detection of 3.7 nM and 44 μM, respectively. Furthermore, we synthesized flexible and transparent fluorescence films by mixing the as-prepared CDs and PVB powder, which can be utilized to directly detect ammonia gas under visible light according to significant colour changes. Therefore, the as-prepared CDs would have more prominent and influential application in clinical diagnostics and environmental analysis. [ABSTRACT FROM AUTHOR]

Mesoporous silica nanocarriers with dual/multifunctionalities are thought to be good candidates for dual/multimodal applications such as combined drug delivery and bioimaging. In this study, new red fluorescent organosilica materials were conveniently produced with diurea-ethidium bromide (DU-EB) functional units integrated in the pore wall framework for simultaneous diagnosis and therapy. We found that the prepared mesoporous silica hybrid nanocarrier system exhibited strong red fluorescence under UV-light (365 nm) while retaining excellent photo- and chemical-stability. The integrated ethidium bromide functional units in the mesopore walls cause the red fluorescence. By loading/releasing doxorubicin (Dox)/5-fluorouracil (5-FU) as a model cargo, the synthesized DU-EB@MSH materials were tested at various pH levels (pH 5.0, 6.2 and 7.4), and the cytocompatibility of the red-fluorescent DU-EB@MSH nanocarrier system was assessed using human breast cancer (MCF-7) cells. The experimental results revealed that the drug release behavior is primarily determined by the pH of the intracellular medium, and red-fluorescence was induced by a UV-light (365 nm) trigger. All the study results suggested that the DU-EB@MSH drug carrier system could be useful for red-fluorescence bioimaging and chemotherapeutic applications in cancer therapy. [ABSTRACT FROM AUTHOR]

Current research based on the development of promising anticancer chemotherapeutics is a great challenge to scientists to combat the pervasiveness of pernicious cancer. In line with this, the aim of this work is to develop a set of 9-arylacenaphtho[1,2-b]quinoxaline analogues with the capability of imaging, as well as terminating, cancer cells in the human body, exploiting the powerful anticancer activity of the quinoxaline and acenaphthene moieties. The rigid, planar disc like framework of acenapthoquinoxalines gives them the ability to intercalate to helical DNA via π–π stacking, and the fluorescence properties of these compounds has been increased with the extension of π-conjugation by introducing various aryl groups to the core moiety via a Suzuki coupling reaction. Precise cytotoxicity screening has revealed that compound 5a is the most potent and selective (with respect to HEK 293 cells) compound among all members of this series, showing IC50 values of 1.97 ± 1.29 μM, 3.06 ± 1.07 μM and 22.01 ± 0.77 μM against the human cervical cancer (HeLa), human breast cancer (MCF-7) and human brain cancer (U87MG) cell lines, respectively. Compound 5c has been recognised as the fluorescent imaging agent with the highest quantum yield (ϕ = 0.1458). Furthermore, the considerable cellular uptake, nucleus targeting aptitude and DNA damaging qualities of these compounds, and above all the annihilation of cancer cells, have been certified by flow cytometry, colocalisation studies, binding studies and DNA gel ladder assays, along with morphological analysis and scratch wound healing assays. [ABSTRACT FROM AUTHOR]

Thiol-containing small molecules such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) play a key role in a wide range of physiological processes. But it is a challenging work to distinguish these biothiols since they have a similar structure and reactivity. An "AIE + ICT" ratiometric fluorescent probe is synthesized by incorporating TPE into the coumarin ring through a Schiff-base C＝N. The sensing mechanism of the probe lies on the nucleophilicity of the sulfhydryl group and the adjacent amino group of Hcy/Cys, breaking the Schiff-base C＝N in the probe structure and forming a five or six-membered ring thiazolidine adduct. Only Hcy/Cys triggers an obvious ratiometric change from orange-yellow to blue. The ratiometric probe can detect Hcy/Cys quantitatively, and the lower limits of detection for Hcy and Cys are 0.554 μM and 1.816 μM, respectively. Moreover, the probe showed a slight preference for Hcy over Cys. The difference in the sensing behavior of the probe for Hcy/Cys is believed to be the consequence of the more highly efficient ICT and PET of thiazolidine adducts. Preliminary studies show that the probe has low cytotoxicity, is cell-permeable and can be employed for the ratiometric fluorescence imaging of exogenous and endogenous Cys in living cells. [ABSTRACT FROM AUTHOR]

A simple and unique dual-channel chemical probe (DH) was designed and synthesized, which not only realized sequential recognition of Cu2+ and CN− by colorimetric and fluorometric methods, but also realized fluorescence detection of CN−. When different cations (Co2+, Mg2+, Ni2+, Cd2+, Hg2+, Al3+, Ag+, Cu2+, Pb2+, Fe3+, Zn2+ and Ca2+) were added into the solution containing the probe molecule DH, only Cu2+ induced an observable change in the UV-vis and fluorescence spectra, indicating that the probe molecule can be applied for specific recognition of Cu2+. The anti-interference experiment of DH to Cu2+ showed that DH has good selectivity for detecting Cu2+, with a detection limit of 7.05 × 10−7 M. In particular, the fluorescence "ON–OFF–ON" process can be recycled by sequentially adding Cu2+ and EDTA, and the fluorescence intensity remained unchanged after ten times. This observation suggested that DH can achieve reversible highly sensitive response to Cu2+ and EDTA, and can be used as a hypersensitive logic gate for Cu2+ detection. More interestingly, when different anions (CH3COO−, SO32−, H2PO4−, ClO4−, NO3−, HSO4−, I−, Cl−, F−, Br−, N3− and CN−) were added into the solution containing DH and Cu2+, only CN− induced color change of the solution from red to yellowish green, and the fluorescence intensity greatly enhanced, indicating that DH-Cu2+ has a specific response to CN−. The anti-interference experiment showed that DH-Cu2+ has good selectivity for CN−, with a detection limit of 8.11 × 10−6 M. Moreover, the probe molecule DH can detect CN−, with a detection limit of 7.61 × 10−6 M. Experimental and theoretical methods were applied to deeply study the detection mechanism of DH, present great potential in practical application for ion test strips and HeLa cell imaging reagents. [ABSTRACT FROM AUTHOR]

Silica nanoparticles have attracted a huge bioaudience as these are biosafe materials for targeted delivery applications due to their ease of functionalisation, less toxicity, and bio-compatibility. However, poor knowledge of the interaction mechanism between silica nanoparticles and protein causes less development of silica-based fluorescent probes for practical applications. Hence, in this work, the interaction mechanism and structural changes in BSA caused by silica nanoparticles with different functional groups have been studied. First dye-supported silica nanoparticles with hydroxyl terminal (DSN) and amine terminal (DSFN) were synthesized by a modified Stober process. The dye supported on silica nanoparticles resulted in improving the photostability, with less toxicity when compared to the bare dye system. To improve the bioavailability, BSA was conjugated with both hydroxyl (BSA–DSN) and amine functionalised dye supported silica nanoparticles (BSA–DSFN). To understand the structural modification induced by silica with different terminals, nanoparticles were incubated with BSA (Bovine Serum Albumin) for 48 h. Then, the structural changes caused by BSA interacting with silica nanoparticles were evaluated using various techniques such as UV-VIS spectroscopy, fluorescence spectroscopy, CD (circular dichroism), and lifetime measurements. Longer lifetime emphasized the stable photophysical properties of BSA conjugated dye supported silica nanoparticles for live-cell imaging. These interaction studies generated knowledge on structural modification induced by BSA adsorption on silica nanoparticles and its bioavailability for cell imaging. The circular dichroism measurement divulges that the stabilisation of the secondary structure and improved thermal stability of BSA were attained after conjugating with silica nanoparticles. Cell toxicity and imaging results showed that BSA conjugated with amine-functionalised silica nanoparticles BSA@DSFN proved to be an ideal candidate for long-life fluorescent probes for cellular imaging application. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of the structures formed by self-assembly of 4-chloro-2(3H)-benzothiazolone (CBT) into panchromatic fibres and their application in cellular imaging. The aggregation properties of the synthesized compound were studied extensively under different solvents and concentrations and their morphologies examined at a supramolecular level by various microscopic techniques such as atomic force microscopy (AFM), fluorescence microscopy, and optical microscopy. Interestingly, the self-assembled structures formed by CBT reveal panchromatic emission properties and show blue, green, and red fluorescence under different excitation wavelengths. The mechanism of structure formation of the self-assemblies was studied through different techniques such as concentration-dependent 1H-NMR, ATR-FTIR, UV-visible spectroscopy, and fluorescence spectroscopy. Finally, the utility of CBT for cell imaging applications was demonstrated and it can be noted that CBT was efficiently taken up by mammalian cells and the cells revealed panchromatic emission in the blue, green, and red channels. The intensities of the fluorescence observed were blue > green > red and the dye interestingly does not exhibit any fluorescence quenching. [ABSTRACT FROM AUTHOR]

Water-soluble conjugated polymers (WSCPs) with the dual capability of two-photon imaging and singlet oxygen (1O2) production have become one of the most promising agents for noninvasive imaging guided photodynamic therapy (PDT). To obtain good imaging and PDT effects, two-photon excited (TPE) red-emitting WSCPs with good biocompatibility and 1O2 production capability are highly needed. Herein, a novel zwitterionic red-emitting WSCP P1′′ and its cationic analogue P1′ were synthesized and studied by comparison. The backbones of both polymers consisted of electron-rich poly[9,9′-bis(2-(2-(2-bromoethoxy)ethoxy)ethyl)fluorene-2,7-ylene vinylene] doped with a small amount of electron-deficient red-emitting unit, 4,7-bis(2-thienyl)-2,1,3-benzothiadiazole (TBT). Both P1′ and P1′′ achieved TPE red-emission through fluorescence resonance energy transfer (FRET). However, when compared with P1′, P1′′ exhibited higher water-solubility and resistance to nonspecific binding in the physiological environment, which could lead to a 5-fold increase in cellular uptake. Moreover, two-photon cell imaging experiments indicated that more of P1′′ entered into HeLa cells than P1′ and located in the cytoplasm instead of adhering near the cell membrane. Furthermore, P1′′ displayed a 1O2 quantum yield of 61%, which was much higher than that of P1′ (39%). These results could be mainly attributed to the anionic sulfonate groups within the zwitterionic side chains, which probably not only further enhanced the water solubility, but also promoted the generation of 1O2 by facilitating the transfer of the singlet-to-triplet excited state. Hence, zwitterionic P1′′ was demonstrated to show potential as an excellent TPE red-emitting photosensitizer for two-photon imaging-guided PDT. [ABSTRACT FROM AUTHOR]