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Owing to their high significance in fundamental study and diverse applications, stimuli-responsive and fluorescent polymers, particularly those with cluster-triggered emission (CTE) featured by non-conjugated chromophores, have drawn tremendous attention in recent years. In this work, fluorescent and multi-responsive polysiloxane (FRPS) was synthesized by hydrolytic condensation polymerization of 3-aminopropyl methyl diethoxysilane (APMS) with 3-(N-isopropyl propionamide) iminopropyl methyl diethoxysilane (APMS-NIP), which was formed in situ through aza-Michael addition between APMS and N-isopropyl acrylamide. FRPS was not only highly sensitive to temperature, pH and CO2 in water, but also showed an enhanced and stimuli-adjustable fluorescence emission. The effects of monomer feeding, pH and CO2 on its lower critical solution temperature and fluorescent property were investigated. FRPS fluorescence emission was ascribed to CTE mechanism. In addition, FRPS was shown to be highly potential as physiological indicator for cell imaging, and for controlled release and trace detection of doxorubicin. This study provides therefore a type of stimuli-responsive and fluorescent material for potential applications in biomedical fields, and it is also of great significance for understanding of the fluorescence mechanism of polysiloxane-based stimuli-responsive polymers. [ABSTRACT FROM AUTHOR]

Organic fluorophores with dual-state emission (DSE) are rare or difficult to observe because most of them display either aggregation-induced emission (AIE) or aggregation-caused quenching (ACQ). Amazing works have been accomplished, yet most of the DSE compounds were excited by UV light which limits their wide application in bioimaging. In this work, we achieved a visible-light excited DSE fluorophore and realized its imaging in SKOV-3 cells and zebrafish. The naphtho[2',3':4,5]imidazo[1,2-a]pyridine (NIP) core ensures its emission in dilute solution. Meanwhile, the twisted phenyl ring blocks fluorescence quenching induced by the π-π stacking and leads to the emission of the solid. The fluorescence intensity is steady even after 6 h of continuous intense sunlight. More importantly, photostability of NIP in cells is much better than commercial dye (mitochondrial green). [ABSTRACT FROM AUTHOR]

New portable hydrogel sensors for Al3+ and Fe3+ detection were designed based on the aggregation-induced emission (AIE) and color change of N-doped carbon dots (N-CDs). N-CDs with yellow fluorescence were prepared by a one-pot hydrothermal method from 2,5-dihydroxyterephthalic acid and acrylamide. The fluorescence of N-CDs was enhanced by Al3+ about 20 times and quenched by Fe3+. It was interesting that although Fe3+ showed obvious quenching on the fluorescence of N-CDs it did not cause a noticeable change in the fluorescence of N-CDs + Al3+. The colorless solution of N-CDs appeared blue in the presence of Fe3+ without the influence of Al3+. Therefore, the turn-on fluorometry and colorimetry systems based on N-CDs were constructed for the simultaneous detection of Al3+ and Fe3+. Furthermore, the portable sensing of Al3+ and Fe3+ was realized with the assistance of hydrogel, filter paper, cellulose acetate, and cellulose nitrate film. The proposed approach was successfully applied to the detection of Al3+ and Fe3+ in food samples and cell imaging. [ABSTRACT FROM AUTHOR]

A dual-mode pH sensor based on nitrogen-doped carbon dots (N-CDs) with the source of o-phenylenediamine and tryptophan has been constructed. Under the stimulation of pH, the N-CDs exhibited prominent both color and fluorescence changes, leading to the rarely discovered colorimetric and fluorescent dual-readouts for the evaluation of pH. The mathematic relationship was established between pH and fluorescence intensity of N-CDs, and between pH and the UV–Vis absorbance ratio at 630 nm and 488 nm of N-CDs, respectively, over a quite broad pH range of 2.2 to 12.0. Multiple techniques are used to explore the dual-mode pH-responsive mechanism, and the preliminary explanation is put forward. The experimental results show that the N-CDs have visualized pH sensing applicability for actual samples, including various water samples and HeLa cell. Furthermore, the N-CD ink is developed for successful information encryption and anti-counterfeiting. This work might provide valuable insights into the sensing mechanism of CDs, and the application potential of CDs in broader fields. [ABSTRACT FROM AUTHOR]

Cyclodextrin (CD) is an important guest material owing to the water solubility and biocompatibility. In the paper, an organic small molecule was synthesized. According to supramolecular self-assembly, the organic molecule was bounded to the cavity of Poly β-cyclodextrin, which was characterized by IR, SEM and TEM et al. After self-assembly interaction, the morphology has changed obviously comparing with precursors. Simultaneously, the supramolecular self-assembly complex exhibited good water solubility. Moreover, By Gaussian calculation, the high binding activity between organic molecule and cyclodextrin was confirmed. By fluorescence investigation, the supramolecular system showed high fluorescence sensing activity for Zn2+ in pure water environment, which could track the dynamic change of Zn2+ in organisms. In addition, the supramolecular system exhibited low cytotoxicity. The work provided an interesting pathway for constructing water-soluble and low cytotoxic fluorescence sensor for Zn2+. [ABSTRACT FROM AUTHOR]

Phototoxicity is an important issue in fluorescence live imaging of light-sensitive cellular processes such as mitosis. Among several approaches to reduce phototoxicity, the addition of antioxidants to the media has been used as a simple method. Here, we analyzed the impact of phototoxicity on the mitotic progression in fluorescence live imaging of human cells and performed a screen to identify the most efficient antioxidative agents that reduce it. Quantitative analysis shows that high amounts of light illumination cause various mitotic defects such as prolonged mitosis and delays of chromosome alignment and centrosome separation. Among several antioxidants, our screen reveals that ascorbic acid significantly alleviates these phototoxic effects in mitosis. Furthermore, we demonstrate that adding ascorbic acid to the media enables fluorescence imaging of mitotic events at very high temporal resolution without obvious photodamage. Thus, this study provides an optimal method to effectively reduce the phototoxic effects in fluorescence live cell imaging. Ascorbic acid alleviates phototoxic effects of fluorescence live imaging in mitosis, allowing for very high temporal resolution without photodamage. [ABSTRACT FROM AUTHOR]

The present work highlights the sustainable approach for the transformation of plastic waste into fluorescent carbon dots (CDs) through carbonization and then they were functionalized with L-cysteine and o-phenylenediamine. CDs which were characterized by different analytical techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are employed to recognize Cu2+, Fe2+, and Hg2+ ions. The results show that the fluorescence emission was considerably quenched, and it is consistent with the interference and Jobs plots. The detection limit was found to be 0.35µM for Cu(II), 1.38 µM for Hg(II), and 0.51µM Fe(III). The interaction of CDs with metal ions enhances the fluorescence intensity detecting histamine successfully. It shows that plastic waste-based CDs can be applied clinically to detect toxic metals and biomolecules. Moreover, the system was employed to develop the cellular images using Saccharomyces cerevisiae cells with the support of a confocal microscope. Furthermore, theoretical studies were performed for the naphthalene layer (AR) as a model for C-dots, then optimized its structure and analyzed by using the molecular orbital. The obtained TD-DFT spectra coincided with experimental spectra for CDs/M2+/histamine systems. [ABSTRACT FROM AUTHOR]

In this paper, a novel amino acid surface-functionalized semiconductor CdTe quantum dot fluorescent probe amidated by carboxyl and amide groups was synthesized to detect pyrophosphate ions (P2O74−, PPi). L-Arginine (L-Arg) was grafted onto cysteine modified CdTe quantum dots (Mea-CdTe QDs) to form a new L-Arginine-functionalized quantum dot fluorescent probe (L-Arg@Mea-CdTe). The prepared probe has good optical properties with multiple grafted functional groups on the surface. The guanidine group of the L-Arg@Mea-CdTe fluorescent probe is strongly basic and will be fully protonated under physiological conditions. The resulting hydrogen bonds bound to pyrophosphate lead to significant changes in the fluorescence of CdTe quantum dots. IR and XPS characterization were performed to confirm it. The addition of PPi induces a significant fluorescence quenching of L-Arg@Mea-CdTe in aqueous solution. The fluorescent QDs probe can also detect pyrophosphate with good sensitivity and anti-interference performance. The detection limit of the L-Arg@Mea-CdTe fluorescence probe for PPi is as low as 0.30 μM. In addition, the novel nano-fluorescent probe was successfully applied to detect PPi in water and in cell imaging. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) have preeminent application prospects as a new star in the nanomaterials field. In this work, a green and facile method to synthesize the blue-emitting CDs was proposed with Melia azedarach leaves as the carbon precursors. Using nature materials without other expensive reagents and instruments, the processes were simple and environmental-friendly. The CDs had high fluorescence quantum yield (11.8%) and excellent luminescence properties. The size of them were among 1.5–2.5 nm and the emission spectrum exhibited a strong peak at 460 nm when excited at 380 nm. Additionally, the CDs were stable in most ions but sensitive to different pH values. As a result, a pH sensor was established for the detection of pH with a linear range of 3–10 pH. Moreover, it was demonstrated that the synthesized CDs had extremely low cytotoxicity. Due to their low toxicity and good biocompatibility, they entered into the A549 cells successfully for cell imaging. [ABSTRACT FROM AUTHOR]

Cysteine (Cys) is a significant biological mercaptan that achieves key roles in several important physiological processes, such as reversible redox homeostasis in living organisms. Abnormal levels of Cys in the human body are directly related to many diseases. In this work, we constructed a sensitive sensor (Cys-NR) by connecting a Cys recognition group to a Nile red derivative. Due to photo-induced electron transfer (PET), the Cys-NR probe showed little fluorescence at 650 nm. With the addition of Cys to the assay solution, the chlorine unit of the probe was substituted by the thiol group of Cys. Further, the amino and sulfhydryl groups in cysteine underwent an intramolecular rearrangement, which led to the Cys-NR probe water solution turning from colorless to pink with an enhancement in fluorescence. The red fluorescence at 650 nm increased about 20 times. Based on the turn-on signal, a selective Cys detection method is developed. The probe signal is not affected by various potential interferences or other competing biothiols and the limit of detection (LOD) is determined to be 0.44 μM. In addition, the probe is further employed for imaging of Cys in live cells, revealing good biological imaging ability that could provide a new way of intracellular Cys detection. [ABSTRACT FROM AUTHOR]

A series of nitrogen-doped photoluminescent carbon dots (N-doped CDs) with a proper quantum yield was prepared through microwave-assisted pyrolysis of citric acid and urea as the carbon and nitrogen sources, respectively. The obtained N-doped CDs were fully characterized by high-resolution transmission electron microscopy, elemental analysis, Fourier transform infrared spectroscopy, and X-ray diffraction pattern. The average size of the synthesized N-doped CDs was determined using high-resolution transmission electron microscopy analysis was approximately 7 nm and the interlayer distance was 0.29 nm, which was consistent with the results obtained by X-ray diffraction. The optical characteristics of the samples were determined by UV-Vis and photoluminescent spectroscopy. The aqueous solution of N-doped CDs showed a multicolor emission wavelength, in the range of 350 to 650 nm, dependent on the nitrogen-doped percentage. With increasing the nitrogen percentage, the emission spectra, depending on the excitation wavelength, have one or two peaks in the green and blue regions, which can be considered in applications such as special bioimaging and related fields. [ABSTRACT FROM AUTHOR]

Imidazo[1,2-a]pyridine derivatives have excellent potential for chelation with transition metal ions. Two new imidazo[1,2-a]pyridine-8-carboxylates were synthesized and characterized by 1H NMR, 13C NMR, HRMS, and single crystal-XRD techniques. Methyl carboxylate (probe 1) turns on fluorescence upon coordination with Zn2+, while sodium carboxylate (probe 2) turns off its fluorescence upon coordination with Co2+ or Cu2+ ions present in aqueous acetonitrile medium. 13C NMR study revealed that the change in metal ion specific binding was due to the involvement of carboxylate anion in complex formation with Co2+ or Cu2+ ions. The carboxylate anion at 8-position also enhanced the sensitivity of detection of probe 2 by an order of magnitude (detection limits: 3.804 × 10–7 M, probe 1/Zn2+; 0.420 × 10–7 M, probe 2/Co2+ and 0.304 × 10–7 M, probe 2/Cu2+). The detection limits of probes 1 and 2 comply well with the World Health Organization (WHO) and US Environmental Protection Agency (US-EPA) guidelines for detection of heavy metal ions present in drinking water and ground water. Both the probes form a 1:1 complex with Zn2+, Co2+ or Cu2+, and the stoichiometry was verified by Job plot and ESI-mass analysis. The sensing mechanism is explained using 13C NMR experiments, ESI-mass analytical data and theoretical DFT calculations. The suitability of probes 1 and 2 for on-site detection and quantitative determination of Zn2+, Co2+ and Cu2+ ions present in biological, environmental and industrial samples is demonstrated. In addition, both 1 and 2 are used for detection of intracellular contamination of Zn2+, Co2+ or Cu2+ ions in onion epidermal cells. [ABSTRACT FROM AUTHOR]

Metal cations such as Zn2+, Al3+, Hg2+, Cd2+, Sn2+, Fe2+, Fe3+ and Cu2+ play important roles in biology, medicine, and the environment. However, when these are not maintained in proper concentration, they can be lethal to life. Therefore, selective sensing of metal cations is of great importance in understanding various metabolic processes, disease diagnosis, checking the purity of environmental samples, and detecting toxic analytes. Schiff base probes have been largely used in designing fluorescent sensors for sensing metal ions because of their easy processing, availability, fast response time, and low detection limit. Herein, an in-depth report on metal ions recognition by some Schiff base fluorescent sensors, their sensing mechanism, their practical applicability in cell imaging, building logic gates, and analysis of real-life samples has been presented. The metal ions having biological, industrial, and environmental significance are targeted. The compiled information is expected to prove beneficial in designing and synthesis of the related Schiff base fluorescent sensors. [ABSTRACT FROM AUTHOR]

Conventional cellular protein detection techniques such as immunocytochemistry and flow cytometry require abundant cells, posing multiple challenges, including difficulty and cost for obtaining enough cells and the potential for clogging the instrument when using flow cytometry. Also, it is challenging to conduct cellular protein imaging and quantification simultaneously from a single experiment. We present a novel 3D platform, which integrates highly biocompatible cell-entrapped alginate hydrogel droplet array with gold-nanoparticle (AuNP)-based metal enhanced fluorescence (MEF), to achieve simultaneous imaging and quantification of proteins in intact cells in a sensitive manner. Compared to 2D immunocytochemistry, this 3D system allows for a higher cell loading capacity per unit area; together with the MEF-based signal enhancement from the embedded AuNPs, sensitive protein quantification was realized. Furthermore, compared to flow cytometry, this platform allows for protein imaging from individual cells. Taking the detection of EpCAM protein in ovarian cancer cells as a model, we optimized the AuNP size and concentration for optimal fluorescent signals. The 5 nm AuNPs at 6.54 × 1013 particles/mL proved to be the most effective in signal enhancement, providing 2.4-fold higher signals compared to that without AuNPs and 6.4-fold higher signals than that of 2D immunocytochemistry. The number of cells required in our technology is 1–3 orders of magnitude smaller than that of conventional methods. This AuNP-embedded hydrogel platform combines the benefits of immunocytochemistry and flow cytometry, providing increased assay sensitivity while also allowing for qualitative analysis through imaging, suitable for protein determination in a variety of cells. [ABSTRACT FROM AUTHOR]

AIE-active compounds have lately attracted considerable attention owing to their versatile applications, especially in OLED and bioimaging. Herein, a series of coumarin-3-formylhydrazone derivatives (CFH-1, 2, 3 and 4) were developed for investigating their AIE and solid-state luminescence behaviors. All the obtained compounds emit varying degrees of solid-state fluorescence. CFH-1 and 2 show the typical AIE characteristics, while CFH-3 and 4 exhibit stronger solution fluorescence than their aggregation-induced emission. The single crystal X-ray diffraction analysis of CFH-1 and CFH-3 showed that both of them adopt planar conformation and the CH···O hydrogen bonding plays a crucial role in their crystal packing. Meanwhile, there is a notable difference between them. Successive π-π stacking interaction was observed in the crystal packing of CFH-1, while the crystals of CFH-3 contain dimeric π-π stacking interaction. Their distinct crystal packing interactions result in their different fluorescence properties. Moreover, both CFH-1 and CFH-2 displayed excellent bioimaging performances in living cells. [ABSTRACT FROM AUTHOR]

Tyrosinase (TYR), an important biomarker for melanoma, offered significant information early detection of melanoma and may decrease the likelihood of mortality. Therefore, this article constructed a highly sensitive and selective green fluorescent functionalized carbon quantum dots (TYR-CQDs) for tyrosinase (TYR) activity detection by one-step hydrothermal protocol utilizing catechol, citric acid and urea as precursors. The prepared TYR-CQDs illustrated excellent linear relationship and broad linear range with a low detection limit, which exhibited high accuracy and recovery in quantitative determination of TYR in human serum samples. Furthermore, the TYR-CQDs had successfully realized intracellular TYR detection owing to excellent biocompatibility, high anti-interference ability and good cellular imaging capability, suggesting the potential biomedical applications in early diagnosis of melanoma and other tyrosinase-related diseases. [ABSTRACT FROM AUTHOR]

A simple multifunctional Schiff base fluorescence probe (E)-N′-(2,4-dihydroxybenzylidene)-2-hydroxybenzohydrazide (NDH) was designed and synthesized by the reaction of 2,4-dihydroxybenzaldehyde and salicylhydrazide. NDH acts as a "off–on" logic gate fluorescence probe for Al3+, Zn2+ and La3+ ions, providing different colors and detection limits of 1.22 μM, 2.47 μM and 2.94 μM, respectively. Moreover, the binding stoichiometry of NDH to Zn2+ was 2:1, but to other metal ions was 1:1, and was confirmed by Job' plot, 1H NMR and ESI–MS. Furthermore, the probe NDH was applied to detect Al3+, Zn2+ and La3+ ions in real water samples and Hela cells. This work might provide a new evidence that the fluorescent probe with "off–on" logic gate can serve as an economical and efficient strategy for simultaneous sensing multiple metal ions. A novel, highly sensitive and selective fluorescent probe was developed to trace Al3+, Zn2+ and La3+ in real water samples and live cells. [ABSTRACT FROM AUTHOR]

The structure, thermal analysis, optical properties, and emission mechanism of fluorescent carbon dots (CDs) have been improved as a result of a vast quantity of new study. Unlike quantum confinement outcomes in quantum dots, CDs usually suffer from intricate optical characteristics coming from a variety of raw materials and synthesis processes based on thermal treatment. The thermal-treatment-based synthesis of CDs and their application in bioenergy systems are discussed in this review. Heating rate, gas atmosphere, and heating regime are among the parameters used in the thermal study of carbon nanomaterials, allowing researchers to investigate the necessary characteristics for applications such as biomass production, photo-catalysis, biodiesel, optoelectronics, and photo-thermal energy conversion. In general, this review proposes CDs as a unified definition of reported carbon nanomaterials, summarises the thermal properties of CDs derived from the formation process, optical properties, and redox characteristics of CDs, and illustrates energy conversion applications, as well as the related mechanistic framework and relationships. The thermal analysis CDs' unique properties may bring up new opportunities and difficulties in a variety of fields. This review also covers energy conversion applications, including the framework and linkages of the mechanisms involved. It is thought that the use of CDs constitutes an advance in the core capabilities of thermal analysis and may provide new perspectives and difficulties in a broader range of applications. [ABSTRACT FROM AUTHOR]

Endogenous sulfur dioxide (SO2), as a gas signal molecule, has a certain physiological functions. Understanding the role of endogenous SO2 in human physiology and pathology is of great significance to the biological characteristics of SO2,which bring challenges to develop fluorescent probes with excellent performance. Herein, we rationally designed and constructed a novel near-infrared bioprobe benzaldehyde-benzopyrylium (BBp) by employing the nucleophilic addition benzopyrylium perchlorate fluorophore and benzaldehyde moiety by means of C = C/C = O group that serves as both fluorescence reporting unit. Probe BBp exhibit excellent sensing performance with fluorescent "On − Off"rapid response (100 s) and long-wavelength emission (670 nm). With the treatment of HSO3−, the color of BBp solution obviously varies from purple to colorless, and the fluorescent color varies from red to colorless. By the fluorescence and colorimetric changes, probe BBp was capable of sensitive determination HSO3− with low limits of detection (LOD) of 0.43 μM, realizing visual quantitative monitoring SO2 derivative levels. Due to the low phototoxicity and good biocompatibility, it was successfully applied to monitor SO2 derivatives and fluorescence imaging in HepG2 and HeLa living cells. Hopefully, this work supplies a new strategy for designing NIR fluorescent probes for quantitative determination SO2 derivatives in biological samples. [ABSTRACT FROM AUTHOR]

A novel fluorescence probe for the detection of Al3+ was developed based on methionine protected gold nanoclusters (Met-AuNCs). A fluorescent Schiff base (an aldimine) is formed between the aldehyde group of salicylaldehyde (SA) and the amino groups of Met on the AuNCs, and developed for selective detection of Al3+ in aqueous solution. Al3+ can strongly bind with the Schiff base ligands, accompanied by the blue-shift and an obvious fluorescence emission enhancement at 455 nm. The limits of detection (LODs) of the probe are 2 pmol L−1 for Al3+. Moreover, the probe can successfully be used in fluorescence imaging of Al3+ in living cells (SHSY5Y cells), suggesting that the simple fluorescent probe has great potential use in biological imaging. [ABSTRACT FROM AUTHOR]

Fluorescent probes are intriguing material for ion detection. In this study, 4,4-difluoro-4-bora3a,4a-diaza-s-indacene (BODIPY) containing a dipicolylethylenediamine unit was developed as a colorimetric and fluorescence "turn-off" probe for Cu2+. The probe exhibited higher selectivity for Cu2+ than other common metal ions with a detection limit of 8.49 μM. With increasing Cu2+ concentration, the probe showed a red-shift in the absorption spectrum as well as fluorescence quenching, possibly due to the intramolecular charge transfer effect of the probe–Cu(II) complex. Furthermore, the probe was used for imaging Cu2+ in living cells based on confocal fluorescence imaging. The results show that the probe is an effective tool for detection copper ions. [ABSTRACT FROM AUTHOR]

In this paper, intrinsic dual-emission fluorescent carbon dots (CDs) doped with N and S atoms have been firstly fabricated. The characterization results show that CDs are successfully synthesized with two separate fluorescence emissions at 468 nm and 628 nm, respectively. The strong and selective interaction of Cr (VI) ions with CDs lead to obvious fluorescence decrease of CDs at 468 nm, which is caused by a mixed quenching mechanism. At the same time, the fluorescence at 628 nm increase. Interestingly, the CDs solution show obvious color change under the daylight and UV light, so visualization detection of Cr (VI) can be realized in water samples. Based on the data of the emission intensity ratios of F468/F628, Cr (VI) can be detected from 3.8 to 38.9 μM combined with the linear correlation coefficient of 0.998, and the lowest detection concentration is 47.2 nM. The platform is satisfactorily applied to the detection of Cr (VI) ions in water samples. In addition, the CDs could be applied as fluorescent probes for cell imaging with dual fluorescent emission. [ABSTRACT FROM AUTHOR]

In this research, DNA-modified carbon dots (CDs) were exploited to construct a fluorescence assay for breast cancer genes (BRCA1, a potential marker for cancer diagnosis) detection. For this purpose, water-soluble synthesized CDs were functionalized with 19 mer-modified oligonucleotides (capture probe). By adding the DNA target, the specific binding between the DNA probe and DNA target causes fluorescence quenching. The assay displayed a fine capability of sensing the BRCA1 gene with a linear range (R2 = 0.9918) of 36 attomolar (aM) to 532 femtomolar (fM) and a detection limit of 2 attomolar. This homogeneous process does not need additional separation and washing steps of un-hybridized DNA. To assess the selectivity, the prepared biosensor responses were evaluated in solutions containing single-base mismatched DNA sequences, three-base mismatched DNA sequences, or non-complementary DNA sequences, separately. To demonstrate the practical application of the designed biosensor, the extracted DNA from blood samples of breast cancer patients was utilized as real samples. When the CDs-DNA bioassay was exploited in the imaging of MCF-7 cancer cells, strong fluorescence emission was observed. After incubation times, both the cells' size and shape remained unchanged. The results validated that the CDs are an extremely great bioimaging candidate in disease diagnosis, biomedicine investigation, and managing cancer diseases. [ABSTRACT FROM AUTHOR]

Sulfhydryl functionalized silicon quantum dots (S-SiQDs) with a fluorescence quantum yield of 38.5% were synthesized using 3-mercaptopropyltrimethoxysilane (MPTMS) and m-phenylenediamine by a simple one-pot method. It is worth noting that by oxidizing the surface sulfhydryl groups and statically quenching, the fluorescence of S-SiQDs at 492 nm (excitation at 383 nm) can be selectively quenched by hypochlorite (ClO-) in a linear range of 0.05 to 1.8 μM with a low detection limit of 13 nM. The reaction was completed in 10 s with no interference from other ROS, metal ions, anions and reducing species. The silicon source containing sulfhydryl groups was used to synthesize silicon quantum dots for the first time, and the surface of the S-SiQDs was provided with sulfhydryl groups and reacted rapidly and sensitively with ClO-. The S-SiQDs have good photostability and biocompatibility, and can be further used for ClO- imaging in MCF-7 cells and zebrafish, showing great promise in biological imaging. The proposed assay demonstrates that 3-mercaptopropyltrimethoxysilane is a good choice to obtain a functionalized fluorescent nanoprobe for redox species. [ABSTRACT FROM AUTHOR]

For ratiometrically imaging peroxynitrite (ONOO−) in living cells, we devised and fabricated a novel fluorescent nanoprobe, NC-NP530/460, in this study. To achieve ratiometric fluorescence response towards ONOO−, NC-NP530/460 used 3-(2-benzothiazolyl) coumarin (Cou-Bz) as the internal reference and 1,8-naphthimide derivative (Naph-PN) as a fluorescent ONOO− probe. These compounds were incorporated into an amphiphilic block polymer called Pluronic F-127. In addition to an ultrafast response to ONOO−, NC-NP530/460 also showed great selectivity and sensitive detection (detection limit was 4.51 μM). It was important to note that NC-NP530/460 demonstrated solid performance for ONOO− fluorescence ratio imaging in living cells, highlighting its potential for ONOO−-related chemical biology research. [ABSTRACT FROM AUTHOR]

A photo-induced electron transfer cationic fluorescence probe L1 based on pyrene-naphthol system was designed to detect the change of Cu2+ with fluorescence. The probe L1 was found to selectively recognize Cu2+ in aqueous ethanol solution [10.0 mmol/L HEPES, pH 7.4, EtOH–H2O = 1:1 (v/v)] without interference from other coexisting metal ions. The response of the sensor to Cu2+ is transient and reversible, and anions generally have no impact on the selectivity of Cu2+. Probe L1 forms complex with Cu2+ in 1:1 ratio as supported by Job's plot analysis. The binding constants of Cu2+ was calculated to be 6.322 × 104 L/mol using a nonlinear curve-fitting method. The detection limit of Cu2+ was determined to be 1.620 × 10–7 mol/L. The energy gap between HOMO and LUMO in L1 and L1–Cu2+ was calculated by density functional theory as 3.76 eV and 2.71 eV, respectively. In addition, the probe L1 has extremely low cytotoxicity and can be used for living cell imaging studies. [ABSTRACT FROM AUTHOR]

The hybrid microgels of carbon dots (CDs) and gold nanoclusters (AuNCs) have been prepared with precipitation polymerization. This hybrid microgels exhibited dual emissions thanks to organic integration of CDs and AuNCs for their unique fluorescence properties maintained in the microgel system. The fluorescence intensity ratio at 570 nm and 450 nm of the dual-emitting has a good linear response to temperature varying at the range of 20–50 °C. In addition, the ratio of the dual emissions intensity of the hybrid microgel shows well linear relationship at pH range between 9.0 and 11.0, which promises to be used as pH sensor. Furthermore, this hybrid microgel is inherently non-cytotoxic, which could be used as high efficient fluorescent probes in living cell with dual colors. Thus, this novel dual-emission hybrid microgel system can be used not only as a multifunctional sensor, but also to expand potential applications in biomedical engineering. [ABSTRACT FROM AUTHOR]

In this work, dual-emissive ratiometric fluorescent system was constructed by the introduction of an ideal internal reference. By virtue of its unique alkalinity, N2H4 could undergo a hydrazinolysis reaction with the ester group of F1, inducing remarkable fluorescence enhancement while the blue fluorescence of the internal reference DPA remained constant. Consequently, the fluorescence intensity ratios (I540/I440) were proportional to the concentrations of N2H4, which was beneficial for the exactly quantitative detection. The skillful strategy granted the sensing system advantages such as relative good solubility in aqueous media, easy-to-design, simple synthesis, large emission shift, good ratiometric response, as well as the successful application in real water samples and cell imaging. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) are a strong alternative to conventional fluorescent probes for cell imaging due to their brightness, photostability, tunable fluorescence emission, low toxicity, inexpensive preparation, and chemical diversity. Improving the targeting efficiency by modulation of the surface functional groups and understanding the mechanisms of targeted imaging are the most challenging issues in cell imaging by CDs. Firstly, we briefly discuss important features of fluorescent CDs for live-cell imaging application in this review. Then, the newest modulated CDs for targeted live-cell imaging of whole-cell, cell organelles, pH, ions, small molecules, and proteins are elaborately discussed, and their challenges in these fields are explained. [ABSTRACT FROM AUTHOR]

The utilization of nanomaterial-based probes in detecting glutathione (GSH) and cell imaging has aroused extensive attention owing to the excellent properties of nanoprobes. Herein, we have synthesized manganese dioxide-S, O co-doped graphitic carbon nitride quantum dots (MnO2-S, O-CNQDs) nanocomposite by in situ synthesis of MnO2 nanosheets in S,O-CNQDs dispersion solution. It was found that GSH could specifically bind to MnO2-S, O-CNQDs so that the fluorescence of S, O-CNQDs could be recovered. As such, a "turn-on" MnO2-S, O-CNQDs nanoprobe can be fabricated and applied to rapidly determine trace amounts of GSH. Under the optimal conditions, MnO2-S, O-CNQDs shows sensitive response to GSH in the range 10–270 μM with a detection limit of 0.307 μM (S/N = 3). The developed MnO2-S, O-CNQDs probe has demonstrated great potential to detection of GSH in biological samples and glutathione injections. What is more, MTT assay indicates that MnO2-S, O-CNQDs has low biotoxicity. The non-fluorescence MnO2-S, O-CNQDs reacts with GSH to recover the fluorescence of S, O-CNQDs in HepG2 cells. Thus, the "turn-on" fluorescence change of MnO2-S, O-CNQDs offers a potentially useful tool to monitor GSH of cancer cells. [ABSTRACT FROM AUTHOR]

A label-free fluorescence sensor based on near-infrared carbon dots (NIR-CDs) and aptamer is described for the highly sensitive and selective detection of ciprofloxacin (CIP). NIR-CDs were synthesized from polyethyleneimine and reduced glutathione by one-step hydrothermal method. The electrostatic interaction between the positively charged carbon dots and the negatively charged aptamer resulted in fluorescence quenching. After the addition of CIP, the specific binding between CIP aptamer and CIP was stronger, resulting in fluorescence recovery. Under the optimal experimental conditions, the recovered fluorescence intensity has a linear relationship with the concentration of CIP in the range 0.5–800 ng/mL, and the detection limit is 0.167 ng/mL. The prepared carbon dots have excellent optical properties and biocompatibility, and due to their emission characteristics in the near-infrared window, they can be used for biological imaging, which has also been confirmed in the experiment. The feasibility of the label-free fluorescence sensor for the detection of CIP is also proved by confocal fluorescence imaging. The detection results of CIP determination in milk by this sensor are satisfactory, indicating that the developed sensor has great application potential. [ABSTRACT FROM AUTHOR]

A fluorescent probe II, 6-azido-2-(2-hydroxyethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione with specific identification environment H2S, was designed and synthesized based on 4-bromine-1,8-naphthalimide and ethanamine. We used 4-bromine-1,8-naphthimide as raw materials to synthesize a new type of reactive fluorescent probe based on the mechanism of intramolecular charge transfer. These two materials are easily obtainable, low in cost, and can be synthesized through a simple two-step reaction. 1,8-Naphthalene anhydride has a moderate fluorescent ability as it introduces an electron-donating group at position 4. A change to its conjugate system can cause a push-pull electronic effect in the molecule and result in a very strong luminous effect. The structure of probe II was characterized by IR, ESI, and NMR. The preliminary screening was under the UV lamp. We found that probe II had a certain specific recognition effect on H2S in the DMSO solvent. After the solvent screening, DMSO was selected as a solvent to identify H2S specifically for the probe. The fluorescence spectroscopy illustrated that probe II showed green fluorescence in the DMSO solution. With the continuous addition of H2S, probe II showed red fluorescence at 510 nm, which produced a strong fluorescence emission peak that stood out from the rest of the spectrum. The experimental results showed that the probe had a very good sensitivity at detecting H2S (with a minimum concentration of 1 × 10–7 mol/L). Meanwhile, dozens of cations and anions do not interfere with the recognition of H2S by the probe molecule in the DMSO system. At the same time, we found that probe II could also recognize H2S by cell imaging technology. [ABSTRACT FROM AUTHOR]

A sensing platform with both ratiometric fluorescence and colorimetric responses towards copper(II) ions (Cu2+) and D-penicillamine (D-pen) was constructed based on carbon dots (CDs). o-Phenylenediamine (OPD) was employed as a chromogenic development reagent for reaction with Cu2+ to generate the oxidation product 2,3-diaminophenazine (oxOPD), which not only emits green fluorescence at 555 nm, but also quenches the blue fluorescence of CDs at 443 nm via the inner filter effect (IFE) and Förster resonance energy transfer (FRET). Additionally, oxOPD exhibits obvious absorption at 420 nm. Since the intense chelation affinity of D-pen to Cu2+ greatly inhibits the oxidation of OPD, the intensity ratio of fluorescence at 443 nm to that at 555 nm (F443/F555) and the absorbance at 420 nm (A420) were conveniently employed as spectral response signals to represent the amount of D-pen introduced into the testing system. This dual-signal sensing platform exhibits excellent selectivity and sensitivity towards both Cu2+ and D-pen, with low detection limits of 0.019 μM and 0.092 μM, respectively. In addition, the low cytotoxicity of the testing reagents involved in the proposed sensing platform facilitates its application for live cell imaging. [ABSTRACT FROM AUTHOR]

In this article, o-carborane has a high boron content, high hydrophobicity, and good chemical stability. It has been widely used in the fields of biology and medicine, especially in the application of boron neutron capture therapy (BNCT). However, o-carborane is a fat-soluble compound, its hydrophobicity is too strong, and its bioavailability is poor. This project aims to improve the water solubility of o-carborane drugs, so that the drugs can reach specific sites. For this reason, this article provides a one-pot reaction for the synthesis of water-soluble boron-containing drugs. 2-Chloro-1-(difluoroboranyl)-5-((4-ethyl-3,5-dimethyl-2H-pyrrol-2-ylidene)(phenyl) methyl)-1H-pyrrole and ethylenediamine are used as raw materials to synthesize fluorescent molecular probe BODIPY-NH2, and the fluorescent molecular probe is reacted with P-CBMA (poly(carboxybetaine methacrylate)) to produce a water-soluble gel polymer. Water-soluble o-carborane polymers were synthesized by hydrogen bonding of the polymers with bis(4-azaspiro[3.4]octan-4-ium)-nido-ortho-carborane and bis(5-azaspiro[4.5]decan-5-ium)-nido-ortho-caborane. The two polymers were characterized and the results showed that the maximum UV absorption wavelength of the two boron polymers in different polar solutions was 530–540 nm. In the fluorescence spectrum, the maximum emission wavelengths of the two boron polymers are concentrated between 550 and 560 nm. Through electron microscopy imaging, the fluoroboron pyrrole polymers wrap the boron clusters to form a spherical stacked. Through fluorescent cell imaging, both boron polymers can enter target cells. [ABSTRACT FROM AUTHOR]

DNA point accumulation for imaging in nanoscale topography (DNA-PAINT) is a powerful super-resolution technique highly suitable for multi-target (multiplexing) bio-imaging. However, multiplexed imaging of cells is still challenging due to the dense and sticky environment inside a cell. Here, we combine fluorescence lifetime imaging microscopy (FLIM) with DNA-PAINT and use the lifetime information as a multiplexing parameter for targets identification. In contrast to Exchange-PAINT, fluorescence lifetime PAINT (FL-PAINT) can image multiple targets simultaneously and does not require any fluid exchange, thus leaving the sample undisturbed and making the use of flow chambers/microfluidic systems unnecessary. We demonstrate the potential of FL-PAINT by simultaneous imaging of up to three targets in a cell using both wide-field FLIM and 3D time-resolved confocal laser scanning microscopy (CLSM). FL-PAINT can be readily combined with other existing techniques of multiplexed imaging and is therefore a perfect candidate for high-throughput multi-target bio-imaging. Oleksiievets et al. combine single-molecule localization super-resolution microscopy technique DNA-PAINT with fluorescence lifetime imaging to allow fast multi-target super-resolution imaging in one spectral region by separating two or three different targets by fluorescence lifetime of the associated dyes. The method is demonstrated on two complementary experimental techniques, a standard confocal laser scanning setup, and a widefield microscope employing a novel TCSPC camera as the detector. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide and biothiol molecules such as Cys and GSH acted important roles in many physiological processes. To simultaneously detect and distinguish them was quite necessary by a suitable fluorescent probe. A novel chemosensor 4-(4-(benzo[d]thiazol-2-yl)-2-methoxyphenoxy)-7-nitrobenzo[c][1,2,5]oxadiazole (BMNO) was designed to detect H2S/Cys/GSH using the combination of nitrobenzofurazan (NBD) and benzothiazole fluorophores linked by a facile ether bond. The probe BMNO was developed for simultaneous identification of H2S, Cys and GSH. Noticeably, the color changes (from colorless to light purple, light orange and light yellow) of probe BMNO solutions for sensing H2S, Cys and GSH could be observed by naked eyes, respectively. The probe BMNO exhibited high selectivity and sensitivity for H2S, Cys and GSH showing distinct optical signal with detection limit as low as 0.15 μM, 0.03 μM and 0.14 μM, respectively. The sensing mechanism was clarified by spectrum analysis and some controlled experiments. In addition, these outstanding properties of probe BMNO enabled its practical applications in detection H2S in beer, and in cell imaging for Cys and GSH as well. [ABSTRACT FROM AUTHOR]

The fabrication of silver nanoclusters with good cellular uptaking behaviors and the property of easy separation and redispersion without aggregation is a thorny problem. In this work, the nanosilica supported silver nanoclusters were prepared by method of situ photochemical reduction of silver precursor on the carboxylated silica nanoparticles. The composite silver nanoclusters showed excellent fluorescent emission properties, good photostability and can be separated from aqueous phase by centrifugation, then can be redispersed in the water environment without affecting its fluorescence emission properties. Further, the vitro cancer cell imaging experiments showed that the composite silver clusters have good cellular uptaking behaviors and excellent biocompatibility. Thus, the composite silver cluster showed good potential application prospects in the field of biomarkers. [ABSTRACT FROM AUTHOR]

In this study, a novel 1,10-phenanthroline skeleton-based fluorescence chemosensor (IPN) was prepared and applied to investigate the metal ions sensing properties. The sensor exhibited an exceptional selective fluorescence response toward Ni2+ combined with the characteristic of high sensitivity, excellent specificity and fast response. The IPN-Ni2+ complex was formed in the ratio of IPN/Ni2+ of 1/2. Introduction of Ni2+ induced the change of fluorescence emission spectra of IPN at 340 nm and 392 nm. Based on Job diagram analysis, frontier molecular orbital calculation and infrared spectrum analysis, the possible mechanism of fluorescence detection Ni2+ was proposed. Moreover, the cell imaging using IPN indicates that IPN is expected to be a useful probe for Ni2+ in broad biological application. [ABSTRACT FROM AUTHOR]

Fluorescence probes that selectively image cadmium are useful for detecting and tracking the amount of Cd2+ in cells and tissues. In this study, we designed and synthesized a novel Cd2+ fluorescence probe based on the pyridine-pyrimidine structure, 4-(methylsulfanyl)-6-(pyridin-2-yl)pyrimidin-2-amine (3), as a low-molecular-weight fluorescence probe for Cd2+. Compound 3 could successfully discriminate between Cd2+ and Zn2+ and exhibited a highly selective turn-on response toward Cd2+ over biologically related metal ions. The dissociation constant (Kd) and the limit of detection (LOD) of 5.4 × 10− 6 mol L− 1 and 4.4 × 10− 7 mol L− 1, respectively, were calculated using fluorescence titration experiments. Studies with closely related analogs showed that the bis-heterocyclic moiety of 3 acted as both a coordination site for Cd2+ and a fluorophore. Further, the methylsulfanyl group of compound 3 is essential for achieving selective and sensitive Cd2+ detection. Fluorescence microscopy studies using living cells revealed that the cell membrane permeability of compound 3 is sufficient to detect intracellular Cd2+. These results indicate that novel bis-heterocyclic molecule 3 has considerable potential as a fluorescence probe for Cd2+ in biological applications. [ABSTRACT FROM AUTHOR]

Zinc ion is closely related to human health. Its content in human body is small, while the effect is large. However, it is not the more the better, must be in a scientific balance. Therefore, it is significant to the rapid detection of Zn2+ in the environment and organism. Herein, a fluorescent probe based on 2-hydroxy-1-naphthalene formaldehyde and furan-2-carbohydrazide was conveniently synthesized via Schiff base reaction. And this probe has been successfully applied to the accurate and quantitative detection of Zn2+ in real samples, showing turn on fluorescence, good selectivity, very low detection limit, real time response and reusability. In addition, this probe has the potential application to trace Zn2+ in living cells with low cytotoxicity. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) are drawing tremendous attention due to their unique photoluminescence property and fascinating functions. Herein, we prepared novel CQDs functionalized with amino acids (AA-CQDs) by a one-pot hydrothermal method for selective detection of Al3+ ions and fluorescence imaging. The prepared AA-CQDs exhibit a novel triple-excitation and single-colour emission for fluorescent property. In addition, the AA-CQDs have a high absolute quantum yield (24.23%) and quantum lifetime (13.29 ns). Moreover, the AA-CQDs exhibit high selectivity and sensitivity for Al3+ by fluorescence enhancement. In pH 7.4 PBS solution, there was a good linear relation between the fluorescence intensity and the concentration of Al3+ in the range of 1–20 μmol L−1; the limit of detection (3σ) was only 0.32 μmol L−1. Furthermore, an AA-CQD probe was also utilized for detection of Al3+ in living cells based on excellent biocompatibility and endocytosis. Based on the concentration of Al3+ ions in cells and apoptosis data, there will be a quick reflect of apoptosis induced by aluminium ions via the fluorescence intensity of the AA-CQD probe. This work will set the stage for developing novel CQD-based biosensors in cell research. [ABSTRACT FROM AUTHOR]

The autoimmune disorders such as rheumatoid, arthritis, and scleroderma are connective tissue diseases (CTD). Autoimmune diseases are generally diagnosed using the antinuclear antibody (ANA) blood test. This test uses indirect immune fluorescence (IIf) image analysis to detect the presence of liquid substance antibodies at intervals the blood, which is responsible for CTDs. Typically human alveolar epithelial cells type 2 (HEp2) are utilized as the substrate for the microscope slides. The various fluorescence antibody patterns on HEp-2 cells permits the differential designation-diagnosis. The segmentation of HEp-2 cells of IIf images is therefore a crucial step in the ANA test. However, not only this task is extremely challenging, but physicians also often have a considerable number of IIf images to examine.In this study, we propose a new methodology for HEp2 segmentation from IIf images by maximum modified quantum entropy. Besides, we have used a new criterion with a flexible representation of the quantum image(FRQI). The proposed methodology determines the optimum threshold based on the quantum entropy measure, by maximizing the measure of class separability for the obtained classes over all the gray levels. We tested the suggested algorithm over all images of the MIVIA HEp 2 image data set.To objectively assess the proposed methodology, segmentation accuracy (SA), Jaccard similarity (JS), the F1-measure,the Matthews correlation coefficient(MCC), and the peak signal-to-noise ratio (PSNR) were used to evaluate performance. We have compared the proposed methodology with quantum entropy, Kapur and Otsu algorithms, respectively.The results show that the proposed algorithm is better than quantum entropy and Kapur methods. In addition, it overcomes the limitations of the Otsu method concerning the images which has positive skew histogram.This study can contribute to create a computer-aided decision (CAD) framework for the diagnosis of immune system diseases [ABSTRACT FROM AUTHOR]

Oxoisoaporphine (OA) is a plant phototoxin isolated from Menispermaceae, however, its weak fluorescence and low water solubility impede it for theranostics. We developed here 4-hydroxyl-oxoisoaporphine (OHOA), which has good singlet oxygen-generating ability (0.06), strong fluorescence (0.72) and improved water solubility. OHOA displays excellent fluorescence for cell imaging and exhibits light-induced cytotoxicity against cancer cell. In vitro model of human cervical carcinoma (HeLa) cell proved that singlet oxygen generated by OHOA triggered photosensitized oxidation reactions and exert toxic effect on tumor cells. The MTT assay using HeLa cells verified the low cytotoxicity of OHOA in the dark and high phototoxicity. Confocal experiment indicates that OHOA mainly distributes in mitochondria and western blotting demonstrated that OHOA induces cell apoptosis via the mitochondrial pathway in the presence of light. Our molecule provides an alternative choice as a theranostic agent against cancer cells which usually are in conflict with each other for most traditional theranostic agents. [ABSTRACT FROM AUTHOR]

Fluorescent probes with outstanding physical and biological properties are superior for functional fluorescent dyes design. However, few studies pay attention to the stability of specific groups in fluorescent probes. The aldehyde group in the fluorescent probe is highly active but unstable under certain conditions. Therefore, we introduced ethoxy groups to realize the conversion to aldehyde groups under acidic conditions and avoid the instability of straightforward aldehyde groups. In this work, two fluorophores based on the multi acetal difluoroboraindacene (BODIPY) units with combination of the pharmaceutical intermediate chalcone have been firstly developed. In the design part, chalcone was introduced as a medium for fluorophore and multiple acetal. The mild synthesis strategy is based on the ligand ((Z)-2-chloro-1-(difluoroboranyl)-5-((4-ethyl-3,5-dimethyl-2H-pyrrol-2-ylidene)(phenyl)methyl)-1H-pyrrole) and connects with chalcone in (2E,2′E)-3,3′-(1,3-phenylene)bis(1-(2,4-bis(2,2-diethoxyethoxy)phenyl)prop-2-en-1-one). The emission wavelengths of the products are around 530 nm with high fluorescence intensity. To highlight the biological characteristics of these novel BODIPY fluorescents, we further demonstrated biological analysis studies on MTT and flow cytometry assays. The IC50 values of BODIPY 5 ranged from 79 ± 6.11 to 63 ± 5.67 μM and BODIPY 6 were found to be 86 ± 4.07 to 58 ± 10.51 μM in tested cell lines. Flow cytometry data analysis shows that the representative agent 6 and reference have similar rational apoptosis rates in first quadrant. Last but not least, 6 shows outstanding biological compatibility and cell imaging potential in live cell imaging and in vivo assay, not only is the fluorescence prominent enough, but also rapidly distributes. Thus, our study reports a mild synthesis strategy and full biological analysis on BODIPY fluorescents, and the subtle modulation of the physical and biological properties by pharmaceutical substituents makes these designed chalcone-BODIPY-based dyes hopeful to realize drug functional fluorescent dyes. Two new highly sensitive BODIPY fluorophores are synthesized based on the ligand ((Z)-2-chloro-1-(difluoroboranyl)-5-((4-ethyl-3,5-dimethyl-2H-pyrrol-2-ylidene)(phenyl)methyl)-1H-pyrrole), which connects with chalcone in (2E,2′E)-3,3′-(1,3/4-phenylene)bis(1-(2,4-bis(2,2-diethoxyethoxy)phenyl)prop-2-en-1-one). Multiple acetals were introduced and the physical and biological properties of BODIPYs are described with MTT assay and in vitro and in vivo imaging. [ABSTRACT FROM AUTHOR]

It is well known that sulfite (SO32−) plays an indispensable role in various physiological processes. Abnormal levels of SO32− can trigger a wide variety of diseases involving respiratory, nervous and cardiovascular systems. Hence, it is necessary to find an efficient approach for detection of SO32−. In this study, a pyrene derivative, (E)-4-(3-oxo-3-(pyren-1-yl)prop-1-en-1-yl)phenyl acrylate (PPA), was designed and synthesized for monitoring SO32−. The probe possessed simple synthetic steps, excellent anti-interference ability and specific response to SO32− in the presence of other substances. The reaction between PPA and SO32− was ascribed to Michael addition and the detection mechanism was confirmed by HRMS spectra analysis and FTIR analysis. Additionally, PPA responded linearly to detect SO32− within the rang of 0–100 μM. The limit of detection was calculated as low as 0.17 μM in accordance with the recommendation of IUPAC (CDL =3sb/m). Notably, PPA was further applied in biological imaging in HepG2 cells, which provided a possibility to monitor SO32− in vivo. [ABSTRACT FROM AUTHOR]

In this work, bright yellow fluorescent and multifunctional carbon dots (N-CDs) were prepared by hydrothermal method from O-phenylenediamine and 4-aminobenzoic acid. The fluorescence characterization showed that the N-CDs possessed good optical properties (QY = 32%) and excitation dependent multi-color emission. By exciting with 390 nm, the strong selective interaction of VB12 with N-CDs could result in a sharp decrease in the luminescence of N-CDs at 567 nm. An efficient fluorescence sensor in aqueous solution was constructed which could linearly respond VB12 in wide concentration ranges of 0–90 μM and 140–250 μM. The linear correlation coefficients of N-CDs and VB12 were 0.9950 and 0.9968, respectively, and the detection limit was 0.119 μM. N-CDs were performed for sensitive determination of VB12 in real samples. Moreover, the N-CDs were exploited to image cell. This N-CDs was a sensitive fluorescence probe to monitor VB12 and presented prospective potential in living cells imaging.Schematic diagram of the synthesis process and application research of N-CDsGraphical abstract: In this work, bright yellow fluorescent and multifunctional carbon dots (N-CDs) were prepared by hydrothermal method from O-phenylenediamine and 4-aminobenzoic acid. The fluorescence characterization showed that the N-CDs possessed good optical properties (QY = 32%) and excitation dependent multi-color emission. By exciting with 390 nm, the strong selective interaction of VB12 with N-CDs could result in a sharp decrease in the luminescence of N-CDs at 567 nm. An efficient fluorescence sensor in aqueous solution was constructed which could linearly respond VB12 in wide concentration ranges of 0–90 μM and 140–250 μM. The linear correlation coefficients of N-CDs and VB12 were 0.9950 and 0.9968, respectively, and the detection limit was 0.119 μM. N-CDs were performed for sensitive determination of VB12 in real samples. Moreover, the N-CDs were exploited to image cell. This N-CDs was a sensitive fluorescence probe to monitor VB12 and presented prospective potential in living cells imaging.Schematic diagram of the synthesis process and application research of N-CDs [ABSTRACT FROM AUTHOR]

By connecting 1,8-naphthalimide and indole sulfonate, a ratio fluorescent probe capable of differential detection of hydrogen sulfite and hypochlorite was synthesized for the first time. It was able to achieve the qualitative detection of HSO3− and ClO− with high sensitivity and selectivity, respectively. It provides a multi-purpose probe and is based on different emission channels without mutual interference. The probe has the advantages of larger Stokes shift (ClO−: 115 nm, HSO3−: 88 nm), longer λem (ClO−: 515 nm, HSO3−: 548 nm) and better water solubility (DMF/PBS = 1:99, v/v). In addition, the probe is a ratio fluorescence probe, which can detect fluorescence intensity with two different emission waves. It provides internal self-calibration, reduces interference from the background and increases detection accuracy. In vitro cytotoxicity and imaging experiments show that the probe can effectively perform the detection of exogenous HSO3− and ClO− in cells. It can also achieve the detection of HSO3− and ClO− in the plasma environment. Because the probe can detect endogenous ClO−, it also has a good prospect for biological application in identifying tumor cells. [ABSTRACT FROM AUTHOR]

Surface enhanced fluorescence (SEF) is observed with very high contrast (100–200) from single E. coli bacteria cells labeled with Carbon nanodots (CDs), on aluminum foil and aluminum film. Likely, it is the first application of organic CDs in SEF. SEF with 633 nm excitation delivered a much higher contrast than SEF with 532 nm excitation. Contrast is the ratio of the fluorescent intensities of labeled CDs to unlabeled (control) cells. High contrast with CDs is also observed on the gold film, silicon, and glass. Enhancement factor (EF) is the ratio of the signal on the metal substrate to the signal on the glass. Single E. coli cells, labeled with commercial graphene quantum dots (GCDs), demonstrated higher EFs (44 on gold, 35 on Al film), but at least one order of magnitude lower contrast (7–10 on aluminum and gold) than cells labeled with organic CDs. Therefore, organic CDs can be a good choice for cell imaging/labeling, capable of achieving a signal to noise (standard deviation of the control) as high as 700 on Al film. Overall, aluminum foil and film are highlighted as inexpensive but efficient substrates for Metal Enhanced Fluorescence, particularly MEF of bacterial cells stained with CDs. [ABSTRACT FROM AUTHOR]

Zinc is essential for growth and development of all living organisms, especially human being. Deficiency of micronutrients like zinc and iron has been linked to the manifestation of hidden hunger. Therefore, it is imperative that development of some rapid screening method for bioavailable zinc in various crops and food commodities would be an essential addition in battle against zinc deficiency related hidden hunger. One such method could be the usage of fluorescence based zinc ion sensing probe which would be robust and convenient for estimating bioavailable zinc. To address this issue, NBD-TPEA, a highly sensitive zinc ion sensing probe, have been used in this study towards the development of a novel fluorescence based approach for the analysis of zinc bioavailability in Caco-2 cells as an in-vitro cellular model. The use of this probe showed dose dependent sensitivity towards increasing concentrations of zinc ion uptake by Caco-2 cells. It also showed specificity for zinc ion uptake as compared to other metal ions in-vitro. These observations correlated extremely well with zinc uptake analysis by cell imaging and conventional analytical technique like, ICP-MS. The developed assay was then tested in mushroom and some selected biofortified derivatives of wheat for determining the levels of their bioavailable zinc using Caco-2 cells. The data as obtained with these food samples in our developed bioassay correlated well with the other sophisticated analytical techniques thus validating our cell based assay. Hence, the developed assay could serve as a simple but sensitive tool for determining bioavailable zinc in various food samples. [ABSTRACT FROM AUTHOR]

In this work, two naphthalene scaffolds dangling around a benzene moiety as a colorimetric and fluorimetric probe for Fe3+ in aqueous media have been reported. Recognition processes of Fe3+ were shown to be scarcely influenced by other coexisting metal ions. The probe exhibits a turn on colorimetric and a turn off fluorimetric detection of Fe3+ ions. The association constant for sensor 1–Fe3+ complex was found as Ka = 1.12 × 105 M–1 with the detection limit of 1.7 nM. The chemosensor has been utilized for bioimaging of E. coli cells. [ABSTRACT FROM AUTHOR]