Multicolor Cellular Imaging Research Articles

Construction of Red Fluorescent Dual Targeting Mechanically Interlocked Molecules for Live Cancer Cell Specific Lysosomal Staining and Multicolor Cellular Imaging.

We have designed and synthesized red fluorescent mechanically interlocked molecules with dual targeting functionality for live cancer cell specific active targeting followed by selective internalization and imaging of malignant lysosomes along with real-time tracking, 3D, and multicolor cellular imaging applications.

Molecularly Precise, Bright, Photostable, and Biocompatible Cyanine Nanodots as Alternatives to Quantum Dots for Biomedical Applications

Fluorescent imaging with fluorophores has become a powerful way to explore complex biological systems and visualize nanoparticles for drug delivery. However, it is challenging to develop fluorophores with ideal physical and optical properties. We report a method to synthesize cyanine nanodots with a single-molecule structure, well-defined particle size, customizable fluorescent spectrum, and bright and stable fluorescence. These cyanine nanodots are acquired by the divergent synthesis of cyanine-dye-cored polylysine (PLL) dendrimers. We demonstrated the feasibility of the method by synthesizing cyanine 3 (Cy3), cyanine 5 (Cy5), or cyanine 7 (Cy7) cored single-molecule nanodots up to eight generations with a size of around 11 nm. We show that these cyanine nanodots are capable of multiple biomedical applications, including multicolor cellular tracing and cancer imaging. These cyanine nanodots possess many merits of organic dots and quantum dots that are promising for future application.

Molecularly Precise, Bright, Photostable, and Biocompatible Cyanine Nanodots as Alternatives to Quantum Dots for Biomedical Applications.

Fluorescent imaging with fluorophores has become a powerful way to explore complex biological systems and visualize nanoparticles for drug delivery. However, it is challenging to develop fluorophores with ideal physical and optical properties. We report a method to synthesize cyanine nanodots with a single-molecule structure, well-defined particle size, customizable fluorescent spectrum, and bright and stable fluorescence. These cyanine nanodots are acquired by the divergent synthesis of cyanine-dye-cored polylysine (PLL) dendrimers. We demonstrated the feasibility of the method by synthesizing cyanine 3 (Cy3), cyanine 5 (Cy5), or cyanine 7 (Cy7) cored single-molecule nanodots up to eight generations with a size of around 11 nm. We show that these cyanine nanodots are capable of multiple biomedical applications, including multicolor cellular tracing and cancer imaging. These cyanine nanodots possess many merits of organic dots and quantum dots that are promising for future application.

A photoactivatable theranostic probe for simultaneous oxidative stress-triggered multi-color cellular imaging and photodynamic therapy

Simultaneous in situ monitoring critical organelles upon oxidative stress and implementing therapeutics utilizing oxidative stress are of vital importance and remain challenging task. Herein, we rationally design and facilely synthesized a photoactivatable fluorescent probe bearing 1,4-dihydropyridine moiety with aggregation-induced emission (AIE) tendency, namely TPA-DHPy, which can rapidly transform into its pyridine counterpart TPA-Py via photo-oxidative dehydrogenation showing strong polarity sensitivity and largely red-shifted emission. TPA-DHPy- and TPA-Py-based type I/type II photosensitization is able to effectively generate reactive oxygen species to induce in situ oxidative stress under white light irradiation. TPA-DHPy can be taken up by cancer cells, and gradually light up lipid droplets (LDs) and endoplasmic reticulum (ER) during photoactivatable process, as well as in situ monitoring difference and alteration of their microenvironment upon oxidative stress by means of multi-color fluorescence imaging in lambda mode. Furthermore, the in situ generated TPA-Py is capable of further destroying the functions of LDs and ER with prolonging the irradiation time, and remarkably inhibiting tumor growth under white light irradiation by the way of photodynamic therapy. This study thus offers useful insights into designing a new generation of theranostic agents towards imaging-guided precise cancer therapy.

Wet chemistry-based processing of tunable polychromatic carbon quantum dots for multicolor bioimaging and enhanced NIR-triggered photothermal bactericidal efficacy

A strategy for the processing of photoluminescence emission tunable multicolor carbon quantum dots has been adopted based on the controllable acidic strength [different ratio mixtures of sulfuric and phosphoric acids (S:P)] using a single polyphenolic precursor. 1,3,5-trihydroxybenzene, a three-fold symmetric (C3h symmetry) triangulogen bearing –OH group at the meta position, was judiciously chosen to undergo dehydration facilitated condensation and carbonization suitably via a tri-molecular reaction route in a dehydrating acid medium. Polyaromatic-polyphenolic CQDs with multicolor emissions [blue (B-CQDs), green (G-CQDs), and yellow (Y-CQDs)] could be rapidly obtained through a facile wet chemistry-based thermal heating process. The mechanism of regulated bottom-up growth of CQD particles involved tri-molecular ring cyclization. These multicolor luminous CQD probes enabled intense multicolor cellular imaging throughout the entire visible range because of their good biocompatibility, photostability, and effective intracellular distribution. Moreover, Y-CQDs with larger polyaromatic sp2 domains and higher oxidized surfaces exhibited a high photothermal conversion efficiency (PCE ∼ 32.6 ± 1 %) and thus exhibited remarkable NIR-light responsive photothermal bactericidal activity. Our results demonstrate that hyperthermia-induced bactericidal activity is due to the elevated reactive oxygen species (ROS) amplification and membrane damage of Bacillus subtilis. This study provides a potential alternative for the multicolor imaging guided CQDs-based phototheranostic.

Carbon dots for multicolor cell imaging and ultra-sensitive detection of multiple ions in living cells: One Stone for multiple Birds

Given the significant impact of ions on environment pollution and human health, it is urgently needed to establish effective and convenient ion detection approaches, particularly in living cells. In this paper, we constructed multicolor N-doped-carbon dots (mPD-CDs) by facile one-step hydrothermal carbonization of m-phenylenediamine (mPD). mPD-CDs were successfully deployed for multicolor cellular imaging for animal cells, fungi, and bacteria in a wash-free way with high photostability and satisfactory biocompability. Moreover, mPD-CDs can be used as a fluorescent sensing probe for ultrasensitive detection of both iodide ion (I−) and typical heavy metals such as cadmium (Cd2+), copper (Cu2+), mercury (Hg2+), gadolinium (Gd3+), ferrous ion (Fe2+), Zinc (Zn2+), and ferric ion (Fe3+). This is the first report using CDs as optical sensing probe for the detection of Gd3+, and for detection of Fe3+ with fluorescence “turn on”. More significantly, with these versatile and fascinating properties, we applied mPD-CDs for intracellular ion detection in living cells like Hep G2 and S. cerevisiae, and zebra fish. Altogether, mPD-CDs displayed great potential for multicolor cell imaging and the multiple ion detection in vitro and in vivo, presenting a promising strategy for in-situ ultrasensitive sensing of multiple metal ions in the environment and the biological systems.

One-step synthesis of nitrogen-doped multi-emission carbon dots and their fluorescent sensing in HClO and cellular imaging.

Tunable multicolor carbon dots (CDs) with a quantum yield reach up to 35% were generated directly from rhodamine and urea via one-step hydrothermal approach and purified through silica gel column chromatography. Transmission electron microscopy images reveal that the as-prepared CDs possess a small size distribution below 10nm with bright blue, green, and yellow color emission, designated as b-CDs, g-CDs, and y-CDs, respectively. The in-depth investigations reveal that the multicolor emission CDs with different fraction displays fluorescence emission wavelength ranges from 398nm (b-CDs), 525nm (g-CDs), to 553nm (y-CDs) which could be well modulated by controlling the amount of heteroatom nitrogen especially amino nitrogen onto their surface structures. Further experiments verify the important role of nitrogen content by using rhodamine solely or substituting urea with sulfur containing compounds as precursors to produce corresponding CDs since the performance is lower than that of urea incorporation. Theoretical calculation results also reveal that the increasing amount of amino nitrogen into their surface structures of b-CDs, g-CDs to y-CDs is responsible for reduced band gaps energy, which result in the redshifted wavelength. Benefiting from the excellent photoluminescence properties, wide pH variation range, high photo stability, and low toxicity, these CDs were employed for HClO sensing at 553nm within the range 5 to 140μM with a limit of detection (LOD) of 0.27 ± 0.025μM (n = 3) and multicolor cellular imaging in HeLa cells. Tunable multicolor carbon dots (CDs) were generated directly from rhodamine and urea via one-step hydrothermal approach and purified through silica gel column chromatography. The as-prepared CDs exhibit bright blue, green, and yellow color emission which could be well modulated by controlling the increasing incorporation of heteroatom nitrogen especially amino nitrogen into their surface structures. These CDs were employed for HClO sensing and demonstrated to multicolor cellular imaging in HeLa cells.

Rapid and Green Fabrication of Carbon Dots for Cellular Imaging and Anti-Counterfeiting Applications

Carbon dots (CDs) with plenty of favorable properties have been extensively investigated in diverse areas including bioimaging, biomedicine, sensor, energy storage, anti-counterfeiting, photocatalysis, and optoelectronic devices. Herein, a simple, rapid, and green sonochemical-assisted method for fabricating nitrogen-doped CDs has been developed. In this approach, the nitrogen-doped CDs can be obtained through irradiation by intensive ultrasonic waves from ultrasonic probes in 30 min. The achieved CDs exhibit excellent water dispersibility, which can be ascribed to their high functionalization. Importantly, the CDs also demonstrate remarkable fluorescent properties, high photostability, and low cytotoxicity, which can be utilized for multicolor cellular imaging and anti-counterfeiting applications. As far as we know, the sonochemical-assisted method for rapidly synthesizing nitrogen-doped CDs from gelatin has never been reported before. Significantly, the sonochemical-assisted approach to rapidly fabricate CDs is versatile for the facile construction of fluorescent CDs, and the obtained CDs can be potentially used in various areas including bioimaging and anti-counterfeiting.

Single-step synthesis of N-doped carbon dots and applied for dopamine sensing, in vitro multicolor cellular imaging as well as fluorescent ink

A water-soluble, simple, and facile nitrogen-doped carbon dots (N-CDs) were developed by a single-step via the pyrolysis process and utilized in the fluorometric detection of dopamine (DA). DA is a neurotransmitter and plays a vital role in regulating several biological activities in mammalians. DA can oxidize into DA-quinone by the addition of N-CDs. The emission intensity of N-CDs can be quenched by DA through the inner filter effect (IFE) procedure. This detection mechanism is characterized by UV–vis spectroscopy and fluorescence lifetime decay study. The synthesized N-CDs are highly selective and sensitive towards DA, and their detection limit is 0.2 nM with a linear range of 0.001−1 μM. More importantly, N-CDs are utilizing to detect DA in the human blood serum. The as-synthesized N-CDs have excellent optical properties and are potentially used as a staining material for multicolor cellular imaging of MDA-MB 468 human breast cancer cells. Moreover, N-CDs are also used as a fluorescent ink and can be used for information storage. Hence, the as-synthesized N-CDs are explored as fluorescence materials for DA sensing, multicolor cellular imaging, and fluorescent ink.

Rapid fabrication of carbon dots from babul seed powder as green precursor: Antioxidant activity and multicolor imaging

Abstract Carbon dots (CDs) are versatile nanomaterials with high biocompatibility and attractive optical properties. This research presents a microwave assisted rapid inexpensive method of CDs production using babul seed powder as a novel green source. Various parameters of synthesis were optimized and as obtained CDs were characterized by Transmission electronic microscopy (TEM), X-ray diffraction (XRD), UV–Visible, fluorescence, Fourier-transform infrared (FT-IR), Raman and X-ray photoelectron spectroscopic (XPS) techniques. CDs exhibited excellent water solubility and excitation dependent emission that is stable to pH, ionic strength and resistant to photo bleaching. Furthermore, the cytotoxicity of CDs tested on both normal (Human embryonic kidney HEK-293) and cancerous (Human breast adenocarcinoma MCF-7) cell lines disclosed their high biocompatibility. With these admirable properties, CDs were applied as multicolor cellular imaging agents. Furthermore the antioxidant activity of CDs was investigated by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay.

One-pot fabrication of dual-emission and single-emission biomass carbon dots for Cu2+ and tetracycline sensing and multicolor cellular imaging.

Dual-emission and single-emission carbon dots (DCDs and SCDs) have been simultaneously synthesized by one-pot solvothermal treatment of leek. Different graphitization and surface functionalization were responsible for their distinction in fluorescence characteristics. DCDs with an average size of 5.6nm exhibited two emissions at 489 and 676nm under 420-nm excitation. Complexation between DCDs' surface porphyrins and Cu2+ led to quenching of the 676-nm emission, which resulted in the ratiometric determination of Cu2+ with a limit of detection (LOD) of 0.085μM. SCDs, containing additional sulfur element (0.50%) with an average size of 7.7nm, presented a single emission at 440nm under 365-nm excitation. The static quenching and inner filter effects between SCDs and tetracyclines (TCs) made SCDs a fluorescence nanoprobe for TCs' determination with LODs of 0.26-0.48μM. Applications of DCDs and SCDs for respective determination of Cu2+ and TCs in milk and pig liver samples were successfully demonstrated. Moreover, good photostability, low toxicity, and outstanding biocompatibility made DCDs and SCDs suitable for multicolor cellular imaging. Results indicate that natural products are excellent raw materials to controllably synthesize CDs with prominent physicochemical and fluorescence properties.Graphical abstract.

Room temperature manufacturing photoluminescent graphene quantum dots based on MXene

Carbide–derived graphene quantum dot (GQDs) have high potential to the photoluminescent field owing to its non-toxicity, strong light harvesting capability and large surface area. In order to cost-effectively and stably produce GQDs, lowering synthesis temperature of GQDs is one of the great candidates, but it has been still a big challenge. Herein, the photoluminescent GQDs were obtained by KOH (aq) of MXene at room temperature controlling the reaction time and concentration. This facile and cost-effective method can produce GQDs/TiO2 nanoparticles which had the average particle size about 1.5 nm with minor portion of amorphous carbon. The functionalized and defects in GQDs/TiO2 crystalline nanoparticles were characterized according to fabricating conditions and photoluminescent properties were precisely detected. Although the quantum yield of fabricated GQDs/TiO2 nanoparticles is 2.06%, it could be improved by optimizing the conditions of KOH activation. It was the meaningful result using facile synthesis for GQDs/TiO2 nanoparticles at room temperature and it could encompass key factor to manufacturing quantum dots. The technique can be considered general enough to expand to various research fields such as information security, display, biocompatible multicolor cellular imaging and sensors.

Hydrothermal synthesis of green fluorescent nitrogen doped carbon dots for the detection of nitrite and multicolor cellular imaging

A fluorescent probe for the determination of nitrite (NO2−) was fabricated by using green fluorescent nitrogen doped carbon dots (NCDs). The NCDs were synthesized via a one-pot hydrothermal carbonization of citric acid in the presence of p-phenylenediamine as the nitrogen source. The N content of the NCDs was high to 17.09% and consisted of a variety of functional groups on the NCDs surface, including sp2-hybridized CN, porphyrin C–N–C and amino N in N-(C) 3 or H–N-(C) 2 et al. N atoms were also doped within the framework of the NCDs. The almost monodisperse NCDs (average particle diameter = 3.67 nm) exhibited green photoluminescence (PL) with excitation/emission maxima of 360/505 nm. The PL of the NCDs was dependent on both excitation wavelength and solution pH. The NCDs showed a strong PL quenching response to NO2− under acidic conditions (pH = 2.5). The PL intensity of the NCDs was inversely proportional to the concentration of NO2− between 0.02 and 40 μM (R2 = 0.992), with a detection limit of 21.2 nM. The practical use of the nanoprobe for NO2− determination in food samples was also demonstrated, successfully. NCD-nitroso compounds formed because of reaction between the abundant amide groups on the surface of NCDs with the NO2−, which caused an inner filter effect and static PL quenching. Importantly, the NCDs had low cellular toxicity and were successfully used as a multicolor cellular imaging agent for Hepg2 cells.

Unprecedented Multicolor Photoluminescence from Hyperbranched Poly(amino ester)s.

A novel kind of water-soluble fluorescent hyperbranched poly(amino ester) (PAE) is prepared through a one-pot polycondensation reaction of citric acid (CA) and N-methyldiethanolamine (NMDEA). The PAE exhibits enhanced and red-shift fluorescence with increasing solution concentration, showing distinct aggregation-induced emission character. Interestingly, the resulting PAE exhibits tunable photoluminescence from blue, cyan, and green to red irradiated by altering the excitation wavelengths. Such unique emission of non-conjugated PAE is attributed to the clustering of ester and tertiary amine groups derived from PAE self-assembly aggregates. Moreover, the fluorescence of PAE is very sensitive to Fe3+ ions. The facile preparation and unique optical features make PAE potentially useful in numerous applications such as multicolor cellular imaging, Fe3+ ions probe, and light-emitting diodes.

Orange, yellow and blue luminescent carbon dots controlled by surface state for multicolor cellular imaging, light emission and illumination.

Three kinds of carbon dots (CDs) with different photoluminescence (PL) (blue, yellow or orange) were synthesized by microwave heating. They display wavelength-independent excitation wavelengths (in the range from 444 to 574nm), similar average particle size (from 3.7 to 4.2nm), and fluorescence lifetimes (from 2.7 to 3.1ns). Color and quantum yields (from 8 to 45% in ethanol) are related to the oxidation degree and the number of N-functional groups on their surface. The CDs are shown to be viable nanoprobes for multicolor imaging of cells. Three composite phosphors were obtained by coating the various CDs on starch particle. The resulting nanomaterials emit solid-state fluorescence with a quantum yield of ≥16%. They were used to fabricate luminescent blocks and light-emitting diodes with controllable color temperature. Graphical abstract (a) The synthesis process of the three carbon dots (CDs). The application in cell imaging (b), starch/CD phosphors (c), starch/CD phosphors-based luminescent blocks (d) and light-emitting diodes (e). (λex: excitation wavelength).

Real time monitoring and quantification of uptake carbon nanodots in eukaryotic cells.

The real time monitoring and quantification of the concentration of highly fluorescent nitrogen-doped carbon nanodots (C-dots) in eukaryotic Tobacco bright yellow-2 (BY-2) plant cells was investigated by fluorescence and confocal microscopy. The quantitative measurement of their fluorescent emission intensity was possible because of the high photo-resistance, good water solubility and the absence of fading effect of the nanoparticles, which is frequent occurred problem of the conventional organic dyes. The microscopic analysis revealed that C-dots entered generally into the cells through endocytosis and caused negligible cytotoxicity. The multicolor cellular imaging of labeled Tobacco BY-2 demonstrates that the cells were in good health conditions and any blinking artifacts were not observed. The quantification of fluorescence emission intensity was carried out in the intracellular regions where the relationship between the C-dots concentration and relative emission was linear. Based on a control experiment with fluorescence liposomes with known dependence between C-dots concentration and emission, we were able to determine the amount of accumulated nanoparticles in the inner compartments of the eukaryotic cell through subsequent digital image analysis. The reported microscopic approach may be used for accurate testing and direct examination of the drug internalization mechanisms by C-dots as sensitive probes in single cells or tissues.

Hydrothermal synthesis of nitrogen and boron co-doped carbon quantum dots for application in acetone and dopamine sensors and multicolor cellular imaging

Nitrogen and boron co-doped carbon quantum dots (NB-CQDs) were prepared via one-pot hydrothermal treatment of citric acid, borax, and p-phenylenediamine.The synthesized NB-CQDs were characterized by transmission electron microscopy, Fourier-transform infrared spectra, X-ray photoelectron spectra, dynamic light scattering, ultraviolet-visible absorption and fluorescence spectra to characterize their surface morphology, crystal structure, functional groups and elemental composition, and optical properties. It was found that N and B species were efficiently doped into the carbon framework of the dots, the N- and B-Containing groups formed on the surface of NB-CQDs during the hydrothermal reaction. The element doping and surface functionalization of NB-CQDs efficiently modulated their physicochemical properties. The NB-CQDs were nearly mono-disperse with an average particle diameter of 3.53 nm, and the excitation/emission wavelengths were 360/490 nm, respectively. The NB-CQDs showed regular photoluminescence (PL) emission under different excitation wavelengths, and possessed pH-dependent and solvent polarity-dependent PL properties. In addition, the NB-CQDs and a NB-CQD/poly(vinyl alcohol) composite film showed good PL responses to acetone solution and vapor. A PL sensor for the determination of acetone solution with a limit of detection (LOD) of 0.54 μM (R2 = 0.9956) was then designed. The NB-CQDs were also used for the determination of dopamine. The PL intensity of the NB-CQDs was inversely proportional to the concentration of dopamine in the range of 0.1–70 μM (R2 = 0.9958). The LOD of dopamine was 11 nM, and PL quenching occurred via a static quenching mechanism. Additionally, these NB-CQDs can be used for multicolor cellular imaging and showed good uptake by Hepg2 cells.

Synthesis and characterization of biocompatible carbon-gold (C-Au) nanocomposites and their biomedical applications as an optical sensor for creatinine detection and cellular imaging

Highlights • This study demonstrates the synthesis of photoluminescent C-Au nanocomposites (C-Au NC) for multi-color cellular imaging in replacement of high priced fluorescence molecules and synthetic dyes. • The synthesized C-Au NC can be used to detect both normal and abnormal levels of creatinine. • The reducing and capping capabilities of Citrullus lanatus derived carbon nano dots (CNDs) for C-Au NC synthesis were investigated. • C-Au NC showed excellent biocompatibility against cancer and normal cell lines which can be used for biomedical applications.

MnO nanoparticles with unique excitation-dependent fluorescence for multicolor cellular imaging and MR imaging of brain glioma.

The authors describe MnO nanoparticles (NPs) with unique excitation-dependent fluorescence across the entire visible spectrum. These NPs are shown to be efficient optical nanoprobe for multicolor cellular imaging. Synthesis of the NPs is accomplished by a thermal decomposition method. The MnO NPs exhibit a high r1 relaxivity of 4.68mM-1s-1 and therefore give an enhanced contrast effect in magnetic resonance (MR) studies of brain glioma. The cytotoxicity assay, hemolysis analysis, and hematoxylin and eosin (H&E) staining tests verify that the MnO NPs are biocompatible. In the authors' perception, the simultaneous attributes of multicolor fluorescence and excellent MR functionality make this material a promising dual-modal nanoprobe for use in bio-imaging. Graphical abstract A direct method to synthesize fluorescent MnO NPs is reported. The NPs are biocompatible and have been successfully applied for multicolor cellular imaging and MR detection of brain glioma.

Low-temperature rapid synthesis of nitrogen and phosphorus dual-doped carbon dots for multicolor cellular imaging and hemoglobin probing in human blood

Heteroatom doping of carbon dots (CDs) can efficiently tune the structure of electronic energy levels and modulate the photochemical properties of CDs. However, the reported synthesis routes of heteroatom-doped CDs are complicated and rigorous. Herein, a simple and rapid low-temperature heating strategy was applied to synthesize fluorescent nitrogen and phosphorus dual-doped CDs (N,P-CDs) using sucrose as carbon source, and 1,2-ethylenediamine (EDA) and phosphoric acid as dopants, respectively. These N,P-CDs exhibit excellent fluorescent stability over wide pH range solutions (4–11), ultrahigh ion strength (3 M KCl), and longtime UV light irradiation (3 h continuously), which makes these N,P-QDs promising good candidates for fluorescent probes. These N,P-CDs showed excellent biocompatibility, multicolor cellular imaging, and non-cytotoxicity to human hepatocellular carcinoma HepG2 cells even at 500 μg/mL levels for 48 h incubation. These N,P-CDs exhibited a strong blue emission and a sensitive response to hemoglobin. The N,P-CDs based fluorescent probe was then applied to sensitively determine hemoglobin with a detection limit of 0.29 nM. Notably, it was also applied for label-free detection of hemoglobin in human urine samples and human blood samples, which indicated its potential applications in clinical diagnosis and other biologically related study.