Application In Cell Imaging Research Articles

Room temperature synthesized metal organic frameworks of Lawsonia inermis: Potential candidates for sensing and cellular imaging

A novel environmentally benign synthesis of Zn and Fe based metal organic frameworks (MOFs) of Lawsonia inermis leaf extract prepared in-house by a simple room temperature extraction technique is presented. BET isotherm and HRTEM analyses revealed mesoporous nature of the newly synthesized MOFs [6.4 nm (Zn-NLw), 3.6 nm (Fe-NLw)]. Their potential for host-guest interaction facilitating sensing applications was demonstrated by selective binding of histidine (His) and tryptophan (Trp) recognized from fluorescence. Addition of His and Trp, induced significant changes in the emission maxima of MOFs (at 470 nm) demonstrating their sensing capacity for these molecules. Host-guest interaction was further investigated by electrochemical studies evidenced as a function of variation in oxidation-reduction peaks. Cytocompatibility of the MOFs were assessed by MTT assay, impact on cellular architecture, degree of cellular uptake while their application in cell imaging was investigated by confocal microscopy analysis. The results suggest excellent biocompatibility of Zn-NLw and Fe-NLw in vitro with significant level of uptake by cells. Fe-NLw exhibited time dependent subcellular localization with distinct luminescence characteristics at a short time period of 30 min as well as at 2 h. These results therefore validate the potential application of Zn-NLw and Fe-NLw in biosensing and fluorescence based bioimaging.

Novel Bis-pyrazoline Fluorescent Probe for Cu2+ and Fe3+ Detection and Application in Cell Imaging.

A fluorescent probe Y((1,1'-([1,1'-biphenyl]-4,4'-diylbis(3-(2-hydroxyphenyl)-4,5-dihydro-1H-pyrazole-5,1-diyl)) bis(ethan-1-one))) was designed and synthesized, which could be used to Cu2+ and Fe3+ sensors. Through the study of optical properties, the probe Y shows good selectivity and sensitivity to Cu2+ and Fe3+ in aqueous tetrahydrofuran solution [10.0mM HEPES, pH 7.4, THF-H2O = 9:1(v/v)] with has excellent anti-interference performance, and its detection limits were 0.931uΜ for Cu2+ and 0.401uΜ for Fe3+. The coordination mechanism of probe Y with Cu2+ and Fe3+ was speculated and verified at DFT level and HRNM. By Hela cytotoxicity and imaging tests, probe Y not only has good biocompatibility, but also can be used for sensing Cu2+ in cells.

Surface Engineering of MoS2 Quantum Dots via Cyclodextrin-Based Host-Guest Chemistry as Versatile Platforms for Enhanced Cell Imaging Application.

Transition metal chalcogenide quantum dots (QDs), especially MoS2 QDs, are an emerging class of novel optical probes for versatile bioanalytical applications owing to their distinct physicochemical properties. However, the reasonable use of these QDs for biological imaging has been largely restricted due to the challenge of controllable surface functionalization. In this work, we report a new strategy to engineer the surface of MoS2 QDs by taking advantage of cyclodextrin (CD)-based host-guest chemistry. The prepared β-CD-modified QDs (β-CD-MoS2 QDs) exhibit enhanced fluorescence properties, excellent biocompatibility, and good stability, making them promising as novel optical probes for bioimaging. Cellular imaging experiments revealed that these β-CD-MoS2 QDs can enter living cells through multiple internalization pathways, which differs significantly from pristine QDs. Particularly, we observed that the intracellular accumulation of MoS2 QDs in lipid droplets was enhanced owing to the specific binding of β-CD to cholesterol, which was then harnessed for monitoring the lipid metabolism in living cells via fluorescence imaging. Furthermore, we also demonstrated the potential use of β-CD-MoS2 QDs for targeted cell imaging and microplate-based cell recognition, which can be easily achieved via bioconjugation with functional motifs (e.g., folate acid) through host-guest chemistry. Altogether, these results illustrate the great potential of engineering the surface of MoS2 QDs and other analogous materials via CD-based host-guest chemistry for advancing their cell imaging applications.

Microencapsulation of Lead-Halide Perovskites in an Oil-in-Fluorine Emulsion for Cell Imaging.

The superior optical properties of lead-halide perovskites (LHPs) inspired significant research in cell imaging applications; many encapsulating processes have improved perovskite stabilities with comparable biosafety. Herein, facile solvent evaporation encapsulation based on an oil-in-fluorine emulsion for aqueous-stable and extremely nontoxic LHP microcapsules is described. Perfluorooctane dispersed the emulsifier fluorocarbon surfactant to form a continuous fluorine phase, while LHPs and polymethylmethacrylate (PMMA) were dispersed in 1,2-dichloroethane, then emulsified in the fluorine phase to form an oil-in-fluorine emulsion. CsPbBr3 microcapsules with a dense PMMA shell that protect fragile CsPbBr3 from the external environment and inhibit lead ion release were obtained after solvent evaporation. The CsPbBr3 microcapsules not only retained 91% of fluorescence intensity after exposure to water for 30 d but also possess extremely low cytotoxicity for MCF-7 cells. After exposure to 2 mg/mL of CsPbBr3 microcapsules for 48 h, the cell viability remained >90%. The intracellular uptake of CsPbBr3 microcapsules indicates its potential use in cell imaging.

Rhodamine B-Quinoline based schiff base as fluorescent ‘turn on’ sensor of Al3+, Cr3+, HSO4− and its cytotoxicity and cell imaging application on TPC-1 and HtH-7 cell lines

A designed Rhodamine-B-quinoline based Schiff base chemosensor (RhBQ) has been synthesized and characterized using various spectroscopic techniques. It shows ‘turn on’ fluorescence emission and also colorimetric sensitivity and selectivity towards trivalent metal ions (Al3+ and Cr3+) and anion (HSO4−) present in aqueous medium. Stoichiometry of both metal (Al3+ & Cr3+) - RhBQ complexes are found to be 1:1 using Job’s plot. A notable enhancement in emission intensity for RhBQ-Al3+ (∼341 fold), RhBQ-Cr3+ (∼292 fold), and RhBQ-HSO4− (∼136 fold) complexes compare to RhBQ are observed. Sensing mechanism i.e. opening of spirolactam ring of RhBQ has been confirmed through various spectroscopic techniques such as; 1H NMR, 13C NMR, ESI-MS, TRPL, FT-IR, and DFT based computational study. The limit of detection (LOD) for Al3+, Cr3+, and HSO4− are found to be 2.2 × 10−8 M, 2.12 × 10−8 M and 8.63 × 10−7 M respectively. An advanced level 3 input OR–INHIBIT logic gate are constructed using chelating ligand EDTA. For onsite detection, TLC paper strip spot of the probe, RhBQ is prepared and the detection of Al3+ in few antacid drug are presented. In addition, cell-imaging analysis of Al3+, Cr3+, and HSO4− ions in the Human papillary thyroid carcinoma cell line (TPC-1) & Human anaplastic thyroid cancer cell lines (HtH-7) are presented and shows promising concentration and time-dependent detection results.

Metal-N-Heterocyclic Carbene Chemistry Directed toward Metallosupramolecular Synthesis and Beyond.

ConspectusAs versatile, modular, and strongly coordinating moieties in organometallic compounds, N-heterocyclic carbenes (NHCs) have led to numerous breakthroughs in transition-metal catalysis, main group chemistry, and organocatalysis. In contrast, the chemistry of NHC-based metallosupramolecular assemblies, in which discrete individual components are held together via metal (M)-CNHC bonds, has been underdeveloped. Integrating NHCs into supramolecular assemblies would endow them with some unforeseen functions. However, one of the most critical challenges is seeking an appropriate combination of the rigid CNHC-M-CNHC units with the resulting topologies and applications. Toward this goal, for the last decade we have focused on the development of M-NHC directed toward metallosupramolecular synthesis. This Account aims to summarize our contributions to the application of M-NHC chemistry toward supramolecular synthesis from structural design to postassembly modification (PAM) and their functional applications since integrating NHCs into supramolecular assemblies has garnered much attention among organometallic, photochemical, and supramolecular researchers. While presenting representative examples of NHC-based architectures, we try to illustrate the purposes and concepts behind the systems developed to aid the rational approach to the design and fabrication of complex assemblies and M-NHC-templated photochemical reactions.We present synthetic approaches for new architectures by the rational design of starting NHC precursors, including the poly-NHC-based mechanically interlocked metallacages and the heteroleptic architectures based on electronic complementary and self-sorting mechanisms. The structural regulation of poly-NHC-based architectures with increasing topological complexity is elaborated on by selective combinations of tetraphenylethylene (TPE) units, NHC backbones, and N-wingtip substituents in a controllable manner.Subsequently, we move to elucidating an M-NHC-templated PAM approach that leads to functional organic cages featuring polyimidazolium/triazolium groups of different shapes and sizes that are difficult to access using alternative organic approaches. These organic cages possess well-defined cavities, and their in situ-generated NHC sites are ideal platforms for stabilizing metal nanoparticles (MNPs) within their cavities for improved catalytic performance.Finally, we demonstrate how to design supramolecular M-NHC templates to synthesize cyclobutane derivatives in homogeneous solutions in a catalytic fashion. Selected examples of M-NHC template-dependent structural transformations and photoreactions are discussed. Their applications in molecular recognition, aggregation-induced emission (AIE), cell imaging, anticancer activity, radical chemistry, and stimuli-responsive materials are also described.Taken together, M-NHC-templated approaches have proven to be powerful methods for constructing diverse architectures with functional applications. The development of this methodology is still in its infancy, with tremendous growth potential and a promising future. We believe that this Account will guide researchers to design fascinating and valuable M-carbene species for diverse applications.

Fabrication of a New Coumarin Based Fluorescent "turn-on" Probe for Distinct and Sequential Recognition of Al3+ and F- Along With Its Application in Live Cell Imaging.

A new coumarin based fluorescent switch PCEH is fabricated which displays high selective sensing towards Al3+ among other metal cations at physiological pH. On gradual addition of Al3+, PCEH shows a brilliant "turn-on" emission enhancement in MeOH/H2O (4/1, v/v) solution. This new fluorescent switch is proven to be a reversible probe by gradual addition of F- into the PCEH-Al3+ solution. Detection limit as well as binding constant values are calculated to be in the order of 10-9M and 104M-1 respectively. We have also explored its potential as a biomarker in the application of live cell imaging using breast cancer cells (MDA-MB-231 cell).

Design of Lysozyme‐Templated Biocompatible Fluorescent Nanocomposites and Their Potential Applications for Cell Imaging, Hydrogen Peroxide Sensing, and Cancer Therapy

AbstractRecently, multifunctional metal‐based nanocomposites gained immense importance in various biomedical applications. Here, a simple approach is reported to synthesize fluorescent bimetallic nanocomposites (NCs) of silver‐gold (Ag@Au NC) and silver‐platinum (Ag@Pt NC) by reducing silver nitrate (AgNO3) on gold nanoparticles and platinum nanoparticles (AuNPs, PtNPs), respectively, in the presence of lysozyme that acts as capping agent. Various in vitro (in normal cells including Chinese hamster ovarian and human umbilical vein endothelial cells) and in vivo (in mouse and chicken egg chorioallantoic membrane model) studies reveal the biocompatibility of these nanocomposites. However, these NCs show inhibition of cancer cell proliferation when treated to various cancer cells (MCF‐7, MDA‐MB‐231, and B16F10), indicating their anticancer property. Intraperitoneal administration of these NCs resulted in the regression of melanoma tumor in C57BL/6J mouse model. Further, these NCs displayed green fluorescence inside MCF‐7 cells facilitating in vitro live‐cell imaging and sense hydrogen peroxide (H2O2) in cellular level (B16F10 and MCF‐7) using their fluorescence enhancement property in presence of H2O2.The results (in vitro and in vivo) altogether demonstrate the promising multifunctional applications of bimetallic nanocomposites (NCs) that can be utilized as promising transformative drugs in cancer theranostics applications.

A novel near-infrared fluorescence probe for hydrogen sulfide detection and application in cell and mice imaging

We presented here a novel near-infrared fluorescent probe based on 2-(2′-hydroxyphenyl)benzothiazole -dicyanoisophorone as fluorophore and 2,4-dinitrobenzenesulfonyl moiety as detection functionalized group for the discrimination of hydrogen sulfide (H2S). Probe L exhibited good specificity and sensitivity “turn on” response at 720 nm with a large Stokes shift (155 nm), rapid response (<60 s) and low detection limit (3.15 × 10−7 M), which also could be identified by the naked eyes. Moreover, probe L was successfully used to image exogenous/endogenous H2S in cells and mice, which demonstrated its potential applications in living systems.

Development of red-luminescent hybrids as contrast agents for cell imaging: A correlation among surface, luminescence, and biological properties

TTA (2-thenoyltrifluoroacetone), DBM (dibenzoylmethane), and EPHEN (5,6-Epoxy-5,6-dihydro- [1,10] phenanthroline) have generated europium complexes with excellent red emission properties. However, for bio applications, these complexes have been grafted on the surface of silica nanoparticles (SNP), by different approaches, due to their low water solubility. Here, we report how three approaches influence the surface, luminescent, and biological properties of 50 and 170 nm-SNP functionalized with carboxylic acid or phenanthroline ligands, useful to anchor TTA and DBM-Eu-complexes. TTA-hybrids exhibited better photophysical properties over the DBM ones, although intermolecular interactions between TTA and silica surface groups are likely to influence their properties. Aiming at such biological application, approach 3 resulted in the luminescent PHEN-hybrids with the highest values of intrinsic (φEuEu) and absolute quantum yields (φEuL), color purity of 100%, and high sensibilization efficiency (η). However, depending on the approach used, different surface charges were observed for the hybrids that directly impacted their cytotoxicity in Huh 7.5 cells. The larger the size of the nanoparticle or the more positive its surface charge is, the lower the toxicity of the hybrid. Even considering the presence of the protein corona effect, estimated in DMEM medium, the initial surface charge, observed in the buffer solution, plays an important role in the nanoparticle-cell interaction. Confocal microscopy images revealed that the hybrids were internalized by cells regardless of their size and surface charge, and their luminescence was also detectable, making them promising candidates for cell imaging applications as luminescent contrast agents.

Comparative study of fluorescence core-shell nanotags with different morphology of gold core

The development of compact and highly active plasmonic nanotags tuned on the first transparency window of biological tissues is under demand for cell imaging applications. The optical activity of bare plasmonic nanoparticles is determined by morphology but the more complex core-shell systems require experimental verification as a shell may change the expected trends. A comparative study of fluorescence core-shell nanotags with different morphology of gold core is presented in this work. Four types of gold nanoparticles (nanostars, nanobones, short and long nanorods), differing in the surface roughness were used for preparation of complex nanotags with a polymer shell containing cyanine 5.5 dye inside and surface functionalized with folic acid as a model delivery vector. The obtained core-shell nanotags were characterized with transmission electron microscopy, UV-Vis absorption spectroscopy and zeta potential measurements. Imaging performance of the obtained nanotags was studied with a fluorescence microscope on human pancreatic cancer cells, indicating a successful internalization of all nanotags by cancer cells and fluorescence intensity depending on the spectral overlap between the dye, plasmonic band of gold core and laser wavelength. The tags based on gold nanorods showed the brightest fluorescence among the studied systems. Scanning electron microscopy of the cells incubated with nanotags proved their internalization in membrane and cytoplasm. The cell viability assay showed reduced cytotoxicity and good biocompatibility up to the concentration enough for cell imaging. The obtained results suggested that compact core-shell nanotags can be used for targeting the folate receptor positive tumor cells.

Multifunctional fluorescent mesoporous carbon nanoprobe for MMP-2-activated cancer cell imaging and targeted photothermal therapy

The integration of cancer imaging with therapy in a simple system is warranted for precise cancer therapy. In this study, carboxyl-functionalized mesoporous carbon nanospheres (MCN) which are efficient photothermal agents and excellent fluorescence quenchers, were used for cancer cell imaging and selective photothermal therapy (PTT) applications. Using MCN, a matrix metalloproteinase-2 (MMP-2)- responsive theranostic nanoprobe was generated by functionalizing an MMP-2-specific fluorescent-labeled PLGVR sequence on the surface of MCN. The nanoprobe not only can be used to detect MMP-2 with a low detection limit of 0.3 pg mL−1, but also can achieve the sensitive intracellular MMP-2 imaging in living cells, validating the differentiation of cancer cells from healthy cells based on the recovered fluorescence intensity. More importantly, selective cancer PTT was achieved using MMP-2-triggered cancer cell imaging. Our in vitro studies showed that by regulating the power density and irradiation time, the nanoprobe can effectively kill cancer cells via PTT. Our strategy opens new avenues for precision medicine, especially phototherapy.

Ratiometric H2S probe that can be recognized by the naked eye and its application in cell imaging

A ratiometric dual-mode probe NI-SH based on 1,8-Naphthalimide was prepared for H2S detection. When treated with H2S, the fluorescence of NI-SH changes from blue (456 nm) to green (540 nm), and displays significant color variation (colorless to yellow) that can visible to the naked eye. Further investigation shows that the NI-SH has high sensitivity, selectivity, and low detection limit at about 0.2 μM, and with large Stokes shift (84 nm). The intermolecular charge transfer (ICT) response mechanism of NI-SH was further studied by analyzing the distributions of the molecular orbital. Besides, NI-SH exhibits a ratiometric fluorescence response in living Hela cells.

Synthesis and surface modification of ultrasmall monodisperse NaYF4:Yb3+/Tm3+ upconversion nanoparticles

The emerging upconversion nanoparticles (UCNP) have gained substantial consideration in the field of bioanalytical as well as diagnostic applications. Therefore, great progress has been made in the synthesis and surface modification of luminescent UCNPs over the last two decades. In this paper, we have reported monodispersed and high luminescent upconversion nanoparticles NaYF4: 20%Yb3+, 2%Tm3+ have been synthesized using a solvothermal method, followed by a coating of the NaYF4 shell with a thin layer of SiO2 on the surface to afford the core-shell NaYF4:Yb3+, Tm3+@SiO2 nanoparticles (NP@SiO2). The prepared nanoparticles were of strong upconversion fluorescent emission intensity, hexagonal phase, and with an average size of about 8 ± 1 nm, which have been characterized by luminescence spectroscopy, powder X-ray diffraction (P-XRD), Dynamic light scattering (DLS), and Transmission electron microscopy (TEM). The results indicate that the NP@SiO2 can be used for the conjugation of fluorescent probes for various biomolecules and can find applications in cancer cell imaging and disease diagnosis.

Pyronin Derivatives as Efficient Electrochemiluminescence Emitters in Aqueous Solution

The electrochemiluminescence (ECL) behavior of pyronin derivatives was reported. We found that these derivatives, as novel ECL emitters, generated an efficient emission phenomenon; that is, they showed anodic emission using tri-propylamine (TPA) as the coreactant and cathodic ECL emission using K2S2O8 as the coreactant. Because of its remarkable luminescent performance, the ECL mechanism (reductive-oxidative and oxidative-reductive) of benzylthiol-substituted pyronin (BTP) was specifically studied. Surprisingly, the cathodic ECL emission of BTP had a lower ECL peak potential at −0.54 V (vs. SCE) in aqueous solution. The potential range of −0.7 V to 0.0 V is lower than that of previously reported K2S2O8 cathodic ECL systems. Its good water solubility, easy modification, and excellent emission properties facilitate appealing (bio)analytical applications in ECL biosensors and cell imaging.

OregonFluor enables quantitative intracellular paired agent imaging to assess drug target availability in live cells and tissues.

Non-destructive fluorophore diffusion across cell membranes to provide an unbiased fluorescence intensity readout is critical for quantitative imaging applications in live cells and tissues. Commercially available small-molecule fluorophores have been engineered for biological compatibility, imparting high water solubility by modifying rhodamine and cyanine dye scaffolds with multiple sulfonate groups. The resulting net negative charge, however, often renders these fluorophores cell-membrane-impermeant. Here we report the design and development of our biologically compatible, water-soluble and cell-membrane-permeable fluorophores, termed OregonFluor (ORFluor). By adapting previously established ratiometric imaging methodology using bio-affinity agents, it is now possible to use small-molecule ORFluor-labelled therapeutic inhibitors to quantitatively visualize their intracellular distribution and protein target-specific binding, providing a chemical toolkit for quantifying drug target availability in live cells and tissues.

A naphthalimide functionalized fluoran with AIE effect for ratiometric sensing Hg2+ and cell imaging application

The pollution caused by mercury ions (Hg2+) poses a potential threat to public health. Therefore, monitoring Hg2+ concentration in the environment is necessary and significant. In this work, a naphthalimide functionalized fluoran dye NAF has been prepared, which shows a new red-shift in emission at 550 nm with the maximum intensity in a mixture of water-CH3CN (v/v = 7/3) due to aggregating induced emission (AIE) effect. Meanwhile, NAF can be employed as a Hg2+ ions sensor, which displays a selective and sensitive response to Hg2+ ions by the reduced fluorescence of naphthalimide fluorophore and increased fluorescence of fluoran group, respectively, showing ratiometric fluorescence signal changes with more than 65-fold emission intensity ratio increase and naked eyes visible color change. In addition, the response time is fast (within 1 min) and the sensing can be conducted in a wide pH range (4.0–9.0). Moreover, the detection limit has been evaluated to be 5.5 nM. The sensing mechanism may be attributed to the formation of a π-extended conjugated system due to the Hg2+ ions-induced conversion of spironolactone to the ring-opened form, partially accompanied by the fluorescence resonance energy transfer (FRET) process. Significantly, NAF exhibits suitable cytotoxicity to living HeLa cells, which allows it to be utilized for ratiometric imaging of Hg2+ ions assisted by confocal fluorescence imaging.

An efficient fluorescence chemosensor for sensing Zn(II) ions and applications in cell imaging and detection of Zn(II) induced aggregation of PrP(106–126) peptide

Zinc is one of the most vital components of the living system and is also involved in promoting various neurodegenerative diseases. Therefore, direct monitoring of Zn2+ in biological systems is essential for human well-being. In this work, a chemosensor probe (HL) based on pyridine was synthesised, characterised, and reported for its highly efficient recognition of the zinc ions. The chemosensing behaviour of HL was determined by fluorescence spectroscopy. The probe was extremely sensitive for Zn2+, with an intensity enhancement of over 80-fold and a low detection limit (LOD) of 4 × 10-10 M (0.4 nM), which is remarkably low. In the presence of Co2+, Cr3+, and Cu2+ metal ions, HL shows fluorescence quenching, probably due to their paramagnetic nature. This chemosensor probe was used for applications in cell imaging and sensing of the Zn2+-induced prion (PrP106-126) peptide aggregation.

Highly selective chemosensor for the sensitive detection of Hg2+ in aqueous media and its cell imaging application

The deleterious toxicity of Hg2+ on ecological and biological system makes it crucial for the precise monitoring of Hg2+. Herein, we prepared a novel “turn-on” chemosensor N’-(4-(methylthio)butan-2-ylidene) rhodamine B hydrazide (denoted as MTRH) by a simple two-step reaction. MTRH exhibited an ultra-low detection limit (LOD) in fluorescence measurement of Hg2+ in pure aqueous media, which was estimated to be 1.3 × 10-9 mol·L-1. Moreover, the proposed chemosensor holds the ability of visualizing Hg2+ by the distinct color change of the solution. The corresponding recognition mechanism was investigated by Job’s plots, mass spectrometry and DFT calculation analysis. Importantly, the characteristics such as high sensitivity, low cytotoxicity and good biocompatibility of MTRH exhibited in the application of detecting Hg2+ in real water sample and bioimaging of intracellular Hg2+ prove that MTRH is a promising tool to evaluate the levels of Hg2+ in complex biological systems.

An optical chemosensor for nano-level determination of Pb2+ and Cu2+ in aqueous media and its application in cell imaging

An optical chemosensor for nano-level determination of Pb2+ and Cu2+ in aqueous media and its application in cell imaging