Cell Imaging Studies Research Articles

Exploration of varying coordination reactivity of Schiff base H3L toward CdII, ZnII and MgII: Hydroxido-bridged dimer, acetato-directed chain and live cell-imaging

In the present work, a discrete dinuclear cadmium(II) complex Cd2(μ−H2L)(μ−OH)Cl2⋅H2O (1) and a dinuclear zinc(II) based 1D chain complex ({Zn2(L')(O2CCH3)}ClO4⋅3H2O)n (2) (where H3L = 2,6-bis{2-(2-hydroxyethylamino)ethylimino}methyl-4-methylphenol and H2L′ = bis-oxazoline (BOX) ligand), have been synthesized and characterized by single-crystal X-ray crystallography. The Cd2+ ions in the first case showed straight cut incorporation of metal ions within the ligand pockets. In case of zinc(II), the coordination induced oxazolidine ring formation resulted in macrocyclic ligand formation having two adjacent coordination pockets. In complex 2, the acetate ion acts as an O,O linker and joins the Zn2 nodes bound within the newly formed macrocyclic ligand bearing bis-oxazolidine rings to form 1D polymeric chain at the end. The H3L was next screened for its efficacy as selective fluorescence sensor for Mg2+ ions in aqueous MeOH medium. Steady state absorption and emission behaviour of H3L, 1 and 2 have been investigated. Time resolved fluorescence properties of H3L and the complexes 1 and 2 have been examined, and their lifetimes have been determined in 0.038–0.257 ns range. The cell viability in presence of H3L makes it a suitable candidate for application in live cell imaging studies.

The role of the transcriptional repressor YY1 in immunoregulatory gp96-mediated immune responses

Abstract Heat shock protein (HSP)-mediated immune responses encompass both antigen-specific pro-inflammatory responses as well as non-antigen specific regulatory responses. The type of immune response primed depends on antigen presenting cell engaged by the HSP. Classical dendritic cells (cDCs) and macrophages elicit inflammatory responses in response to immunogenic HSPs such as gp96, whereas plasmacytoid dendritic cells (pDCs) induce regulatory responses. We have previously shown that NRP1 is in part responsible for the difference between these subsets. Gp96 signaling increases NRP1 expression on pDCs but not cDCs. This increased expression drives pDC-Treg interactions and results in activated Tregs. Increased NRP1 expression in pDCs is dependent on DNA methylation and an area of differential methylation has been identified in intron 2 of NRP1. Within this region of intron 2, bisulfite sequencing was used to look for specific sites of methylation. Intron 2 includes 2 CpG sites which show increased methylation in pDCs following stimulation with gp96. In the same region of these CpG sites, there is a consensus sequence for the transcriptional repressor YY1. We are investigating the role of YY1 as an inhibitor of NRP1 transcription, whose binding is blocked by methylation at intron 2. Using ChIP assays, siRNA knockdowns and cell imaging studies we will determine the role of YY1 in gp96-mediated immunoregulatory responses.

Lipid Droplets in Unicellular Photosynthetic Stramenopiles.

The Heterokonta or Stramenopile phylum comprises clades of unicellular photosynthetic species, which are promising for a broad range of biotechnological applications, based on their capacity to capture atmospheric CO2 via photosynthesis and produce biomolecules of interest. These molecules include triacylglycerol (TAG) loaded inside specific cytosolic bodies, called the lipid droplets (LDs). Understanding TAG production and LD biogenesis and function in photosynthetic stramenopiles is therefore essential, and is mostly based on the study of a few emerging models, such as the pennate diatom Phaeodactylum tricornutum and eustigmatophytes, such as Nannochloropsis and Microchloropsis species. The biogenesis of cytosolic LD usually occurs at the level of the endoplasmic reticulum. However, stramenopile cells contain a complex plastid deriving from a secondary endosymbiosis, limited by four membranes, the outermost one being connected to the endomembrane system. Recent cell imaging and proteomic studies suggest that at least some cytosolic LDs might be associated to the surface of the complex plastid, via still uncharacterized contact sites. The carbon length and number of double bonds of the acyl groups contained in the TAG molecules depend on their origin. De novo synthesis produces long-chain saturated or monounsaturated fatty acids (SFA, MUFA), whereas subsequent maturation processes lead to very long-chain polyunsaturated FA (VLC-PUFA). TAG composition in SFA, MUFA, and VLC-PUFA reflects therefore the metabolic context that gave rise to the formation of the LD, either via an early partitioning of carbon following FA de novo synthesis and/or a recycling of FA from membrane lipids, e.g., plastid galactolipids or endomembrane phosphor- or betaine lipids. In this review, we address the relationship between cytosolic LDs and the complex membrane compartmentalization within stramenopile cells, the metabolic routes leading to TAG accumulation, and the physiological conditions that trigger LD production, in response to various environmental factors.

Piperidine based effective chemosensor for Zn(II) with the formation of binuclear Zn complex having specific Al(III) detection ability in aqueous medium and live cell images

A schiff base chemosensor HL [4-chloro-(((2-(piperidine-1-yl)imino)methyl)phenol], constructed by one step condensation of 2-aminoethyl piperidine and 5- Chloro Salicylaldehyde is illustrated to have its usefulness for selective and sensitive detection of Zn(II) among other metal ions in aqueous solution (HEPES buffer) displaying the colour changes from light blue to turquoise under UV light. The specific detection phenomena of Zn (II) is monitored by the remarkable fluorescence enhancement and notable change in NMR spectral data of fluorescence active HL after addition of Zn(II) to it. The impressive high binding constant in 106 orders, determined by electronic spectral titration after introduction of Zn(II) to HL assure the formation of a Zinc complex during sensing phenomena. In order to check whether the nuclearity of the constructed complex can be increased or not fluorescence enhancement phenomenon is further monitored in presence of different bridging ligands and the results display that only in presence of azide a significant enhancement of Zn(II)-HL domain is exposed where as for other bridging ligand the spectra remain unaltered. This observation insists to conduct the reaction between HL and ZnCl2 in presence of sodium azide which lead the formation of a Zn complex [Zn2(HL)2(N3)4] (complex 1) employing azide as the secondary anionic residue instead of bridging. The single crystal structure of the complex unveils the unique protonation of the piperidine N during the crystallization of the dinuclear motif of the complex 1. Furthermore the Zn complex due to the presence of remarkable luminescence property have been effectively used for selective sensing of Al(III) ion as metalloreceptor in HEPES buffer solution via turn of fluorescence with remarkable fluorescence quenching constant. In aqueous solution, complex 1 induces a 1:2 complex formation with Al(III) ion indicated by Job’s plot analysis. The DFT study suggests the formation of bimetal complex during sensing of Al(III) with complex 1 as metalloreceptor. The in vitro cell imaging study gives a authentic hints for in vivo biomedical application of HL as a selective and easy Zn(II) sensor. The two step sensing phenomena of HL and complex 1 is further established by advanced molecular logic gate formation.

Investigating the cell and developmental biology of plant infection by the rice blast fungus Magnaporthe oryzae

Magnaporthe oryzae is the causal agent of rice blast disease, the most widespread and serious disease of cultivated rice. Live cell imaging and quantitative 4D image analysis have provided new insight into the mechanisms by which the fungus infects host cells and spreads rapidly in plant tissue. In this video review article, we apply live cell imaging approaches to understanding the cell and developmental biology of rice blast disease. To gain entry to host plants, M. oryzae develops a specialised infection structure called an appressorium, a unicellular dome-shaped cell which generates enormous turgor, translated into mechanical force to rupture the leaf cuticle. Appressorium development is induced by perception of the hydrophobic leaf surface and nutrient deprivation. Cargo-independent autophagy in the three-celled conidium, controlled by cell cycle regulation, is essential for appressorium morphogenesis. Appressorium maturation involves turgor generation and melanin pigment deposition in the appressorial cell wall. Once a threshold of turgor has been reached, this triggers re-polarisation which requires regulated generation of reactive oxygen species, to facilitate septin GTPase-dependent cytoskeletal re-organisation and re-polarisation of the appressorium to form a narrow, rigid penetration peg. Infection of host tissue requires a further morphogenetic transition to a pseudohyphal-type of growth within colonised rice cells. At the same time the fungus secretes an arsenal of effector proteins to suppress plant immunity. Many effectors are secreted into host cells directly, which involves a specific secretory pathway and a specialised structure called the biotrophic interfacial complex. Cell-to-cell spread of the fungus then requires development of a specialised structure, the transpressorium, that is used to traverse pit field sites, allowing the fungus to maintain host cell membrane integrity as new living plant cells are invaded. Thereafter, the fungus rapidly moves through plant tissue and host cells begin to die, as the fungus switches to necrotrophic growth and disease symptoms develop. These morphogenetic transitions are reviewed in the context of live cell imaging studies.

Molecular Mechanisms of the Blockage of Glioblastoma Motility.

Glioblastoma (GBM) is the most common and lethal brain tumor. GBM has a remarkable degree of motility and is able to infiltrate the healthy brain. In order to perform a rationale-based drug-repositioning study, we have used known inhibitors of two small Rho GTPases, Rac1 and Cdc42, which are upregulated in GBM and are involved in the signaling processes underlying the orchestration of the cytoskeleton and cellular motility. The selected inhibitors (R-ketorolac and ML141 for Cdc42 and R-ketorolac and EHT 1864 for Rac1) have been successfully employed to reduce the infiltration propensity of GBM in live cell imaging studies. Complementarily, all-atom simulations have elucidated the molecular basis of their inhibition mechanism, identifying the binding sites targeted by the inhibitors and dissecting their impact on the small Rho GTPases' function. Our results demonstrate the potential of targeting the Rac1 and Cdc42 proteins with small molecules to contrast GBM infiltration growth and supply precious information for future drug discovery studies aiming to fight GBM and other infiltrative cancer types.

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

The effects of morphine, methadone, and fentanyl on mitochondria: A live cell imaging study

The important role of mitochondria in maintaining normal brain cell function has been demonstrated in several neurodegenerative diseases where mitochondrial dysfunction is a prominent feature. Accumulating evidence indicates that opioids may induce neuronal cell death and inhibit neurogenesis, two factors that are dependent on normal mitochondrial function. The aim of the present study was to examine the effects of morphine, methadone, and fentanyl on MitoTracker-stained mitochondria. Cells from the neuroblastoma/glioma hybrid cell-line NG108−15 were seeded on 96-well cell culture plates and treated with MitoTracker for 30 min prior to opioid treatment. Morphine, methadone, and fentanyl were added at various concentrations and images of mitochondria were acquired every 30 min for four hours using a high-content imaging device. The parameters total mitochondrial area, mitochondrial network, as well as the number and mean area of mitochondrial objects were analyzed using automated image analysis. Methadone and fentanyl, but not morphine, decreased the mitochondrial network, the number of mitochondrial objects, and increased the mean area of mitochondrial objects. Both methadone and fentanyl altered mitochondrial morphology with no effects seen from morphine treatment. These data suggest that methadone and fentanyl impact mitochondrial morphology negatively, which may be associated with neuronal cell death.

A red-to-near-infrared fluorescent probe for the detection of thiophenol based on a novel hydroxylflavone-quinoline-amino molecular system with large Stokes shift

In this work, we synthesized a novel long-wavelength-emitting fluorophore FQ-OH based on a novel designed hydroxylflavone-quinoline-amino molecular system with both intramolecular charge transfer (ICT) and excited-state intramolecular proton transfer (ESIPT) process, enabling FQ-OH with strong fluorescence in a wide range of 550–800 nm, covering red-to-near-infrared emission region and large stokes shift as much as 162 nm. Due to the promising spectra property, FQ-OH was then fabricated into a red-to-near-infrared fluorescent probe FQ-DNP for the selective detection of thiophenol via aromatic nucleophilic substitution (SNAr) reaction mechanism. Spectra assays in the solution demonstrated that FQ-DNP displayed prominent turn-on fluorescence response to thiophenol in 550–800 nm with emission peak at 627 nm, excellent selectivity, and exceptional sensitivity (detection limit as low as 7.2 nM). In addition, thiophenol in vapor form could be detected by FQ-DNP coated test papers enabling naked eye detection. Moreover, FQ-DNP was utilized for detecting thiophenol in environmental samples and showed great recovery results. Furthermore, biological application of FQ-DNP in living cells through cell imaging study demonstrated apparent intracellular fluorescence enhancement before/after thiophenol addition.

Solvent-Regulated Fluorimetric Differentiation of Al3+ and Zn2+ Using an AIE-Active Single Sensor.

The absence of d-orbital electrons or presence of full-filled d-orbital electrons in metal ions is a well-known Achilles' heel problem for the detection of these metal ions by a simple UV-visible study. For this reason, detection of metal ions such as Al3+ with no d-orbital electrons or Zn2+ with filled d-orbital electrons is a challenging task. Herein, we report a 2-naphthol-based fluorescent probe [1-((E)-((E)-(5-bromo-2-hydroxybenzylidene)hydrazono)methyl)naphthalen-2-ol] (H2L) that has been used to sense and discriminate Al3+ and Zn2+ via solvent regulation. The probe exhibits excellent selectivity and swift sensitivity toward Al3+ in MeOH-water (9:1, v/v) and toward Zn2+ in dimethyl sulfoxide (DMSO)-water (9:1, v/v) among various metal ions. The respective detection limit is found to be 9.78 and 3.65 μM. The sensing mechanism is attributed to multiple processes, viz., the inhibition of photo-induced electron transfer (PET) along with the introduction of chelation-enhanced emission (CHEF) and excited-state intramolecular proton transfer (ESIPT) inhibition, which are experimentally well verified by UV-vis absorption spectroscopy, emission spectroscopy, and NMR spectroscopy. The probe shows aggregation-induced emissive (AIE) response in ≥70% aqueous media as well as in the solid state. The experimental results are well corroborated by time-resolved photoluminescence (TRPL) and density functional theory (DFT) calculations. An advanced-level OR-AND-NOT logic gate has been constructed from a different chemical combinational input and emission output. The reversible recognition of both Al3+ in MeOH-water (9:1, v/v) and Zn2+ in DMSO-water (9:1, v/v) is also ascertained in the presence of Na2EDTA, enabling the construction of a molecular memory device. The probe H2L also detects intracellular Al3+/Zn2+ ions in Hela cells. Altogether, our fundamental findings will pave the way for designing and synthesis of unique chemosensors that could be used for cell imaging studies as well as constructing molecular logic gates.

Genetically Encoded Dual-Color Light-Up RNA Sensor Enabled Ratiometric Imaging of MicroRNA

MicroRNAs (miRNAs) play essential roles in regulating gene expression and cell fate. However, it remains a great challenge to image miRNAs with high accuracy in living cells. Here, we report a novel genetically encoded dual-color light-up RNA sensor for ratiometric imaging of miRNAs using Mango as an internal reference and SRB2 as the sensor module. This genetically encoded sensor is designed by expressing a splittable fusion of the internal reference and sensor module under a single promoter. This design strategy allows synchronous expression of the two modules with negligible interference. Live cell imaging studies reveal that the genetically encoded ratiometric RNA sensor responds specifically to mir-224. Moreover, the sensor-to-Mango fluorescence ratios are linearly correlated with the concentrations of mir-224, confirming their capability of determining mir-224 concentrations in living cells. Our genetically encoded light-up RNA sensor also enables ratiometric imaging of mir-224 in different cell lines. This strategy could provide a versatile approach for ratiometric imaging of intracellular RNAs, affording powerful tools for interrogating RNA functions and abundance in living cells.

Effect of structural variation on tumor targeting efficacy of cationically charged porphyrin derivatives: Comparative in-vitro and in-vivo evaluation for possible potential in PET and PDT

tetracationic (TMPyP) and tricationic porphyrin (TriMPyCOOHP) derivatives were synthesized, characterized and investigated for binding with DNA by Isothermal Titration Calorimetry as well as by UV-Vis spectroscopy in order to study the effect of structural variation on tumor targeting efficacy of cationically charged porphyrin derivatives. Fluorescence cell imaging studies performed in cancer cell lines corroborated the findings of aforementioned studies. Photocytotoxicity experiments in A549cell lines revealed relatively higher light dependent cytotoxic effects exerted by TMPyP compared to TriMPyCOOHP. In-vivo experiments in tumor bearing animal model revealed relatively longer retention of 68Ga-TMPyP in tumorous lesion compared to that of 68Ga-TriMPyCOOHP. The study reveals that removal of one of the positive charges of the tetracationic porphyrin derivatives significantly reduces their DNA binding ability and cytotoxicity as well as brings changes in the pharmacokinetic pattern and tumor retention in small animal model.

A bio-compatible pyridine-pyrazole hydrazide based compartmental receptor for Al3+ sensing and its application in cell imaging.

For practical applications, the development of bio-compatible organic molecules as p-block ion chemosensors is critical. Herein, we report the single crystal (SC) of new pyridine-pyrazole derived Al3+ sensor H2PPC [(Z)-N'-(2,3-dihydroxybenzylidene)-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazide] as well as its Cu-complex SC. The probe exhibits an "off-on" fluorescence response towards Al3+ ions, and this has been modulated with different solvents. For selective detection of Al3+ ions, a special coordination pocket in the structural backbone is advantageous. The chemosensor exhibits a submicromolar detection level (LOD = 4.78 μM) for Al3+. The density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations of H2PPC and [Al(HPP)2]+ (1) reveal that a change of the structural conformation of probe H2PPC upon complexation causes the pyrazole and pyridine units to create a specific cavity to tether Al3+, and consequently H2PPC proves to be a promising molecule for Al3+ detection. Furthermore, the probe has been successfully used to evaluate Al3+ as a low-cost kit using filter paper strips, and the in situ Al3+ ion imaging in Vero cells as well as A549 cell lines shows the sensor's nuclear envelope penetrability, indicating that it has great potential for biological and environmental applications.

Fabrication of a fluorescent probe for reversibly monitoring mitochondrial membrane potential in living cells.

Mitochondria are important organelles in cells, which play an important role in metabolism and many other vital biological events. Mitochondrial membrane potential (MMP) is a significant biological parameter participating in various procedures. However, fluorescent probes for monitoring MMP are rarely reported, which greatly limited the related studies. Herein, we present the rational design, synthesis, and living cell imaging studies of a fluorescent probe REP for monitoring MMP changes based on organic cationic fluorophores. In live cells with high MMP levels, REP can exclusively light up mitochondria with intense fluorescence. Upon the loss of MMP, the emission of intracellular REP evidently decreased. The reversible changes in MMP have been successfully monitored by REP, and the oxidative damages to live cells have been detected with the probe. The probe is expected to serve as a desired tool in studying MMP and related areas.

Study of the Parameters Affecting the Loading of Fluorescein on Coated Gold Nanoparticles: Promising Nanostructure for Cancer Diagnosis.

Recent advances in nanotechnology have led to the use of nanomaterials in the diagnosis of cancer by imaging techniques. This study aimed to synthesize fluorescein-conjugated gold nanoparticles and study the parameters affecting the loading of fluorescein on synthesized coated gold nanoparticles with the ability to be used in medical diagnostic methods. The synthesized gold nanoparticles were functionalized with polyethylene glycol. Then, these particles were conjugated with fluorescein under different conditions. To investigate the optical and structural features as well as the factors affecting the loading, the nanoparticles were evaluated by ultraviolet-visible, fluorescence and FT-IR spectrophotometer, fluorescence spectrophotometer, transmission electron microscopy, dynamic light scattering, and zeta potential measuring device. Also, the use of these particles in cancer diagnosis on the skin melanoma cell (B16F10) was examined using a fluorescence microscope. PEG-coated spherical gold nanoparticles were synthesized as a carrier for the fluorescein dye detector. The coating agent concentration, incubation time, temperature, and pH of the medium affected the loading efficiency of fluorescein on the nanoparticles. Also, optimal conditions for use in the diagnostic applications were investigated. Ten micromolar of the sample were selected for cell imaging studies. The fluorescence signal of B16F10 cells containing nanoparticles was relatively strong, indicating the amount of nanoparticles uptaken by the cells. The results showed that by designing fluorescent gold nanoparticles with fluorescein as fluorescent detectors and considering their diagnostic importance, an efficient way to diagnose incurable diseases can be found.

Development of two-photon fluorescence probe for detecting cyclooxygenase-2 level in human colorectal cancer tissue

Abstract Cyclooxygenase-2 is overexpressed in all stages of cancers and thus serves as an attractive biomarker for early cancer diagnosis. In this study, we report a two-photon probe (SCX) for cyclooxygenase-2 which can reflect the intracellular enzyme level and distinguish between cancerous and normal tissue in colorectal cancer patients. SCX is based on a novel two-photon fluorophore (PBT) possessing phenanthrene donor and benzothiazole acceptor, and indomethacin as a COX-2 targeting unit. The in vitro and cell imaging studies revealed that SCX could distinguish the COX-2 expression levels in cancerous and normal cells. Furthermore, for the first time, normal and cancerous tissues could clearly be distinguished in human biopsy samples by using a COX-2 responsible two-photon probe.

The Performance of Minicircle DNA Versus Parental Plasmid in p53 Gene Delivery Into HPV-18-Infected Cervical Cancer Cells

Minicircle DNA (mcDNA) has been suggested as a vanguard technology for gene therapy, consisting of a nonviral DNA vector devoid of prokaryotic sequences. Unlike conventional plasmid DNA (pDNA), this small vector is able to sustain high expression rates throughout time. Thus, this work describes the construction, production, and purification of mcDNA-p53 and its precursor parental plasmid (PP)-p53 for a comparative study of both DNA vectors in the growth suppression of human papillomavirus (HPV)-18-infected cervical cancer cells. First, live cell imaging and fluorescence microscopy studies allowed to understand that mcDNA-p53 vector was able to enter cell nuclei more rapidly than PP-p53 vector, leading to a transfection efficiency of 68% against 34%, respectively. Then, p53 transcripts and protein expression assessment revealed that both vectors were able to induce transcription and the target protein expression. However, the mcDNA-p53 vector performance stood out, by demonstrating higher p53 expression levels (91.65 ± 2.82 U/mL vs. 74.75 ± 4.44 U/mL). After assuring the safety of both vectors by viability studies, such potential was confirmed by proliferation and apoptosis assays. These studies confirmed the mcDNA-p53 vector function toward cell cycle arrest and apoptosis in HPV-18-infected cervical cancer cells. Altogether, these results suggest that the mcDNA vector has a more promising and efficient role as a DNA vector than conventional pDNA, opening new investigation lines for cervical cancer treatment in the future.

A Peptide Stapling Strategy with Built-In Fluorescence by Direct Late-Stage C(sp2 )-H Olefination of Tryptophan.

Fluorescent stapled peptides are important chemical tools for detecting intracellular distribution, protein-protein interactions, and localization of target proteins. These peptides are usually labeled with bulky sized fluorophores through reactive functional groups, which may alter the physical properties and biological activities of peptides. Herein, a unique strategy is developed for synthesizing new stapled peptides with built-in fluorescence. The stapled peptides were prepared through Rh-catalyzed C(sp2 )-H olefination in tryptophan (Trp) residues by using pyridine/pyrimidine as the directing groups under mild conditions. This method displays good regioselectivity and high efficiency. Furthermore, as a proof of concept for its biological applications, stapled peptides without additional fluorophore 9 a and 9 b were constructed for a cell imaging study. These peptides displayed strong binding affinity toward integrin αvβ3 in A549 cells by cell imaging experiments. Notably they demonstrated even better anticancer activity than commercial antagonist cyclic (RGDfK). The method will provide robust tools for the peptide macrocyclization field.

Picoline based fluorescence ‘turn-on’ chemosensor for zinc(II) ion recognition, cell imaging and cytotoxicity study: Synthesis, crystal structure, spectroscopy and DFT

A new picoline based ligand, namely 2-hydroxy-5-methyl-3-[{(6-methylpyridin-2-yl)imino}methyl]benzaldehyde (L) and it’s zinc(II) complex, Zn(L)2 (1) have been synthesized and structurally characterized. The ligand (L) selectively interacts with Zn2+ ion in presence of series of cations in CH3CN-H2O (v/v 1:1) in 1 mM HEPES buffer (pH 7.2). The fluorescence intensity of L is significantly enhanced, and it is increased to 52 times on coordination with Zn(II) ion. The fluorescence intensity value of the L does not show any significant change in the pH range 5 to 9, while the extent of emission phenomenon with Zn(II) ions is observed in the said pH range. The detection limit (0.36 µM) and association constant (log Kapp = 13.25) are evaluated by the fluorescence emission experiment. The probe shows reversibility in addition of dihydrogen phosphate (H2PO4−) ion to the 1. Additionally, the ‘turn-on’ fluorescence probe has sufficient cell permeability and intracellular Zn(II) sensing property as envisaged from the microscopic imaging in HEK293T cells. Both L and ZnL2 (1) are innocuous against PBMC (peripheral blood mononuclear cells) but effective antitumor agents against U-937 cancer cells.

Synthesis and Spectroscopic Properties of Optical Probe Based on Schiff Base with Biological Application

A series of facile optical probe has been easily developed by a one-step Schiff base type reaction of 2,4-dihydroxybenzaldehyde and ortho, meta or para aminophenol. Schiff base compounds as fluorescence sensor were utilized to identify metal ions by spectrophotometric techniques. The data of absorption and emission spectra displayed the extraordinary selective and sensitive sensor properties for Schiff base probe derived from ortho aminophenol (SB-2) toward Al3+ ions. Upon introducing Al3+ ions, an excellent increase in the fluorescence intensity of the probe (SB-2) resulting in color change was observed because of blocking the photoinduced electron transfer (PET) mechanism of azomethine unit. The specific bonding mode of probe (SB-2) with Al3+ was verified by using a series of spectroscopic techniques such as FT-IR, 1H NMR, and UV-vis (Job-plot data). The detection limit of probe (SB-2) toward Al3+was determined around 10−7M. Furthermore, cell imaging studies of probe (SB-2) were also performed and from these experiments, it was seen that the presence of even trace amounts of Al3+ in living cells could be noticeably detected by (SB-2). In this study, antimicrobial properties of Schiff base compounds were also carried out towards some selected bacteria species. This presented work provides a method for design, facile synthesis and application of effective fluorescence probes toward Al3+ ions in biological systems.