Synthetic peptides with selective affinity for apoptotic cells

The appearance of anionic phosphatidylserine (PS) in the outer monolayer of the plasma membrane is a universal indicator of the early/intermediate stages of cell apoptosis. The most common method of detecting PS on a cell surface is to use the protein annexin V; however, in certain applications there is a need for alternative reagents. Recent research indicates that rationally designed zinc 2,2'-dipicolylamine (Zn2+-DPA) coordination complexes can mimic the apoptosis sensing function of annexin V. Here, a series of fluorescently-labelled, tri- and pentapeptides with side chains containing Zn2+-DPA are prepared and shown to selectively bind to anionic vesicle membranes. Fluorescein-labelled versions of the peptides are used to detect apoptotic cells by fluorescence microscopy and flow cytometry.     

Cofactor-free detection of phosphatidylserine with cyclic peptides mimicking lactadherin

Cyclic peptides (cLacs) are designed to mimic the natural phosphatidylserine (PS) binding protein lactadherin. Unlike annexin V or its small molecule mimics, the cLac peptides selectively target PS-presenting membranes with no need for metal cofactors. We further show that a fluorophore-labeled cLac effectively stains early apoptotic cells. The small size and facile conjugation with a variety of imaging tracers make the cLac design promising for imaging cell death in vitro as well as in living organisms.     

Characterization of the early stages of programmed cell death in maize root cells by using comet assay and the combination of cell electrophoresis with annexin binding

An emerging topic in plant biology is whether plant cells display similar elements of programmed cell death (PCD) as animal cells do. We have studied cell death in maize roots exposed to cold stress by using fluorescence microscopy, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL), DNA gel electrophoresis, single cell gel electrophoresis (SCGE), cell electrophoresis, and annexin binding techniques. The results showed that cell death in maize root cells triggered by cold stress was accompanied by a subset of features characteristic of animal PCD such as nuclear condensation and fragmentation, and oligonucleosomal DNA fragmentation. In addition to DNA laddering and TUNEL positivity, a "comet" pattern indicative of DNA breakage appeared as short as after one day of treatment. The maize root cell PCD process was also accompanied by an increase in negative surface charge of the dying cells due to exposure of phosphatiolylserine (PS) from inner to outer membrane. After annexin binding, however, the enhanced electrophoretic mobility (EPM) of the dying cells decreased nearly to normal values. This result suggests that the combination between cell electrophoresis and annexin binding provides a quantitative method for monitoring PS exposure during plant PCD.     

Biocompatible fluorescent polyamine‐based cyclophosphazene hybrid nanospheres for targeted cell imaging

Fluorescent nanoprobes are highly desirable toolkit for bioimaging applications. This study reports the first example for the synthesis of a nontoxic prototypical fluorescent organic compound 2‐benzo[d]thiazol‐2‐yl)‐3‐(2‐chloro‐4‐(dimethylamino)phenyl)acrylonitrile (BCA) and its entrapment into the poly[cyclotriphosphazene‐co‐polyethyleneimine] cross‐linked (PCPEI) nanospheres named as BCA@PCPEI for targeted cell imaging application. The as‐prepared BCA@PCPEI nanospheres were thoroughly characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and phosphorus‐31 nuclear magnetic resonance (³¹P‐NMR) analyses. The surface functional analysis of the nanospheres was performed by X‐ray photoelectron spectroscopy (XPS), which proves that the content ratios of elements belong to the precursors concentrations. The as‐prepared nanospheres displayed emission at 606 nm with bright orange fluorescence at any concentration. Moreover, the nanospheres were also less cytotoxic and maintained remarkable cell viability up to 100 μg/mL. Owing to the fluorescence with higher emission, this material has shown excellent cell imaging performance with better targeting ability to HeLa cells.     

Polymer Electron Acceptors Based on Fluorinated Isoindigo Unit for Polymer Solar Cells

Most of efficient polymer electron acceptors for polymer solar cells (PSCs) are based on naphthalene diimide or perylene diimide as the electron deficient building block. In this paper, for the first time, we report polymer electron acceptors based on fluorinated isoindigo (F‐IID) as the electron deficient building block. We synthesized two polymer electron acceptors consisting of alternating F‐IID unit and thiophene/selenophen unit. They show low‐lying LUMO/HOMO energy levels of –3.69/–5.69 eV, high electron mobilities of 1.31×10^–5 cm²·V^–1·s^–1 and broad absorption spectra with the optical bandgap of 1.61 eV. PSC devices using the two F‐IID‐based polymers as polymer electron acceptors show encouraging power conversion efficiencies (PCEs) of up to 1.50% with an open‐circuit voltage (V_OC) of 0.97 V, a short‐circuit current density (J_SC) of 2.91 mA·cm^–2, and a fill factor (FF) of 53.2%. This work suggests a new kind of polymer electron acceptors based on F‐IID unit.     

Multifunctional Logic in a Photosensitizer with Triple‐Mode Fluorescent and Photodynamic Activity

Herein we describe a photosensitizer (PS) with the capacity to perform multiple logic operations based on a pyrene‐containing phthalocyanine (Pc) derivative. The system presents three output signals (fluorescence at 377 and 683 nm, and singlet oxygen (¹O₂) production), which are dependent on three inputs: two chemical (concentration of dithiothreitol (DTT) and acidic pH) and one physical (visible light above 530 nm for ¹O₂ sensitization). The multi‐input/multioutput nature of this PS leads to single‐, double‐, and triple‐mode activation pathways of its fluorescent and photodynamic functions, through the interplay of various interrelated AND, ID, and INHIBIT gates. Dual fluorescence emissions are potentially useful for orthogonal optical imaging protocols while ¹O₂ is the main reactive species in photodynamic therapy (PDT). We thus expect that this kind of PS logic system will be of great interest for multimodal cellular imaging and therapeutic applications.     

Biocompatible Triplex Ag@SiO2@mTiO2 Core–Shell Nanoparticles for Simultaneous Fluorescence‐SERS Bimodal Imaging and Drug Delivery

Herein, we report the synthesis of biocompatible triplex Ag@SiO₂@mTiO₂ core–shell nanoparticles (NPs) for simultaneous fluorescence‐surface‐enhanced Raman scattering (F‐SERS) bimodal imaging and drug delivery. Stable Raman signals were created by typical SERS tags that were composed of Ag NPs for optical enhancement, a reporter molecule of 4‐mercaptopyridine (4‐Mpy) for a spectroscopic signature, and a silica shell for protection. A further coating of mesoporous titania (mTiO₂) on the SERS tags offered high loading capacity for a fluorescence dye (flavin mononucleotide) and an anti‐cancer drug (doxorubicin (DOX)), thereby endowing the material with fluorescence‐imaging and therapeutic functions. The as‐prepared F‐SERS dots exhibited strong fluorescence when excited by light at 460 nm whilst a stable, characteristic 4‐Mpy SERS signal was detected when the excitation wavelength was changed to longer wavelength (632.8 nm), both in solution and after incorporation inside living cells. Their excellent biocompatibility was demonstrated by low cytotoxicity against MCF‐7 cells, even at a high concentration of 100 μg mL^?1. In vitro cell cytotoxicity confirmed that DOX‐loaded F‐SERS dots had a comparable or even greater therapeutic effect compared with the free drug, owing to the increased cell‐uptake, which was attributed to the possible endocytosis mechanism of the NPs. To the best of our knowledge, this is the first proof‐of‐concept investigation on a multifunctional nanomedicine that possessed a combined capacity for fast and multiplexed F‐SERS labeling as well as drug‐loading for cancer therapy.     

When Molecular Probes Meet Self‐Assembly: An Enhanced Quenching Effect

We demonstrate that the incorporation of one or two amino acids of phenylalanine (F) or 4‐fluoro phenylalanine (^fF) will greatly lower the background fluorescence intensities of conventional quenched probes with quenchers. This enhanced quenching effect was due to the synergetic effect of the aggregation caused quenching and the presence of a quencher. Such strategy will not greatly affect the enzyme recognition properties to the probes. We also demonstrated that our self‐assembled nanoprobe with the enhanced quenching effect showed a better performance in cells for the detection of cell apoptosis than the unassembled probes. Our study demonstrates that using molecular self‐assembly can optimize and improve the performance of molecular probes and it provides a simple but very useful strategy to boost the signal‐to‐noise ratios of fluorescence probes.     

Design, synthesis, and biological evaluation of a dansyled amino acid derivative as an imaging agent for apoptosis

To develop a small molecule-based biomarker for in vivo apoptosis imaging, a dansyled amino acid derivative (BNSBA) was designed and synthesized in good yield. The biological evaluation demonstrated that BNSBA selectively binds to apoptotic cancer cells and is localized within the cytoplasm of cells that bound annexin V on the plasma membrane.     

Anchoring Supramolecular Polymers to Human Red Blood Cells by Combining Dynamic Covalent and Non‐Covalent Chemistries

Understanding cell/material interactions is essential to design functional cell‐responsive materials. While the scientific literature abounds with formulations of biomimetic materials, only a fraction of them focused on mechanisms of the molecular interactions between cells and material. To provide new knowledge on the strategies for materials/cell recognition and binding, supramolecular benzene‐1,3,5‐tricarboxamide copolymers bearing benzoxaborole moieties are anchored on the surface of human erythrocytes via benzoxaborole/sialic‐acid binding. This interaction based on both dynamic covalent and non‐covalent chemistries is visualized in real time by means of total internal reflection fluorescence microscopy. Exploiting this imaging method, we observe that the functional copolymers specifically interact with the cell surface. An optimal fiber affinity towards the cells as a function of benzoxaborole concentration demonstrates the crucial role of multivalency in these cell/material interactions.     

Near‐Infrared Light‐Mediated Photoactivation of a Platinum Antitumor Prodrug and Simultaneous Cellular Apoptosis Imaging by Upconversion‐Luminescent Nanoparticles

Platinum‐based drugs are among the most active antitumor reagents in clinical practice; their application is limited by side effects and drug resistance. A novel and personalized near‐infrared (NIR) light‐activated nanoplatform is obtained by combining a photoactivatable platinum(IV) prodrug and a caspase imaging peptide conjugated with silica‐coated upconversion‐luminescent nanoparticles (UCNPs) for the remote control of antitumor platinum prodrug activation, and simultaneously for real‐time imaging of apoptosis induced by activated cytotoxicity. Upon NIR light illumination, the Pt^IV prodrug complex is activated at the surface of the nanoparticle and active components are selectively released which display cytotoxicity against human ovarian carcinoma A2780 cells and its cisplatin‐resistant variant A2780cis cells. More importantly, the caspases enzymes triggered by cytotoxicity would effectively cleave the probe peptide, thereby allowing the direct imaging of apoptosis in living cells.     

Photo‐switchable spiropyran immobilized polystyrene beads using catechol chemistry

Catechol and spiropyran functional groups were conjugated to a polymer backbone, allowing immobilization on polystyrene beads (PS beads). The final product was capable of stably reproducing the optical properties of spiropyran. Through the outstanding surface adhesion properties of the catechol functional group, spiropyran was immobilized on PS beads. Switchable photoluminescence in the spiropyran coated PS bead surfaces was observed depending on irradiation with either UV or visible light. The surfaces of the PS beads were morphologically examined by field emission scanning electron microscopy and X‐ray photoelectron spectroscopy was used for characterization of the constituent atoms. Furthermore, UV–Vis and fluorescence spectroscopy were used to confirm conversion between the spiropyran (SP) and merocyanine (MC) forms through UV or visible light irradiation on SP, while fluorescent images for both SP and MC were studied using confocal laser scanning microscopy. The confocal images of the SP‐PS beads system onto MDAMB‐231 cells under UV and visible light indicate the cellular uptake by emerging color within the cytoplasm. Advancing study, the remaining catechol groups can confers adhesive properties, given by contact angle data of various coated surfaces film. These stimuli‐responsive coatings are compatible as drawing switchable photochromic material on versatile substrate shown in confocal images of propylene film. Overall, this great water solubility and biocompatibility PS beads system also showed potential as cell bio‐imaging light stimuli responsive material, and the benefits of this system can also possibly address coat able advanced material for a wide range of surface light sensor applications. Copyright © 2017 John Wiley & Sons, Ltd.     

Bystander Effect Induced by UVC Radiation in Chinese hamster V79 cells

In past decades, researches on radiation‐induced bystander effect mainly focused on ionizing radiation such as α‐particle, β‐particle, X‐ray and γ‐ray. But few researches have been conducted on the ability of ultraviolet (UV) radiation‐induced bystander effect, and knowledge of UVC‐induced bystander effect is far limited. Here, we adopted medium transfer experiment to detect whether UVC could cause bystander effect in Chinese hamster V79 cells. We determined the cell viability, apoptosis rate, chromosome aberration and ultrastructure changes, respectively. Our results showed that: (1) the viability of UVC‐irradiated V79 cells declined significantly with the dosage of UVC; (2) similar to the irradiated cells, the main death type of bystander cells cultured in irradiation conditioned medium (ICMs) was also apoptosis; (3) soluble factors secreted by UVC‐irradiated cells could induce bystander effect in V79 cells; (4) cells treated with 4 h ICM collected from 90 mJ cm^?2 UVC‐irradiated cells displayed the strongest response. Our data revealed that UVC could cause bystander effect through the medium soluble factors excreted from irradiated cells and this bystander effect was a novel quantitative and kinetic response. These findings might provide a foundation to further explore the exact soluble bystander factors and detailed mechanism underlying UVC‐induced bystander effect.     

Synthesis and Application of a Full Water‐Soluble and Red‐Emitting Chemosensor Based on Phenoxazinium for Copper(II) Ions

A phenoxazinium‐based chemosensor ( 1 ) bearing di(2‐picolyl)amine unit was successfully synthesized. The result shows that it is a red‐emitting and full water‐soluble chemosensor for the selective detection of Cu²⁺ in pure water. The fluorescence on‐off mechanism was studied by ab initio calculations. To confirm the suitability of 1 for biological applications, it was employed in the fluorescence detection of the intracellular Cu²⁺ with cultured KB cells. The results indicated that 1 had good membrane permeability and could be useful for the fluorescence microscopic imaging.     

Photovoltaic properties and femtosecond time‐resolved fluorescence study of polyoxometalate‐containing rod–coil diblock copolymers

The photovoltaic properties and exciton decay dynamics of three polyoxometalate (POM)‐containing hybrid rod–coil diblock copolymers (HDCPs), PS‐Mo6‐PT1–3 , are studied. Single‐component photovoltaic cells of PS‐Mo6‐PT2 and inverted solar cells based on ZnO nanorod arrays/ PS‐Mo6‐PT1–3 are fabricated showing power conversion efficiencies only up to 0.055%. To understand the poor photovoltaic performance, femtosecond fluorescence up‐conversion technique is used to study the exciton decay dynamics of all three HDCPs. Drastically different fluorescence dynamics of the three HDCPs are observed in dilute solutions, which is attributed to the different extent and different type of interpolymer association depending on the P3HT rod block length and the cluster loading ratio. While both cation‐mediated POM cluster association and P3HT‐P3HT π‐stacking contribute significantly to PS‐Mo6‐PT2 aggregation, the aggregation of PS‐Mo6‐PT1 and that of PS‐Mo6‐PT3 is driven predominantly by cluster association and π‐stacking, respectively. In conjunction with the high residual polarization anisotropy, it is concluded that charge transfer from P3HT excitons to POM clusters in all three HDCPs is inefficient. An improved system with direct π‐conjugation between the POM clusters and the rod block addressing this issue has been proposed. © 2013 Wiley Periodicals, 2014 , 52, 122–133     

Highly Selective Mitochondrial Targeting by a Ruthenium(II) Peptide Conjugate: Imaging and Photoinduced Damage of Mitochondrial DNA

Mitochondrial DNA (mtDNA) plays a crucial but incompletely understood role in cellular biochemistry and etiology of numerous disease states. Thus, there is an urgent need for targeted probes that can dynamically respond to changes to mtDNA such as copy number in live cells, but it is difficult to permeate the mitochondrial membrane of the living cell. Now, a ruthenium(II) light‐switching probe targeted by peptide vectorization selectively to mitochondrial nucleoids is presented. Evidence for DNA binding by the probe in live cells is derived from confocal fluorescence microscopy, resonance Raman, and luminescence lifetime imaging. While viable under imaging conditions, specific staining of mitochondrial DNA permitted efficient and selective photoinduced toxicity on a cell‐by‐cell basis under higher excitation intensities. This powerful combination of imaging and photocytotoxicity is an important step towards realizing phototheranostic application of such Ru^II probes.     

A Mitochondria-targeted AIEgen Labelled with 18F for Breast Cancer Cell Imaging and Therapy

A lack of efficient diagnostic tools for early and noninvasive diagnosis of breast cancer has restricted the clinical treatment effect. This problem might be addressed by the combination of aggregation-induced emission (AIE) fluorescence imaging and positron emission tomography (PET) with the dual advantages of high resolution and easy operation, and unlimited penetration and high sensitivity. Here, a mitochondria-targeted AIE luminogen (AIEgen) radiolabeled with ¹⁸F was developed through a two-step radiochemical reaction by virtue of a prosthetic group. The obtained ^18/19F-Bz-CP imaging probe was examined by in vitro cell uptake and cell proliferation inhibition in two breast cancer cell lines, showing that the probe can efficiently target and locate in the mitochondria through the analysis of fluorescence imaging and PET simultaneously. Additionally, the probe can induce cancer cell apoptosis with the half maximal inhibitory concentration (IC50) of 4.8 μM for MCF-7 cells and 7.2 μM for T47D cells, indicating its potential application for breast cancer therapy.     

Organoboron Schiff bases as cell‐staining fluorescent probes: Synthesis,Chemio‐photophysical characterization,DFT, and X‐ray structures

The fluorescence imaging technologies are becoming the most powerful and noninvasive diagnostic tools in cellular biology and modern medicine where abnormal cell arrangements are associated with diseases. Thus, these techniques require new fluorescent dyes with excellent chemical, physical, and photophysical properties. A series of four new Boron Schiff bases ( 1 – 4 ) has been prepared by condensation between phenylboronic acid with the corresponding ligand. The compounds were characterized by NMR (¹H, ¹³C, and ¹¹B), UV/vis, fluorescence spectroscopy, and high‐resolution mass spectrometry. The crystal structures of three compounds showed tetracoordinated Boron atoms with semiplanar skeleton ligands. Interesting organoboron response to viscosity on their fluorescence (Φ: more than 3‐fold). Additionally, compounds 1 and 2 were found to serve as a fluorescent dye for cell imaging (B16F10, CaCo, and A‐431 cells) since it has the capability to rapidly accumulate within the cells and gave bright green fluorescence, it showed low cytotoxicity activity and high photostability in solution. Additionally, the compounds have also been investigated using DFT.     

β-Cyclodextrin/glycyrrhizic acid functionalised quantum dots selectively enter hepatic cells and induce apoptosis

The use of active components from important medical herbs has proved effective in treating various cancers. Glycyrrhizic acid (GA) is one of the many interesting triterpenoic acids with anticancerogenic potential, and is known to trigger apoptosis in hepatocarcinoma cells. In this study we combined quantum dots (QDs) with GA in the presence of β‐cyclodextrin (β‐CD), and prepared β‐CD/GA‐functionalised QDs, which led to improved antitumor activity and induced apoptosis in hepatocarcinoma cells. These compounds showed a better selectivity for hepatic cells compared to HeLa and ECV‐304 cells. Hoechst and annexin V–FITC staining and mitochondrial membrane potential (MMP) experiments proved an apoptotic effect of these compounds on HepG2 cells. At the same time, transmission electron microscopy (TEM) showed obvious features of apoptosis, for example, irregularities of nuclear shapes, mitochondria swelling, clumping and peripheral chromatin condensation, zeiosis or blebbing of the plasma membrane and formation of apoptotic bodies. It is notable that β‐CD/GA‐functionalised QDs showed effective cell growth inhibition by triggering G0/G1 phase arrest and inducing apoptosis through an reactive oxygen species mediated mitochondrial dysfunction pathway. β‐CD/GA‐functionalised QDs primarily induced apoptotic response in a time‐ and dose‐dependent manner, but little apoptosis appeared with L ‐Cys‐β‐CD‐functionalised QDs or GA alone. These studies suggest that β‐CD/GA‐functionalised QDs have therapeutic potential against cancer.     

Design and Synthesis of a Highly Sensitive Off–On Fluorescent Chemosensor for Zinc Ions Utilizing Internal Charge Transfer

Fluorescence imaging is a powerful tool for the visualization of biological molecules in living cells, tissue slices, and whole bodies, and is important for elucidating biological phenomena. Furthermore, zinc (Zn²⁺) is the second most abundant heavy metal ion in the human body after iron, and detection of chelatable Zn²⁺ in biological studies has attracted much attention. Herein, we present a novel, highly sensitive off–on fluorescent chemosensor for Zn²⁺ by using the internal charge transfer (ICT) mechanism. The rationale of our approach to highly sensitive sensor molecules is as follows. If fluorescence can be completely quenched in the absence of Zn²⁺, chemosensors would offer a better signal‐to‐noise ratio. However, it is difficult to quench the fluorescence completely before Zn²⁺ binding, and most sensor molecules still show very weak fluorescence in the absence of Zn²⁺. But even though the sensor shows a weak fluorescence in the absence of Zn²⁺, this fluorescence can be further suppressed by selecting an excitation wavelength that is barely absorbed by the Zn²⁺‐free sensor molecule. Focusing on careful control of ICT within the 4‐amino‐1,8‐naphthalimide dye platform, we designed and synthesized a new chemosensor ( 1 ) that shows a pronounced fluorescence enhancement with a blueshift in the absorption spectrum upon addition of Zn²⁺. The usefulness of 1 for monitoring Zn²⁺ changes was confirmed in living HeLa cells. There have been several reports on 4‐amino‐1,8‐naphthalimide‐based fluorescent sensor molecules. However, 1 is the first Zn²⁺‐sensitive off–on fluorescent sensor molecule that employs the ICT mechanism; most off–on sensor molecules for Zn²⁺ employ the photoinduced electron transfer (PeT) mechanism.