Simultaneous Morphologies and Luminescence Control of NaYF_(4)∶Yb/Er Nanophosphors by Surfactants for Cancer Cell Imaging

Hydrophilic rare-earth up-conversion nanophosphors(UCNPs)with small sizes and a strong up-conversion luminescence have attracted much interest.Herein the simultaneous control of morphologies and the up-conversion luminescence intensities was reported for NaYF_(4)∶Yb/Er nanophosphors by a facile hydrothermal procedure with different surfactants.With the change of the surfactants from polyvinylpyrrolidone(PVP)to sodium citrate(CIT),edetate disodium(EDTA)or sodium dodecyl benzenesulfonate(SDBS),the morphology of NaYF_(4)∶Yb/Er nanophosphors transformed from nanoparticles with a diameter of about 70.0 nm to hexagonal nanoblocks with a thickness of about 125.0 nm and a length of about 240.0 nm,nanorods with a diameter of about 700.0 nm and a length of about 2.6μm,or nanowires with a diameter of 250.0 nm and a length of about 3.2μm.Simultaneously,their up-conversion luminescence intensity went down gradually under laser irradiation at a wavelength of 980 nm due to the increase of photobleaching.PVP-capped NaYF_(4)∶Yb/Er nanoparticles exhibited the smallest size and the strongest up-conversion luminescence intensity.Biological experiment results revealed that NaYF_(4)∶Yb/Er nanophosphors exhibited a high biocompatibility and could be used as biological labels with a perfect signal-to-noise ratio for cancer cell imaging.

Synthesis of Fluorescent Carbon Quantum Dots and Their Application in the Plant Cell Imaging

Carbon quantum dots(CQDs) exhibit tremendous advantages for plant growth study due to its strong fluorescence and good biocompatibility. The fluorescent CQDs were synthesized by the onestep microwave method with the raw materials of citric acid(CA) and urea(UR), and expressed a unique green fluorescence with the optimal excitation wavelength of over 400 nm through adjusting the doping of N elements. It is demonstrated that CQDs can act as deliver media in plant and fluorescent probes for plant cell imaging through directly cultivated in the seedlings of melon and wheat, respectively. Based on the effects of the fluorescent CQDs on plants growth, we can further study the mechanisms of the ions transport in plants.

Preparation of Fluorescent Carbon Dots from Chinese Herbal Medicine Alisma and Its Potential Applications in Photocatalytic Degradation of Malachite Green and Cell Imaging

Natural plants and Chinese herbal medicines are valuable resources.It is one of the new tasks for medical workers to study the new application fields of these resources.In this work,one kind of traditional Chinese herbal plant,Alisma,was chosen as a carbon source to synthesize the carbon dots(CDs).This kind of CDs has an amorphous carbon structure and shows strong stability to time,temperature,and ion strength.The results show that the degradation efficiency of malachite green dye can reach 100%in 4.5 h without illumination,and the degradation efficiency is better than that in dark environment.In addition,the CDs have also been successfully applied to HeLa cell imaging.Simple synthesis method,stable properties,good photodegradation and bioimaging applications make this material of great application value.

Highly efficient and non-doped red conjugated polymer dot for photostable cell imaging

By introducing a naphthothiadiazole(NT)unit as the main building block,a non-doped and red emissive conjugated polymer poly(9,9-dihexylfluorene-alt-naphthothiadiazole)(PFNT)is readily obtained through a two-step synthesis.Since the NT unit has a large twist angle with its neighboring segment,the aggregation-induced quenching(AIQ)effect of PFNT can be effectively suppressed in the condensed state.As a result,the corresponding PFNT polymer dot(Pdot)exhibits a high fluorescence quantum yield of53.2%with peak emission at 616 nm,which is one of the most efficient red Pdots known.PFNT Pdot shows good biocompatibility and can be employed for living cell fluorescent imaging with high brightness.It also can be used for specific subcellular organelle imaging through immunofluorescence labeling.Furthermore,the PFNT Pdot demonstrates much better photostability for long-time cell fluorescence imaging than commercial red dyes.The high performances of PFNT Pdot make it a promising fluorescent probe for practical bioapplications.

Emerging advances in plasmonic nanoassemblies for biosensing and cell imaging

Integrating discrete plasmonic nanoparticles into assemblies can induce plasmonic coupling that produces collective plasmonic properties,which are not available for single nanoparticles.Theoretical analysis revealed that plasmonic coupling derived from assemblies could produce stronger electromagnetic field enhancement effects.Thus,plasmonic assemblies enable better performance in plasmon-based applications,such as enhanced fluorescence and Raman effects.This makes them hold great potential for trace analyte detection and nanomedicine.Herein,we focus on the recent advances in various plasmonic nanoassembles such as dimers,tetramers,and core-satellite structures,and discuss their applications in biosensing and cell imaging.The fabrication strategies for self-assembled plasmonic nanostructures are described,including top-down strategies,self-assembly methods linked by DNA,ligand,polymer,amino acid,or proteins,and chemical overgrowth methods.Thereafter,their applications in biosensor and cell imaging based on dark-field imaging,surface-enhanced Raman scattering,plasmonic circular dichroism,and fluorescence imaging are discussed.Finally,the remaining challenges and prospects are elucidated.

Au(Ⅰ)-BSA nanocomposites with assembling-induced excitation-dependent multicolor emission for dynamic cell imaging

Excitation wavelength dependent(Ex-De) luminescent materials have attracted intense attention due to their great potential in multicolor bioimaging,dynamic anti-counterfeiting,and light emitting devices.However,it remains a formidable challenge to construct an Ex-De luminescent biomaterial with green starting materials,excellent biocompatibility,good water solubility,and multiple color emission for dynamic cell imaging.In this work,nanocomposites based on the facile self-assembly strategy of bovine serum albumin(BSA) and Au(Ⅰ)-complex are rationally designed and synthesized to simultaneously present Ex-De fluorescence(429–516 nm) and decent phosphorescence(~615 nm) in a dilute aqueous solution.Combinatory analyses of spectroscopic and microscopic results reveal that the luminescent mechanism of Au(Ⅰ)-BSA nanocomposites is cluster-induced Ex-De fluorescence and metal-to-ligand charge transition(MLCT) based phosphorescence.Importantly,based on the excellent biocompatibility,water-solubility and color-tunable emission over the entire visible region(360–800 nm),the Au(Ⅰ)-BSA nanocomposites are successfully used for cell imaging with multiple and switchable colors on demand.What is more,the solid tablets of Au(Ⅰ)-BSA nanoparticles showed pressure-responsive luminescence and decent room temperature phosphorescence.This work provides an assembling-induced emission strategy for the design of water-soluble,non-cytotoxic,and color-tunable luminescent biomaterials based on the composite of protein and Au nanoparticles.

Ir(Ⅲ)-based Ratiometric Hypoxic Probe for Cell Imaging

Two new ratiometric hypoxia probes(Ir-C343 and Ir-GFP)are synthesized by covalently incorporating florescent internal standard molecules coumarin 343(C343)and green fluorescent protein(GFP)into bis[1-(9,9-dimethyl-9H-fluoren-2-yl)-isoquinoline](succinylacetone)Ir(Ⅲ)(Ir-fliq),respectively.After connecting with internal standard molecules,the Ir-fliq moiety still exhibits high sensitivity to oxygen concentration,while the fluorescence intensity of the internal standard remains relatively constant under different oxygen concentrations.As a result,a ratiometric response is realized that is only related to oxygen concentration.In addition,Ir-GFP shows more promising applications in the ratiometric hypoxia imaging of cells due to its long excitation wavelength,good water solubility,high biocompatibility,and low relative fluorescence intensity compared with the phosphorescent emitter Ir-fliq.

Fast Response Fluorescent Probe with a Large Stokes Shift for Thiophenol Detection in Water Samples and Cell Imaging

Herein,the 2,4-dinitrophenyl functional group acting as the thiophenol reactive site was introduced into a carbazole-chalcone fluorophore to synthesize probe-CCF2,which could result in a remarkable increase in fluorescence when reacting with thiophenols.The selectivity and accuracy of probe-CCF2 were investigated with thiophenols,hydrosulphide salt,aliphatic thiols,glutathione,cysteine,anions and metal cations.Probe-CCF2 exhibited a detection limit of 37 nmol/L(R^(2)=0.9951),a remarkable Stokes shift of approximately 130 nm,and a brief response time of 9 min with a remarkable increase in fluorescence of 90-fold.Probe-CCF2 was applied for thiophenol detection in water samples and imaging in living cells successfully,with high sensitivity and excellent selectivity.

Effect of Probe Lifting Height in Jumping Mode AFM for Living Cell Imaging

Atomic force microscopy(AFM)is one of the effective methods for imaging the morphological and physical properties of living cells in a near-physiological environment.However,several problems caused by the adhesion of living cells and extension of the cell membranes seriously affect the image quality during living cell imaging,hindering the study of living cells.In this work,jumping mode AFM imaging was used to image living cells at varied probe lifting heights to meet image quality requirements,and image quality related to the probe lifting height is discussed in detail.The jumping mode was divided into three parts based on the varying heights of the lifted probe,namely near-contact mode,half-jumping mode,and full-jumping mode,and the causes of their imaging drawbacks were analyzed.At an appropriate lifting height,the probe can be completely free from the influence of cell adhesion and self-excited oscillation,thus avoiding the occurrence of“trail”phenomena and invalid points in the imaging of living cells and improving the image quality.Additionally,this work provides a new approach to calculating the lateral force through the adhesion of trace and retrace scanning at a low height,which is important for studying the extension characteristics of the cell membrane.

Live cell imaging of genomic loci using dCas9-SunTag system and a bright fluorescent protein

Dear Editor,CRISPR-Cas9 （clustered regularly interspaced short palin- dromic repeats-CRISPR associated） systems have been harnessed for kinds of genome manipulation, including gene editing, transcription regulation, and chromosome loci imaging （Dominguez et al., 2016; Komor et al., 2017）. A typical engineered CRISPR-Cas9 system is composed of a Cas9 protein and a single guide RNA （sgRNA）, which could form a protein/RNA complex to recognize and cleave DNA sequence （Hsu et al., 2014; Wright et al., 2016）.

Highly green fluorescent Nb2C MXene quantum dots for Cu2+ion sensing and cell imaging

Niobium carbide MXene quantum dots(Nb2 C MQDs)derived from 2 D Nb2 CTx(MXene)are the rising-star material recently.Herein,a sulfur and nitrogen co-doped Nb2 C MQDs(S,N-MQDs)were synthesized through a hydrothermal method.The obtained Nb2 C MQDs have excellent green fluorescence with a quantum yield(QY)of 17.25%.In addition,they exhibited excitatio n-dependent photoluminescence,antiphotobleaching and dispersion stability.They emit light at 520 nm when excited at 390 nm.The Nb2 C MQDs could be successfully applied to copper ion detection with detection limit of 2μmol/L and Caco-2 cells imaging.

β-Cyclodextrin and Its Derivatives Functionalized Magnetic Nanoparticles for Targeting Delivery of Curcumin and Cell Imaging

β-Cyclodextrin （β-CD） and its derivatives functionalized magnetic nanoparticles （MNPs） with high saturated magnetism were fabricated successfully by an effective grafting method. The resultant carboxymethyl/hydroxy- propyl/sulfobutyl ether-β-CD-MNPs （CM/HP/SBE-β-CD-MNPs） nanocomposites were characterized by the TEM, FTIR, DLS, Zeta potential, XRD and VSM. In addition, the loading and release performance of the as-prepared nanocarriers for the hydrophobic anti-cancer drug curcumin was also investigated. The results revealed that the SBE-fl-CD-MNPs possessed the highest loading and release capacity in comparison with other two nanosystems. Cellular uptake and imaging suggested that the SBE-β-CD-MNPs entered into the cell, and curcumin could be suc-cessfully delivered into the cell by SBE-β-CD-MNPs nanocarrier. Moreover, cell toxicity experiments demonstrated the SBE-β-CD-MNPs were non-toxic, while curcumin loaded SBE-β-CD-MNPs showed high potential to kill the HepG2 cells. The as-prepared magnetic composites were expected to expand their potential applications in bio- medical field.

Azomethine-H as a Highly Selective Fluorescent Probe for Fe^3＋ Detection in 100% Aqueous Solution and Its Application in Living Cell Imaging

A simple assay for the detection of Fe^3＋ in water by means of fluorescence spectroscopy was developed based on a commercially available reagent, Azomethine-H（A-H）, allowing sensing trace levels of Fe^3＋ with high selectivity over other cations. A significant fluorescence quenching of A-H at 424 nm was found after its binding with Fe^3＋ in 100% aqueous solution at pH=7.0, while other physiologically relevant metal ions posed little interference. The fluorescence responses can be well described by the modified Stern-Volmer equation. A good linear relationship（Re=0.9904） was observed up to 1.6x10 5 mol/L Fe^3＋ ions. The detection limit, calculated via the 3tr IUPAC（international union of pure and applied chemistry） criteria, was 1.95x10-7 mol/L. Moreover, the colorimetric and fluorescent response of A-H to Fe^3＋ can be conveniently detected by the naked eye, providing a facile method for visual detection of Fe^3＋. The proposed method was used to determine Fe^3＋ in water samples. Moreover, inverted fluorescence microscopy imaging using human umbilical vein endothelial cells shows that A-H can be used as an effective fluorescent probe for detecting Fe^3＋ in living cells.

A selective and sensitive off–on probe for palladium and its application for living cell imaging

A new rhodamine B derivative T1 has been rationally synthesized and displayed selective Pd（Ⅱ）-amplified absorbance and fluorescence emission above 540 nm in methanol-water. Upon the addition of Pd（Ⅱ）, the spirolactam ring was unfolded and a 1：1 metal-ligand complex formed, which can be used for ＇＇naked-eyes＂ detection. In addition, fluorescence imaging experiments of Pd^（2＋） in HepG2 living cells showed its valuable application in biological systems.

Deep-learning cell imaging through Anderson localizing optical fiber

We demonstrate a deep-learning-based fiber imaging system that can transfer real-time artifact-free cell images through a meter-long Anderson localizing optical fiber.The cell samples are illuminated by an incoherent LED light source.A deep convolutional neural network is applied to the image reconstruction process.The network training uses data generated by a setup with straight fiber at room temperature(∼20°C)but can be utilized directly for high-fidelity reconstruction of cell images that are transported through fiber with a few degrees bend or fiber with segments heated up to 50°C.In addition,cell images located several millimeters away from the bare fiber end can be transported and recovered successfully without the assistance of distal optics.We provide evidence that the trained neural network is able to transfer its learning to recover images of cells featuring very different morphologies and classes that are never“seen”during the training process.

Synthesis,characterization and cell imaging properties of rare earth compounds based on hydroxamate ligand

Six binuclear rare earth compounds were synthesized through the ligand of 4-Bromo-N-hydroxy-Nmethyl-benzamide（sH_2 bha）. Compounds 1-3 are isomorphous, and compound 1 is crystallized in the monoclinic system with the P2_1/c space group. Compounds 4 and 5 are isomorphous, and compound 4 is crystallized in the triclinic system with the P-1 space group. Compound 6 is crystallized in the triclinic system with the P-1 space group. The compounds were characterized by thermogravimetric analysis（TGA） and IR spectroscopy. The fluorescence spectrum in the visible area shows characteristic peaks of Eu, Tb, and Dy compounds. The efficiency of Eu compound on the viability of PC3 cells was assessed using CCK8 assays. From the CCK8 results, ionic concentration may have a great effect on PC3 cells＇ proliferation. Eu compound shows red fluorescence in the cytoplasm of PC3 cell. As for Eu compound, it might have potential application in cell imaging technology.

Functional nucleic acid-based cell imaging and manipulation

Cells are the basic structural and functional units of organisms.Dynamic analysis and manipulation of specific components in living cells would provide valuable information for the study of related biological processes.Advances in fluorescence microscopy have allowed real-time monitoring of biological events at the molecular level.Meanwhile,the development of highperformance fluorescence probes has become a critical issue.Functional nucleic acids(FNAs)are oligonucleotides with special chemical and biological functions,and aptamers with excellent molecular recognition capability are one of the most important representatives.They have attracted extensive attention in the field of live-cell study,owing to intrinsic advantages of simple synthesis,convenient modification,low immunogenicity and high programmability.This review focuses on recent research progress in fluorescence imaging and manipulation of cells using FNAs,particularly aptamers,as the molecular tools.Finally,a summary is provided and the related challenges are discussed.

One-Pot Aqueous Synthesis of Highly Biocompatible Near Infrared CulnS2 Quantum Dots for Target Cell Imaging

In this study, we report a novel and facile autoclave strategy for synthesis of near-infrared （NIR） CulnS2 QDs by employing glutathione （GSH） as capping ligand and stabilizer in aqueous media under 100 ~C. Various experi- mental parameters including the ratio of precursors, reaction time, reaction temperature, pH effect and stability have been systematically studied. The QDs were characterized by X-ray diffraction （XRD）, transmission electron micro- scope （TEM）, and Fourier transform infrared spectroscopy （FT-IR）. The as-synthesized NIR QDs exhibited low cytotoxicity and maintained excellent cell viability even up to 100 gg/mL. After bioconjugation with Arg-Gly-Asp （RGD） peptide, the obtained CulnS2-RGD QDs have demonstrated high targeting ability with good fluorescence cell imaging performance.

Bioactivated in vivo assembly(BIVA)peptide-tetraphenylethylene(TPE)probe with controllable assembled nanostructure for cell imaging

The emergence of fluorescent light-up molecular probe,which can specifically turn on their fluorescent in the presence of stimulation factors,has open up a new opportunity to advance biosensing and bioimaging.In this work,we designed and synthesized a peptide-AIE conjugate probe for cell imaging with controlled in situ assembled nanostructures.The modular designed probe is consisted of a selfassembled peptide-tetraphenylethene(TPE)motif,a fibroblast activation protein alpha(FAP-α)responsive motif,a hydrophilic motif and a targeting motif.The probe exhibits typically turn-on fluorescence property specifically triggered by FAP-α,which is a significant overexpressed membrane protein on pancreatic tumor cells.Interestingly,the peptide modified the TPE dramatically impacts the assembled nanostructure,which can be modulated by peptide sequences.As a result,the peptide FF(PhePhe)modification of TPE as the self-assembled motif provides a suitable balance of the probe with lightup property and nanofiber assembled structure in situ.Finally,our probe could effectively detect the FAP-αon tumor cells with high specificity.Meantime,the nanofibers in situ assembled on the surface of CAFs enhanced the probe accumulation and prolonged the retention for cell imaging.We envision that this study may inspire new insights into the design of nanostructure controlled AIE light-up bio-probe.

A bestatin-based fluorescent probe for aminopeptidase N cell imaging

Aminopeptidase N （APN） is an important drug target and biomarker for various tumors. The current work characterizes a novel APN-targeted fluorescent probe （Bes-Green, 2） that manifests comparable inhibitory activity with Bestatin. This probe has capacity of tightly binding to the APN for imaging endogenous APN in living human ovarian clear cell carcinoma cells （ES-2） and has potential application in biological study of cellular APN.