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.

Application of Image Fusion Methods to Cell Imaging Processing

Aim To fuse the fluorescence image and transmission image of a cell into a single image containing more information than any of the individual image. Methods Image fusion technology was applied to biological cell imaging processing. It could match the images and improve the confidence and spatial resolution of the images. Using two algorithms, double thresholds algorithm and denoising algorithm based on wavelet transform,the fluorescence image and transmission image of a Cell were merged into a composite image. Results and Conclusion The position of fluorescence and the structure of cell can be displyed in the composite image. The signal-to-noise ratio of the exultant image is improved to a large extent. The algorithms are not only useful to investigate the fluorescence and transmission images, but also suitable to observing two or more fluoascent label proes in a single cell.

Fluorine-doped carbon quantum dots with deep-red emission for hypochlorite determination and cancer cell imaging

As a type of new carbon-based nanomaterials,carbon dots(CDs)possess exceptional optical properties,making them highly desirable for use in fluorescent sensors.However,the CDs with deep-red(DR)or near-infrared(NIR)emission have rarely been reported.In this work,we prepared deep-red emissive fluorine-doped carbon quantum dots(F-CDs)by introducing a precursor simultaneously containing fluorine and amidogen.The synergistic effect of nitrogen doping and D-π-A pattern production contributed to the maximum emission of F-CDs at 636 nm with an absolute quantum yield of 36.00%±0.68%.Moreover,we designed an F-CDs-based fluorescence assay to determine the content of hypochlorite(ClO^(-)),with a limit of detection(LOD)as low as 15.4 nmol/L,indicating the high sensitivity of F-CDs to ClO^(-).In real samples,the F-CDs-based fluorescent sensor exhibited excellent sensitivity and selectivity in the detection of ClO^(-),with an error below 2%,suggesting their great potential in daily life.In cancer cell imaging,the F-CDs not only demonstrated high sensitivity to ClO^(-)but also exhibited excellent mitochondria targeting,as evidenced by the high Pearson's correlation coefficient(PCC)of 0.93 in colocalization analysis.The work presented here suggests the great potential of replacing commercial dyes with F-CDs for highly specific mitochondria labeling and cell imaging.

Luminescent terphen[3]arene sulfate-activated FRET assemblies for cell imaging

Multicharged supramolecular assemblies based on luminescent macrocycle play an important role in extending their optical properties and functions.Herein,we reported macrocyclic supramolecular assemblies based on luminescent terphen[3]arene sulfate(TP[3]AS)and tetraphenylethylene pyridinium(TPE-4Py)through electrostatic interactions,host-guest encapsulation andπ-πstacking interactions.F?rster resonance energy transfer(FRET)process from TP[3]AS to TPE-4Py was achieved with the energy transfer efficiency of 99.9%,accompanied by TPE-4Py fluorescence emission bathochromic shifted of 15 nm and enhanced by 1.68 times in PBS solution.In contrast,other non-luminescent sulfato-β-cyclodextrin and sulfobutylether-β-cyclodextrin only can enhance the fluorescence intensity of TPE-4Py without bathochromic shift.Due to the strong fluorescence and good stability of TPE-4Py@TP[3]AS,it can be used for optical imaging in living cells,which provided an effective approach for the construction of assembling-confined luminescent biomaterials.

Multiplexed stimulated emission depletion nanoscopy(mSTED)for 5-color live-cell long-term imaging of organelle interactome

Stimulated emission depletion microscopy(STED)holds great potential in biological science applications,especially in studying nanoscale subcellular structures.However,multi-color STED imaging in live-cell remains challenging due to the limited excitation wavelengths and large amount of laser radiation.Here,we develop a multiplexed live-cell STED method to observe more structures simultaneously with limited photo-bleaching and photo-cytotoxicity.By separating live-cell fluorescent probes with similar spectral properties using phasor analysis,our method enables five-color live-cell STED imaging and reveals long-term interactions between different subcellular structures.The results here provide an avenue for understanding the complex and delicate interactome of subcellular structures in live-cell.

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.

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.

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.

Recent advances in optical techniques for dynamically probing cellular mechanobiology

Cellular mechanotransduction characterized by the transformation of mechanical stimuli into biochemical signals,represents a pivotal and complex process underpinning a multitude of cellular functionalities.This process is integral to diverse biological phenomena,including embryonic development,cell migration,tissue regeneration,and disease pathology,particularly in the context of cancer metastasis and cardiovascular diseases.Despite the profound biological and clinical significance of mechanotransduction,our understanding of this complex process remains incomplete.The recent development of advanced optical techniques enables in-situ force measurement and subcellular manipulation from the outer cell membrane to the organelles inside a cell.In this review,we delved into the current state-of-the-art techniques utilized to probe cellular mechanobiology,their principles,applications,and limitations.We mainly examined optical methodologies to quantitatively measure the mechanical properties of cells during intracellular transport,cell adhesion,and migration.We provided an introductory overview of various conventional and optical-based techniques for probing cellular mechanics.These techniques have provided into the dynamics of mechanobiology,their potential to unravel mechanistic intricacies and implications for therapeutic intervention.

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.

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）.

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.