Understanding host-graft crosstalk for predicting the outcome of stem cell transplantation

Mesenchymal stromal cells(MSCs)hold great promise for tissue regeneration in debilitating disorders.Despite reported improvements,the short-term outcomes of MSC transplantation,which is possibly linked to poor cell survival,demand extensive investigation.Disease-associated stress microenvironments further complicate outcomes.This debate underscores the need for a deeper understanding of the phenotypes of transplanted MSCs and their environment-induced fluctuations.Additionally,questions arise about how to predict,track,and comprehend cell fate post-transplantation.In vivo cellular imaging has emerged as a critical requirement for both short-and long-term safety and efficacy studies.However,translating preclinical imaging methods to clinical settings remains challenging.The fate and function of transplanted cells within the host environment present intricate challenges,including MSC engraftment,variability,and inconsistencies between preclinical and clinical data.The study explored the impact of high glucose concentrations on MSC survival in diabetic environments,emphasizing mitochondrial factors.Preserving these factors may enhance MSC survival,suggesting potential strategies involving genetic modification,biomaterials,and nanoparticles.Understanding stressors in diabetic patients is crucial for predicting the effects of MSC-based therapies.These multifaceted challenges call for a holistic approach involving the incorporation of large-scale data,computational disease modeling,and possibly artificial intelligence to enable deterministic insights.

Cytotoxicity and cellular imaging of quantum dots protected by polyelectrolyte

The nanocomposites of poly-diallyldimethylammonium chloride (PDADMAC) and CdTe quantum dots (QDs) (i.e. QDs-PDADMAC nanocomposites) have been prepared based on electrostatic interaction and their fluorescence stability in aqueous solution has been investigated. MTT method (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide method) was used to study their cytotoxicity and A549 lung cancer cell as a model cell was also used to evaluate their cellular imaging. It was shown that the fluorescence stability of QDsPDADMAC nanocomposites was much better than that of bare QDs both in aqueous solution and cell. Meanwhile, QDs-PDADMAC nanocomposites display very low cytotoxicity in the low concentrations and better staining ability compared with QDs. QDs-PDADMAC nanocomposites will have great advantage on the cell analysis detection and imaging.

In situ visualization of the cellular uptake and sub-cellular distribution of mussel oligosaccharides

Unlike chemosynthetic drugs designed for specific molecular and disease targets,active small-molecule natural products typically have a wide range of bioactivities and multiple targets,necessitating extensive screening and development.To address this issue,we propose a strategy for the direct in situ microdynamic examination of potential drug candidates to rapidly identify their effects and mechanisms of action.As a proof-of-concept,we investigated the behavior of mussel oligosaccharide(MOS-1)by tracking the subcellular dynamics of fluorescently labeled MOS-1 in cultured cells.We recorded the entire dynamic process of the localization of fluorescein isothiocyanate(FITC)-MOS-1 to the lysosomes and visualized the distribution of the drug within the cell.Remarkably,lysosomes containing FITC-MOS-1 actively recruited lipid droplets,leading to fusion events and increased cellular lipid consumption.These drug behaviors confirmed MOS-1 is a candidate for the treatment of lipid-related diseases.Furthermore,in a high-fat HepG2 cell model and in high-fat diet-fed apolipoprotein E(ApoE)^(-/-)mice,MOS-1 significantly promoted triglyceride degradation,reduced lipid droplet accumulation,lowered serum triglyceride levels,and mitigated liver damage and steatosis.Overall,our work supports the prioritization of in situ visual monitoring of drug location and distribution in subcellular compartments during the drug development phase,as this methodology contributes to the rapid identification of drug indications.Collectively,this methodology is significant for the screening and development of selective small-molecule drugs,and is expected to expedite the identification of candidate molecules with medicinal effects.

Photoacoustic imaging of prostate cancer

Photoacoustic imaging(PAI),also known as optoacoustic imaging,is a rapidly growing imaging modality with potential in medical diagnosis and therapy monitoring.This paper focuses on the techniques of prostate PAI and its potential applications in prostate cancer detection.Transurethral light delivery combined with transrectal ultrasound detection overcomes light scattering in the surrounding tissue and provides optimal photoacoustic signals while minimizing invasiveness.While label-free PAI based on endogenous contrast has promising potential for prostate cancer detection,exogenous contrast agents can further enhance the sensitivity and speci¯city of prostate cancer PAI.Further in vivo studies are required in order to achieve the translation of prostate PAI to clinical implementation.The minimal invasiveness,relatively low cost,high speci¯city and sensitivity,and real-time imaging capability are valuable advantages of PAI that may improve the current prostate cancer management in clinic.

Water-ultrastable perovskite CsPbBr_(3)nanocrystals for fluorescence-enhanced cellular imaging

Metal halide perovskites have attracted much attention in biomedicine because of their excellent fluorescence energy conversion properties;however,poor water-stability and cytotoxicity limit its applications as a biomedical tracer,especially in cellular imaging.Herein,water-ultrastable perovskites C sPbBr_(3):Cs_(4)PbBr_(6)nanocrystals(NCs)encapsulated in chitosan are fabricated successfully using a water-triggered method.The as-synthesized CsPbBr_(3):Cs_(4)PbBr_(6)@CS(chitosan,CS)nanoparticles in water display enhanced fluorescence emission for 35 days.Further,the viability of glioma cells(U87 cells)incubated with different concentrations of CsPbBr_(3):Cs_(4)PbBr_(6)@CS nanoparticles(0-20μg·ml^(-1))for24 h is found to be higher than 90%.In artificial body fluid,analyses using laser confocal microscopy,the standard Cell Counting Kit-8(CCK-8)method,and flow cytometry demonstrated the good water ultrastability and high biocompatibility performance of CsPbBr_(3):Cs_(4)PbBr_(6)@CS nanoparticles in cellular imaging.Overall,the water-ultrastable halide perovskites support promising perspectives in biological cell tracing and intelligent medical technology.

Tracking of Labelled Stem Cells Using Molecular MR Imaging in a Mouse Burn Model <i>in Vivo</i>as an Approach to Regenerative Medicine

Therapies based on stem cell transplants offer significant potential in the field of regenerative medicine. Monitoring the fate of the transplanted stem cells in a timely manner is considered one of the main limitations for long-standing success of stem cell transplants. Imaging methods that visualize and track stem cells in vivo non-invasively in real time are helpful towards the development of successful cell transplantation techniques. Novel molecular imaging methods which are non-invasive particularly such as MRI have been of great recent interest. Hence, mouse models which are of clinical relevance have been studied by injecting contrast agents used for labelling cells such as super-paramagnetic iron-oxide (SPIO) nanoparticles for cellular imaging. The MR techniques which can be used to generate positive contrast images have been of much relevance recently for tracking of the labelled cells. Particularly when the off-resonance region in the vicinity of the labeled cells is selectively excited while suppressing the signals from the non-labeled regions by the method of spectral dephasing. Thus, tracking of magnetically labelled cells employing positive contrast in vivo MR imaging methods in a burn mouse model in a non-invasive way has been the scope of this study. The consequences have direct implications for monitoring labeled stem cells at some stage in wound healing. We suggest that our approach can be used in clinical trials in molecular and regenerative medicine.

Nano-Graphene Oxide for Cellular Imaging and Drug Delivery

Two-dimensional graphene offers interesting electronic,thermal,and mechanical properties that are currently being explored for advanced electronics,membranes,and composites.Here we synthesize and explore the biological applications of nano-graphene oxide(NGO),i.e.,single-layer graphene oxide sheets down to a few nanometers in lateral width.We develop functionalization chemistry in order to impart solubility and compatibility of NGO in biological environments.We obtain size separated pegylated NGO sheets that are soluble in buffers and serum without agglomeration.The NGO sheets are found to be photoluminescent in the visible and infrared regions.The intrinsic photoluminescence(PL)of NGO is used for live cell imaging in the near-infrared(NIR)with little background.We found that simple physisorption viaπ-stacking can be used for loading doxorubicin,a widely used cancer drug onto NGO functionalized with antibody for selective killing of cancer cells in vitro.Owing to its small size,intrinsic optical properties,large specifi c surface area,low cost,and useful non-covalent interactions with aromatic drug molecules,NGO is a promising new material for biological and medical applications.

Photoluminescent two-dimensional SiC quantum dots for cellular imaging and transport

Two-dimensional （2D） ultrathin SiC has received intense attention due to its broad band gap and resistance to large mechanical deformation and external chemical corrosion. However, the synthesis and application of ultrasmall 2D SiC quantum dots （QDs） has not been explored. Herein, we synthesize a type of monolayered 2D SiC QDs with advanced photoluminescence （PL） properties via a facile hydrothermal route. Their average size and thickness can be easily adjusted by altering the reaction time. The ultrasmall 2D SiC QDs exhibit a long fluorescence lifetime of 2.59 ps due to efficient quantum confinement. The applications of SiC QDs are demonstrated through labeling A549, HeLa, and NHDF cells and delivering agents for intracellular low-abundant microRNA （miRNA） detection. This advance in preparing photoluminescent SiC QDs is of great significance for broadening their potential in biomedical and optical applications.

Versatile Graphene-Isolated AuAg-Nanocrystal for Multiphase Analysis and Multimodal Cellular Raman Imaging

Surface-enhanced Raman spectroscopy(SERS)-based bioanalytical technique involves the interaction of SERS-active substrate with complex environment,which has aroused intensive research interests.Compared to the commonly used Au SERS substrates,Ag nanocrystals have larger optical absorption cross section and acceptable price,but they possess poor oxidation resistance and potential biotoxicity,and the occurrence of unnecessary chemical reactions is inevitable due to the direct contact with probe molecules.Herein,we report a graphene-isolated AuAg nanocrystal(GIAAN)with the SERS-active AuAg core confined in a nanospace of few-layer graphene shell,which possesses unique Raman peaks,high SERS activity,excellent stability,superior fluorescence quenching performance and good biocompatibility.Based on the limited solubility of GIAAN in water and organic solvents,it is able to spontaneously generate interfacial self-assembled GIAAN(ISA-GIAAN)film at immiscible two-phase interfaces without any inducer,and multiphase Raman analysis of both water-and lipid-soluble drug model molecules is further achieved.Moreover,the GIAAN is further non-covalently functionalized with polyoxyethylenestearyl ether(C18-PEG)to acquire GIAAN@PEG with good water-solubility for SERS quantitative analysis in homogeneous system and multimodal Raman imaging of MCF-7 cells.We expect the versatile GIAAN holds great potential to monitor drug metabolism and guide intended drug delivery in clinic trials.

Facile Preparation and Cellular Imaging of Photoluminescent Carbogenic Nanoparticles Derived from Defoliations

In the past two decades, photoluminescent semiconductor quantum dots（QDs） have received intensive attention for a variety of promising properties and applications, especially for their potential application in cellular imagingE. QDs with high quantum yield have been prepared based on cad mium（zinc） selenide（sulfide） and related coreshell compo sites. However, the release of Cd2＋, S2 and Se2 ions in evitably causes serious health and environmental concerns. Therefore, many efforts have been devoted to developing be nign alternatives with enhanced photoluminescence, such as silicon nanoparticles and nanowires. Carbonbased nanomaterials, including carbon nano tubes（CNTs） and carbogenic nanoparticles（CNPs）, represent an exciting new type of alternative to the aforementioned QDs with high quantum yield. CNPs are superior to QDs in chemi cally inertness, biocompatibility and photostability. After the report on the photoluminescence of carbon dots prepared by laser ablation with graphite as carbon sourcetill, several strate gies have been developed for the preparation of luminescent CNPs. For instance, luminescent CNPs were prepared by Liu et al.021 with candle soot via oxidative acid treatment, and the resulting CNPs with different emission colors were isolated by means of electrophoretic separation. Hu et al. employed an improved onestep approach for the synthesis of luminescent CNPs by laser irradiating a suspension of carbon materials in organic solvents of diamineterminated oligomeric poly（ethylene glycol）（PEG1500N）. More recently, luminescent carbogenic dots have been obtained by Peng and Travas via surface passivation of carbogenic dots in an aqueous solution with carbohydrates as the starting materials. Carbogenic nano particlesloaded magnesiumaluminophosphate solid phosphors.

Emerging applications of near-infrared fluorescent metal nanoclusters for biological imaging

Fluorescent metal nanoclusters（MNCs） have recently emerged as a novel kind of promising fluorescent probes for biological imaging because of their ultrasmall core size（〈2 nm）, strong photoluminescence,facile availability and good biocompatibility. In this review, we provide an update on recent advances in the development of near infrared（NIR）-emitting MNCs in terms of synthesis strategies and bioimaging applications. We mainly focus on the utilization of NIR-emitting MNCs（including Au, Ag, Cu and alloy NCs） either as single modal imaging（fluorescence intensity-based imaging, fluorescence lifetime imaging, two-photon imaging） probes or as multimodal imaging（such as NIR fluorescence/X-ray computed tomography/magnetic resonance imaging, NIR fluorescence/photoacoustic imaging/magnetic resonance imaging, NIR fluorescence/single photon emission computed tomography） probes in biological cells and tissues. Finally, we give a brief outlook on the future challenges and prospects of developing NIR-emitting MNCs for bioimaging.

Highly photostable nanogels for fluorescence-based theranostics

A novel photo-crosslinkable nanogel is prepared from a biodegradable polymer template with intrinsic photoluminescence and high photostability.The fluorescent nanogels display excellent biodegradability and cytocompatibility owed to the facile synthesis scheme involving a solvent-and surfactant-free onepot reaction,derived entirely from biocompatible monomers citric acid,maleic acid,L-cysteine,and poly(ethylene glycol).The resultant nanogels are less than 200 nm in diameter with a narrow size distribution and monodispersity,and demonstrate long-term structural stability in biological buffer for two weeks.To gauge potential in theranostic applications,the fluorescent nanogels were surface functionalized with biologically active RGD peptides and encapsulated with active anti-cancer drug Doxorubicin,resulting in a pH-responsive controlled drug release in acidic pH resembling tumor environments.The strong fluorescence of the nanogels enabled tracking of targeted drug delivery,showing that drug-loaded nanogels homed into the cytoplasmic regions of prostate cancer cells to significantly induce cell death.These photo-crosslinkable and biodegradable nanogels pose as a strong candidate for theranostic medicine,demonstrating versatile functionalization,high stability in biological buffers,and capacity for real-time fluorescence-based monitoring of targeted drug delivery.

Framework Nucleic Acids for Cell Imaging and Therapy

Over the past decade,structural DNA nanotechnology has been well developed to be a promising and powerful technique to generate various nanostructures with programmability,spatial organization and biocompatibi-lity.With the advent of computer-aided tools,framework nucleic acids have been employed in a series of biomedical applications,ranging from biosensing,bioimaging,diagnosis,to therapeutics.In this review,we summarized recent advances in the construction of precisely assembled DNA nanostructures,and DNA-engineered biomimetics.We also outlined the challenges and opportunities for the translational applications of framework nucleic acids.

PEGylated BODIPY assembling fluorescent nanoparticles for photodynamic therapy

Two amphiphilic macromolecules were synthesized from polyethylene glycol monomethylether（PEG）and borondipyrrolmethene（BODIPY） via one-pot multicomponent Passerini reaction,and they could self-assemble into stable nanoparticles（NPs） in aqueous media.The optical properties,including fluorescence resonance energy transfer（FRET） were studied in detail.The obtained NPs possess good cytocompatibility,and could be used for living cell imaging and effective photodynamic therapy（PDT）.These results shed light on one-pot synthesis of PEGylated fluorescent nanoparticles via multicomponent reaction for biomedical application.

High-contrast and real-time visualization of membrane proteins in live cells with malachite green-based fluorogenic probes

Imaging dynamics of membrane proteins of live cells in a wash-free and real-time manner has been a challenging task. Herein, we report unprecedented applications of malachite green(MG), an organic dye widely used in pigment industry, as a switchable fluorophore to monitor membrane enzymes or noncatalytic proteins in live cells. Conformationally flexible MG is non-fluorescent in aqueous solution, yet covalent binding with endogenous proteins of cells significantly enhances its fluorescence at 670 nm by restricting flexibility of dye. Integrating a phosphate-caged quinone methide precursor with MG yielded a covalent labeling fluorogenic probe, allowing real-time imaging of membrane alkaline phosphatase(ALP,a model catalytic protein) activity in live cells with over 100-fold enhancement of fluorescence intensity.Moreover, MG is also applicable to image non-catalytic protein by conjugation with protein-specific ligand. A fluorogenic probe consisted of c-RGDf K peptide and MG proved to be compatible with wash-free and real-time visualization of non-catalytic integrin α_(v)β_(3) in live cells with high contrast.

Tn5-FISH,a novel cytogenetic method to image chromatin interactions with sub-kilobase resolution

There is an increasing interest in understanding how three-dimensional(3D)organization of the genome is regulated.Different strategies have been employed to identify genome-wide chromatin interactions.However,due to current limitations in resolving genomic contacts,visualization and validation of these genomic loci with sub-kilobase resolution remain unsolved to date.Here,we describe Tn5 transposase-based Fluorescencein situhybridization(Tn5-FISH),a PCR-based,cost-effective imaging method,which can co-localize the genomic loci with sub-kilobase resolution,dissect genome architecture,and verify chromatin interactions detected by chromatin configuration capture(3C)-derived methods.To validate this method,short-range interactions in keratin-encoding gene(KRT)locus in topologically associated domain(TAD)were imaged by triple-color Tn5-FISH,indicating that Tn5-FISH is very useful to verify short-range chromatin interactions inside the contact domain and TAD.Therefore,Tn5-FISH can be a powerful molecular tool for the clinical detection of cytogenetic changes in numerous genetic diseases such as cancers.

Fluorescent Cadmium Sulfide Supraparticles: One-Step In situ Self-Assembly Fabrication and Cationic Surfactant Chain Length-Dependent Mitochondria Targeting Capacity

The exploration of novel fluorescent tools for subcellular analysis is of great importance for both chemical biology and biomedicine.Herein,we present an in situ self-assembly strategy for fabricating fluorescent and monodisperse Cd S supraparticles(SPs),which are subsequently employed for mitochondria targeting applications.Using bovine serum albumin and linear chain cationic surfactants as templates and electrostatic modulators,respectively,Cd S SPs can be well fabricated by the proposed one-step self-assembly approach in aqueous medium.In addition to high stability,favorable biocompatibility,as well as decent quantum efficiency,the as-prepared SPs have mitochondria targeting capacity due to their cationic surfactant modification.Interestingly,the localization capacity is positively correlated with the length of the cationic surfactant molecules.As the carbon chains of the cationic surfactant molecules enhance from 10 to 16 atoms,the colocalization efficiencies are correspondingly increased from 81 to 84%.

A Monochromophoric Approach to Succinct Ratiometric Fluorescent Probes without Probe-Product Crosstalk

Ratiometric probes facilitate quantitative studies via self-calibration and are cherished for bioimaging.Often,a small probe-product spectral separation leads to crosstalk,but the rational development of ratiometric probes with zero probe-product crosstalk remains challenging.Harnessing the recent progress on photophysical modulation of xanthenoid fluorochromes,we propose a powerful and versatile probe design principle,that is,“bridging-group modification,”and developed totalROX,a robust probe for monitoring the total cellular oxidative capacity.