Journal of Nanobiotechnology

Interest in mesenchymal stem cell derived extracellular vesicles (MSC-EVs) as therapeutic agents has dramatically increased over the last decade. Preclinical studies show that MSC-EVs have anti-apoptotic and neuroprotective effects, boost wound healing, and improve the integration of allogeneic grafts through immunomodulation. Current approaches to the characterization and quality control of EV-based therapeutics include particle tracking techniques, Western blotting, and advanced cytometry, but standardized methods are lacking. In this study, we established and verified quartz crystal microbalance (QCM) as highly sensitive label-free immunosensing technique for characterizing clinically approved umbilical cord MSC-EVs enriched by tangential flow filtration and ultracentrifugation. Using QCM in conjunction with common characterization methods, we were able to specifically detect EVs via EV (CD9, CD63, CD81) and MSC (CD44, CD49e, CD73) markers and gauge their prevalence. Additionally, we characterized the topography and elasticity of these EVs by atomic force microscopy (AFM), enabling us to distinguish between EVs and non-vesicular particles (NVPs) in a therapeutic formulation. This measurement modality makes it possible to identify EV sub-fractions, discriminate between EVs and NVPs, and to characterize EV surface proteins, all with minimal sample preparation and using label-free measurement devices with low barriers of entry for labs looking to widen their spectrum of characterization techniques. Our combination of QCM with impedance measurement (QCM-I) and AFM measurements provides a robust multi-marker approach to the characterization of clinically approved EV formulations and opens the door to improved quality control.

Graphene oxide (GO) holds great potential for biomedical applications, however fundamental understanding of the way it interacts with biological systems is still lacking even though it is essential for successful clinical translation. In this study, we exploit intrinsic fluorescent properties of thin GO sheets to establish the relationship between lateral dimensions of the material, its cellular uptake mechanisms and intracellular fate over time. Label-free GO with distinct lateral dimensions, small (s-GO) and ultra-small (us-GO) were thoroughly characterised both in water and in biologically relevant cell culture medium. Interactions of the material with a range of non-phagocytic mammalian cell lines (BEAS-2B, NIH/3T3, HaCaT, 293T) were studied using a combination of complementary analytical techniques (confocal microscopy, flow cytometry and TEM). The uptake mechanism was initially interrogated using a range of pharmaceutical inhibitors and validated using polystyrene beads of different diameters (0.1 and 1 m). Subsequently, RNA-Seq was used to follow the changes in the uptake mechanism used to internalize s-GO flakes over time. Regardless of lateral dimensions, both types of GO were found to interact with the plasma membrane and to be internalized by a panel of cell lines studied. However, s-GO was internalized mainly via macropinocytosis while us-GO was mainly internalized via clathrin- and caveolae-mediated endocytosis. Importantly, we report the shift from macropinocytosis to clathrin-dependent endocytosis in the uptake of s-GO at 24 h, mediated by upregulation of mTORC1/2 pathway. Finally, we show that both s-GO and us-GO terminate in lysosomal compartments for up to 48 h. Our results offer an insight into the mechanism of interaction of GO with non-phagocytic cell lines over time that can be exploited for the design of biomedically-applicable 2D transport systems.

High-sensitivity flow cytometry (FC) allows multiparametric analysis of nanoparticles (NPs) and extracellular vesicles (EVs). With new instruments available, studies that evaluate their performance using the same materials in a controlled environment are required. Here, we performed a comparative study to investigate the capabilities of three flow cytometers, namely the NanoFCM (NF), BD Influx (IF) and CytoFLEX LX (CF). Firstly, we analyzed a mixed population of silica NPs (SiNPs, 68, 91, 114 and 155 nm) by using light-scatter based detection thresholds (SSC, FSC, VSSC) across a concentration range from 106 to 109 particles/mL. Next, we analyzed fluorescent recombinant EVs (rEVs) by comparing light-scatter based thresholding (488 nm SSC available for all platforms), the combination of SSC thresholding with a fluorescent gate, and fluorescent thresholding for their qualitative and quantitative analysis. We here provide the strengths and limitations for each platform regarding the analysis of differently sized NPs at different sample concentrations.

The majority of studies on extracellular vesicles (EVs) focused on samples isolated from liquid matrices, such as cell culture media and blood, due to their accessibility. However, recent research highlights the emerging roles of EVs derived from solid tissues, including the brain, muscles and tumors. Investigating EVs from the extracellular matrix of solid tissues offers insights into their microenvironment and potential biological influences on surrounding cells. This study presents a universal method for comparing EV-enriched samples from solid (human skeletal muscle biopsy) and liquid (human plasma) matrices, addressing technical challenges and minimizing biases in separation techniques. By employing optimized protocols and advanced analytical techniques, the study reveals differences in biomolecular composition, nanomechanical properties, particle yield, size distribution, and colloidal stability between human skeletal muscle and plasma EVs. Understanding these distinctions may contribute to the development of novel diagnostic assays for muscular pathologies and shed light on the roles of EVs in diverse tissue environments.

Accurate discrimination of extracellular vesicles (EVs) from non-vesicular nanoparticles and robust phenotyping of individual EVs directly within complex biofluids are essential to advance understanding of EV biology and to realize their potential as biomarkers and therapeutic agents. Conventional flow cytometers, originally designed for cellular analysis, lack the scatter and fluorescence sensitivity, dynamic range, and event-rate control required for quantitative characterization of nanoscale vesicles and are particularly susceptible to coincident (swarm) detection. Dedicated nanoparticle flow cytometers have been developed to address these limitations, and here we systematically evaluate the suitability of the CytoFLEX Nano (Beckman Coulter) for EV analysis. Using a series of calibration beads of different materials, fluorescent liposomes, and EVs isolated from peritoneal fluid and cell culture medium, we assess size-detection thresholds, scatter and fluorescence sensitivity, dynamic range, and volumetric counting accuracy. These data provide practical guidance for implementing nanoscale flow cytometry in EV research and support the informed adoption of dedicated nanoparticle cytometers in studies adhering to current EV reporting standards.

Traditional crop delivery methods, such as foliar spray and soil application, face significant limitations, including nutrient loss, environmental impacts, and low delivery efficiency. Recent advances in nanomaterials have offered novel molecular delivery platforms, but challenges such as synthesis complexity, long-term stability, and compliance with rigorous biosafety regulations persist. To provide a simpler, lower-cost, and safer alternative, we developed a polyvinyl alcohol (PVA)-based microneedle (MN) delivery system that can be precisely applied to various plant tissues (e.g., stem, lateral branch, or petiole), which demonstrates high delivery efficiency compared to the conventional methods (3.5x higher tissue accumulation) while reducing application dose (>90% less). This MN system facilitates the delivery of diverse small molecules, ranging from fluorescent dyes, growth promoters, to antiviral hormones, into plant tissues, on the other hand showing limited wounding stress to the plant. By applying fluorescent dye-loaded MNs onto tomato stems, we demonstrated effective molecular diffusion through vascular tissues. Additionally, MNs loaded with gibberellic acid (GA3) enhanced stem and branch growth in tomatoes and restored the lateral flowering phenotype in Arabidopsis ft-10 mutants, with significant upregulation of GA receptor gene expression. Lastly, salicylic acid (SA) injections with MNs induced resistance to tomato spotted wilt virus (TSWV) in Nicotiana benthamiana, comparable to conventional spray and infiltration-based approaches. This easily fabricated and cost-effective MN system offers a promising tool for precision agriculture, enhancing plant health and productivity while significantly reducing the use of agrochemicals.

Exosomes are nanovesicles ([~]30-150 nm diameters) released via an endocytic pathway in almost all mammalian cell types. Exosomes are composed of a lipid bilayer membrane that encloses RNA, miRNA, proteins and DNA. This manuscript unravels how exosome cargo is collected by a highly precise process delineating two separate mRNA transcript entities encoding cytoplasmic and nuclear proteins separately. Ultracentrifuge isolated exosomes were directly converted into cDNA (Exo-cDNA), by a method developed in our laboratory. Cellular RNA was extracted from each cell line and cDNA was prepared (Cell-cDNA). We amplified mRNA transcripts translating cytoplasmic proteins CD10 and CXCR4 and mRNA transcripts translating nuclear proteins such as proliferating cell nuclear antigen (PCNA), CREB-BP, activation induced cytidine deaminase (AID), and terminal deoxynucleotidyl transferase (TdT). We amplified all four different mRNA transcripts (PCNA, CREB-BP, AID, and TdT) from cellular cDNA but none from exosomal cDNA (Exo-cDNA). These findings suggest that exosomes carry mRNA transcripts encoding cytoplasmic proteins only but mRNA transcripts encoding nuclear proteins could not be detected. This important observation could prove to be crucial for the exosome research community since it sheds light on one of the limitations relating to the use of exosomes as biomarkers in cancer biology and other diseases. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=118 SRC="FIGDIR/small/227223v2_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@102c790org.highwire.dtl.DTLVardef@17bcabdorg.highwire.dtl.DTLVardef@3b5ac0org.highwire.dtl.DTLVardef@c303c8_HPS_FORMAT_FIGEXP M_FIG C_FIG

Fluorescent nanodiamonds have exceptional optical properties and are highly biocompatible, which allows to use them as labels for long-term tracking of the cells. The research fields that make use of this application of nanodiamonds include stem cell biology and cancer biology, where quiescent and differentiating cells can be traced in vitro and in vivo. However, these studies focus on using nanodiamonds as simple labels, whereas they can serve as highly sensitive intracellular sensors for free radical species. In this study, we aimed to bring the two approaches together and to assess the free radical production in the cells over the course of their differentiation. We report on the successful enterocytic differentiation of HT-29 colon adenocarcinoma cells, pre-loaded with fluorescent nanodiamonds. The cells were cultured in butyrate-free or butyrate-supplemented medium for 13 days. Butyrate-treated cells developed the morphological and molecular traits, characteristic for normal enterocytes. Fluorescent nanodiamonds did not have a negative effect on the process of differentiation. Moreover, the particles could be found in the cytoplasm of both undifferentiated and re-differentiated cells even after 13 days of culture. The internalized nanodiamonds were used to assess the free radical load in the undifferentiated and re-differentiated HT-29 cells at different stages of the experiment. Consistently with previous findings, re-differentiated HT-29 cells showed higher free radical load than undifferentiated ones.

Extracellular vesicles (EVs) allow the exchange of protein, lipids and genetic material for communication between cells. We developed a method to track protein exchange between cells via EVs, using stable isotope labelling of amino acids in cell culture (SILAC). We compared EV isolation methods: ultracentrifugation and size exclusion chromatography (SEC) and undertook characterisation through nanoparticle tracking analysis (NTA), then optimised the requirement (0-10%) for foetal calf serum (FCS) and EV application concentration (6.5 million-200 EVs/cell seeded). We employed heavy amino acids L-Arg-HCl and L-Lys-2HCl to label donor cells and subsequent EV proteins. Unlabelled recipient cells were treated for 12 hours with EVs, at various concentrations. Mass spectrometry proteomics was used to assess uptake of heavy labelled EVs into recipient cells. A labelling efficiency of 62% was achieved. There was no relationship between the number of EVs applied to cells and the number of heavy proteins detected in the recipient cells. Pathway analysis indicated an inflammatory effect of applying EVs to cells, but the potential cause of this was unclear. We identified transferred protein cargo from EVs in recipient cells. Further optimisation of this method is still necessary.

The application of nanotechnology in plant science is unlocking innovative approaches to enhance nutrient use efficiency in crops, particularly through foliar fertilization. This study demonstrates that colloidally stable, pH-responsive polyacrylic acid (PAA)-coated manganese dioxide (MnO2) nanoparticles (nPAA-MnO2) can be designed to significantly restore key metabolic functionalities in manganese (Mn)-deficient barley (Hordeum vulgare) within a few days. Using a combination of advanced bioimaging techniques - including confocal laser scanning microscopy (CLSM), laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), and X-ray nano-computed tomography (nano-CT), we mapped the uptake and distribution pathways of nPAA-MnO2 compared to ionic Mn. While soluble Mn2+ ions primarily enter through hydrophilic cuticular pores, nPAA-MnO2 penetrates leaves via stomata, facilitated by the application of an organosilicone surfactant and glycerol to enhance wetting and hydraulic activation of stomatal pores. Within a few hours, nPAA-MnO2 accumulated in the sub-stomatal cavity and mesophyll apoplast, gradually releasing bioavailable Mn ions in the acidic apoplast environment. Moreover, labeling experiments with tracer ions revealed nPAA-MnO2 hot-spots around the vascular bundles and a limited but significant basipetal translocation of intact nanoparticles out of the foliar application zone, a pivotal step towards converting immobile nutrients such as Mn into mobile ones. Importantly, and unlike ionic Mn solutions, nPAA-MnO2 could be applied at high doses without causing leaf scorching and cytotoxicity, paving the way for more sustainable and efficient foliar fertilization practices. These novel aspects of nanoparticle uptake, translocation, and assimilation underscores the potential of nanotechnology to address nutrient mobility challenges in agriculture, representing an important contribution to the green transition of modern crop production.

BackgroundMalignant melanoma is a highly aggressive cancer that presents significant treatment challenges, especially in metastatic stages where conventional therapies often fail due to resistance. Targeting the tumors supportive environment rather than the cancer cells themselves offers a promising strategy. The tumor endothelial marker 8 (TEM8), also known as anthrax toxin receptor 1, is overexpressed in tumor neovasculature endothelial cells and their precursors, making it an attractive therapeutic target. This study introduces PA17, a protein ligand derived from the anthrax toxin binding domain and specifically engineered to target TEM8, aiming to enhance the precision and effectiveness of nanomedicine. ResultsRecombinant and purified PA17 ligand protein exhibited high affinity for TEM8 both in vitro and in vivo in preclinical melanoma models, demonstrating significant intrinsic antitumor activity and no detectable off-target effects. When PA17 was used to functionali ze doxorubicin-loaded mesoporous silica nanoparticles, it resulted in a 65% reduction in tumor mass with a single local administration and a 55% reduction after three systemic administrations. This treatment was significantly more effective than free doxorubicin or non-targeted doxorubicin-loaded nanoparticles and was associated with a marked decrease in tumor vascularization. ConclusionsThis study highlights the potential of toxin-derived ligands as novel targeti ng agents for tumor neovasculature in aggressive cancers such as malignant melanoma. PA17, with its intrinsic antitumor properties and exceptional targeting efficacy, enhances the efficacy of nanomedicine and addresses common challenges such as drug resistance. The use of natural ligands represents a transformative approach to nanomedicine delivery and offers a promising strategy to advance cancer nanotherapy. Graphical abstract image O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/626996v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@ae5f6dorg.highwire.dtl.DTLVardef@1fb115borg.highwire.dtl.DTLVardef@309f9eorg.highwire.dtl.DTLVardef@3f53b5_HPS_FORMAT_FIGEXP M_FIG C_FIG

Extracellular vesicles (EVs) have been lauded as next generation medicines, but very few EV-based therapeutics have progressed to clinical use. Limited clinical translation is largely due to technical barriers that hamper our ability to mass-produce EVs, i.e. to isolate, purify and characterise them effectively. Technical limitations in comprehensive characterisation of EVs leads to unpredicted biological effects of EVs. Here, using a range of optical and non-optical techniques, we showed that the differences in molecular composition of EVs isolated using two isolation methods correlated with the differences in their biological function. Our results demonstrated that the isolation method determines the composition of isolated EVs at single and sub-population levels. Besides the composition, we measured for the first time the dry mass and predicted sedimentation of EVs. These parameters were shown to correlate well with the biological and functional effects of EVs on single cell and cell cultures. We anticipate that our new multiscale characterisation approach, which goes beyond traditional experimental methodology, will support fundamental understanding of EVs as well as elucidate the functional effects of EVs in in vitro and in vivo studies. Our findings and methodology will be pivotal for developing optimal isolation methods and establishing EVs as mainstream therapeutics and diagnostics. This innovative approach is applicable to a wide range of sectors including biopharma and biotechnology as well as to regulatory agencies.

Glioblastoma (GBM) is a malignant brain tumor with a poor long-term prognosis. The current median survival is approximately fifteen to twenty months with the standard of care therapy which includes surgery, radiation, and chemotherapy. An important factor contributing to recurrence of GBM is high resistance of GBM cancer stem cells (CSCs) to several anticancer drugs, for which a systemically delivered single drug approach will be unlikely to produce a viable cure. Therefore, multidrug therapies have the potential to improve the survival time. Currently, only temozolomide (TMZ), which is a DNA alkylator, affects overall survival in GBM patients. CSCs regenerate rapidly and over-express a methyl transferase which overrides the DNA-alkylating mechanism of TMZ, leading to drug resistance. Idasanutlin (RG7388, R05503781) is a potent, selective MDM2 antagonist that additively kills GBM CSCs when combined with TMZ. Nanotechnology is an emerging field that shows great promise in drug delivery and diagnostics. The ability to combine both therapy and imaging allows real time assessment of drug delivery in vivo for the field of theranostics. To develop a multi-drug therapy using multi-functional nanoparticles (NPs) that preferentially target the GBM CSC subpopulation and provide in vivo preclinical imaging capability. Polymer-micellar NPs composed of poly(styrene-b-ethylene oxide) (PS-b-PEO) and poly(lactic-co-glycolic) acid (PLGA) were developed investigating both single and double emulsion fabrication techniques as well as combinations of TMZ and RG7388. The NPs were covalently bound to a 15-base-pair CD133 aptamer in order to target the CD133 antigen expressed on the surface of GBM CSC subpopulation. For theranostic functionality, the NPs were also labelled with a radiotracer, Zirconium-89 (89Zr). The NPs maintained a small size of less than 100 nm, a low negative charge and exhibited the ability to effectively target and kill the CSC subpopulation. In addition, the conjugation of the CD133 aptamer was able to promote killing in CSCs leading to the justification of a targeted nanosystem to potentially improve localized therapy in future in vivo models. This work has provided a potentially therapeutic option for GBM specific for CSC targeting and theranostic imaging.

In this study, we describe the cytotoxic and antibacterial capabilities of gold nanoparticles (GNPs) synthesized from Dillenia indica leaves. Here, we used an environmentally friendly method to synthesize GNPs and then characterized them using techniques such as transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-visible spectroscopy, XRD, and Fourier transform infrared spectroscopy. The Surface Plasmon Resonance of GNPs was identified by an absorption peak at 533 nm in the UV-visible spectroscopic studies. The biosynthesized GNPs had an average size of 83 nm and were spherical in shape, according to TEM examination. Its interesting to note that the biosynthesized GNPs exhibited antibacterial action against a variety of bacterial isolates, both Gram-positive and negative. By using an MTT assay, growth inhibition and the cytotoxic effect of the synthesized GNPs against Daltons lymphoma cell lines were also evaluated.

Nanoalgosomes are extracellular vesicles (EVs) released by microalgal cells that can mediate intercellular and cross-kingdom communication. In the present study, starting from the optimized nanoalgosome manufacturing from cultures of marine microalgae, we evaluated their innate biological properties in preclinical models. Our investigation of nanoalgosome biocompatibility included toxicological analyses, starting from studies on the invertebrate model organism Caenorhabditis elegans, proceeding to hematological and immunological evaluations in mice and immune-compatibility ex vivo. Nanoalgosome biodistribution was evaluated in mice with accurate space-time resolution, and in C. elegans at cellular and subcellular levels. Further examination highlighted the antioxidant and anti-inflammatory bioactivities of nanoalgosomes. This holistic approach to nanoalgosome functional characterization showcases that nanoalgosomes are innate effectors and potential drug delivery system for novel cosmetic formulations and EV-based therapies.

Active targeting is based on the binding of ligands to receptors present on the surface of targeted cells, in order to promote the internalization of the drugs conjugated to the ligands. Several conjugates are already in use or under development for active targeting of tumors, the most widely known being antibody-drug conjugates (ADC). They combine the specificity of monoclonal antibodies with the cytotoxicity of chemotherapeutic molecules. Other than antibodies, nucleic-acid aptamers, are promising ligands to deliver conjugated drugs by active targeting in tumor cells. The therapeutic efficacy of conjugates largely depends on their endocytosis and vesicular trafficking. However, so far, no therapeutic approach to enhance endocytosis of conjugates is available. In recent studies, we showed that gefitinib, a tyrosine kinase inhibitor directed against the epidermal growth factor receptor EGFR, induces a massive, non-physiological endocytosis of EGFR, known as gefitinib-mediated endocytosis (GME), in different glioblastoma cell lines. We thus hypothesized that besides promoting endocytosis of EGFR, gefitinib could also promote endocytosis of its ligands. In this study, we proved by quantitative fluorescence bioimaging, that gefitinib is indeed able to strengthen the endocytosis of fluorophore-conjugated EGFR-specific antibodies and aptamers. We also showed that the GME potentiates the toxicity of an antibody-drug conjugate, even at low concentrations. Our results suggest the development of a new therapeutic combination, of ADC and gefitinib, to potentiate the delivery of ADC and likely other conjugates targeting EGFR in glioblastoma, while limiting side effects on non-targeted cells.

Extracellular vesicles (EVs) are involved in mediating intercellular communication processes. An important goal within the EV field is the study of the biodistribution of EVs and the identification of their target cells. Considering that EV uptake is central for mediating the EVs role in intercellular communication processes, labelling with fluorescent dyes has emerged as a broadly distributed strategy for the identification of the EVs target cells and tissues. However, the accuracy and specificity of commonly utilized labelling dyes has not been sufficiently analyzed. By combining recent advancements in imaging flow cytometry for the phenotypic analysis of single EVs and aiming to identify target cells for EVs within therapeutically relevant MSC-EV preparations, we explored the EV labelling efficacy of various fluorescent dyes, specifically of CFDA-SE, Calcein AM, PKH67, BODIPY-TR-Ceramide and a novel lipid dye named Exoria. Our analyses qualified Exoria as the only dye which specifically labels EVs within our MSC-EV preparations. Furthermore, we demonstrate Exoria labelling does not interfere with the immunomodulatory properties of the MSC-EV preparations as tested in a multi-donor mixed lymphocyte reaction assay. Within this assay, labelled EVs were differentially taken-up by different immune cell types. Overall, our results qualify Exoria as an appropriate dye for the labelling of EVs derived from our MSC-EV preparations, this study also demonstrates the need for the development of next generation EV characterization tools which are able to localize and confirm specificity of EV labelling.

Layered double hydroxides (LDHs) have emerged as promising nanocarriers for RNA interference (RNAi)-based crop protection due to their ability to stabilize and effectively deliver pathogen-specific double-stranded RNA (dsRNA). However, their potential against obligate biotrophic pathogens like powdery mildews remains unexplored. In this study, we investigated Magnesium Iron-LDH (MgFe-LDH) nanomaterials as carriers of fungal effector dsRNA (Ef-dsRNA) and evaluated the efficacy of the resulting complex in suppressing Erysiphe pisi (powdery mildew) infection in pea (Pisum sativum) via foliar spray application. The synthesized LDH nanomaterial exhibits strong leaf adherence, biocompatibility, and high dsRNA loading capacity, protects the dsRNA against RNase-mediated degradation, and facilitates its sustained release over time. Foliar spray application of the Ef-dsRNA-LDH complex on intact pea plants results in enhanced gene silencing of the target fungal effector and confers greater and prolonged local and systemic powdery mildew disease protection compared to treatments with dsRNA or LDH alone. Following spray application, the LDH nanomaterial is rapidly taken up by intact pea leaf cells and from the plant into E. pisi hyphae via haustoria, enabling efficient dsRNA delivery and silencing of the target gene up to 15 days post-application. Overall, our Ef-dsRNA-LDH formulation offers a robust, sustainable, and targeted approach for RNAi-mediated control of powdery mildews.

Fungal adhesion to stainless steel, an alloy commonly used in food and beverage sectors, public and healthcare settings, and numerous medical devices, can give rise to serious infections, ultimately leading to morbidity, mortality, and significant healthcare expenses. In this study, we demonstrate that nanotextured stainless steel (nSS) fabricated using an electrochemical technique is an antibiotic-free biocidal surface against Candida Albicans and Fusarium Oxysporum with 98% and 97% reduction, respectively. The nanoprotrusion features on nSS can have both physical contact with cell membranes and chemical impact on cells through production of reactive species, this material should not contribute to drug resistant fungus as antibiotics can. As nSS is also antibacterial and compatible with mammalian cells, demonstration of antifungal activity gives nSS the potential to be used to create effective, scalable, and sustainable solutions to broadly and responsibly prevent fungal and other microbial infections caused by surface contamination. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=76 SRC="FIGDIR/small/616307v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@9c037dorg.highwire.dtl.DTLVardef@a93518org.highwire.dtl.DTLVardef@dccc6forg.highwire.dtl.DTLVardef@1f19515_HPS_FORMAT_FIGEXP M_FIG C_FIG

Efficient, aggregation-free extracellular vesicles (EVs) labeling is essential for studying their dynamics in-vitro and in-vivo. However, traditional dyes introduce limitations including aggregation, membrane intercalation, fluorescence transfer and inconsistent performance across EV sources thus distorting quantification, altering surface properties and confounding uptake and biodistribution analyses. Here, we systematically evaluated CytoLight, a luminal dye traditionally used for live-cell imaging, as an alternative for EV quantification, characterization, uptake analysis and in-vivo tracking, benchmarking it against PKH26, CFSE and ExoBrite across multiple platforms. CytoLight generated stable, intravesicular fluorescence without aggregation or membrane alteration, eliminating artifacts characteristic of conventional dyes. Using fluorescence-NTA and single-EV flow cytometry, CytoLight showed more consistent labeling across EV types than CFSE or ExoBrite, while avoiding PKH-related micelle-driven artifacts and exhibited compatibility with CD81 dual-detection. In uptake assays, CytoLight produced EV-specific endocytosis-dependent internalization signals exceeding labeled-BPS/protein controls. In-vivo, CytoLight-labeled EVs enabled fluorescent biodistribution mapping showing conventional EV tropism patterns distinguishable from labeled-PBS controls. These findings establish CytoLight as an effective, aggregation-free EV-labeling strategy. Its stability, specificity, compatibility with single-EV platforms and reliable performance in both cellular uptake and biodistribution studies position CytoLight as a practical, scalable alternative to current dyes, providing a stronger foundation for standardized and reproducible EV research.