High content, quantitative AFM analysis of the scalable biomechanical properties of extracellular vesicles

Cellulose Nanofibrils of High Immunoaffinity for Efficient Enrichment of Small Extracellular Vesicles

Extracellular vesicles (EVs), crucial in facilitating the transport of diverse molecular cargoes for intercellular communication, have shown great potential in diagnostics, therapeutics, and drug delivery. The challenge of developing effective preparation methods for EVs is heightened by their intrinsic heterogeneity and complexity. Here, a novel strategy for high EV enrichment is developed by utilizing EV-affinitive-modified cellulose nanofibrils. Specifically, modified cellulose with rich carboxyl groups has outstanding dispersing properties, able to be dispersed into cellulose nanofibrils in solution. These cellulose nanofibrils are utilized as scaffolds for the immobilization of EV-affinitive antibody of CD63 by chemical conjugation. The CD63-modified nanofibrils demonstrate a superior EV capture efficiency of 86.4% compared with other reported methods. The high performance of this system is further validated by the efficient capture of EVs from biological blood plasma, allowing the detection of bioactive markers from EV-derived miRNAs and proteins. The authors envision that these modified cellulose nanofibrils of enhanced capability on EV enrichment will open new avenues in various biomedical applications.

Mechanical properties of blood exosomes and lipoproteins after the rat whole blood irradiation with X-rays in vitro explored by atomic force microscopy

Blood is a two-component system with two levels of hierarchy: the macrosystem of blood formed elements and the dispersed system of blood nanoparticles. Biological nanoparticles are the key participants in communication between the irradiated and non-irradiated cells and inducers of the non-targeted effects of ionizing radiation. The work aimed at studying by atomic force microscopy the structural, mechanical, and electrical properties of exosomes and lipoproteins (LDL/VLDL) isolated from rat blood after its exposure to X-rays in vitro.

MATERIALS AND METHODS

The whole blood of Wistar rats fed with a high-fat diet was irradiated with X-rays (1 and 100 Gy) in vitro. The structural and mechanical properties (the elastic modulus and nonspecific adhesion force) of exosome and lipoprotein isolates from the blood by ultracentrifugation method were studied using Bruker Bioscope Resolve atomic force microscope in PF QNM mode, their electric properties (the zeta-potential) was measured by electrophoretic mobility.

RESULTS

Lipoproteins isolated from non-irradiated blood were softer (Me(LQ; UQ): 7.8(4.9;12.1) MPa) compared to blood nanoparticles of its exosome fraction (34.8(22.6;44.9) MPa) containing both exosomes and non-membrane nanoparticles. X-ray blood irradiation with a dose of 1 Gy significantly weakened the elastic properties of lipoproteins. Exposure of the blood to 100 Gy X-rays made lipoproteins stiffer and their nonspecific adhesive properties stronger. The radiation effects on the mechanical parameters of exosomes and non-membrane nanoparticles in exosome fractions differed. The significant radiation-induced change in electric properties of the studied nanoparticles was detected only for lipoproteins in the blood irradiated with 1 Gy X-rays. The low-dose radiation-induced changes in zeta-potential and increase in lipoprotein size with the appearance of a soft thick surface layer indicate the formation of the modified lipoproteins covered with a corona from macromolecules of irradiated blood.

CONCLUSION

Our data obtained using the nanomechanical mapping mode of AFM are the first evidence of the significant radiation-induced changes in the structural and mechanical properties of the dispersed system of blood nanoparticles after the X-ray irradiation of the blood.

Extracellular Vesicle Preparation and Analysis: A State-of-the-Art Review

In recent decades, research on Extracellular Vesicles (EVs) has gained prominence in the life sciences due to their critical roles in both health and disease states, offering promising applications in disease diagnosis, drug delivery, and therapy. However, their inherent heterogeneity and complex origins pose significant challenges to their preparation, analysis, and subsequent clinical application. This review is structured to provide an overview of the biogenesis, composition, and various sources of EVs, thereby laying the groundwork for a detailed discussion of contemporary techniques for their preparation and analysis. Particular focus is given to state-of-the-art technologies that employ both microfluidic and non-microfluidic platforms for EV processing. Furthermore, this discourse extends into innovative approaches that incorporate artificial intelligence and cutting-edge electrochemical sensors, with a particular emphasis on single EV analysis. This review proposes current challenges and outlines prospective avenues for future research. The objective is to motivate researchers to innovate and expand methods for the preparation and analysis of EVs, fully unlocking their biomedical potential.

Application of Single Extracellular Vesicle Analysis Techniques

Extracellular vesicles (EVs) are lipid containers that are actively released by cells and contain complex molecular cargoes. These cargoes include abundant material such as genomes and proteins from cells of origin. They are involved in intercellular communication and various pathological processes, showing excellent potential for diagnosing and treating diseases. Given the significant heterogeneity of EVs in complex physiopathological processes, unveiling their composition is essential to understanding their function. Bulk detection methods have been previously used to analyze EVs, but they often mask their heterogeneity, leading to the loss of valuable information. To overcome this limitation, single extracellular vesicle (SEV) analysis techniques have been developed and advanced. These techniques allow for analyzing EVs' physical information and biometric molecules at the SEV level. This paper reviews recent advances in SEV detection methods and summarizes some clinical applications for SEV detection strategies.

Putative Wound Healing Induction Functions of Exosomes Isolated from IMMUNEPOTENT CRP

Chronic wounds in diabetic patients can take months or years to heal, representing a great cost for the healthcare sector and impacts on patients' lifestyles. Therefore, new effective treatment alternatives are needed to accelerate the healing process. Exosomes are nanovesicles involved in the modulation of signaling pathways that can be produced by any cell and can exert functions similar to the cell of origin. For this reason, IMMUNEPOTENT CRP, which is a bovine spleen leukocyte extract, was analyzed to identify the proteins present and is proposed as a source of exosomes. The exosomes were isolated through ultracentrifugation and shape-size, characterized by atomic force microscopy. The protein content in IMMUNEPOTENT CRP was characterized by EV-trap coupled to liquid chromatography. The in silico analyses for biological pathways, tissue specificity, and transcription factor inducement were performed in GOrilla ontology, Panther ontology, Metascape, and Reactome. It was observed that IMMUNEPOTENT CRP contains diverse peptides. The peptide-containing exosomes had an average size of 60 nm, and exomeres of 30 nm. They had biological activity capable of modulating the wound healing process, through inflammation modulation and the activation of signaling pathways such as PIP3-AKT, as well as other pathways activated by FOXE genes related to specificity in the skin tissue.

DG, Sun L, Banjara B, Mosley-Kellum K, Dinh TC, Singh M. Cannabidiol-Loaded Extracellular Vesicles from Human Umbilical Cord Mesenchymal Stem Cells Alleviate Paclitaxel-Induced Peripheral Neuropathy

In cancer patients, chronic paclitaxel (PTX) treatment causes excruciating pain, limiting its use in cancer chemotherapy. The neuroprotective potential of synthetic cannabidiol (CBD) and CBD formulated in extracellular vesicles (CBD-EVs) isolated from human umbilical cord derived mesenchymal stem cells was investigated in C57BL/6J mice with PTX-induced neuropathic pain (PIPN). The particle size of EVs and CBD-EVs, surface roughness, nanomechanical properties, stability, and release studies were all investigated. To develop neuropathy in mice, PTX (8 mg/kg, i.p.) was administered every other day (four doses). In terms of decreasing mechanical and thermal hypersensitivity, CBD-EVs treatment was superior to EVs treatment or CBD treatment alone (p < 0.001). CBD and CBD-EVs significantly reduced mitochondrial dysfunction in dorsal root ganglions and spinal homogenates of PTX-treated animals by modulating the AMPK pathway (p < 0.001). Studies inhibiting the AMPK and 5HT1A receptors found that CBD did not influence the neurobehavioral or mitochondrial function of PIPN. Based on these results, we hypothesize that CBD and CBD-EVs mitigated PIPN by modulating AMPK and mitochondrial function.

Nanoscale biophysical properties of small extracellular vesicles from senescent cells using atomic force microscopy, surface potential microscopy, and Raman spectroscopy

Cells secrete extracellular vesicles (EVs) carrying cell-of-origin markers to communicate with surrounding cells. EVs regulate physiological processes ranging from intercellular signaling to waste management. However, when senescent cells (SnCs) secrete EVs, the EVs, which are newly regarded as senescence-associated secretory phenotype (SASP) factors, can evoke inflammation, senescence induction, and metabolic disorders in neighboring cells. Unlike other soluble SASP factors, the biophysical properties of EVs, including small EVs (sEVs), derived from SnCs have not yet been investigated. In this study, sEVs were extracted from a human IMR90 lung fibroblast in vitro senescence model. Their biomechanical properties were mapped using atomic force microscopy-based quantitative nanomechanical techniques, surface potential microscopy, and Raman spectroscopy. The surfaces of sEVs derived from SnCs are slightly stiffer but their cores are softer than those of sEVs secreted from non-senescent cells (non-SnCs). This inversely proportional relationship between deformation and stiffness, attributed to a decrease in the concentration of genetic and protein materials inside the vesicles and the adsorption of positively charged SASP factors onto the vesicle surfaces, respectively, was found to be a peculiar characteristic of SnC-derived sEVs. Our results demonstrate that the biomechanical properties of SnC-derived sEVs differ from those of non-SnC-derived sEVs and provide insight into the mechanisms underlying their formation and composition.

Unveiling the Native Morphology of Extracellular Vesicles from Human Cerebrospinal Fluid by Atomic Force and Cryogenic Electron Microscopy

Extracellular vesicles (EVs) are membranous structures in biofluids with enormous diagnostic/prognostic potential for application in liquid biopsies. Any such downstream application requires a detailed characterization of EV concentration, size and morphology. This study aimed to observe the native morphology of EVs in human cerebrospinal fluid after traumatic brain injury. Therefore, they were separated by gravity-driven size-exclusion chromatography (SEC) and investigated by atomic force microscopy (AFM) in liquid and cryogenic transmission electron microscopy (cryo-TEM). The enrichment of EVs in early SEC fractions was confirmed by immunoblot for transmembrane proteins CD9 and CD81. These fractions were then pooled, and the concentration and particle size distribution were determined by Tunable Resistive Pulse Sensing (around 10¹⁰ particles/mL, mode 100 nm) and Nanoparticle Tracking Analysis (around 10⁹ particles/mL, mode 150 nm). Liquid AFM and cryo-TEM investigations showed mode sizes of about 60 and 90 nm, respectively, and various morphology features. AFM revealed round, concave, multilobed EV structures; and cryo-TEM identified single, double and multi-membrane EVs. By combining AFM for the surface morphology investigation and cryo-TEM for internal structure differentiation, EV morphological subpopulations in cerebrospinal fluid could be identified. These subpopulations should be further investigated because they could have different biological functions.

GFP-tagging of extracellular vesicles for rapid process development

Extracellular vesicles (EVs) act as nano-scale molecular messengers owing to their capacity to shuttle functional macromolecular cargo between cells. This intrinsic ability to deliver bioactive cargo has sparked great interest in the use of EVs as novel therapeutic delivery vehicles; investments totalling over $2 billion in 2020 alone were reported for therapeutic EVs. One of the bottlenecks facing the production of EVs is the lack of rapid and high throughput analytics and characterisation to aid process development. Here we have designed and engineered CHO cells to express GFP-tagged EVs via fusion to CD81. Moreover, we highlight the importance of parent cell characterisation to ensure lack of non-fused GFP for the effective use of this quantitative approach. The fluorescent nature of resulting vesicles allowed for rapid quantification of concentration and yield across the EV purification process. In this manner we deduced the degree of product loss by mass balance analysis of ultrafiltration processing and reconciled up to 97% of initial feed mass. The use of GFP-tagging allowed for straightforward monitoring of vesicle elution from chromatography separations and detection via western blotting. Collectively, this work illustrates the utility of GFP-tagged EVs as a quantitative and accessible tool for accelerated process development. This article is protected by copyright. All rights reserved.

Speeding up the Topography Imaging of Atomic Force Microscopy by Convolutional Neural Network

Atomic force microscopy (AFM) provides unprecedented insight into surface topography research with ultrahigh spatial resolution at the subnanometer level. However, a slow scanning rate has to be employed to ensure the image quality, which will largely increase the accumulated sample drift, thereby, resulting in the low fidelity of the AFM image. In this paper, we propose a fast imaging method which performs a complete fast Raster scanning and a slow μ-path subsampling together with a deep learning algorithm to rapidly produce an AFM image with high quality and small drift. A supervised convolutional neural network (CNN) model is trained with the slow μ-path subsampled data and its counterpart acquired with fast Raster scan. The fast speed acquired AFM image is then inputted to the well-trained CNN model to output the high quality one. We validate the reliability of this method using a silicon grids sample and further apply it to the fast imaging of a vanadium dioxide thin film. The results demonstrate that this method can largely improve the imaging speed up to 10.3 times with state-of-the-art imaging quality, and reduce the sample drift by 8.9 times in the multiframe AFM imaging of the same area. Furthermore, we prove that this method is also applicable to other scanning imaging techniques such as scanning electrochemical microscopy.

Extracellular vesicles as delivery systems at nano-/micro-scale

Extracellular vesicles (EVs) have shown significant promises as nano-/micro-size carriers in drug delivery and bioimaging. With more characteristics of EVs explored through tremendous research efforts, their unmatched physicochemical properties, biological features, and mechanical aspects make them unique vehicles, owning exceptional pharmacokinetics, circulatory metabolism and biodistribution pattern when delivering theranostic cargoes. In this review we firstly analyzed pros and cons of the EVs as a delivery platform. Secondly, compared to engineered nanoparticle delivery systems, such as biocompatible di-block co-polymers, rational design to improve EVs (exosomes in particular) were elaborated. Lastly, different pharmaceutical loading approaches into EVs were compared, reaching a conclusion on how to construct a clinically available and effective nano-/micro-carrier for a satisfactory medical mission.