Colorimetric nanoplasmonic assay to determine purity and titrate extracellular vesicles

The influence of tumour-derived extracellular vesicles on local and distal metastatic dissemination

Extracellular vesicles (EVs) are key mediators of intercellular communication that have been ignored for decades. Tumour cells benefit from the secretion of vesicles as they can influence the behaviour of neighbouring tumour cells within the tumour microenvironment. Several studies have shown that extracellular vesicles play an active role in pre-metastatic niche formation and importantly, they are involved in the metastatic organotropism of different tumour types. Tumour-derived EVs carry and transfer molecules to recipient cells, modifying their behaviour through a process defined as "EV-driven education". EVs favour metastasis to sentinel lymph nodes and distal organs by reinforcing angiogenesis, inflammation and lymphangiogenesis. Hence, in this review we will summarize the main mechanisms by which tumour-derived EVs regulate lymph node and distal organ metastasis. Moreover, since some cancers metastasize through the lymphatic system, we will discuss recent discoveries about the presence and function of tumour EVs in the lymph. Finally, we will address the potential value of tumour EVs as prognostic biomarkers in liquid biopsies, specially blood and lymphatic fluid, and the use of these tools as early detectors of metastases.

Localized surface plasmon resonance based biosensing

INTRODUCTION

Bioanalytical sensing based on the principle of localized surface plasmon resonance experiences is currently an extremely rapid development. Novel sensors with new kinds of plasmonic transducers and innovative concepts for the signal development as well as read-out principles were identified. This review will give an overview of the development of this field. Areas covered: The focus is primarily on types of transducers by preparation or dimension, factors for optimal sensing concepts and the critical view of the usability of these devices as innovative sensors for bioanalytical applications. Expert commentary: Plasmonic sensor devices offer a high potential for future biosensing given that limiting factors such as long-time stability of the transducers, the required high sensitivity and the cost-efficient production are addressed. For higher sensitivity, the design of the sensor in shape and material has to be combined with optimal enhancement strategies. Plasmonic nanoparticles from bottom-up synthesis with a post-synthetic processing show a high potential for cost-efficient sensor production. Regarding the measurement principle, LSPRi offers a large potential for multiplex sensors and can provide a high-throughput as well as highly paralleled sensing. The main trends are expected towards optimal LSPR concepts which represent cost-efficient and robust point-of-care solutions, and the use of multiplexed devices for clinical applications.

Biophysical properties of extracellular vesicles in diagnostics

Extracellular vesicles (EVs) are cell-derived nanoparticles, involved in cell-to-cell communication, in both normal and pathological processes. Originating by the outward budding of the plasma membrane or released by exocytosis, they are natural cargoes for lipids, carbohydrates, proteins and nucleic acids. EV-based diagnostics promises unique advantages compared with conventional strategies involving whole body fluid analysis, including the reduction of biofluids complexity and more specific and sensitive detection of low abundance biomacromolecules. Besides EV cargoes, new breakthrough technologies are addressing EV 'colloidal properties' - including particle content, size and membrane mechanical properties - directly experienced by researchers to be critical factors in biomarkers discovery. This article focuses on the progresses in EV biophysical properties characterization as diagnostic tools for different pathological conditions.

Counting of peripheral extracellular vesicles in Multiple Sclerosis patients by an improved nanoplasmonic assay and dynamic light scattering

Extracellular vesicles (EVs) are vesicles naturally secreted by the majority of human cells. Being composed by a closed phospholipid bilayer secluding proteins and RNAs they are used to transfer molecular information to other cells, thereby influencing the recipient cell functions. Despite the increasingly recognized relevance of EVs, the clarification of their physiological role is hampered by the lack of suitable analytical tools for their quantification and characterization. In this study, we have implemented a nanoplasmonic assay, previously proposed for the purity of the EV fractions, to achieve a robust analytical protocol in order to quantify the total phospholipid concentration (C_PL) and the EVs number. We show how the coupling of the nanoplasmonic assay with serial dilutions of the unknown sample allows, by simple visual inspection, to detect deviations from the physiological EVs content. The use of a response that depends on the absorbance values at three wavelengths permits to reduce the limit of detection of C_PL to 5 μM (total) and the limit of quantification to 35 μM. We also propose a method that takes into account the spread in EV size when the concentration of phospholipids is turned into a concentration of vesicles. The proposed analytical protocol is successfully applied to a small cohort of Multiple Sclerosis patients examined in different stages of their clinical diseases.

Hemoglobin-driven iron-directed assembly of gold nanoparticles

The ability to form complex 3D architectures using nanoparticles (NPs) as the building blocks and complex macromolecules that direct these assemblies remains a challenging objective for nanotechnology. Here we report results in which the partial substitution of classical Turkevich citrate-capped gold NPs by a novel, heteroaromatic ligand (L) results in NPs able to form coordination-driven assemblies mediated by free or protein-bound iron ions. The morphology of these assemblies can be tuned depending on the source of iron. To prove the concept, classical citrate and novel NPs were reacted with iron-containing protein hemoglobin (Hb). To diminish the influence of possible electrostatic interactions of native Hb and gold NPs, the reaction was performed at the isoelectric point of Hb. Moreover, thiol groups of Hb were protected with p-quinone to exclude thiol–gold bond formation. As expected, citrate-capped gold NPs are well dispersed in functionalized Hb, while L-functionalized NPs form assemblies. The blue shift of the Soret band of the functionalized Hb, when reacted with novel NPs, unambiguously confirms the coordination of a NP-anchored heteroaromatic ligand with the heme moiety of Hb. Coarse-grained molecular dynamics of this system were performed to gain information about aggregation dynamics and kinetics of iron- and hemoglobin-templated assemblies of L–NPs. A multi-scale simulation approach was employed to extend this model to longer time scales. The application of this model towards novel coordination-based assemblies can become a powerful tool for the development of new nanomaterials.

The ability to form complex 3D architectures using nanoparticles as the building blocks and complex macromolecules that direct these assemblies remains a challenging objective for nanotechnology.

Exosomes Secreted by HeLa Cells Shuttle on Their Surface the Plasma Membrane-Associated Sialidase NEU3

Sialidases are glycohydrolases that remove terminal sialic acid residues from oligosaccharides, glycolipids, and glycoproteins. The plasma membrane-associated sialidase NEU3 is involved in the fine-tuning of sialic acid-containing glycans directly on the cell surface and plays relevant roles in important biological phenomena such as cell differentiation, molecular recognition, and cancer transformation. Extracellular vesicles are membranous structures with a diameter of 0.03-1 μm released by cells and can be detected in blood, urine, and culture media. Among extracellular vesicles, exosomes play roles in intercellular communication and maintenance of several physiological and pathological conditions, including cancer, and could represent a useful diagnostic tool for personalized nanomedicine approaches. Using inducible expression of the murine form of NEU3 in HeLa cells, a study of the association of the enzyme with exosomes released in the culture media has been performed. Briefly, NEU3 is associated with highly purified exosomes and localizes on the external leaflet of these nanovesicles, as demonstrated by enzyme activity measurements, Western blot analysis, and dot blot analysis using specific protein markers. On the basis of these results, it is plausible that NEU3 activity on exosome glycans enhances the dynamic biological behavior of these small extracellular vesicles by modifying the negative charge and steric hindrance of their glycocalyx. The presence of NEU3 on the exosomal surface could represent a useful marker for the detection of these nanovesicles and a tool for improving our understanding of the biology of these important extracellular carriers in physiological and pathological conditions.

Bioreducible Hydrophobin-Stabilized Supraparticles for Selective Intracellular Release

One of the main hurdles in nanomedicine is the low stability of drug-nanocarrier complexes as well as the drug delivery efficiency in the region-of-interest. Here, we describe the use of the film-forming protein hydrophobin HFBII to organize dodecanethiol-protected gold nanoparticles (NPs) into well-defined supraparticles (SPs). The obtained SPs are exceptionally stable in vivo and efficiently encapsulate hydrophobic drug molecules. The HFBII film prevents massive release of the encapsulated drug, which, instead, is activated by selective SP disassembly triggered intracellularly by glutathione reduction of the protein film. As a consequence, the therapeutic efficiency of an encapsulated anticancer drug is highly enhanced (2 orders of magnitude decrease in IC₅₀). Biodistribution and pharmacokinetics studies demonstrate the high stability of the loaded SPs in the bloodstream and the selective release of the payloads once taken up in the tissues. Overall, our results provide a rationale for the development of bioreducible and multifunctional nanomedicines.

RNA-seq reveals distinctive RNA profiles of small extracellular vesicles from different human liver cancer cell lines

Liver cancer (LC) is one of the most common cancers and represents the third highest cause of cancer-related deaths worldwide. Extracellular vesicle (EVs) cargoes, which are selectively enriched in RNA, offer great promise for the diagnosis, prognosis and treatment of LC. Our study analyzed the RNA cargoes of EVs derived from 4 liver-cancer cell lines: HuH7, Hep3B, HepG2 (hepato-cellular carcinoma) and HuH6 (hepatoblastoma), generating two different sets of sequencing libraries for each. One library was size-selected for small RNAs and the other targeted the whole transcriptome. Here are reported genome wide data of the expression level of coding and non-coding transcripts, microRNAs, isomiRs and snoRNAs providing the first comprehensive overview of the extracellular-vesicle RNA cargo released from LC cell lines. The EV-RNA expression profiles of the four liver cancer cell lines share a similar background, but cell-specific features clearly emerge showing the marked heterogeneity of the EV-cargo among the individual cell lines, evident both for the coding and non-coding RNA species.

Size distribution of extracellular vesicles by optical correlation techniques

Understanding the colloidal properties of extracellular vesicles (EVs) is key to advance fundamental knowledge in this field and to develop effective EV-based diagnostics, therapeutics and devices. Determination of size distribution and of colloidal stability of purified EVs resuspended in buffered media is a complex and challenging issue - because of the wide range of EV diameters (from 30 to 2000nm), concentrations of interest and membrane properties, and the possible presence of co-isolated contaminants with similar size and densities, such as protein aggregates and fat globules - which is still waiting to be fully addressed. We report here a fully detailed protocol for accurate and robust determination of the size distribution and stability of EV samples which leverages a dedicated combination of Fluorescence Correlation Spectroscopy (FCS) and Dynamic Light Scattering (DLS). The theoretical background, critical experimental steps and data analysis procedures are thoroughly presented and finally illustrated through the representative case study of EV formulations obtained from culture media of B16 melanoma cells, a murine tumor cell line used as a model for human skin cancers.

Emerging techniques in the isolation and characterization of extracellular vesicles and their roles in cancer diagnostics and prognostics

Extracellular vesicles (EVs) are cell-derived nanovesicles, present in almost all types of body fluids, which play an important role in intercellular communication and are involved in the transport of biological signals for regulating diverse cellular functions. Due to the increasing clinical interest in the role of EVs in tumor promotion, various techniques for their isolation, detection, and characterization are being developed. In this review, we present an overview of the current EV isolation and characterization methods in addition to their applications and limitations. Furthermore, EVs as the potential emerging biomarkers in cancer management and their clinical implementation are briefly discussed.

Gold Nanoparticle Based Platforms for Circulating Cancer Marker Detection

Detection of cancer-related circulating biomarkers in body fluids has become a cutting-edge technology that has the potential to noninvasively screen cancer, diagnose cancer at early stage, monitor tumor progression, and evaluate therapy responses. Traditional molecular and cellular detection methods are either insensitive for early cancer intervention or technically costly and complicated making them impractical for typical clinical settings. Due to their exceptional structural and functional properties that are not available from bulk materials or discrete molecules, nanotechnology is opening new horizons for low cost, rapid, highly sensitive, and highly specific detection of circulating cancer markers. Gold nanoparticles have emerged as a unique nanoplatform for circulating biomarker detection owning to their advantages of easy synthesis, facile surface chemistry, excellent biocompatibility, and remarkable structure and environment sensitive optical properties. In this review, we introduce current gold nanoparticle-based technology platforms for the detection of four major classes of circulating cancer markers - circulating tumor cells, vesicles, nucleic acids, and proteins. The techniques will be summarized in terms of signal detection strategies. Distinctive examples are provided to highlight the state-of-the-art technologies that significantly advance basic and clinical cancer research.

Cultured human amniocytes express hTERT, which is distributed between nucleus and cytoplasm and is secreted in extracellular vesicles

BACKGROUND

An increasing number of studies on stem cells suggests that the therapeutic effect they exert is primarily mediated by a paracrine regulation through extracellular vesicles (EVs) giving solid grounds for stem cell EVs to be exploited as agents for treating diseases or for restoring damaged tissues and organs. Due to their capacity to differentiate in all embryonic germ layers, amniotic fluid stem cells (AFCs), represent a highly promising cell type for tissue regeneration, which however is still poorly studied and in turn underutilized. In view of this, we conducted a first investigation on the expression of human hTERT gene - known to be among the key triggers of organ regeneration - in AFCs and in the EVs they secrete.

METHODS

Isolated AFCs were evaluated by RT-qPCR for hTERT expression. The clones expressing the highest levels of transcript, were analyzed by Immunofluorescence imaging and Nuclear/cytoplasmic fractionation in order to evaluate hTERT subcellular localization. We then separated EVs from FBS depleted culture medium by serial (ultra) centrifugations steps and characterized them using Western blotting, Atomic force Microscopy and Nanoplasmonic assay.

RESULTS

We first demonstrated that primary cultures of AFCs express the gene hTERT at different levels. Then we evidenced that in AFCs with the higher transcript levels, the hTERT protein is present in the nuclear and cytoplasmic compartment. Finally, we found that cytosolic hTERT is embodied in the EVs that AFCs secrete in the extracellular milieu.

CONCLUSIONS

Our study demonstrates for the first time the expression of the full protein hTERT by AFCs and its release outside the cell mediated by EVs, indicating a new extra telomeric role for this protein. This finding represents an initial but crucial evidence for considering AFCs derived EVs as new potential sources for tissue regeneration.

Development of a NanoBioAnalytical platform for "on-chip" qualification and quantification of platelet-derived microparticles

Blood microparticles (MPs) are small membrane vesicles (50-1000nm), derived from different cell types. They are known to play important roles in various biological processes and also recognized as potential biomarkers of various health disorders. Different methods are currently used for the detection and characterization of MPs, but none of these methods is capable to quantify and qualify total MPs at the same time, hence, there is a need to develop a new approach for simultaneous detection, characterization and quantification of microparticles. Here we show the potential of surface plasmon resonance (SPR) method coupled to atomic force microscopy (AFM) to quantify and qualify platelet-derived microparticles (PMPs), on the whole nano-to micro-meter scale. The different subpopulations of microparticles could be determined via their capture onto the surface using specific ligands. In order to verify the correlation between the capture level and the microparticles concentration in solution, two calibration standards were used: Virus-Like Particles (VLPs) and synthetic beads with a mean diameter of 53nm and 920nm respectively. The AFM analysis of the biochip surface allowed metrological analysis of captured PMPs and revealed that more than 95% of PMPs were smaller than 300nm. Our results suggest that our NanoBioAnalytical platform, combining SPR and AFM, is a suitable method for a sensitive, reproducible, label-free characterization and quantification of MPs over a wide concentration range (≈10⁷ to 10¹² particles/mL; with a limit of detection (LOD) in the lowest ng/µL range) which matches with their typical concentrations in blood.

Methods for the physical characterization and quantification of extracellular vesicles in biological samples

BACKGROUND

Our body fluids contain a multitude of cell-derived vesicles, secreted by most cell types, commonly referred to as extracellular vesicles. They have attracted considerable attention for their function as intercellular communication vehicles in a broad range of physiological processes and pathological conditions. Extracellular vesicles and especially the smallest type, exosomes, have also generated a lot of excitement in view of their potential as disease biomarkers or as carriers for drug delivery. In this context, state-of-the-art techniques capable of comprehensively characterizing vesicles in biological fluids are urgently needed.

SCOPE OF REVIEW

This review presents the arsenal of techniques available for quantification and characterization of physical properties of extracellular vesicles, summarizes their working principles, discusses their advantages and limitations and further illustrates their implementation in extracellular vesicle research.

MAJOR CONCLUSIONS

The small size and physicochemical heterogeneity of extracellular vesicles make their physical characterization and quantification an extremely challenging task. Currently, structure, size, buoyant density, optical properties and zeta potential have most commonly been studied. The concentration of vesicles in suspension can be expressed in terms of biomolecular or particle content depending on the method at hand. In addition, common quantification methods may either provide a direct quantitative measurement of vesicle concentration or solely allow for relative comparison between samples.

GENERAL SIGNIFICANCE

The combination of complementary methods capable of detecting, characterizing and quantifying extracellular vesicles at a single particle level promises to provide new exciting insights into their modes of action and to reveal the existence of vesicle subpopulations fulfilling key biological tasks.

Therapeutic and diagnostic applications of extracellular vesicles

During the past two decades, extracellular vesicles (EVs) have been identified as important mediators of intercellular communication, enabling the functional transfer of bioactive molecules from one cell to another. Consequently, it is becoming increasingly clear that these vesicles are involved in many (patho)physiological processes, providing opportunities for therapeutic applications. Moreover, it is known that the molecular composition of EVs reflects the physiological status of the producing cell and tissue, rationalizing their exploitation as biomarkers in various diseases. In this review the composition, biogenesis and diversity of EVs is discussed in a therapeutic and diagnostic context. We describe emerging therapeutic applications, including the use of EVs as drug delivery vehicles and as cell-free vaccines, and reflect on future challenges for clinical translation. Finally, we discuss the use of EVs as a biomarker source and highlight recent studies and clinical successes.

Residual matrix from different separation techniques impacts exosome biological activity

Exosomes are gaining a prominent role in research due to their intriguing biology and several therapeutic opportunities. However, their accurate purification from body fluids and detailed physicochemical characterization remain open issues. We isolated exosomes from serum of patients with Multiple Myeloma by four of the most popular purification methods and assessed the presence of residual contaminants in the preparations through an ad hoc combination of biochemical and biophysical techniques - including Western Blot, colloidal nanoplasmonics, atomic force microscopy (AFM) and scanning helium ion microscopy (HIM). The preparations obtained by iodixanol and sucrose gradients were highly pure. To the contrary, those achieved with limited processing (serial centrifugation or one step precipitation kit) resulted contaminated by a residual matrix, embedding the exosomes. The contaminated preparations showed lower ability to induce NfkB nuclear translocation in endothelial cells with respect to the pure ones, probably because the matrix prevents the interaction and fusion of the exosomes with the cell membrane. These findings suggest that exosome preparation purity must be carefully assessed since it may interfere with exosome biological activity. Contaminants can be reliably probed only by an integrated characterization approach aimed at both the molecular and the colloidal length scales.

Nanomedicine delivery: does protein corona route to the target or off road?

Nanomedicine aims to find novel solutions for urgent biomedical needs. Despite this, one of the most challenging hurdles that nanomedicine faces is to successfully target therapeutic nanoparticles to cells of interest in vivo. As for any biomaterials, once in vivo, nanoparticles can interact with plasma biomolecules, forming new entities for which the name protein coronas (PCs) have been coined. The PC can influence the in vivo biological fate of a nanoparticle. Thus for guaranteeing the desired function of an engineered nanomaterial in vivo, it is crucial to dissect its PC in terms of formation and evolution within the body. In this contribution we will review the 'good' and 'bad' sides of the PC, starting from the scientific aspects to the technological applications.

Merging colloidal nanoplasmonics and surface plasmon resonance spectroscopy for enhanced profiling of multiple myeloma-derived exosomes

A novel approach for sorting exosomes from multiple myeloma (MM), monoclonal gammopathy of undetermined significance (MGUS) and healthy individuals is presented. The method is based on the combination of colloidal gold nanoplasmonics and surface plasmon resonance (SPR) biosensing and probes distinctive colloidal properties of MM-derived exosomes, such as molar concentration and cell membrane binding preferences. It allowed to discover that MM patients produce about four folds more exosomes than MGUS and healthy individuals. In addition, it showed that among the analyzed exosomes, only the MM-derived ones bind heparin - a structural analog of heparan sulfate proteoglycans known to mediate exosome endocytosis - with an apparent dissociation constant (Kd) equal to about 1 nM, indicating a high affinity binding. This plasmonic method complements the classical biochemical profiling approach to exosomes, expanding the MM biomarker panel and adding biosensors to the toolbox to diagnose MM. It may find applications for other diseases and has wider interest for fundamental and translational research involving exosomes.