The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points.

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Minimal information for studies of extracellular vesicles 2018 (MISEV2018) : a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

Liposomes — microscopic phospholipid bubbles with a bilayered membrane structure — have received a lot of attention during the past 30 years as pharmaceutical carriers of great potential. More recently, many new developments have been seen in the area of liposomal drugs — from clinically approved products to new experimental applications, with gene delivery and cancer therapy still being the principal areas of interest. For further successful development of this field, promising trends must be identified and exploited, albeit with a clear understanding of the limitations of these approaches.

Recent advances with liposomes as pharmaceutical carriers.

Liposomal drug delivery systems: from concept to clinical applications.

The rapid recognition of intravenously injected colloidal carriers, such as liposomes and polymeric nanospheres from the blood by Kupffer cells, has initiated a surge of development for "Kupffer cell-evading" or long-circulating particles. Such carriers have applications in vascular drug delivery and release, site-specific targeting (passive as well as active targeting), as well as transfusion medicine. In this article we have critically reviewed and assessed the rational approaches in the design as well as the biological performance of such constructs. For engineering and design of long-circulating carriers, we have taken a lead from nature. Here, we have explored the surface mechanisms, which affords red blood cells long-circulatory lives and the ability of specific microorganisms to evade macrophage recognition. Our analysis is then centered where such strategies have been translated and fabricated to design a wide range of particulate carriers (e.g., nanospheres, liposomes, micelles, oil-in-water emulsions) with prolonged circulation and/or target specificity. With regard to the targeting issues, attention is particularly focused on the importance of physiological barriers and disease states.

Long-Circulating and Target-Specific Nanoparticles: Theory to Practice

Engineered nanoparticles have the potential to revolutionize the diagnosis and treatment of many diseases; for example, by allowing the targeted delivery of a drug to particular subsets of cells. However, so far, such nanoparticles have not proved capable of surmounting all of the biological barriers required to achieve this goal. Nevertheless, advances in nanoparticle engineering, as well as advances in understanding the importance of nanoparticle characteristics such as size, shape and surface properties for biological interactions, are creating new opportunities for the development of nanoparticles for therapeutic applications. This Review focuses on recent progress important for the rational design of such nanoparticles and discusses the challenges to realizing the potential of nanoparticles.

Strategies in the design of nanoparticles for therapeutic applications

https://febs.onlinelibrary.wiley.com/doi/epdf/10.1016/0014-5793%2890%2981016-H

Amphipathic polyethyleneglycols effectively prolong the circulation time of liposomes

Microbubbles in ultrasound-triggered drug and gene delivery

Apoptotic cells must be removed by phagocytes to avoid local inflammation. They expose phosphatidylserine, which is normally restricted to the inner leaflet of the plasma membrane, on their surface, acting as an 'eat-me' signal. This paper shows that the BAI1 protein is an upstream receptor for phosphatidylserine in mammalian macrophages

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BAI1 is an engulfment receptor for apoptotic cells upstream of the ELMO/Dock180/Rac module

Background— Angiogenesis is a critical determinant of tumor growth and metastasis. We hypothesized that contrast-enhanced ultrasound (CEU) with microbubbles targeted to αv-integrins expressed on the neovascular endothelium could be used to image angiogenesis. Methods and Results— Malignant gliomas were produced in 14 athymic rats by intracerebral implantation of U87MG human glioma cells. On day 14 or day 28 after implantation, CEU was performed with microbubbles targeted to αvβ3 by surface conjugation of echistatin. CEU perfusion imaging with nontargeted microbubbles was used to derive tumor microvascular blood volume and blood velocity. Vascular αv-integrin expression was assessed by immunohistochemistry, and microbubble adhesion was characterized by confocal microscopy. Mean tumor size increased markedly from 14 to 28 days (2±1 versus 35±14 mm2, P<0.001). Tumor blood volume increased by ≈35% from day 14 to day 28, whereas microvascular blood velocity decreased, especially at the central portions of the ...

Imaging Tumor Angiogenesis With Contrast Ultrasound and Microbubbles Targeted to αvβ3

Background Routine methods capable of assessing tissue inflammation noninvasively are currently not available. We hypothesized that tissue retention of microbubbles targeted to the endothelial cell adhesion molecule P-selectin would provide a means to assess inflammation with ultrasound imaging. Methods and Results Phospholipid microbubbles targeted to P-selectin (MBp) were created by conjugating monoclonal antibodies against murine P-selectin to the lipid shell. The microvascular behaviors of MBp and control microbubbles without antibody (MB) or with isotype control antibody (MBiso) were assessed by intravital microscopy of cremasteric venules of control and tumor necrosis factor (TNF)-α–stimulated wild-type mice. Retention of all microbubbles increased (P<0.05) with TNF-α treatment because of increased attachment to activated leukocytes. Extensive attachment of MBp directly to the venular endothelium or to adherent platelet-leukocyte aggregates was observed in TNF-α–stimulated mice, resulting in 4-fold ...

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Alexander L. Klibanov

Papers

Amphipathic polyethyleneglycols effectively prolong the circulation time of liposomes

Microbubbles in ultrasound-triggered drug and gene delivery

BAI1 is an engulfment receptor for apoptotic cells upstream of the ELMO/Dock180/Rac module

Imaging Tumor Angiogenesis With Contrast Ultrasound and Microbubbles Targeted to αvβ3

Ultrasound Assessment of Inflammation and Renal Tissue Injury With Microbubbles Targeted to P-Selectin