Extracellular vesicles for tumor targeting delivery based on five features principle

Patient-derived microvesicles/AIE luminogen hybrid system for personalized sonodynamic cancer therapy in patient-derived xenograft models

Sonodynamic therapy (SDT), as an efficient way of tumor treatment, has the advantages of deep tumor penetration and high therapeutic efficacy. However, developing efficient sonosensitizers are still challenging. AIEgen-based SDT is rarely reported and it is urgent to develop novel AIEgen-active sonosensitizers. Furthermore, the AIEgen-based theranostic system is promisingly needed to be proved on PDX models to be closer to the clinic. Herein, we constructed a novel AIEgen based SDT system and found that DCPy has advantages over traditional sonosensitizers in SDT. Then, a patient-derived MVs/AIEgen hybrid system (AMVs) prepared by electroporation was used for personalized SDT in bladder cancer patient-derived xenograft (PDX) models. Impressively, AMVs displayed the superior tumor targeting ability and efficient personalized SDT therapy on PDX models, both of which were much more improved compared with PLGA/AIEgens nanoparticles and cell line-derived micro vesicles. This work provides new ideas for both the design of AIE-active sonosensitizers and the SDT treatment of cancers, further expanding the potential clinical application of AIEgens in the future.

Recent Advancement and Technical Challenges in Developing Small Extracellular Vesicles for Cancer Drug Delivery

Extracellular vesicles (EVs) are a heterogeneous population of lipid bilayer membrane-enclosed vesicles and act like 'messages in a bottle' in cell-cell communication by transporting their cargoes to recipient cells. Small EVs (sEVs, < 200 nm) are highly researched recently and have been harnessed as novel delivery systems for the treatment of various diseases, including neurodegenerative disorders, cardiovascular diseases, and most importantly cancer primarily because of their non-immunogenicity, tissue penetration and cell-tropism. This review will first provide a comprehensive overview of sEVs regarding the current understanding on their properties, biogenesis, new classification by the ISEV, composition, as well as their roles in cancer development (thereby called "oncosomes"). The primary focus will be given to the current state of sEVs as natural nanocarriers for cancer drug delivery, the technologies and challenges involved in sEV isolation and characterization, therapeutic cargo loading, and surface modification to enhance tumor-targeting. We will also provide examples of sEV products under clinical trials. Furthermore, the current challenges as well as the advance in "sEV mimetics" to address some of the sEVs limitations is briefly discussed. We seek to advance our understanding of sEVs to unlock their full potential as superior drug delivery vehicles in cancer therapy.

The Use of Alternative Strategies for Enhanced Nanoparticle Delivery to Solid Tumors

Nanomaterial (NM) delivery to solid tumors has been the focus of intense research for over a decade. Classically, scientists have tried to improve NM delivery by employing passive or active targeting strategies, making use of the so-called enhanced permeability and retention (EPR) effect. This phenomenon is made possible due to the leaky tumor vasculature through which NMs can leave the bloodstream, traverse through the gaps in the endothelial lining of the vessels, and enter the tumor. Recent studies have shown that despite many efforts to employ the EPR effect, this process remains very poor. Furthermore, the role of the EPR effect has been called into question, where it has been suggested that NMs enter the tumor via active mechanisms and not through the endothelial gaps. In this review, we provide a short overview of the EPR and mechanisms to enhance it, after which we focus on alternative delivery strategies that do not solely rely on EPR in itself but can offer interesting pharmacological, physical, and biological solutions for enhanced delivery. We discuss the strengths and shortcomings of these different strategies and suggest combinatorial approaches as the ideal path forward.

Trends in Research on Exosomes in Cancer Progression and Anticancer Therapy

Simple Summary

Intensive research in the field of cancer biology has discovered a unique mode of interplay between cells via extracellular bioactive vesicles called exosomes. Exosomes serve as intermediators among cells via their cargoes that, in turn, contribute in the progression of cancer. They are ubiquitously present in all body fluids as they are secreted from both normal and tumor cells. These minuscules exhibit multiple unique properties that facilitate their migration to distant locations and modulate the microenvironment for progression of cancer. This review summarizes the multifarious role of exosomes in various aspects of cancer research with its pros and cons. It discusses biogenesis of exosomes, their functional role in cancer metastasis, both protumorigenic and antitumorigenic, and also their applications in anticancer therapy.

Abstract

Exosomes, the endosome-derived bilayered extracellular nanovesicles with their contribution in many aspects of cancer biology, have become one of the prime foci of research. Exosomes derived from various cells carry cargoes similar to their originator cells and their mode of generation is different compared to other extracellular vesicles. This review has tried to cover all aspects of exosome biogenesis, including cargo, Rab-dependent and Rab-independent secretion of endosomes and exosomal internalization. The bioactive molecules of the tumor-derived exosomes, by virtue of their ubiquitous presence and small size, can migrate to distal parts and propagate oncogenic signaling and epigenetic regulation, modulate tumor microenvironment and facilitate immune escape, tumor progression and drug resistance responsible for cancer progression. Strategies improvised against tumor-derived exosomes include suppression of exosome uptake, modulation of exosomal cargo and removal of exosomes. Apart from the protumorigenic role, exosomal cargoes have been selectively manipulated for diagnosis, immune therapy, vaccine development, RNA therapy, stem cell therapy, drug delivery and reversal of chemoresistance against cancer. However, several challenges, including in-depth knowledge of exosome biogenesis and protein sorting, perfect and pure isolation of exosomes, large-scale production, better loading efficiency, and targeted delivery of exosomes, have to be confronted before the successful implementation of exosomes becomes possible for the diagnosis and therapy of cancer.

Advances in Exosome-Based Drug Delivery and Tumor Targeting: From Tissue Distribution to Intracellular Fate

Exosomes or small extracellular vesicles are considered a new generation of bioinspired-nanoscale drug delivery system (DDS). Endogenous exosomes function as signalosomes since they convey signals via ligands or adhesion molecules located on the exosomal membrane, or packaged inside the exosome. Recently, exosome membrane modification, therapeutic payloads encapsulation, and modulation of in vivo disposition of exosomes have been extensively investigated, among which significant advances have been made to optimize exosome-mediated delivery to solid tumors. Exosomes, specifically tumor cell-derived exosomes, are presumed to have tumor-preferential delivery due to the homotypic features. However, quality attributes that dictate the tissue distribution, cell type-selective uptake, and intracellular payload release of the administered exosomes, as well as the spatiotemporal information regarding exosome fate in vivo, remain to be further investigated. This review summarizes recent advances in developing exosomes as drug delivery platforms with a focus on tumor targeting. The pharmacokinetic features of naive exosomes and factors influencing their intracellular fate are summarized. Recent strategies to improve tumor targeting of exosomes are also reviewed in the context of the biological features of tumor and tumor microenvironment (TME). Selected approaches to augment tumor tissue deposition of exosomes, as well as methods to enhance intracellular payload delivery, are summarized with emphasis on the underlying mechanisms (eg, passive or active targeting, endosomal escape, etc.). In conclusion, this review highlights recently reported tumor-targeting strategies of exosome-based drug delivery, and it's in the hope that multiple approaches might be employed in a synergistic combination in the development of exosome-based cancer therapy.

Exosomes Enhance Adhesion and Osteogenic Differentiation of Initial Bone Marrow Stem Cells on Titanium Surfaces

Successful osseointegration involves the biological behavior of bone marrow stem cells (BMSCs) on an implant surface; however, the role of BMSC-derived extracellular vesicles (EVs)/exosomes in osseointegration is little known. This study aimed to: (i) explore the interaction force between exosomes (Exo) and cells on a titanium surface; (ii) discuss whether the morphology and biological behavior of BMSCs are affected by exosomes; and (iii) preliminarily investigate the mechanism by which exosomes regulate cells on Ti surface. Exosomes secreted by rat BMSCs were collected by ultracentrifugation and analyzed using transmission electron microscopy and nanoparticle tracking analysis. Confocal fluorescence microscopy, scanning electron microscopy, Cell Counting Kit-8 (CCK-8), quantitative real-time polymerase chain reaction techniques, and alkaline phosphatase bioactivity, Alizarin Red staining, and quantification were used to investigate the exosomes that adhere to the Ti plates under different treatments as well as the morphological change, adhesion, spread, and differentiation of BMSCs. We found that exosomes were efficiently internalized and could regulate cell morphology and promoted the adhesion, spreading, and osteogenic differentiation of BMSCs. These were achieved partly by activating the RhoA/ROCK signaling pathway. Our discovery presents a new insight into the positive regulatory effect of exosomes on the biological behaviors of BMSCs on Ti surface and provides a novel route to modify the surface of a Ti implant.

Stellate Plasmonic Exosomes for Penetrative Targeting Tumor NIR-II Thermo-Radiotherapy

Multifunctional gold (Au)-based nanomaterials with high atomic number (symbol Z) and strong absorbance in the second near-infrared window (NIR-II) property are emerging as promising candidates for tumor thermo-radiotherapy. The main limitations of applying Au-based nanomaterials to biomedical studies include the absence of active tumor-targeting ability, penetrating efficiency, and stability. In this study, we present a novel type of tumor cell-derived stellate plasmonic exosomes (TDSP-Exos) for penetrative targeted tumor NIR-II thermo-radiotherapy and photoacoustic imaging. The TDSP-Exos are abundantly and easily produced by the incubation of tumor cells with gold nanostars, based on which gold nanostars promote the exocytosis of exosomes from tumor cells. Compared with bare gold nanostars, the TDSP-Exos exhibit pronounced accumulation in deep tumor tissues and perform well in both PA imaging and NIR-II thermo-radiotherapy against the tumor. Moreover, the TDSP-Exos improve tumor hypoxia to enhanced radiotherapy by NIR-II photothermal therapy. This work indicates that the tumor cell-derived exosomes have the potential to function as a universal carrier of photothermal agents for targeted tumor NIR-II thermo-radiotherapy.

Exosomes as drug carriers for cancer therapy and challenges regarding exosome uptake

With the development of biomedicine, exosomes are rapidly developing as a new therapy for tumors. As biological carriers, exosomes possess biological activity and can transport their contents between cells. The contents are natural or artificially loaded with biomolecules or chemical drugs. Exosomes deliver biomolecules or chemical drugs into the pathological sites of recipient, which can effectively inhibit the progression of tumors. However, the treatments of tumors through the delivery of exosomes are not sufficiently accurate or efficient, and various challenges need to be overcome. Exosomes from different cell sources possess different characteristics, as well as different specificity for various cells. In the future, for the promotion and application of exosomes, it is of great significance to understand how to select appropriate exosomes loaded with biomolecules or chemical drugs for different tumors types, and how to deliver exosomes to recipient cells accurately and efficiently. This review introduces the application and challenges of exosomes as delivery carriers in tumors.