Cancer cell-type tropism is one of crucial determinants for the efficient systemic delivery of cancer cell-derived exosomes to tumor tissues

Targeting of Extracellular Vesicle-Based Therapeutics to the Brain

Extracellular vesicles (EVs) have been explored as promising vehicles for drug delivery. One of the most valuable features of EVs is their ability to cross physiological barriers, particularly the blood-brain barrier (BBB). This significantly enhances the development of EV-based drug delivery systems for the treatment of CNS disorders. The present review focuses on the factors and techniques that contribute to the successful delivery of EV-based therapeutics to the brain. Here, we discuss the major methods of brain targeting which includes the utilization of different administration routes, capitalizing on the biological origins of EVs, and the modification of EVs through the addition of specific ligands on to the surface of EVs. Finally, we discuss the current challenges in large-scale EV production and drug loading while highlighting future perspectives regarding the application of EV-based therapeutics for brain delivery.

Anti-Inflammatory Macrophage-Derived Exosomes Modified With Self-Antigen Peptides for Treatment of Experimental Autoimmune Encephalomyelitis

Current treatments for autoimmune diseases often involve broad-acting immunosuppressants, which carry risks such as infections and malignancies. This study investigates whether exosomes derived from anti-inflammatory macrophages (AE) and decorated with myelin oligodendrocyte glycoprotein (MOG) peptide (AE/M) can induce immune tolerance in autoimmune diseases. Experimental autoimmune encephalomyelitis (EAE), a mouse model for multiple sclerosis, serves as the autoimmune disease model. Exosomes derived from myoblasts or fibroblasts are also modified with MOG peptides for comparison. Unlike their myoblast or fibroblast counterparts, exosomes from anti-inflammatory macrophages demonstrate a targeted capacity toward antigen-presenting cells. Moreover, AE/M uniquely promotes the differentiation of dendritic cells (DC) into a tolerogenic phenotype. When splenocytes are treated with AE/M, an increased population of tolerogenic DC (tolDC) is observed, even under proinflammatory stimuli. Subcutaneous administration of AE/M in the EAE mouse model results in MOG peptide-specific immune tolerance and preserves motor coordination. In contrast to treatments with fibroblast- or myoblast-derived exosomes modified with MOG peptides, AE/M treatment provides complete protection from EAE in mice. These findings highlight the potential of self-antigen modified AE as a versatile and adaptable nanoplatform for the treatment of various autoimmune diseases.

Barcoded Hybrids of Extracellular Vesicles and Lipid Nanoparticles for Multiplexed Analysis of Tissue Distribution

Targeted delivery of therapeutic agents is a persistent challenge in modern medicine. Recent efforts in this area have highlighted the utility of extracellular vesicles (EVs) as drug carriers, given that they naturally occur in bloodstream and tissues, and can be loaded with a wide range of therapeutic molecules. However, biodistribution and tissue tropism of EVs remain difficult to study systematically. Here, a multiplexed approach is developed for simultaneous tracking of EVs from various cell lines within a single in vivo experiment. EVs are used from 16 different cell lines, and through controlled fusion with lipid nanoparticles (LNPs) carrying single-stranded DNA barcodes, uniquely barcoded hybrid EV particle (hEV) library is generated. These hEVs are combined for a multiplexed in vivo biodistribution profiling in mice, and discovered that HAP1-derived hEVs demonstrated lung tropism, suggesting that these hEVs may be used for targeted drug delivery into lung tissue. To examine this possibility further, it is shown that HAP1 hEV loaded with Cre mRNA displayed functional delivery to the lungs. Overall, the barcoded hEV technology enables rapid profiling of biodistribution across EV cell sources, which is poised to improve throughput and extent of EV studies, while reducing the number of animals required for research.

Surface modification of extracellular vesicles with polyoxazolines to enhance their plasma stability and tumor accumulation

Extracellular vesicles (EVs) are future promising therapeutics, but their instability in vivo after administration remains an important barrier to their further development. Many groups evaluated EV surface modification strategies to add a targeting group with the aim of controlling EV biodistribution. Conversely, fewer groups focused on their stabilization to obtain "stealth" allogenic EVs. Modulating their stabilization and biodistribution is an essential prerequisite for their development as nano-therapeutics. Here, we explored polyoxazolines with lipid anchors association to the EV membrane (POxylation as an alternative to PEGylation) to stabilize EVs in plasma and control their biodistribution, while preserving their native properties. We found that this modification maintained and seemed to potentiate the immunomodulatory properties of EVs derived from mesenchymal stem/stromal cells (MSC). Using a radiolabeling protocol to track EVs at a therapeutically relevant concentration in vivo, we demonstrated that POxylation is a promising option to stabilize EVs in plasma because it increased EV half-life by 6 fold at 6 h post-injection. Moreover, EV accumulation in tumors was higher after POxylation than after PEGylation.

Microfluidic post-insertion of polyethylene glycol lipids and KK or RGD high functionality and quality lipids in milk-derived extracellular vesicles

To achieve the desired delivery effect, extracellular vesicles (EVs) must bypass rapid clearance from circulation and exhibit affinity for target cells; however, it is difficult to simultaneously incorporate two materials into EVs. Post-insertion is a general modification method that can be performed by simply mixing different solutions. Previously, we have developed a microfluidic post-insertion method that supported fast and upscaled modification of EVs using KK-modified high-functionality and -quality (HFQ) lipids. Here, we used microfluidic post-insertion to achieve simultaneous incorporation of polyethylene glycol (PEG) lipids and KK or RGD-modified HFQ lipids into milk-derived EVs to avoid uptake from the reticuloendothelial system and increase the uptake into target cells. PEG lipid and HFQ lipids were formulated to produce micelles and subsequently mixed with EV solution using a microfluidic device. Compared to bulk mixing, microfluidic post-insertion showed higher cellular association. Altered cellular association capacities and endocytic pathways indicated simultaneous incorporation. The cellular association of modified EVs can be adjusted by altering the ratio of (EK)4-KK in micelles with slight changes in physicochemical properties. Furthermore, microfluidic post-insertion is also suitable for (SG)5-RGD, which is insoluble in phosphate-buffered saline (PBS). Our results may be valuable for the development and manufacture of functional EVs as drug delivery systems for clinical applications.

Extracellular vesicles versus lipid nanoparticles for the delivery of nucleic acids

Extracellular vesicles (EVs) are increasingly investigated for delivering nucleic acid (NA) therapeutics, leveraging their natural role in transporting NA and protein-based cargo in cell-to-cell signaling. Their synthetic counterparts, lipid nanoparticles (LNPs), have been developed over the past decades as NA carriers, culminating in the approval of several marketed formulations such as patisiran/Onpattro® and the mRNA-1273/BNT162 COVID-19 vaccines. The success of LNPs has sparked efforts to develop innovative technologies to target extrahepatic organs, and to deliver novel therapeutic modalities, such as tools for in vivo gene editing. Fueled by the recent advancements in both fields, this review aims to provide a comprehensive overview of the basic characteristics of EV and LNP-based NA delivery systems, from EV biogenesis to structural properties of LNPs. It addresses the primary challenges encountered in utilizing these nanocarriers from a drug formulation and delivery perspective. Additionally, biodistribution profiles, in vitro and in vivo transfection outcomes, as well as their status in clinical trials are compared. Overall, this review provides insights into promising research avenues and potential dead ends for EV and LNP-based NA delivery systems.

Exosomes for CRISPR-Cas9 Delivery: The Cutting Edge in Genome Editing

Gene mutation correction was challenging until the discovery of clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein (Cas). CRISPR is a new era for genome modification, and this technology has bypassed the limitations of previous methods such as zinc-finger nuclease and transcription activator-like effector nuclease. Currently, this method is becoming the method of choice for gene-editing purposes, especially therapeutic gene editing in diseases such as cardiovascular, neurological, renal, genetic, optical, and stem cell, as well as blood disorders and muscular degeneration. However, finding the optimum delivery system capable of carrying this large complex persists as the main challenge of this technology. Therefore, it would be ideal if the delivery vehicle could direct the introduction of editing functions to specific cells in a multicellular organism. Exosomes are membrane-bound vesicles with high biocompatibility and low immunogenicity; they offer the best and most reliable way to fill the CRISPR/Cas9 system delivery gap. This review presents the current evidence on the molecular mechanisms and challenges of CRISPR/Cas9-mediated genome modification. Also, the role of CRISPR/Cas9 in the development of treatment and diagnosis of numerous disorders, from malignancies to viral infections, has been discussed. Lastly, the focus is on new advances in exosome-delivery technologies that may play a role in CRISPR/Cas9 delivery for future clinical settings.

Rapid increase of MFGE8 secretion from endometrial epithelial cells is an indicator of extracellular vesicle mediated embryo maternal dialogue

Successful embryo implantation relies on synchronized dialog between the embryo and endometrium, and the role of extracellular vesicles (EVs) in facilitating this cross-talk has been recently established. In our previous study, milk fat globule-EGF factor 8 protein (MFGE8) was identified as increasing in receptive endometrial epithelial cells (EECs) in response to trophoblastic EVs. However, the dynamics of MFGE8 protein in this context are not completely understood. Therefore, we examined its expression and secretion in EECs exposed to estrogen, progesterone, and trophoblastic EVs to gain deeper insights into its potential as an indicator of EV-mediated embryo-maternal dialogue. Our findings revealed that MFGE8 secretion is sensitive to estrogen and progesterone, and that trophoblastic EVs stimulate their release in both receptive and non-receptive EECs. Furthermore, trophoblast EV function was dose and time-dependent. Notably, the secretion of MFGE8 increased within a short timeframe of 30 min after addition of EVs, suggesting the possibility of rapid processes such as binding, fusion or internalization of trophoblastic EVs within EECs. Interestingly, MFGE8 released from EECs was associated with EVs, suggesting increased EV secretion from EECs in response to embryonic signals. In conclusion, increased MFGE8 secretion in this embryo implantation model can serve as an indicator of EV-mediated embryo-maternal dialogue.

A Review: Surface Engineering of Lipid-Based Drug Delivery Systems

This review explores the evolution of lipid-based nanoparticles (LBNPs) for drug delivery (DD). Herein, LBNPs are classified into liposomes and cell membrane-based nanoparticles (CMNPs), each with unique advantages and challenges. Conventional LBNPs possess drawbacks such as poor targeting, quick clearance, and limited biocompatibility. One of the possible alternatives to overcome these challenges is surface modification of nanoparticles (NPs) with materials such as polyethylene glycol (PEG), aptamers, antibody fragments, peptides, CD44, hyaluronic acid, folic acid, palmitic acid, and lactoferrin. Thus, the main focus of this review will be on the different surface modifications that enable LBNPs to have beneficial properties for DD, such as enhancing mass transport properties, immune evasion, improved stability, and targeting. Moreover, various CMNPs are explored used for DD derived from cells such as red blood cells (RBCs), platelets, leukocytes, cancer cells, and stem cells, highlighting their unique natural properties (e.g., biocompatibility and ability to evade the immune system). This discussion extends to the biomimicking of hybrid NPs accomplished through the surface coating of synthetic (mainly polymeric) NPs with different cell membranes. This review aims to provide a comprehensive resource for researchers on recent advances in the field of surface modification of LBNPs and CMNPs. Overall, this review provides valuable insights into the dynamic field of lipid-based DD systems.

Extracellular vesicles in cancer: challenges and opportunities for clinical laboratories

Extracellular vesicles (EVs) are nano-sized particles secreted by most cells. They transport different types of biomolecules (nucleic acids, proteins, and lipids) characteristic of their tissue or cellular origin that can mediate long-distance intercellular communication. In the case of cancer, EVs participate in tumor progression by modifying the tumor microenvironment, favoring immune tolerance and metastasis development. Consequently, EVs have great potential in liquid biopsy for cancer diagnosis, prognosis and follow-up. In addition, EVs could have a role in cancer treatment as a targeted drug delivery system. The intense research in the EV field has resulted in hundreds of patents and the creation of biomedical companies. However, methodological issues and heterogeneity in EV composition have hampered the advancement of EV validation trials and the development of EV-based diagnostic and therapeutic products. Consequently, only a few EV biomarkers have moved from research to clinical laboratories, such as the ExoDx Prostate IntelliScore (EPI) test, a CLIA/FDA-approved EV prostate cancer diagnostic test. In addition, the number of large-scale multicenter studies that would clearly define biomarker performance is limited. In this review, we will critically describe the different types of EVs, the methods for their enrichment and characterization, and their biological role in cancer. Then, we will specially focus on the parameters to be considered for the translation of EV biology to the clinic laboratory, the advances already made in the field of EVs related to cancer diagnosis and treatment, and the issues still pending to be solved before EVs could be used as a routine tool in oncology.

Advances in delivery systems for CRISPR/Cas-mediated cancer treatment: a focus on viral vectors and extracellular vesicles

The delivery of CRISPR/Cas systems holds immense potential for revolutionizing cancer treatment, with recent advancements focusing on extracellular vesicles (EVs) and viral vectors. EVs, particularly exosomes, offer promising opportunities for targeted therapy due to their natural cargo transport capabilities. Engineered EVs have shown efficacy in delivering CRISPR/Cas components to tumor cells, resulting in inhibited cancer cell proliferation and enhanced chemotherapy sensitivity. However, challenges such as off-target effects and immune responses remain significant hurdles. Viral vectors, including adeno-associated viruses (AAVs) and adenoviral vectors (AdVs), represent robust delivery platforms for CRISPR/Cas systems. AAVs, known for their safety profile, have already been employed in clinical trials for gene therapy, demonstrating their potential in cancer treatment. AdVs, capable of infecting both dividing and non-dividing cells, offer versatility in CRISPR/Cas delivery for disease modeling and drug discovery. Despite their efficacy, viral vectors present several challenges, including immune responses and off-target effects. Future directions entail refining delivery systems to enhance specificity and minimize adverse effects, heralding personalized and effective CRISPR/Cas-mediated cancer therapies. This article underscores the importance of optimized delivery mechanisms in realizing the full therapeutic potential of CRISPR/Cas technology in oncology. As the field progresses, addressing these challenges will be pivotal for translating CRISPR/Cas-mediated cancer treatments from bench to bedside.

Do extracellular vesicles have specific target cells?; Extracellular vesicle mediated embryo maternal communication

Extracellular vesicles (EVs) serve as messengers for intercellular communication, yet the precise mechanisms by which recipient cells interpret EV messages remain incompletely understood. In this study, we explored how the origin of EVs, their protein cargo, and the recipient cell type influence the cellular response to EVs within an embryo implantation model. We treated two types of EVs to 6 different recipient cell types and expression of zinc finger protein 81 (ZNF81) gene expression in the recipient cells were quantified using quantitative polymerase chain reaction (qPCR). The proteomic contents of the EV cargos were also analyzed. The results showed that downregulation of the ZNF81 gene was a specific cellular response of receptive endometrial epithelial cells to trophoblast derived EVs. Protein cargo analysis revealed that the proteomic profile of EVs depends on their cell of origin and therefore may affect the recipient cell response to EVs. Furthermore, trophoblastic EVs were found to be specifically enriched with transcription factors such as CTNNB1 (catenin beta-1), HDAC2 (histone deacetylase 2), and NOTCH1 (neurogenic locus notch homolog protein 1), which are known regulators of ZNF81 gene expression. The current study provided compelling evidence supporting the existence of EV specificity, where the characteristics of both the EVs and the recipient cell type collectively contribute to regulating EV target specificity. Additionally, EV protein cargo analysis suggested a potential association between transcription factors and the specific functionality of trophoblastic EVs. This in vitro embryo implantation model and ZNF81 read-out provides a unique platform to study EV specific functionality in natural cell-cell communication.

CRISPR/CAS as a Powerful Tool for Human Immunodeficiency Virus Cure: A Review

Despite care and the availability of effective antiretroviral treatment, some human immunodeficiency virus (HIV)-infected individuals suffer from neurocognitive disorders associated with HIV (HAND) that significantly affect their quality of life. The different types of HAND can be divided into asymptomatic neurocognitive impairment, mild neurocognitive disorder, and the most severe form known as HIV-associated dementia. Little is known about the mechanisms of HAND, but it is thought to be related to infection of astrocytes, microglial cells, and macrophages in the human brain. The formation of a viral reservoir that lies dormant as a provirus in resting CD4+ T lymphocytes and in refuge tissues such as the brain contributes significantly to HIV eradication. In recent years, a new set of tools have emerged: the gene editing based on the clustered regularly interspaced palindromic repeats (CRISPR)/Cas9 system, which can alter genome segments by insertion, deletion, and replacement and has great therapeutic potential. This technology has been used in research to treat HIV and appears to offer hope for a possible cure for HIV infection and perhaps prevention of HAND. This approach has the potential to directly impact the quality of life of HIV-infected individuals, which is a very important topic to be known and discussed.

In vitro and in vivo toxicity of thiolated and PEGylated organosilica nanoparticles

This study comprises the comprehensive toxicological assessment of thiolated organosilica nanoparticles (NPs) synthesised from 3-mercaptopropyltrimethoxysilane (MPTS). We investigated the influence of three different types of nanoparticles synthesised from 3-mercaptopropyltrimethoxysilane: the starting thiolated silica (Si-NP-SH) and their derivatives prepared by surface PEGylation with PEG 750 (Si-NP-PEG750) and 5000 Da (Si-NP-PEG5000) on biological subjects from in vitro to in vivo experiments to explore the possible applications of those nanoparticles in biomedical research. As a result of this study, we generated a comprehensive understanding of the toxicological properties of these nanoparticles, including their cytotoxicity in different cell lines, hemolytic properties, in vitro localisation, mucosal irritation properties and biodistribution in BALB/c mice. Our findings indicate that all three types of nanoparticles can be considered safe and have promising prospects for use in biomedical applications. Nanoparticles did not affect the viability of HPF, MCF7, HEK293 and A549 cell lines at low concentrations (up to 100 µg/mL); moreover, they did not cause organ damage to BALB/c mice at concentrations of 10 mg/kg. The outcomes of this study enhance our understanding of the impact of organosilica nanoparticles on health and the environment, which is vital for developing silica nanoparticle-based drug delivery systems and provides opportunities to expand the applications of organosilica nanoparticles.

Role of Exosomal miR-205-5p Cargo in Angiogenesis and Cell Migration

Exosomes or small extracellular vesicles (sEVs) represent a pivotal component in intercellular communication, carrying a diverse array of biomolecules. Several factors can affect sEVs release dynamics, as occurs in hyperglycemia or inflammation. In fact, sEVs release has been associated with the promotion of physio-pathological processes. Among the sEVs cargo, microRNAs play an essential role in cell-to-cell regulation. More concretely, miR-205-5p is related to angiogenesis and cell proliferation. The aim of this study is to understand the specific role of sEVs containing miR-205-5p under high glucose conditions. ARPE-19 cells were cultured with high glucose (HG) for 5 days. sEVs were isolated and characterized. sEVs from ARPE-19 were used for angiogenesis and cell proliferation. HG increased sEVs release but downregulated miR-205-5p cargo expression compared to the control. sEVs from HG-treated ARPE-19 cells promoted tube formation and migration processes. In contrast, miR-205-5p overexpression (by mimic transfection) decreased angiogenesis and cell migration. Our results demonstrate how ARPE-19 cells respond to HG challenge by increasing sEVs with weak miR-205-5p cargo. The absence of this miRNA in sEVs is enough to promote angiogenesis. In contrast, restoring sEVs-miR-205-5p levels decreased it. These findings open new possibilities in sEVs-based therapies containing miR-205-5p against angiogenesis.

Exploring the role of polymers to overcome ongoing challenges in the field of extracellular vesicles

Extracellular vesicles (EVs) are naturally occurring nanoparticles released from all eucaryotic and procaryotic cells. While their role was formerly largely underestimated, EVs are now clearly established as key mediators of intercellular communication. Therefore, these vesicles constitute an attractive topic of study for both basic and applied research with great potential, for example, as a new class of biomarkers, as cell-free therapeutics or as drug delivery systems. However, the complexity and biological origin of EVs sometimes complicate their identification and therapeutic use. Thus, this rapidly expanding research field requires new methods and tools for the production, enrichment, detection, and therapeutic application of EVs. In this review, we have sought to explain how polymer materials actively contributed to overcome some of the limitations associated to EVs. Indeed, thanks to their infinite diversity of composition and properties, polymers can act through a variety of strategies and at different stages of EVs development. Overall, we would like to emphasize the importance of multidisciplinary research involving polymers to address persistent limitations in the field of EVs.

Bioinspired extracellular vesicle-coated silica nanoparticles as selective delivery systems

In recent years, there has been a breakthrough in the integration of artificial nanoplatforms with natural biomaterials for the development of more efficient drug delivery systems. The formulation of bioinspired nanosystems, combining the benefits of synthetic nanoparticles with the natural features of biological materials, provides an efficient strategy to improve nanoparticle circulation time, biocompatibility and specificity toward targeted tissues. Among others biological materials, extracellular vesicles (EVs), membranous structures secreted by many types of cells composed by a protein rich lipid bilayer, have shown a great potential as drug delivery systems themselves and in combination with artificial nanoparticles. The reason for such interest relays on their natural properties, such as overcoming several biological barriers or migration towards specific tissues. Here, we propose the use of mesoporous silica nanoparticles (MSNs) as efficient and versatile nanocarriers in combination with tumor derived extracellular vesicles (EVs) for the development of selective drug delivery systems. The hybrid nanosystems demonstrated selective cellular internalization in parent cells, indicating that the EV targeting capabilities were efficiently transferred to MSNs by the developed coating strategy. As a result, EVs-coated MSNs provided an enhanced and selective intracellular accumulation of doxorubicin and a specific cytotoxic activity against targeted cancer cells, revealing these hybrid nanosystems as promising candidates for the development of targeted treatments.

Understanding of Ovarian Cancer Cell-Derived Exosome Tropism for Future Therapeutic Applications

Exosomes, a subtype of extracellular vesicles, ranging from 50 to 200 nm in diameter, and mediate cell-to-cell communication in normal biological and pathological processes. Exosomes derived from tumors have multiple functions in cancer progression, resistance, and metastasis through cancer exosome-derived tropism. However, there is no quantitative information on cancer exosome-derived tropism. Such data would be highly beneficial to guide cancer therapy by inhibiting exosome release and/or uptake. Using two fluorescent protein (mKate2) transfected ovarian cancer cell lines (OVCA4 and OVCA8), cancer exosome tropism was quantified by measuring the released exosome from ovarian cancer cells and determining the uptake of exosomes into parental ovarian cancer cells, 3D spheroids, and tumors in tumor-bearing mice. The OVCA4 cells release 50 to 200 exosomes per cell, and the OVCA8 cells do 300 to 560 per cell. The uptake of exosomes by parental ovarian cancer cells is many-fold higher than by non-parental cells. In tumor-bearing mice, most exosomes are homing to the parent cancer rather than other tissues. We successfully quantified exosome release and uptake by the parent cancer cells, further proving the tropism of cancer cell-derived exosomes. The results implied that cancer exosome tropism could provide useful information for future cancer therapeutic applications.

The application of extracellular vesicles in colorectal cancer metastasis and drug resistance: recent advances and trends

Colorectal cancer (CRC) has high incidence and mortality rates and is one of the most common cancers of the digestive tract worldwide. Metastasis and drug resistance are the main causes of cancer treatment failure. Studies have recently suggested extracellular vesicles (EVs) as a novel mechanism for intercellular communication. They are vesicular particles, which are secreted and released into biological fluids, such as blood, urine, milk, etc., by a variety of cells and carry numerous biologically active molecules, including proteins, nucleic acids, lipids, metabolites, etc. EVs play a crucial part in the metastasis and drug resistance of CRC by delivering cargo to recipient cells and modulating their behavior. An in-depth exploration of EVs might facilitate a comprehensive understanding of the biological behavior of CRC metastasis and drug resistance, which might provide a basis for developing therapeutic strategies. Therefore, considering the specific biological properties of EVs, researchers have attempted to explore their potential as next-generation delivery systems. On the other hand, EVs have also been demonstrated as biomarkers for the prediction, diagnosis, and presumed prognosis of CRC. This review focuses on the role of EVs in regulating the metastasis and chemoresistance of CRC. Moreover, the clinical applications of EVs are also discussed.

Viral Vectors, Exosomes, and Vexosomes: Potential Armamentarium for Delivering CRISPR/Cas to Cancer Cells

The underlying cause of cancer is genetic disruption, so gene editing technologies, particularly CRISPR/Cas systems can be used to go against cancer. The field of gene therapy has undergone many transitions over its 40-year history. Despite its many successes, it has also suffered many failures in the battle against malignancies, causing really adverse effects instead of therapeutic outcomes. At the tip of this double-edged sword are viral and non-viral-based vectors, which have profoundly transformed the way scientists and clinicians develop therapeutic platforms. Viruses such as lentivirus, adenovirus, and adeno-associated viruses are the most common viral vectors used for delivering the CRISPR/Cas system into human cells. In addition, among non-viral vectors, exosomes, especially tumor-derived exosomes (TDEs), have proven to be quite effective at delivering this gene editing tool. The combined use of viral vectors and exosomes, called vexosomes, seems to be a solution to overcoming the obstacles of both delivery systems.

High therapeutic efficacy of 5-Fluorouracil-loaded exosomes against colon cancer cells

The successful chemotherapeutic regime required for the clinical management of different cancers largely depends on the efficient drug delivery within the cancer cells. Exosomes have emerged as an enticing candidate for exploring their role as delivery vehicles. Exosomes are reported to be intrinsically nanosized vesicles competent for efficient delivery across the cellular membrane. In the present study, we assessed the feasibility of an autologous exosome-based drug delivery platform for delivering 5-Fluorouracil (5-FU) against human colon cancer HCT116 cells. Autologous exosomes have shown probable tropism toward the tumor microenvironment, which makes them the most competitive vehicle for drug delivery. It was observed that the autologous exosomes loaded with 5-FU showed an enhanced rate of drug release under acidic conditions. The result of the cell viability assay showed that treatment of 5-FU-loaded exosomes (equivalent to 5 μg 5-FU) resulted in enhanced cytotoxic effect in HCT116 cells as compared to an equivalent amount of free 5-FU (5 μg), which elucidated the efficient delivery of the 5-FU by exosomes inside the cancer cells. Subsequently, 5-FU-loaded exosomes led to increased nuclear condensation and fragmentation along with increased ROS production. In addition, 5-FU-loaded exosomes caused enhanced dissipation of mitochondrial membrane potential and caspase-3 activation, resulting in increased apoptosis induction. Our study also revealed that 5-FU-loaded exosomes upsurged the arrest in the cell cycle at the G0/G1 stage in HCT-116 cells and it was found to be associated with decreased CDK4 and Cyclin D1 expression concomitantly with the upregulation of CDK inhibitor, p21^Cip1 expression. Thus, the findings from the present study highlight the advantages of autologous exosomes as a natural drug carrier which could efficiently deliver chemotherapeutic drugs to cancer cells.

Emerging role of exosomes in vascular diseases

Exosomes are biological small spherical lipid bilayer vesicles secreted by most cells in the body. Their contents include nucleic acids, proteins, and lipids. Exosomes can transfer material molecules between cells and consequently have a variety of biological functions, participating in disease development while exhibiting potential value as biomarkers and therapeutics. Growing evidence suggests that exosomes are vital mediators of vascular remodeling. Endothelial cells (ECs), vascular smooth muscle cells (VSMCs), inflammatory cells, and adventitial fibroblasts (AFs) can communicate through exosomes; such communication is associated with inflammatory responses, cell migration and proliferation, and cell metabolism, leading to changes in vascular function and structure. Essential hypertension (EH), atherosclerosis (AS), and pulmonary arterial hypertension (PAH) are the most common vascular diseases and are associated with significant vascular remodeling. This paper reviews the latest research progress on the involvement of exosomes in vascular remodeling through intercellular information exchange and provides new ideas for understanding related diseases.

Functionalisation of extracellular vesicles with cyclic-RGDyC potentially for glioblastoma targeted intracellular drug delivery

With the intrinsic ability to cross the blood-brain barrier, small extracellular vesicles (sEVs) hold promise as endogenous brain-targeted drug delivery nano-platforms for glioblastoma (GBM) treatment. To increase GBM targetability, this study aimed to functionalise sEVs with cyclic arginine-glycine-aspartic acid-tyrosine-cysteine (cRGDyC), a ligand for integrin (α_vβ₃) that is overexpressed in GBM cells. Firstly, the intrinsic cellular uptake of sEVs derived from GBM U87 and pancreatic cancer MIA PaCa-2 cells was investigated on the donor cells. To obtain functionalised sEVs (cRGDyC-sEVs), DSPE-mPEG₂₀₀₀-maleimide was incubated with the selected (U87) sEVs, and cRGDyC was subsequently conjugated to the maleimide groups via a thiol-maleimide coupling reaction. The GBM cell targetability and intracellular trafficking of cRGDyC-sEVs were evaluated on U87 cells by fluorescence and confocal microscopy, using unmodified sEVs as a reference. The cytotoxicity of doxorubicin-loaded vesicles (Dox@sEVs, Dox@cRGDyC-sEVs) was compared with a standard liposome formulation (Dox@Liposomes) and free Dox. Both U87 and MIA PaCa-2 cell-derived sEVs displayed tropism with the former being >4.9-fold more efficient to be internalised into U87. Therefore, the U87-derived sEVs were chosen for GBM-targeting. Approximately 4000 DSPE-mPEG₂₀₀₀-maleimide were inserted onto each sEV with cRGDyC conjugated to the maleimide group. The cell targetability of cRGDyC-sEVs to U87 cells improved 2.4-fold than natural sEVs. Despite their proneness to be colocalised with endosomes/lysosomes, both Dox@sEVs and Dox@cRGDyC-sEVs showed superior cytotoxicity to U87 GBM cells compared to Dox@Liposomes, particularly Dox@cRGDyC-sEVs. Overall, U87-derived sEVs were successufully conjugated with cRGDyC via a PEG linker, and cRGDyC-sEVs were demonstrated to be a potnetial integrin-targeting drug delivery vehicle for GBM treatment. Graphic abstract.

Viral vectors and extracellular vesicles: innate delivery systems utilized in CRISPR/Cas-mediated cancer therapy

Gene editing-based therapeutic strategies grant the power to override cell machinery and alter faulty genes contributing to disease development like cancer. Nowadays, the principal tool for gene editing is the clustered regularly interspaced short palindromic repeats-associated nuclease 9 (CRISPR/Cas9) system. In order to bring this gene-editing system from the bench to the bedside, a significant hurdle remains, and that is the delivery of CRISPR/Cas to various target cells in vivo and in vitro. The CRISPR-Cas system can be delivered into mammalian cells using various strategies; among all, we have reviewed recent research around two natural gene delivery systems that have been proven to be compatible with human cells. Herein, we have discussed the advantages and limitations of viral vectors, and extracellular vesicles (EVs) in delivering the CRISPR/Cas system for cancer therapy purposes.

One-Step Pharmaceutical Preparation of PEG-Modified Exosomes Encapsulating Anti-Cancer Drugs by a High-Pressure Homogenization Technique

The use of exosomes encapsulating therapeutic agents for the treatment of diseases is of increasing interest. However, some concerns such as limited efficiency and scalability of conventional drug encapsulation methods to exosomes have still remained; thus, a new approach that enables encapsulation of therapeutic agents with superior efficiency and scalability is required. Herein, we used RAW264 macrophage cell-derived exosomes (RAW-Exos) and demonstrated that high-pressure homogenization (HPH) using a microfluidizer decreased their particle size without changing their morphology, the amount of exosomal marker proteins, and cellular uptake efficiency into RAW264 and colon-26 cancer cells. Moreover, HPH allowed for modification of polyethylene glycol (PEG)-conjugated lipids onto RAW-Exos, as well as encapsulation of the anti-cancer agent doxorubicin. Importantly, the doxorubicin encapsulation efficiency became higher upon increasing the process pressure and simultaneous HPH with PEG-lipids. Moreover, treatment with PEG-modified RAW-Exos encapsulating doxorubicin significantly suppressed tumor growth in colon-26-bearing mice. Taken together, these results suggest that HPH using a microfluidizer could be useful to prepare PEG-modified Exos encapsulating anti-cancer drugs via a one-step pharmaceutical process, and that the prepared functional Exos could be applied for the treatment of cancer in vivo.

Extracellular Vesicles-Based Cell-Cell Communication in Melanoma: New Perspectives in Diagnostics and Therapy

Extracellular vesicles (EVs) are a heterogeneous group of cell-secreted particles that carry cargo of functional biomolecules crucial for cell-to-cell communication with both physiological and pathophysiological consequences. In this review, we focus on evidence demonstrating that the EV-mediated crosstalk between melanoma cells within tumor, between melanoma cells and immune and stromal cells, promotes immune evasion and influences all steps of melanoma development from local progression, pre-metastatic niche formation, to metastatic colonization of distant organs. We also discuss the role of EVs in the development of resistance to immunotherapy and therapy with BRAF^V600/MEK inhibitors, and shortly summarize the recent advances on the potential applications of EVs in melanoma diagnostics and therapy.

A simple approach to re-engineering small extracellular vesicles to circumvent endosome entrapment

Small extracellular vesicles (sEVs) have emerged as attractive drug delivery systems. However, the intracellular release of their cargoes is restricted. This study aimed to develop an efficient approach to re-engineer sEVs by hybridisation with pH-sensitive liposomes (PSLs) and investigate their endosome escape potential. MIA PaCa-2 cell-derived sEVs and PSLs were fused via three methods, and fusion efficiency (FE) was measured using a fluorescence resonance energy transfer assay and nanoparticle tracking analysis. Cellular uptake, intracellular trafficking, and cytotoxicity of doxorubicin-loaded vesicles (Dox@hybrids, Dox@sEVs, and Dox@PSLs) were investigated on MIA PaCa-2 cells. Among the three methods, Ca²⁺-mediated fusion was the simplest and led to a comparable FE with freeze-thaw method, which was significantly higher than PEG₈₀₀₀-mediated fusion. sEVs were more stable after hybridisation with PSLs. Confocal microscopy revealed that the hybrids internalised more efficiently than natural sEVs. While the internalised Dox@sEVs were primarily co-localised with endo/lysosomes even after 8 h, Dox from Dox@hybrids was found to escape from endosomes by 2 h and homogenously distributed in the cytosol before accumulated at nucleus, corresponding to the in vitro pH-responsive release profile. Consequently, Dox@hybrids enhanced cytotoxicity compared with Dox@sEVs, Dox@PSLs, or free drugs. Overall, the biomimetic nanosystem generated by simple Ca²⁺-mediated fusion was more stable and demonstrated higher efficiencies of cellular uptake and endosome escape compared to natural sEVs.

Intraocular RGD-Engineered Exosomes and Active Targeting of Choroidal Neovascularization (CNV)

PURPOSE

To assess the transretinal penetration of intravitreally injected retinal multicell-derived exosomes and to develop exosome-based active targeting of choroidal neovascularization (CNV) by bioengineering with ASL, which is composed of a membrane Anchor (BODIPY), Spacer (PEG), and targeting Ligands (cyclic RGD peptide).

METHODS

Retinal multicell-derived exosomes were recovered from a whole mouse retina using differential ultracentrifugation. Their size, number, and morphology were characterized using nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM). Exosome markers were confirmed using an exosome detection antibody array. Intravitreal injection of fluorescent (PKH-26)-labeled or engineered ASL exosomes (1 × 106 exosomes/μL) were given to the wild-type mouse or laser-induced CNV mouse model. Retinal uptake of exosomes was assessed by in vivo retinal imaging microscopy and histological staining with DAPI, GSA, and anti-integrin αv for retinal sections or choroid/RPE flat mounts. Active targeting of CNV was assessed by comparing retinal uptake between areas with and without CNV and by colocalization analysis of ASL exosomes with integrin αv within CNV. Staining with anti-F4/80, anti-ICAM-1, and anti-GFAP antibodies on retinal sections were performed to identify intracellular uptake of exosomes and immediate reactive retinal gliosis after exosome treatment.

RESULTS

An average of 2.1 × 109 particles/mL with a peak size of 140 nm exosomes were recovered. Rapid retinal penetration of intravitreally injected exosomes was confirmed by retinal imaging microscopy at 3 and 24 h post-injection. Intravitreally delivered PKH-26-labeled exosomes reached inner and outer retinal layers including IPL, INL, OPL, and ONL at 1 and 7 days post-injection. Intravitreally injected ASL exosomes were predominantly delivered to the area of CNV including ONL, RPE, and choroid in laser-induced CNV mouse models with 89.5% of colocalization with integrin αv. Part of exosomes was also taken intracellularly to vascular endothelial cells and macrophages. After intravitreal injection, neither naive exosomes nor ASL exosomes induced immediate reactive gliosis.

CONCLUSIONS

Intravitreally delivered retinal multicell-derived exosomes have good retinal penetration, and ASL modification of exosomes actively targets CNV with no immediate reactive gliosis. ASL exosomes have a great potential to serve as an intraocular drug delivery vehicle, allowing an active targeting strategy.

Insight into Extracellular Vesicle-Cell Communication: From Cell Recognition to Intracellular Fate

Extracellular vesicles (EVs) are heterogamous lipid bilayer-enclosed membranous structures secreted by cells. They are comprised of apoptotic bodies, microvesicles, and exosomes, and carry a range of nucleic acids and proteins that are necessary for cell-to-cell communication via interaction on the cells surface. They initiate intracellular signaling pathways or the transference of cargo molecules, which elicit pleiotropic responses in recipient cells in physiological processes, as well as pathological processes, such as cancer. It is therefore important to understand the molecular means by which EVs are taken up into cells. Accordingly, this review summarizes the underlying mechanisms involved in EV targeting and uptake. The primary method of entry by EVs appears to be endocytosis, where clathrin-mediated, caveolae-dependent, macropinocytotic, phagocytotic, and lipid raft-mediated uptake have been variously described as being prevalent. EV uptake mechanisms may depend on proteins and lipids found on the surfaces of both vesicles and target cells. As EVs have been shown to contribute to cancer growth and progression, further exploration and targeting of the gateways utilized by EVs to internalize into tumor cells may assist in the prevention or deceleration of cancer pathogenesis.

Challenges and directions in studying cell-cell communication by extracellular vesicles

Extracellular vesicles (EVs) are increasingly recognized as important mediators of intercellular communication. They have important roles in numerous physiological and pathological processes, and show considerable promise as novel biomarkers of disease, as therapeutic agents and as drug delivery vehicles. Intriguingly, however, understanding of the cellular and molecular mechanisms that govern the many observed functions of EVs remains far from comprehensive, at least partly due to technical challenges in working with these small messengers. Here, we highlight areas of consensus as well as contentious issues in our understanding of the intracellular and intercellular journey of EVs: from biogenesis, release and dynamics in the extracellular space, to interaction with and uptake by recipient cells. We define knowledge gaps, identify key questions and challenges, and make recommendations on how to address these.

Biomedical application of small extracellular vesicles in cancer treatment

Extracellular vesicles (EVs) are produced by almost all cell types in vivo or in vitro. Among them, exosomes are small nanovesicles with a lipid bilayer, proteins and RNAs actively involved in cellular communication, suggesting that they may be used both as biomarkers and for therapeutic purposes in diseases such as cancer. Moreover, the idea of using them as drug delivery vehicle arises as a promising field of study. Here, we reviewed recent findings showing the importance of EVs, with special focus in exosomes as biomarkers including the most relevant proteins found in different cancer types and it is discussed the FDA approved tests which use exosomes in clinical practice. Finally, we present an overview of the different chimeric EVs developed in the last few years, demonstrating that they can be conjugate to nanoparticles, biomolecules, cancer drugs, etc., and can be developed for a specific cancer treatment. Additionally, we summarized the clinical trials where EVs are used in the treatment of several cancer types aiming to improve the prognosis of these deadly diseases.

Current Strategies for Cancer Cell-Derived Extracellular Vesicles for Cancer Therapy

Cancer cell-derived extracellular vesicles (CEVs), a novel type of therapeutic agent in cancer treatment, can be prepared from the autocrine secretion of various cancer cells, the direct extraction of cancer cells and the combination of cancer cell-derived membranes with advanced materials. With various bioactive molecules, exosomes are produced by cells for intercellular communication. Although cancer cell-derived exosomes are known to inhibit tumor apoptosis and promote the progression of cancer, researchers have developed various innovative strategies to prepare anti-tumor vesicles from cancer cells. With current strategies for anti-tumor vesicles, four different kinds of CEVs are classified including irradiated CEVs, advanced materials combined CEVs, chemotherapeutic drugs loaded CEVs and genetically engineered CEVs. In this way, CEVs can not only be the carriers for anti-tumor drugs to the target tumor area but also act as immune-active agents. Problems raised in the strategies mainly concerned with the preparation, efficacy and application. In this review, we classified and summarized the current strategies for utilizing the anti-tumor potential of CEVs. Additionally, the challenges and the prospects of this novel agent have been discussed.

Special delEVery: Extracellular Vesicles as Promising Delivery Platform to the Brain

The treatment of central nervous system (CNS) pathologies is severely hampered by the presence of tightly regulated CNS barriers that restrict drug delivery to the brain. An increasing amount of data suggests that extracellular vesicles (EVs), i.e., membrane derived vesicles that inherently protect and transfer biological cargoes between cells, naturally cross the CNS barriers. Moreover, EVs can be engineered with targeting ligands to obtain enriched tissue targeting and delivery capacities. In this review, we provide a detailed overview of the literature describing a natural and engineered CNS targeting and therapeutic efficiency of different cell type derived EVs. Hereby, we specifically focus on peripheral administration routes in a broad range of CNS diseases. Furthermore, we underline the potential of research aimed at elucidating the vesicular transport mechanisms across the different CNS barriers. Finally, we elaborate on the practical considerations towards the application of EVs as a brain drug delivery system.

Extracellular Vesicles Tropism: A Comparative Study between Passive Innate Tropism and the Active Engineered Targeting Capability of Lymphocyte-Derived EVs

Cellular communications take place thanks to a well-connected network of chemical–physical signals, biomolecules, growth factors, and vesicular messengers that travel inside or between cells. A deep knowledge of the extracellular vesicle (EV) system allows for a better understanding of the whole series of phenomena responsible for cell proliferation and death. To this purpose, here, a thorough immuno-phenotypic characterization of B-cell EV membranes is presented. Furthermore, the cellular membrane of B lymphocytes, Burkitt lymphoma, and human myeloid leukemic cells were characterized through cytofluorimetry assays and fluorescent microscopy analysis. Through cytotoxicity and internalization tests, the tropism of B lymphocyte-derived EVs was investigated toward the parental cell line and two different cancer cell lines. In this study, an innate capability of passive targeting of the native EVs was distinguished from the active targeting capability of monoclonal antibody-engineered EVs, able to selectively drive the vesicles, enhancing their internalization into the target cancer cells. In particular, the specific targeting ability of anti-CD20 engineered EVs towards Daudi cells, highly expressing CD20 marker on their cell membrane, was proved, while almost no internalization events were observed in HL60 cells, since they did not express an appreciable amount of the CD20 marker on their plasma membranes.

Small extracellular vesicles in cancer

Extracellular vesicles (EV) are lipid-bilayer enclosed vesicles in submicron size that are released from cells. A variety of molecules, including proteins, DNA fragments, RNAs, lipids, and metabolites can be selectively encapsulated into EVs and delivered to nearby and distant recipient cells. In tumors, through such intercellular communication, EVs can regulate initiation, growth, metastasis and invasion of tumors. Recent studies have found that EVs exhibit specific expression patterns which mimic the parental cell, providing a fingerprint for early cancer diagnosis and prognosis as well as monitoring responses to treatment. Accordingly, various EV isolation and detection technologies have been developed for research and diagnostic purposes. Moreover, natural and engineered EVs have also been used as drug delivery nanocarriers, cancer vaccines, cell surface modulators, therapeutic agents and therapeutic targets. Overall, EVs are under intense investigation as they hold promise for pathophysiological and translational discoveries. This comprehensive review examines the latest EV research trends over the last five years, encompassing their roles in cancer pathophysiology, diagnostics and therapeutics. This review aims to examine the full spectrum of tumor-EV studies and provide a comprehensive foundation to enhance the field. The topics which are discussed and scrutinized in this review encompass isolation techniques and how these issues need to be overcome for EV-based diagnostics, EVs and their roles in cancer biology, biomarkers for diagnosis and monitoring, EVs as vaccines, therapeutic targets, and EVs as drug delivery systems. We will also examine the challenges involved in EV research and promote a framework for catalyzing scientific discovery and innovation for tumor-EV-focused research.

Exosomes as Smart Nanoplatforms for Diagnosis and Therapy of Cancer

Exosomes are composed of a lipid bilayer membrane, containing proteins, nucleic acids, DNA, RNA, etc., derived from donor cells. They have a size range of approximately 30-150 nm. The intrinsic characteristics of exosomes, including efficient cellular uptake, low immunogenicity, low toxicity, intrinsic ability to traverse biological barriers, and inherent targeting ability, facilitate their application to the drug delivery system. Here, we review the generation, uptake, separation, and purification methods of exosomes, focusing on their application as carriers in tumor diagnosis and treatment, especially in brain tumors, as well as the patent applications of exosomes in recent years.

Exosomes as Targeted Delivery Platform of CRISPR/Cas9 for Therapeutic Genome Editing

Therapeutic genome editing harnesses the power of genome editing tools to correct erroneous genes associated with disease pathology. To bring the CRISPR/Cas9 tool from the bench to the bedside, a critical hurdle is the safe and efficient delivery of this nucleic acid tool to the desired type of cells in patients. This review discusses the use of natural carriers, extracellular vesicles (EVs), in particular exosomes, to fill the gap. Exosomes are lipid-containing nanovesicle released by various types of cells to mediate cell-cell communications. Their inherent long-distance transportation capability, biocompatibility, and engineerability have made EVs potential vehicles for delivering therapeutic drugs. We summarize the recent progress of harnessing exosomes as delivery vehicles for the CRISPR/Cas system to achieve therapeutic gene editing for disease treatment, with a focus on various strategies to achieve selective delivery to a particular type of cell and efficient packaging of the genome editing tools in the vesicles. Critical issues and possible solutions in the design and engineering of the targeting vehicles are highlighted. Taken together, we demonstrate EV/exosome-mediated packaging of the nucleic acid/protein tools and the cell/tissue-targeted delivery to be a viable way towards the clinical translation of the CRISPR/Cas9 technology.

Extracellular vesicles as a drug delivery system: A systematic review of preclinical studies

During the past decades, extracellular vesicles (EVs) have emerged as an attractive drug delivery system. Here, we assess their pre-clinical applications, in the form of a systematic review. For each study published in the past decade, disease models, animal species, EV donor cell types, active pharmaceutical ingredients (APIs), EV surface modifications, API loading methods, EV size and charge, estimation of EV purity, presence of biodistribution studies and administration routes were quantitatively analyzed in a defined and reproducible way. We have interpreted the trends we observe over the past decade, to define the niches where to apply EVs for drug delivery in the future and to provide a basis for regulatory guidelines.

Docetaxel-loaded exosomes for targeting non-small cell lung cancer: preparation and evaluation in vitro and in vivo

Non-small cell lung cancer (NSCLC) is a highly lethal disease and the majority of NSCLC patients are desperate for therapies that can effectively target their cancer and ultimately improve their overall survival. Docetaxel (DTX) represents the first-line of the antitumor agent that is used to treat NSCLC; however, it has poor solubility in water and unsatisfactory encapsulation efficiency. In our study, exosomes were isolated from A549 cancer cells by ultracentrifugation and then characterized using transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blot (WB). The particle size changes of EXO and EXO-DTX were measured daily for seven days to test the stability. DTX was selected payload by electroporation (EXO-DTX). For the in vitro evaluation, cell proliferation, cell cycle, cell apoptosis, reactive oxygen species (ROS) assay and cellular uptake were evaluated in the A549 cells. Also, this study evaluated the target and therapeutic effect of DTX as an antitumor agent in vivo. As a result, EXO-DTX with a particle size of 149.5 nm were successfully prepared and the cytotoxicity of the EXO-DTX was much greater than that of DTX monomers. Exosomes significantly increased the cellular uptake in vitro evaluation and showed better targeting to tumor tissue compared to the free DTX in the mice. We also explored the potential of tumor cell-derived exosomes as a drug delivery agent to target the parent cancer. Hence, we conclude that exosomes might be used as a potential antitumor drug delivery system (DDS).

Anti-PEG IgM production and accelerated blood clearance phenomenon after the administration of PEGylated exosomes in mice

Recently, there is an increasing interest in exosomes or extracellular vesicles as potential candidates for delivering RNAs, proteins, genes, and anticancer agents. Engineering of exosome properties is rapidly evolving as a means of expanding exosome applications. PEGylation of exosomes is a technique used to improve their in vivo stability, circulation half-lives, and sometimes to allow the binding targeting ligands to the exosome exterior. According to FDA guidelines for the development of PEGylated proteins, immunological responses to PEGylated molecules and particles should be examined. In this study, we prepared PEGylated exosomes and investigated the production of anti-PEG IgM antibodies after single i.v. injections in mice. In addition, we monitored blood concentrations and tumor accumulation of a second dose of PEGylated exosomes administered after the initial dose. Single injections of PEGylated exosomes in mice induced anti-PEG IgM production in a T cell-dependent manner. The anti-PEG IgM production decreased when the injection dose of PEGylated exosomes was further increased. Anti-PEG IgM induced by injection of PEGylated exosomes decreased blood concentrations of a second dose of PEGylated exosomes and suppressed their tumor accumulation in a C26 murine colorectal cancer model. Initial injection doses of either PEGylated liposomes or PEGylated ovalbumin (PEG-OVA), both of them induced anti-PEG IgM production, also decreased the blood concentration of PEGylated exosomes. Interestingly, anti-PEG IgM induced by injection of PEGylated exosomes did not affect the blood concentration of PEG-OVA. These results imply the importance of monitoring anti-PEG IgM when repeat PEGylated exosome doses are required and/or when PEGylated exosomes are used together with other PEGylated therapeutics.

Exosome-Mediated Delivery of the Neuroprotective Peptide PACAP38 Promotes Retinal Ganglion Cell Survival and Axon Regeneration in Rats With Traumatic Optic Neuropathy

Traumatic optic neuropathy (TON) refers to optic nerve damage caused by trauma, leading to partial or complete loss of vision. The primary treatment options, such as hormonal therapy and surgery, have limited efficacy. Pituitary adenylate cyclase-activating polypeptide 38 (PACAP38), a functional endogenous neuroprotective peptide, has emerged as a promising therapeutic agent. In this study, we used rat retinal ganglion cell (RGC) exosomes as nanosized vesicles for the delivery of PACAP38 loaded via the exosomal anchor peptide CP05 (EXO PACAP38 ). EXO PACAP38 showed greater uptake efficiency in vitro and in vivo than PACAP38. The results showed that EXO PACAP38 significantly enhanced the RGC survival rate and retinal nerve fiber layer thickness in a rat TON model. Moreover, EXO PACAP38 significantly promoted axon regeneration and optic nerve function after injury. These findings indicate that EXO PACAP38 can be used as a treatment option and may have therapeutic implications for patients with TON.

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.

M. de Rosales R. Radiolabelling of Extracellular Vesicles for PET and SPECT imaging

Extracellular vesicles (EVs) such as exosomes and microvesicles have gained recent attention as potential biomarkers of disease as well as nanomedicinal tools, but their behaviour in vivo remains mostly unexplored. In order to gain knowledge of their in vivo biodistribution it is important to develop imaging tools that allow us to track EVs over time and at the whole-body level. Radionuclide-based imaging (PET and SPECT) have properties that allow us to do so efficiently, mostly due to their high sensitivity, imaging signal tissue penetration, and accurate quantification. Furthermore, they can be easily translated from animals to humans. In this review, we summarise and discuss the different studies that have used PET or SPECT to study the behaviour of EVs in vivo. With a focus on the different radiolabelling methods used, we also discuss the advantages and disadvantages of each one, and the challenges of imaging EVs due to their variable stability and heterogeneity.

Biofunctional Peptide-Modified Extracellular Vesicles Enable Effective Intracellular Delivery via the Induction of Macropinocytosis

We previously reported that macropinocytosis (accompanied by actin reorganization, ruffling of the plasma membrane, and engulfment of large volumes of extracellular fluid) is an important process for the cellular uptake of extracellular vesicles, exosomes. Accordingly, we developed techniques to induce macropinocytosis by the modification of biofunctional peptides on exosomal membranes, thereby enhancing their cellular uptake. Arginine-rich cell-penetrating peptides have been shown to induce macropinocytosis via proteoglycans; accordingly, we developed peptide-modified exosomes that could actively induce macropinocytotic uptake by cells. In addition, the activation of EGFR induces macropinocytosis; based on this knowledge, we developed artificial leucine-zipper peptide (K4)-modified exosomes. These exosomes can recognize E3 sequence-fused EGFR (E3-EGFR), leading to the clustering and activation of E3-EGFR by coiled-coil formation (E3/K4), which induces cellular exosome uptake by macropinocytosis. In addition, modification of pH-sensitive fusogenic peptides (e.g., GALA) also enhances the cytosolic release of exosomal contents. These experimental techniques and findings using biofunctional peptides have contributed to the development of exosome-based intracellular delivery systems.

Extracellular Vesicle-Based Therapeutics: Preclinical and Clinical Investigations

Drug nanoformulations hold remarkable promise for the efficient delivery of therapeutics to a disease site. Unfortunately, artificial nanocarriers, mostly liposomes and polymeric nanoparticles, show limited applications due to the unfavorable pharmacokinetics and rapid clearance from the blood circulation by the reticuloendothelial system (RES). Besides, many of them have high cytotoxicity, low biodegradability, and the inability to cross biological barriers, including the blood brain barrier. Extracellular vesicles (EVs) are novel candidates for drug delivery systems with high bioavailability, exceptional biocompatibility, and low immunogenicity. They provide a means for intercellular communication and the transmission of bioactive compounds to targeted tissues, cells, and organs. These features have made them increasingly attractive as a therapeutic platform in recent years. However, there are many obstacles to designing EV-based therapeutics. In this review, we will outline the main hurdles and limitations for therapeutic and clinical applications of drug loaded EV formulations and describe various attempts to solve these problems.

Inhibition of Glioma Cells' Proliferation by Doxorubicin-Loaded Exosomes via Microfluidics

Background

Malignant glioma is a fatal brain cancer. Accumulated evidence has demonstrated that exosomes can cross the blood–brain barrier (BBB), suggesting their potential use as drug delivery vehicles to glioma. Therefore, various loading methods of anticancer agents into exosomes have been developed. However, the loading efficiency of anticancer drugs, such as doxorubicin (DOX) and paclitaxel (PTX), into exosomes is relatively low, thus challenging to improve the drug delivery efficiency to glioma cells (GMs) via exosomes.

Methods

To improve the loading efficiency of doxorubicin into exosomes, a microfluidic device (Exo-Load) was developed. Next, to increase the exosomal delivery of doxorubicin to GMs, autologous exosomes were used for its loading via Exo-Load. Briefly, exosomes from SF7761 stem cells-like- and U251-GMs were isolated and characterized by nano-tracking analysis (NTA), transmission electron microscopy (TEM), and immunogold EM. Finally, doxorubicin was successfully loaded into exosomes with saponin by Exo-Load, and the uptake and functionality of doxorubicin-loaded exosomes for parent GMs were evaluated.

Results

The loading efficiency of DOX into SF7761 stem cells-like- and U251-GMs-derived-exosomes were 19.7% and 7.86% via Exo-Load at the injection flow rate of 50 µL/min, respectively. Interestingly, the loading efficiency of DOX into U251 GMs-derived exosomes was significantly improved to 31.98% by a sigmoid type of Exo-Load at the injection flow rate of 12.5 µL/min. Importantly, DOX-loaded GMs-derived exosomes via Exo-Load inhibited parent GMs’ proliferation more than heterologous GMs, supporting exosomes’ homing effect.

Conclusion

This study revealed that DOX and PTX could be loaded in exosomes via Exo-Load, demonstrating that Exo-Load could be a potential drug-loading device into exosomes with further optimization. This study also demonstrated that the delivery of DOX to SF7761 GMs via their daughter exosomes was much more efficient rather than U251 GMs-derived exosomes, supporting that the use of autologous exosomes could be better for glioma drug targeting.

Recent Advances in Extracellular Vesicles as Drug Delivery Systems and Their Potential in Precision Medicine

Extracellular vesicles (EVs) are membrane-bilayered nanoparticles released by most cell types. Recently, an enormous number of studies have been published on the potential of EVs as carriers of therapeutic agents. In contrast to systems such as liposomes, EVs exhibit less immunogenicity and higher engineering potential. Here, we review the most relevant publications addressing the potential and use of EVs as a drug delivery system (DDS). The information is divided based on the key steps for designing an EV-mediated delivery strategy. We discuss possible sources and isolation methods of EVs. We address the administration routes that have been tested in vivo and the tissue distribution observed. We describe the current knowledge on EV clearance, a significant challenge towards enhancing bioavailability. Also, EV-engineering approaches are described as alternatives to improve tissue and cell-specificity. Finally, a summary of the ongoing clinical trials is performed. Although the application of EVs in the clinical practice is still at an early stage, a high number of studies in animals support their potential as DDS. Thus, better treatment options could be designed to precisely increase target specificity and therapeutic efficacy while reducing off-target effects and toxicity according to the individual requirements of each patient.

Exosomes as drug delivery vehicle and contributor of resistance to anticancer drugs

Exosomes are small membranous vesicles implicated in intercellular signalling. Through their uncanny ability to carry and deliver donor cellular cargo (biomolecules) to target cells, they exert a profound effect on the regular functioning of healthy cells and play a significant role in pathogenesis and progression of several diseases, including cancer. The composition and number of endogenously circulating exosomes frequently vary, which is often reflective of the pathophysiological status of the cell. Applicability of exosomes derived from normal cells as a drug carrier with or without modifying their intraluminal and surface components are generally tested. Conversely, exosomes also are reported to contribute to resistance towards several anti-cancer therapies. Therefore, it is necessary to carefully evaluate the role of exosomes in cancer progression, resistance and the potential use of exosomes as a delivery vehicle of cancer therapeutics. In this review, we summarize the recent advancements in the exploitation of exosomes as a drug delivery vehicle. We also discuss the role of exosomes in conferring resistance to anti-cancer therapeutics. While this review is focused on cancer, the exosome-based drug delivery and resistance is also applicable to other human diseases.