Mannose-Modified Serum Exosomes for the Elevated Uptake to Murine Dendritic Cells and Lymphatic Accumulation

Optimization of polyethylene glycol shielding and mannose density on the lipid nanoparticles for efficient delivery to macrophages and spleens

This study compared the effects of polyethylene glycol (PEG) shielding and mannose-conjugated ligands density on lipid nanoparticles (LNPs) for intracellular uptake to macrophages in vitro and accumulation in spleens in vivo. Fabricated phosphatidyl serine-incorporated LNPs (sLNPs) was physically decorated with mannose-conjugated DSPE-PEG (DPM) at different DPM/LNP molar ratios achieving the DPM density from 0 to 0.6 PEGs/nm2. We demonstrated that low PEG shielding sLNPs with mannose ligands (sLNP-DPMs) displayed superior uptake to macrophages (RAW 264.7 cells) compared with high PEG shielding sLNP-DPMs in vitro. However, high PEG shielding sLNP-DPMs showed significant spleen accumulation compared with low PEG shielding sLNP-DPMs in vivo after intravenous injection. In particular, high PEG shielding sLNPs coated with DSPE-methoxyPEG (DP) and DPM mixture at DP/DPM molar ratios of 5/5 exhibited greater accumulation in red pulp of spleens than naked sLNPs by 2.7-folds in vivo. These results suggested that the optimal PEG shielding and mannose densities per a particle might be different between in vitro cellular uptake to macrophages and in vivo spleen accumulation after systemic administration. Taken together, precision-tailored LNP-surface modifications achieved through optimization of PEG shielding and mannose density can greatly enhance accumulation of LNPs in red pulp of spleens, which could be applied for the delivery of nucleic acid-based drugs and vaccines to spleens in vivo.

Strategies for Small Extracellular Vesicle-Based Cancer Immunotherapy

Extracellular vesicles (EVs) are lipid bilayer-enclosed vesicles released by cells. EVs encapsulate proteins and nucleic acids of their parental cell and efficiently deliver the cargo to recipient cells. These vesicles act as mediators of intercellular communication and thus play a crucial role in various physiological and pathological processes. Moreover, EVs hold promise for clinical use. They have been explored as drug delivery vehicles, therapeutic agents, and targets for disease diagnosis. In the landscape of cancer research, while strides have been made in EV-focused cancer physiopathology, liquid biopsy, and drug delivery, the exploration of EVs as immunotherapeutic agents may not have seen substantial progress to date. Despite promising findings reported in cell and animal studies, the clinical translation of EV-based cancer immunotherapeutics encounters challenges. Here, we review the existing strategies used in EV-based cancer immunotherapy, aiming to propel the development of this emerging yet crucial field.

Chondroitin sulfate-tocopherol succinate modified exosomes for targeted drug delivery to CD44-positive cancer cells

Exosomes (Exos), natural nanovesicles released by various cell types, show potential as an effective drug delivery platform due to their intrinsic role as transporters of biomolecules between different cells. However, Exos functionalization with targeting ligands is a critical step to enhance their targeting capability, which could be challenging. In this study, Exos were modified to specifically bind to CD44-positive cells by anchoring chondroitin sulfate (CS) to their surface. Exo modification was facilitated with CS conjugation with alpha-tocopherol succinate (TOS) as an anchorage. The modified Exos were utilized for delivering curcumin (Cur) to pancreatic cancer (PC) cells. In vitro Cur release studies revealed that Exos play a crucial role in maintaining Cur within themselves, demonstrating their potential as effective carriers for drug delivery to targeted locations. Notably, Cur loaded into the modified Exos exhibited enhanced cytotoxicity compared to unmodified Exo-Cur. Meanwhile, Exo-Cur-TOS-CS induced apoptosis more effectively in AsPC-1 cells than unmodified Exos (70.2 % versus 56.9 %). It is worth mentioning that with CD44-mediated cancer-specific targeting, Exo-CS enabled increased intracellular accumulation in AsPC-1 cells, showing promise as a targeted platform for cancer therapy. These results confirm that Exo modification has a positive impact on enhancing the therapeutic efficacy and cytotoxicity of drugs.

Exosome: From biology to drug delivery

In recent years, different advancements have been observed in nanosized drug delivery systems. Factors such as stability, safety and targeting efficiency cause hindrances in the clinical translation of these synthetic nanocarriers. Therefore, researchers employed endogenous nanocarriers like exosomes as drug delivery vehicles that have an inherent ability to target more efficiently after appropriate functionalization and show higher biocompatibility and less immunogenicity and facilitate penetration through the biological barriers more quickly than the other available carriers. Exosomes are biologically derived lipid bilayer-enclosed nanosized extracellular vesicles (size ranges from 30 to 150 nm) secreted from both prokaryotic and eukaryotic cells and appears significantly in the extracellular space. These EVs (extracellular vesicles) can exist in different sources, including mammals, plants and microorganisms. Different advanced techniques have been introduced for the isolation of exosomes to overcome the existing barriers present with conventional methods. Extensive research on the application of exosomes in therapeutic delivery for treating various diseases related to central nervous system, bone, cancer, skin, etc. has been employed. Several studies are on different stages of clinical trials, and many exosomes patents have been registered.

Mannose modified targeted immersion vaccine delivery system improves protective immunity against Infectious spleen and kidney necrosis virus in mandarin fish (Siniperca chuatsi)

Vaccination is an effective method to prevent viral diseases. However, the biological barrier prevents the immersion vaccine from achieving the best effect without adding adjuvants and carriers. Researches on the targeted presentation technology of vaccines with nanocarriers are helpful to develop immersion vaccines for fish that can break through biological barriers and play an effective role in fish defense. In our study, functionally modified single-walled carbon nanotubes (SWCNTs) were used as carriers to construct a targeted immersion vaccine (SWCNTs-M-MCP) with mannose modified major capsid protein (MCP) to target antigen-presenting cells (APCs), against iridovirus diseases. After bath immunization, our results showed that SWCNTs-M-MCP induced the presentation process and uptake of APCs, triggering a powerful immune response. Moreover, the highest relative percent survival (RPS) was 81.3% in SWCNTs-M-MCP group, which was only 41.5% in SWCNTs-MCP group. Altogether, this study indicates that the SWCNTs-based targeted immersion vaccine induces strong immune response and provided an effective protection against iridovirus diseases.

Approaches to Characterize and Quantify Extracellular Vesicle Surface Conjugation Efficiency

Extracellular vesicles (EVs) are cell-secreted nanovesicles that play an important role in long-range cell-cell communication. Although EVs pose a promising alternative to cell-based therapy, targeted in vivo delivery still falls short. Many studies have explored the surface modification of EVs to enhance their targeting capabilities. However, to our knowledge, there are no standardized practices to confirm the successful surface modification of EVs or calculate the degree of conjugation on EV surfaces (conjugation efficiency). These pieces of information are essential in the reproducibility of targeted EV therapeutics and the determination of optimized conjugation conditions for EVs to see significant therapeutic effects in vitro and in vivo. This review will discuss the vast array of techniques adopted, technologies developed, and efficiency definitions made by studies that have calculated EV/nanoparticle surface conjugation efficiency and how differences between studies may contribute to differently reported conjugation efficiencies.

Lymphatic distribution considerations for subunit vaccine design and development

Subunit vaccines are an important platform for controlling current and emerging infectious diseases. The lymph nodes are the primary site generating the humoral response and delivery of antigens to these sites is critical to effective immunization. Indeed, the duration of antigen exposure within the lymph node is correlated with the antibody response. While current licensed vaccines are typically given through the intramuscular route, injecting vaccines subcutaneously allows for direct access to lymphatic vessels and therefore can enhance the transfer of antigen to the lymph nodes. However, protein subunit antigen uptake into the lymph nodes is inefficient, and subunit vaccines require adjuvants to stimulate the initial immune response. Therefore, formulation strategies have been developed to enhance the exposure of subunit proteins and adjuvants to the lymph nodes by increasing lymphatic uptake or prolonging the retention at the injection site. Given that lymph node exposure is a crucial consideration in vaccine design, in depth analyses of the pharmacokinetics of antigens and adjuvants should be the focus of future preclinical and clinical studies. This review will provide an overview of formulation strategies for targeting the lymphatics and prolonging antigen exposure and will discuss pharmacokinetic evaluations which can be applied toward vaccine development.

Engineering exosomes to reshape the immune microenvironment in breast cancer: Molecular insights and therapeutic opportunities

BACKGROUND

Breast cancer remains a global health challenge, necessitating innovative therapeutic approaches. Immunomodulation and immunotherapy have emerged as promising strategies for breast cancer treatment. Engineered exosomes are the sort of exosomes modified with surface decoration and internal therapeutic molecules. Through suitable modifications, engineered exosomes exhibit the capability to overcome the limitations associated with traditional therapeutic approaches. This ability opens up novel avenues for the development of more effective, personalized, and minimally invasive interventions.

MAIN BODY

In this comprehensive review, we explore the molecular insights and therapeutic potential of engineered exosomes in breast cancer. We discuss the strategies employed for exosome engineering and delve into their molecular mechanisms in reshaping the immune microenvironment of breast cancer.

CONCLUSIONS

By elucidating the contribution of engineered exosomes to breast cancer immunomodulation, this review underscores the transformative potential of this emerging field for improving breast cancer therapy.

HIGHLIGHTS

Surface modification of exosomes can improve the targeting specificity. The engineered exosome-loaded immunomodulatory cargo regulates the tumour immune microenvironment. Engineered exosomes are involved in the immune regulation of breast cancer.

Immunoactivity of a hybrid membrane biosurface on nanoparticles: enhancing interactions with dendritic cells to augment anti-tumor immune responses

Nano-biointerfaces play a pivotal role in determining the functionality of engineered therapeutic nanoparticles, particularly in the context of designing nanovaccines to effectively activate immune cells for cancer immunotherapy. Unlike involving chemical reactions by conventional surface decorating strategies, cell membrane-coating technology offers a straightforward approach to endow nanoparticles with natural biosurfaces, enabling them to mimic and integrate into the intricate biosystems of the body to interact with specific cells under physiological conditions. In this study, cell membranes, in a hybrid formulation, derived from cancer and activated macrophage cells were found to enhance the interaction of nanoparticles (HMP) with dendritic cells (DCs) and T cells among the mixed immune cells from lymph nodes (LNs), which could be leveraged in the development of nanovaccines for anti-tumor therapy. After loading with an adjuvant (R837), the nanoparticles coated with a hybrid membrane (HMPR) demonstrated effectiveness in priming DCs both in vitro and in vivo, resulting in amplified anti-tumor immune responses compared to those of nanoparticles coated with a single type of membrane or those lacking a membrane coating. The elevated immunoactivity of nanoparticles achieved by incorporating a hybrid membrane biosurface provides us a more profound comprehension of the nano-immune interaction, which may significantly benefit the development of bioactive nanomaterials for advanced therapy.

Physio-chemical Modifications to Re-engineer Small Extracellular Vesicles for Targeted Anticancer Therapeutics Delivery and Imaging

Cancer theranostics developed through nanoengineering applications are essential for targeted oncologic interventions in the new era of personalized and precision medicine. Recently, small extracellular vesicles (sEVs) have emerged as an attractive nanoengineering platform for tumor-directed anticancer therapeutic delivery and imaging of malignant tumors. These natural nanoparticles have multiple advantages over synthetic nanoparticle-based delivery systems, such as intrinsic targeting ability, less immunogenicity, and a prolonged circulation time. Since the inception of sEVs as a viable replacement for liposomes (synthetic nanoparticles) as a drug delivery vehicle, many studies have attempted to further the therapeutic efficacy of sEVs. This article discusses engineering strategies for sEVs using physical and chemical methods to enhance their anticancer therapeutic delivery performance. We review physio-chemical techniques of effective therapeutic loading into sEV, sEV surface engineering for targeted entry of therapeutics, and its cancer environment sensitive release inside the cells/organ. Next, we also discuss the novel hybrid sEV systems developed by a combination of sEVs with lipid and metal nanoparticles to garner each component's benefits while overcoming their drawbacks. The article extensively analyzes multiple sEV labeling techniques developed and investigated for live tracking or imaging sEVs. Finally, we discuss the theranostic potential of engineered sEVs in future cancer care regimens.

Modulation of microglial polarization by sequential targeting surface-engineered exosomes improves therapy for ischemic stroke

Microglia are important cells that act on regulating neuroinflammation and neurofunction after the induction of ischemic stroke (IS). Consequently, the efficient accumulation of drugs within ischemic regions, particularly in microglia, serves as a valuable approach for achieving effective therapy by attenuating microglia-mediated cerebral ischemic injury. In this study, we designed mannose (man)-conjugated luteolin (lut)-loaded platelet-derived exosomes (lut/man-pEXO) as surface engineered multifunctional cascade-delivery drug carriers to target ischemic blood vessels and subsequent microglia to enhance drug accumulation and induce neuroprotection of neurovascular unit (NVU) against IS. The results revealed that as platelets naturally gathered in pathological ischemic cerebral vessels, lut/man-pEXO could bind to platelets and efficiently target ischemic injury sites. Moreover, owing to the selective binding affinity of mannose present in lut/man-pEXO towards the mannose receptor expressed on microglia, lut/man-pEXO exhibited superior microglia-targeting properties, inducing the increased uptake of lut by microglia. As a result, lut/man-pEXO regulated microglia by inhibiting the activation of detrimental M1 and promoting the transition towards the anti-inflammatory type (M2), thus attenuating ischemic damage of NVU by reducing the infarct area, rescuing the damage of blood-brain barrier (BBB) and preventing inflammatory transformation of astrocytes.

Exosomes as Targeted Delivery Drug System: Advances in Exosome Loading, Surface Functionalization and Potential for Clinical Application

Exosomes are subtypes of vesicles secreted by almost all cells and can play an important role in intercellular communication. They contain various proteins, lipids, nucleic acids and other natural substances from their metrocytes. Exosomes are expected to be a new generation of drug delivery systems due to their low immunogenicity, high potential to transfer bioactive substances and biocompatibility. However, exosomes themselves are not highly targeted, it is necessary to develop new surface modification techniques and targeted drug delivery strategies, which are the focus of drug delivery research. In this review, we introduced the biogenesis of exosomes and their role in intercellular communication. We listed various advanced exosome drug-loading techniques. Emphatically, we summarized different exosome surface modification techniques and targeted drug delivery strategies. In addition, we discussed the application of exosomes in vaccines and briefly introduced milk exosomes. Finally, we clarified the clinical application prospects and shortcomings of exosomes.

Current Update of Research on Exosomes in Cancer

Exosomes are vesicles secreted by the plasma membrane of the cells delimited by a lipid bilayer membrane into the extracellular space of the cell. Their release is associated with the disposal mechanism to remove unwanted materials from the cells. Exosomes released from primary tumour sites migrate to other parts of the body to create a metastatic environment for spreading the tumour cells. We have reviewed that exosomes interfere with the tumour progression by (i) promoting angiogenesis, (ii) initiating metastasis, (iii) regulating tumour microenvironment (TME) and inflammation, (iv) modifying energy metabolism, and (v) transferring mutations. We have found that EVs play an important role in inducing tumour drug resistance against anticancer drugs. This review discusses the potential of exosomes to generate a significant therapeutic effect along with improved diagnosis, prognosis, insights on the various research conducted and their significant findings of our interest.

Complete remission of tumors in mice with neoantigen-painted exosomes and anti-PD-1 therapy

Neoantigen-based cancer vaccines are emerging as promising tumor therapies, but enhancement of immunogenicity can further improve therapeutic outcomes. Here, we demonstrate that anchoring different peptide neoantigens on subcutaneously administered serum exosomes promote lymph node homing and dendritic cell uptake, resulting in significantly enhanced antigenicity in vitro and in vivo. Exosomes anchoring of melanoma peptide neoantigens augmented the magnitude and breadth of T cell response in vitro and in vivo, to a greater extent with CD8+ T cell responses. Simultaneous decoration of different peptide neoantigens on serum exosomes induced potent tumor suppression and neoantigen-specific immune responses in mice with melanoma and colon cancer. Complete tumor eradication and sustainable immunological memory were achieved with neoantigen-painted serum exosome vaccines in combination with programmed cell death protein 1 (PD-1) antibodies in mice with colon cancer. Importantly, human serum exosomes loaded with peptide neoantigens elicited significant tumor growth retardation and immune responses in human colon cancer 3-dimensional (3D) multicellular spheroids. Our study demonstrates that serum exosomes direct in vivo localization, increase dendritic cell uptake, and enhance the immunogenicity of antigenic peptides and thus provides a general delivery tool for peptide antigen-based personalized immunotherapy.

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.

Liposome Vaccine for Active Regulation of Cellular and Humoral Immunity

Despite significant progress in vaccine development, especially in the fight against viral infections, many unexplored areas remain including innovative adjuvants, diversification of vaccine formulations, and research into the coordination of humoral and cellular immune mechanisms induced by vaccines. Effective coordination of humoral and cellular immunity is crucial in vaccine design. In this study, we used the spike protein (S) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or ovalbumin (OVA) as antigen models and CpG DNA (an activator of toll-like receptor 9, TLR9) as an adjuvant to prepare a multitargeted liposome (LIPO) vaccine. Once equipped with the ability to target lymph nodes (LN) and the endoplasmic reticulum (ER), the LIPO vaccine significantly enhances the cross-presentation ability of antigen-presenting cells (APCs) for exogenous antigens through the ER-associated protein degradation (ERSD) mechanism. Additionally, the vaccine could fine-tune the efficiency of ER-targeted antigen delivery, actively regulating the presentation of exogenous antigen proteins via the major histocompatibility complex (MHC-I) or MHC-II pathways. Immune data from in vivo mouse experiments indicated that the LIPO vaccine effectively stimulated both humoral and cellular immune responses. Furthermore, it triggers immune protection by establishing a robust and persistent germinal center. Moreover, the multifunctionality of this LIPO vaccine extends to the fields of cancer, viruses, and bacteria, providing insights for skilled vaccine design and improvement.

Exosome engineering for efficient and targeted drug delivery: Current status and future perspective

Exosomes are membrane-bound vesicles that are released by most cells. They carry nucleic acids, cytokines, growth factors, proteins, lipids, and metabolites. They are responsible for inter- and intracellular communications and their role in drug delivery is well defined. Exosomes have great potential for therapeutic applications, but the clinical use is restricted because of limitations in standardized procedures for isolation, purification, and drug delivery. Bioengineering of exosomes could be one approach to achieve standardization and reproducible isolation for clinical use. Exosomes are important transporters for targeted drug delivery because of their small size, stable structure, non-immunogenicity, and non-toxic nature, as well as their ability to carry a wide variety of compounds. These features of exosomes can be enhanced further by bioengineering. In this review, possible exosome bioengineering approaches, their biomedical applications, and targeted drug delivery are discussed.

Prospective applications of extracellular vesicle-based therapies in regenerative medicine: implications for the use of dental stem cell-derived extracellular vesicles

In the 21st century, research on extracellular vesicles (EVs) has made remarkable advancements. Recently, researchers have uncovered the exceptional biological features of EVs, highlighting their prospective use as therapeutic targets, biomarkers, innovative drug delivery systems, and standalone therapeutic agents. Currently, mesenchymal stem cells stand out as the most potent source of EVs for clinical applications in tissue engineering and regenerative medicine. Owing to their accessibility and capability of undergoing numerous differentiation inductions, dental stem cell-derived EVs (DSC-EVs) offer distinct advantages in the field of tissue regeneration. Nonetheless, it is essential to note that unmodified EVs are currently unsuitable for use in the majority of clinical therapeutic scenarios. Considering the high feasibility of engineering EVs, it is imperative to modify these EVs to facilitate the swift translation of theoretical knowledge into clinical practice. The review succinctly presents the known biotherapeutic effects of odontogenic EVs and the underlying mechanisms. Subsequently, the current state of functional cargo loading for engineered EVs is critically discussed. For enhancing EV targeting and in vivo circulation time, the review highlights cutting-edge engineering solutions that may help overcome key obstacles in the clinical application of EV therapeutics. By presenting innovative concepts and strategies, this review aims to pave the way for the adaptation of DSC-EVs in regenerative medicine within clinical settings.

Function and clinical application of exosome-how to improve tumor immunotherapy?

In recent years, immunotherapy has been increasingly used in clinical practice to treat tumors. However, immunotherapy's efficacy varies between tumor types and patient populations, and long-term drug resistance often occurs during treatment. Therefore, it is essential to explore the molecular mechanisms of immunotherapy to improve its efficacy. In this review, we focus on the significance of tumor-derived exosomes in the clinical treatment of tumors and how modifying these exosomes may enhance immune effectiveness. Specifically, we discuss exosome components, such as RNA, lipids, and proteins, and the role of membrane molecules on exosome surfaces. Additionally, we highlight the importance of engineered exosomes for tumor immunotherapy. Our goal is to propose new strategies to improve the efficacy of tumor immunotherapy.

Application of Nano-Delivery Systems in Lymph Nodes for Tumor Immunotherapy

Immunotherapy has become a promising research "hotspot" in cancer treatment. "Soldier" immune cells are not uniform throughout the body; they accumulate mostly in the immune organs such as the spleen and lymph nodes (LNs), etc. The unique structure of LNs provides the microenvironment suitable for the survival, activation, and proliferation of multiple types of immune cells. LNs play an important role in both the initiation of adaptive immunity and the generation of durable anti-tumor responses. Antigens taken up by antigen-presenting cells in peripheral tissues need to migrate with lymphatic fluid to LNs to activate the lymphocytes therein. Meanwhile, the accumulation and retaining of many immune functional compounds in LNs enhance their efficacy significantly. Therefore, LNs have become a key target for tumor immunotherapy. Unfortunately, the nonspecific distribution of the immune drugs in vivo greatly limits the activation and proliferation of immune cells, which leads to unsatisfactory anti-tumor effects. The efficient nano-delivery system to LNs is an effective strategy to maximize the efficacy of immune drugs. Nano-delivery systems have shown beneficial in improving biodistribution and enhancing accumulation in lymphoid tissues, exhibiting powerful and promising prospects for achieving effective delivery to LNs. Herein, the physiological structure and the delivery barriers of LNs were summarized and the factors affecting LNs accumulation were discussed thoroughly. Moreover, developments in nano-delivery systems were reviewed and the transformation prospects of LNs targeting nanocarriers were summarized and discussed.

Surface-Engineered Extracellular Vesicles in Cancer Immunotherapy

Extracellular vesicles (EVs) are lipid bilayer-enclosed bodies secreted by all cell types. EVs carry bioactive materials, such as proteins, lipids, metabolites, and nucleic acids, to communicate and elicit functional alterations and phenotypic changes in the counterpart stromal cells. In cancer, cells secrete EVs to shape a tumor-promoting niche. Tumor-secreted EVs mediate communications with immune cells that determine the fate of anti-tumor therapeutic effectiveness. Surface engineering of EVs has emerged as a promising tool for the modulation of tumor microenvironments for cancer immunotherapy. Modification of EVs' surface with various molecules, such as antibodies, peptides, and proteins, can enhance their targeting specificity, immunogenicity, biodistribution, and pharmacokinetics. The diverse approaches sought for engineering EV surfaces can be categorized as physical, chemical, and genetic engineering strategies. The choice of method depends on the specific application and desired outcome. Each has its advantages and disadvantages. This review lends a bird's-eye view of the recent progress in these approaches with respect to their rational implications in the immunomodulation of tumor microenvironments (TME) from pro-tumorigenic to anti-tumorigenic ones. The strategies for modulating TME using targeted EVs, their advantages, current limitations, and future directions are discussed.

Modification of Extracellular Vesicle Surfaces: An Approach for Targeted Drug Delivery

Extracellular vesicles (EVs) are a promising drug delivery vehicle candidate because of their natural origin and intrinsic function of transporting various molecules between different cells. Several advantages of the EV delivery platform include enhanced permeability and retention effect, efficient interaction with recipient cells, the ability to traverse biological barriers, high biocompatibility, high biodegradability, and low immunogenicity. Furthermore, EV membranes share approximately similar structures and contents to the cell membrane, which allows surface modification of EVs, an approach to enable specific targeting. Enhanced drug accumulation in intended sites and reduced adverse effects of chemotherapeutic drugs are the most prominent effects of targeted drug delivery. In order to improve the targeting ability of EVs, chemical modification and genetic engineering are the most adopted methods to date. Diverse chemical methods are employed to decorate EV surfaces with various ligands such as aptamers, carbohydrates, peptides, vitamins, and antibodies. In this review, we introduce the biogenesis, content, and cellular pathway of natural EVs and further discuss the genetic modification of EVs, and its challenges. Furthermore, we provide a comprehensive deliberation on the various chemical modification methods for improved drug delivery, which are directly related to increasing the therapeutic index.

Pillararenes as Promising Carriers for Drug Delivery

Since their discovery in 2008 by N. Ogoshi and co-authors, pillararenes (PAs) have become popular hosts for molecular recognition and supramolecular chemistry, as well as other practical applications. The most useful property of these fascinating macrocycles is their ability to accommodate reversibly guest molecules of various kinds, including drugs or drug-like molecules, in their highly ordered rigid cavity. The last two features of pillararenes are widely used in various pillararene-based molecular devices and machines, stimuli-responsive supramolecular/host-guest systems, porous/nonporous materials, organic-inorganic hybrid systems, catalysis, and, finally, drug delivery systems. In this review, the most representative and important results on using pillararenes for drug delivery systems for the last decade are presented.

Mannose-modified erythrocyte membrane-encapsulated chitovanic nanoparticles as a DNA vaccine carrier against reticuloendothelial tissue hyperplasia virus

Introduction

The erythrocyte membranes used in nanovaccines include high membrane stability, long circulation life, adaptability and extremely good bio compatibility. Nanoparticles encapsulated by erythrocyte membranes are widely used as ideal drug delivery vehicles because of their high drug loading, long circulation time, and excellent biocompatibility. The mannose modification of delivery materials can help target mannose receptors (MRs) to deliver antigens to antigen-presenting cells (APCs).

Methods

In this study, the antigen gene gp90 of avian reticuloendotheliosis virus (REV) was encapsulated with carboxymethyl chitosan (CS) to obtain CSgp90 nanoparticles, which were coated with mannose-modied fowl erythrocyte membranes to yield CS-gp90@M-M nanoparticles. The physicochemical characterization and immune response of the CS-gp90@M-M nanoparticles were investigated in vitro and in vivo.

Results

CS-gp90@M-M nanoparticles were rapidly phagocytized in vitro by macrophages to induce the production of cytokines and nitric oxide. In vivo, CS-gp90@M-M nanoparticles increased cytokine levels, the CD4+/8+ ratio, REV-specific antibodies in the peripheral blood of chicks, and the mRNA levels of immune-related genes in the spleen and bursa of immunized chicks. CS-gp90@M-M nanoparticles could be targeted to lymphoid organs to prolong the retention time of the nanoparticles at the injection site and lymphatic organs, leading to a strong, sustained immune response. Moreover, the CS-gp90@M-M nano-vaccine showed a lasting immunoprotective effect and improved the body weight of chicks after the challenge.

Conclusion

Overall, CS-gp90@M-M nanoparticles can be used in vaccine designs as an effective delivery carrier with immune response-enhancing effects.

Hybrid exosomes, exosome-like nanovesicles and engineered exosomes for therapeutic applications

Exosomes are endosome-derived nanovesicles involved in cellular communication. They are natural nanocarriers secreted by various cells, making them suitable candidates for diverse drug delivery and therapeutic applications from a material standpoint. They have a phospholipid bilayer decorated with functional molecules and an enclosed parental matrix, which has attracted interest in developing designer/hybrid engineered exosome nanocarriers. The structural versatility of exosomes allows the modification of their original configuration using various methods, including genetic engineering, chemical procedures, physical techniques, and microfluidic technology, to load exosomes with additional cargo for expanded biomedical applications. Exosomes show enormous potential for overcoming the limitations of conventional nanoparticle-based techniques in targeted therapy. This review highlights the exosome sources, characteristics, state of the art in the field of hybrid exosomes, exosome-like nanovesicles and engineered exosomes as potential cargo delivery vehicles for therapeutic applications.

Exosome engineering in cell therapy and drug delivery

Cell-derived exosomes have opened new horizons in modern therapy for advanced drug delivery and therapeutic applications, due to their key features such as low immunogenicity, high physicochemical stability, capacity to penetrate into tissues, and the innate capacity to communicate with other cells over long distances. Exosome-based liquid biopsy has been potentially used for the diagnosis and prognosis of a range of disorders. Exosomes deliver therapeutic agents, including immunological modulators, therapeutic drugs, and antisense oligonucleotides to certain targets, and can be used as vaccines, though their clinical application is still far from reality. Producing exosomes on a large-scale is restricted to their low circulation lifetime, weak targeting capacity, and inappropriate controls, which need to be refined before being implemented in practice. Several bioengineering methods have been used for refining therapeutic applications of exosomes and promoting their effectiveness, on the one hand, and addressing the existing challenges, on the other. In the short run, new diagnostic platforms and emerging therapeutic strategies will further develop exosome engineering and therapeutic potential. This requires a thorough analysis of exosome engineering approaches along with their merits and drawbacks, as outlined in this paper. The present study is a comprehensive review of novel techniques for exosome development in terms of circulation time in the body, targeting capacity, and higher drug loading/delivery efficacies.

Extracellular-Vesicle-Based Drug Delivery Systems for Enhanced Antitumor Therapies through Modulating the Cancer-Immunity Cycle

Although immunotherapy harnessing activity of the immune system against tumors has made great progress, the treatment efficacy remains limited in most cancers. Current anticancer immunotherapy is primarily based on T-cell-mediated cellular immunity, which highly relies on efficiency of triggering the cancer-immunity cycle, namely, tumor antigen release, antigen presentation by antigen presenting cells, T cell activation, recruitment and infiltration of T cells into tumors, and recognition and killing of tumor cells by T cells. Unfortunately, these immunotherapies are restricted by inefficient drug delivery and acting on only a single step of the cancer-immunity cycle. Due to high biocompatibility, low immunogenicity, intrinsic cell targeting, and easy chemical and genetic manipulation, extracellular vesicle (EV)-based drug delivery systems are widely used to amplify anticancer immune responses by serving as an integrated platform for multiple drugs or therapeutic strategies to synergistically activate several steps of cancer-immunity cycle. This review summarizes various mechanisms related to affecting cancer-immunity cycle disorders. Meanwhile, preparation and application of EV-based drug delivery systems in modulating cancer-immunity cycle are introduced, especially in the improvement of T cell recruitment and infiltration into tumors. Finally, opportunities and challenges of EV-based drug delivery systems in translational clinical applications are briefly discussed.

Engineered exosomes for studies in tumor immunology

Exosomes are a type of extracellular vesicle (EV) with diameters of 30-150 nm secreted by most of the cells into the extracellular spaces and can alter the microenvironment through cell-to-cell interactions by fusion with the plasma membrane and subsequent endocytosis and release of the cargo. Because of their biocompatibility, low toxicity and immunogenicity, permeability (even through the blood-brain barrier (BBB)), stability in biological fluids, and ability to accumulate in the lesions with higher specificity, investigators have started making designer's exosomes or engineered exosomes to carry biologically active protein on the surface or inside the exosomes as well as using exosomes to carry drugs, micro RNA, and other products to the site of interest. In this review, we have discussed biogenesis, markers, and contents of various exosomes including exosomes of immune cells. We have also discussed the current methods of making engineered and designer's exosomes as well as the use of engineered exosomes targeting different immune cells in the tumors, stroke, as well as at peripheral blood. Genetic engineering and customizing exosomes create an unlimited opportunity to use in diagnosis and treatment. Very little use has been discovered, and we are far away to reach its limits.

Radiovesicolomics-new approach in medical imaging

This review introduce extracellular vesicles (EVs) to a molecular imaging field. The idea of modern analyses based on the use of omics studies, using high-throughput methods to characterize the molecular content of a single biological system, vesicolomics seems to be the new approach to collect molecular data about EV content, to find novel biomarkers or therapeutic targets. The use of various imaging techniques, including those based on radionuclides as positron emission tomography (PET) or single photon emission computed tomography (SPECT), combining molecular data on EVs, opens up the new space for radiovesicolomics—a new approach to be used in theranostics.

Bioengineering exosomes for treatment of organ ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injury is a leading cause of death worldwide. It arises from blood reflowing after tissue hypoxia induced by ischemia that causes severe damages due to the accumulation of reactive oxygen species and the activation of inflammatory responses. Exosomes are the smallest members of the extracellular vesicles' family, which originate from nearly all eukaryotic cells. Exosomes have a great potential in the treatment of I/R injury either in native or modified forms. Native exosomes are secreted by different cell types, such as stem cells, and contain components such as specific miRNA molecules with tissue protective properties. On the other hand, exosome bioengineering has recently received increased attention in context of current advances in the purification, manipulation, biological characterization, and pharmacological applications. There are various pre-isolation and post-isolation manipulation approaches that can be utilized to increase the circulation half-life of exosomes or the availability of their bioactive cargos in the target site. In this review, the various therapeutic actions of native exosomes in different I/R injury will be discussed first. Exosome bioengineering approaches will then be explained, including pre- and post-isolation manipulation methods, applicability for delivery of bioactive agents to injured tissue, clinical translation issues, and future perspectives.

Recent advances in exosome-mediated nucleic acid delivery for cancer therapy

Cancer is a leading public health problem worldwide. Its treatment remains a daunting challenge, although significant progress has been made in existing treatments in recent years. A large concern is the poor therapeutic effect due to lack of specificity and low bioavailability. Gene therapy has recently emerged as a powerful tool for cancer therapy. However, delivery methods limit its therapeutic effects. Exosomes, a subset of extracellular vesicles secreted by most cells, have the characteristics of good biocompatibility, low toxicity and immunogenicity, and great designability. In the past decades, as therapeutic carriers and diagnostic markers, they have caught extensive attention. This review introduced the characteristics of exosomes, and focused on their applications as delivery carriers in DNA, messenger RNA (mRNA), microRNA (miRNA), small interfering RNA (siRNA), circular RNA (circRNA) and other nucleic acids. Meanwhile, their application in cancer therapy and exosome-based clinical trials were presented and discussed. Through systematic summarization and analysis, the recent advances and current challenges of exosome-mediated nucleic acid delivery for cancer therapy are introduced, which will provide a theoretical basis for the development of nucleic acid drugs.

Targeted Drug Delivery to the Central Nervous System Using Extracellular Vesicles

The blood brain barrier (BBB) maintains the homeostasis of the central nervous system (CNS) and protects the brain from toxic substances present in the circulating blood. However, the impermeability of the BBB to drugs is a hurdle for CNS drug development, which hinders the distribution of the most therapeutic molecules into the brain. Therefore, scientists have been striving to develop safe and effective technologies to advance drug penetration into the CNS with higher targeting properties and lower off-targeting side effects. This review will discuss the limitation of artificial nanomedicine in CNS drug delivery and the use of natural extracellular vesicles (EVs), as therapeutic vehicles to achieve targeted delivery to the CNS. Information on clinical trials regarding CNS targeted drug delivery using EVs is very limited. Thus, this review will also briefly highlight the recent clinical studies on targeted drug delivery in the peripheral nervous system to shed light on potential strategies for CNS drug delivery. Different technologies engaged in pre- and post-isolation have been implemented to further utilize and optimize the natural property of EVs. EVs from various sources have also been applied in the engineering of EVs for CNS targeted drug delivery in vitro and in vivo. Here, the future feasibility of those studies in clinic will be discussed.

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.

New Advances in Exosome-based Targeted Drug Delivery Systems

In recent years, various drug nano-delivery platforms have emerged to enhance drug effectiveness in cancer treatment. However, their successful translation to clinics have been hampered by unwanted side effects, as well as associated toxicity. Therefore, there is an imperative need for drug delivery vehicles capable of surpassing cellular barriers and also efficiently transfer therapeutic payloads to tumor cells. Exosomes, a class of small extracellular vesicles naturally released from all cells, have been exploited as a favorable delivery vehicle due to their natural role in intracellular communication and biocompatibility. In this review, information on exosome biogenesis, contents, forms of isolation and their natural functions is discussed, further complemented with the various successful methodologies for therapeutic payloads encapsulation, including distinct loading approaches. In addition, grafting of molecules to improve pharmacokinetics, tumor homing-ligands, as well as stimuli-responsive elements to enhance cell specificity are also debated. In the end, the current status of clinical-grade exosome-based therapies is outlined.

sEVsRVG selectively delivers antiviral siRNA to fetus brain, inhibits ZIKV infection and mitigates ZIKV-induced microcephaly in mouse model

Zika virus (ZIKV), a flavivirus associated with neurological disorders, constitutes a global health threat. During pregnancy, ZIKV traverses the placenta and causes congenital disease such as microcephaly and Guillain-Barré syndrome in newborns. To develop a specific antiviral therapy against ZIKV-induced microcephaly that could cross placental and blood-brain barriers, we designed targeted small extracellular vesicles (sEVs) encapsulating antiviral siRNA (small interfering RNA) to inhibit ZIKV. The neuro-specific targeting was achieved by engineering EVs membrane protein lamp2b fused with a neuron-specific rabies virus glycoprotein derived peptide (RVG). Intravenous administration of the RVG-engineered sEVs loaded with siRNA (ZIKV-specific siRNA) protected pregnant AG6 mice against vertical transmission of ZIKV. Particularly, sEVs^RVG-siRNA traversed placental and blood-brain barriers and suppressed ZIKV infection in fetal brains. Moreover, sEVs^RVG-siRNA alleviated the neuroinflammation and neurological damage caused by ZIKV in the fetal mouse model. In general, we developed a sEVs-based targeted system of antiviral therapy for brain and fetal brain infections.

Targeting the Gut Mucosal Immune System Using Nanomaterials

The gastrointestinal (GI) tract is one the biggest mucosal surface in the body and one of the primary targets for the delivery of therapeutics, including immunotherapies. GI diseases, including, e.g., inflammatory bowel disease and intestinal infections such as cholera, pose a significant public health burden and are on the rise. Many of these diseases involve inflammatory processes that can be targeted by immune modulatory therapeutics. However, nonspecific targeting of inflammation systemically can lead to significant side effects. This can be avoided by locally targeting therapeutics to the GI tract and its mucosal immune system. In this review, we discuss nanomaterial-based strategies targeting the GI mucosal immune system, including gut-associated lymphoid tissues, tissue resident immune cells, as well as GI lymph nodes, to modulate GI inflammation and disease outcomes, as well as take advantage of some of the primary mechanisms of GI immunity such as oral tolerance.

Exosomes as a New Delivery Vehicle in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a type of chronic relapsing inflammatory disease. The pathogenesis of IBD is still unclear, which may involve environmental factors, genetic factors, intestinal microbiota disorder, and abnormal immune responses. Exosomes (30–150 nm) are found in various body fluids, including blood, saliva, urine, and cerebrospinal fluid. Exosomes mediate intercellular communication and regulate cell biological activity by carrying non-coding RNAs, proteins, and lipids. There is evidence that exosomes are involved in the pathogenesis of IBD. In view of the important roles of exosomes in the pathogenesis of IBD, this work systematically reviews the latest research progress of exosomes in IBD, especially the roles of exosomes as non-coding RNA delivery systems in the pathogenesis of IBD, including a disordered immune response, barrier function, and intestinal microbiota. The review will help to clarify the pathogenesis of IBD and explore new diagnostic markers and therapeutic targets for patients with IBD.

Exosomes Engineering and Their Roles as Therapy Delivery Tools, Therapeutic Targets, and Biomarkers

Exosomes are becoming increasingly important therapeutic biomaterials for use in a variety of therapeutic applications due to their unique characteristics, especially due to the ineffectiveness and cytotoxicity of some existing therapies and synthetic therapeutic nanocarriers. They are highly promising as carriers of drugs, genes, and other therapeutic agents that can be incorporated into their interior or onto their surface through various modification techniques to improve their targeting abilities. In addition, they are biocompatible, safe, and stable. The review focuses on different types of exosomes and methods of their preparation, including the incorporation of different kinds of cargo, especially for drug delivery purposes. In particular, their importance and effectiveness as delivery vehicles of various therapeutic agents for a variety of therapeutic applications, including different diseases and disorders such as cancer treatment, cardiovascular and neurodegenerative diseases, are emphasized. Administration routes of exosomes into the body are also included. A novelty in the article is the emphasis on global companies that are already successfully developing and testing such therapeutic biomaterials, with a focus on the most influential ones. Moreover, a comparison of the advantages and disadvantages of the various methods of exosome production is summarized for the first time.

Virus-Induced CD8+ T-Cell Immunity and Its Exploitation to Contain the SARS-CoV-2 Pandemic

The current battle against Severe Acute Respiratory Syndrome (SARS)-Coronavirus-2 benefits from the worldwide distribution of different vaccine formulations. All anti-SARS-CoV-2 vaccines in use are conceived to induce anti-Spike neutralizing antibodies. However, this strategy still has unresolved issues, the most relevant of which are: (i) the resistance to neutralizing antibodies of emerging SARS-CoV-2 variants and (ii) the waning of neutralizing antibodies. On the other hand, both pre-clinical evidence and clinical evidence support the idea that the immunity sustained by antigen-specific CD8⁺ T lymphocytes can complement and also surrogate the antiviral humoral immunity. As a distinctive feature, anti-SARS-CoV-2 CD8⁺ T-driven immunity maintains its efficacy even in the presence of viral protein mutations. In addition, on the basis of data obtained in survivors of the SARS-CoV epidemic, this immunity is expected to last for several years. In this review, both the mechanisms and role of CD8⁺ T-cell immunity in viral infections, particularly those induced by SARS-CoV and SARS-CoV-2, are analyzed. Moreover, a CD8⁺ T-cell-based vaccine platform relying on in vivo engineered extracellular vesicles is described. When applied to SARS-CoV-2, this strategy was proven to induce a strong immunogenicity, holding great promise for its translation into the clinic.

Fostering "Education": Do Extracellular Vesicles Exploit Their Own Delivery Code?

Extracellular vesicles (EVs), comprising large microvesicles (MVs) and exosomes (EXs), play a key role in intercellular communication, both in physiological and in a wide variety of pathological conditions. However, the education of EV target cells has so far mainly been investigated as a function of EX cargo, while few studies have focused on the characterization of EV surface membrane molecules and the mechanisms that mediate the addressability of specific EVs to different cell types and tissues. Identifying these mechanisms will help fulfill the diagnostic, prognostic, and therapeutic promises fueled by our growing knowledge of EVs. In this review, we first discuss published studies on the presumed EV “delivery code” and on the combinations of the hypothesized EV surface membrane “sender” and “recipient” molecules that may mediate EV targeting in intercellular communication. Then we briefly review the main experimental approaches and techniques, and the bioinformatic tools that can be used to identify and characterize the structure and functional role of EV surface membrane molecules. In the final part, we present innovative techniques and directions for future research that would improve and deepen our understandings of EV-cell targeting.

Emerging Significance and Therapeutic Potential of Extracellular vesicles

Extracellular vesicles (EVs), are membrane-bound vesicles that have many advantages over traditional nanocarriers for drug and gene delivery. Evidence from recent studies indicate that EVs have therapeutic capability with chemical or biological modification. Tumor-derived exosomes (TEXs) were used as a new type of antigens or tumor vaccines in anti-tumor immunotherapy. With superior characteristics, modified EVs were applied to loaded and delivered synthetic drugs, silencing RNA, and microRNA for treatment. Different surface functionalization strategies have been proposed to improve the therapeutic functions of EVs. Appropriately modified EVs for disease intervention provide new avenues for effective clinical treatment strategies. Therefore, this review aimed at elucidating the therapeutic functions of EVs to generate new ideas for treatment and to unlock their hidden potential in translational medicine.

Approaches to surface engineering of extracellular vesicles

Extracellular vesicles (EVs) are cell-derived nanoparticles that are important mediators in intercellular communication. This function makes them auspicious candidates for therapeutic and drug-delivery applications. Among EVs, mammalian cell derived EVs and outer membrane vesicles (OMVs) produced by gram-negative bacteria are the most investigated candidates for pharmaceutical applications. To further optimize their performance and to utilize their natural abilities, researchers have strived to equip EVs with new moieties on their surface while preserving the integrity of the vesicles. The aim of this review is to give a comprehensive overview of techniques that can be used to introduce these moieties to the vesicle surface. Approaches can be classified in regards to whether they take place before or after the isolation of EVs. The producing cells can be subjected to genetic manipulation or metabolic engineering to produce surface modified vesicles or EVs are engineered after their isolation by physical or chemical means. Here, the advantages and disadvantages of these processes and their applicability for the development of EVs as therapeutic agents are discussed.

Cancer-Cell-Derived Hybrid Vesicles from MCF-7 and HeLa Cells for Dual-Homotypic Targeting of Anticancer Drugs

Here, as a proof of concept, hybrid vesicles (VEs) are developed from two types of cancer cells, MCF-7 and HeLa, for the dual targeting of the anticancer drug doxorubicin (Dox) to cancer cells via homotypic interactions. Hybrid VEs with a size of 181.8 ± 28.2 nm and surface charge of -27.8 ± 1.9 mV are successfully prepared by the fusion of MCF-7 and HeLa VEs, as demonstrated by the fluorescence resonance energy transfer assay. The hybrid VEs exhibit enhanced intracellular uptake both in MCF-7 and HeLa cells. Dox-encapsulated hybrid VEs (Dox-hybrid VEs) also exhibit promising anticancer and antiproliferative activities against MCF-7/multidrug-resistant cells and HeLa cells. In addition, compared to free Dox, the Dox-hybrid VEs exhibit low intracellular uptake and reduced cytotoxicity for RAW264.7 cells. Thus, hybrid VEs with dual-targeting activity toward two types of cancer cells may be useful for the specific targeting of anticancer drugs for improved anticancer effects with reduced nonspecific toxicity.

From Exosome Glycobiology to Exosome Glycotechnology, the Role of Natural Occurring Polysaccharides

Exosomes (EXOs) are nano-sized informative shuttles acting as endogenous mediators of cell-to-cell communication. Their innate ability to target specific cells and deliver functional cargo is recently claimed as a promising theranostic strategy. The glycan profile, actively involved in the EXO biogenesis, release, sorting and function, is highly cell type-specific and frequently altered in pathological conditions. Therefore, the modulation of EXO glyco-composition has recently been considered an attractive tool in the design of novel therapeutics. In addition to the available approaches involving conventional glyco-engineering, soft technology is becoming more and more attractive for better exploiting EXO glycan tasks and optimizing EXO delivery platforms. This review, first, explores the main functions of EXO glycans and associates the potential implications of the reported new findings across the nanomedicine applications. The state-of-the-art of the last decade concerning the role of natural polysaccharides—as targeting molecules and in 3D soft structure manufacture matrices—is then analysed and highlighted, as an advancing EXO biofunction toolkit. The promising results, integrating the biopolymers area to the EXO-based bio-nanofabrication and bio-nanotechnology field, lay the foundation for further investigation and offer a new perspective in drug delivery and personalized medicine progress.

Extracellular Nanovesicles: From Intercellular Messengers to Efficient Drug Delivery Systems

Nanosized extracellular vesicles (nEV) are released by all the eukaryotic cells into the extracellular spaces. They serve as crucial mediators of intercellular communication, and their presence has been detected in a variety of body fluids. nEV carry nucleic acids, lipids, proteins, and metabolites from the donor cells and transfer them to the recipient cells in the vicinity or distant locations to cause changes in their biological phenotypes. This very property of nEV makes them a suitable carrier of the drugs for therapeutic applications. The use of nEV as a drug delivery system offers several advantages over synthetic nanoparticles, including biocompatibility, natural targeting ability, and long-term safety. Further, nEV can be isolated from various biological sources, quickly loaded with the drug of choice, and modified to further enhance their utility as targeted drug delivery vehicles. Here we review these aspects of nEV and discuss the parameters that should be kept in mind while choosing the nEV source, drug loading method, and surface modification strategies. We also discuss the challenges associated with the nEV-based drug delivery platforms that must be overcome before realizing their full potential in clinical applications.

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.

Exosomes: Cell-Derived Nanoplatforms for the Delivery of Cancer Therapeutics

Exosomes are cell-secreted nanovesicles that naturally contain biomolecular cargoes such as lipids, proteins, and nucleic acids. Exosomes mediate intercellular communication, enabling the transfer biological signals from the donor cells to the recipient cells. Recently, exosomes are emerging as promising drug delivery vehicles due to their strong stability in blood circulation, high biocompatibility, low immunogenicity, and natural targeting ability. In particular, exosomes derived from specific types of cells can carry endogenous signaling molecules with therapeutic potential for cancer treatment, thus presenting a significant impact on targeted drug delivery and therapy. Furthermore, exosomes can be engineered to display targeting moieties on their surface or to load additional therapeutic agents. Therefore, a comprehensive understanding of exosome biogenesis and the development of efficient exosome engineering techniques will provide new avenues to establish convincing clinical therapeutic strategies based on exosomes. This review focuses on the therapeutic applications of exosomes derived from various cells and the exosome engineering technologies that enable the accurate delivery of various types of cargoes to target cells for cancer therapy.

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.

Folic acid-modified Exosome-PH20 enhances the efficiency of therapy via modulation of the tumor microenvironment and directly inhibits tumor cell metastasis

High accumulation of hyaluronan (HA) in the tumor microenvironment leads to an increase in the interstitial pressure and reduction perfusion of drugs. Furthermore, high molecular-weight (HMW)-HA suppresses M1 macrophage polarization, enhances M2 polarization, and induces immunosuppression. Hyaluronidase treatment have attempted to decrease the quantity of HA in tumors. However, hyaluronidase-driven HA degradation driven accelerates tumor cell metastasis, which is a major cause of mortality in cancer patients. Thus, we designed a novel exosome-based drug delivery system (DDS), named Exos-PH20-FA, using genetic engineering to express human hyaluronidase (PH20) and self-assembly techniques to modify the exosomes with folic acid (FA). Our results show that Exos-PH20-FA degraded HMW-HA to low-molecular-weight (LMW)-HA. Moreover, LMW-HA polarized macrophages to the M1 phenotype and reduced the number of relevant immunosuppressive immunocytes which changed the immune microenvironment from an immunosuppressive to immunosupportive phenotype. Furthermore, we demonstrated Exos-PH20-FA directly reduced hyaluronidase-induced metastasis of tumor cells. This tumor treatment also allowed an enhanced delivery of chemotherapy by tumor-targeting effect with FA modification. Our findings indicate that Exos-PH20-FA improves tumor treatment efficiency and reduces the side effects of hyaluronidase treatment, namely tumor cell metastasis. This all-in-one exosome-based HA targeting DDS maybe a promising treatment that yields more efficient and safer results.

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High molecular-weight hyaluronan is related to tumor progression.

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The degradation of hyaluronan enhance cancer cell migration and metastasis.

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Folic acid can target tumor and inhibit tumor cell migration.

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Exosomes are ideal carriers for chemotherapeutics, folic acid and hyaluronidase.

The "sugar-coated bullets" of cancer: Tumor-derived exosome surface glycosylation from basic knowledge to applications

Scientific interest in exosomes has exploded in recent decades. In 1990 only three articles were published on exosomes, while over 1,700 have already been published half-way into 2020.1 While researchers have shown much interest in exosomes since being discovered in 1981, an appreciation of the potential role of glycans in exosome structure and function has emerged only recently. Glycosylation is one of the most common post-translational modification, which functions in many physiological and pathological aspects of cellular function. Many components of exosomes are heavily glycosylated including proteins, lipids, among others. Thus, glycosylation undoubtedly has a great impact on exosome biosynthesis and function. Despite the importance of glycosylation in exosomes and the recent recognition of them as biomarkers for not only malignancies but also other system dysfunction and disease, the characterization of exosome glycans remains understudied. In this review, we discuss glycosylation patterns of exosomes derived from various tissues, their biological features, and potential for various clinical applications. We highlight state-of-the-art knowledge about the fine structure of exosomes, which will allow researchers to reconstruct them by surface modification. These efforts will likely lead to novel disease-related biomarker discovery, purification tagging, and targeted drug transfer for clinical applications in the future.