The receptor‐binding domain (RBD) of the severe acute respiratory syndrome coronavirus 2 spike (S) protein plays a central role in mediating the first step of virus infection to cause disease: virus binding to angiotensin‐converting enzyme 2 (ACE2) receptors on human host cells Therefore, S/RBD is an ideal target for blocking and neutralization therapies to prevent and treat coronavirus disease 2019 (COVID‐19) Using a target‐based selection approach, we developed oligonucleotide aptamers containing a conserved sequence motif that specifically targets S/RBD Synthetic aptamers had high binding affinity for S/RBD‐coated virus mimics (KD≈7 nM) and also blocked interaction of S/RBD with ACE2 receptors (IC50≈5 nM) Importantly, aptamers were able to neutralize S protein‐expressing viral particles and prevent host cell infection, suggesting a promising COVID‐19 therapy strategy [ABSTRACT FROM AUTHOR] Copyright of Angewandte Chemie is the property of John Wiley & Sons, Inc and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission However, users may print, download, or email articles for individual use This abstract may be abridged No warranty is given about the accuracy of the copy Users should refer to the original published version of the material for the full abstract (Copyright applies to all Abstracts )

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ange.202100345

Neutralizing Aptamers Block S/RBD-ACE2 Interactions and Prevent Host Cell Infection.

Tumor-derived exosomes have emerged as promising cancer biomarkers and attracted increasing interest in non-invasive cancer diagnosis and treatment monitoring. However, the identification and quantification of exosomes in clinical samples such as blood remains challenging due to the difficulty in trade-off between recognition specificity and isolation efficiency. Here we have developed an aptamer-based fluorescence polarization assay for exosome quantification, which is a separation-free, amplification-free and sensitive approach enabling direct quantification of exosomes in human plasma. While the key specificity of this assay is based on the aptamer's inherent affinity to membrane proteins on exosomes, exosomes’ inherent huge mass/volume acts as mass-based fluorescence polarization amplifier. Our assay allows quantitative analysis of exosomes in the range of 5 × 102 to 5 × 105 particles per μL with a detect limitation of 500 particles per μL for the cell line deprived exosomes. The total assay time is about 30 min with just one mix-and-read step to achieve high sensitivity. We have also demonstrated quantification of exosomes from lung cancer patients and healthy donors in clinical samples. This work describes a new and simple liquid biopsy assay to directly detect exosomes in the biological matrix, which facilitates cancer diagnosis and therapy monitoring.

Aptamer-based fluorescence polarization assay for separation-free exosome quantification

Small extracellular vesicles in cancer.

Dysregulated inflammation is a complicated pathological process involved in various diseases, and the treatment of inflammation-linked disorders currently represents an enormous global burden. Extracellular vesicles (EVs) are nanosized, lipid membrane-enclosed vesicles secreted by virtually all types of cells, which act as an important intercellular communicative medium. Considering their capacity to transfer bioactive substances, both unmodified and engineered EVs are increasingly being explored as potential therapeutic agents or therapeutic vehicles. Moreover, as the nature's own delivery tool, EVs possess many desirable advantages, such as stability, biocompatibility, low immunogenicity, low toxicity, and biological barrier permeability. The application of EV-based therapy to combat inflammation, though still in an early stage of development, has profound transformative potential. In this review, we highlight the recent progress in EV engineering for inflammation targeting and modulation, summarize their preclinical applications in the treatment of inflammatory disorders, and present our views on the anti-inflammatory applications of EV-based nanotherapeutics.

Extracellular vesicle-based Nanotherapeutics: Emerging frontiers in anti-inflammatory therapy.

Extracellular vesicles (EVs) hold great promise as therapeutic modalities due to their endogenous characteristics, however, further bioengineering refinement is required to address clinical and commercial limitations. Clinical applications of EV-based therapeutics are being trialed in immunomodulation, tissue regeneration and recovery, and as delivery vectors for combination therapies. Native/biological EVs possess diverse endogenous properties that offer stability and facilitate crossing of biological barriers for delivery of molecular cargo to cells, acting as a form of intercellular communication to regulate function and phenotype. Moreover, EVs are important components of paracrine signaling in stem/progenitor cell-based therapies, are employed as standalone therapies, and can be used as a drug delivery system. Despite remarkable utility of native/biological EVs, they can be improved using bio/engineering approaches to further therapeutic potential. EVs can be engineered to harbor specific pharmaceutical content, enhance their stability, and modify surface epitopes for improved tropism and targeting to cells and tissues in vivo. Limitations currently challenging the full realization of their therapeutic utility include scalability and standardization of generation, molecular characterization for design and regulation, therapeutic potency assessment, and targeted delivery. The fields' utilization of advanced technologies (imaging, quantitative analyses, multi-omics, labeling/live-cell reporters), and utility of biocompatible natural sources for producing EVs (plants, bacteria, milk) will play an important role in overcoming these limitations. Advancements in EV engineering methodologies and design will facilitate the development of EV-based therapeutics, revolutionizing the current pharmaceutical landscape.

/pdf/development-of-extracellular-vesicle-therapeutics-challenges-12mnb7vmn3.pdf

Development of Extracellular Vesicle Therapeutics: Challenges, Considerations, and Opportunities.

In the past decade, the study of exosomes, nanosized vesicles (50-150 nm) released into the extracellular space via the fusion of multivesicular bodies with the plasma membrane, has burgeoned with impressive achievements in theranostics applications. These nanosized vesicles have emerged as key players in homeostasis and in the pathogenesis of diseases owing to the variety of the cargos they can carry, the nature of the molecules packaged inside the vesicles, and the robust interactions between exosomes and target cells or tissues. Accordingly, the development of exosome-based liquid biopsy techniques for early disease detection and for monitoring disease progression marks a new era of precision medicine in the 21st century. Moreover, exosomes possess intrinsic properties - a nanosized structure and unique "homing effects" - that make them outstanding drug delivery vehicles. In addition, targeted exosome-based drug delivery systems can be further optimized using active targeting ligands such as nucleic acid aptamers. Indeed, the aptamers themselves can function as therapeutic and/or diagnostic tools based on their attributes of unique target-binding and non-immunogenicity. This review aims to provide readers with a current picture of the research on exosomes and aptamers and their applications in cancer theranostics, highlighting recent advances in their transition from the bench to the clinic.

/pdf/aptamer-guided-extracellular-vesicle-theranostics-in-xyd2g8n02h.pdf

Aptamer-guided extracellular vesicle theranostics in oncology

Bovine extracellular vesicles contaminate human extracellular vesicles produced in cell culture conditioned medium when 'exosome-depleted serum' is utilised.

Andrew Duan

Papers

Aptamer-guided extracellular vesicle theranostics in oncology

Bovine extracellular vesicles contaminate human extracellular vesicles produced in cell culture conditioned medium when 'exosome-depleted serum' is utilised.