Target-induced proximity ligation triggers recombinase polymerase amplification and transcription-mediated amplification to detect tumor-derived exosomes in nasopharyngeal carcinoma with high sensitivity

Recent achievements in exosomal biomarkers detection by nanomaterials-based optical biosensors - A review

Exosomal biomarkers including tumor-derived exosomes, exosomal surface proteins and exosomal nucleic acids have emerged as one of the most important and general cancer biomarkers in modern biomedical science. These indicators can provide momentous biological information for early diagnosis and treatment of cancer. Recently, numerous studies have been conducted to design biosensors for exosomal biomarkers detection and profiling with high sensitivity and strong applied ability. Among these biosensors, nanomaterial-based optical biosensors are prospective future platforms for rapid and cost-effective detection of exosomal biomarkers. Firstly, we have focused on the progress and advancements in different optical-transducing approaches (Surface-Enhanced Raman Scattering, Surface Plasmon Resonance, Colorimetry, Immunochromatographic assay, Chemiluminescence, Electrochemiluminescence, and fluorescence) for detecting and profiling exosomal biomarkers. Additionally, we have summarized strengths and drawbacks of each strategy. Finally, challenges and future outlooks in developing efficient nanomaterial-based optical biosensor systems for exosomal tumor biomarkers detection have been discussed. The review will exhibit an overview of this field and provide meaningful information for scientific researchers.

Exosome-specific tumor diagnosis via biomedical analysis of exosome-containing microRNA biomarkers

Exosome-containing microRNAs (exomiRs) can be employed as potential biomarkers for tumor diagnosis and have drawn much attention in the past few years. However, the separation of exosomes and the detection of exomiRs are still inconvenient or even difficult to implement. Thus, it is important to develop a simple, accurate, and reliable strategy for the separation of exosomes and the biomedical analysis of exomiRs. Herein, a novel exosome-specific tumor diagnosis strategy was constructed by integrating the rapid magnetic exosome-enrichment platform and the Ru(bpy)32+-polymer amplified electrochemiluminescence (ECL) strategy. This strategy realized the rapid and efficient capture of tumor-derived exosomes through a biological-affinity identification platform of the EpCAM antibody. The biomedical analysis of exomiRs achieved a preferable specificity and high sensitivity of 103 particles. Furthermore, we investigated the performance index for clinical blood samples from tumor patients; the results indicated that the exosome-specific tumor diagnosis strategy readily and consistently responded to exomiRs. These results indicated that the exosome-specific tumor diagnosis strategy provided new opportunities for the sensitive and efficient analysis of tumor-derived exomiRs. This strategy greatly simplified the biomedical analysis process and established the non-destructive detection mode of fluid biopsy for tumors.

Biosensing extracellular vesicles: contribution of biomolecules in affinity-based methods for detection and isolation

Extracellular Vesicles (EVs) are lipid vesicles secreted by cells that allow intercellular communication. They are decorated with surface proteins, which are membrane proteins that can be targeted by biochemical techniques to isolate EVs from background particles. EVs have recently attracted attention for their potential applications as biomarkers for numerous diseases. This review focuses on the contribution of biomolecules used as ligands in affinity-based biosensors for the detection and isolation of EVs. Capturing biological objects like EVs with antibodies is well described in the literature through different biosensing techniques. However, since handling proteins can be challenging due to stability issues, sensors using non-denaturable biomolecules are emerging. DNA aptamers, short DNA fragments that mimic antibody action, are currently being developed and considered as the future of antibody-like ligands. These molecules offer undeniable advantages: unparalleled ease of production, very high stability in air, similar affinity constants to antibodies, and compatibility with many organic solvents. The use of peptides specific to EVs is also an exciting biochemical solution to target EV membrane proteins and complement other probes. These different ligands have been used in several types of biosensors: electrochemical, optical, microfluidic using both generic probes (targeting widely expressed membrane proteins such as the tetraspanins) and specific probes (targeting disease biomarkers such as proteins overexpressed in cancer).

de la Fuente J, Moros M. Nanoparticle-based biosensors for detection of extracellular vesicles in liquid biopsies

Selecting the appropriate nanoparticle, functionalization chemistry and sensing methodology can speed up the translation of liquid biopsies into the clinic.

Sensitive Multicolor Visual Detection of Exosomes via Dual Signal Amplification Strategy of Enzyme-Catalyzed Metallization of Au Nanorods and Hybridization Chain Reaction

Exosomes as nanosized vesicles have been recognized as potential noninvasive biomarkers for early cancer diagnosis. Herein, we presented a sensitive multicolor visual method for exosome detection based on enzyme-induced silver deposition on gold nanorods (Au NRs). To achieve highly sensitive determination of exosomes, hybridization chain reaction (HCR) was employed to introduce more alkaline phosphatase (ALP) for signal amplification. First, exosomes were captured by magnetic bead-labeled CD63 aptamer, and, then, cholesterol-modified DNA probes were spontaneously inserted into the exosomal lipid membrane. The ends of the DNA probes act as the initiator to trigger the HCR for signal amplification. Finally, with the help of HCR, increased sites led to enhanced ALP loading and thus boosted the ascorbic acid generation. Silver ions were reduced by ascorbic acid, and silver shells were formed on Au NRs, giving rise to the blue shift of the longitudinal localized surface plasmon resonance peak. Correspondingly, the concentration of exosomes can be obviously distinguished with naked eyes via the vivid color variation. Due to the dual signal amplification of HCR and metallization of Au NRs, highly sensitive detection for exosomes were realized with detection limits as low as 1.6 × 10² particles/μL by UV-vis spectroscopy and 9 × 10³ particles/μL by naked eyes. Compared to the reported colorimetric methods for exosome quantification, visualization based on plentiful color tonalities is the most captivating merit of our approach, and HCR-induced signal amplification highlights the virtue of the strategy. The applicability of the method was validated by the analysis of clinical samples.

Recent Progress in Isolation and Detection of Extracellular Vesicles for Cancer Diagnostics

Extracellular vesicles (EVs) are emerging as one of the many new and promising biomarkers for liquid biopsy of cancer due to their loading capability of some specific proteins and nucleic acids that are closely associated with cancer states. As such, the isolation and detection of cancer-derived EVs offer important information in noninvasive diagnosis of early-stage cancer and real-time monitoring of cancer development. In light of the importance of EVs, over the last decade, researchers have made remarkable innovations to advance the development of EV isolation and detection methods by taking advantage of microfluidics, biomolecule probes, nanomaterials, surface plasmon, optics, and so on. This review introduces the basic properties of EVs and common cancer-derived EV ingredients, and provides a comprehensive overview of EV isolation and detection strategies, with emphasis on liquid biopsies of EVs for cancer diagnostics.