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

Single extracellular vesicle research: From cell population to a single cell

Extracellular vesicles (EVs) are secreted by cells with a membrane structure and complex components such as DNA, RNA and proteins. These biomolecules play an important role in cell communication, cell proliferation, cell migration, vascularization, immune response and other physiological and pathological processes. Most current research on EVs focused on populations of EVs. Heterogeneity of EVs is neglected. Considering the heterogeneity of single EVs may offer critical molecular insights into cell-cell interactions, it is necessary to enhance our understanding about molecular characteristics from EVs derived from cell population to a single EV of derived from a single cell. This transformation is expected to provide a new insight into the understanding of cellular biology and the accurate description of the law of disease progress. In this article, we review the current research progress of single EV analysis technology for single EVs derived from cell population (SECP) and discuss its main applications in biological and clinical medicine research. After that, we propose the development direction, main difficulties and application prospect of single EV analysis technology for single EVs derived from single cells (SESC) according to our own research work, to provide new perspectives for the field of EV research.

Size Matters: Curvature and Antigen-Mediated Dual Recognition of Size-Specific Tumor-Derived Exosomes

Accurate identification of tumor-derived exosomes is crucial for advancing cancer diagnosis and therapies. However, distinguishing tumor-derived exosomes is challenging due to the heterogeneity of exosomes, which reflect different sizes and cells of origin. To address this challenge, we introduce the curvature and antigen-mediated proximity ligation assay for tumor-derived exosomes (CAPTURE) strategy, which leverages the size-selective properties of curvature-sensing peptides and specific antigen binding of aptamers. CAPTURE enables highly specific identification and precise quantification of the PD-L1+ exosomes in plasma samples. CAPTURE is proven to be simple, homogeneous, rapid, and highly selective, achieving a 100% specificity in discriminating colorectal cancer (CRC) patients from healthy donors. Overall, the CAPTURE strategy presents a promising avenue for precise and noninvasive cancer diagnosis.

Highly sensitive detection platform-based diagnosis of oesophageal squamous cell carcinoma in China: a multicentre, case-control, diagnostic study

BACKGROUND

Early detection and screening of oesophageal squamous cell carcinoma rely on upper gastrointestinal endoscopy, which is not feasible for population-wide implementation. Tumour marker-based blood tests offer a potential alternative. However, the sensitivity of current clinical protein detection technologies is inadequate for identifying low-abundance circulating tumour biomarkers, leading to poor discrimination between individuals with and without cancer. We aimed to develop a highly sensitive blood test tool to improve detection of oesophageal squamous cell carcinoma.

METHODS

We designed a detection platform named SENSORS and validated its effectiveness by comparing its performance in detecting the selected serological biomarkers MMP13 and SCC against ELISA and electrochemiluminescence immunoassay (ECLIA). We then developed a SENSORS-based oesophageal squamous cell carcinoma adjunct diagnostic system (with potential applications in screening and triage under clinical supervision) to classify individuals with oesophageal squamous cell carcinoma and healthy controls in a retrospective study including participants (cohort I) from Sun Yat-sen University Cancer Center (SYSUCC; Guangzhou, China), Henan Cancer Hospital (HNCH; Zhengzhou, China), and Cancer Hospital of Shantou University Medical College (CHSUMC; Shantou, China). The inclusion criteria were age 18 years or older, pathologically confirmed primary oesophageal squamous cell carcinoma, and no cancer treatments before serum sample collection. Participants without oesophageal-related diseases were recruited from the health examination department as the control group. The SENSORS-based diagnostic system is based on a multivariable logistic regression model that uses the detection values of SENSORS as the input and outputs a risk score for the predicted likelihood of oesophageal squamous cell carcinoma. We further evaluated the clinical utility of the system in an independent prospective multicentre study with different participants selected from the same three institutions. Patients with newly diagnosed oesophageal-related diseases without previous cancer treatment were enrolled. The inclusion criteria for healthy controls were no obvious abnormalities in routine blood and tumour marker tests, no oesophageal-associated diseases, and no history of cancer. Finally, we assessed whether classification could be improved by integrating machine-learning algorithms with the system, which combined baseline clinical characteristics, epidemiological risk factors, and serological tumour marker concentrations. Retrospective SYSUCC cohort I (randomly assigned [7:3] to a training set and an internal validation set) and three prospective validation sets (SYSUCC cohort II [internal validation], HNCH cohort II [external validation], and CHSUMC cohort II [external validation]) were used in this step. Six machine-learning algorithms were compared (the least absolute shrinkage and selector operator regression, ridge regression, random forest, logistic regression, support vector machine, and neural network), and the best-performing algorithm was chosen as the final prediction model. Performance of SENSORS and the SENSORS-based diagnostic system was primarily assessed using accuracy, sensitivity, specificity, and area under the receiver operating characteristic curve (AUC).

FINDINGS

Between Oct 1, 2017, and April 30, 2020, 1051 participants were included in the retrospective study. In the prospective diagnostic study, 924 participants were included from April 2, 2022, to Feb 2, 2023. Compared with ELISA (108·90 pg/mL) and ECLIA (41·79 pg/mL), SENSORS (243·03 fg/mL) showed 448 times and 172 times improvements, respectively. In the three retrospective validation sets, the SENSORS-based diagnostic system achieved AUCs of 0·95 (95% CI 0·90-0·99) in the SYSUCC internal validation set, 0·93 (0·89-0·97) in the HNCH external validation set, and 0·98 (0·97-1·00) in the CHSUMC external validation set, sensitivities of 87·1% (79·3-92·3), 98·6% (94·4-99·8), and 93·5% (88·1-96·7), and specificities of 88·9% (75·2-95·8), 74·6% (61·3-84·6), and 92·1% (81·7-97·0), respectively, successfully distinguishing between patients with oesophageal squamous cell carcinoma and healthy controls. Additionally, in three prospective validation cohorts, it yielded sensitivities of 90·9% (95% CI 86·1-94·2) for SYSUCC, 84·8% (76·1-90·8) for HNCH, and 95·2% (85·6-98·7) for CHSUMC. Of the six machine-learning algorithms compared, the random forest model showed the best performance. A feature selection step identified five features to have the highest performance to predictions (SCC, age, MMP13, CEA, and NSE) and a simplified random forest model using these five features further improved classification, achieving sensitivities of 98·2% (95% CI 93·2-99·7) in the internal validation set from retrospective SYSUCC cohort I, 94·1% (89·9-96·7) in SYSUCC prospective cohort II, 88·6% (80·5-93·7) in HNCH prospective cohort II, and 98·4% (90·2-99·9) in CHSUMC prospective cohort II.

INTERPRETATION

The SENSORS system facilitates highly sensitive detection of oesophageal squamous cell carcinoma tumour biomarkers, overcoming the limitations of detecting low-abundance circulating proteins, and could substantially improve oesophageal squamous cell carcinoma diagnostics. This method could act as a minimally invasive screening tool, potentially reducing the need for unnecessary endoscopies.

FUNDING

The National Key R&D Program of China, the National Natural Science Foundation of China, and the Enterprises Joint Fund-Key Program of Guangdong Province.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

Sensitive and reliable lab-on-paper biosensor for label-free detection of exosomes by electrochemical impedance spectroscopy

A new, sensitive, and cost-effective lab-on-paper-based immunosensor was designed based on electrochemical impedance spectroscopy (EIS) for the detection of exosomes. EIS was selected as the determination method since there was a surface blockage in electron transfer by binding the exosomes to the transducer. Briefly, the carbon working electrode (WE) on the paper electrode (PE) was modified with gold particles (AuPs@PE) and then conjugated with anti-CD9 (Anti-CD9/AuPs@PE) for the detection of exosomes. Variables involved in the biosensor design were optimized with the univariate mode. The developed method presents the limit of detection of  8.7 × 102 exosomes mL-1, which is lower than that of many other available methods under the best conditions. The biosensor was also tested with urine samples from cancer patients with high recoveries. Due to this  a unique, low-cost, biodegradable technology is presented that can directly measure exosomes without labeling them for early cancer or metastasis detection.

Shedding Light on Cellular Secrets: A Review of Advanced Optical Biosensing Techniques for Detecting Extracellular Vesicles with a Special Focus on Cancer Diagnosis

In the relentless pursuit of innovative diagnostic tools for cancer, this review illuminates the cutting-edge realm of extracellular vesicles (EVs) and their biomolecular cargo detection through advanced optical biosensing techniques with a primary emphasis on their significance in cancer diagnosis. From the sophisticated domain of nanomaterials to the precision of surface plasmon resonance, we herein examine the diverse universe of optical biosensors, emphasizing their specified applications in cancer diagnosis. Exploring and understanding the details of EVs, we present innovative applications of enhancing and blending signals, going beyond the limits to sharpen our ability to sense and distinguish with greater sensitivity and specificity. Our special focus on cancer diagnosis underscores the transformative potential of optical biosensors in early detection and personalized medicine. This review aims to help guide researchers, clinicians, and enthusiasts into the captivating domain where light meets cellular secrets, creating innovative opportunities in cancer diagnostics.

Isolation and Enrichment of Extracellular Vesicles with Double-Positive Membrane Protein for Subsequent Biological Studies

The isolation and enrichment of specific extracellular vesicle (EV) subpopulations are essential in the context of precision medicine. However, the current methods predominantly rely on a single-positive marker and are susceptible to interference from soluble proteins or impurities. This limitation represents a significant obstacle to the widespread application of EVs in biological research. Herein, a novel approach that utilizes proximity ligation assay (PLA) and DNA-RNA hybridization are proposed to facilitate the binding of two proteins on the EV membrane in advance enabling the isolation and enrichment of intact EVs with double-positive membrane proteins followed by using functionalized magnetic beads for capture and enzymatic cleavage for isolated EVs release. The isolated subpopulations of EVs can be further utilized for cellular uptake studies, high-throughput small RNA sequencing, and breast cancer diagnosis. Hence, developing and implementing a specialized system for isolating and enriching a specific subpopulation of EVs can enhance basic and clinical research in this field.

Unfolding the Complexity of Exosome-Cellular Interactions on Tumour Immunity and Their Clinical Prospects in Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is an epithelial malignancy situated in the posterolateral nasopharynx. NPC poses grave concerns in Southeast Asia due to its late diagnosis. Together with resistance to standard treatment combining chemo- and radiotherapy, NPC presents high metastatic rates and common recurrence. Despite advancements in immune-checkpoint inhibitors (ICIs) and cytotoxic-T-lymphocytes (CTLs)-based cellular therapy, the exhaustive T cell profile and other signs of immunosuppression within the NPC tumour microenvironment (TME) remain as concerns to immunotherapy response. Exosomes, extracellular vesicles of 30-150 nm in diameter, are increasingly studied and linked to tumourigenesis in oncology. These bilipid-membrane-bound vesicles are packaged with a variety of signalling molecules, mediating cell-cell communications. Within the TME, exosomes can originate from tumour, immune, or stromal cells. Although there are studies on tumour-derived exosomes (TEX) in NPC and their effects on tumour processes like angiogenesis, metastasis, therapeutic resistance, there is a lack of research on their involvement in immune evasion. In this review, we aim to enhance the comprehension of how NPC TEX contribute to cellular immunosuppression. Furthermore, considering the detectability of TEX in bodily fluids, we will also discuss the potential development of TEX-related biomarkers for liquid biopsy in NPC as this could facilitate early diagnosis and prognostication of the disease.

Advances in colorimetric biosensors of exosomes: novel approaches based on natural enzymes and nanozymes

Exosomes are 30-150 nm vesicles derived from diverse cell types, serving as one of the most important biomarkers for early diagnosis and prognosis of diseases. However, the conventional detection method for exosomes faces significant challenges, such as unsatisfactory sensitivity, complicated operation, and the requirement of complicated devices. In recent years, colorimetric exosome biosensors with a visual readout underwent rapid development due to the advances in natural enzyme-based assays and the integration of various types of nanozymes. These synthetic nanomaterials show unique physiochemical properties and catalytic abilities, enabling the construction of exosome colorimetric biosensors with novel principles. This review will illustrate the reaction mechanisms and properties of natural enzymes and nanozymes, followed by a detailed introduction of the recent advances in both types of enzyme-based colorimetric biosensors. A comparison between natural enzymes and nanozymes is made to provide insights into the research that improves the sensitivity and convenience of assays. Finally, the advantages, challenges, and future directions of enzymes as well as exosome colorimetric biosensors are highlighted, aiming at improving the overall performance from different approaches.

Dual-Recognition Triggered Proximity Ligation Combined with a Rolling Circle Amplification Strategy for Analysis of Exosomal Protein-Specific Glycosylation

Exosomal surface glycan reveals the biological function and molecular information on the protein, especially in indicating the pathogenesis of certain diseases through monitoring of specific protein glycosylation accurately. However, in situ and nondestructive measurement techniques for certain Exosomal glycoproteins are still lacking. In this work, combined with on-chip purification, we designed a proximity ligation assay-induced rolling circle amplification (RCA) strategy for highly sensitive identification of Exosomal protein-specific glycosylation based on a couple of proximity probes to target Exosomal protein and the protein-specific glycosylation site. Benefiting from efficient separation, scalable dual-recognition, and proximity-triggered RCA amplification, the proposed strategy could convert different protein-specific glycan levels to prominent changes in absorbance signals, resulting in accurate quantification of specific glycosylated Exosomal protein. When detecting the glycosylated PD-L1 on MDA-MB-231 exosomes and glycosylated PTK7 on HepG2 exosomes, the detection limits were calculated to be as low as 1.04 × 104 and 2.759 × 103 particles/mL, respectively. In addition, we further expand the dual-recognition site to investigate the potential correlation of Exosomal glycosylation with polarization of THP-1 cells toward the tumor-suppressive M1 phenotype. Overall, this strategy provides a universal tool for multiple analyses of diverse protein-specific glycosylated exosomes, exhibiting enormous potential to explore exosome function and search for new early diagnosis markers.

Advanced extracellular vesicle bioinformatic nanomaterials: from enrichment, decoding to clinical diagnostics

Extracellular vesicles (EVs) are membrane nanoarchitectures generated by cells that carry a variety of biomolecules, including DNA, RNA, proteins and metabolites. These characteristics make them attractive as circulating bioinformatic nanocabinets for liquid biopsy. Recent advances on EV biology and biogenesis demonstrate that EVs serve as highly important cellular surrogates involved in a wide range of diseases, opening up new frontiers for modern diagnostics. However, inefficient methods for EV enrichment, as well as low sensitivity of EV bioinformatic decoding technologies, hinder the use of EV nanocabinet for clinical diagnosis. To overcome these challenges, new EV nanotechnology is being actively developed to promote the clinical translation of EV diagnostics. This article aims to present the emerging enrichment strategies and bioinformatic decoding platforms for EV analysis, and their applications as bioinformatic nanomaterials in clinical settings.

A smart TESTER for reliable discrimination of cancer-derived small extracellular vesicles

Cancer-derived small extracellular vesicles (csEVs) are crucial liquid biopsy indicators that reflect the presence and progression of many malignancies. However, reliable discrimination of csEVs remains a great challenge owing to the interference from normal sEVs (nsEVs) and low abundance in the early stages of cancer. In this work, we developed a Two-Elements Selectively Triggered csEVs Recognization (TESTER) strategy for selective identification of csEVs from the complex clinical body fluid samples. This method was based on the MNAzyme-controlled synchronous recognition to EpCAM and CD63 proteins on the membrane of csEVs. Efficient recognition to csEVs via EpCAM aptamer and CD63 aptamer prompted the release of Partzyme A and Partzyme B probes to induce a MNAzyme structure formation, resulting in the cyclic cleavage of substrate chain to produce cascade fluorescence signal amplification. The detection threshold of the developed TESTER approach for csEVs in complicated biological samples was 72 particles μL-1, accomplishing the highly sensitive and selective quantification of csEVs. At the same time, we successfully constructed a new platform for bimolecular simultaneous recognition, which provides a good idea for the construction of bimolecular-activated detection switch in the future.

Signal amplification strategies in biosensing of extracellular vesicles (EVs)

Extracellular vesicles (EVs) are membrane-enclosed vesicles secreted from mammalian cells. EVs act as multicomponent delivery vehicles to carry a wide variety of biological molecular information and participate in intercellular communications. Since elevated levels of EVs are associated with some pathological states such as inflammatory diseases and cancers, probing circulating EVs holds a great potential for early diagnostics. To this end, several detection methods have been developed in which biosensors have attracted great attentions in identification of EVs due to their simple instrumentation, versatile design and portability for point-of-care applications. The concentrations of EVs in bodily fluids are extremely low (i.e. 1-100 per μl) at early stages of a disease, which necessitates the use of signal amplification strategies for EVs detection. In this way, this review presents and discusses various amplification strategies for EVs biosensors based on detection modalities including surface plasmon resonance (SPR), calorimetry, fluorescence, electrochemical and electrochemiluminescence (ECL). In addition, microfluidic systems employed for signal amplification are reviewed and discussed in terms of their design and integration with the detection methods.

Advanced technologies for molecular diagnosis of cancer: State of pre-clinical tumor-derived exosome liquid biopsies

Exosomes are membrane-defined extracellular vesicles (EVs) approximately 40-160 ​nm in diameter that are found in all body fluids including blood, urine, and saliva. They act as important vehicles for intercellular communication between both local and distant cells and can serve as circulating biomarkers for disease diagnosis and prognosis. Exosomes play a key role in tumor metastasis, are abundant in biofluids, and stabilize biomarkers they carry, and thus can improve cancer detection, treatment monitoring, and cancer staging/prognosis. Despite their clinical potential, lack of sensitive/specific biomarkers and sensitive isolation/enrichment and analytical technologies has posed a barrier to clinical translation of exosomes. This review presents a critical overview of technologies now being used to detect tumor-derived exosome (TDE) biomarkers in clinical specimens that have potential for clinical translation.

Nanomaterials assisted exosomes isolation and analysis towards liquid biopsy

Exosomes has attracted tremendous research interests as they are emerging as a new paradigm of liquid biopsy. Although the concentration of exosomes in blood is relatively abundant, there still exists various vesicle-like nanoparticles, such as microvesicles, apoptotic bodies. It's an urgent need to isolate and enrich exosomes from the complex contaminants in biofluid samples. Moreover, the expressing level of exosomal biomarkers varies a lot, which make the sensitive molecular detection of exosomes in high demand. Unfortunately, the efficient isolation and sensitive molecular quantification of exosomes is still a major obstacle hindering the further development and clinical application of exosome-based liquid biopsy. Nanomaterials, with unique physiochemical properties, have been widely used in biosensing and analysis aspects, thus they are thought as powerful tools for effective purification and molecular analysis of exosomes. In this review, we summarized the most recent progresses in nanomaterials assisted exosome isolation and analysis towards liquid biopsy. On the one hand, nanomaterials can be used as capture substrates to afford large binding area and specific affinity to exosomes. Meanwhile, nanomaterials can also be served as promising signal transducers and amplifiers for molecular detection of exosomes. Furthermore, we also pointed out several potential and promising research directions in nanomaterials assisted exosome analysis. It's envisioned that this review will give the audience a complete outline of nanomaterials in exosome study, and further promote the intersection of nanotechnology and bio-analysis.

Ultrasensitive and preprocessing-free electrochemical biosensing platform for the detection of cancer-derived exosomes based on spiky-shaped aptamer-magnetic beads

Cancer-derived exosomes, as liquid biopsy markers, have been shown to play an important role in the early screening, diagnosis, and prognosis of cancer. However, existing detection methods have shortcomings such as long-time consumption and low sensitivity. Herein, a sandwich-type electrochemical sensing platform based on Prussian blue/graphene oxide (GO/PB) and spiky Au@Fe₃O₄ nanoparticles was successfully designed and constructed to detect tumor-derived exosomes with high sensitivity and no preprocessing. In this strategy, nanospike structures were introduced on magnetic beads to form spiky Au@Fe₃O₄, which was used to enrich exosomes from serum, avoiding the extraction and purification processes of previous detections. The enrichment and signal amplification of spiky Au@Fe₃O₄ could also greatly improve the detection sensitivity of the sensing platform. Consequently, the concentration of exosomes could be directly quantified by monitoring the electroactive molecules of PB. Therefore, the limit of detection (LOD) of the proposed biosensor was 80 particles·μL^-1. Furthermore, this proposed biosensor could realize the high sensitivity analysis of exosomes and effectively save detection time, and provide an effective assistant diagnostic tool for the early diagnosis of cancer.

Future of Digital Assays to Resolve Clinical Heterogeneity of Single Extracellular Vesicles

Extracellular vesicles (EVs) are complex lipid membrane vehicles with variable expressions of molecular cargo, composed of diverse subpopulations that participate in the intercellular signaling of biological responses in disease. EV-based liquid biopsies demonstrate invaluable clinical potential for overhauling current practices of disease management. Yet, EV heterogeneity is a major needle-in-a-haystack challenge to translate their use into clinical practice. In this review, existing digital assays will be discussed to analyze EVs at a single vesicle resolution, and future opportunities to optimize the throughput, multiplexing, and sensitivity of current digital EV assays will be highlighted. Furthermore, this review will outline the challenges and opportunities that impact the clinical translation of single EV technologies for disease diagnostics and treatment monitoring.

Noninvasive Diagnosis of Nasopharyngeal Carcinoma Based on Phenotypic Profiling of Viral and Tumor Markers on Plasma Extracellular Vesicles

Nasopharyngeal carcinoma (NPC) is a malignant tumor commonly associated with Epstein-Barr virus (EBV) infection, and its early diagnosis as well as its differentiation from nasopharyngitis (NPG) remains challenging due to the insufficient sensitivity of routine screening methods in clinical practice. To date, circulating extracellular vesicles (EVs, 40-1000 nm) have shown appealing potential in liquid biopsy for cancer diagnosis and prognosis. Herein, nanoflow cytometry (nFCM) capable of single EV analysis was applied to examine the expression of surface proteins with very low copy numbers on individual EVs as small as 40 nm. The particle concentrations of five EV subsets exposing EBV-encoded latent membrane proteins (LMP1 and LMP2A) and tumor markers (PD-L1, EGFR, and EpCAM) in plasma were determined rapidly via single-particle enumeration. We identified a five-marker panel named EV^SUM5 (an unweighted sum of the concentration of the five individual EV subsets) that significantly surpassed the traditional VCA-IgA assay in discriminating NPC patients from both healthy donors and NPG patients with accuracies of 96.3 and 83.1%, respectively. Moreover, EV^SUM2 (an unweighted sum of virus-specific LMP1- and LMP2A-positive EVs) could achieve the diagnosis of NPG with an accuracy of 82.6%. Collectively, the work presented a rapid, reliable, and noninvasive method as well as two diagnostic markers to help more accurately differentiate NPC from NPG patients and healthy donors in clinical practice.

Current Status, Opportunities, and Challenges of Exosomes in Oral Cancer Diagnosis and Treatment

Oral cancer is one of the most common cancers in the world, with more than 300,000 cases diagnosed each year, of which oral squamous cell carcinoma accounts for more than 90%, with a 5-year survival rate of only 40–60%, and poor prognosis. Exploring new strategies for the early diagnosis and treatment of oral cancer is key to improving the survival rate. Exosomes are nanoscale lipid bilayer membrane vesicles that are secreted by almost all cell types. During the development of oral cancer, exosomes can transport their contents (DNA, RNA, proteins, etc) to target cells and promote or inhibit the proliferation, invasion, and metastasis of oral cancer cells by influencing the host immune response, drug-resistant metastasis, and tumour angiogenesis. Therefore, exosomes have great potential and advantages as biomarkers for oral cancer diagnosis, and as drug delivery vehicles or targets for oral cancer therapy. In this review, we first describe the biogenesis, biological functions, and isolation methods of exosomes, followed by their relationship with oral cancer. Here, we focused on the potential of exosomes as oral cancer biomarkers, drug carriers, and therapeutic targets. Finally, we provide an insightful discussion of the opportunities and challenges of exosome application in oral cancer diagnosis and treatment, intending to offer new ideas for the clinical management of oral cancer.

Ti3C2 MXene-anchored photoelectrochemical detection of exosomes by in situ fabrication of CdS nanoparticles with enzyme-assisted hybridization chain reaction

Exosomes that carry large amounts of tumor-specific molecular information have been identified as a potential non-invasive biomarker for early warning of cancer. In this work, we reported an enzyme-assisted photoelectrochemical (PEC) biosensor for quantification of exosomes based on the in situ synthesis of Ti₃C₂ MXene/CdS composites with magnetic separation technology and hybridization chain reaction (HCR). First, exosomes were specifically bound between aptamer-labeled magnetic beads (CD63-MBs) and a cholesterol-labeled DNA anchor. The properly designed anchor ends acted as a trigger to enrich the alkaline phosphatase (ALP) through HCR. It catalyzed more sodium thiophosphate to generate the sulfideion (S²⁻), which combined with Cd²⁺ for in situ fabrication of CdS on Ti₃C₂ MXene resulting in elevated photocurrent. The Ti₃C₂ MXene-anchored PEC method was realized for the quantitative detection of exosomes, which exhibited the dynamic working range from 7.3 × 10⁵ particles per mL to 3.285 × 10⁸ particles per mL with a limit of detection of 7.875 × 10⁴ particles per mL. The strategy showed acceptable stability, high sensitivity, rapid response and excellent selectivity. Furthermore, we believe that the PEC biosensor has huge potential as a routine bioassay method for the precise quantification of exosomes from breast cancer in the future.

An enzyme-assisted photoelectrochemical (PEC) biosensor was established for quantification of exosomes based on the in situ synthesis of Ti₃C₂ MXene/CdS composites with magnetic separation technology and hybridization chain reaction (HCR).

Extracellular Vesicles in the Progression and Therapeutic Resistance of Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is an epithelial malignancy largely associated with Epstein-Barr virus (EBV) infection, which is frequently reported in east and southeast Asia. Extracellular vesicles (EVs) originate from the endosome or plasma membrane, which plays a critical role in tumor pathogenesis for their character of cell-cell communication and its cargos, including proteins, RNA, and other molecules that can target recipient cells and affect their progression. To date, numerous studies have indicated that EVs have crucial significance in the progression, metastasis, and therapeutic resistance of NPC. In this review, we not only summarize the interaction of NPC cells and the tumor microenvironment (TME) through EVs, but also explain the role of EVs in radiation and drug resistance of NPC, which poses a severe threat to cancer therapy. Therefore, EVs may show great potential as biomarkers in the early diagnosis of interfered targets of NPC therapy.

Isothermal nucleic acid amplification technology for rapid detection of virus

While the research field and industrial market of in vitro diagnosis (IVD) thrived during and post the COVID-19 pandemic, the development of isothermal nucleic acid amplification test (INAAT) based rapid diagnosis was engendered in a global wised large measure as a problem-solving exercise. This review systematically analyzed the recent advances of INAAT strategies with practical case for the real-world scenario virus detection applications. With the qualities that make INAAT systems useful for making diagnosis relevant decisions, the key performance indicators and the cost-effectiveness of enzyme-assisted methods and enzyme-free methods were compared. The modularity of nucleic acid amplification reactions that can lead to thresholding signal amplifications using INAAT reagents and their methodology design were examined, alongside the potential application with rapid test platform/device integration. Given that clinical practitioners are, by and large, unaware of many the isothermal nucleic acid test advances. This review could bridge the arcane research field of different INAAT systems and signal output modalities with end-users in clinic when choosing suitable test kits and/or methods for rapid virus detection.

Translating cancer exosomes detection into the color change of phenol red based on target-responsive DNA microcapsules

Emerging evidence indicates that exosomes can be used as a potential biomarker for monitoring diseases, including cancer. However, enhancing the sensing performance in terms of convenience and sensitivity remains an urgent demand for exosomes detection. In this study, a pH-sensitive colorimetric biosensing strategy was developed for exosomes detection by integrating stimuli-responsive DNA microcapsules and acetylcholinesterase to produce acetic acid. The constructed DNA microcapsules consisted of DNA shells crosslinked by anti-CD63 aptamers and loaded with acetylcholinesterase. With exosomes addition, an energetically stabilized aptamer-CD63 compound was produced and microcapsules dissociated due to the reaction of surface protein CD63 of exosomes and aptamer of CD63, resulting in the release of encapsulated AChE. Through a simple centrifugation separation, unreacted DNA microcapsules were removed and the supernatant containing released acetylcholinesterase collected, which was then used for colorimetric exosomes detection through the ability of acetylcholinesterase to hydrolyze acetylcholine to release acetic acid. The resulting decreased solution pH was detected with phenol red indicator, with the sharp color transition conveniently by naked eye. Exosomes quantification was also achieved using the solution's absorption intensity ratio of 558 vs. 432 nm. The linear range was from 2.0 × 10³ to 5.0 × 10⁵ particles/μL, and the limit of detection and limit of quantification were 1.2 × 10³ particles/μL and 2.2 × 10³ particles/μL, respectively. In addition, this proposed strategy for exosomes detection showed a relative standard deviation of 3.1% and high recovery efficiency (>94%), exhibiting a bright application future in exsomes analysis.

Multiplexed Profiling of Extracellular Vesicles for Biomarker Development

Extracellular vesicles (EVs) are cell-derived membranous particles that play a crucial role in molecular trafficking, intercellular transport and the egress of unwanted proteins. They have been implicated in many diseases including cancer and neurodegeneration. EVs are detected in all bodily fluids, and their protein and nucleic acid content offers a means of assessing the status of the cells from which they originated. As such, they provide opportunities in biomarker discovery for diagnosis, prognosis or the stratification of diseases as well as an objective monitoring of therapies. The simultaneous assaying of multiple EV-derived markers will be required for an impactful practical application, and multiplexing platforms have evolved with the potential to achieve this. Herein, we provide a comprehensive overview of the currently available multiplexing platforms for EV analysis, with a primary focus on miniaturized and integrated devices that offer potential step changes in analytical power, throughput and consistency.

Progress in Nanomaterials-Based Optical and Electrochemical Methods for the Assays of Exosomes

Exosomes with diameters of 30-150 nm are small membrane-bound vesicles secreted by a variety of cells. They play an important role in many biological processes, such as tumor-related immune response and intercellular signal transduction. Exosomes have been considered as emerging and noninvasive biomarkers for cancer diagnosis. Recently, a large number of optical and electrochemical biosensors have been proposed for sensitive detection of exosomes. To meet the increasing demands for ultrasensitive detection, nanomaterials have been integrated with various techniques as powerful components. Because of their intrinsic merits of biological compatibility, excellent physicochemical features and unique catalytic ability, nanomaterials have significantly improved the analytical performances of exosome biosensors. In this review, we summarized the recent progress in nanomaterials-based biosensors for the detection of cancer-derived exosomes, including fluorescence, colorimetry, surface plasmon resonance spectroscopy, surface enhanced Raman scattering spectroscopy, electrochemistry, electrochemiluminescence and so on.

Biosensor-based assay of exosome biomarker for early diagnosis of cancer

Cancer imposes a severe threat to people's health and lives, thus pressing a huge medical and economic burden on individuals and communities. Therefore, early diagnosis of cancer is indispensable in the timely prevention and effective treatment for patients. Exosome has recently become an attractive cancer biomarker in noninvasive early diagnosis because of the unique physiology and pathology functions, which reflects remarkable information regarding the cancer microenvironment, and plays an important role in the occurrence and evolution of cancer. Meanwhile, biosensors have gained great attention for the detection of exosomes due to their superior properties, such as convenient operation, real-time readout, high sensitivity, and remarkable specificity, suggesting promising biomedical applications in the early diagnosis of cancer. In this review, the latest advances of biosensors regarding the assay of exosomes were summarized, and the superiorities of exosomes as markers for the early diagnosis of cancer were evaluated. Moreover, the recent challenges and further opportunities of developing effective biosensors for the early diagnosis of cancer were discussed.

Recent advances of nanomaterial-based optical sensor for the detection of benzimidazole fungicides in food: a review

The abuse of pesticides in agricultural land during pre- and post-harvest causes an increase of residue in agricultural products and pollution in the environment, which ultimately affects human health. Hence, it is crucially important to develop an effective detection method to quantify the trace amount of residue in food and water. However, with the rapid development of nanotechnology and considering the exclusive properties of nanomaterials, optical, and their integrated system have gained exclusive interest for accurately sensing of pesticides in food and agricultural samples to ensure food safety thanks to their unique benefit of high sensitivity, low detection limit, good selectivity and so on and making them a trending hotspot. This review focuses on recent progress in the past five years on nanomaterial-based optical, such as colorimetric, fluorescence, surface-enhanced Raman scattering (SERS), and their integrated system for the monitoring of benzimidazole fungicide (including, carbendazim, thiabendazole, and thiophanate-methyl) residue in food and water samples. This review firstly provides a brief introduction to mentioned techniques, detection mechanism, applied nanomaterials, label-free detection, target-specific detection, etc. then their specific application. Finally, challenges and perspectives in the respective field are discussed.

Ultrasensitive Exosome Detection by Modularized SERS Labeling for Postoperative Recurrence Surveillance

Exosome-based liquid biopsy holds great potential in monitoring tumor progression. Current exosome detection biosensors rely on signal amplification strategies to improve sensitivity; however, these strategies pay little attention to manipulating the number of signal reporters, limiting the rational optimization of the biosensors. Here, we have developed a modularized surface-enhanced Raman spectroscopy (SERS) labeling strategy, where each Raman reporter is coupled with lysine as a signal-lysine module, and thus the number of Raman reporters can be precisely controlled by the modularized solid-phase peptide synthesis. Using this strategy, we screened out an optimum Raman biosensor for ultrasensitive exosome detection, with the limit of detection of 2.4 particles per microliter. This biosensor enables a successful detection of the tumor with an average diameter of approximately 3.55 mm, and thus enables successful surveillance of the postoperative tumor recurrence in mice models and distinguishing cancer patients from healthy subjects. Our work provides a de novo strategy to precisely amplify signals toward a myriad of biosensor-related medical applications.

Nanoplasmonic Sensor Approaches for Sensitive Detection of Disease-Associated Exosomes

Exosomes are abundantly secreted by most cells that carry membrane and cytosolic factors that can reflect the physiologic state of their source cells and thus have strong potential to serve as biomarkers for early diagnosis, disease staging, and treatment monitoring. However, traditional diagnostic or prognostic applications that might use exosomes are hindered by the lack of rapid and sensitive assays that can exploit their biological information. An array of assay approaches have been developed to address this deficit, including those that integrate immunoassays with nanoplasmonic sensors to measure changes in optical refractive indexes in response to the binding of low concentrations of their targeted molecules. These sensors take advantage of enhanced and tunable interactions between the electron clouds of nanoplasmonic particles and structures and incident electromagnetic radiation to enable isolation-free and ultrasensitive quantification of disease-associated exosome biomarkers present in complex biological samples. These unique advantages make nanoplasmonic sensing one of the most competitive approaches available for clinical applications and point-of-care tests that evaluate exosome-based biomarkers. This review will briefly summarize the origin and clinical utility of exosomes and the limitations of current isolation and analysis approaches before reviewing the specific advantages and limitations of nanoplasmonic sensing devices and indicating what additional developments are necessary to allow the translation of these approaches into clinical applications.

[Microfluidic strategies for separation and analysis of circulating exosomes]

Exosomes are membrane-bound nanovesicles that are secreted by most types of cells and contain a range of biologically important molecules, including lipids, proteins, ribonucleic acids, etc. Emerging evidences show that exosomes can affect cells' physiological status by transmitting molecular messages among cells. As such, exosomes are involved in various pathological processes. Studying exosomes is of great importance for understanding their biological functions and relevance to disease diagnosis. However, it is difficult to separate and analyze exosomes due to their small size, and because their density is similar to that of bodily fluids. Traditional methods, including ultracentrifugation and ultrafiltration are time-consuming and require expensive equipment. Other methods for exosome separation, including immunoaffinity-based methods, are expensive and rely heavily on specific antibodies. Precipitation-based methods do not yield acceptable purity for downstream analysis, due to polymer contamination. Thus, urgent demand exists for a portable, simple, affordable method for exosome separation. Microfluidic chip technology offers a potential platform for separation and detection of exosomes, with several remarkable characteristics, including low sample consumption, high throughput, and easy integration. This paper provides an overview of current microfluidic strategies for separation and analysis of circulating exosomes. In our introduction to exosome separation, we divide existing separation methods into two categories. Category one is based on exosome physical properties, and includes membrane filtration, nano-column array sorting, and physical isolation. The other is immune capture, which is based on biochemical characteristics of exosomes, and includes fixed base immune capture and unfixed base immune capture. In our introduction to exosome analyses, some commonly used methods, including western blotting, scanning electron microscopy, and flow cytometry are briefly described. Some new systems, which combine microfluidic technology with fluorescence, electrochemical sensing, surface plasmon resonance, or other multimodal analysis methods for integrated detection of exosomes are then described in detail. Finally, the challenges faced by microfluidic technology in improving exosome purity and making systems more portable are analyzed. Prospects for application of microfluidic chips in this area are also discussed. With the rapid development of micro/nano-manufacturing, new materials, and information technology, microfluidic exosome separation and analysis systems will become smaller, more integrated, and more automated. Microfluidic chip technology will play important roles in exosome separation, biochemical detection, and mechanism analysis.

Recent Progress in Detection and Profiling of Cancer Cell-Derived Exosomes

Exosomes, known as nanometer-sized vesicles (30-200 nm), are secreted by many types of cells. Cancer-derived exosomes have great potential to be biomarkers for early clinical diagnosis and evaluation of cancer therapeutic efficacy. Conventional detection methods are limited to low sensitivity and reproducibility. There are hundreds of papers published with different detection methods in recent years to address these challenges. Therefore, in this review, pioneering researches about various detection strategies are comprehensively summarized and the analytical performance of these tests is evaluated. Furthermore, the exosome molecular composition (protein and nucleic acid) profiling, a single exosome profiling, and their application in clinical cancer diagnosis are reviewed. Finally, the principles and applications of machine learning method in exosomes researches are presented.

Metal-Organic Framework-Functionalized Paper-Based Electrochemical Biosensor for Ultrasensitive Exosome Assay

The exosome has emerged as a promising noninvasive biomarker for the early diagnosis of cancer. Therefore, it is highly desirable to develop simple, inexpensive, and user-friendly biosensors for convenient, sensitive, and quantitative exosome assay. Herein, we developed a simple and cost-efficient electrochemical biosensor by combining a metal-organic framework (MOF)-functionalized paper and a screen-printed electrode (SPE) for portable, ultrasensitive, and quantitative determination of cancer-derived exosomes. In principle, the biosensor relied on recognition of the exosome by Zr-MOFs and aptamer to initiate the hybridization chain reaction (HCR) and the formation of DNAzyme for signal amplification. Benefiting from the high signal amplification ability of HCR, the label-free paper-based biosensor is capable of ultrasensitive exosome assay with a detection limit down to 5 × 10³ particles/mL, which is superior to that of most reported methods. Moreover, the proposed paper-based biosensor possessed the advantages of low cost, simple operation, and high sensitivity, making it affordable and deliverable for point-of-care (POC) diagnosis in resource-limited settings.

The role of Exosomes in the Pathogenesis of Nasopharyngeal Carcinoma and the involved Clinical Application

Exosomes are nanoscale membrane vesicles, which carry biologically active substances of their cell of origin and play an important role in signal transduction and intercellular communication. At present, exosomes have been identified as a promising non-invasive liquid biopsy biomarker in the tissues and circulating blood of nasopharyngeal carcinoma (NPC) and found to participate in regulating pathophysiological process of the tumor. We here review recent insights gained into the molecular mechanisms of exosome-induced cell growth, angiogenesis, metastasis, immunosuppression, radiation resistance and chemotherapy resistance in the development and progression of NPC, as well as the clinical application of exosomes as diagnostic biomarkers and therapeutic agents. We also discuss the limitations and challenges in exosome application. We hope this review may provide some references for the use of exosomes in clinical intervention.

High-Fidelity and Simultaneous Sensing of Endogenous Mutant and Wild p53 Proteins for Precise Cancer Diagnosis and Drug Screening

The simultaneous sensing of endogenous wild and mutant proteins plays a critical role in disease diagnosis and drug screening, and this remains a major current challenge. Here, we present a new and highly specific target-triggered dual proximity ligation assay (dPLA) strategy for sensitive and simultaneous sensing of wild and mutant p53 proteins from cancer cells. Two proximity DNA probes bind the target protein to form the primer/circular DNA template complexes with two nicks in the presence of the hairpin and ssDNA connector sequences via the strand displacement reaction. Only when the two nicks are simultaneously ligated can the rolling circle amplification be triggered with high fidelity for yielding substantially enhanced fluorescence. By encoding the hairpin sequence, two distinct fluorescence signals can be generated for simultaneous detection of the wild and mutant p53 proteins. Importantly, our method significantly reduces the possibility of nonspecific ligation reactions by using two ligation nicks, which minimizes the background noise. With this dPLA method, the regulation transition of intracellular mutant p53 to wild p53 proteins upon anticancer drug treatment has also been demonstrated, highlighting its usefulness for potential early disease diagnosis and drug screening with high fidelity.

Review: Multiplexed profiling of biomarkers in extracellular vesicles for cancer diagnosis and therapy monitoring

Extracellular vesicles (EVs) are nanoscale vesicles secreted by normal and pathological cells. The types and levels of surface proteins and internal nucleic acids in EVs are closely related to their original cells, tumor occurrence, and development. Thus, the sensitive and accurate detection of EV biomarkers is a reliable approach for noninvasive disease diagnosis and treatment response monitoring. However, the purification and molecular profiling of these EVs are technically challenging. Much effort has been dedicated to developing new methods for the detection of multiple EV biomarkers. In this review, we summarize the recent progress in EV protein and nucleic acid biomarker analysis. Additionally, we systematically discuss the advantages of multiplexed EV biomarker detection for accurate cancer diagnosis, therapy monitoring, and cancer screening. This article aims to present an overview of all kinds of analytical technologies for assessing EVs and their applications in clinical settings.

Progress in the research of nanomaterial-based exosome bioanalysis and exosome-based nanomaterials tumor therapy

Exosomes and their internal components have been proven to play critical roles in cell-cell interactions and intrinsic cellular regulations, showing promising prospects in both biomedical and clinical fields. Although conventional methods have so far been utilized to great effect, accurate bioanalysis remains a major challenge. In recent years, the fast-paced development of nanomaterials with unique physiochemical properties has led to a boom in the potential bioapplications of such materials. In particular, the application of nanomaterials in exosome bioanalysis provides a great opportunity to overcome the current challenges and limitations of conventional methods. A timely review of the research progress in this field is thus of great significance to the continued development of new methods. This review outlines the properties and potential uses of exosomes, and discusses the conventional methods currently used for their analysis. We then focus on exploring the current state of the art regarding the use of nanomaterials for the isolation, detection and even the subsequent profiling of exosomes. The main methods are based on principles including fluorescence, surface-enhanced Raman spectroscopy, colorimetry, electrochemistry, and surface plasmon resonance. Additionally, research on exosome-based nanomaterials tumor therapy is also promising from a clinical perspective, so the research progress in this branch is also summarized. Finally, we look at ways in which the field might develop in the future.

Recent Advancements in Nanoparticle-Based Optical Biosensors for Circulating Cancer Biomarkers

The effectiveness of cancer treatment strongly depends on the early detection of the disease. Currently, the most common diagnostic method, tissue biopsy, takes time and can be damaging to the patient. Circulating cancer biomarkers such as circulating tumor DNA, micro-RNA (miRNA), tumor proteins, exosomes, and circulating tumor cells have repeatedly demonstrated their viability as targets for minimally invasive cancer detection through liquid biopsies. However, among other things, achieving a great sensitivity of detection is still challenging due to the very low concentration of biomarkers in fluid samples. This review will discuss how the recent advances in nanoparticle-based biosensors are overcoming these practical difficulties. This report will be focusing mainly on optical transduction mechanisms of metal nanoparticles (M-NPs), quantum dots (QDs), and upconversion nanoparticles (UCNPs).

Recent advances in nanomaterial-based biosensors for the detection of exosomes

Exosomes are a type of extracellular vesicle actively secreted by almost all eukaryotic cells. They are ideal candidates for reliable next-generation biomarkers in the early diagnosis and therapeutic response evaluation of cancer. Thus, the quantification of exosomes is crucial in facilitating clinical research and application. Compared with traditional materials, nanomaterials have better optical, magnetic, electrical, and catalytic properties due to their small size, high specific surface area, and variable structure. The incorporation of nanomaterials into sensing systems is an attractive approach towards improving sensitivity and can provide improved sensor selectivity and stability. In this paper, we summarize the progress in nanomaterial-based exosome detection methods, including electrochemical biosensors, photoelectrochemical biosensors, colorimetric biosensors, fluorescence biosensors, chemiluminescence biosensors, electrochemiluminescence biosensors, surface plasmon resonance biosensors, and surface-enhanced Raman spectroscopy biosensors. Moreover, future research directions and challenges in exosome detection methods are discussed. We hope that this article will offer an overview of nanomaterial-based exosome detection techniques and open new avenues in disease research.Graphical abstract.

Trends in MERS-CoV, SARS-CoV, and SARS-CoV-2 (COVID-19) Diagnosis Strategies: A Patent Review

The emergence of a new coronavirus (SARS-CoV-2) outbreak represents a challenge for the diagnostic laboratories responsible for developing test kits to identify those infected with SARS-CoV-2. Methods with rapid and accurate detection are essential to control the sources of infection, to prevent the spread of the disease and to assist decision-making by public health managers. Currently, there is a wide variety of tests available with different detection methodologies, levels of specificity and sensitivity, detection time, and with an extensive range of prices. This review therefore aimed to conduct a patent search in relation to tests for the detection of SARS-CoV, MERS-CoV, and SARS-CoV-2. The greatest number of patents identified in the search were registered between 2003 and 2011, being mainly deposited by China, the Republic of Korea, and the United States. Most of the patents used the existing RT-PCR, ELISA, and isothermal amplification methods to develop simple, sensitive, precise, easy to use, low-cost tests that reduced false-negative or false-positive results. The findings of this patent search show that an increasing number of materials and diagnostic tests for the coronavirus are being produced to identify infected individuals and combat the growth of the current pandemic; however, there is still a question in relation to the reliability of the results of these tests.

Applying CRISPR/Cas13 to Construct Exosomal PD‐L1 Ultrasensitive Biosensors for Dynamic Monitoring of Tumor Progression in Immunotherapy

Programmed cell death receptor 1 (PD‐L1) protein on exosomes (exosomal PD‐L1) is one of the most promising biomarkers for cancer immunotherapy monitoring. However, current approaches for exosomal PD‐L1 detection are poorly sensitive, laborious, and time‐consuming. Here, a new method, named Aptamer‐RPA‐TMA‐Cas13a Assay (ARTCA) is established, which enables exosomal PD‐L1 to be detected directly in serum with a lower limit of 10 particles mL−1. Mechanistically, using DNA aptamer specifically binding to exosomal PD‐L1, the aptamer is amplified twice by recombinase polymerase amplification (RPA) coupled with transcription‐mediated amplification (TMA) and simultaneously the TMA products are detected in real‐time with CRISPR/Cas13a system. Utilizing ARTCA, PD‐L1 levels in circulating exosomes seem to be a reliable marker of PD‐L1 expression in tumor tissue. The level of circulating exosomal PD‐L1 increases significantly in patients with tumor progression. Ultra‐trace detection of serum exosomal PD‐L1 by ARTCA provides a potentially convenient way for dynamic monitoring of tumor progression for patients undergoing immunotherapy. These results demonstrate the use of CRISPR‐Cas13a for protein detection, and circulating exosomal PD‐L1 levels seem to be a reliable marker as well as PD‐L1 expression in tumor tissue, opening up new avenues for monitoring tumor progression.

Rational Design of Functional Peptide-Gold Hybrid Nanomaterials for Molecular Interactions

Gold nanoparticles (AuNPs) have been extensively used for decades in biosensing-related development due to outstanding optical properties. Peptides, as newly realized functional biomolecules, are promising candidates of replacing antibodies, receptors, and substrates for specific molecular interactions. Both peptides and AuNPs are robust and easily synthesized at relatively low cost. Hence, peptide-AuNP-based bio-nano-technological approaches have drawn increasing interest, especially in the field of molecular targeting, cell imaging, drug delivery, and therapy. Many excellent works in these areas have been reported: demonstrating novel ideas, exploring new targets, and facilitating advanced diagnostic and therapeutic technologies. Importantly, some of them also have been employed to address real practical problems, especially in remote and less privileged areas. This contribution focuses on the application of peptide-gold hybrid nanomaterials for various molecular interactions, especially in biosensing/diagnostics and cell targeting/imaging, as well as for the development of highly active antimicrobial/antifouling coating strategies. Rationally designed peptide-gold nanomaterials with functional properties are discussed along with future challenges and opportunities.

Applications of Bionano Sensor for Extracellular Vesicles Analysis

Recently, extracellular vesicles (EVs) and their contents have been revealed to play crucial roles in the intrinsic intercellular communications and have received extensive attention as next-generation biomarkers for diagnosis of diseases such as cancers. However, due to the structural nature of the EVs, the precise isolation and characterization are extremely challenging. To this end, tremendous efforts have been made to develop bionano sensors for the precise and sensitive characterization of EVs from a complex biologic fluid. In this review, we will provide a detailed discussion of recently developed bionano sensors in which EVs analysis applications were achieved, typically in optical and electrochemical methods. We believe that the topics discussed in this review will be useful to provide a concise guideline in the development of bionano sensors for EVs monitoring in the future. The development of a novel strategy to monitor various bio/chemical materials from EVs will provide promising information to understand cellular activities in a more precise manner and accelerates research on both cancer and cell-based therapy.

An ultrasensitive hybridization chain reaction-amplified CRISPR-Cas12a aptasensor for extracellular vesicle surface protein quantification

Tumor-derived extracellular vesicle (TEV) protein biomarkers facilitate cancer diagnosis and prognostic evaluations. However, the lack of reliable and convenient quantitative methods for evaluating TEV proteins prevents their clinical application.

Methods: Here, based on dual amplification of hybridization chain reaction (HCR) and CRISPR-Cas12a, we developed the apta-HCR-CRISPR assay for direct high-sensitivity detection of TEV proteins. The TEV protein-targeted aptamer was amplified by HCR to produce a long-repeated sequence comprising multiple CRISPR RNA (crRNA) targetable barcodes, and the signals were further amplified by CRISPR-Cas12a collateral cleavage activities, resulting in a fluorescence signal.

Results: The established strategy was verified by detecting the TEV protein markers nucleolin and programmed death ligand 1 (PD-L1). Both achieved limit of detection (LOD) values as low as 10² particles/µL, which is at least 10⁴-fold more sensitive than aptamer-ELISA and 10²-fold more sensitive than apta-HCR-ELISA. We directly applied our assay to a clinical analysis of circulating TEVs from 50 µL of serum, revealing potential applications of nucleolin⁺ TEVs for nasopharyngeal carcinoma cancer (NPC) diagnosis and PD-L1⁺ TEVs for therapeutic monitoring.

Conclusion: The platform was simple and easy to operate, and this approach should be useful for the highly sensitive and versatile quantification of TEV proteins in clinical samples.

Recent Advances in Bio-Sensing Methods for the Detection of Tumor Exosomes

Exosomes, small vesicles with the diameters of 40-160 nm, play an important role in intercellular transport and communication. Exosomes are rich in many kinds of biomolecules, and differential expression of exosomal contents directly reflects the state of the original cells. Therefore, the tumor exosomes are appearing as promising biomarkers in liquid biopsy, and highly sensitive and specific detection of tumor exosomes may provide the information for the early diagnosis, real-time monitoring and treatment of the tumors. In this review, we summarized the recent advances in the detection of tumor exosomes, mainly focusing on the use of different analytical techniques, such as optical and electrochemical methods as well as that combination with newly-emerging microfluidic techniques, thereby providing valuable information for the application in the clinical diagnosis and management of the tumors.

Sensitive Signal Amplifying a Diagnostic Biochip Based on a Biomimetic Periodic Nanostructure for Detecting Cancer Exosomes

Tumor-derived exosomes are emerging noninvasive biomarker reservoirs that reflect biological information from their parental cells, especially specific markers, including proteins, DNA fragments and RNAs. Recently, analytical methods of tumor-derived exosomes have been increasing growth. However, developing a convenient signal amplification technique to improve the sensitivity of exosomes detection still remains a challenge. Herein, an ultrasensitive and specific exosomes diagnostic biochip is constructed and further applied to circulating tumor exosomes detection in serum. Using an exosomes diagnostic biochip, signal amplification is achieved by combining the advantages of quantum dots with the biomimetic periodic nanostructure of photonic crystals. Glypican-1 (GPC1), a membrane-anchored protein that is overexpressed in exosomes from pancreatic cancer, is detected using nanosized molecular beacons with high luminescence efficiency; then the signal is amplified through photonic crystals. Moreover, the method allows the quantitative analysis of various disease-specific surface proteins on exosomes. We believe that this exosomes diagnostic biochip is likely to have potential as an effective bioassay, which may be helpful for quantification of disease-specific exosomes in clinical use.

Allosteric Probe-Initiated Wash-Free Method for Sensitive Extracellular Vesicle Detection through Dual Cycle-Assisted CRISPR-Cas12a

Extracellular vesicles (EVs) are emerging as promising biomarkers for cancer diagnosis and therapy. Recognizing low-abundance EVs from clinical samples in an easy-to-operate way is highly desired but remains a challenge. Herein, we established an allosteric probe-initiated dual cycle amplification-assisted CRISPR-Cas12a (AID-Cas) platform for sensitive detection of EVs in a wash-free way. In AID-Cas, the allosteric probe can specifically recognize and bind with target EVs and thus initiate the following dual-cycle amplification. Subsequently, the amplified products were transcribed to generate numerous single-stranded RNAs, which could work as crRNA to trigger the trans-cleavage of CRISPR-Cas12a. Consequently, the proposed approach achieved a good linear response to extracted EVs in a concentration range from 10² to 10⁶ particles/μL. Because of its high sensitivity, together with its wash-free convenience, the proposed strategy could have promising clinical potentials for early diagnosis of cancers.

Optical, electrochemical and electrical (nano)biosensors for detection of exosomes: A comprehensive overview

Exosomes are small extracellular vesicles involved in many physiological activities of cells in the human body. Exosomes from cancer cells have great potential to be applied in clinical diagnosis, early cancer detection and target identification for molecular therapy. While this field is gaining increasing interests from both academia and industry, barriers such as supersensitive detection techniques and highly-efficient isolation methods remain. In the clinical settings, there is an urgent need for rapid analysis, reliable detection and point-of-care testing (POCT). With these challenges to be addressed, this article aims to review recent developments and technical breakthroughs including optical, electrochemical and electrical biosensors for exosomes detection in the field of cancer and other diseases and demonstrate how nanobiosensors could enhance the performance of conventional sensors. Working strategies, limit of detections, advantages and shortcomings of the studies are summarized. New trends, challenges and future perspectives of exosome-driven POCT in liquid biopsy have been discussed.