Sensitive detection of exosomes by gold nanoparticles labeling inductively coupled plasma mass spectrometry based on cholesterol recognition and rolling circle amplification

An Electrochemical Aptasensor for Accurate and Sensitive Detection of Exosomes Based on Dual-Probe Recognition and Hybridization Chain Reaction

The accurate and sensitive detection of tumor-derived exosomes holds significant promise for the early diagnosis of cancer. In this study, an electrochemical aptasensor was developed for the high-performance detection of exosomes by integrating dual-probe recognition and hybridization chain reaction (HCR). A dual-probe recognition unit composed of a MUC1 aptamer (MUC1-Apt) probe and cholesterol probe was designed for capturing target exosomes and reducing the interference from free proteins, significantly improving the accuracy of exosome detection. It should be noted that the dual-probe recognition unit was formed in conjunction with the HCR. Moreover, a large number of biotins were also assembled on the HCR product, which were used to capture avidin-horseradish peroxidase (SA-HRP) for signal amplification. The CD63 aptamer (CD63-Apt) was immobilized on the surface of a gold electrode for specifically capturing exosomes to construct a classical sandwiched structure. The loaded SA-HRP can efficiently catalyze the reaction of 3, 3', 5, 5' tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2) to generate a large electrochemical signal. According to this phenomenon, a linear relationship of this proposed aptasensor was achieved between the electrochemical response and 1 × 102-1 × 107 particles/mL exosomes, with a detection limit of 45 particles/mL. Moreover, the aptasensor exhibited accepted stability and potential clinical applicability. All results proved that this aptasensor has a promising application in exosome-based disease diagnostics.

Emerging biosensing platforms based on metal-organic frameworks (MOFs) for detection of exosomes as diagnostic cancer biomarkers: case study for the role of the MOFs

Exosomes, which are considered nanoscale extracellular vesicles (EVs), are secreted by various cell types and widely distributed in different biological fluids. They consist of multifarious bioactive molecules and use systematic circulation for their transfer to adjoining cells. This phenomenon enables exosomes to take part in intercellular and intracellular communications. They serve as novel and important cancer biomarkers due to their ability to be obtained from various biological fluids and the presence of nucleic acids, proteins, glycoconjugates, and lipids in their structure. The advancement of sensitive and selective exosome detection approaches continues to be a critical challenge that must be addressed. Metal-organic frameworks (MOFs) are a class of 2D and 3D synthetic organic and crystalline nanomaterials, forming through the self-assembly of organic linking molecules and metal ions. The exploration of MOF-based molecules in the recognition of exosomes is an essential aspect in the development of cutting-edge sensing platforms due to their tunable pore structures, excellent adsorption capabilities, and high surface area. Their advantages allow for the inclusion of a large number of electroactive molecules and biological elements, thereby enhancing their electrical conductivity and selectivity, respectively. The synergetic effect of nanomaterials and bioreceptors allows for efficient detection probes. In this review, the different roles of MOFs in the biosensing of exosomes are highlighted, providing a comprehensive understanding of biosensing approaches in this area. In addition, probes based on MOFs and different bioreceptors are investigated for detecting these important cancer biomarkers. The current gaps in this field and future perspectives are discussed.

SERS-Based Droplet Microfluidic Platform for Sensitive and High-Throughput Detection of Cancer Exosomes

Exosomes, nanosized extracellular vesicles containing biomolecular cargo, are increasingly recognized as promising noninvasive biomarkers for cancer diagnosis, particularly for their role in carrying tumor-specific molecular information. Traditional methods for exosome detection face challenges such as complexity, time consumption, and the need for sophisticated equipment. This study addresses these challenges by introducing a novel droplet microfluidic platform integrated with a surface-enhanced Raman spectroscopy (SERS)-based aptasensor for the rapid and sensitive detection of HER2-positive exosomes from breast cancer cells. Our approach utilized an on-chip salt-induced gold nanoparticles (GNPs) aggregation process in the presence of HER2 aptamers and HER2-positive exosomes, enhancing the hot spot-based SERS signal amplification. This platform achieved a limit of detection of 4.5 log10 particles/mL with a sample-to-result time of 5 min per sample. Moreover, this platform has been successfully applied for HER2 status testing in clinical samples to distinguish HER2-positive breast cancer patients from HER2-negative breast cancer patients. High sensitivity, specificity, and the potential for high-throughput screening of specific tumor exosomes make this SERS-based droplet system a potential liquid biopsy technology for early cancer diagnosis.

Exploring capabilities of elemental mass spectrometry for determination of metal and biomolecules in extracellular vesicles

Extracellular vesicles (EVs) are increasingly recognized as crucial components influencing various pathophysiological processes, such as cellular homeostasis, cancer progression, and neurological disease. However, the lack of standardized methods for EV isolation and classification, coupled with ambiguity in biochemical markers associated with EV subtypes, remains a major challenge. This Trends article highlights the most common approaches for EV isolation and characterization, along with recent applications of elemental mass spectrometry (MS) to analyse metals and biomolecules in EVs obtained from biofluids or in vitro cellular models. Considering the promising capabilities of elemental MS, the article also looks ahead to the potential analysis of EVs at the single-vesicle and single-cell levels using ICP-MS. These approaches may offer valuable insights into individual characteristics of EVs and their functions, contributing to a deeper understanding of their role in various biological processes.

Emerging roles of exosomes in oral diseases progression

Oral diseases, such as periodontitis, salivary gland diseases, and oral cancers, significantly challenge health conditions due to their detrimental effects on patient's digestive functions, pronunciation, and esthetic demands. Delayed diagnosis and non-targeted treatment profoundly influence patients' prognosis and quality of life. The exploration of innovative approaches for early detection and precise treatment represents a promising frontier in oral medicine. Exosomes, which are characterized as nanometer-sized extracellular vesicles, are secreted by virtually all types of cells. As the research continues, the complex roles of these intracellular-derived extracellular vesicles in biological processes have gradually unfolded. Exosomes have attracted attention as valuable diagnostic and therapeutic tools for their ability to transfer abundant biological cargos and their intricate involvement in multiple cellular functions. In this review, we provide an overview of the recent applications of exosomes within the field of oral diseases, focusing on inflammation-related bone diseases and oral squamous cell carcinomas. We characterize the exosome alterations and demonstrate their potential applications as biomarkers for early diagnosis, highlighting their roles as indicators in multiple oral diseases. We also summarize the promising applications of exosomes in targeted therapy and proposed future directions for the use of exosomes in clinical treatment.

Discretized butterfly optimization algorithm for variable selection in the rapid determination of cholesterol by near-infrared spectroscopy

The blood cholesterol level is strongly associated with cardiovascular disease. It is necessary to develop a rapid method to determine the cholesterol concentration of blood. In this study, a discretized butterfly optimization algorithm-partial least squares (BOA-PLS) method combined with near-infrared (NIR) spectroscopy is firstly proposed for rapid determination of the cholesterol concentration in blood. In discretized BOA, the butterfly vector is described by 1 or 0, which represents whether the variable is selected or not, respectively. In the optimization process, four transfer functions, i.e., arctangent, V-shaped, improved arctangent (I-atan) and improved V-shaped (I-V), are introduced and compared for discretization of the butterfly position. The partial least squares (PLS) model is established between the selected NIR variables and cholesterol concentrations. The iteration number, transfer functions and the performance of butterflies are investigated. The proposed method is compared with full-spectrum PLS, multiplicative scatter correction-PLS (MSC-PLS), max-min scaling-PLS (MMS-PLS), MSC-MMS-PLS, uninformative variable elimination-PLS (UVE-PLS), Monte Carlo uninformative variable elimination-PLS (MCUVE-PLS) and randomization test-PLS (RT-PLS). Results show that the I-V function is the best transfer function for discretization. Both preprocessing and variable selection can improve the prediction performance of PLS. Variable selection methods based on BOA are better than those based on statistics. Furthermore, I-V-BOA-PLS has the highest predictive accuracy among the seven variable selection methods. MSC-MMS can further improve the prediction ability of I-V-BOA-PLS. Therefore, BOA-PLS combined with NIR spectroscopy is promising for the rapid determination of cholesterol concentration in blood.

Review of the advances in lipid anchors-based biosensors for the isolation and detection of exosomes

Exosomes are nanoparticles with a bilayer lipid structure that carry cargo from their cells of origin. These vesicles are vital to disease diagnosis and therapeutics; however, conventional isolation and detection techniques are generally complicated, time-consuming, and costly, thus hampering the clinical applications of exosomes. Meanwhile, sandwich-structured immunoassays for exosome isolation and detection rely on the specific binding of membrane surface biomarkers, which may be limited by the type and amount of target protein present. Recently, lipid anchors inserted into the membranes of vesicles through hydrophobic interactions have been adopted as a new strategy for extracellular vesicle manipulation. By combining nonspecific and specific binding, the performance of biosensors can be improved variously. This review presents the reaction mechanisms and properties of lipid anchors/probes, as well as advances in the development of biosensors. The combination of signal amplification methods with lipid anchors is discussed in detail to provide insights into the design of convenient and sensitive detection techniques. Finally, the advantages, challenges, and future directions of lipid anchor-based exosome isolation and detection methods are highlighted from the perspectives of research, clinical use, and commercialization.

Colorimetric aptasensor based on spherical nucleic acid-induced hybridization chain reaction for sensitive detection of exosomes

Exosomes are one of the most promising biomarkers for tumor diagnosis and prognosis. Therefore, the development of convenient and sensitive exosome sensing strategies is of great significance. Herein, we integrated aptamer-based spherical nucleic acids (SNAs) and hybridization chain reaction (HCR) into a colorimetric aptasensor platform and applied it to the detection of exosomes. In this design, the CD63-specific aptamer pre-immobilized on the microplate was used to capture target exosomes, while the SNAs conjugated with nucleolin-specific aptamer and trigger probe H1 were designed for amplifying signal. In the presence of target exosomes, the SNAs can be attached to the microplate by the bridge effect of exosomes, resulting in the trigger of HCR. This process is accompanied by the formation of abundant G-quadruplex/hemin DNAzyme, enabling the visual quantitative analysis of exosomes. Featured with the dual amplification of SNAs and HCR, the proposed aptasensor achieved a considerable detection limit of 50 particles/μL. The practicability of this method was further verified by testing the different clinical samples. Given the ability of the aptasensor to visually detect exosomes in scenarios lacking instruments and resources, we believe that the aptasensor can be serve as a potential on-site test for liquid biopsy.

Nanomaterials for Molecular Detection and Analysis of Extracellular Vesicles

Extracellular vesicles (EVs) have emerged as a novel resource of biomarkers for cancer and certain other diseases. Probing EVs in body fluids has become of major interest in the past decade in the development of a new-generation liquid biopsy for cancer diagnosis and monitoring. However, sensitive and specific molecular detection and analysis are challenging, due to the small size of EVs, low amount of antigens on individual EVs, and the complex biofluid matrix. Nanomaterials have been widely used in the technological development of protein and nucleic acid-based EV detection and analysis, owing to the unique structure and functional properties of materials at the nanometer scale. In this review, we summarize various nanomaterial-based analytical technologies for molecular EV detection and analysis. We discuss these technologies based on the major types of nanomaterials, including plasmonic, fluorescent, magnetic, organic, carbon-based, and certain other nanostructures. For each type of nanomaterial, functional properties are briefly described, followed by the applications of the nanomaterials for EV biomarker detection, profiling, and analysis in terms of detection mechanisms.