Magneto-Mediated Electrochemical Sensor for Simultaneous Analysis of Breast Cancer Exosomal Proteins

CRISPR/Cas12a and aptamer-chemiluminescence based analysis for the relative abundance determination of tumor-related protein positive exosomes for breast cancer diagnosis

Exosomes, as novel biomarker for liquid biopsy, exhibit huge important potential value for cancer diagnosis. However, various proteins show different expression levels on exosomal membrane, and the absolute concentration of exosomes in clinical samples is easily influenced by a number of factors. Here, we developed a CRISPR/Cas12a and aptamer-chemiluminescence based analysis (CACBA) for the relative abundance determination of tumor-related protein positive exosomes in plasma for breast cancer diagnosis. The total concentration of exosomes was determined through captured CD63 using a CRISPR/Cas12a-based method with the LoD of 8.97 × 103 particles/μl. Meanwhile, EpCAM and MUC1 positive exosomes were quantitatively detected by aptamer-chemiluminescence (ACL) based method with the LoD of 1.45 × 102 and 3.73 × 102 particles/μl, respectively. It showed that the percentages of EpCAM and MUC1 positive exosomes offered an excellent capability to differentiate breast cancer patients and healthy donors. The high sensitivity, strong specificity, outstanding anti-interference capability, and steady recovery rate of this approach offered higher accuracy and robustness than the commercialized method in clinical trial. In addition with good stability, easy preparation and low cost, this method not only provides a new approach to rapid analysis of exosome proteins, it may be quickly extended to the diagnoses of various cancers.

A homogeneous electrochemiluminescence immunoassay platform based on carbon quantum dots and magnetic beads enrichment for detection of thyroglobulin in serum

Considering the high probability of recurrence or metastasis after thyroidectomy, it is meaningful to develop a rapid, sensitive and specific method for monitoring thyrophyma-related biomarkers. In this study, a homogeneous electrochemiluminescence immunoassay (HO-ECLIA) coupled with magnetic beads (MBs)-based enrichment tactic was established for the determination of thyrophyma-related thyroglobulin (Tg). Importantly, owing to the abundant surface groups and good biocompatibility of carbon quantum dots (CQDs), the incorporation of CQDs onto the Tg antigen surface was achieved, resulting in the formation of Tg-encapsulated CQDs (CQDs-Tg), which served not only as an ECL probe but as a biorecognition element. Under optimal experimental conditions, the proposed platform demonstrated a wide linear range from 0.01 to 100 ng·mL-1 with a detection limit of 6.9 pg·mL-1 (S/N = 3), and performed well in real serum sample analysis against interference. Collectively, the proposed platform exhibited the rapid response, satisfactory sensitivity and specificity toward Tg in complex serum milieu, and held a considerable potential for clinical prognosis monitoring of thyrophyma.

Empowering Exosomes with Aptamers for Precision Theranostics

As information messengers for cell-to-cell communication, exosomes, typically small membrane vesicles (30-150 nm), play an imperative role in the physiological and pathological processes of living systems. Accumulating studies have demonstrated that exosomes are potential biological candidates for theranostics, including liquid biopsy-based diagnosis and drug delivery. However, their clinical applications are hindered by several issues, especially their unspecific detection and insufficient targeting ability. How to upgrade the accuracy of exosome-based theranostics is being widely explored. Aptamers, benefitting from their admirable characteristics, are used as excellent molecular recognition elements to empower exosomes for precision theranostics. With high affinity against targets and easy site-specific modification, aptamers can be incorporated with platforms for the specific detection of exosomes, thus providing opportunities for advancing disease diagnostics. Furthermore, aptamers can be tailored and functionalized on exosomes to enable targeted therapeutics. Herein, this review emphasizes the empowering of exosomes by aptamers for precision theranostics. A brief introduction of exosomes and aptamers is provided, followed by a discussion of recent progress in aptamer-based exosome detection for disease diagnosis, and the emerging applications of aptamer-functionalized exosomes for targeted therapeutics. Finally, current challenges and opportunities in this research field are presented.

Multi-Enzyme Cascade Nanoreactors for High-Throughput Immunoassay: Transitioning Concept in Lab to Application in Community

In this work, we reported a cholesterol oxidase (Chox)-loaded platinum (Pt) nanozyme with the collaborative cascade nanoreactor for the construction of nanozyme-enzyme-linked immunosorbent assay (N-ELSA) models to realize high-throughput rapid evaluation of cancer markers. Considering the high specific surface area and manipulable surface sites, ZIF-8 was used as a substrate for natural enzyme and nanozyme loading. The constructed ZIF-8-Pt nanozyme platform exhibited efficient enzyme-like catalytic efficiency with a standard corrected activity of 60.59 U mg-1, which was 12 times higher than that of the ZIF-8 precursor, and highly efficient photothermal conversion efficiency (∼35.49%). In N-ELISA testing, developed multienzyme photothermal probes were immobilized in microplates based on antigen-antibody-specific reactions. Cholesterol was reacted in a cascade to reactive oxygen radicals, which attacked 3,3',5,5'-tetramethylbenzidine, causing it to oxidize and color change, thus exhibiting highly enhanced efficient photothermal properties. Systematic temperature evaluations were performed by a hand-held microelectromechanical system thermal imager under the excitation of an 808 nm surface light source to determine the cancer antigen 15-3 (CA15-3) profiles in the samples. Encouragingly, the temperature signal from the microwells increased with increasing CA15-3, with a linear range of 2 mU mL-1 to 100 U mL-1, considering it to be the sensor with the widest working range for visualization and portability available. This work provides new horizons for the development of efficient multienzyme portable colorimetric-photothermal platforms to help advance the community-based process of early cancer detection.

Enhanced synthesis of antibody-functionalized gold nanoparticles for multiplexed exosome detection via mass signal amplification in LDI-TOF MS

We present a novel method for sensitive exosomal protein detection using organic matrix-free laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS) and gold nanoparticles (AuNPs) functionalized with mass tags for signal amplification (Am-tags). Target exosomes were captured by specific antibodies on AuNPs and a biochip, where the antibody-presenting AuNPs (Ab/Am-tag@AuNPs) contained excess Am-tags. LDI-TOF MS analysis revealed the mass signal of Am-tags on Ab/Am-tag@AuNPs, indicating the presence of target exosomes. Thus, the target signal was amplified by a large number of Am-tags, resulting in enhanced sensitivity. We optimized the protocol to prepare stable Ab/Am-tag@AuNPs, focusing on parameters such as the concentration and ratio of thiol molecules for AuNP functionalization, suitable solvents for the coupling reaction, and amount of antibodies conjugated to the AuNPs. Subsequently, we evaluated the ability of our method to detect exosomes isolated from three cell lines, NIH3T3, MCF7, and HeLa, using an anti-Rab5 immobilized gold chip and anti-CD63/Am-tag@AuNPs with LDI-TOF MS analysis. Calibration curves constructed for the three cell lines showed a linear relationship with an excellent limit of detection. Finally, we emphasized the versatility of our method for the quantitative detection of exosomal proteins CD63 and mucin 1 (MUC1) using two types of Am-tags. LDI-TOF MS analysis revealed the presence of CD63 and MUC1 at different expression levels in HeLa and MCF7 cancer cells. Our findings clearly indicate the potential of Ab/Am-tag@AuNPs as a sensitive and reliable approach for identifying biomarkers in exosomes, providing valuable insights into their utility in biomedical research and clinical settings.

Aptamer-bivalent-cholesterol-mediated proximity entropy-driven exosomal protein reporter for tumor diagnosis

Exosomal proteins from the parental cells are considered to be promising biomarker sets for precise tumor diagnostics and monitoring. However, the accurate quantitative analysis of low-abundance exosomal proteins remains challenging due to the heterogeneity of clinical samples. Here, we standardized the exosomal concentration with a fluorogenic membrane probe and developed an aptamer-bivalent-cholesterol-mediated Proximity Entropy-driven Exosomal Protein Reporter (PEEPR). The proposed PEEPR enables the in-situ analysis of multiple exosomal proteins by integrating bivalent cholesterol anchor (exosomal lipid bilayer) and aptamer (exosomal proteins) with a proximity entropy-driven circuit. Based on this strategy, we successfully achieved detection limits of 3.9 pg/mL exosomal GPC-3 and 3.4 pg/mL exosomal PD-L1. Notably, the standardization of exosome concentrations is designed to avoid errors due to biological heterogeneity. The results showed that evaluating the levels of exosomal GPC-3 and PD-L1 in clinical samples via this strategy could accurately differentiate healthy individuals, hepatitis B patients, and hepatocellular carcinoma patients. In summary, PEEPR is a promising clinical diagnostic strategy for the quantitative analysis of a variety of tumor-associated exosomal proteins for the precise diagnosis and personalized treatment monitoring of tumors.

Weak Value Amplification-Based Biochip for Highly Sensitive Detection and Identification of Breast Cancer Exosomes

Exosomes constitute an emerging biomarker for cancer diagnosis because they carry multiple proteins that reflect the origins of the parent cell. The highly sensitive detection of exosomes is a crucial prerequisite for the diagnosis of cancer. In this study, we report an exosome detection system based on quantum weak value amplification (WVA). The WVA detection system consists of a reflection detection light path and a Zr-ionized biochip. Zr-ionized biochips effectively capture exosomes through the specific interaction between zirconium dioxide and the phosphate groups on the lipid bilayer of exosomes. Aptamer-modified gold nanoparticles (Au NPs) are then used to specifically recognize proteins on exosomes to enhance the detection signal. The sensitivity and resolution of the detection system are 2944.07 nm/RIU and 1.22 × 10-5 RIU, respectively. The concentration of exosomes can be directly quantified by the WVA system, ranging from 105-107 particles/mL with the detection limit of 3 × 104 particles/mL. The use of Au NPs-EpCAM for the specific enhancement of breast cancer MDA-MB-231 exosomes is demonstrated. The results indicate that the WVA detection system can be a promising candidate for the detection of exosomes as tumor markers.

DNA four-way junction-driven dual-rolling circle amplification sandwich-type aptasensor for ultra-sensitive and specific detection of tumor-derived exosomes

There is an urgent need to accurately quantify tumor-derived exosomes, which have emerged as promising non-invasive tumor diagnostic biomarkers. Herein, a bispecific-aptamer sandwich-type gold nanoparticle-modified electrochemical aptasensor was developed based on a four-way junction (4-WJ)-triggered dual rolling circle amplification (RCA)-assisted methylene blue (MB)/G-quadruplex strategy for extremely specific and sensitive exosome detection. This aptamer/exosome/aptamer sandwich-type design contained a CD63-specific aptamer and a cancerous mucin-1 (MUC1) protein-specific aptamer. The CD63 aptamer modified on a gold electrode captured exosomes, and then the sandwich-type aptasensor was formed with the addition of the MUC1 aptamer. The MUC1 aptamer's 3'-end sequence facilitated the formation of 4-WJ, assisted by a molecular beacon probe and a binary DNA probe. Subsequently, a dual-RCA reaction was triggered by binding to two cytosine-rich circle DNA templates at both ends of 4-WJ. Ultimately, dual-RCA products containing multiple G-quadruplex conformations were generated with the assistance of K+ to trap abundant MB indicators and amplify electrochemical signals. The aptasensor exhibited high specificity, sensitivity, repeatability, and stability toward MCF-7-derived exosomes, with a detection limit of 20 particles/mL and a linear range of 1 × 102 to 1 × 107 particles/mL. Moreover, it showed excellent applicability in clinical settings to recover exosomes in normal human serum. Our aptasensor is anticipated to serve as a versatile platform for detecting various specific aptamer-based targets in biomedical and bioanalytical applications.

The Landscape of Biomimetic Nanovesicles in Brain Diseases

Brain diseases, such as brain tumors, neurodegenerative diseases, cerebrovascular diseases, and brain injuries, are caused by various pathophysiological changes, which pose a serious health threat. Brain disorders are often difficult to treat due to the presence of the blood-brain barrier (BBB). Biomimetic nanovesicles (BNVs), including endogenous extracellular vesicles (EVs) derived from various cells and artificial nanovesicles, possess the ability to penetrate the BBB and thus can be utilized for drug delivery to the brain. BNVs, especially endogenous EVs, are widely distributed in body fluids and usually carry various disease-related signal molecules such as proteins, RNA, and DNA, and may also be analyzed to understand the etiology and pathogenesis of brain diseases. This review covers the exhaustive classification and characterization of BNVs and pathophysiological roles involved in various brain diseases, and emphatically focuses on nanotechnology-integrated BNVs for brain disease theranostics, including various diagnosis strategies and precise therapeutic regulations (e.g., immunity regulation, disordered protein clearance, anti-neuroinflammation, neuroregeneration, angiogenesis, and the gut-brain axis regulation). The remaining challenges and future perspectives regarding the nanotechnology-integrated BNVs for the diagnosis and treatment of brain diseases are also discussed and outlined.

Immunomagnetic capture and traceless release of native tumor-derived exosomes from human plasma for exploring interaction with recipient cells by aptamer-functionalized nanoflowers

BACKGROUND

Tumor-derived exosomes (TEXs) play an important role in the development process of cancer, which can transport a large number of carcinogenic molecules to normal cells, and subsequently promote tumor metastasis. However, TEXs that were utilized in most of previous researches were obtained from the cell medium of tumor cell lines, which cannot reflect the physiological state of primary cells in vivo. Isolation of native TEXs from human plasma with intact function is contributed to exploring the interaction between TEXs and recipient cells for understanding their true biological functions.

RESULTS

We developed a strategy that involves both capture and release processes to obtain native TEXs from plasma of cancer patients. An MoS2-based immunomagnetic probe (Fe3O4@MoS2-Au-Aptamer, named as FMAA) with the advantages of high surface area, magnetic response and abundant affinity sites was designed and synthesized to capture TEXs through recognizing high-expression tumor-associated antigens of EpCAM. With the assistance of complementary sequences of EpCAM, TEXs were released with non-destruction and no residual labels. According to NTA analysis, 107-108 TEXs were recovered from per mL plasma of breast cancer patients. The interaction between native TEXs and normal epithelial cells confirms TEXs could induce significant activation of autophagy of recipient cells with co-culture for 12 h. Proteomics analysis demonstrated a total of 637 proteins inside epithelial cells had dynamic expression with the stimulation of TEXs and 5 proteins in the pathway of autophagy had elevated expression level.

SIGNIFICANCE

This work not only obtains native TEXs from human plasma with non-destruction and no residual labels, but also explores the interaction between TEXs and recipient cells for understanding their true biological functions, which will accelerate the application of TEXs in the field of biomarkers and therapeutic drugs.

Ultrasensitive determination of surface proteins on tumor-derived small extracellular vesicles for breast cancer identification based on lanthanide-activated signal amplification strategy

Small extracellular vesicles (sEVs) carrying multiple tumor-associated proteins inherited from parental cells play crucial roles in noninvasive breast cancer (BC) diagnosis. However, it is challenging to assess the subtle variations of surface proteins on sEV membranes due to the highly heterogeneous BC. Therefore, a simple and ultrasensitive assay based on lanthanide (Ln3+)-activated luminescence signal amplification was developed to detect multiple surface proteins on BC-derived sEVs. Multiple protein biomarkers on sEVs can be well identified with high sensitivity and specificity through dissolution-amplified luminescence of the NaEuF4 nanoparticle-based nanoprobe. We employ linear discriminant analysis to successfully discriminate triple negative BC cell (MDA-MB-231 cell) derived sEVs from other breast cell lines (MCF-7, SK-BR-3, BT474 and MCF-10A cell). Furthermore, the strategy enables high accuracy for districting the progression stages of BC patients and healthy donors. The simple and sensitive signal amplification strategy exhibits great potential for early clinic diagnosis by precise protein profiling of sEVs.

A Magnetically Driven Tandem Chip Enables Rapid Isolation and Multiplexed Profiling of Extracellular Vesicles

The protein phenotypes of extracellular vesicles (EVs) have emerged as promising biomarkers for cancer diagnosis and treatment monitoring. However, the technical challenges in rapid isolation and multiplexed molecular detection of EVs have limited their clinical practice. Herein, we developed a magnetically driven tandem chip to achieve streamlined rapid isolation and multiplexed profiling of surface protein biomarkers of EVs. Driven by magnetic force, the magnetic nanomixers not only act as tiny stir bars to promote mass transfer and enhance reaction efficiency of EVs, but also transport on communicating vessels of the tandem chip continuously and expedite the assay workflow. We designed cyclic surface enhancement of Raman scattering (SERS) tags to bind with target EVs and then release them by exonuclease I, eliminating steric hindrance and amplifying the SERS signal of multiple protein biomarkers on EVs. Due to the excellent assay performance, six breast cancer biomarkers were detected simultaneously on EVs using only 10 μL plasma within 1.5 h. The unweighted SUM signature offers great accuracy in discriminating breast cancer patients from healthy donors. Overall, the dynamic magnetic driving tandem chip offers a new avenue to advance the clinical application of EV-based liquid biopsy.

Accurate and noninvasive diagnosis of epithelial cancers through AND gate photoluminescence on tumor-derived small extracellular vesicles

Noninvasive detection of small extracellular vesicles (sEVs) has become one of the most promising liquid biopsy methodologies for effective and timely cancer diagnosis and prognostic monitoring. Currently, accurate and sensitive detection of tumor-derived sEVs is compromised by their heterogeneous nature, and the tissue origin and parent cell cycle change may significantly affect the tumor-associated information (e.g., phenotypic proteins) of sEVs. Accordingly, many of the single-marker dependent detections on sEVs may not provide comprehensive information about the tumor, and their reliability and clinical applicability cannot be guaranteed. Herein, a strategy for constructing AND gate photoluminescence on tumor-derived sEVs is proposed. Briefly, only after co-recognition of the two epithelial phenotypic proteins (EpCAM and MUC1) on tumor-derived sEVs simultaneously, can our designed lanthanide luminescence probe precursors then assemble to form the AND gate for photoluminescence detection. Consequently, the generated AND gate photoluminescence provided time-resolved luminescence for a wide cancerous sEV linear detection range of 6.0 × 104-6.0 × 109 particles per mL, with a calculated detection limitation of 1.42 × 102 particles per mL. Furthermore, the AND gate photoluminescence can significantly distinguish epithelial cancer patients from healthy controls, displaying its great potential for accurate and noninvasive cancer diagnosis.

Employing the Anchor DSPE-PEG as a Redox Probe for Ratiometric Electrochemical Detection of Surface Proteins on Extracellular Vesicles with Aptamers

Quantitative analysis of surface proteins on extracellular vesicles (EVs) has been considered to be a crucial approach for reflecting the status of diseases. Due to the diverse composition of surface proteins on EVs and the interference from nonvesicular proteins, accurately detecting the expression of surface proteins on EVs remains a challenging task. While membrane affinity molecules have been widely employed as EVs capture probes to address this issue, their inherent biochemical properties have not been effectively harnessed. In this paper, we found that the electrochemical redox activity of the DSPE-PEG molecule was diminished upon its insertion into the membrane of EVs. This observation establishes the DSPE-PEG molecule modified on the Au electrode surface as a capture and a redox probe for the electrochemical detection of EVs. By utilizing methylene blue-labeled aptamers, the targeted surface proteins of EVs can be detected by recording the ratio of the oxidation peak current of methylene blue and DSPE-PEG. Without complicated signal amplification, the detection limit for EVs is calculated to be 8.11 × 102 particles/mL. Using this platform, we directly analyzed the expression of CD63 and HER2 proteins on the surface of EVs in human clinical plasma samples, demonstrating its significant potential in distinguishing breast cancer patients from healthy individuals.

A filter-electrochemical microfluidic chip for multiple surface protein analysis of exosomes to detect and classify breast cancer

Breast cancer (BC) is a complex disease with high variability and no specific tumor markers available for diagnosis. Exosomes contain rich maternal tumor information and are a novel non-invasive biomarker with the potential for cancer diagnosis and prognosis. However, analysis of exosomal protein markers in blood samples is challenging due to lengthy sample workups and insufficient sensitivity. To address this difficulty, we developed a novel filter-electrochemical microfluidic chip (FEMC) to detect and classify BC directly in whole blood without requiring heavy purification methods. In our system, exosome enrichment was performed using a dual filtration system. The target was directed through a curved channel onto four screen-printed electrodes (SPEs), where it was captured by the previously modified antibodies. Simultaneously, Zr-MOFs encapsulated with a large number of methylene blue molecules (MB@UiO-66) were absorbed on the surface of exosomes due to the high affinity for phosphate groups. This process leads to the amplification of electrical signals. The approach demonstrated that the utilization of BC exosome-associated tumor biomarkers (i.e., PMSA, EGFR, CD81, and CEA), enabled the classification of various BC mouse models samples and clinical BC samples. The entire FEMC assay was completed in 1 h with a limit of detection of 1 × 104 particles/mL. Thus, the FEMC assay can provide real-time detection information, allowing timely and better-informed opportunities for clinical BC diagnosis and typing.

Asymmetrically split DNAzyme-based colorimetric and electrochemical dual-modal biosensor for detection of breast cancer exosomal surface proteins

Exosomal surface proteins are potentially useful for breast cancer diagnosis and awareness of risk. However, some detection techniques involving complex operations and expensive instrumentation are limited to advance to clinical applications. To solve this problem, we develop a dual-modal sensor combining naked-eye detection and electrochemical assay of exosomal surface proteins from breast cancer. Most of existing sensors rely on aptamers recognizing exosomes and generating amplified signals at the same time, which require well-designed aptamer probes to avoid difficulties in identifying exosomes. In our work, aptamers not bound by the exosomes can serve as complete templates to induce formation of G quadruplexes. The peroxidase activity of the G-quadruplex/hemin DNAzyme catalyze substrates can generate both color and electrochemical signals. The developed dual-modal sensor offers a remarkable capability to differentiate nonmetastatic, metastatic breast cancer patients, and healthy individuals through the analysis of exosomal surface proteins. The sensor's distinctive features, including its universality, simplicity, and cost-effectiveness, position it as a promising diagnostic tool in breast cancer research and clinical practice.

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.

Recent progress in quantitative technologies for the analysis of cancer-related exosome proteins

Exosomes are a kind of extracellular vesicles, which play a significant role in intercellular communication and molecular exchange. Cancer-derived exosomes are potential and ideal biomarkers for the early diagnosis and treatment monitoring of cancers because of their abundant biological information and contribution to the interaction between cancer cells and the tumor microenvironment. However, there are a number of drawbacks, such as low sensitivity and tedious steps, in conventional detection techniques. Furthermore, exosome quantification is not enough to accurately distinguish cancer patients from healthy individuals. Therefore, developing efficient, accurate, and inexpensive exosome surface protein analysis techniques is necessary and critical. In recent years, a considerable number of researchers have presented novel detection strategies in this field. This review summarizes the recent progress in quantitative technologies for the analysis of cancer-related exosome proteins, mainly including the detection methods based on aptamers, nanomaterials, and antibodies, discusses a roadmap for future developments, and aims to offer an innovative perspective of exosome research.

Current research status of tumor cell biomarker detection

With the annual increases in the morbidity and mortality rates of tumors, the use of biomarkers for early diagnosis and real-time monitoring of tumor cells is of great importance. Biomarkers used for tumor cell detection in body fluids include circulating tumor cells, nucleic acids, protein markers, and extracellular vesicles. Among them, circulating tumor cells, circulating tumor DNA, and exosomes have high potential for the prediction, diagnosis, and prognosis of tumor diseases due to the large amount of valuable information on tumor characteristics and evolution; in addition, in situ monitoring of telomerase and miRNA in living cells has been the topic of extensive research to understand tumor development in real time. Various techniques, such as enzyme-linked immunosorbent assays, immunoblotting, and mass spectrometry, have been widely used for the detection of these markers. Among them, the detection of tumor cell markers in body fluids based on electrochemical biosensors and fluorescence signal analysis is highly preferred because of its high sensitivity, rapid detection and portable operation. Herein, we summarize recent research progress in the detection of tumor cell biomarkers in body fluids using electrochemical and fluorescence biosensors, outline the current research status of in situ fluorescence monitoring and the analysis of tumor markers in living cells, and discuss the technical challenges for their practical clinical application to provide a reference for the development of new tumor marker detection methods.

Absolute Quantification of Serum Exosomes in Patients with an SERS-Lateral Flow Strip Biosensor for Noninvasive Clinical Cancer Diagnosis

Exosomes (exos) widely existing in body fluids show great potential for noninvasive cancer diagnosis. Quantitative analysis of exos is traditionally performed by targeting specific exosomal surface proteins, but it is often imprecise due to the common expression of exosomal proteins and subtle expression differences between different cancer subtypes. Herein, we report quantitative surface-enhanced Raman spectroscopy (SERS) of serum exos through a combination of a paper-based lateral flow strip (LFS) biosensor with multivariate spectral unmixing analysis rather than simply quantifying exosomal proteins. Our SERS-LFS biosensor enables absolute quantification of two different serum exos with a limit of detection down to ∼106 particles/mL for both exos. We further exemplify the application of this strategy in quantitative dual-plex detection of serum exos from breast cancer patients. We find that human epidermal growth factor receptor 2+ (HER2+) and luminal A breast cancer patients undergoing no surgery are enriched in serum exos derived from SKBR-3 cells and MCF-7 cells (denoted as SKBR and MCF exos), respectively. The surgical treatment of these breast cancer patients accompanies an obvious decrease of either SKBR or MCF exos in the serum. These results suggest the great potential of the combination of the SERS-LFS biosensor and multivariate spectral unmixing for breast cancer subtyping and therapeutic surveillance with the powerful quantitative capability of exos in clinical samples.

Ultrasensitive detection of exosomes by microchip electrophoresis combining with triple amplification strategies

The analysis of exosomes is significant as they can be used for various pathophysiological processes, especially cancer related intercellular communication. Therefore, a convenient, reliable, and sensitive detection method is urgently needed. Strand displacement amplification (SDA) and catalytic hairpin assembly (CHA) are two kinds of effective isothermal nucleic acid amplification methods. In this article, an efficient quantitative MCE method for detecting human breast cancer cell (MCF-7) exosomes assisted by triple amplification strategies combining cholesterol probe (Chol-probe) with SDA-CHA was first developed. CD63 aptamer was immobilized on the avidin magnetic beads to specifically capture exosomes and then Chol-probe with high affinity was spontaneously inserted into the exosome membrane, which was the first step of amplification strategy to improve detection sensitivity. After magnetic separation, Chol-probe could complement ssDNA and trigger SDA, producing a large number of DNA sequences (Ta) to trigger CHA, achieving SDA-CHA amplification. Under optimal conditions, the detection limit (LOD) for MCF-7 exosomes was as low as 26 particle/μL (S/N = 3). This method provides an effective approach for sensitive and accurate quantification of tumor exosomes, and can be expected to detect exosomes in clinical samples.

Quantification of GPC1(+) Exosomes Based on MALDI-TOF MS In Situ Signal Amplification for Pancreatic Cancer Discrimination and Evaluation

Pancreatic cancer (PC) has a high mortality, with a fairly low five-year survival rate, because of its delayed diagnosis. Recently, liquid biopsy, especially based on exosomes, has attracted vast attention, thanks to its low invasiveness. Herein, we constructed a protocol for pancreatic cancer related Glypican 1 (GPC1) exosome quantification, based on in situ mass spectrometry signal amplification, by utilizing mass tag molecules on gold nanoparticles (AuNPs). Exosomes were extracted and purified by size-exclusion chromatography (SEC), captured by TiO₂ modified magnetic nanoparticles, and then targeted specifically by anti-GPC1 antibody modified on AuNPs. With matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), the signal of PC biomarker, GPC1, was converted to a mass tag signal and amplified. With addition of a certain amount of internal standard molecules modified on AuNPs, the relative intensity ratio of mass tag to internal standard was proportional to the concentration of GPC1(+) exosomes derived from pancreatic cancer cell lines, PANC-1, with good linearity (R² = 0.9945) in a wide dynamic range from 7.1 × 10 to 7.1 × 10⁶ particles/μL. This method was further applied to plasma samples from healthy control (HC) and pancreatic cancer patients with different tumor load, and exhibited a great potential in discriminating diagnosed PC patients from HC, and has the monitoring potential in PC progression.

One-step multiplex analysis of breast cancer exosomes using an electrochemical strategy assisted by gold nanoparticles

Exosomes, as a non-invasive biomarker, perform an important role in breast cancer screening and prognosis monitoring. However, establishing a simple, sensitive, and reliable exosome analysis technique remains challenging. Herein, a one-step multiplex analysis electrochemical aptasensor based on a multi-probe recognition strategy was constructed to analyze breast cancer exosomes. HER2-positive breast cancer cell (SK-BR-3) exosomes were selected as the model targets and three aptamers including CD63, HER2 and EpCAM aptamers were used as the capture units. Methylene blue (MB) functionalized HER2 aptamer and ferrocene (Fc) functionalized EpCAM aptamer, which were modified on gold nanoparticles (Au NPs), i.e. MB-HER2-Au NPs and Fc-EpCAM-Au NPs, were used as signal units. When the mixture of target exosomes, MB-HER2-Au NPs and Fc-EpCAM-Au NPs were added on the CD63 aptamer modified gold electrode, two Au NPs modified by MB and Fc could be specifically captured on the electrode by the recognition of three aptamers with target exosomes. Then one-step multiplex analysis of exosomes was achieved by detecting two independent electrochemical signals. This strategy can not only distinguish breast cancer exosomes from other exosomes (including normal exosomes and other tumor exosomes) but also HER2-positive breast cancer exosomes and HER2-negative breast cancer exosomes. Besides, it had high sensitivity and can detect SK-BR-3 exosomes with a concentration as low as 3.4 × 10³ particles mL^-1. Crucially, this method can be applicable to the examination of exosomes in complicated samples, which is anticipated to afford assistance for the screening and prognosis of breast cancer.

Induced ultrasensitive electrochemical biosensor for target MDA-MB-231 cell cytoplasmic protein detection based on RNA-cleavage DNAzyme catalytic reaction

Herein, we implemented RNA-cleaving DNAzymes specific for the endogenous protein of breast cancer cells (MDA-MB -231) and programmed for electrochemical detection. Thionine-modified gold nanoparticles and modified magnetic nanoparticles are attached to the two ends of the DNAzyme molecule. The prepared probe is pulled to the surface of the electrode with the help of a magnetic field, and the signal caused by the electrochemical activity of thionine is observed on the surface of the electrode. The presence of a covalent gold nanoparticle-thionine hybrid as a highly electroactive/enhanced electrochemical label ensures a strong detection signal. After addition of the enzyme activator cofactor (MDA-MB -231 cytoplasmic cell protein), it reacts with the catalytic core of the enzyme sequence in the DNAzyme molecule and triggers the cleavage reaction in the substrate sequence of the DNAzyme molecule. During this process, the gold nanoparticle-thionine labels are detached from the probe and released into the solution. Inductive removal of gold nanoparticles leads to a decrease in the current related to the reduction of thionine on the electrode surface. The results show that this biosensor can detect this protein marker in the linear range of (1.0E-06 to 1.0E+01) pg/ml, with a detection limit (1.0129E-07 pg/ml), using differential pulse voltammetry as a measuring technique. As well as, electrochemical impedance spectroscopy (EIS).

Magneto-Nanomechanical Array Biosensor for Ultrasensitive Detection of Oncogenic Exosomes for Early Diagnosis of Cancers

Exosomes are a class of nanoscale vesicles secreted by cells, which contain abundant information closely related to parental cells. The ultrasensitive detection of cancer-derived exosomes is highly significant for early non-invasive diagnosis of cancer. Here, an ultrasensitive nanomechanical sensor is reported, which uses a magnetic-driven microcantilever array to selectively detect oncogenic exosomes. A magnetic force, which can produce a far greater deflection of microcantilever than that produced by the intermolecular interaction force even with very low concentrations of target substances, is introduced. This method reduced the detection limit to less than 10 exosomes mL^-1 . Direct detection of exosomes in the serum of patients with breast cancer and in healthy people showed a significant difference. This work improved the sensitivity by five orders of magnitude as compared to that of traditional nanomechanical sensing based on surface stress mode. This method can be applied parallelly for highly sensitive detection of other microorganisms (such as bacteria and viruses) by using different probe molecules, which can provide a supersensitive detection approach for cancer diagnosis, food safety, and SARS-CoV-2 infection.

Integrated SERS-Vertical Flow Biosensor Enabling Multiplexed Quantitative Profiling of Serological Exosomal Proteins in Patients for Accurate Breast Cancer Subtyping

Protein profiles of exosomes (EXOs) in clinical samples of cancer patients have become a promising diagnostic and therapeutic biomarker. However, simultaneous quantitative analysis of multiple exosomal proteins of interest remains challenging. To address the unmet need, we develop a paper-based surface-enhanced Raman spectroscopy (SERS)-vertical flow biosensor, named iREX (integrated Raman spectroscopic EXO) biosensor, for multiplexed quantitative profiling of exosomal proteins in clinical serum samples of patients. Utilizing this iREX biosensor, we are able to quantitatively profile MUC1, HER2 and CEA in EXO samples derived from various breast cancer cell subtypes. The results show discriminative expression profiles of the three exosomal proteins in these cell subtypes, which allows for accurate diagnosis and molecular subtyping of breast cancer. We further validate the clinical utility of the iREX biosensor for simultaneous quantitative analysis of MUC1, HER2 and CEA in patient's blood serums, thereby aiding in noninvasive breast cancer subtyping and longitudinal treatment monitoring. Our iREX biosensor integrating the SERS detection in a vertical flow diagnostic device offers great advantages of high sensitivity, molecular specificity, powerful multiplexing capability, and high diagnostic accuracy. We believe that the iREX biosensor could be a promising clinical tool for comprehensive analysis of exosomal proteins in clinical samples for personalized diagnosis and precise management of breast cancer.

Dual-Aptamer-Assisted Ratiometric SERS Biosensor for Ultrasensitive and Precise Identification of Breast Cancer Exosomes

Due to the heterogeneity of breast cancer, its early accurate diagnosis remains a challenge. Exosomes carry abundant genetic materials and proteins and are ideal biomarkers for early cancer detection. Herein, a ratiometric surface-enhanced Raman scattering (SERS) biosensor for exosome detection was constructed using a regularly arranged Au@Ag nanoparticles/graphene oxide (Au@Ag NPs/GO) substrate with 4-nitrothiophenol (4-NTP) molecules as an internal standard. Aptamers of two overexpressed proteins (epithelial cell adhesion molecule and human epidermal growth factor receptor 2) were linked by a short complementary DNA with rhodamine X modified at the 3'-terminal to form V-shaped double-stranded DNA, which attached to the surface of Au@Ag NPs/GO substrate for the selective recognition of breast cancer cell-derived exosomes. In the presence of exosomes, a competitive reaction occurred, resulting in the formation of the V-shaped double-stranded DNA/exosomes complex, and the V-shaped double-stranded DNA separated from the SERS substrate. The SERS signal of rhodamine X on the V-shaped double-stranded DNA decreased with the concentration of exosomes increasing, whereas the SERS signal of 4-NTP on the substrate remained stable. The ratiometric SERS strategy provides huge electromagnetic enhancement and abundant DNA adsorbing sites on the GO layer, achieving a wide detection range of 2.7 × 10² to 2.7 × 10⁸ particles/mL and an ultralow limit of detection down to 1.5 × 10² particles/mL, without the requirement of any nucleic acid amplification. Particularly, the proposed method has significant applications in early cancer diagnosis as it can accurately identify breast cancer cell-derived exosomes in clinical serum samples and can differentiate pancreatic cancer patients and healthy individuals.

Highly Sensitive Aptasensor for Detecting Cancerous Exosomes Based on Clover-like Gold Nanoclusters

Exosome-based liquid biopsy technologies play an increasingly prominent role in tumor diagnosis. However, the simple and sensitive method for counting exosomes still faces considerable challenges. In this work, the CD63 aptamer-modified DNA tetrahedrons on the gold electrode were used as recognition elements for the specific capture of exosomes. Partially complementary DNA probes act as bridges linking trapped exosomes and three AuNP-DNA signal probes. This clover-like structure can tackle the recognition and sensitivity issues arising from the undesired AuNP aggregation event. When cancerous exosomes are present in the system, the high accumulation of methylene blue molecules from DNA-AuNP nanocomposites on the surface of the electrode leads to an intense current signal. According to the results, the aptasensor responds to MCF-7 cell-derived exosomes in the concentration range from 1.0 × 10³ to 1.0 × 10⁸ particles·μL^-1, with the detection limit of 158 particles·μL^-1. Furthermore, the aptasensor has been extended to serum samples from breast cancer patients and exhibited excellent specificity. To sum it up, the aptasensor is sensitive, straightforward, less expensive, and fully capable of receiving widespread application in clinics for tumor monitoring.

A novel highly sensitive compilation-detachment fluorescence sensing strategy based on RNA-cleavage DNAzyme for MDA-MB-231 breast cancer biomarker determination

Herein, we designed a novel and highly sensitive fluorescence multicomponent detachable platform for MDA-MB-231 breast cancer cell detection as a model. The RNA cleavage DNAzyme was used as a central operator of the multicomponent probe through which compilation and induced detachment of probe was done. During the compilation step, the dsDNA-Sybr green 1 complexes on gold nanoparticles (GNP@dsDNA@SG1) were assembled. The intercalated Sybr green in the DNA structure has been used as an amplified signal generator on one site of DNAzyme and magnetic nanoparticles (MNP) act as a biological carrier and probe collector on the opposite side. The enzyme activator co-factor (MDA-MB-231 cell cytoplasmic protein) provokes the activation of the catalytic core of enzyme sequence in the DNAzyme molecule, followed by cleavage reaction in the substrate sequence and releasing GNP@ dsDNA@SG1 into the solution. The results indicate that the Sybr green emission fluorescence (520 nm) increases with the increment of MDA-MB-231 protein concentration in the linear dynamic range of 8.10 × 10^-2 to 1.95 ng ml^-1 (0.77 × 10^-3-0.019 cell ml^-1) with a detection limit (LOD) of 1/72 × 10^-2 pg ml^-1 under optimal conditions. The proposed immunosensor has great potential in developing ultrasensitive and rapid diagnostic platforms.

Nanostructures and Nanotechnologies for the Detection of Extracellular Vesicle

Liquid biopsy has been taken as a minimally invasive examination and a promising surrogate to the clinically applied tissue-based test for the diagnosis and molecular analysis of cancer. Extracellular vesicles (EVs) carry complex molecular information from the tumor, allowing for the multicomponent analysis of cancer and would be beneficial to personalized medicine. In this review, the advanced nanomaterials and nanotechniques for the detection and molecular profiling of EVs, highlight the advantages of nanotechnology in the high-purity isolation and the high-sensitive and high-specific identification of EVs, are summarized. An outlook on the clinical application of nanotechnology-based liquid biopsy in the diagnosis, prognostication, and surveillance of cancer is also provided. It provides information for developing liquid biopsy based on EVs by discussing the advantages and challenges of functionalized nanomaterials and various nanotechnologies.

Nanotechnology-Inspired Extracellular Vesicles Theranostics for Diagnosis and Therapy of Central Nervous System Diseases

Shuttling various bioactive substances across the blood-brain barrier (BBB) bidirectionally, extracellular vesicles (EVs) have been opening new frontiers for the diagnosis and therapy of central nervous system (CNS) diseases. However, clinical translation of EV-based theranostics remains challenging due to difficulties in effective EV engineering for superior imaging/therapeutic potential, ultrasensitive EV detection for small sample volume, as well as scale-up and standardized EV production. In the past decade, continuous advancement in nanotechnology provided extensive concepts and strategies for EV engineering and analysis, which inspired the application of EVs for CNS diseases. Here we will review the existing types of EV-nanomaterial hybrid systems with improved diagnostic and therapeutic efficacy for CNS diseases. A summary of recent progress in the incorporation of nanomaterials and nanostructures in EV production, separation, and analysis will also be provided. Moreover, the convergence between nanotechnology and microfluidics for integrated EV engineering and liquid biopsy of CNS diseases will be discussed.

Overview on the Design of Magnetically Assisted Electrochemical Biosensors

Electrochemical biosensors generally require the immobilization of recognition elements or capture probes on the electrode surface. This may limit their practical applications due to the complex operation procedure and low repeatability and stability. Magnetically assisted biosensors show remarkable advantages in separation and pre-concentration of targets from complex biological samples. More importantly, magnetically assisted sensing systems show high throughput since the magnetic materials can be produced and preserved on a large scale. In this work, we summarized the design of electrochemical biosensors involving magnetic materials as the platforms for recognition reaction and target conversion. The recognition reactions usually include antigen-antibody, DNA hybridization, and aptamer-target interactions. By conjugating an electroactive probe to biomolecules attached to magnetic materials, the complexes can be accumulated near to an electrode surface with the aid of external magnet field, producing an easily measurable redox current. The redox current can be further enhanced by enzymes, nanomaterials, DNA assemblies, and thermal-cycle or isothermal amplification. In magnetically assisted assays, the magnetic substrates are removed by a magnet after the target conversion, and the signal can be monitored through stimuli-response release of signal reporters, enzymatic production of electroactive species, or target-induced generation of messenger DNA.

Electrochemical nano-sensing interface for exosomes analysis and cancer diagnosis

Exosomes are a class of the nanosized extracellular vesicles, which have emerged as representative liquid biopsy biomarkers. To date, the electrochemical nanosensors are of great significance in the exosome detection with the advantages of easy operation, high accuracy and reliable repeatability. Especially, the growing field of nano interface has provided the electrochemical sensing platforms for the accurate exosomes analysis. The incorporation of multiple nanomaterials can take advantages and synergistic properties of functional units. So, based on the integration of with nanomaterial-based signal transduction and specific biorecognition, the nano-sensing interface provides excellent electrochemical features owing to rapid mass transport and excellent conductivity. The nano-sensing interface with a wide variety of morphologies and structure also provides the large active surface area for the immobilization of bio-capturing agents. Furthermore, through the design of nanostructured electrode array, the efficiency of transducer can be greatly improved. It should be noticed that the elaboration of a proper sensor requires the profound knowledge of the nano-sensing interface. Therefore, this article presents a review of the recent advance in exosomes detection based on the electrochemical nano-sensing interface, including electrochemical analysis principles, exosome sensing mechanisms, nano-interface construction strategies, as well as the typical diagnosis application. In particular, the article is focused on the exploration of the various electrochemical sensing performance of nano-interface in the exosome detection. We have also prospected the future trend and challenge of the electrochemical nano-sensing interface for exosomes analysis in clinical cancer diagnosis.

Recent Advances in Detection for Breast-Cancer-Derived Exosomes

Breast cancer is the most common malignant tumor in women, its incidence is secret, and more than half of the patients are diagnosed in the middle and advanced stages, so it is necessary to develop simple and efficient detection methods for breast cancer diagnosis to improve the survival rate and quality of life of breast cancer patients. Exosomes are extracellular vesicles secreted by all kinds of living cells, and play an important role in the occurrence and development of breast cancer and the formation of the tumor microenvironment. Exosomes, as biomarkers, are an important part of breast cancer fluid biopsy and have become ideal targets for the early diagnosis, curative effect evaluation, and clinical treatment of breast cancer. In this paper, several traditional exosome detection methods, including differential centrifugation and immunoaffinity capture, were summarized, focusing on the latest research progress in breast cancer exosome detection. It was summarized from the aspects of optics, electrochemistry, electrochemiluminescence and other aspects. This review is expected to provide valuable guidance for exosome detection of clinical breast cancer and the establishment of more reliable, efficient, simple and innovative methods for exosome detection of breast cancer in the future.

Introduction of Nanomaterials to Biosensors for Exosome Detection: Case Study for Cancer Analysis

Exosomes have been gaining attention for early cancer diagnosis owing to their biological functions in cells. Several studies have reported the relevance of exosomes in various diseases, including pancreatic cancer, retroperitoneal fibrosis, obesity, neurodegenerative diseases, and atherosclerosis. Particularly, exosomes are regarded as biomarkers for cancer diagnosis and can be detected in biofluids, such as saliva, urine, peritoneal fluid, and blood. Thus, exosomes are advantageous for cancer liquid biopsies as they overcome the current limitations of cancer tissue biopsies. Several studies have reported methods for exosome isolation, and analysis for cancer diagnosis. However, further clinical trials are still required to determine accurate exosome concentration quantification methods. Recently, various biosensors have been developed to detect exosomal biomarkers, including tumor-derived exosomes, nucleic acids, and proteins. Among these, the exact quantification of tumor-derived exosomes is a serious obstacle to the clinical use of liquid biopsies. Precise detection of exosome concentration is difficult because it requires clinical sample pretreatment. To solve this problem, the use of the nanobiohybrid material-based biosensor provides improved sensitivity and selectivity. The present review will discuss recent progress in exosome biosensors consisting of nanomaterials and biomaterial hybrids for electrochemical, electrical, and optical-based biosensors.

Current Perspectives in Graphene Oxide-Based Electrochemical Biosensors for Cancer Diagnostics

Since the first commercial biosensor device for blood glucose measurement was introduced in the 1970s, many “biosensor types” have been developed, and this research area remains popular worldwide. In parallel with some global biosensor research reports published in the last decade, including a great deal of literature and industry statistics, it is predicted that biosensor design technologies, including handheld or wearable devices, will be preferred and highly valuable in many areas in the near future. Biosensors using nanoparticles still maintain their very important place in science and technology and are the subject of innovative research projects. Among the nanomaterials, carbon-based ones are considered to be one of the most valuable nanoparticles, especially in the field of electrochemical biosensors. In this context, graphene oxide, which has been used in recent years to increase the electrochemical analysis performance in biosensor designs, has been the subject of this review. In fact, graphene is already foreseen not only for biosensors but also as the nanomaterial of the future in many fields and is therefore drawing research attention. In this review, recent and prominent developments in biosensor technologies using graphene oxide (GO)-based nanomaterials in the field of cancer diagnosis are briefly summarized.

Exosome Processing and Characterization Approaches for Research and Technology Development

Exosomes are extracellular vesicles that share components of their parent cells and are attractive in biotechnology and biomedical research as potential disease biomarkers as well as therapeutic agents. Crucial to realizing this potential is the ability to manufacture high-quality exosomes; however, unlike biologics such as proteins, exosomes lack standardized Good Manufacturing Practices for their processing and characterization. Furthermore, there is a lack of well-characterized reference exosome materials to aid in selection of methods for exosome isolation, purification, and analysis. This review informs exosome research and technology development by comparing exosome processing and characterization methods and recommending exosome workflows. This review also provides a detailed introduction to exosomes, including their physical and chemical properties, roles in normal biological processes and in disease progression, and summarizes some of the on-going clinical trials.

Exosome detection via surface-enhanced Raman spectroscopy for cancer diagnosis

As nanoscale extracellular vesicles, exosomes are secreted by various cell types, and they are widely distributed in multiple biological fluids. Studies have shown that tumor-derived exosomes can carry a variety of primary tumor-specific molecules, which may represent a novel tool for the early detection of cancer. However, the clinical translation of exosomes remains a challenge due to the requirement of large quantities of samples when enriching the cancer-related exosomes in biological fluids, the insufficiency of traditional techniques for exosome subpopulations, and the complex exosome isolation of the current commercially available exosome phenotype profiling approaches. The evolving surface-enhanced Raman scattering (SERS) technology, with properties of unique optoelectronics, easy functionalization, and the particular interaction between light and nanoscale metallic materials, can achieve sensitive detection of exosomes without large quantities of samples and multiplexed phenotype profiling, providing a new mode of real-time and noninvasive analysis for cancer patients. In the present review, we mainly discussed exosome detection based on SERS, especially SERS immunoassay. The basic structure and function of exosomes were firstly introduced. Then, recent studies using the SERS technique for cancer detection were critically reviewed, which mainly included various SERS substrates, biological modification of SERS substrates, SERS-based exosome detection, and the combination of SERS and other technologies for cancer diagnosis. This review systematically discussed the essential aspects, limitations, and considerations of applying SERS technology in the detection and analysis of cancer-derived exosomes, which could provide a valuable reference for the early diagnosis of cancer through SERS technology. STATEMENT OF SIGNIFICANCE: Surface-enhanced Raman scattering (SERS) has been applied to exosomes detection to obtain better diagnostic results. In past three years, several reviews have been published in exosome detection, which were narrowly focus on methods of exosome detection. Selection and surface functionalization of the substrate and the combination detection with different methods based on SERS will provide new strategies for the detection of exosomes. This review will focus on the above aspects. This emerging detection method is constantly evolving and contributing to the early discovery of diseases in the future.

Harnessing the Therapeutic Potential of Extracellular Vesicles for Biomedical Applications Using Multifunctional Magnetic Nanomaterials

Extracellular vesicles (e.g., exosomes) carrying various biomolecules (e.g., proteins, lipids, and nucleic acids) have rapidly emerged as promising platforms for many biomedical applications. Despite their enormous potential, their heterogeneity in surfaces and sizes, the high complexity of cargo biomolecules, and the inefficient uptake by recipient cells remain critical barriers for their theranostic applications. To address these critical issues, multifunctional nanomaterials, such as magnetic nanomaterials, with their tunable physical, chemical, and biological properties, may play crucial roles in next-generation extracellular vesicles (EV)-based disease diagnosis, drug delivery, tissue engineering, and regenerative medicine. As such, one aims to provide cutting-edge knowledge pertaining to magnetic nanomaterials-facilitated isolation, detection, and delivery of extracellular vesicles and their associated biomolecules. By engaging the fields of extracellular vesicles and magnetic nanomaterials, it is envisioned that their properties can be effectively combined for optimal outcomes in biomedical applications.

Colorimetric Aptasensor Based on Fe₃O₄-Cu2+ Nanozyme with Intrinsic Peroxidase-Like Activity in the Detection of Breast Cancer Exosomes

Because breast cancer cells such as MCF-7, exhibit vital and developmental signs by exosome secretion, diagnosing them in the blood can provide a good index of the presence of breast cancer. However, accurate and inexpensive detection of exosomes in clinical practice faces challenges. Therefore, in the presents study, an aptasensor based on CD63 aptameriron oxide-copper ion nanozymes (Fe₃O₄-Cu²⁺-NZs) was designed with the ability of the CD63 aptamer to interact with the exosome and the release of the Fe₃O₄-Cu²⁺-NZs for peroxidase-like activity on the tetramethylbenzidine (TMB). After fabrication of CD63 aptamer-Fe₃O₄-Cu²⁺-NZs based on hydrothermal method, their physicochemical properties were investigated with the SEM, TEM, DLS, Zeta, XRD and magnetization. To investigate the interaction of CD63 aptamer-Fe₃O₄-Cu²⁺-NZs with exosomes, the required exosomes were extracted from cultured MCF-7 cells. The performance of CD63 aptamer-Fe₃O₄-Cu²⁺-NZs on TMB degradation in the presence and absence of exosomes was investigated through UV-vis adsorption and ocular observations based on colour changes on laboratory and real samples. The results show that the absence of exosomes significantly inhibited the peroxidase-like activity of CD63 aptamer-Fe₃O₄-Cu²⁺-NZs due to the aptamer coating. Under optimal conditions, the designed CD63 aptamer-Fe₃O₄-Cu²⁺-NZs is capable of detecting exosomes in the range of 1.4 × 10⁴-5.6 × 10⁵ particles/μL with a detection limit of 5.91 × 10³ particles/μL. Also, this method showed a satisfactory outcome in detection of cancer cells in real samples. Overall, this colorimetric aptasensor can be used to diagnose breast cancer cells based on a simple and inexpensive approach.

Recent Advances in Aptamer-Based Liquid Biopsy

Liquid biopsy capable of noninvasive and real-time molecular profiling is considered as a breakthrough technology, endowing an opportunity for precise diagnosis of individual patients. Extracellular vesicles (EVs) and circulating tumor cells (CTCs) consisting of substantial disease-related molecular information play an important role in liquid biopsy. Therefore, it is critically significant to exploit high-performance recognition ligands for efficient isolation and analysis of EVs and CTCs from complex body fluids. Aptamers exhibit extraordinary merits of high specificity and affinity, which are considered as superior recognition ligands for liquid biopsy. In this review, we first summarize recent advanced strategies for the evolution of high-performance aptamers and the construction of various aptamer-based recognition elements. Subsequently, we mainly discuss the isolation and analysis of EVs and CTCs based on the aptamer functioned biomaterials/biointerface. Ultimately, we envision major challenges and future direction of aptamer-based liquid biopsy for clinical utilities.

Multiplexed analysis of small extracellular vesicle-derived mRNAs by droplet digital PCR and machine learning improves breast cancer diagnosis

Breast cancer has become the leading cause of global cancer incidence and a serious threat to women's health. Accurate diagnosis and early treatment are of great importance to prognosis. Although clinically used diagnostic approaches can be used for cancer screening, accurate diagnosis of breast cancer is still a critical unmet need. Here, we report a 4-plex droplet digital PCR technology for simultaneous detection of four small extracellular vesicle (sEV)-derived mRNAs (PGR, ESR1, ERBB2 and GAPDH) in combination with machine learning (ML) algorithms to improve breast cancer diagnosis. We evaluate the diagnsotic results with and without the assistance of the ML models. The results indicate that ML-assisted analysis exhibits higher diagnostic performance even using a single marker for breast cancer diagnosis, and demonstrate improved diagnostic performance under the best combination of biomarkers and suitable ML diagnostic model. Therefore, multiple sEV-derived mRNAs analysis coupled with ML not only provides the best combination of markers for breast cancer diagnosis, but also significantly improves the diagnostic efficiency of breast cancer.

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.