Dual rolling circle amplification-enabled ultrasensitive multiplex detection of exosome biomarkers using electrochemical aptasensors

Target-induced proximity ligation triggers polymerase chain reaction for subset tracing of small extracellular vesicles

The considerable abundance and remarkable stability of sEVs provide substantial benefits for diagnosing Alzheimer's disease. Therefore, precise tracking subtypes of small extracellular vesicles (sEVs) is crucial for screening novel diagnostic biomarkers and developing therapeutic technologies. We propose a three-target recognition-mediated proximity ligation assay for the precise identification of sEV subtypes utilizing three specifically designed probes: one for the exosomal surface protein CD63 recognition, one for fixing the biolipid layer, and the third for the identification of distinctive protein associated with a specific subtype of sEVs (L1CAM positive sEVs). The developed sEVs subtype tracing approach integrates proximity ligation of the three probes to specifically bind to surface biomarkers and polymerase chain reaction (PCR) for signal amplification, enabling "AND" logic analysis of three essential components on sEVs. This method can be utilized for both sEVs quantification and subtype tracing. The proposed approach demonstrated a low limit of detection for neuronal sEVs at 2.5 particles/μL, according to this design. In addition, we utilized this technique to measure plasma sEV levels in individuals with Alzheimer's disease and examined its early diagnostic effectiveness. The approach can assess the concentration ratios of neuronal sEVs and cancer-derived sEVs, highlighting its potential for clinical applications. In addition, the approach enables precise tracing and identification of sEVs subtypes, hence facilitating extensive applications in biological science, biomedical engineering, and personalized medicine.

Innovations in aptamer-based biosensors for detection of pathogenic bacteria: Recent advances and perspective

The rapid and accurate detection of pathogenic bacteria is a pressing concern in the fields of public health, food safety, and environmental monitoring. However, traditional methods often prove to be slow and difficult to quantify accurately. Thus, there is a pressing need to develop advanced methods that enable rapid detection which is sensitive and inexpensive. Aptamers, which are short nucleic acid sequences derived through a process called systematic evolution of ligands by exponential enrichment (SELEX), offer a promising alternative due to their unique binding characteristics. These properties confer several advantages over traditional antibodies, making aptamers effective and versatile bioreceptors for pathogen detection. Recent advancements have led to the development of various aptamer-based biosensors utilizing diverse signaling strategies, including optical, electrochemical, mass-based, paper-based and microchip capillary electrophoresis (MCE) methods. The integration of nanomaterials with aptamer technology has further enhanced biosensor performance by improving sensitivity and enabling real-time monitoring of bacterial contamination. In this review, the focus is on current developments in aptamer-based biosensors and their potential applications in clinical diagnostics, food safety and environmental monitoring. As research progresses, the customization of aptamer sequences for specific targets is expected to yield tailored diagnostic solutions, ultimately improving patient outcomes and public health responses. The continued exploration of aptamer technology marks a significant advancement in methodologies for detecting pathogenic bacteria, highlighting not only the promise of aptamers as effective detection tools but also the critical need for multidisciplinary collaboration, integrating molecular biology, materials science, and microfluidics, to overcome challenges in this field.

Enrichment and Detection of HER2-Expressing Extracellular Vesicles Based on DNA Tetrahedral Nanostructures: A New Strategy for Liquid Biopsy in Breast Cancer

Extracellular vesicles (EVs) play a crucial role as important mediators of intercellular communication in the progression of tumors. The capture and analysis of tumor-derived EVs offer new possibilities for the application of cancer liquid biopsies. This study aims to construct a DNA tetrahedral nanostructure that specifically recognizes HER2 and CD63, enabling the effective enrichment and detection of HER2-expressing EVs (HEVs). We enriched HEVs from cell lines and 13 random clinical samples and validated their characteristics by dynamic light scattering, transmission electron microscopy, and Western blotting. Further, we detected HEVs levels in clinical samples. The HEVs levels in HER2-positive breast cancer patients were significantly higher than those in healthy/benign controls (mean, 4.737 vs 4.160 vs 4.144 U/μL, P < 0.0001), displaying a concentration gradient across different HER2 expression levels. This study establishes an approach for HEV detection, thus providing a new tool for the diagnosis of HER2-positive breast cancer.

Ultrasensitive determination of exosomes by tyramine-assisted colorimetric sensors for tumor diagnosis

Exosomes, which are recognized as a kind of valuable liquid biopsy biomarker, exhibit significant application potential in cancer diagnosis. Therefore, it is crucial to establish a reliable detection method for their clinical application. In this study, we have presented an ultrasensitive aptasensor for the visual detection of exosomes by employing tyramine-assisted dual-signal amplification technology. First, we utilized magnetic beads modified with the nucleolin aptamer (MNPs-Aptnucleolin) to capture exosomes. This modification not only enhanced specificity, but also reduced interference of complex sample components. The captured exosomes as a rich source of proteins can bind with multiple biotinyl-tyramide (Bio-TR) molecules through a catalytic reaction involving horseradish peroxidase (HRP) and H2O2. Second, streptavidin-HRP complex-modified gold nanoparticles (GNPs-Str-HRP) as a signal amplification probe was introduced to further enhance the detection signal by binding to Bio-TR. Lastly, the addition of 3,3',5,5'-tetramethylbenzidine (TMB) solution induced a visible color change, enabling quantification of the exosome concentration. This dual-signal amplification strategy resulted in a low limit of detection (LOD) of 63 particles per μL, and it also demonstrated accurate visual diagnosis capabilities for clinical samples. The successful implementation of this approach suggests its potential as a promising tool for point-of-care testing (POCT) in cancer diagnostics.

An easy-operation aptasensor for simultaneous detection of multiple tumor-associated exosomal proteins based on multicolor fluorescent DNA nanoassemblies

As a promising liquid biopsy biomarker, exosomes have demonstrated great potential and advantages in the noninvasive tumor diagnosis. However, an accurate and sensitive method for tumors-associated exosomes detection is scarce. Herein, we presented an easy-operation aptasensor which simultaneously detect multiple exosomal proteins by using multicolor fluorescent DNA nanoassemblies (FDNs) and CD63 aptamer-modified magnetic beads (MNPs-AptCD63). In this system, the FDNs were firstly constructed by encapsulating different quantum dots (QDs) into rolling circle amplification (RCA) products that contained different aptamer sequences. Thus, the FDNs could selectively recognize the different exosomal proteins captured by the MNPs-AptCD63, and achieve the multiplex and sensitive detection according to the fluorescence of QDs. Benefiting from the signal amplification capacity and high selectivity of FDNs, this aptasensor not only could detect exosomes as low as 650 particles/μL, but also showed accurate analysis in clinical samples. In addition, we can also achieve point-of-care testing (POCT) due to the simple analysis steps and naked-eye observable fluorescence of QDs under the ultraviolet irradiation. We believe that our aptasensor could provide a promising platform for exosomes-based personalized diagnosis and precise monitoring of human health.

Efficiency of electrochemical immuno- vs. apta(geno)sensors for multiple cancer biomarkers detection

The interest in biosensors technology has been constantly growing over the last few years. It is still the biggest challenge to design biosensors able to detect two or more analytes in a single measurement. Electrochemical methods are frequently used for this purpose, mainly due to the possibility of applying two or more different redox labels characterized by independent and distinguished electrochemical signals. In addition to antibodies, nucleic acids (aptamers) have been increasingly used as bioreceptors in the construction of such sensors. Within this review paper, we have collected the examples of electrochemical immuno- and geno(apta)sensors for simultaneous detection of multiple analytes. Based on many published literature examples, we have emphasized the recent application of multiplexed platforms for detection of cancer biomarkers. It has allowed us to compare the progress in design strategies, including novel nanomaterials and amplification of signals, to get as low as possible limits of detection. We have focused on multi-electrode and multi-label strategies based on redox-active labels, such as ferrocene, anthraquinone, methylene blue, thionine, hemin and quantum dots, or metal ions such as Ag+, Pb2+, Cd2+, Zn2+, Cu2+ and others. We have finally discussed the possible way of development, challenges and prospects in the area of multianalyte electrochemical immuno- and geno(apta)sensors.

Enhancing multiplex detection capabilities of the Cas12a/blocker DNA system

In the field of molecular diagnostics, the demand for multiplex detection, aimed at reducing overall analysis costs and streamlining procedures, is on the rise, prompting ongoing developments in various technologies. In this study, we developed a novel system, the split T7 promoter-based three-way junction-transcription, coupled with Cas12a/Blocker DNA (T3-CaB), for the multiplex detection of target nucleic acids. The T3-CaB system builds upon the foundation of the T3 system, generating numerous RNA transcripts upon encountering target nucleic acids. Subsequently, these RNA transcripts displace the blocker DNA from reporter DNA, allowing active Cas12a to engage in efficient trans-cleavage reaction on the reporter DNA, resulting in a strong fluorescence signal. Importantly, the proposed system operates at the isothermal condition (37 °C), with the entire analysis completed within 90 min. Further, the detection performance of the proposed system surpasses that of the preceding Cas12a/Blocker DNA system. Model targets, namely the 16S rRNA of Staphylococcus aureus and Escherichia coli, were selected, and a successful demonstration of multiplex detection was achieved. This technology holds promise for broadening the applicability of CRISPR/Cas-based diagnostics, especially in settings necessitating multiplex detection capabilities.

Multispectral pathogens detection in food using multiplex hyperbranched saltatory rolling circle amplification

Foodborne illnesses caused by Salmonella and Staphylococcus aureus are a significant public health concern, leading to societal and economic repercussions. It is important to develop a simple and straightforward bacteria detection and identification method. A triple-probe multiplex rolling circle amplification technique has been developed to simultaneously detect Salmonella Typhimurium and S. aureus. This method utilizes fluorophore-labeled long padlock probes targeting S. Typhimurium invA and S. aureus glnA specific genes, along with a pH-based detection approach for direct visual identification. The multiplex hyperbranched saltatory rolling circle amplification assay at 30 °C has showed promising results with synthetic targets within 30 min and real bacteria within 2 h after establishing the detection settings. The assay is specific for S. aureus and S. Typhimurium, with a limit of detection of 39 μM for fluorescence and 78 μM for colorimetric. In the simulative test of this method for the detection of S. Typhimurium and S. aureus in milk, the limit of detection for the fluorescence signal after 2 h of amplification was 10 CFU/mL and 5 CFU/mL, respectively. The detection method was evaluated to be stable enough to detect pathogen for 3.29 months. Consequently, this triple-probe-multiplex rolling circle amplification method displays notable specificity, sensitivity, as well as ease of interpretation when testing food samples for harmful pathogens.

Colorimetric aptasensor based on temporally controllable light-stimulated oxidase-mimicking fluorescein for the sensitive detection of exosomes in mild conditions

Analysis of exosomes provides important information for rapid and non-invasive screening of tumors. However, sensitive and convenient detection of exosomes remains technically challenging to date. Herein, a colorimetric aptasensor based on the light-stimulated oxidase-mimicking activity of FITC was constructed for detecting ovarian cancer (OC) exosomes. The aptasensor contained an EpCAM aptamer to capture OC exosomes. Cholesterol and fluorescein (FITC) were used to modify either end of the DNA (DNA anchor). The DNA anchor could combine with exosomes through a hydrophobic reaction between cholesterol and the lipid membrane. FITC oxidized 3,3',5,5'-tetramethylbenzidine (TMB) under a 365 nm LED light source in a temporally controllable manner under mild conditions, causing the solution to change from colorless to blue, and the corresponding UV-vis absorbance increased. Based on this principle, the exosomes were qualitatively analyzed by observing the color change with the naked eye. In parallel, the exosome concentration was also detected using UV-vis spectrophotometry. The linear range was from 2 × 105 to 100 × 105 particles per mL with a limit of detection of 1.77 × 105 particles per mL. The developed aptasensor also exhibited favorable selectivity and could discriminate the exosomes from OC cells and normal cells. Besides, the receiver operating characteristic (ROC) curve demonstrates that it is possible to distinguish between patients with OC and healthy donors (HDs) using exosomes as the biomarker. Our technology may expand the applications of DNA-based detection method-enabled OC diagnostic tools.

The combination of DNA nanostructures and materials for highly sensitive electrochemical detection

Due to the wide range of electrochemical devices available, DNA nanostructures and material-based technologies have been greatly broadened. They have been actively used to create a variety of beautiful nanostructures owing to their unmatched programmability. Currently, a variety of electrochemical devices have been used for rapid sensing of biomolecules and other diagnostic applications. Here, we provide a brief overview of recent advances in DNA-based biomolecular assays. Biosensing platform such as electrochemical biosensor, nanopore biosensor, and field-effect transistor biosensors (FET), which are equipped with aptamer, DNA walker, DNAzyme, DNA origami, and nanomaterials, has been developed for amplification detection. Under the optimal conditions, the proposed biosensor has good amplification detection performance. Further, we discussed the challenges of detection strategies in clinical applications and offered the prospect of this field.

Proximity hybridization based "turn-on" DNA tweezers for accurate and enzyme-free small extracellular vesicle analysis

Small extracellular vesicles (sEVs) are a type of extracellular vesicle that carries many types of molecular information. The identification of sEVs is essential for the non-invasive detection and treatment of illnesses. Hence, there is a significant need for the development of simple, sensitive, and precise methods for sEV detection. Herein, a DNA tweezers-based assay utilizing a "turn-on" mechanism and proximity ligation was suggested for the efficient and rapid detection of sEVs through amplified fluorescence. The target facilitates the proximity combination of the C1 probe and C2 probe, resulting in the formation of a complete extended sequence. The elongated sequence can cyclically initiate the hairpin probe (HP), leading to the activation of DNA tweezers. An excellent linear correlation was achieved, with a limit of detection of 57 particles per μL. Furthermore, it has been effectively employed to analyze sEVs under intricate experimental conditions, demonstrating a promising and pragmatic prospect for future applications. Given that the identification of sEVs was successfully accomplished using a single-step method that exhibited exceptional sensitivity and strong resistance to interference, the proposed technique has the potential to provide a beneficial platform for accurate recognition of sEVs and early detection of diseases.

Nanoarchitectonics-based electrochemical aptasensors for highly efficient exosome detection

Exosomes, a type of extracellular vesicles, have attracted considerable attention due to their ability to provide valuable insights into the pathophysiological microenvironment of the cells from which they originate. This characteristic implicates their potential use as diagnostic disease biomarkers clinically, including cancer, infectious diseases, neurodegenerative disorders, and cardiovascular diseases. Aptasensors, which are electrochemical aptamers based biosensing devices, have emerged as a new class of powerful detection technology to conventional methods like ELISA and Western analysis, primarily because of their capability for high-performance bioanalysis. This review covers the current research landscape on the detection of exosomes utilizing nanoarchitectonics strategy for the development of electrochemical aptasensors. Strategies involving signal amplification and biofouling prevention are discussed, with an emphasis on nanoarchitectonics-based bio-interfaces, showcasing their potential to enhance sensitivity and selectivity through optimal conduction and mass transport properties. The ongoing challenges to broaden the clinical applications of these biosensors are also highlighted.

Multiplex electrochemical sensing platforms for the detection of breast cancer biomarkers

Herein, advancements in electroanalytical devices for the simultaneous detection of diverse breast cancer (BC) markers are demonstrated. This article identifies several important areas of exploration for electrochemical diagnostics and highlights important factors that are pivotal for the successful deployment of novel bioanalytical devices. We have highlighted that the limits of detection (LOD) reported for the multiplex electrochemical biosensor can surpass the sensitivity displayed by current clinical standards such as ELISA, FISH, and PCR. HER-2; a breast cancer marker characterised by increased metastatic potential, more aggressive development, and poor clinical outcomes; can be sensed with a LOD of 0.5 ng/ml using electrochemical multiplex platforms, which falls within the range of that measured by ELISA (from picogram/ml to nanogram/ml). Electrochemical multiplex biosensors are reported with detection limits of 0.53 ng/ml and 0.21 U/ml for MUC-1 and CA 15-3, respectively, or 5.8 × 10-3 U/ml for CA 15-3 alone. The sensitivity of electrochemical assays is improved when compared to conventional analysis of MUC-1 protein which is detected at 11-12 ng/ml, and ≤30 U/ml for CA 15-3 in the current clinical blood tests. The LOD for micro-ribonucleic acid (miRNA) biomarkers analyzed by electrochemical multiplex assays were all notedly superior at 9.79 × 10-16 M, 3.58 × 10-15 M, and 2.54 × 10-16 M for miRNA-155, miRNA-21, and miRNA-16, respectively. The dogma in miRNA testing is the qRT-PCR method, which reports ranges in the ng/ml level for the same miRNAs. Breast cancer exosomes, which are being explored as a new frontier of biosensing, have been detected electrochemically with an LOD of 103-108 particles/mL and can exceed detection limits seen by the tracking and analysis of nanoparticles (∼ 107 particles/ml), flow cytometry, Western blotting and ELISA, etc. A range of concentration at 78-5,000 pg/ml for RANKL and 16-1,000 pg/ml for TNF is reported for ELISA assay while LOD values of 2.6 and 3.0 pg/ml for RANKL and TNF, respectively, are demonstrated by the electrochemical dual immunoassay platform. Finally, EGFR and VEGF markers can be quantified at much lower concentrations (0.01 and 0.005 pg/ml for EGFR and VEGF, respectively) as compared to their ELISA assays (EGRF at 0.31-20 ng/ml and VEGF at 31.3-2,000 pg/ml). In this study we hope to answer several questions: (1) Are the limits of detection (LODs) reported for multiplex electrochemical biosensors of clinical relevance and how do they compare to well-established methods like ELISA, FISH, or PCR? (2) Can a single sensor electrode be used for the detection of multiple markers from one blood drop? (3) What mechanism of electrochemical biosensing is the most promising, and what technological advancements are needed to utilize these devices for multiplex POC detection? (4) Can nanotechnology advance the sensitive and selective diagnostics of multiple BC biomarkers? (5) Are there preferred receptors (antibody, nucleic acid or their combinations) and preferred biosensor designs (complementary methods, sandwich-type protocols, antibody/aptamer concept, label-free protocol)? (6) Why are we still without FDA-approved electrochemical multiplex devices for BC screening?

A dual-cycle amplification-based electrochemical platform for sensitive detection of tobramycin

BACKGROUND

Tobramycin (TOB), an essential aminoglycoside antibiotic in human life, poses potential threats due to its residues in the environment. The primary concern is the adverse impact of excessive TOB on human kidneys, hearing, and other organs, significantly affecting human health. Constructing a sensitive electrochemical platform for simple and rapid trace detection is crucial. Herein, to enhance the sensitivity of TOB detection in the environment and mitigate the risks associated with residual antibiotics, an ultrasensitive electrochemical aptasensor was developed.

RESULTS

The sensor employs a dual-cycle amplification strategy involving catalytic hairpin assembly (CHA) and exonuclease III (Exo III) for efficient signal amplification. Simultaneously, the electrode performance was optimized by incorporating gold nanowires (AuNWs) onto the surface of reduced graphene oxide (PDA-rGO). Specifically, in the presence of TOB, which binds to the aptamer (Apt), dsDNA dissociates, releasing cDNA to open hairpin 1 (HP1) and initiate the CHA cycle with the participation of hairpin 2 (HP2). Exo III shears HP1 in the HP1/HP2 complex, freeing HP2 to participate in the CHA cycle again. Ultimately, a significant amount of signal label is retained on the electrode by hybridizing with sheared HP1, generating a robust electrical signal.

SIGNIFICANCE

Through the signal amplification strategy, the aptasensor design provides a broad linear range of 0.005-500 nM, with a low detection limit of 0.112 pM for TOB. It is worth mentioning that the aptasensor displayed favorable stability, specificity, and reproducibility, and has been successfully applied to practical samples, demonstrating its utility in practical applications.

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.

Development of a Novel DNA Aptamer Targeting Colorectal Cancer Cell-Derived Small Extracellular Vesicles as a Potential Diagnostic and Therapeutic Agent

Colorectal cancer (CRC) as the second leading cause of global cancer deaths poses critical challenges in clinical settings. Cancer-derived small extracellular vesicles (sEVs), which are secreted by cancer cells, have been shown to mediate tumor development, invasion, and even metastasis, and have thus received increasing attention for the development of cancer diagnostic or therapeutic platforms. In the present study, the sEV-targeted systematic evolution of ligands by exponential enrichment (E-SELEX) is developed to generate a high-quality aptamer (CCE-10F) that recognizes and binds to CRC-derived sEVs. Via an in-depth investigation, it is confirmed that this novel aptamer possesses high affinity (Kd = 3.41 nm) for CRC-derived sEVs and exhibits a wide linear range (2.0 × 104 -1.0 × 106 particles µL-1 ) with a limit of detection (LOD) of 1.0 × 103 particles µL-1 . Furthermore, the aptamer discriminates CRC cell-derived sEVs from those derived from normal colon cell, human serum, and other cancer cells, showing high specificity for CRC cell-derived sEVs and significantly suppresses the critical processes of metastasis, including cellular migration, invasion, and angiogenesis, which are originally induced by sEVs themselves. These findings are highly encouraging for the potential use of the aptamer in sEV-based diagnostic and therapeutic applications.

A signal-off aptasensor for the determination of Acinetobacter baumannii by using methylene blue as an electrochemical probe

An electrochemical aptasensor has been developed to detect Acinetobacter baumannii (A. baumannii). The proposed system was developed by modifying carbon screen-printed electrodes (CSPEs) with a synthesized MWCNT@Fe₃O₄@SiO₂-Cl nanocomposite and then binding A. baumannii-specific aptamer using covalent immobilization on the modified electrode surface and the interaction of methylene blue (MB) with Apt as an electrochemical redox indicator. As a result of the incubation of the A. baumannii bacteria as a target on the proposed aptasensor, a cathodic peak current density (J_pc) of MB decreased due to the formation of the Apt-A. baumannii complex and MB being released from the immobilized Apt on the surface of the modified electrode. In addition to increasing the electron transfer kinetics, the nanocomposite provides a relatively stable matrix to improve the loading Apt sequence. The suggested aptasensor was demonstrated to be capable of detecting A. baumannii with a linear range of 10.0-1.0 × 10⁷ colony-forming unit (CFU) mL^-1 and a detection limit of 1 CFU mL^-1 (S/N = 3) using differential pulse voltammetry (DPV) studies at a working potential of ~0.29 V and a scan rate of 100 mV s^-1. The outcomes revealed that the aptasensor exhibited high A. baumannii detection sensitivity, stability, reproducibility, and specificity.

Prospects of Microfluidic Technology in Nucleic Acid Detection Approaches

Conventional diagnostic techniques are based on the utilization of analyte sampling, sensing and signaling on separate platforms for detection purposes, which must be integrated to a single step procedure in point of care (POC) testing devices. Due to the expeditious nature of microfluidic platforms, the trend has been shifted toward the implementation of these systems for the detection of analytes in biochemical, clinical and food technology. Microfluidic systems molded with substances such as polymers or glass offer the specific and sensitive detection of infectious and noninfectious diseases by providing innumerable benefits, including less cost, good biological affinity, strong capillary action and simple process of fabrication. In the case of nanosensors for nucleic acid detection, some challenges need to be addressed, such as cellular lysis, isolation and amplification of nucleic acid before its detection. To avoid the utilization of laborious steps for executing these processes, advances have been deployed in this perspective for on-chip sample preparation, amplification and detection by the introduction of an emerging field of modular microfluidics that has multiple advantages over integrated microfluidics. This review emphasizes the significance of microfluidic technology for the nucleic acid detection of infectious and non-infectious diseases. The implementation of isothermal amplification in conjunction with the lateral flow assay greatly increases the binding efficiency of nanoparticles and biomolecules and improves the limit of detection and sensitivity. Most importantly, the deployment of paper-based material made of cellulose reduces the overall cost. Microfluidic technology in nucleic acid testing has been discussed by explicating its applications in different fields. Next-generation diagnostic methods can be improved by using CRISPR/Cas technology in microfluidic systems. This review concludes with the comparison and future prospects of various microfluidic systems, detection methods and plasma separation techniques used in microfluidic devices.

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.

A Comprehensive Review on Electrochemical Nano Biosensors for Precise Detection of Blood-Based Oncomarkers in Breast Cancer

Breast cancer (BC), one of the most common and life-threatening cancers, has the highest incidence rate among women. Early diagnosis of BC oncomarkers is considered the most effective strategy for detecting and treating BC. Finding the type and stage of BC in women as soon as possible is one of the greatest ways to stop its incidence and negative effects on medical treatment. The development of biosensors for early, sensitive, and selective detection of oncomarkers has recently attracted much attention. An electrochemical nano biosensor (EN) is a very suitable option for a powerful tool for cancer diagnosis. This comprehensive review provides information about the prevalence and pathobiology of BC, recent advances in clinically available BC oncomarkers, and the most common electrochemical nano biosensors for point-of-care (POC) detection of various BC oncomarkers using nanomaterial-based signal amplification techniques.

Recent advances in electrochemical nanomaterial-based aptasensors for the detection of cancer biomarkers

New technologies have provided suitable tools for rapid diagnosis of cancer which can reduce treatment costs and even increase patients' survival rates. Recently, the development of electrochemical aptamer-based nanobiosensors has raised great hopes for early, sensitive, selective, and low-cost cancer diagnosis. Here, we reviewed the flagged recent research (2021-2023) developed as a series of biosensors equipped with nanomaterials and aptamer sequences (nanoaptasensors) to diagnose/prognosis of various types of cancers. Equipping these aptasensors with nanomaterials and using advanced biomolecular technologies have provided specified biosensing interfaces for more optimal and reliable detection of cancer biomarkers. The primary intention of this review was to present and categorize the latest innovations used in the design of these diagnostic tools, including the hottest surface modifications and assembly of sensing bioplatforms considering diagnostic mechanisms. The main classification is based on applying various nanomaterials and sub-classifications considered based on the type of analyte and other vital features. This review may help design subsequent electrochemical aptasensors. Likewise, the up-to-date status, remaining limitations, and possible paths for translating aptasensors to clinical cancer assay tools can be clarified.

Extracellular Vesicles, as Drug-Delivery Vehicles, Improve the Biological Activities of Astaxanthin

Astaxanthin (AST) exhibits potent antioxidant and anti-inflammatory activities but poor stability and biological efficacy, which limit its application in the food and medical industries. In the present study, a new strategy was proposed to enhance the biological activities of AST using fetal bovine serum-derived extracellular vesicles (EVs). Saponin-assisted incubation was used to load AST owing to its high encapsulation efficiency and loading capacity. AST-incorporated EVs (EV-ASTs) maintained their original EV morphology and showed high stability at 4 °C, 25 °C, and 37 °C over a 28-day period, which was attributed to the protective environment provided by the phospholipid bilayer membrane of the EVs. Additionally, the EV-ASTs exhibited excellent antioxidant and anti-inflammatory activities in HaCaT keratinocytes and RAW 264.7 macrophage cells, respectively; these were significantly higher than those of free AST. Furthermore, the mechanism associated with the enhanced biological activities of EV-ASTs was evaluated by analyzing the expression of genes involved in antioxidation and anti-inflammation, in parallel with cellular in vitro assays. These results provide insights into methods for improving the performance of hydrophobic drugs using nature-derived EVs and will contribute to the development of novel drug-delivery systems.

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.

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.

Practical tips and new trends in electrochemical biosensing of cancer-related extracellular vesicles

To tackle cancer and provide prompt diagnoses and prognoses, the constantly evolving biosensing field is continuously on the lookout for novel markers that can be non-invasively analysed. Extracellular vesicles (EVs) may represent a promising biomarker that also works as a source of biomarkers. The augmented cellular activity of cancerous cells leads to the production of higher numbers of EVs, which can give direct information on the disease due to the presence of general and cancer-specific surface-tethered molecules. Moreover, the intravesicular space is enriched with other molecules that can considerably help in the early detection of neoplasia. Even though EV-targeted research has indubitably received broad attention lately, there still is a wide lack of practical and effective quantitative procedures due to difficulties in pre-analytical and analytical phases. This review aims at providing an exhaustive outline of the recent progress in EV detection using electrochemical and photoelectrochemical biosensors, with a focus on handling approaches and trends in the selection of bioreceptors and molecular targets related to EVs that might guide researchers that are approaching such an unstandardised field.

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.

Tri-Channel Electrochemical Immunobiosensor for Combined Detections of Multiple Exosome Biomarkers of Lung Cancer

Current methods for the early diagnosis of cancer can be invasive and costly. In recent years, exosomes have been recognized as potential biomarkers for cancer diagnostics. The common methods for quantitative detection of exosomes, such as nanoparticle tracking analysis (NTA) and flow cytometry, rely on large-scale instruments and complex operation, with results not specific for cancer. Herein, we present a tri-channel electrochemical immunobiosensor for enzyme-free and label-free detecting carcino-embryonic antigen (CEA), neuron-specific enolase (NSE), and cytokeratin 19 fragments (Cyfra21-1) from exosomes for specific early diagnosis of lung cancer. The electrochemical immunobiosensor showed good selectivity and stability. Under optimum experimental conditions, the linear ranges were from 10^-3 to 10 ng/mL for CEA, 10^-4 to 10² ng/mL for NSE, and 10^-3 to 10² ng/mL for Cyfra21-1, and a detection limit down to 10^-4 ng/mL was achieved. Furthermore, we performed exosome analysis in three kinds of lung cancer. The results showed a distinct expression level of exosomal markers in different types. These works provide insight into a promising alternative for the quantification of exosomal markers in specific diseases in the following clinical bioassays.

Cobalt based Bi-functional Metal Organic Framework mediated Fluorescent Bio-sensing System for Hypersensitive Detection of Ag+ Ions through Catalytic Hairpin Assembly

Silver is often used as a water disinfectant in healthcare institutions as well as in potable water purifiers. Even though there are no strict regulations regarding the amount of silver...