Microporous PdCuB nanotag-based electrochemical aptasensor with Au@CuCl(2) nanowires interface for ultrasensitive detection of PD-L1-positive exosomes in the serum of lung cancer patients

Detection of Cancer Biomarkers: Review of Methods and Applications Reported from Analytical Perspective

One in five deaths in developed countries is related to cancer. The cancer prevalence is likely to grow with aging population. The affordable and accurate early diagnostics of cancer based on detection of cancer biomarkers at low concentration during its early stages is one of the most efficient way to decrease mortality and human suffering from cancer. The data from 201 analytical papers are tabulated in 9 tables, illustrated in 8 figures and used for comparative analysis of methods applied for cancer biomarker detection, including polymerase chain reaction, Loop-mediated isothermal amplification (LAMP), mass spectrometry, enzyme-linked immunosorbent assay, electroanalytical methods, immunoassays, surface enhanced Raman scattering, Fourier Transform Infrared and others in terms of above-mentioned performance parameters. Median and/or average limit of detection (LOD) are calculated and compared between different analytical methods. We also described and compared LOD of the methods used for detection of three frequently detected cancer biomarkers: carcinoembryonic antigen, prostate-specific antigen and alpha-fetoprotein. Among those methods of detection, the reported electrochemical sensors often demonstrate relatively high sensitivity/low LOD while they often have a moderate instrumental cost and fast time to results. The review tabulates, compares and discusses analytical papers, which report LOD of cancer biomarkers and comprehensive quantitative comparison of various analytical methods is made. The discussion of those techniques applied for cancer biomarker detection included brief summary of pro and cons for each of those methods.

Aptamers as Diagnostic and Therapeutic Agents for Aging and Age-Related Diseases

In the 21st century, the demographic shift toward an aging population has posed a significant challenge, particularly with respect to age-related diseases, which constitute a major threat to human health. Accordingly, the detection, prevention, and treatment of aging and age-related diseases have become critical issues, and the introduction of novel molecular recognition elements, called aptamers, has been considered. Aptamers, a class of oligonucleotides, can bind to target molecules with high specificity. In addition, aptamers exhibit superior stability, biocompatibility, and applicability, rendering them promising tools for the diagnosis and treatment of human diseases. In this paper, we present a comprehensive overview of aptamers, systematic evolution of ligands by exponential enrichment (SELEX), biomarkers associated with aging, as well as aptamer-based diagnostic and therapeutic platforms. Finally, the limitations associated with predicting and preventing age-related conditions are discussed, along with potential solutions based on advanced technologies and theoretical approaches.

PdPtCu mesoporous nanocube-based electrochemical sandwich immunosensor for detection of HIV-p24

The construction of simple, stable, low-cost and reproducible enzyme-free electrochemical biosensors can effectively avoid the problem of signal attenuation caused by enzyme inactivation. Hererin, we prepared a novel nanoenzymes PdPtCu mesoporous nanocubes (MNCs) to construct a label-free sandwich electrochemical immunosensor for the highly sensitivity detection of HIV-p24. PdPtCu MNCs have excellent peroxidase activity against hydrogen peroxide (H2O2) due to their synergistic ternary composition, large surface area and ability to penetrate mesoporous channels. Moreover, highly conductive and biocompatible gold nanoparticles@graphene oxide (AuNPs@GO) was introduced as a substrate to modify a glassy carbon electrode (GCE). Owing to the excellent electrochemical performance of the PdPtCu MNCs and AuNPs@GO, the developed immunosensors exhibited a good linear response from 0.04 pg/mL to 100 ng/mL with a low detection limit of 20 fg/mL. In addition, the established method exhibited excellent practical performance in human serum. This novel strategy provides a promising platform for ultrasensitive detection of the HIV-p24 in the field of clinical diagnostics.

Colorimetric aptasensor coupled with a deep-learning-powered smartphone app for programmed death ligand-1 expressing extracellular vesicles

Lung cancer is a devastating public health threat and a leading cause of cancer-related deaths. Therefore, it is imperative to develop sophisticated techniques for the non-invasive detection of lung cancer. Extracellular vesicles expressing programmed death ligand-1 (PD-L1) markers (PD-L1@EVs) in the blood are reported to be indicative of lung cancer and response to immunotherapy. Our approach is the development of a colorimetric aptasensor by combining the rapid capturing efficiency of (Fe3O4)-SiO2-TiO2 for EV isolation with PD-L1 aptamer-triggered enzyme-linked hybridization chain reaction (HCR) for signal amplification. The numerous HRPs catalyze their substrate dopamine (colorless) into polydopamine (blackish brown). Change in chromaticity directly correlates with the concentration of PD-L1@EVs in the sample. The colorimetric aptasensor was able to detect PD-L1@EVs at concentrations as low as 3.6×102 EVs/mL with a wide linear range from 103 to 1010 EVs/mL with high specificity and successfully detected lung cancer patients' serum from healthy volunteers' serum. To transform the qualitative colorimetric approach into a quantitative operation, we developed an intelligent convolutional neural network (CNN)-powered quantitative analyzer for chromaticity in the form of a smartphone app named ExoP, thereby achieving the intelligent analysis of chromaticity with minimal user intervention or additional hardware attachments for the sensitive and specific quantification of PD-L1@EVs. This combined approach offers a simple, sensitive, and specific tool for lung cancer detection using PD-L1@EVs. The addition of a CNN-powered smartphone app further eliminates the need for specialized equipment, making the colorimetric aptasensor more accessible for low-resource settings.

Branched hybridization chain reaction and tetrahedral DNA-based trivalent aptamer powered SERS sensor for ultra-highly sensitive detection of cancer-derived exosomes

Exosomes have emerged as a promising noninvasive biomarker for early cancer diagnosis due to their ability to carry specific bioinformation related to cancer cells. However, accurate detection of trace amount of cancer-derived exosomes in complex blood remains a significant challenge. Herein, an ultra-highly sensitive SERS sensor, powered by the branched hybridization chain reaction (bHCR) and tetrahedral DNA-based trivalent aptamer (triApt-TDN), has been proposed for precise detection of cancer-derived exosomes. Taking gastric cancer SGC-7901 cells-derived exosomes as a test model, the triApt-TDNs were constructed by conjugating aptamers specific to mucin 1 (MUC1) protein with tetrahedral DNAs and subsequently immobilized on the surface of silver nanorods (AgNRs) arrays to create SERS-active sensing chips capable of specifically capturing exosomes overexpressing MUC1 proteins. The bHCR was further initiated by the trigger aptamers (tgApts) bound to exosomes, and as a result the SERS tags were assembled into AuNP network structures with abundant SERS hotspots. By optimizing the sensing conditions, the SERS sensor showed good performance in ultra-highly sensitive detection of target exosomes within 60 min detection time, with a broad response ranging of 1.44 to 1.44 × 104 particles·μL-1 and an ultralow limit of detection capable of detecting a single exosome in 2 μL sample. Furthermore, the SERS sensor exhibited good uniformity, repeatability and specificity, and capability to distinguish between gastric cancer (GC) patients and healthy controls (HC) through the detection of exosomes in clinical human serums, indicating its promising clinical potential for early diagnosis of gastric cancer.

Electrochemical Biosensors for Cancer Diagnosis: Multitarget Analysis to Present Molecular Characteristics of Tumor Heterogeneity

Electrochemical biosensors are gaining attention as powerful tools in cancer diagnosis, particularly in liquid biopsy, due to their high efficiency, rapid response, exceptional sensitivity, and specificity. However, the complexity of intra- and intertumor heterogeneity, with variations in genetic and protein expression profiles and epigenetic modifications, makes electrochemical biosensors susceptible to false-positive or false-negative diagnostic outcomes. To address this challenge, there is growing interest in simultaneously analyzing multiple biomarkers to reveal molecular characteristics of tumor heterogeneity for precise cancer diagnosis. In this Perspective, we highlight recent advancements in utilizing electrochemical biosensors for cancer diagnosis, with a specific emphasis on the multitarget analysis of cancer biomarkers including tumor-associated nucleic acids, tumor protein markers, extracellular vesicles, and tumor cells. These biosensors hold significant promise for improving precision in early cancer diagnosis and monitoring, as well as potentially offering new insights into personalized cancer management.

New strategies for lung cancer diagnosis and treatment: applications and advances in nanotechnology

Lung cancer leads in causing cancer-related mortality worldwide, continually posing a significant threat to human health. Current imaging diagnostic techniques, while offering non-invasive detection, suffer from issues such as insufficient sensitivity and the risks associated with radiation exposure. Pathological diagnosis, the gold standard for confirmation, also faces challenges like invasiveness and high costs. In treatment, surgery, radiotherapy, and chemotherapy are the main modalities, each encountering challenges related to precision, environmental adaptability, and side effects. Nanotechnology's advancement provides new solutions for the diagnosis and treatment of lung cancer, promising to enhance diagnostic accuracy and reduce side effects during treatment. This article introduces the main types of nanomaterials used in the field of lung cancer, offering a comprehensive overview of current research on the application of nanotechnology in early screening, diagnosis, treatment, and monitoring of lung cancer, and summarizing ongoing clinical research findings.

Influencing immunity: role of extracellular vesicles in tumor immune checkpoint dynamics

Immune checkpoint proteins (ICPs) serve as critical regulators of the immune system, ensuring protection against damage due to overly activated immune responses. However, within the tumor environment, excessive ICP activation weakens antitumor immunity. Despite the development of numerous immune checkpoint blockade (ICB) drugs in recent years, their broad application has been inhibited by uncertainties about their clinical efficacy. A thorough understanding of ICP regulation in the tumor microenvironment is essential for advancing the development of more effective and safer ICB therapies. Extracellular vesicles (EVs), which are pivotal mediators of cell-cell communication, have been extensively studied and found to play key roles in the functionality of ICPs. Nonetheless, a comprehensive review summarizing the current knowledge about the crosstalk between EVs and ICPs in the tumor environment is lacking. In this review, we summarize the interactions between EVs and several widely studied ICPs as well as their potential clinical implications, providing a theoretical basis for further investigation of EV-related ICB therapeutic approaches.

The new advance of exosome-based liquid biopsy for cancer diagnosis

Liquid biopsy is a minimally invasive method that uses biofluid samples instead of tissue samples for cancer diagnosis. Exosomes are small extracellular vesicles secreted by donor cells and act as mediators of intercellular communication in human health and disease. Due to their important roles, exosomes have been considered as promising biomarkers for liquid biopsy. However, traditional methods for exosome isolation and cargo detection methods are time-consuming and inefficient, limiting their practical application. In the past decades, many new strategies, such as microfluidic chips, nanowire arrays and electrochemical biosensors, have been proposed to achieve rapid, accurate and high-throughput detection and analysis of exosomes. In this review, we discussed about the new advance in exosome-based liquid biopsy technology, including isolation, enrichment, cargo detection and analysis approaches. The comparison of currently available methods is also included. Finally, we summarized the advantages and limitations of the present strategies and further gave a perspective to their future translational use.

Recent advances to address challenges in extracellular vesicle-based applications for lung cancer

Lung cancer, highly prevalent and the leading cause of cancer-related death globally, persists as a significant challenge due to the lack of definitive tumor markers for early diagnosis and personalized therapeutic interventions. Recently, extracellular vesicles (EVs), functioning as natural carriers for intercellular communication, have received increasing attention due to their ability to traverse biological barriers and deliver diverse biological cargoes, including cytosolic proteins, cell surface proteins, microRNA, lncRNA, circRNA, DNA, and lipids. EVs are increasingly recognized as a valuable resource for non-invasive liquid biopsy, as well as drug delivery platforms, and anticancer vaccines for precision medicine in lung cancer. Herein, given the diagnostic and therapeutic potential of tumor-associated EVs for lung cancer, we discuss this topic from a translational standpoint. We delve into the specific roles that EVs play in lung cancer carcinogenesis and offer a particular perspective on how advanced engineering technologies can overcome the current challenges and expedite and/or enhance the translation of EVs from laboratory research to clinical settings.

Composition, functions, and applications of exosomal membrane proteins

Exosomes play a crucial role in various biological processes, such as human development, immune responses, and disease occurrence. The membrane proteins on exosomes are pivotal factors for their biological functionality. Currently, numerous membrane proteins have been identified on exosome membranes, participating in intercellular communication, mediating target cell recognition, and regulating immune processes. Furthermore, membrane proteins from exosomes derived from cancer cells can serve as relevant biomarkers for early cancer diagnosis. This article provides a comprehensive review of the composition of exosome membrane proteins and their diverse functions in the organism's biological processes. Through in-depth exploration of exosome membrane proteins, it is expected to offer essential foundations for the future development of novel biomedical diagnostics and therapies.

Development of a microcantilever-based biosensor for detecting Programmed Death Ligand 1

The ongoing global concern of cancer worldwide necessitates the development of advanced diagnostic and therapeutic strategies. The majority of recent detection strategies involve the employment of biomarkers. A critical biomarker for cancer immunotherapy efficacy and patient prognosis is Programmed Death Ligand 1 (PD-L1), which is a key immune checkpoint protein. PD-L1 can be particularly linked to cancer progression and therapy response. Current detection methods, such as enzyme-linked immunosorbent assay (ELISA), face limitations like high cost, time consumption, and complexity. This study introduces a microcantilever-based biosensor designed for the detection of soluble PD-L1 (sPD-L1), which has a specific association with PD-L1. The biosensor utilizes anti-PD-L1 as the sensing layer, capitalizing on the specific binding affinity between anti-PD-L1 and sPD-L1. The presence of the sensing layer was confirmed through Atomic Force Microscopy (AFM) and contact angle measurements. Binding between sPD-L1 and anti-PD-L1 induces a shift in the microcantilever's resonance frequency, which is proportional to the PD-L1 concentration. Notably, the resonance frequency shift demonstrates a robust linear relationship with the increasing biomarker concentration, ranging from 0.05 ng/ml to 500 ng/ml. The detection limit of the biosensor was determined to be approximately 10 pg/ml. The biosensor demonstrates excellent performance in detecting PD-L1 with high specificity even in complex biological matrices. This innovative approach not only provides a promising tool for early cancer diagnosis but also holds potential for monitoring immunotherapy efficacy, paving the way for personalized and effective cancer treatments.

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.

Leveraging electrochemical sensors to improve efficiency of cancer detection

Electrochemical biosensors have emerged as a promising technology for cancer detection due to their high sensitivity, rapid response, low cost, and capability for non-invasive detection. Recent advances in nanomaterials like nanoparticles, graphene, and nanowires have enhanced sensor performance to allow for cancer biomarker detection, like circulating tumor cells, nucleic acids, proteins and metabolites, at ultra-low concentrations. However, several challenges need to be addressed before electrochemical biosensors can be clinically implemented. These include improving sensor selectivity in complex biological media, device miniaturization for implantable applications, integration with data analytics, handling biomarker variability, and navigating regulatory approval. This editorial critically examines the prospects of electrochemical biosensors for efficient, low-cost and minimally invasive cancer screening. We discuss recent developments in nanotechnology, microfabrication, electronics integration, multiplexing, and machine learning that can help realize the potential of these sensors. However, significant interdisciplinary efforts among researchers, clinicians, regulators and the healthcare industry are still needed to tackle limitations in selectivity, size constraints, data interpretation, biomarker validation, toxicity and commercial translation. With committed resources and pragmatic strategies, electrochemical biosensors could enable routine early cancer detection and dramatically reduce the global cancer burden.

Ratiometric electrochemical immunosensor for simultaneous detection of C-myc and Bcl-2 based on multi-role alloy composites

A ratiometric electrochemical immunosensor is proposed for simultaneous detection of cellular-myelocytomatosis oncoprotein (C-myc) and B-cell lymphoma 2 (Bcl-2) via the potential-resolved strategy. It relied on multi-role co-loaded alloy composites (CLACs) and poly(3,4-ethylenedioxythiophene) (PEDOT)-graphene oxide (GO)-multiwalled carbon nanotubes (MWCNTs) (PGM) modified electrodes. CLACs with good catalytic and enzyme-like properties were synthesized in one step by loading tetramethylbenzidine (TMB) or methylene blue (MB) into Pt-Pd alloy and used as label materials. After immunological reactions, CLACs showed distinguishable dual differential pulse voltammetry signals at  - 0.26 V and 0.38 V, corresponding to C-myc and Bcl-2, and the PGM had an electrochemical signal at 1.2 V, which could be used as a reference signal to construct a ratiometric sensor. CLACs had a satisfactory synergistic effect with the PGM, and eventually achieved quadruple signal amplification. Thus, benefiting from multiple magnification and ratiometric self-calibration functions, sensitive detections of C-myc and Bcl-2 were achieved, with detection limits as low as 0.5 and 2.5 pg mL-1, respectively. Additionally, when the designed method was applied to blood samples from lymphoma patients, results consistent with the ELISA kit were obtained. This will open avenues for constructing multiple protein detection sensors.

Enzyme-catalyzed electrochemical aptasensor for ultrasensitive detection of soluble PD-L1 in breast cancer based on decorated covalent organic frameworks and carbon nanotubes

BACKGROUND

Soluble programmed death-ligand 1 (sPD-L1) is critically involved in breast cancer recurrence and metastasis. However, the clinical application of highly sensitive sPD-L1 assays remains a challenge due to its low abundance in peripheral blood. To address this issue, for the first time, an enzyme-catalyzed electrochemical aptasensing platform was devised, incorporating covalent organic frameworks-gold nanoparticles-antibody-horseradish peroxidase (COFs-AuNPs-Ab-HRP) and polyethyleneimine-functionalized multiwalled carbon nanotubes (MWCNTs-PEI-AuNPs) for the highly specific and ultrasensitive detection of sPD-L1.

RESULTS

MWCNTs-PEI-AuNPs possessed an extensive specific surface area and exhibited excellent electrical conductivity, facilitating the immobilization of aptamer and amplifying the signal. COFs modified with AuNPs not only amplified the electrical signal but also proffered a loading platform for the Ab and HRP. The favorable biocompatibility of COFs contributed to the preservation of enzyme activity and stability. HRP acted in synergy with hydrogen peroxide (H2O2) to catalyze the oxidation of hydroquinone (HQ) to benzoquinone (BQ). Subsequently, BQ underwent electrochemical reduction to HQ, inducing an enzymatic redox cycle that amplified the electrochemical signal and enhanced the sensitivity and selectivity of the detection method. The developed aptasensor displayed a liner range for sPD-L1 identification from 1 pg mL-1 to 100 ng mL-1 and the detection limit reached 0.143 pg mL-1 (S/N = 3).

SIGNIFICANCE

Paving the way for clinical application, this strategy detected differences in sPD-L1 in cell supernatants and peripheral blood of breast cancer patients with higher sensitivity compared to commercial sPD-L1 ELISA kit. This work demonstrates significant potential in offering reference information for early diagnosis and disease surveillance of breast cancer.

Ti3C2Tx MXene -facilitated non-selective trapping effect: Efficient SERS detection of exosomal PD-L1

Biosensors developed through a sandwich approach have demonstrated favorable detection performance for exosomal programmed cell death 1 ligand 1 (ExoPD-L1) detection. However, the reported PD-L1 antibodies, peptides, and aptamers utilized in these biosensors typically bind to the extracellular region, with overlapping binding sites that severely constrain the fabrication of biosensors. In this study, we present a simple approach to specifically identify and analyze ExoPD-L1 through the non-selective trapping effect of Ti3C2TX (X=-O, -F, -OH) MXene on exosomes via the formation of Ti-O-P complexation, and the selective capture of peptide-functionalized Au@MPBA (4-Mercaptophenylboronic acid) @SiO2 surface enhanced Raman scattering (SERS) tags on ExoPD-L1. The biosensor delivered a both hypersensitive and reliable performance in exosome detection with a low limit of detection (20.74 particles/mL) in the linear range of 102 to 5×106 particles/mL. Furthermore, the biosensor demonstrated excellent stability and interference resistance in detecting ExoPD-L1 in clinical serum samples, enabling the easy differentiation of breast cancer patients from healthy controls. This work provides new insights into the design of biosensors for exosome detection and can serve as a replicable template for sandwich immunoassay detection for other types of sensors, including but not limited to SERS.