Assembly of Black Phosphorus Nanosheets and MOF to Form Functional Hybrid Thin-Film for Precise Protein Capture, Dual-Signal and Intrinsic Self-Calibration Sensing of Specific Cancer-Derived Exosomes

Rapid, flexible fabrication of a microfluidic electrochemical chip nucleic acid target for selective, label-free detection of influenza virus DNA using catalytic redox-recycling

H5N1 flu is a highly virulent and variable subtype of influenza with significant epidemic and pandemic potential. In this study, we introduce a novel, maskless, and rapid manufacturing process for a microfluidic chip integrated with electrodes for the quantitative detection of H5N1-DNA sequences. This detection leverages a catalytic redox-recycling signal via a novel Fe₃O₄@TMU-8 nanocomposite, which facilitates the turnover of the oxidation state of [Ru(NH₃)₆]³⁺, thereby amplifying the electrochemical signal output. The positively charged [Ru(NH₃)₆]³⁺ molecule associates with the phosphate backbone of the nucleic acids in H5N1-DNA. Changes in the aptasensor's redox-recycling signal, due to the hybridization of DNA sequences with [Ru(NH₃)₆]³⁺, were used as the electrochemical sensing response. Under optimal conditions, the signal exhibited a linear relationship with H5N1-DNA concentration, ranging from 1 fM to 1 nM, with a detection limit of 0.16 fM. This report details the fabrication of the microfluidic device using Poly(methyl methacrylate) (PMMA) sheet substrates. A laser system was employed to generate microfluidic patterns directly on the PMMA sheet. This biosensing device demonstrated long-term stability and good reproducibility, making it suitable for the quantitative assay of H5N1-DNA sequences. The results from food sample analyses further confirmed the applicability and effectiveness of the resulting biosensor.

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

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

Metal-Organic Frameworks (MOFs): Classification, Synthesis, Modification, and Biomedical Applications

Metal-organic frameworks (MOFs) are a new variety of solid crystalline porous functional materials. As an extension of inorganic porous materials, it has made important progress in preparation and application. MOFs are widely used in various fields such as gas adsorption storage, drug delivery, sensing, and biological imaging due to their high specific surface area, porosity, adjustable pore size, abundant active sites, and functional modification by introducing groups. In this paper, the types of MOFs are classified, and the synthesis methods and functional modification mechanisms of MOFs materials are summarized. Finally, the application prospects and challenges of metal-organic framework materials in the biomedical field are discussed, hoping to promote their application in multidisciplinary fields.

Zwitterionic polymers grafting of metal organic framework encapsulated boronic acid carbon dots as antibiofouling fluorescent probe for baicalin monitoring

The sensitivity and accuracy of fluorescence probes for biological samples are affected by not only interfering molecule compounds but also the nonspecific adsorption of proteins and other macromolecules. Herein, fluorescence probe based on zwitterionic sulfobetaine methacrylate polymer (PSBMA) as an antibiofouling layer and amino boric acid carbon dots encapsulated in the metal-organic framework UiO-66-NH2 (UiO-66-NH2/BN-CDs) as a target recognition site was designed for the detection of baicalin (BAI). Owing to the introduction of BN-CDs into UiO-66-NH2 with high specific surface area, the prepared UiO-66-NH2/BN-CDs@PSBMA probe exhibited a high adsorption capacity of 78.9 mg g-1, while presented fluorescence enhancing and superior fluorescence selectivity to BAI at excitation and emission wavelengths of 400 and 425 nm, respectively. Connecting PSBMA with good hydrophilicity to UiO-66-NH2, resulted in an anti-protein capacity of over 96.3 %, effectively inhibiting protein interference with the fluorescence signal. By virtue of its good antibiofouling and recognizing capacities, the fluorescence probe exhibited a satisfactory detection range of 10-80 nmol L-1, with a fairly low detection limit of 0.0064 μmol L-1. Using the method to detect BAI in Goji berry, Sophora and Yinhuang oral solution, demonstrating its potential for the accurate and quantitative detection of BAI in complex biological samples.

Dual-Modal Aptasensor for Sensitive Detection of Non-Small Cell Lung Cancer Exosomes Utilizing Two-Dimensional Nanopaper Co@g-C3N4@PB

Nonsmall cell lung cancer (NSCLC), due to its lack of early symptoms, has become one of the leading causes of cancer-related deaths globally. Exosomes, small membrane vesicles secreted by cells, are widely present in human bodily fluids. In the bodily fluids of NSCLC patients, the quantity of extracellular vesicles is double that of healthy individuals, suggesting their potential as biomarkers for screening NSCLC. This study designed a dual-modal aptasensor that integrated excellent sensitivity in electrochemical detection and portability in fluorescence detection into one device. AuNPs were functionalized with exosome-capturing probes containing thiol-modified CD63 aptamers, which were immobilized on screen-printed gold electrodes. On the other hand, the carboxylated CD63 aptamer was immobilized on the surface of PB-modified g-C3N4 loaded with Co-SANs particles (Co@g-C3N4@PB). By combining these components, a sandwich structure (AuNPs/Apt1/Exo/Apt2- Co@g-C3N4@PB) was constructed, forming a probe for specific exosome recognition. First, the samples were preliminarily assessed for their positive or negative status under a fluorescence inverted microscope. Subsequently, a more in-depth quantitative analysis was conducted on suspected positive samples using electrochemical or fluorescence analysis methods. The detection limits for electrochemical analysis and fluorescence analysis were 66.68 and 33.5particles/mL, respectively. In the analysis of clinical serum exosome samples, the developed dual-modal aptasensor effectively distinguished serum specimens from those of NSCLC patients and healthy volunteers. This highlighted the inspection capability of the dual-modal adapter sensor, especially in point-of-care testing, making it a highly suitable tool for clinical applications.

Homogeneous electrochemical ratiometric biosensor for MircoRNA detection based on UiO-66-NH2 signal probe and waste-free entropy-driven DNA machine

The construction of efficient methods for highly sensitive and rapid detection of disease markers is essential for the early diagnosis of serious diseases. In this paper, taking advantage of the UiO-66-NH2 signal molecule in combination with a waste-free entropy-driven DNA machine, a novel homogeneous electrochemical ratiometric platform is developed to detect MircoRNA (miRNA). Metal-organic framework materials (UiO-66-NH2 MOF) and ferrocene were utilized as electrochemical signal tags and reference probes, respectively. The target-initiated waste-free three-dimensional (3D) entropy-driven DNA nanomachine is activated in the presence of miRNA, resulting in DNA-labeled-UiO-66-NH2 falling off from the electrode, leading to a decrease in the signal of UiO-66-NH2 at 0.83V. Our strategy can mitigate false positive responses induced by the DNA probes immobilized on electrodes in traditional distance-dependent signal adjustment ratiometric strategies. The proposed ratiometric platform demonstrates superior sensitivity (a detection limit of 9.8 fM), simplified operation, high selectivity, and high repeatability. The ratiometric biosensor is also applied to detect miRNA content in spiked serum samples.

Magnetic metal-organic frameworks as sensitive aptasensors for coronavirus spike protein

Electrochemical biosensors, known for their low cost, sensitivity, selectivity, and miniaturization capabilities, are ideal for point-of-care devices. The magnetic metal-organic framework (MMOF), synthesized using the in-situ growth method, consists of ferric salt, magnetic nanoparticles, histidine, and benzene tetracarboxylic acid. MMOF was sequentially modified with aptamer-biotin and streptavidin-horseradish peroxidase, serving as a detector for spike protein and a transducer converting electrochemical signals using H2O2-hydroquinone on a screen-printed electrode. MMOF facilitates easy washing and homogeneous deposition on the working electrode with a magnet, enhancing sensitivity and reducing noise. The physical and electrochemical properties of the modified MMOFs were thoroughly characterized using various analytical techniques. The aptasensors' performance achieved a detection limit of 6 pM for voltammetry and 5.12 pM for impedance spectroscopy in human serum samples. This cost-effective, portable MMOF platform is suitable for rapid point-of-care testing for SARS-CoV-2 spike proteins.

Portable self-powered electrochemical aptasensing platform for ratiometric detection of mycotoxins based on multichannel photofuel cell

Self-powered electrochemical sensors based on photofuel cells have attracted considerable research interest because their unique advantage of not requiring an external electric source, but their application in portable and multiplexed targets assay is limited by the inherent mechanism. In this work, a portable self-powered sensor constructed with multichannel photofuel cells was developed for the ratiometric detection of mycotoxins, namely ochratoxin A (OTA) and patulin (PAT). The spatially resolved CdS/Bi2S3-modified photoanodes and a shared Prussian Blue cathode were integrated on an etched indium-tin oxide slide to fabricate the multichannel photofuel cell. The aptamers of OTA and PAT were covalently bonded to individual photoanode regions to build sensitive interfaces, and the specific recognition of analytes impaired the output performance of constructed PFC. Accordingly, ratiometric sensing of OTA and PAT was achieved by utilizing the output performance of a control PFC as a reference signal. This approach effectively eliminates the impact of light intensity on the accuracy of the detection. Under the optimal conditions, the proposed sensing chip exhibited linear ranges of 2.0-1000 nM and 5.0-500 nM for OTA and PAT, respectively. The detection limits (3 S/N) were determined to be 0.25 nM for OTA and 0.27 nM for PAT. The developed ratiometric sensing method demonstrated good selectivity and stability in the simultaneous detection of OTA and PAT. It was successfully utilized for the analysis of OTA and PAT real samples. This work provides a new perspective for construction of portable and ratiometric self-powered sensing platform.

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.

Label-Free, Sensitive, and Versatile Colorimetric Method for Molecule Detection via the G-Quadruplex-Based Signal Quenching Strategy

Signal amplification strategies have emerged as a prominent tool in the field of improving the detection sensitivity of small extracellular vesicles (sEVs). It is important to highlight that the utilization of signal quenching strategies is not commonly implemented. A detection technique for sEVs was established based on the unwinding of G-quadruplex using Klenow fragment polymerase (KF), which served as an inspiration for this study. This system is characterized by its simplicity and lack of labeling, making it an efficient approach for signal quenching. In the presence of sEVs, the CD63 aptamer in the capture@sMBs complex binds with the CD63 protein on the surface of sEVs to release trigger sequences, which were employed as a primer to mediate the DNA polymerase/endonuclease-assisted signal recycling. The signal recycling process produces numerous single-stranded DNA sequences that can bind to the toehold section of the G-quadruplex. This leads to the rupture of the G-quadruplex structure and the subsequent deactivation of a DNAzyme generated by the G-quadruplex structure and hemin, thereby inhibiting its biological catalytic function. Consequently, the G-quadruplex structure would undergo a transformation to a duplex structure, leading to the emergence of a discernible differential signal that can be noticed in a majority of instances, even without the aid of magnification devices. The decrease in the prominent signal allows for the efficient analysis of target sEVs, which exhibit a notably low detection limit. In addition to the detection of sEVs, the approach has also been utilized for the investigation of miRNA-21. The approach demonstrates a high level of selectivity and robustness in its capacity to differentiate between target miRNA and base-mismatched miRNA as well as other miRNA families. This statement suggests that the assay holds significant promise for use in biochemical research and clinical diagnosis.

Polydopamine-assisted aptamer-carrying tetrahedral DNA microelectrode sensor for ultrasensitive electrochemical detection of exosomes

BACKGROUND

Exosomes are nanoscale extracellular vesicles (30-160 nm) with endosome origin secreted by almost all types of cells, which are considered to be messengers of intercellular communication. Cancerous exosomes serve as a rich source of biomarkers for monitoring changes in cancer-related physiological status, because they carry a large number of biological macromolecules derived from parental tumors. The ultrasensitive quantification of trace amounts of cancerous exosomes is highly valuable for non-invasive early cancer diagnosis, yet it remains challenging. Herein, we developed an aptamer-carrying tetrahedral DNA (Apt-TDNA) microelectrode sensor, assisted by a polydopamine (PDA) coating with semiconducting properties, for the ultrasensitive electrochemical detection of cancer-derived exosomes.

RESULTS

The stable rigid structure and orientation of Apt-TDNA ensured efficient capture of suspended exosomes. Without PDA coating signal amplification strategy, the sensor has a linear working range of 102-107 particles mL-1, with LOD of ~ 69 exosomes and ~ 42 exosomes for EIS and DPV, respectively. With PDA coating, the electrochemical signal of the microelectrode is further amplified, achieving single particle level sensitivity (~ 14 exosomes by EIS and ~ 6 exosomes by DPV).

CONCLUSIONS

The proposed PDA-assisted Apt-TDNA microelectrode sensor, which integrates efficient exosome capture, sensitive electrochemical signal feedback with PDA coating signal amplification, provides a new avenue for the development of simple and sensitive electrochemical sensing techniques in non-invasive cancer diagnosis and monitoring treatment response.

Aptamer-functionalized MOFs and AI-driven strategies for early cancer diagnosis and therapeutics

Metal-Organic Frameworks (MOFs) have exceptional inherent properties that make them highly suitable for diverse applications, such as catalysis, storage, optics, chemo sensing, and biomedical science and technology. Over the past decades, researchers have utilized various techniques, including solvothermal, hydrothermal, mechanochemical, electrochemical, and ultrasonic, to synthesize MOFs with tailored properties. Post-synthetic modification of linkers, nodal components, and crystallite domain size and morphology can functionalize MOFs to improve their aptamer applications. Advancements in AI and machine learning led to the development of nonporous MOFs and nanoscale MOFs for medical purposes. MOFs have exhibited promise in cancer therapy, with the successful accumulation of a photosensitizer in cancer cells representing a significant breakthrough. This perspective is focused on MOFs' use as advanced materials and systems for cancer therapy, exploring the challenging aspects and promising features of MOF-based cancer diagnosis and treatment. The paper concludes by emphasizing the potential of MOFs as a transformative technology for cancer treatment and diagnosis.

Nano-Brush Structure for Rapid Label-Free Differentiation of Alzheimer's Disease Stages and Direct Capture of Neuron-Derived Exosomes from Human Blood Plasma

The measurement of the neurofilament light chain (NFL) in human blood plasma/serum is a promising liquid biopsy for Alzheimer's disease (AD) diagnosis, offering advantages over conventional neuroimaging techniques recommended in clinical guidelines. Here, a controllable nano-brush structure comprising upstanding silicon nanowires coated with indium tin oxide was employed as the sensing substrate. This nano-brush structure was modified with an NFL antibody (NFLAb) via silane coupling and then further connected as the extended gate in a field-effect transistor (EGFET). Notable signal differences emerged within a 2 min timeframe, enabling the label-free differentiation in human blood plasmas among four distinct cohorts: healthy controls, subjective cognitive decline, mild cognitive impairment, and dementia due to AD. Our study indicates that achieving a surface roughness exceeding 400 nm on the modified nano-brush structure enables the effective electrical sensing in our EGFETs. These distinct electrical responses measured via the NFLAb-modified nano-brush EGFETs can be attributed to the combined effects of the captured NFLs and NFL-specific neuron-derived exosomes (NDEs) found in dementia patients, as confirmed by electron spectroscopy for chemical analysis, atomic force microscopy, and scanning electron microscopy. Finally, the potential of quantitatively detecting NDEs on the NFLAb-modified nano-brush structure was demonstrated using spiked solutions containing NFL-specific NDEs from IMR-32 neuroblast cells, wherein concentration-dependent changes were observed in the EGFETs output signal. Our findings show that the NFLAb-modified nano-brush EGFET enables rapid, label-free differentiation between healthy individuals and patients at varying stages of AD.

Current status and prospect of ZIF-based materials for breast cancer treatment

Breast cancer, one of the three most life-threatening cancers in modern times, must be explored for treatments with low side effects and practical efficacy. Metal organic framework materials (MOFs) is made by metal ions as the center for point and organic ligands as a bridge connecting a new type of porous nano-materials, among them, the zinc base zeolite imidazole skeleton material series (ZIFs) because of its excellent biocompatibility and pH slow controlled release ability, is widely used in the tumor microenvironment in basic research and achieved remarkable curative effect. Inspired by this, in this review, we focus on the recent research progress on the application of ZIFs in the treatment of breast cancer, mainly studying the structure of ZIFs such as ZIF-8, ZIF-90 and ZIF-67 and their application in novel therapies for breast cancer treatment, such as targeted drug delivery, photothermal therapy, immunotherapy and gene therapy.We will more fully demonstrate the potential of zif in breast cancer treatment, hoping to provide an avenue for exploring breast cancer treatment.

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.

Ultrasensitive Electrochemical Aptasensing of Malathion Based on Hydroxylated Black Phosphorus/Poly-L-Lysine Composite

A highly sensitive unlabeled electrochemical aptasensor based on hydroxylated black phosphorus/poly-L-lysine (hBP/PLL) composite is introduced herein for the detection of malathion. Poly-L-lysine (PLL) with adhesion and coating properties adhere to the surface of the nanosheets by noncovalent interactions with underlying hydroxylated black phosphorus nanosheets (hBP) to produce the hBP/PLL composite. The as-synthesized hBP/PLL composite bonded to Au nanoparticles (Au NPs) firmly by assembling and using them as a substrate for the aptamer with high specificity as a probe to fabricate the sensor. Under optimal conditions, the linear range of the electrochemical aptasensor was 0.1 pM~1 μM, and the detection limit was 2.805 fM. The electrochemical aptasensor has great selectivity, a low detection limit, and anti-interference, which has potential application prospects in the field of rapid trace detection of pesticide residues.

DNA-directed assembly of nanomaterials and their biomedical applications

In the past decades, DNA has been widely used in the field of nanostructures due to its unique programmable properties. Besides being used to form its own diverse structures such as the assembly of DNA origami, DNA can also be used for the assembly of nanostructures with other materials. In this review, different strategies for the functionalization of DNA on nanoparticle surfaces are listed, and the roles of DNA in the assembly of nanostructures as well as the influencing factors are discussed. Finally, the biomedical applications of DNA-assembled nanostructures were summarized. This review provided new insight into the application of DNA in nanostructure assembly.

Enzyme‐Encapsulated Protein Trap Engineered Metal–Organic Framework‐Derived Biomineral Probes for Non‐Invasive Prostate Cancer Surveillance

A paper‐based naked‐eye recognition assay with enzyme‐encapsulated protein engineered metal–organic framework‐derived biominerals is developed for direct quantification of sarcosine in urine samples for screening of prostate cancer individuals. The detection strategy stems from the successful construction of a cascade response model, which involves the introduction of a cascade enzymatic catalytic reaction on Pt nanoparticles (NPs)‐loaded porous CeO2 by integrating a sarcosine oxidase as a special recognition unit and a chromogenic substrate as a signal molecule reporter. Pt NPs‐loaded CeO2 is subjected to a one‐step thermal treatment based on multilayered mesoporous Ce‐based metal–organic framework, and the calcined CeO2 exhibits the same distinct porous graded structure. Importantly, introduction of Pt NPs sharply enhances the peroxidase‐like activity of CeO2, which is considered to be caused by the difference in the adsorption behavior of hydrogen peroxide on the CeO2 surface and Pt/CeO2 obtained by density functional theory calculations. On the basis of this, the probe is used on a mass‐producible paper‐based working platform and 3D‐printed device to specifically screen for minor differences in sarcosine between urine samples from cancer patients and normal individuals. Enzyme‐assisted cascade catalytic reaction can be extended by replacing different recognition units for multiple analytes.

Electrochemical aptasensor based on the engineered core-shell MOF nanostructures for the detection of tumor antigens

It is essential to develop ultrasensitive biosensors for cancer detection and treatment monitoring. In the development of sensing platforms, metal-organic frameworks (MOFs) have received considerable attention as potential porous crystalline nanostructures. Core-shell MOF nanoparticles (NPs) have shown different diversities, complexities, and biological functionalities, as well as significant electrochemical (EC) properties and potential bio-affinity to aptamers. As a result, the developed core-shell MOF-based aptasensors serve as highly sensitive platforms for sensing cancer biomarkers with an extremely low limit of detection (LOD). This paper aimed to provide an overview of different strategies for improving selectivity, sensitivity, and signal strength of MOF nanostructures. Then, aptamers and aptamers-modified core-shell MOFs were reviewed to address their functionalization and application in biosensing platforms. Additionally, the application of core-shell MOF-assisted EC aptasensors for detection of several tumor antigens such as prostate-specific antigen (PSA), carbohydrate antigen 15-3 (CA15-3), carcinoembryonic antigen (CEA), human epidermal growth factor receptor-2 (HER2), cancer antigen 125 (CA-125), cytokeratin 19 fragment (CYFRA21-1), and other tumor markers were discussed. In conclusion, the present article reviews the advancement of potential biosensing platforms toward the detection of specific cancer biomarkers through the development of core-shell MOFs-based EC aptasensors.

BioMOF-Based Anti-Cancer Drug Delivery Systems

A variety of nanomaterials have been developed specifically for biomedical applications, such as drug delivery in cancer treatment. These materials involve both synthetic and natural nanoparticles and nanofibers of varying dimensions. The efficacy of a drug delivery system (DDS) depends on its biocompatibility, intrinsic high surface area, high interconnected porosity, and chemical functionality. Recent advances in metal-organic framework (MOF) nanostructures have led to the achievement of these desirable features. MOFs consist of metal ions and organic linkers that are assembled in different geometries and can be produced in 0, 1, 2, or 3 dimensions. The defining features of MOFs are their outstanding surface area, interconnected porosity, and variable chemical functionality, which enable an endless range of modalities for loading drugs into their hierarchical structures. MOFs, coupled with biocompatibility requisites, are now regarded as highly successful DDSs for the treatment of diverse diseases. This review aims to present the development and applications of DDSs based on chemically-functionalized MOF nanostructures in the context of cancer treatment. A concise overview of the structure, synthesis, and mode of action of MOF-DDS is provided.

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.

Nanobiosensors Design Using 2D Materials: Implementation in Infectious and Fatal Disease Diagnosis

Nanobiosensors are devices that utilize a very small probe and any form of electrical, optical, or magnetic technology to detect and analyze a biochemical or biological process. With an increasing population today, nanobiosensors have become the broadly used electroanalytical tools for the timely detection of many infectious (dengue, hepatitis, tuberculosis, leukemia, etc.) and other fatal diseases, such as prostate cancer, breast cancer, etc., at their early stage. Compared to classical or traditional analytical methods, nanobiosensors have significant benefits, including low detection limit, high selectivity and sensitivity, shorter analysis duration, easier portability, biocompatibility, and ease of miniaturization for on-site monitoring. Very similar to biosensors, nanobiosensors can also be classified in numerous ways, either depending on biological molecules, such as enzymes, antibodies, and aptamer, or by working principles, such as optical and electrochemical. Various nanobiosensors, such as cyclic voltametric, amperometric, impedimetric, etc., have been discussed for the timely monitoring of the infectious and fatal diseases at their early stage. Nanobiosensors performance and efficiency can be enhanced by using a variety of engineered nanostructures, which include nanotubes, nanoparticles, nanopores, self-adhesive monolayers, nanowires, and nanocomposites. Here, this mini review recaps the application of two-dimensional (2D) materials, especially graphitic carbon nitride (g-C₃N₄), graphene oxide, black phosphorous, and MXenes, for the construction of the nanobiosensors and their application for the diagnosis of various infectious diseases at very early stage.

Recent developments in biosensing methods for extracellular vesicle protein characterization

Research into extracellular vesicles (EVs) has grown significantly over the last few decades with EVs being widely regarded as a source of biomarkers for human health and disease with massive clinical potential. Secreted by every cell type in the body, EVs report on the internal cellular conditions across all tissue types. Their presence in readily accessible biofluids makes the potential of EV biosensing highly attractive as a noninvasive diagnostic platform via liquid biopsies. However, their small size (50-250 nm), inherent heterogeneity, and the complexity of the native biofluids introduce challenges for effective characterization, thus, limiting their clinical utility. This has led to a surge in the development of various novel EV biosensing techniques, with capabilities beyond those of conventional methods that have been directly transferred from cell biology. In this review, key detection principles used for EV biosensing are summarized, with a focus on some of the most recent and fundamental developments in the field over the last 5 years. This article is categorized under: Diagnostic Tools > Biosensing Diagnostic Tools > In Vitro Nanoparticle-Based Sensing.

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.

Recent advances in determination applications of emerging films based on nanomaterials

Sensitive and facile detection of analytes is crucial in various fields such as agriculture production, food safety, clinical diagnosis and therapy, and environmental monitoring. However, the synergy of complicated sample pretreatment and detection is an urgent challenge. By integrating the inherent porosity, processability and flexibility of films and the diversified merits of nanomaterials, nanomaterial-based films have evolved as preferred candidates to meet the above challenge. Recent years have witnessed the flourishment of films-based detection technologies due to their unique porous structures and integrated physical/chemical merits, which favors the separation/collection and detection of analytes in a rapid, efficient and facile way. In particular, films based on nanomaterials consisting of 0D metal-organic framework particles, 1D nanofibers and carbon nanotubes, and 2D graphene and analogs have drawn increasing attention due to incorporating new properties from nanomaterials. This paper summarizes the progress of the fabrication of emerging films based on nanomaterials and their detection applications in recent five years, focusing on typical electrochemical and optical methods. Some new interesting applications, such as point-of-care testing, wearable devices and detection chips, are proposed and emphasized. This review will provide insights into the integration and processability of films based on nanomaterials, thus stimulate further contributions towards films based on nanomaterials for high-performance analytical-chemistry-related applications.

Black Phosphorous Aptamer-based Platform for Biomarker Detection

Black phosphorus nanostructures (nano-BPs) mainly include BP nanosheets (BP NSs), BP quantum dots (BPQDs), and other nano-BPs-based particles at nanoscale. Firstly discovered in 2014, nano-BPs are one of the most popular nanomaterials. Different synthesis methods are discussed in short to understand the basic concepts and developments in synthesis. Exfoliated nano-BPs, i.e. nano-BPs possess high surface area, high photothermal conversion efficacy, excellent biocompatibility, high charge carrier mobility (~1000 cm^-2V^-1s^-1), thermal conductivity of 86 Wm^-1K^-1; and these properties make it a highly potential candidate for fabrication of biosensing platform. These properties enable nano-BPs to be promising photothermal/drug delivery agents as well as in electrochemical data storage devices and sensing devices; and in super capacitors, photodetectors, photovoltaics and solar cells, LEDs, super-conductors, etc. Early diagnosis is very critical in the health sector scenarios. This review attempts to highlight the attempts made towards attaining stable BP, BP-aptamer conjugates for successful biosensing applications. BP-aptamer- based platforms are reviewed to highlight the significance of BP in detecting biological and physiological markers of cardiovascular diseases and cancer; to be useful in disease diagnosis and management.

Applications of electrochemical biosensors based on 2D materials and their hybrid composites in hematological malignancies diagnosis

Hematological malignancies encompass a wide variety of severe diseases that pose a serious threat to human health. Given the fact that hematological malignancies are difficult to treat due to their unpredictable and rapid deterioration and high rates of recurrence, growing attention has been paid to their early screening and diagnosis. However, developing a rapid and effective diagnostic tool featuring a noninvasive sampling technique is still extremely challenging. In recent years, novel nanomaterials-based electrochemical biosensors have attracted great interest because of such advantages as simple operation, low cost, fast response, etc. As a kind of rising nanomaterials, two-dimensional materials have excellent electronic and chemical properties, which have been proven to improve the performance of electrochemical biosensors. This review summarizes the applications of different types of electrochemical biosensors (nucleic acid sensors, immunosensors, aptamer biosensors, and cytosensors) based on two-dimensional materials in the detection of biological molecules related to hematological malignancies. Two-dimensional materials-based electrochemical biosensors designed for the diagnosis of leukemia could rapidly detect the target biomolecules at a trace level and show great merits such as wide linear range, low detection limit, high sensitivity, excellent selectivity, and cost-effectiveness. In addition, these biosensors have also achieved satisfactory results in the diagnosis of lymphoma and multiple myeloma. Thus, two-dimensional materials-based electrochemical biosensors are attractive for the early diagnosis of hematological malignancies in clinical practice. Nevertheless, more efforts are still required to further improve the performance of electrochemical biosensors. In this review, we propose the possible main concerns in the design of future two-dimensional materials-based electrochemical biosensors, involving the development of sensors for synchronous detection of diverse target biomolecules, the exploration of other superior two-dimensional materials, the simplification of the sensors fabrication process, the construction of new hybrid structures and how to avoid possible environmental issues.

Ultrasensitive dual-signal electrochemical ratiometric aptasensor based on Co-MOFs with intrinsic self-calibration property for Mucin 1

The concentration of tumor biomarker Mucin 1 (MUC 1) is highly related with many diseases, which can be employed for the early diagnosis of cancer. In this paper, an electrochemical ratiometric aptasensor with intrinsic self-calibration property for the detection of MUC 1 is presented. In this paper, Co-MOFs themselves were employed as signal substances. This strategy was fabricated by using gold nanoparticles@black phosphorus (BP) as the substrate on the electrode, followed by modification of DNA nanotetrahedrons (DTN) via Au-S bond. The terminal of DTN contains MUC 1 aptamer. In the presence of MUC 1, the signal of DNA-labeled Co-MOFs can be detected. The current signal of Co-MOFs increased and that of thionine (as reference) was unchanged upon the addition of MUC 1. Thus, an intrinsic self-calibration aptasensor was achieved. In order to simplify the modification procedure, the electrolyte solution thionine was employed as an inner reference probe. Moreover, coupling of the hybridization chain reaction (HCR) with these MOFs signal tags presents an enzyme-free method for signal amplification, endowing the proposed ratiometric biosensor detection with high reproducibility and high sensitivity. The current ratio (I_IR/I_SP) remained stable over 30 individual measurements performed on ten different working electrodes. Even ten repeated scans performed on a single electrode exhibited a constant current ratio. The electrochemical ratiometric aptasensor is highly sensitivity for MUC 1 with the detection limit of 1.34 fM. Our proposed ratiometric sensor has great potential for the detection of cancer-related biomarkers.

Picomolar glutathione detection based on the dual-signal self-calibration electrochemical sensor of ferrocene-functionalized copper metal-organic framework via solid-state electrochemistry of cuprous chloride

Chemical biosensing techniques are essential for food analysis and disease diagnosis. Nanomaterials with redox activity show great potential in electrochemical analysis, acting as signal labels or signal amplification unit, which can reflect the targets concentration in foods and biological samples. Here, an ultra-sensitive dual-signal intrinsic self-calibration electrochemical platform for GSH was firstly fabricated based on the novel electroactive nanomaterial of ferrocene-functionalized copper metal-organic framework (Fc-Cu-MOF). Due to the solid-state electrochemical property of cuprous chloride (CuCl), a sharp characteristic peak with an increased signal appears with the coexistence of chloride ions in solution. The stronger specific affinity between Cu⁺ and GSH than that of Cu⁺ and Cl^- triggers a "crowding effect" that causes the current signal of CuCl decrease greatly. Meanwhile, the peak current of ferrocene keeps unchanged as an internal reference. Based on the ratio of the peak current variation (ΔI_Cu/ΔI_Fc) as the signal output, Fc-Cu-MOF modified electrode showed wider linear range in 0.1 nM -1 μM for GSH with the detection limit as low as 0.025 nM. And the sensor was successfully applied in the determination of GSH with excellent recoveries in various real samples such as food and serum samples, providing good prospect in application of bioanalysis and food screening.

Understanding the bidirectional interactions between two-dimensional materials, microorganisms, and the immune system

Two-dimensional (2D) materials such as the graphene-based materials, transition metal dichalcogenides, transition metal carbides and nitrides (MXenes), black phosphorus, hexagonal boron nitride, and others have attracted considerable attention due to their unique physicochemical properties. This is true not least in the field of medicine. Understanding the interactions between 2D materials and the immune system is therefore of paramount importance. Furthermore, emerging evidence suggests that 2D materials may interact with microorganisms - pathogens as well as commensal bacteria that dwell in and on our body. We discuss the interplay between 2D materials, the immune system, and the microbial world in order to bring a systems perspective to bear on the biological interactions of 2D materials. The use of 2D materials as vectors for drug delivery and as immune adjuvants in tumor vaccines, and 2D materials to counteract inflammation and promote tissue regeneration, are explored. The bio-corona formation on and biodegradation of 2D materials, and the reciprocal interactions between 2D materials and microorganisms, are also highlighted. Finally, we consider the future challenges pertaining to the biomedical applications of various classes of 2D materials.

Monoelemental two-dimensional boron nanomaterials beyond theoretical simulations: From experimental preparation, functionalized modification to practical applications

During the past decade, there is an explosive growth of theoretical and computational studies on 2D boron-based nanomaterials. In terms of extensive predictions from theoretical simulations, borophene, boron nanosheets and 2D boron derivatives show excellent structural, electronic, photonic and nonlinear optical characteristics, and potential applications in a wide range of fields. In recent years, previous studies have reported the successful experimental preparations, superior properties, multi-functionalized modifications of various 2D boron and its derivatives, which show many practical applications in significant fields. To further promote the ever-increasing experimental studies, this present review systematically summarizes recent progress on experimental preparation methods, functionalized modification strategies and practical applications of 2D boron-based nanomaterials and multifunctional derivatives. Firstly, this review summarizes the experimental preparation methods, including molecular beam epitaxy, chemical vapor deposition, liquid-phase exfoliation, chemical reaction, and other auxiliary methods. Then, various strategies for functionalized modification are introduced overall, focusing on borophene derivatives, boron-based nanosheets, atom-introduced, chemically-functionalized borophene and boron nanosheets, borophene or boron nanosheet-based heterostructures, and other functionalized 2D boron nanomaterials. Subsequently, various potential applications are discussed in detail, involving energy storage, catalysis conversion, photonics, optoelectronics, sensors, bio-imaging, biomedicine therapy, and adsorption. We comment the state-of-the-art related studies concisely, and also discuss the current status, probable challenges and perspectives rationally. This review is timely, comprehensive, in-depth and highly attractive for scientists from multiple disciplines and scientific fields, and can facilitate further development of advanced functional low-dimensional nanomaterials and multi-functionalized systems toward high-performance practical applications in significant fields.

Rapid On-Chip Isolation of Cancer-Associated Exosomes and Combined Analysis of Exosomes and Exosomal Proteins

Exosomes are lipid bilayer extracellular vesicles secreted by various types of cells and inherit abundant molecular information from parental cells. Tumor-derived exosomes have been widely recognized as noninvasive biomarkers for early cancer diagnosis and surveillance, but the separation of intact exosomes and detection of exosomal proteins remain challenging. Herein, we proposed a microfluidic chip for specific exosome isolation, integrated with sensitive quantification by a novel PTCDI-aptamer signal switch strategy. To enhance the capture efficiency, an alternating drop-shaped micropillar array was designed to assist the capture of tumor-derived exosomes by Tim4-modified magnetic beads (Tim4 beads) on the chip. Following capture, a chelating agent can easily elute intact exosomes which were further used for profiling exosomal surface proteins by the multiplexed fluorescence turn-on approach. Profiting from the efficient on-chip enrichment of the Tim4 beads and superior fluorescence signal transduction strategy, the detection limit of the analysis platform for HepG2 exosomes is as low as 8.69 × 10³ particles/mL with a wide linear range spanning 6 orders of magnitude. Meanwhile, the proposed platform could recognize subtle changes in protein levels on the exosomal surface from various cell lines. More importantly, this strategy is successfully applied to analyze exosomes in human serum to distinguish liver cancer patients from healthy individuals. Combined analysis of different types of biomarkers on the exosomal membrane surface can greatly improve the accuracy of cancer type identification and disease monitoring. We hope that this convenient, rapid, and sensitive platform may become a powerful tool in the field of exosome analysis and early cancer screening.

Specifically triggered dissociation based ratiometric electrochemical sensor for H2O2 measurement in food samples

A novel ratiometric strategy based electrochemical sensor was developed to quantitative assay of H₂O₂ in different food samples. 4-aminophenylboronic acid pinacol ester (ABAPE) dissociation was specifically triggered by H₂O₂ to generate electro-active 4-aminophenol (4-AP), which not only can be oxidized to indirectly indicate the concentration of H₂O₂, but also endowed the sensor with high selectivity. Meanwhile, a reference probe of poly(thionine) (TH) was modified with ketjen black (KB) and gold nanoparticles (AuNPs) on electrode surface. KB and AuNPs displayed high electrocatalytic activity to 4-AP. A current ratio between 4-AP and TH (i/i_TH) showed a good linear relationship with the concentration of H₂O₂ in a range of 3.0 × 10^-7 - 1.0 × 10^-4 mol/L (0.010 ppm - 3.40 ppm) with a limit of detection of 2.6 × 10^-7 mol/L (0.009 ppm) (S/N = 3). Moreover, the ratiometric strategy based sensor possessed good accuracy, reliability, and stability, and successfully determined H₂O₂ in food samples with satisfactory results.

Triple-color fluorescence co-localization of PD-L1-overexpressing cancer exosomes

Programed cell death ligand 1 (PD-L1) is a protein biomarker overexpressed on exosomes derived from tumor cells. It plays an important role in tumor diagnosis, screening, evaluation of therapeutic efficacy, and prognosis. In this study, a facile method is presented to detect PD-L1-overexpressing cancer exosomes with high specificity and sensitivity. First, gold nanospheres (GNSs) were attached to the bottom of an eight-well chambered slide by electrostatic adsorption, forming the detection substrate. Then, Cy5-labeled CD63 aptamers (i.e., the capture probes) were modified on the GNSs by Au-S bond. After adding samples containing target exosomes which were stained by membrane dyes DiI in advance, FAM-labeled PD-L1 aptamers (i.e., the immunoprobes) were added to recognize PD-L1 on the target exosomes. By triple-color fluorescence co-localization (TFC) of the Cy5, DiI, and FAM channels, highly sensitive and reliable detection of the PD-L1-overexpressing exosomes was achieved in the concentration range 7.78 × 10¹ to 7.78 × 10⁴ particles/mL with a detection limit down to 6 particles/mL. The advantages of the proposed detection method include the following; first, the detection substrate is easy to prepare and convenient to clean. Second, the TFC strategy can completely exclude nonspecific reaction sites and thus significantly improves the accuracy. Such a facile and reliable detection method holds a great potential in exosome-based cancer theranostics. In this paper, we proposed a triple-color fluorescence co-localization (TFC) strategy to significantly improve the reliability of exosome detection and the detection substrate is easy to prepare and convenient to clean. In addition, the LOD is down to 6 particles/mL, which is quite low compared with other detection methods.

Recent advances in the selection of cancer-specific aptamers for the development of biosensors

An early diagnosis has the potential to greatly decrease cancer mortality. For that purpose, specific cancer biomarkers have been molecularly targeted by aptamer sequences to enable an accurate and rapid detection. Aptamer-based biosensors for cancer diagnostics are a promising alternative to those using antibodies, due to their high affinity and specificity to the target molecules and advantageous production. Synthetic nucleic acid aptamers are generated by in vitro Systematic Evolution of Ligands by Exponential enrichment (SELEX) methodologies that have been improved over the years to enhance the efficacy and to shorten the selection process. Aptamers have been successfully applied in electrochemical, optical, photoelectrochemical and piezoelectrical-based detection strategies. These aptasensors comprise a sensitive, accurate and inexpensive option for cancer detection being used as point-of-care devices. This review highlights the recent advances in cancer biomarkers, achievements and optimizations made in aptamer selection, as well as the different aptasensors developed for the detection of several cancer biomarkers.

Dual-Mode and Label-Free Detection of Exosomes from Plasma Using an Electrochemical Quartz Crystal Microbalance with Dissipation Monitoring

The biomolecular contents of extracellular vesicles, such as exosomes, have been shown to be crucial in intercellular communication and disease propagation. As a result, there has been a recent surge in the exploration of novel biosensing platforms that can sensitively and specifically detect exosomal content such as proteins and nucleic acids, with a view toward application in diagnostic assays. Here, we demonstrate dual-mode and label-free detection of plasma exosomes using an electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D). The platform adopts a direct immunosensing approach to effectively capture exosomes via their surface protein expression of CD63. By combining QCM-D with a tandem in situ electrochemical impedance spectroscopy measurement, we are able to demonstrate relationships between mass, viscoelasticity and impedance inducing properties of each functional layer and analyte. In addition to lowering the limit of detection (by a factor of 2-4) to 6.71 × 10⁷ exosome-sized particles (ESP) per mL in 25% v/v serum, the synergy between dissipation and impedance response introduces improved sensing specificity by offering further distinction between soft and rigid analytes, thereby promoting EQCM-D as an important technique for exosome analysis.

Fabricated Metal-Organic Frameworks (MOFs) as luminescent and electrochemical biosensors for cancer biomarkers detection

In the health domain, a major challenge is the detection of diseases using rapid and cost-effective techniques. Most of the existing cancer detection methods show poor sensitivity and selectivity and are time consuming with high cost. To overcome this challenge, we analyzed porous fabricated metal-organic frameworks (MOFs) that have better structures and porosities for enhanced biomarker sensing. Here, we summarize the use of fabricated MOF luminescence and electrochemical sensors in devices for cancer biomarker detection. Various strategies of fabrication and the role of fabricated materials in sensing cancer biomarkers have been studied and described. The structural properties, sensing mechanisms, roles of noncovalent interactions, limits of detection, modeling, advantages, and limitations of MOF sensors have been well-discussed. The study presents an innovative technique to detect the cancer biomarkers by the use of luminescence and electrochemical MOF sensors. In addition, the potential association studies have been opening the way for personalized patient treatments and the development of new cancer-detecting devices.

Dual-Mode and Label-Free Detection of Exosomes from Plasma Using an Electrochemical Quartz Crystal Microbalance with Dissipation Monitoring

The biomolecular contents of extracellular vesicles, such as exosomes, have been shown to be crucial in intercellular communication and disease propagation. As a result, there has been a recent surge in the exploration of novel biosensing platforms that can sensitively and specifically detect exosomal content such as proteins and nucleic acids, with a view toward application in diagnostic assays. Here, we demonstrate dual-mode and label-free detection of plasma exosomes using an electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D). The platform adopts a direct immunosensing approach to effectively capture exosomes via their surface protein expression of CD63. By combining QCM-D with a tandem in situ electrochemical impedance spectroscopy measurement, we are able to demonstrate relationships between mass, viscoelasticity and impedance inducing properties of each functional layer and analyte. In addition to lowering the limit of detection (by a factor of 2–4) to 6.71 × 10⁷ exosome-sized particles (ESP) per mL in 25% v/v serum, the synergy between dissipation and impedance response introduces improved sensing specificity by offering further distinction between soft and rigid analytes, thereby promoting EQCM-D as an important technique for exosome analysis.

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.

A colorimetric aptasensor based on a hemin/EpCAM aptamer DNAzyme for sensitive exosome detection

Exosomes are considered as potential biomarkers that can reflect information from their parent cell-associated cancer microenvironment.