Sensitive detection of MCF-7 human breast cancer cells by using a novel DNA-labeled sandwich electrochemical biosensor

Nanotechnology-based optical sensors for Baijiu quality and safety control

Baijiu quality and safety have received considerable attention owing to the gradual increase in its consumption. However, owing to the unique and complex process of Baijiu production, issues leading to quality and safety concerns may occur during the manufacturing process. Therefore, establishing appropriate analytical methods is necessary for Baijiu quality assurance and process control. Nanomaterial (NM)-based optical sensing techniques have garnered widespread interest because of their unique advantages. However, comprehensive studies on nano-optical sensing technology for quality and safety control of Baijiu are lacking. In this review, we systematically summarize NM-based optical sensor applications for the accurate detection and quantification of analytes closely related to Baijiu quality and safety. Furthermore, we evaluate the sensing mechanisms for each application. Finally, we discuss the challenges nanotechnology poses for Baijiu analysis and future trends. Overall, nanotechnological approaches provide a potentially useful alternative for simplifying Baijiu analysis and improving final product quality and safety.

Precision in cancer diagnostics: ultra-sensitive detection of MCF-7 breast cancer cells by gold nanostructure-enhanced electrochemical biosensing

Timely identification of cancers is pivotal in optimizing treatment efficacy and reducing their widespread impact. This study introduces a novel biosensor for the sensitive electrochemical detection of cancer cells overexpressing mucin 1 (MUC1), a well-established model for breast cancer. The sensor substrate comprises gold columnar nanostructures obtained through glancing angle deposition (GLAD) of copper nanostructures, subsequently replaced by gold via a facile galvanic replacement process. Functionalizing these gold nanostructures with aptamers targeting the MUC1 glycoproteins, a prominent cancer biomarker, enables specific recognition of MCF-7 breast cancer cells. The proposed electrochemical sensing platform offers several advantages, including high selectivity, a wide linear range of detection, a low detection limit of 30 cells per mL, and long-term stability, rendering this sensor highly desirable for definitive breast cancer diagnosis.

Label-free electrochemical biosensor based on green-synthesized reduced graphene oxide/Fe3O4/nafion/polyaniline for ultrasensitive detection of SKBR3 cell line of HER2 breast cancer biomarker

Cancer stands as one of the most impactful illnesses in the modern world, primarily owing to its lethal consequences. The fundamental concern in this context likely stems from delayed diagnoses in patients. Hence, detecting various forms of cancer is imperative. A formidable challenge in cancer research has been the diagnosis and treatment of this disease. Early cancer diagnosis is crucial, as it significantly influences subsequent therapeutic steps. Despite substantial scientific efforts, accurately and swiftly diagnosing cancer remains a formidable challenge. It is well known that the field of cancer diagnosis has effectively included electrochemical approaches. Combining the remarkable selectivity of biosensing components-such as aptamers, antibodies, or nucleic acids-with electrochemical sensor systems has shown positive outcomes. In this study, we adapt a novel electrochemical biosensor for cancer detection. This biosensor, based on a glassy carbon electrode, incorporates a nanocomposite of reduced graphene oxide/Fe3O4/Nafion/polyaniline. We elucidated the modification process using SEM, TEM, FTIR, RAMAN, VSM, and electrochemical methods. To optimize the experimental conditions and monitor the immobilization processes, electrochemical techniques such as CV, EIS, and SWV were employed. The calibration graph has a linear range of 102-106 cells mL-1, with a detection limit of 5 cells mL-1.

Ag nanorod@PEI-Ag nanohybrid as an excellent signal label for sensitive and rapid detection of serum HER2

The accurate detection of Human epidermal growth factor receptor-2 (HER2) as a critical breast cancer biomarker can be essential for the early selection of therapeutic approaches. HER2 is a prominent component of a signaling network. Overexpression of the HER2 protein due to amplification of its gene leads to the development of an aggressive subtype of breast cancer. Patients with tumors that overexpress HER2 are eligible for treatment that significantly reduces mortality rates. Herein, we present a fast and simple method for detecting serum HER2. A new electrochemical label has been developed using charged Ag nanorod@ polyethylenimine-Ag (Ag NR@ PEI-Ag) nanohybrid. The synthesized Ag NR@PEI-Ag nanohybrid simultaneously has the electroactive property of silver and the large surface area of the PEI, which results in the enhancement of the detection signal. So, using Ag NR@PEI-Ag nanohybrid as the electrochemical label, a simple, fast, and sensitive electrochemical biosensor was designed to detect HER2. This way, after immobilizing HER2 aptamer on the Au electrode surface, HER2 or human serum was exposed to the aptamer. Then, the positively charged Ag NR@PEI-Ag nanohybrid was adsorbed onto the negatively charged aptamer-HER2 complex, and the current that was produced due to the Ag/AgCl reaction was measured as the electrochemical signal. The aptasensor shows a broad linear response from 10-12 to 10-7 g, a low detection limit (LOD) of 10 pg, and a total assay time of ~ 30 min.

Diverse applications and development of aptamer detection technology

Aptamers have received extensive attention in recent years because of their advantages of high specificity, high sensitivity and low immunogenicity. Aptamers can perform almost all functions of antibodies through the combination of spatial structure and target, which are called "chemical antibodies". At present, aptamers have been widely used in cell imaging, new drug development, disease treatment, microbial detection and other fields. Due to the diversity of modifications, aptamers can be combined with different detection technologies to construct aptasensors. This review focuses on the diversity of aptamers in the field of detection and the development of aptamer-based detection technology and proposes new challenges for aptamers in this field.

Impact of Nanomedicine in Women's Metastatic Breast Cancer

Metastatic breast cancer is responsible for 90% of mortalities among women suffering from various types of breast cancers. Traditional cancer treatments such as chemotherapy and radiation therapy can cause significant side effects and may not be effective in many cases. However, recent advances in nanomedicine have shown great promise in the treatment of metastatic breast cancer. For example, nanomedicine demonstrated robust capacity in detection of metastatic cancers at early stages (i.e., before the metastatic cells leave the initial tumor site), which gives clinicians a timely option to change their treatment process (for example, instead of endocrine therapy they may use chemotherapy). Here recent advances in nanomedicine technology in the identification and treatment of metastatic breast cancers are reviewed.

Smartphone-assisted lab-in-a-tube device using gold nanocluster-based aptasensor for detection of MUC1-overexpressed tumor cells

Developing smartphone technology for point-of-care diagnosis is one of the current favorable trends in the field of biosensors. In fact, using smartphones can provide better accessibility and facility for rapid diagnosis of diseases. On the other hand, the detection of circulating tumor cells (CTCs) is one of the recent methods for the early diagnosis of cancer. Here, a new smartphone-assisted lab-in-a-tube device is introduced for the detection of Mucin 1 (MUC1) overexpressed tumor-derived cell lines using gold nanoclusters (GNCs)-based aptasensor. Accordingly, commercial polyurethane (PU) foam was first coated with graphene oxide (GO) to increase its surface area (8.45-fold), and improve its wettability. The surface of the resulting three-dimensional PU-GO (3DPU-GO) platform was then modified by MUC1 aptamer-GNCs to provide the required sensitivity and specificity through a turn "on/off" detection system. The proposed biosensor was first optimized with a spectrophotometer method. Afterward, findings were evaluated based on the red color intensity of the lab-in-a-tube system; and indicated the high ability of the biosensor for detection of MUC1-overexpressed tumor cell lines in the range of 250-20,000 cells mL^-1 with a limit of detection of 221 cells mL^-1. In addition, the developed biosensor showed a decent selectivity against positive-control cell lines (MCF-7, and HT-29) in comparison to negative-control cell lines (HEK293, and L929). Notably, the results represented good accordance with reference methods including spectroscopy devices. Ultimately, the results of this work bring a new perspective to the field of point-of-care detection and can be considered in future biosensors.

Ultrasensitive PEC cytosensor for breast cancer cells detection and inhibitor screening based on plum-branched CdS/Bi2S3 heterostructures

Breast cancer is the most common malignant tumor in women, which seriously threatens the life and health of patients. Therefore, facile and sensitive detection of human breast cancer cells is crucial for cancer diagnosis. In this work, plum-branched CdS/Bi₂S₃ heterostructures (CdS/Bi₂S₃ HSs) were synthesized under hydrothermal condition, whose photoelectrochemical (PEC) property and biocompatibility were scrutinously investigated. In parallel, a signal amplification strategy was designed based on immune recognition between epidermal growth factor receptor (EGFR) overexpressed on membrane of breast cancer cells MDA-MB-231 and its aptamer. Integration of the above together, a highly sensitive PEC cytosensor was developed for analysis of target MDA-MB-231 cells, exhibiting a wider linear range of 1 × 10² ∼ 3 × 10⁵ cells mL^-1 with a limit of detection (LOD) down to 6 cells mL^-1 (S/N = 3). Further, the biosensor was explored for anticancer drug (e.g., dacomitinib) screening by monitoring the variations in the PEC signals of the expressed EGFR upon drug stimulation. The obtained CdS/Bi₂S₃ HSs are identified as promising and feasible photoactive material for determination of cancer cells and drug screening in clinic and related research.

Carbon-based biosensors from graphene family to carbon dots: A viewpoint in cancer detection

According to the latest report by International Agency for Research on Cancer, 19.3 million new cancer cases and 10 million cancer deaths were globally reported in 2020. Early diagnosis can reduce these numbers significantly, and biosensors have appeared to be a solution to this problem as, unlike the traditional methods, they have low cost, rapid process, and do not need experts present on site for use. These devices have been incorporated to detect many cancer biomarkers and measure cancer drug delivery. To design these biosensors, a researcher must know about their different types, properties of nanomaterials, and cancer biomarkers. Among all types of biosensors, electrochemical and optical biosensors are the most sensitive and promising sensors for detecting complicated diseases like cancer. The carbon-based nanomaterial family has attracted lots of attention due to their low cost, easy preparation, biocompatibility, and significant electrochemical and optical properties. In this review, we have discussed the application of graphene and its derivatives, carbon nanotubes (CNTs), carbon dots (CDs), and fullerene (C60), for designing different electrochemical and optical cancer-detecting biosensors. Furthermore, the application of these carbon-based biosensors for detecting seven widely studied cancer biomarkers (HER2, CEA, CA125, VEGF, PSA, Alpha-fetoprotein, and miRNA21) is reviewed. Finally, various fabricated carbon-based biosensors for detecting cancer biomarkers and anticancer drugs are comprehensively summarized as well.

Synthesis and characterization of folate-functionalized silica-based materials and application for bioimaging of cancer cells

Early-stage detection is a vital factor in the later treatment and prognosis of cancer. Enhancing the sensitivity and specificity of the cancer detection pathological and experimental approaches can affect the morbidity and mortality of this disease. A folic acid (FA)-functionalized silica quantum dots (SiQDs)/KCC-NH₂@SiO₂ nanomaterials were synthesized and characterized as a bioimaging agent of the MCF 7 cancer cells. These nanoparticles showed biocompatible nature with specificity towards folate receptor (FR)-overexpressed MCF 7 cancer cells. Viability findings suggested that the SiQDs/KCC-NH₂@SiO₂/FA nanomaterials have nontoxic nature towards the cells in the concentration of 200 μg/mL. Fluorescence microscopy images were utilized to estimate the cell internalization of the nanoparticles and further verified by the flow cytometry technique. The differentiation ability of the nanoparticles was also approved by incubation with FR-negative HEK 293 normal cells. The SiQDs/KCC-NH₂@SiO₂/FA nanoparticle exhibited high stability, bright and high quantum yield fluorescence emission, proposing as a high-quality material for in vivo bioimaging of FR-overexpressed circulating tumoral cancer cells (CTCs).

Graphene-Based Electrochemical Biosensors for Breast Cancer Detection

Breast cancer (BC) is the most common cancer in women, which is also the second most public cancer worldwide. When detected early, BC can be treated more easily and prevented from spreading beyond the breast. In recent years, various BC biosensor strategies have been studied, including optical, electrical, electrochemical, and mechanical biosensors. In particular, the high sensitivity and short detection time of electrochemical biosensors make them suitable for the recognition of BC biomarkers. Moreover, the sensitivity of the electrochemical biosensor can be increased by incorporating nanomaterials. In this respect, the outstanding mechanical and electrical performances of graphene have led to an increasingly intense study of graphene-based materials for BC electrochemical biosensors. Hence, the present review examines the latest advances in graphene-based electrochemical biosensors for BC biosensing. For each biosensor, the detection limit (LOD), linear range (LR), and diagnosis technique are analyzed. This is followed by a discussion of the prospects and current challenges, along with potential strategies for enhancing the performance of electrochemical biosensors.

Synthesis and In Vitro Testing of YVO4:Eu3+@silica-NH-GDA-IgG Bio-Nano Complexes for Labelling MCF-7 Breast Cancer Cells

We present a visual tool and facile method to detect MCF-7 breast cancer cells by using YVO₄:Eu³⁺@silica-NH-GDA-IgG bio-nanocomplexes. To obtain these complexes, YVO₄:Eu³⁺ nanoparticles with a uniform size of 10-25 nm have been prepared firstly by the hydrothermal process, followed by surface functionalization to be bio-compatible and conjugated with cancer cells. The YVO₄:Eu³⁺@silica-NH-GDA-IgG nanoparticles exhibited an enhanced red emission at 618 nm under an excitation wavelength of 355 nm and were strongly coupled with MCF-7 breast cancer cells via biological conjugation. These bio-nanocomplexes showed a superior sensitiveness for MCF-7 cancer cell labelling with a detection percentage as high as 82%, while no HEK-293A healthy cells were probed under the same conditions of in vitro experiments. In addition, the detection percentage of MCF-7 breast cancer cells increased significantly via the functionalization and conjugation of YVO₄:Eu³⁺ nanoparticles. The experimental results demonstrated that the YVO₄:Eu³⁺@silica-NH-GDA-IgG bio-nanocomplexes can be used as a promising labelling agent for biomedical imaging and diagnostics.

Tailored point-of-care biosensors for liquid biopsy in the field of oncology

In the field of cancer detection, technologies to analyze tumors using biomarkers circulating in fluids such as blood have developed rapidly based on liquid biopsy. A proactive approach to early cancer detection can lead to more effective treatments with minimal side effects and better long-term patient survival. However, early detection of cancer is hindered by the existing limitations of conventional cancer diagnostic methods. To enable early diagnosis and regular monitoring and improve automation, the development of integrated point-of-care (POC) and biosensors is needed. This is expected to fundamentally change the diagnosis, management, and monitoring of response to treatment of cancer. POC-based techniques will provide a way to avoid complications that occur after invasive tissue biopsy, such as bleeding, infection, and pain. The aim of this study is to provide a comprehensive view of biosensors and their clinical relevance in oncology for the detection of biomarkers with liquid biopsies of proteins, miRNA, ctDNA, exosomes, and cancer cells. The preceding discussion also illustrates the changing landscape of liquid biopsy-based cancer diagnosis through nanomaterials, machine learning, artificial intelligence, wearable devices, and sensors, many of which apply POC design principles. With the advent of sensitive, selective, and timely detection of cancer, we see the field of POC technology for cancer detection and treatment undergoing a positive paradigm shift in the foreseeable future.

Nanotechnology‐based electrochemical biosensors for monitoring breast cancer biomarkers

Breast cancer is categorized as the most widespread cancer type among women globally. On-time diagnosis can decrease the mortality rate by making the right decision in the therapy procedure. These features lead to a reduction in medication time and socioeconomic burden. The current review article provides a comprehensive assessment for breast cancer diagnosis using nanomaterials and related technologies. Growing use of the nano/biotechnology domain in terms of electrochemical nanobiosensor designing was discussed in detail. In this regard, recent advances in nanomaterial applied for amplified biosensing methodologies were assessed for breast cancer diagnosis by focusing on the advantages and disadvantages of these approaches. We also monitored designing methods, advantages, and the necessity of suitable (nano) materials from a statistical standpoint. The main objective of this review is to classify the applicable biosensors based on breast cancer biomarkers. With numerous nano-sized platforms published for breast cancer diagnosis, this review tried to collect the most suitable methodologies for detecting biomarkers and certain breast cancer cell types.

Bovine serum albumin-gold nanoclusters protein corona stabilized polystyrene nanoparticles as dual-color fluorescent nanoprobes for breast cancer detection

Breast cancer is the most prevalent malignancy and the first leading cause of cancer-related mortality among the female population worldwide. Approaches for precise and reliable detection of breast cancer cells, particularly in the nascent state, are desperately needed for elevating the survival rate of patients bearing the breast tumor. In this work, we successfully performed the sensitive, precise, and reliable breast cancer cell detection using facilely fabricated bovine serum albumin-gold nanocluster (BSA-AuNCs) protein corona stabilized, epithelial cell adhesion molecule (EpCAM) aptamer linked fluorescent polystyrene nanoparticle (PS NP), termed as PS-BSA-AuNCs-Apt. The rapidly adsorbed BSA-AuNCs hard protein corona without complicated covalent conjugation not only imparted excellent colloidal stability to the PS nanoparticles, but also offered numerous active anchors for the targeted EpCAM aptamers to locate. With the remarkable aid of the aptamers specifically targeting the EpCAM-positive breast cancer cells, the PS-BSA-AuNCs-Apt emitted strong and photostable dual-color fluorescent signals for precise and reliable cancer cell detection by overcoming the false signals. The specific identification potency of the PS-BSA-AuNCs-Apt system was further verified by successfully detecting the xenografted breast tumor tissue. Notably, to the best of our knowledge, the protein corona formed nanoprobes was exploited for direct tumor cell and tissue detection with high efficacy for the first time, demonstrating their promising potential in clinical tumor detection.

Antifouling Electrochemical Biosensor Based on the Designed Functional Peptide and the Electrodeposited Conducting Polymer for CTC Analysis in Human Blood

Circulating tumor cells (CTCs) are considered reliable cancer biomarkers for the liquid biopsy of many types of tumors. The direct detection of CTCs in human blood with normal biosensors, however, remains challenging because of severe biofouling in blood that contains various proteins and a large number of cells. Herein, we report the construction of an antifouling electrochemical biosensor capable of assaying CTCs directly in blood, based on a designed multifunctional peptide and the electrodeposited conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT). The designed peptide possesses antifouling capability in complex biological media and specific recognition ability to capture breast cancer cells MCF-7. Meanwhile, electrodeposited PEDOT can promote electron transfer at the sensing interface, improve the signal-to-noise ratio for the detection, and thus enhance the sensitivity of the biosensor. The integration of the multifunctional peptide and conducting polymer PEDOT ensures that the developed biosensor is able to perform directly in blood samples without purification or separation. The antifouling electrochemical biosensor for the detection of MCF-7 cells exhibits a wide linear range over 4 orders, with a limit of detection (LOD) of 17 cells mL^-1. More interestingly, even when performing in 25% human blood, the biosensor still retains a linear response with an LOD of 22 cells mL^-1, without suffering significantly from biofouling in real blood. This work provides a promising strategy for the direct analysis of CTCs in human blood without a complicated pretreatment, and it may find practical application in the liquid biopsy of cancers.

A dual-recognition-controlled electrochemical biosensor for accurate and sensitive detection of specific circulating tumor cells

Accurate and sensitive assay of specific circulating tumor cells (CTCs) is of importance for the diagnosis, treatment, and metastasis monitoring of cancer. Herein, we have proposed a dual-recognition-controlled electrochemical biosensor in this work for the detection of specific CTCs. To this sensor, two aptamer hairpin probes are designed to be able to separately bind to two adjacent proteins on the cell membrane to activate the associative toehold for strand displacement reaction, which will then trigger a dimer-like rolling cycle amplification reaction, and finally produce significantly amplified electrochemical signals for sensitive quantification of target CTCs. In our design, only the case that the two proteins are simultaneously expressed on the cell membrane can result in obvious signal responses, which may greatly improve the accuracy of CTCs analysis. The proposed biosensor can possess excellent selectivity to distinguish target cells from different cancer cells. Moreover, the combination of rolling cycle amplification and DNA nanostructure capture probes can effectively lower the detection limit to 3 cells mL^-1. Notably, our biosensor can be applied to the assay of the target CTCs in the complex whole blood matrixes, verifying its strong stability and anti-interference. Thus, the as-proposed dual-recognition-controlled electrochemical biosensor may exhibit great promise in clinical cancer diagnosis and personalized medicine.

p-Co-BDC/AuNPs-based multiple signal amplification for ultra-sensitive electrochemical determination of miRNAs

In this work, we report AuNPs-decorated pyrolyzed Co-BDC nanosheets (p-Co-BDC/AuNPs) as high-performance electrocatalyst for developing an electrochemical platform. p-Co-BDC/AuNPs as a new electrocatalyst showed superior electrocatalytic activity towards the electrochemical oxidation of methylene blue (MB). Besides, magnetic p-Co-BDC/AuNPs can be well immobilized on the magnetic glassy carbon electrode without further assistance. The oxidation of MB can be reduced by ascorbic acid. Inspired by this phenomenon, an electrochemical biosensor was constructed based on multiple signal amplification for the diagnosis of miRNAs. Firstly, p-Co-BDC/AuNPs enhanced the electrochemical oxidation of MB. Then, strand displacement amplification reaction can form lots of double helix structure DNA to embed more MB molecules. Finally, ascorbic acid in the electrolyte was utilized to reduce the oxidation of MB and improve the electrochemical signal of MB electro-oxidation. The linear detection range for the detection of miRNAs is 100 aM to 10 nM, and the limit of detection is 86 aM. Furthermore, the constructed biosensor also displayed satisfactory selectivity, good reproducibility, and excellent recovery in the detection of real samples. We are convinced that our proposed multiple signal amplification strategy will provide more promising methods for the diagnosis of cancer.

Aptamer Embedded Arch-Cruciform DNA Assemblies on 2-D VS2 Scaffolds for Sensitive Detection of Breast Cancer Cells

Arch-cruciform DNA are self-assembled on AuNPs/VS₂ scaffold as a highly sensitive and selective electrochemical biosensor for michigan cancer foundation-7 (MCF-7) breast cancer cells. In the construction, arch DNA is formed using two single-strand DNA sequences embedded with the aptamer for MCF-7 cells. In the absence of MCF-7 cells, a cruciform DNA labeled with three terminal biotin is bound to the top of arch DNA, which further combines with streptavidin-labeled horseradish peroxidase (HRP) to catalyze the hydroquinone-H₂O₂ reaction on the electrode surface. The presence of MCF-7 cells can release the cruciform DNA and reduce the amount of immobilized HRP, thus effectively inhibiting enzyme-mediated electrocatalysis. The electrochemical response of the sensor is negatively correlated with the concentration of MCF-7 cells, with a linear range of 10~1 × 10⁵ cells/mL, and a limit of detection as low as 5 cells/mL (S/N = 3). Through two-dimensional materials and enzyme-based dual signal amplification, this biosensor may pave new ways for the highly sensitive detection of tumor cells in real samples.

Amplified electrochemical biosensing based on bienzymatic cascade catalysis confined in a functional DNA structure

Herein, an amplified and renewable electrochemical biosensor was developed via bienzymatic cascade catalysis of glucose oxidase (GOx) and horseradish peroxidase (HRP), which were confined in a functional Y-shaped DNA nanostructure oriented by a dual-thiol-ended hairpin probe (dSH-HP) with a paired stem as a rigid scaffold and unpaired loop as enclosed binding platform. For proof-of-concept assay of sequence-specific biomarker DNA related to Alzheimer's disease (aDNA), GOx and redox ferrocene-modified HRP (Fc@HRP) were chemically conjugated in two enzyme strands (GOx-ES1 and Fc@HRP-ES2), respectively. The repeated recycling of aDNA was powered by the displacement of GOx-ES1 by aDNA and exonuclease III (ExoIII)-assisted cleavage reaction for amplified output of numerous GOx-ES1 as dependent transducers, together with Fc@HRP-ES2 which was simultaneously hybridized with dSH-HP to assemble this DNA structure. Rationally, the bienzymatic cascade catalysis was motivated through GOx-catalyzed glucose oxidization to in situ generate hydrogen peroxide (H₂O₂) and overlapped HRP-catalyzed H₂O₂ decomposition to promote the electron transfer, producing significantly enhanced electrochemical signal of Fc with an ultrahigh sensitivity down to 0.22 fM of aDNA. Benefited from the unique design of dSH-HP-oriented bienzymatic cascades, this one-step strategy without non-specific blockers passivation was simple and renewable, and would pave a promising avenue for sensitive electrochemical assay of biomolecules.

Advanced Devices for Tumor Diagnosis and Therapy

At present, tumor diagnosis is performed using common procedures, which are slow, costly, and still presenting difficulties in diagnosing tumors at their early stage. Tumor therapeutic methods also mainly rely on large-scale equipment or non-intelligent treatment approaches. Thus, an early and accurate tumor diagnosis and personalized treatment may represent the best treatment option for a successful result, and the efforts in finding them are still in progress and mainly focusing on non-destructive, integrated, and multiple technologies. These objectives can be achieved with the development of advanced devices and smart technology that represent the topic of the current investigations. Therefore, this review summarizes the progress in tumor diagnosis and therapy and briefly explains the advantages and disadvantages of the described microdevices, finally proposing advanced micro smart devices as the future development trend for tumor diagnosis and therapy.

Electrochemical sensing technology for liquid biopsy of circulating tumor cells-a review

In recent years, a lot of new detection techniques for circulating tumor cells (CTCs) have been developed. Among them, electrochemical sensing technology has gradually developed because of its advantages of good selectivity, high sensitivity, low cost and rapid detection. Especially in the latest decade, the field of electrochemical biosensing has witnessed great progress, thanks to the merging of biosensing research area with nanotechnology, immunotechnology, nucleic acid technology, and microfluidic technology. In this review, the recent progress for the detection of CTCs according to the principle of detection was summarized and how they can contribute to the enhanced performance of such biosensors was explained. The latest electrode construction strategies such as rolling circle amplification reaction, DNA walker and microfluidic technology and their advantages were also introduced emphatically. Moreover, the main reasonswhy the existing biosensors have not been widely used clinically and the next research points were clearly put forward.

Semiconducting CuxNi3-x(hexahydroxytriphenylene)2 framework for electrochemical aptasensing of C6 glioma cells and epidermal growth factor receptor

A 2D CuNi metal-organic framework (MOF) named CuxNi3-x(HHTP)2 was synthesized with 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) as the linker and was used as a sensitive scaffold to adsorb aptamer strands for the electrochemical detection of living C6 glioma cells and one of their biomarkers, epidermal growth factor receptor (EGFR). Different from conventional MOFs, the CuxNi3-x(HHTP)2 MOF comprises long-range delocalized electrons, a graphene-analog nanostructure, multiple metal states (Cu0/Cu+/Cu2+ and Ni2+/Ni3+), and abundant oxygen vacancies. With these features, the CuxNi3-x(HHTP)2 MOF anchored a large amount of C6 cell-targeted aptamer strands via coordination among metal centers, oligonucleotides, π-π stacking, and van der Waals force. The CuxNi3-x(HHTP)2-based cytosensor showed a low limit of detection (LOD) of 21 cells mL-1 toward C6 glioma cells within a wide range from 50 cells mL-1 to 1 × 105 cells mL-1. Moreover, the proposed aptasensor displayed high selectivity, good stability, acceptable reproducibility, and a low LOD of 0.72 fg mL-1 for detecting EGFR with the concentration ranging from 1 fg mL-1 to 1 ng mL-1. The aptasensor based on the CuxNi3-x(HHTP)2 MOF exhibited superior sensing performance over those based on its monometallic analogues such as Cu3(HHTP)2 MOF and Ni3(HHTP)2 MOF. Hence, this sensing strategy based on a bimetallic semiconducting MOF shows great potential for cancer diagnosis.

A novel biosensor for the ultrasensitive detection of the lncRNA biomarker MALAT1 in non-small cell lung cancer

Long non-coding RNAs (lncRNAs) have been proposed as diagnostic biomarkers for the screening of non-small cell lung cancer and monitoring disease progression. Accordingly, new, rapid, and cost-effective lncRNA biosensors that can be used clinically are urgently needed. Herein, a novel effective and ultrasensitive electrochemical biosensor was developed based on a gold nanocage coupled with an amidated multi-walled carbon nanotube (Au NCs/MWCNT-NH₂)-decorated screen-printed carbon electrode (SPCE). Because of its large surface area, superior conductivity, and excellent biocompatibility, this SPCE Au NCs/MWCNT-NH₂ lncRNA biosensor showed a wide linear range (10^–7–10^–14 M) and low limit of detection limit (42.8 fM) coupled with satisfactory selectivity and stability. Compared to traditional RT-PCR, the proposed method exhibits acceptable stability, good selectivity, is simpler to operate, has faster detection, and uses less costly raw materials. In summary, this biosensor may be a powerful tool for detecting lncRNAs for efficient clinical prognosis and cancer diagnosis.

A label-free electrochemical immunosensor based on encapsulated signal molecules in mesoporous silica-coated gold nanorods for ultrasensitive assay of procalcitonin

For immobilization and signal amplification of the probes, it is feasible and promising by using porous nanomaterials as nanocarriers. Herein, a novel label-free electrochemical immmunosensor was efficiently designed for ultrasensitive detection of procalcitonin (PCT). The immunosensor was prepared by using porous silica-coated gold nanorods (Au NRs@m-SiO₂) to load electroactive dye thionine (Thi) on the electrode surface. Apart from the improved electrical conductivity, the porous feature highly increased the loading amount of Thi to boost the detection signals, while the good biocompatibility and protective microenvironment are beneficial to the largely improved stability for the target. For quantification of PCT, the developed immunosensor exhibited a good linear relationship in the antigen concentration range of 0.001-100 ng mL^-1 with an ultra-low limit of detection (LOD, 0.39 pg mL^-1, S/N = 3). Moreover, the built platform was successfully applied to such assay in human serum samples. The research provides some valuable guidelines for clinical screening and diagnosis of other biomarkers.

0D/2D heteronanostructure-integrated bimetallic CoCu-ZIF nanosheets and MXene-derived carbon dots for impedimetric cytosensing of melanoma B16-F10 cells

A novel heterogeneous architecture has been constructed integrating two-dimensional (2D) bimetallic CoCu-zeolite imidazole framework (CoCu-ZIF) and zero-dimensional (0D) Ti₃C₂T_x MXene-derived carbon dots (CDs) (represented by CoCu-ZIF@CDs). The prepared CoCu-ZIF@CDs were further explored as sensitive layer for anchoring B16-F10 cell-targeted aptamer strands and detecting B16-F10 cells from the biological environment. Basic characterization showed that CDs were homogeneously embedded within CoCu-ZIF NSs owing to their π-π stacking interaction, leading to outstanding fluorescence performance of the 0D/2D CoCu-ZIF@CD nanohybrid. As such, the CoCu-ZIF@CD-based cytosensor was applied to detect living B16-F10 cells through electrochemical techniques and cell imaging. Compared with CoCu-ZIF- and CD-based cytosensors, the constructed CoCu-ZIF@CD-based one showed superior sensing performance, with an extremely low limit of detection (LOD) of 33 cells∙mL^-1 and a wide range of suspension concentration of 1 × 10²-1 × 10⁵ cells∙mL^-1 B16-F10 cells. The developed cytosensor also demonstrated excellent detection performance, including cell imaging properties, good selectivity, high stability, and good reproducibility. By anchoring other probe molecules, the constructed CoCu-ZIF@CD-based biosensor can be extensively explored for early diagnosis of other analytes, thereby widening the applications of porous organic frameworks in biosensing and biomedical fields. A novel sensing system for melanoma B16-F10 cells based on a novel CoCu-ZIF@CD nanohybrid has been developed. The CoCu-ZIF@CDs-based cytosensor displayed an extremely low limit of detection (LOD) of 33 cells∙mL^-1 within the wide range of B16-F10 cell concentration from 1 × 10² to 1 × 10⁵ cells∙mL^-1, accompanying with cell imaging properties, good selectivity, high stability, and well reproducibility.

Renewable photoelectrochemical cytosensing platform for rapid capture and detection of circulating tumor cells

Determination of circulating tumor cells (CTCs) is crucial for cancer diagnosis and therapy at an early stage. However, extremely low concentration of CTCs in peripheral blood makes the detection of CTCs challenging. In this study, a reusable cytosensor was developed for rapid detection of CTCs based on excellent photoelectrochemical (PEC) characteristic of semiconductor nanoarrays. Using typical breast cancer cell, MCF-7 cell, as a target model, a PEC sensing platform was constructed with polymerized aminophenylboronic acid (APBA) layer coated CdS/ZnO nanorod arrays, exhibiting outstanding performance for the capture and detection of CTCs. In this design, the polymerized APBA provides abundant binding sites for capturing terminal sialic acid (SA) molecules in CTCs. As a result, the PEC cytosensor shows good sensitivity and specificity with concentrations ranging from 50 to 1.0 × 10⁶ cells/mL MCF-7 cells. Moreover, the PEC cytosensor can be rapidly and effectively recovered via a short-time bias triggered cell release and subsequent repair of APBA. This study establishes a new approach to refine a PEC cytosensor for stable monitoring and provides a robust PEC electrode with high sensitivity and low cost for clinical diagnosis related to CTCs.

Recent Advances in Electrochemical Sensors for the Detection of Biomolecules and Whole Cells

Electrochemical sensors are considered an auspicious tool to detect biomolecules (e.g., DNA, proteins, and lipids), which are valuable sources for the early diagnosis of diseases and disorders. Advances in electrochemical sensing platforms have enabled the development of a new type of biosensor, enabling label-free, non-destructive detection of viability, function, and the genetic signature of whole cells. Numerous studies have attempted to enhance both the sensitivity and selectivity of electrochemical sensors, which are the most critical parameters for assessing sensor performance. Various nanomaterials, including metal nanoparticles, carbon nanotubes, graphene and its derivatives, and metal oxide nanoparticles, have been used to improve the electrical conductivity and electrocatalytic properties of working electrodes, increasing sensor sensitivity. Further modifications have been implemented to advance sensor platform selectivity and biocompatibility using biomaterials such as antibodies, aptamers, extracellular matrix (ECM) proteins, and peptide composites. This paper summarizes recent electrochemical sensors designed to detect target biomolecules and animal cells (cancer cells and stem cells). We hope that this review will inspire researchers to increase their efforts to accelerate biosensor progress-enabling a prosperous future in regenerative medicine and the biomedical industry.

Target-triggered "signal-off" electrochemical aptasensor assisted by Au nanoparticle-modified sensing platform for high-sensitivity determination of circulating tumor cells

In this study, we fabricated a high-sensitivity "signal-off" electrochemical aptasensing platform for quantifying circulating tumor cells (CTCs) based on target-triggered signal readout of methylene blue (MB). Au nanoparticles (AuNPs) were introduced to enlarge the specific surface area of the gold electrode (GE), which would immobilize homogeneous and more MB-aptamers. MB-modified and stem-loop-like aptamers were assigned as a recognition element with K562 cells. Thiolated complementary strands hybridized with MB-aptamers to form double-stranded DNA (dsDNA) conformation which were further self-assembled on the surface of AuNP-modified GE, leading to a marked current peak of MB signal. In the presence of K562 cells, the MB-aptamers preferred to recognize and bind with the cells, causing the disassembly of MB-aptamers from the GE surface. Therefore, the reduced value of MB signal was related to the number of K562 cells. With the proposed aptasensor, a dynamic linear range from 1 × 10² to 1 × 10⁶ cells mL^-1 was obtained with a detection limit of 23 cells mL^-1. Moreover, the aptasensor showed good selectivity, stability, and reproducibility as well as potential use in the clinical setting. Meanwhile, characterization techniques such as field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy were performed to analyze the evolution of the morphology and each fabricated step of the constructed aptasensor. Our proposed aptasensor could be designed as a universal platform for CTC determination by replacing tumor cell-specific aptamers, which is a promising strategy for basic research and clinical applications. Graphical abstract.

Detection of Circulating Tumor Cells in Breast Cancer Patients by Nanopore Sensing with Aptamer-Mediated Amplification

Circulating tumor cells (CTCs) have been utilized in the diagnosis and prognosis of tumor. However, the CTC concentration is extremely low to be detected in peripheral blood. Many existing methods suffer from either expensive labeling or complex operation. In this study, we constructed a label- and enzyme-free and sensitive method to detect the breast cancer CTCs. First of all, a probe containing a breast cancer cell-specific aptamer and a complementary single-stranded DNA (trigger DNA P1) were designed. When the target cells are present, the aptamer binds to the CTCs and releases P1 which triggers the strand displacement amplification. This process generates three-way junction structure DNA, the specific translocation signals of which are identified by nanopore assay. The detection limit of tumor cells is 5 in the current experimental setup and can be further reduced. Furthermore, the method is demonstrated in a clinical sample test with high recovery rate and accuracy. Our results suggest that this method could be applied to early diagnosis of metastatic recurrence and prognosis determination.

Electrochemical Nanobiosensors for Detection of Breast Cancer Biomarkers

This comprehensive review paper describes recent advances made in the field of electrochemical nanobiosensors for the detection of breast cancer (BC) biomarkers such as specific genes, microRNA, proteins, circulating tumor cells, BC cell lines, and exosomes or exosome-derived biomarkers. Besides the description of key functional characteristics of electrochemical nanobiosensors, the reader can find basic statistic information about BC incidence and mortality, breast pathology, and current clinically used BC biomarkers. The final part of the review is focused on challenges that need to be addressed in order to apply electrochemical nanobiosensors in a clinical practice.

Application of electrochemical biosensors in tumor cell detection

Conventional methods for detecting tumors, such as immunological methods and histopathological diagnostic techniques, often request high analytical costs, complex operation, long turnaround time, experienced personnel and high false-positive rates. In addition, these assays are difficult to obtain an early diagnosis and prognosis quickly for malignant tumors. Compared with traditional technology, electrochemical technology has realized the study of interface charge transfer behavior at the atomic and molecular levels, which has become an important analytical and detection tool in contemporary analytical science. Electrochemical technique has the advantages of rapid detection, high sensitivity (single cell) and specificity in the detection of tumor cells, which has not only been successful in differentiating tumor cells from normal cells, but has also achieved targeted detection of localized tumor cells and circulating tumor cells. Electrochemical biosensors provide powerful tools for early diagnosis, staging and prognosis of tumors in clinical medicine. Therefore, this review mainly discusses the development and application of electrochemical biosensors in tumor cell detection in recent years.

Nanomaterials in electrochemical cytosensors

Nano-electrochemical cytosensors have attracted intensive attention and achieved huge progress in the biomedical field owing to their stability, rapidity, accuracy, and low-cost properties.

Electrochemical cytosensors for detection of breast cancer cells

Breast cancer is one of lethal cancers among women with its metastasis leading to cancer-related morbidity and mortality. Circulating tumor cells (CTCs) derived from a primary tumor can be detected in the venous blood of cancer patients. Monitoring CTCs in blood samples has increased exponentially over the past decades and holds great promise in the diagnosis and treatment of metastatic breast cancer. Electrochemical cytosensors, classified as a class of electrochemical biosensors for sensitive detection and enumeration of targeted cells with minimally invasive methods, have the advantages of electrochemical biosensors, such as simplicity, low cost, and low limit of detection. Here, we review recent progress in the detection of CTCs from breast cancer with a focus on electrochemical cytosensors. This review describes platforms benefiting from these cytosensors to identify cancerous breast cells. Furthermore, strategies for signal amplification and also generation of reusable electrochemical cytosensors are introduced. In addition, breast cancer markers and biorecognition elements for cell capturing are reviewed.

Photoelectrochemical detection of circulating tumor cells based on aptamer conjugated Cu2O as signal probe

In this work, a sensitive and reliable photoelectrochemical (PEC) biosensor was proposed based on hexagonal carbon nitride tubes (HCNT) as photoactive material for detection of circulating tumor cells (CTCs). Magnetic Fe₃O₄ nanospheres (MNs) and Cu₂O nanoparticles (Cu₂O NPs) were utilized for highly efficient magnetic capture of CTCs and for signal amplification, respectively. First, anti-epithelial cell adhesion molecule (EpCAM) antibody was linked onto MNs for capture and enrichment of CTCs. With the captured MCF-7 coated onto the electrode, the photocurrent intensity of HCNT was decreased due to the steric hindrance derived from MCF-7. Then, when the Cu₂O-aptamer probe was bound onto the CTC surface, the photocurrent intensity was further decreased because Cu₂O NPs competed with HCNT for absorption of exciting light and the aptamer molecules increased the steric hindrance, which leads to significantly decreased photocurrent response, thus realizing dual signal amplification. Using the breast cancer cell MCF-7 as a model, the proposed PEC biosensor displays good performances with a linear range from 3 to 3000 cell mL^-1 and limit of detection down to 1 cell mL^-1. The HCNT-based PEC biosensor shows good performance for detection of CTCs, which may have potential applications in cancer diagnostics and therapeutics.

Nanomaterials for Healthcare Biosensing Applications

In recent years, an increasing number of nanomaterials have been explored for their applications in biomedical diagnostics, making their applications in healthcare biosensing a rapidly evolving field. Nanomaterials introduce versatility to the sensing platforms and may even allow mobility between different detection mechanisms. The prospect of a combination of different nanomaterials allows an exploitation of their synergistic additive and novel properties for sensor development. This paper covers more than 290 research works since 2015, elaborating the diverse roles played by various nanomaterials in the biosensing field. Hence, we provide a comprehensive review of the healthcare sensing applications of nanomaterials, covering carbon allotrope-based, inorganic, and organic nanomaterials. These sensing systems are able to detect a wide variety of clinically relevant molecules, like nucleic acids, viruses, bacteria, cancer antigens, pharmaceuticals and narcotic drugs, toxins, contaminants, as well as entire cells in various sensing media, ranging from buffers to more complex environments such as urine, blood or sputum. Thus, the latest advancements reviewed in this paper hold tremendous potential for the application of nanomaterials in the early screening of diseases and point-of-care testing.

An electrochemical aptasensor for analysis of MUC1 using gold platinum bimetallic nanoparticles deposited carboxylated graphene oxide

A simple electrochemical strategy has been designed for the analysis of MUC1 using electrodeposited gold platinum bimetallic nanoparticles (Au-PtBNPs) on the surface of carboxylated graphene oxide (CGO)/FTO electrode as a signal amplification platform. The carboxylic groups of CGO were activated with EDS-NHS linker and subsequently immobilized with streptavidin for further deposition of biotin labelled aptamer. All the modification steps were characterized by FE-SEM, EDS mapping, FT-IR, contact angle measurements and electrochemical methods. After incubating with target protein MUC1, the aptaelectrode produced some concentration dependent responses which were measured electrochemically by DPV assay. The prepared aptasensor exhibits wide linear range from 1 fM-100 nM with detection limit of 0.79 fM under optimal experimental conditions. The performance of this aptaelectrode was also evaluated showing good selectivity, storage stability (15 days), reproducibility and reusability (up to 3 times). Furthermore, the applicability of the aptasensor for spiked serum samples showed recovery range from 92% to 97%.

Construction of Tb-MOF-on-Fe-MOF conjugate as a novel platform for ultrasensitive detection of carbohydrate antigen 125 and living cancer cells

Combining different metal-organic frameworks (MOFs) into a conjugate material can integrate the properties of each MOF component and further lead to emergent properties from the synergistic heterostructured units. In this work, two kinds of bimetallic TbFe-MOFs have been designed by MOF-on-MOF strategy and utilized as a platform for anchoring carbohydrate antigen 125 (CA125) aptamer to detect CA125 and living michigan cancer foundation-7 (MCF-7) cells. Although the integrated MOF-on-MOF architectures show similar chemical and structural features to that of the top layer, the Fe-MOF-on-Tb-MOF and Tb-MOF-on-Fe-MOF have different surface nanostructures to their parent MOFs. The developed aptasensor based on Tb-MOF-on-Fe-MOF displays higher stability of the formed G-quadruplex between aptamer and CA125 than that based on Fe-MOF-on-Tb-MOF, owing to stronger immobilization behavior of the aptamer for the Tb-MOF-on-Fe-MOF composite. The developed aptasensor provides an extremely low detection limit of 58 μU·mL^-1 towards CA125 within a wide linear range from 100 μU·mL^-1 to 200 U·mL^-1, which is significantly lower than those of all reported sensors. This aptasensor also has high selectivity, good stability, acceptable reproducibility, and excellent applicability in human serum. Moreover, the Tb-MOF-on-Fe-MOF nanoarchitecture demonstrates superior biocompatibility and good endocytosis. As a result, the developed aptasensor illustrates high sensitivity for detection of MCF-7 cells with an extremely low detection limit of 19 cell·mL^-1. Therefore, the proposed aptasensor based on Tb-MOF-on-Fe-MOF exhibits great potentials for early diagnosis of tumors.

Direct Plasmon-Enhanced Electrochemistry for Enabling Ultrasensitive and Label-Free Detection of Circulating Tumor Cells in Blood

In this work, we developed a simple electrochemical method for ultrasensitive and label-free detection of circulating tumor cells (CTCs) based on direct plasmon-enhanced electrochemistry (DPEE). After plasmonic gold nanostars (AuNSs) were modified on the glassy carbon (GC) electrode, the aptamer probe was immobilized on the AuNSs surface, which can selectively capture the CTCs in samples. Upon localized surface plasmon resonance (LSPR) excitation, the electrochemical current response can be enhanced remarkably due to efficient hot electrons transport from AuNSs to the external circuit. The captured cells on the AuNSs surface will influence the hot electrons transport efficiency, leading to a decreased current response. Using ascorbic acid (AA) as the electroactive probe, it was found that the current responses of the AuNSs/GC electrode upon light irradiation decrease with the cell concentration. Due to the special molecular recognition of the aptamer and enhanced electrochemical performance of the plasmon, the proposed method enables an ultrasensitive and label-free detection of CTCs with excellent selectivity. The experimental results show that CCRF-CEM cell concentrations as low as 5 cells/mL can be successfully detected, which is superior to most reported work up to now. Using the present method, MCF-7 cells as low as 10 cells/mL can be also successfully detected, indicating the universality of the proposed method for CTCs detection. Furthermore, the cytosensor can successfully distinguish CTCs from normal cells in blood samples. The as-proposed strategy provides a promising application of DPEE in the development of novel biosensors for nondestructive analysis of biological samples.