Ultrasensitive detection of cancer cells and glycan expression profiling based on a multivalent recognition and alkaline phosphatase-responsive electrogenerated chemiluminescence biosensor

Harnessing aptamers for the biosensing of cell surface glycans - A review

Cell surface glycans (CSGs) are essential for cell recognition, adhesion, and invasion, and they also serve as disease biomarkers. Traditional CSG recognition using lectins has limitations such as limited specificity, low stability, high cytotoxicity, and multivalent binding. Aptamers, known for their specific binding capacity to target molecules, are increasingly being employed in the biosensing of CSGs. Aptamers offer the advantage of high flexibility, small size, straightforward modification, and monovalent recognition, enabling their integration into the profiling of CSGs on living cells. In this review, we summarize representative examples of aptamer-based CSG biosensing and identify two strategies for harnessing aptamers in CSG detection: direct recognition based on aptamer-CSG binding and indirect recognition through protein localization. These strategies enable the generation of diverse signals including fluorescence, electrochemical, photoacoustic, and electrochemiluminescence signals for CSG detection. The advantages, challenges, and future perspectives of using aptamers for CSG biosensing are also discussed.

An electrochemiluminescence resonance energy transfer biosensor based on CDs/PAMAM/rGO nanocomposites and Au@Ag2S nanoparticles for PML/RARα fusion gene detection

In recent years, electrochemiluminescence resonance energy transfer (ECL-RET) with low background signal and high specificity has attracted much attention among researchers. Herein, we established a novel ECL-RET biosensor for PML/RARα fusion gene detection. In this ECL-RET system, carbon dots (CDs) with low toxicity and prominent electrochemical activity were used as donor and Au@Ag2S core-shell nanoparticles (Au@Ag2S NPs) were employed as ECL acceptor. The Au@Ag2S NPs possessed a wide ultraviolet-visible (UV-vis) absorption spectrum between 500 nm and 700 nm, which completely overlapped with the ECL spectrum of CDs. Furthermore, the CDs-decorated poly-amidoamine/reduced graphene oxide (CDs/PAMAM/rGO) nanocomposites were prepared to improve the ECL signals and served as a substrate to stably load capture probe deoxyribonucleic acid (DNA). Based on the ECL-RET biosensing strategy, the Au@Ag2S NPs-labeled assistant probes and target DNA could pair with capture probes to form the sandwich-type DNA structure and the distance between donor and accepter was closed, leading to quenching of the ECL signal of CDs. The ECL-RET biosensor represented eminent analytical performance for PML/RARα fusion gene detection with a wide linear relationship from 5 fM to 500 pM and a low detection limit of 0.72 fM, which provided a novel technical means and theoretical basis for detection and diagnosis of acute promyelocytic leukemia.

Enzyme-Free Autocatalysis-Driven Feedback DNA Circuits for Amplified Aptasensing of Living Cells

Aptasensors with high specificity have emerged as powerful tools for understanding various biological processes, thus providing tremendous opportunities for clinical diagnosis and prognosis. However, their applications in intracellular molecular imaging are largely impeded due to the low anti-interference capacity in biological environments and the moderate sensitivity to targets. Herein, a robust enzyme-free autocatalysis-driven feedback DNA circuit is devised for amplified aptasensing, for example, adenosine triphosphate (ATP) and thrombin, with a significantly improved sensitivity in living cells. This initiator-replicated hybridization chain reaction (ID-HCR) circuit was acquired by integrating the HCR circuit with the DNAzyme biocatalysis. Also, the autocatalysis-driven aptasensor consists of a recognition element and an amplification element. The recognition unit can specifically identify ATP or thrombin via a versatile conformational transformation, resulting in the exposure of the initiator to the autocatalysis-driven circuit. The ID-HCR element integrates the charming self-assembly characteristics of the HCR and the remarkable catalytic cleavage capacity of DNAzyme for realizing the continuously self-sustained regeneration or replication of trigger strands and for achieving an exponential signal gain. The autocatalysis-driven aptasensor has been validated for quantitative analysis of ATP and thrombin in vitro and for monitoring the corresponding aptamer substrates with various expressions in live cells. More importantly, the autocatalysis-driven aptasensor, as a versatile amplification strategy, holds enormous potential for analysis of other less abundant biomarkers by changing only the recognition element of the system.

Recent Development of Nanomaterials-Based Cytosensors for the Detection of Circulating Tumor Cells

The accurate analysis of circulating tumor cells (CTCs) holds great promise in early diagnosis and prognosis of cancers. However, the extremely low abundance of CTCs in peripheral blood samples limits the practical utility of the traditional methods for CTCs detection. Thus, novel and powerful strategies have been proposed for sensitive detection of CTCs. In particular, nanomaterials with exceptional physical and chemical properties have been used to fabricate cytosensors for amplifying the signal and enhancing the sensitivity. In this review, we summarize the recent development of nanomaterials-based optical and electrochemical analytical techniques for CTCs detection, including fluorescence, colorimetry, surface-enhanced Raman scattering, chemiluminescence, electrochemistry, electrochemiluminescence, photoelectrochemistry and so on.

A novel nucleic acid amplification system based on nano-gap embedded active disk resonators

Recent advances in nucleic acid based testing using bio-optical sensor approaches have been introduced but most are based on hybridization between the optical sensor and the bio-molecule and not on an amplification mechanism. Direct nucleic acid amplification on an optical sensor has several technical limitations, such as the sensitivity of the temperature sensor, instrument complexity, and high background signal. We here describe a novel nucleic acid amplification method based on a whispering gallery mode active resonator and discuss its potential molecular diagnostic application. By implanting nanoclusters as active compounds, this active resonator operates without tapered fiber coupling and emits a strong photoluminescence signal with low background in the wavelength of low absorption in an aqueous environment that is typical of biosensors. Our method also offers an extremely low detection threshold down to a single copy within 10 min due to the strong light-matter interaction in a nano-gap structure. We envision that this active resonator provides a high refractive index contrast for tight mode confinement with simple alignment as well as the possibility of reducing the device size so that a point-of-care system with low-cost, high-sensitivity and simplicity.

Recent Advances in Electrochemiluminescence-Based Systems for Mammalian Cell Analysis

Mammalian cell analysis is essential in the context of both fundamental studies and clinical applications. Among the various techniques available for cell analysis, electrochemiluminescence (ECL) has attracted significant attention due to its integration of both electrochemical and spectroscopic methods. In this review, we summarize recent advances in the ECL-based systems developed for mammalian cell analysis. The review begins with a summary of the developments in luminophores that opened the door to ECL applications for biological samples. Secondly, ECL-based imaging systems are introduced as an emerging technique to visualize single-cell morphologies and intracellular molecules. In the subsequent section, the ECL sensors developed in the past decade are summarized, the use of which made the highly sensitive detection of cell-derived molecules possible. Although ECL immunoassays are well developed in terms of commercial use, the sensing of biomolecules at a single-cell level remains a challenge. Emphasis is therefore placed on ECL sensors that directly detect cellular molecules from small portions of cells or even single cells. Finally, the development of bipolar electrode devices for ECL cell assays is introduced. To conclude, the direction of research in this field and its application prospects are described.

Ultrasensitive and Label-Free Detection of Cell Surface Glycan Using Nanochannel-Ionchannel Hybrid Coupled with Electrochemical Detector

In this work, asymmetric nanochannel-ionchannel of porous anodic alumina (PAA) coupled with electrochemical detector was used for sensitive and label-free detection of cell surface glycan. The amplified ionic current caused by array nanochannels as well as the ionic current rectification (ICR) caused by asymmetric geometry endows PAA with sensitive ionic current response. Functionalized with the special molecular probe, the constructed nanofluidic device can be used for selective recognition and detection of glycan in a real-time and label-free format. In addition, due to the subnanosize of ionchannels, the probe immobilization and glycan recognition is carried out on the outer surface of PAA, avoiding the blockage of PAA nanochannel by samples, which promises the reproducibility and accuracy of the present method toward bioanalysis. Results show that the glycan concentration ranging from 10 fM to 10 nM can be successfully detected with a detection limit of ∼10 aM, which is substantially lower than most previous works. The designed strategy provides a valuable platform for sensitive and label-free detection of cell surface glycan, which acts as a promising candidate in pathological research and cancer diagnosis.

Recent Progress of Biomarker Detection Sensors

Early cancer diagnosis and treatment are crucial research fields of human health. One method that has proven efficient is biomarker detection which can provide real-time and accurate biological information for early diagnosis. This review presents several biomarker sensors based on electrochemistry, surface plasmon resonance (SPR), nanowires, other nanostructures, and, most recently, metamaterials which have also shown their mechanisms and prospects in application in recent years. Compared with previous reviews, electrochemistry-based biomarker sensors have been classified into three strategies according to their optimizing methods in this review. This makes it more convenient for researchers to find a specific fabrication method to improve the performance of their sensors. Besides that, as microfabrication technologies have improved and novel materials are explored, some novel biomarker sensors-such as nanowire-based and metamaterial-based biomarker sensors-have also been investigated and summarized in this review, which can exhibit ultrahigh resolution, sensitivity, and limit of detection (LoD) in a more complex detection environment. The purpose of this review is to understand the present by reviewing the past. Researchers can break through bottlenecks of existing biomarker sensors by reviewing previous works and finally meet the various complex detection needs for the early diagnosis of human cancer.

Aptamer-based electrochemical cytosensors for tumor cell detection in cancer diagnosis: A review

Circulating tumor cells, a type of viable cancer cell circulating from primary or metastatic tumors in the blood stream, can lead to the parallel development of primary tumors and metastatic lesions. Highly selective and sensitive detection of tumor cells has become a hot research topic and can provide a basis for early diagnosis of cancers and anticancer drug evaluation to develop the best treatment plan. Aptamers are single-stranded oligonucleotides that can bind to target tumor cells in unique three-dimensional structures with high specificity and affinity. Aptamer-based methods or signal amplification methods using aptamers show great potential in improving the selectivity and sensitivity of electrochemical (EC) cytosensors for tumor cell detection. This review covers the remarkable developments in aptamer-based EC cytosensors for the identification of cell type, cell counting and detection of crucial proteins on the cell surface. Various EC techniques have been developed for cancer cell detection, including common voltammetry or impedance, electrochemiluminescence and photoelectrochemistry in a direct approach (aptamer-target cell), sandwich approach (capture probe-target cell-signaling probe) or other approach. The current challenges and promising opportunities in the establishment of EC aptamer cytosensors for tumor cell detection are also discussed.

Nanoscale Nucleic Acid Recognition at the Solid-Liquid Interface Using Xeno Nucleic Acid Probes

Challenges in reliable nucleic acid detection are manifold. The major ones are related to false positive or negative signals due to a lack of target specificity in detection and to low sensitivity, especially when a plethora of background sequences are present that can mask the specific recognition signal. Utilizing designed synthetic nucleic acids that are commonly called xeno nucleic acids could offer potential routes to meeting such challenges. In this article, we present the general framework of nucleic acid detection, especially for nanoscale applications, and discuss how and why the xeno nucleic acids could be truly an alternative to the DNA probes. Two specific cases, locked nucleic acid (LNA) and peptide nucleic acid (PNA), which are nuclease-resistant and can form thermally stable duplexes with DNA, are addressed. It is shown that the relative ease of the conformationally rigid LNA probe to be oriented upright on the substrate surface and of the nonionic PNA probe to result into high probe density assists in their use in nanoscale nucleic acid recognition. It is anticipated that success with these probes may lead to important developments such as PCR-independent approaches where the major aim is to detect a small number of target sequences present in the analyte medium.

Aggregation-induced emission fluorescent probe for monitoring endogenous alkaline phosphatase in living cells

Alkaline phosphatase (ALP) is a non-specific phosphate monoesterase and often regarded as an important biomarker of hypothyroidism and hepatobiliary diseases in medical diagnosis. In-situ detection of endogenous ALP and exploration of the distribution of ALP in cells are of great importance for the diagnosis of diseases associated with ALP. In this work, we designed and synthesized an aggregation-induced emission (AIE) fluorescent probe, (E)-2-(((9H-fluoren-9-ylidene) hydrazono)methyl)phenyl dihydrogen phosphate (FAS-P), that can respond to ALP with a remarkable large Stokes shift (>200 nm) based on excited state intramolecular proton transfer (ESIPT) mechanism. The probe FAS-P has high selectivity and sensitivity to the detection of ALP. And there is a linear relationship between the fluorescence intensity of FAS-P and ALP activity in the range of 1-100 U L^-1, the limit of detection (LOD) is as low as 0.6 U L^-1. More importantly, we successfully applied FAS-P to detect ALP in living cells and the monitoring of ALP in real time.

A rational strategy to develop a boron nitride quantum dot-based molecular logic gate and fluorescent assay of alkaline phosphatase activity

By comparing the percentage of FL quenching and recovery of the BNQDs, a Fe³⁺-mediated FL quenching of BNQDs system was rationally designed for efficient ALP assay. Moreover, the aforementioned ensemble was exploited to newly construct a 2D-QD-based INH logic gate.

An Aptamer-Based Capacitive Sensing Platform for Specific Detection of Lung Carcinoma Cells in the Microfluidic Chip

Improvement of methods for reliable and early diagnosis of the cellular diseases is necessary. A biological selectivity probe, such as an aptamer, is one of the candidate recognition layers that can be used to detect important biomolecules. Lung cancer is currently a typical cause of cancer-related deaths. In this work, an electrical sensing platform is built based on amine-terminated aptamer modified-gold electrodes for the specific, label-free detection of a human lung carcinoma cell line (A549). The microdevice, that includes a coplanar electrodes configuration and a simple microfluidic channel on a glass substrate, is fabricated using standard photolithography and cast molding techniques. A procedure of self-assembly onto the gold surface is proposed. Optical microscope observations and electrical impedance spectroscopy measurements confirm that the fabricated microchip can specifically and effectively identify A549 cells. In the experiments, the capacitance element that is dominant in the change of the impedance is calculated at the appropriate frequency for evaluation of the sensitivity of the biosensor. Therefore, a simple, inexpensive, biocompatible, and selective biosensor that has the potential to detect early-stage lung cancer would be developed.

Multifunctional solid-state electrochemiluminescent chemosensors and aptasensor with free-standing active sites based on task-specific pyrene-terminated polymers via RAFT polymerization

Based on the flexible molecular engineering technique of reversible addition-fragmentation chain transfer (RAFT) polymerization, various polymers carrying positive or negative charges and different terminal groups such as pyrene or tertiary amine were synthesized for fabricating multifunctional solid-state electrochemiluminescent (ECL) sensors. Accordingly, the chemosensors immobilizing the ECL probe or co-immobilizing the ECL probe and the coreactant were realized for the quantification of small molecules (e.g., tripropylamine, tetracycline), and an aptasensor was developed for the specific and sensitive lysozyme assay (limit of detection: 0.1 ng/mL). All of the sensors were realized via a simple design exploiting the π-π stacking and electrostatic interactions. It was confirmed that the proposed strategy is simple but universal for the fabrication of versatile ECL sensors that showed simplicity, cost-effectiveness, high sensitivity, long-term stability, and excellent reproducibility.

Graphitic-phase carbon nitride-based electrochemiluminescence sensing analyses: recent advances and perspectives

This review describes the current trends in synthesis methods, signaling strategies, and sensing applications of g-C₃N₄-based ECL emitters.

Flow injection amperometric sandwich-type aptasensor for the determination of human leukemic lymphoblast cancer cells using MWCNTs-Pdnano/PTCA/aptamer as labeled aptamer for the signal amplification

In this research, we demonstrated a flow injection amperometric sandwich-type aptasensor for the determination of human leukemic lymphoblasts (CCRF-CEM) based on poly(3,4-ethylenedioxythiophene) decorated with gold nanoparticles (PEDOT-Au_nano) as a nano platform to immobilize thiolated sgc8c aptamer and multiwall carbon nanotubes decorated with palladium nanoparticles/3,4,9,10-perylene tetracarboxylic acid (MWCNTs-Pd_nano/PTCA) to fabricate catalytic labeled aptamer. In the proposed sensing strategy, the CCRF-CEM cancer cells were sandwiched between immobilized sgc8c aptamer on PEDOT-Au_nano modified surface electrode and catalytic labeled sgc8c aptamer (MWCNTs-Pd_nano/PTCA/aptamer). After that, the concentration of CCRF-CEM cancer cells was determined in presence of 0.1 mM hydrogen peroxide (H₂O₂) as an electroactive component. The attached MWCNTs-Pd_nano nanocomposites to CCRF-CEM cancer cells amplified the electrocatalytic reduction of H₂O₂ and improved the sensitivity of the sensor to CCRF-CEM cancer cells. The MWCNT-Pd_nano nanocomposite was characterized with transmission electron microscopy (TEM) and energy dispersive X-ray (EDX). The electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to confirm the stepwise changes in the electrochemical surface properties of the electrode. The proposed sandwich-type electrochemical aptasensor exhibited an excellent analytical performance for the detection of CCRF-CEM cancer cells ranging from 1.0 × 10¹ to 5.0 × 10⁵ cells mL^-1. The limit of detection was 8 cells mL^-1. The proposed aptasensor showed high selectivity toward CCRF-CEM cancer cells. The proposed aptasensor was also applied to the determination of CCRF-CEM cancer cells in human serum samples.

Ultrasensitive Photoelectrochemical Biosensing of Cell Surface N-Glycan Expression Based on the Enhancement of Nanogold-Assembled Mesoporous Silica Amplified by Graphene Quantum Dots and Hybridization Chain Reaction

An ultrasensitive photoelectrochemical (PEC) biosensor for N-glycan expression based on the enhancement of nanogold-assembled mesoporous silica nanoparticles (GMSNs) was fabricated, which also combined with multibranched hybridization chain reaction (mHCR) and graphene quantum dots (GQDs). In this work, the localized surface plasmon resonance, mHCR and GQDs-induced signal amplification strategies were integrated exquisitely and applied sufficiently. In the fabrication, after porous ZnO spheres immobilized on the Au nanorod-modified paper working electrode were sensitized by CdTe QDs, the GMSNs were assembled on the CdTe QDs. Then the photocurrent efficiency was improved by the sensitization of the CdTe QDs and the localized surface plasmon resonance of GMSNs. Successively, the products of mHCR with multiple biotins for multiple horseradish peroxidase binding and multiple branched arms for capturing the target cells were attached on the as-prepared electrode. The chemiluminescent (CL) emission with the aid of horseradish peroxidase served as an inner light source to excite photoactive materials for simplifying the instrument. Furthermore, the aptamer could capture the cancer cells by its highly efficient cell recognition ability, which avoided the conventional routing cell counting procedures. Meanwhile, the GQDs served as the signal amplication strategy, which was exerted in the process of N-glycan evaluation because the competitive absorption of exciting light and consumption of H₂O₂ served as the electron donor of the PEC system and the oxidant of the luminol-based CL system. This judiciously engineered biosensor offered a promising platform for the exploration of N-glycan-based physiological processes.

Simultaneous fluorescence analysis of the different carbohydrates expressed on living cell surfaces using functionalized quantum dots

The aberrant expression of carbohydrates has been associated with the occurrence, growth, progression and metastasis of tumors.

A label-free and high-efficient GO-based aptasensor for cancer cells based on cyclic enzymatic signal amplification

A label-free and high-efficient graphene oxide (GO)-based aptasensor was developed for the detection of low quantity cancer cells based on cell-triggered cyclic enzymatic signal amplification (CTCESA). In the absence of target cells, hairpin aptamer probes (HAPs) and dye-labeled linker DNAs stably coexisted in solution, and the fluorescence was quenched by the GO-based FÖrster resonance energy transfer (FRET) process. In the presence of target cells, the specific binding of HAPs with the target cells triggered a conformational alternation, which resulted in linker DNA complementary pairing and cleavage by nicking endonuclease-strand scission cycles. Consequently, more cleaved fragments of linker DNAs with more the terminal labeled dyes could show the enhanced fluorescence because these cleaved DNA fragments hardly combine with GOs and prevent the FRET process. Fluorescence analysis demonstrated that this GO-based aptasensor exhibited selective and sensitive response to the presence of target CCRF-CEM cells in the concentration range from 50 to 10⁵ cells. The detection limit of this method was 25 cells, which was approximately 20 times lower than the detection limit of normal fluorescence aptasensors without amplification. With high sensitivity and specificity, it provided a simple and cost-effective approach for early cancer diagnosis.

Rapid biosensing tools for cancer biomarkers

The present review critically discusses the latest developments in the field of smart diagnostic systems for cancer biomarkers. A wide coverage of recent biosensing approaches involving aptamers, enzymes, DNA probes, fluorescent probes, interacting proteins and antibodies in vicinity to transducers such as electrochemical, optical and piezoelectric is presented. Recent advanced developments in biosensing approaches for cancer biomarker owes much credit to functionalized nanomaterials due to their unique opto-electronic properties and enhanced surface to volume ratio. Biosensing methods for a plenty of cancer biomarkers has been summarized emphasizing the key principles involved.

Aptamers: versatile molecular recognition probes for cancer detection

In the past two decades, aptamers have emerged as a novel class of molecular recognition probes comprising uniquely-folded short RNA or single-stranded DNA oligonucleotides that bind to their cognate targets with high specificity and affinity. Aptamers, often referred to as "chemical antibodies", possess several highly desirable features for clinical use. They can be chemically synthesized and are easily conjugated to a wide range of reporters for different applications, and are able to rapidly penetrate tissues. These advantages significantly enhance their clinical applicability, and render them excellent alternatives to antibody-based probes in cancer diagnostics and therapeutics. Aptamer probes based on fluorescence, colorimetry, magnetism, electrochemistry, and in conjunction with nanomaterials (e.g., nanoparticles, quantum dots, single-walled carbon nanotubes, and magnetic nanoparticles) have provided novel ultrasensitive cancer diagnostic strategies and assays. Furthermore, promising aptamer targeted-multimodal tumor imaging probes have been recently developed in conjunction with fluorescence, positron emission tomography (PET), single-photon emission computed tomography (SPECT), and magnetic resonance imaging (MRI). The capabilities of the aptamer-based platforms described herein underscore the great potential they hold for the future of cancer detection. In this review, we highlight the most prominent recent developments in this rapidly advancing field.

A polydopamine nanosphere based highly sensitive and selective aptamer cytosensor with enzyme amplification

With CCRF-CEM as the model cell, a highly sensitive and selective cytosensor was developed by taking advantage of polydopamine nanospheres for the first time. The strategies of aptamer/membrane protein recognition and Exonuclease III assisted cycle amplification were used for improving selectivity and sensitivity. The detection of limit reached was as low as 15 cells per mL.

Reusable and dual-potential responses electrogenerated chemiluminescence biosensor for synchronously cytosensing and dynamic cell surface N-glycan evaluation

A novel reusable and dual-potential responsive electrogenerated chemiluminescence (ECL) biosensor was fabricated for synchronous detection of cancer cells and their surface N-glycan. In this strategy, a cancer cell recognized aptamer hybridized with a capture DNA was immobilized on electrochemically reduced MoS2 nanosheets, and Ru(phen)3(2+) as ECL probes was intercalated into the grooves of the double-strand DNA. In the presence of target cells, the capture DNA and Ru(phen)3(2+) were released from the electrode interface owing to the specific interaction between cancer cells and the aptamer. Meanwhile, concanavalin A (Con A), a mannose binding protein, and a conjugated gold nanoparticle modified graphite-C3N4 (Con A@Au-C3N4) was used as a negative ECL nanoprobe and applied for the cell surface N-glycan evaluation owing to the excellent ECL properties of g-C3N4 at negative potential. The cytosensing and cell surface N-glycan evaluation could be simultaneously realized with high sensitivity and excellent selectivity based on the ratio of ECL intensity between the negative potential and positive potential (ΔECLn/ΔECLp), avoiding the traditional routing cell counting procedures. Moreover, the aptamer modified electrode can be regenerated in the presence of capture DNA solutions for cyclic utilization. As a proof-of-concept, the ECL cytosensor showed excellent performances for the analysis of the MCF-7 cancer cell and its surface N-glycan evaluation in human serum samples. The reusable and dual potential response ECL biosensor endows a feasibility tool for clinical diagnosis and drug screening especially in complex biological systems.

Ultrasensitive detection of drug resistant cancer cells in biological matrixes using an amperometric nanobiosensor

Multidrug resistance (MDR) is a key issue in the failure of cancer chemotherapy and its detection will be helpful to develop suitable therapeutic strategies for cancer patients and overcome the death rates. In this direction, we designed a new amperometric sensor (a medical device prototype) to detect drug resistant cancer cells by sensing "Permeability glycoprotein (P-gp)". The sensor probe is fabricated by immobilizing monoclonal P-gp antibody on the gold nanoparticles (AuNPs) conducting polymer composite. The detection relies on a sandwich-type approach using a bioconjugate, where the aminophenyl boronic acid (APBA) served as a recognition molecule which binds with the cell surface glycans and hydrazine (Hyd) served as an electrocatalyst for the reduction of H2O2 which are attached on multi-wall carbon nanotube (MWCNT) (APBA-MWCNT-Hyd). A linear range for the cancer cell detection is obtained between 50 and 100,000 cells/mL with the detection limit of 23±2 cells/mL. The proposed immunosensor is successfully applied to detect MDR cancer cells (MDRCC) in serum and mixed cell samples. Interferences by drug sensitive (SKBr-3 and HeLa), noncancerous cells (HEK-293 and OSE), and other chemical molecules present in the real sample matrix are examined. The sensitivity of the proposed immunosensor is excellent compared with the conventional reporter antibody based assay.