Ultrasensitive Detection Of Carcinoembryonic Antigen Research Articles

Development and performance assessment of a multi-walled carbon nanotube/iron oxide nanocomposite-based electrochemical immunosensor for precise and ultrasensitive detection of carcinoembryonic antigen

Development and performance assessment of a multi-walled carbon nanotube/iron oxide nanocomposite-based electrochemical immunosensor for precise and ultrasensitive detection of carcinoembryonic antigen

A dual-model immobilization-free photoelectrochemical/visual colorimetric bioanalysis based on microemulsion self-assemblies mediated multifunctional signal amplification strategy

Herein, a novel silver ion-loaded gold microemulsion assemblies (Au/Ag+ MAs) mediated multifunctional signal amplification strategy was proposed to construct a sensitive immobilization-free photoelectrochemical (PEC)/colorimetric biosensor for carcinoembryonic antigen (CEA) detection. Through the sandwiched reaction among CEA, the CEA aptamer (DNA1) loaded on the Au nanoparticles (NPs) functionalized iron oxide (Fe3O4) nanospheres and another CEA aptamer (DNA2) immobilized on Au/Ag+ MAs, a complex is formed and acquired by magnetic separation. Then, Au/Ag+ MAs of the complex are disassembled into Au NPs and Ag+ ions driven by an acetone response, and the obtained demulsification solution is transferred to the cadmium sulfide/cadmium telluride (CdS/CdTe) photoactive composites modified electrode. Based on the multiple inhibition functions (blocking effect of oleylamine; energy transfer effect of Au NPs; and electron snatching effect of Ag+), the photocurrent of the electrode decreases obviously, resulting in the ultrasensitive detection of CEA (a detection limit of 16 fg mL−1). Interestingly, the ion-exchange reactions between CdS/CdTe composites and Ag+ ions generate silver sulfide/silver telluride (Ag2S/Ag2Te) composites, and a color change of composites can be distinguished directly, leading to a quick visual detection of CEA. Compared with the traditional single-modal assay for CEA, such dual-modal PEC/colorimetric assay is a more accurate and reliable due to different mechanisms and independent signal conversion. This work will offer a new perspective for the applications of various self-assemblies in PEC bioanalysis.

Pt Nanodot Inlaid Mesoporous NaBiOF Nanoblackberry for Remarkable Signal Amplification Toward Biomarker Detection.

Anew ultrasensitive sandwich-type electrochemical immunosensor has been successfully constructedto quantitatively detect carcinoembryonic antigen (CEA) using blackberry-like mesoporous bismuth-based nanospheres NaBiOF (NBOF NSs) inlaid with Pt nanodots (NDs) (BiPt NSs) as the antibody capture and signal-amplifying probe. The growth of Pt NDs inside the holes of NBOF NSs formed the nanozyme inlay outside NBOF NSs, greatly increasing the specific surface area and exposure of the catalytic active sites by minimizing the particle size of the Pt to nanodot scale. Such a blackberry-shaped heterojunction structure of BiPt NSs was well-suited to antibody capture and improvedthe catalytic performance of BiPt NSs in reducing H2O2, amplifying the signal, and yielding highly sensitive detection of CEA. Theuse of Au nanoparticle-modified multi-walled carbon nanotubes (Au@MWCNTs) as the electrode substrates significantly enhanced the electron transfer behavior over the electrode surface, further increasing the conductivity and sensitivity of the immunosensor. Remarkably, good compatibility with human body fluid was achieved using the newly developed BiPt-based immunosensor resulting from the favorable biocompatibility and stability of both BiPt NSs and Au@MWCNTs. Benefiting from the double signal amplification strategy and the high biocompatibility, the immunosensor responded linearly to CEA in a wide range from 50 fg/mL to 100 ng/ml with an extremely low detection limit of 3.52 fg/mL (S/N = 3). The excellent detection properties of this new immunosensor were evidenced by the satisfactory selectivity, reproducibility, and stability obtained, as well as the reliable and precise determination of CEA in actual human blood samples. This work provides a new strategy for the earlyclinical diagnosis of cancer. Novel blackberry-like mesoporous NaBiOF nanospheres with Pt nanodot inlay were successfully usedto construct a sandwich-type electrochemical immunosensor for the ultra-sensitive detection ofcarcinoembryonic antigen in human blood plasma based on a remarkable signal amplification strategy.

Ultrasensitive detection of carcinoembryonic antigen based on exonuclease Ⅲ-assisted recycling and hybridization chain reaction strategies

In this work, we developed a novel ratiometric electrochemical aptasensor for the sensitive detection of carcinoembryonic antigen (CEA). Upon the addition of CEA, the specific binding between CEA and hairpin probe 1 (HP1) could trigger the Exo Ⅲ cleavage reaction and release large amounts of single stranded DNA (S1), which then hybridized with thiolated ferrocene-labeled hairpin probe 3 (Fc-HP3) on the electrode surface. Exo Ⅲ then cyclically digested the resulting duplexes to generate Fc-HP3 fragments on the electrode, accompanying the Fc molecules far away from the electrode surface and the Fc oxidation peak current signal (IFc) decreased. The HCR process was triggered by the Fc-HP3 fragment as an initiator, producing many long DNA sequences for electroactive probe methylene blue (MB) intercalation; thus, the MB oxidation peak current signal (IMB) increased. The IMB/IFc ratio was proportional to the logarithm value of CEA concentration from 100 fg mL−1 to 50 ng mL−1, with a lower detection limit of 30.5 fg mL−1. Furthermore, the aptasensor exhibited good selectivity and stability, with satisfactory reproducibility. Additionally, the developed aptasensor effectively measured CEA in real serum samples, verifying its practical application in biological samples.

Electrochemiluminescent immunosensor for detection of carcinoembryonic antigen using luminol-coated silver nanoparticles

Recently, electrochemiluminescent (ECL) immunosensors have received muchattention in the field of biomarker detection. Here, a highly enhanced ECL immunosensing platform was designed for ultrasensitive detection of carcinoembryonic antigen (CEA). The surface of the glassy carbon electrode was enhanced by applying functional nanostructures such as thiolated graphene oxide (S-GO) and streptavidin-coated gold nanoparticles (SA-AuNPs). The selectivity and sensitivity of the designed immunosensor were improved by entrapping CEA biomolecules using a sandwich approach. Luminol/silver nanoparticles (Lu-SNPs) were applied as the main core of the signaling probe, which were then coated with streptavidin to provide overloading of the secondary antibody. The highly ECL signal enhancement was obtained due to the presence of horseradish peroxidase (HRP) in the signaling probe, in which the presence of H2O2 further amplified the intensity of the signals. The engineered immunosensor presented excellent sensitivity for CEA detection, with limitof detection (LOD) and linear detection range (LDR) values of 58fgmL-1 and 0.1pgmL-1 to 5pgmL-1 (R2 = 0.9944), respectively. Besides its sensitivity, the fabricated ECL immunosensor presented outstanding selectivity for the detection of CEA in the presence of various similar agents. Additionally, the developed immunosensor showed an appropriate repeatability (RSD 3.8%) and proper stability (2weeks). Having indicated a robust performance in the real human serum with stated LOD and LDR, the engineered immunosensor can be considered for the detection and monitoring of CEA in the clinic.

Electrochemical immunosensor based on multi-order Rubik's cube-type platinum nickel nanocubes and Au NPs/cPDA NTs for detection of CEA

Herein, an innovative sandwich-type electrochemical immunosensor based on multi-order Rubik's cube-type platinum nickel nanocubes and Au NPs/cPDA NTs was used for the ultrasensitive detection of carcinoembryonic antigen (CEA). In this process, an appropriate amount of uniformly dispersed gold nanoparticles (Au NPs) was effectively immobilized on nitrogen riched carbonized polydopamine nanotubes (cPDA NTs) through Au-N bonds, avoiding the stacking and agglomeration of Au NPs, thereby enhancing the conductivity. Subsequently, multi-order Rubik's cube-type platinum nickel nanocubes (PtNi NCs), composed of numerous small interlaced nanocubes, was successfully prepared to immobilize the secondary antibodies (Ab2) effectively. Due to its inherent hierarchical architectures and high density of active sites, PtNi NCs exhibited excellent mass and electron transfer performance towards the reduction of hydrogen peroxide (H2O2) for amplifying the current signal to detect CEA. The rationally designed immunosensor presented a broad linear ranging from 50 fg mL−1 to 100 ng mL−1 and a low limit of detection of 17.78 fg mL−1 (S/N = 3) for CEA determination under optimal conditions. Furthermore, the as-fabricated immunosensor exhibited excellent selectivity, reproducibility and stability, which can be extended to accurate and sensitive detection of other biomarkers.

Advanced Pt hollow nanospheres/rubrene nanoleaves coupled with M-shaped DNA walker for ultrasensitive electrochemiluminescence bioassay

Herein, an intense electrochemiluminescence (ECL) was achieved based on Pt hollow nanospheres/rubrene nanoleaves (Pt HNSs/Rub NLs) without the addition of any coreactant, which was employed for ultrasensitive detection of carcinoembryonic antigen (CEA) coupled with an M-shaped DNA walker (M-DNA walker) as signal switch. Specifically, in comparison with platinum nanoparticles (Pt NPs), Pt HNSs revealed excellent catalytic performance and pore confinement-enhanced ECL, which could significantly amplify ECL intensity of Rub NLs/dissolved O2 (DO) binary system. Then, the tracks and M-DNA walker were confined on the Pt HNSs simultaneously to promote the reaction efficiency, whose M-structure boosted the interaction sites between walking strands and tracks and reduced the rigidity of their recognition. Once the CEA approached the sensing interface, the M-DNA walker was activated based on highly specific aptamer recognition to recover ECL intensity with the assistance of exonuclease Ⅲ (Exo Ⅲ). As proof of concept, the “on-off-on” switch aptasensor was constructed for CEA detection with a low detection limit of 0.20 fg/mL. The principle of the constructed ECL aptasensor also enables a universal platform for sensitive detection of other tumor markers.

Ratiometric electrochemical immunosensor triggered by an advanced oxidation process for the ultrasensitive detection of carcinoembryonic antigen

Conventional electrochemical immunosensors often achieve detection purposes through a single signal output, but its electrical signal is susceptible to external environmental interference, which seriously interferes with the sensitivity and repeatability of the sensors. In this work, a novel ratiometric electrochemical immunosensor triggered by an advanced oxidation process (AOP) was developed for the ultrasensitive detection of carcinoembryonic antigen (CEA). The sensor uses gold nanoparticle-reduced graphene oxide/methylene blue adsorbed by sodium alginate (Au-rGO/MB-SA) as matrix to immobilize primary antibody (Ab1) and Ag nanoparticles-functionalized egg yolk structure Co3O4@SiO2 (Co3O4-Ag@SiO2) as a marker to label secondary antibody (Ab2). When the detection solution contains peroxymonosulfate (PMS), the signal probe Co3O4-Ag@SiO2 activates PMS to produce SO4•−/•OH radicals to degrade MB, thus generating two independent electrochemical signals with opposite directional changes (IAg and IMB). The sensitivity of the sensor is improved due to an enhanced response magnitude on account of the processing of the dual selective responsive signals to yield a response magnitude greater than that of the signal from a single sensor. Square wave voltammetry (SWV) analysis shows that the dual signal ratio (I = IAg/IMB) has a linear relationship with the logarithm of the CEA concentration in the range of 0.01 pg/mL to 40 ng/mL, and the detection limit is as low as 3.42 fg/mL. In addition, the sensor has good selectivity and reproducibility, showing great promise for applications in bioanalysis and disease diagnosis.

Thionine functionalized hollow N-doped carbon nanoboxes: As a high-performance substrate for fabrication of label-free electrochemical aptasensor toward ultrasensitive detection of carcinoembryonic antigen

• A novel electrochemical aptasensor based on Thi@N-C n -box/AuNPs nanocomposites was developed for the determination of CEA. • The Thi@N-C n -box/AuNPs nanocomposites were synthesized to improve the sensitivity of aptasensor. • The aptasensor was successfully used for CEA detection in serum sample. During recent years, the combination of aptamer with new nanomaterials has led to significant improvements in the performance of aptamer-based sensors. The hollow N-doped carbon nanoboxes (N-C n -box) have attracted a lot of attention due to their unique physical and chemical properties and also significant intrinsic cavities which are suitable for loading specific chemicals. In this study, a label free electrochemical aptasensor is described, using thionine (Thi), as a signal molecule, gold nanoparticles (AuNPs) and N-C n -box, as signal amplification platform and high-performance substrate for aptamer strings immobilization for the measurement of carcinoembryonic antigen (CEA), as a model molecule. The presence of the target molecule impedes electron transfer which leads to a decrease in the Thi-associated square wave voltammetry (SWV) peak currents. This approach increases the amount of redox probe at the electrode surface and reduces the distance between the redox probe and the electrode surface. Therefore, this strategy exhibited higher sensitivity and wider linearity in the range of 0.1 fM to 30 nM (17 fg mL −1 –5.4 ng mL −1 ) with a LOD of 0.03 fM (5 fg mL −1 ) and also with good selectivity in the presence of different off-target species. This is the first report on the rational design of N-C n -box shelled with Thi for the electrochemical application.

Stable DNA Aptamer-Metal-Organic Framework as Horseradish Peroxidase Mimic for Ultra-Sensitive Detection of Carcinoembryonic Antigen in Serum.

Carcinoembryonic antigen (CEA) is an important broad-spectrum tumor marker. For CEA detection, a novel type of metal–organic framework (MOF) was prepared by grafting CEA aptamer-incorporated DNA tetrahedral (TDN) nanostructures into PCN-222 (Fe)-based MOF (referred as CEAapt-TDN-MOF colloid nanorods). The synthesized CEAapt-TDN-MOF is a very stable detection system due to the vertex phosphorylated TDN structure at the interface, possessing a one-year shelf-life. Moreover, it exhibits a significant horseradish peroxidase mimicking activity due to the iron porphyrin ring, which leads to a colorimetric reaction upon binding toward antibody-captured CEA. Using this method, we successfully achieved the highly specific and ultra-sensitive detection of CEA with a limit of detection as low as 3.3 pg/mL. In addition, this method can detect and analyze the target proteins in clinical serum samples, effectively identify the difference between normal individuals and patients with colon cancer, and provide a new method for the clinical diagnosis of tumors, demonstrating a great application potential.

A general scattering proximity immunoassay with the formation of dimer of gold nanoparticle

In this work, we structured a colorimetric ultrasensitive detection of carcinoembryonic antigen (CEA) based on a proximity hybridization-induced gold nanoparticles (Au NPs) dimers structure. Under the dark-field microscope, this method takes advantage of the distinctive and strong distance-relative localized surface plasmon resonance (LSPR) of Au NPs and their oriented assembly. DNA served as a medium showing wonderful flexibility to label antibody and Au NPs, and tune interparticle spacing as well. Two capture probes were formed by the integration of DNA labeled antibody (DNA1-Ab1 or DNA2-Ab2) and asymmetrically assembled DNA (DNA 3 or DNA 4)- Au NPs via partly hybridization between DNA sequences. In the presence of antigen, the reaction between target protein and capture probes could trigger the generation of immunocomplex which led to the proximity hybridization of the DNA1 and DNA2, and then change the distance of interparticle to form Au NP dimers and thus showed a different color under dark-field microscope. A limit of detection of 14.25 pg/mL was obtained for the detection of CEA, which indicated a promising sensing method in clinical diagnosis of protein biomarkers.

Biocatalyst and colorimetric biosensor of carcinoembryonic antigen constructed via chicken egg white-copper phosphate organic/inorganic hybrid nanoflowers

In this article, the dual-functional chicken egg white-copper phosphate organic-inorganic hybrid nanoflowers (Cu-NFs), combining the functions of signal amplification and biological recognition, were prepared through a simple one-pot method. The Cu-NFs exhibit excellent biocatalytic activity of peroxidase and polyphenol oxidase. Besides, a biotin-labeled secondary antibody encapsulated Cu-NFs-2 (Cu-NFs-2@Biotin-NHS-Ab2) capture probe was prepared by using the interaction between avidin in the egg white and biotin. Based upon this superiority, the as-prepared Cu-NFs-2 were used in labeled avidin-biotin enzyme-linked immunosorbent assay (Cu-NFs-2 based-LAB-ELISA) to construct a sensitive colorimetric biosensor for the ultrasensitive detection of carcinoembryonic antigen (CEA). Under weak alkaline (pH = 7.5) conditions, the as-developed colorimetric sensor displayed a wide linear range of 0.05–40 ng/mL with a detection limit of 3.52 pg/mL. Furthermore, this colorimetric sensor has been successfully applied to the detection of CEA in human serum samples. Therefore, the as-developed colorimetric sensor has broad application prospects in the field of medical diagnosis and portable detection.

An immunosensor based on an electrochemical-chemical-chemical advanced redox cycle amplification strategy for the ultrasensitive determination of CEA

Signal amplification is very important for electrochemical immunoassays. We report an enzyme-free electrochemical immunosensor based on an electrochemical-chemical-chemical (ECC) redox cycle advanced (RCA) signal amplification strategy for the ultrasensitive detection of Carcinoembryonic antigen (CEA). In this scheme, CeO2/Au NPs@SiO2 is connected with ferrocene as the redox indicator, and the detection buffer is composed of the reducing agent hydroquinone (HQ) and tris(2-carboxyethyl) phosphine (TCEP). First, ferrocenecarboxylic acid (FcA) is oxidized to FcA+ on the electrode. Then, HQ reduces FcA+ to FcA to trigger the cyclic reaction of the inner ring. Second, the oxidation product of HQ is catalyzed by TCEP. The product is reduced to HQ again to complete the cyclic reaction of the outer ring, so the entire cyclic reaction forms a closed loop. The system realizes the high-efficiency regeneration of the electroactive material Fc, thereby ensuring the full amplification of the electrical signal. The results show that the immunosensor exhibits good analytical performance, the detection range is 0.01 pg/mL-80 ng/mL, the detection limit is 0.0037 pg/mL, and the immunosensor has excellent selectivity and stability and performs well in the detection of actual samples. This strategy provides a new method for the early screening of CEA.

Cellulose nanocrystalline and sodium benzenesulfonate-doped polypyrrole nano-hydrogel/Au composites for ultrasensitive detection of carcinoembryonic antigen

Scheme illustrates the fabrication procedures of the proposed immunosensor. The proposed immunosensor shows ultrasensitive detection of carcinoembryonic antigen.

Ratiometric Electrochemical Immunosensor Triggered by an Advanced Oxidation Process for the Ultrasensitive Detection of Carcinoembryonic Antigen

Ratiometric Electrochemical Immunosensor Triggered by an Advanced Oxidation Process for the Ultrasensitive Detection of Carcinoembryonic Antigen

Dual labeled mesoporous silica nanospheres based electrochemical immunosensor for ultrasensitive detection of carcinoembryonic antigen

Carcinoembryonic antigen (CEA) is a well-known cancer biomarker for the detection of several malignancies. The development of ultrasensitive CEA diagnostic tools is crucial for early detection and progression observation of tumors. Herein, a dual signal amplified sandwich-type electrochemical immunoassay was developed based on dual-labeled mesoporous silica nanospheres as a signal amplifier, combined with NiO@Au decorated graphene as a conductive layer for ultrasensitive and rapid determination of CEA. The dual-labeled mesoporous silica (DLMS) nanosphere, which was synthesized by entrapping Au nanorod (Au NR) and horseradish peroxidase (HRP) in the channels of amine-functionalized SBA-15 followed by subordinate antibody (Ab2) conjugation which was denoted as Au NR@SBA-15/Ab2-HRP. The dual signal amplification from Au NR@SBA-15 and HRP enhanced the sensitivity of the proposed immunoassay. Consequently, the developed DLMS based immunosensor displayed ultra-low limits of detection of 5.25 fg/mL and a wide range of linearity (0.1–5 pg/mL), which was extended for CEA determination in real-time samples with improved recoveries of >98%. Therefore, this dual amplification prototype would cater to the clinical requirements for the ultrasensitive detection of CEA biomarkers.

Visible-light-driven renewable photoelectrochemical/synchronous visualized sensing platform based on Ni:FeOOH/BiVO4 photoanode and enzymatic cascade amplification for carcinoembryonic antigen detection

A renewable photoelectrochemical/synchronous visualized sensing platform with two functional cells, named sensing and electrochromic cells, was developed for ultrasensitive detection of carcinoembryonic antigen (CEA). For achieving a boosted photocurrent intensity, the Ni:FeOOH/BiVO4 nanocomposites were engineered and served as the photoanode materials, which were then combined with the cathode material Prussian blue (PB) to form the sensing cell. Through the sandwich-type immunoreaction and enzymatic cascade amplification, the carried GOx could catalyse the decomposition of glucose to produce H2O2, leading to improvement of electron transfer efficiency of Ni:FeOOH/BiVO4 under the light irradiation and accompanying by the PB reduced to Prussian white (PW). By combining digital multimeter (DMM)-joined circuit to collect photocurrents with PB electrochromic indicator, ultrasensitive and naked eye visual detection of CEA was realized synchronously. On the electrochromic cell, laccase as the biocathode enabled PW back to the original PB state through the biocatalyzing oxygen reduction of the laccase, gaining an updatable sensing platform. Under the optimal conditions, the bimodal biosensor shows acceptable dynamic working range for CEA from 1 pg·mL−1 to 90 ng·mL−1 with a detection limit (LOD) of 0.35 pg mL−1. Meanwhile, it also has great potential applications in real sample analysis.

3D DNA nanosphere-based photoelectrochemical biosensor combined with multiple enzyme-free amplification for ultrasensitive detection of cancer biomarkers

In this work, a new 3D DNA nanosphere was ingeniously designed and fabricated, which was used to combine with multiple enzyme-free amplification strategy to develop a photoelectrochemical (PEC) biosensing platform for ultrasensitive detection of carcinoembryonic antigen (CEA). The 3D DNA nanostructure was self-assembled by base complementary pairing in a few minutes and rolling circle amplification (RCA) reaction. The intense photocurrent derived from Au NPs/ZnSe QDs can be effectively decreased by 3D DNA nanospheres assembled on the electrode, making photoelectric signal present “off” state. The specific binding of target CEA with its hairpin (HP1) aptamer opens HP1 structure, which initiated multiple enzyme-free strand displacement amplification (SDA) reaction and generated a large number of single strands DNA S1. Then S1 competitively binds to capture DNA on the electrode to release 3D DNA nanospheres, thus the photocurrent signal became “on” state for achieving amplified assay of target CEA. The proposed PEC biosensor exhibits excellent performance with a wide linear range of 1.0 fg/mL to 10 ng/mL and a low detection limit of 0.12 fg/mL for CEA, which was successfully applied for the assay of real serum samples with good precision. The reported strategy opens a new simple way for PEC biosensor using DNA nanostructure, showing huge potential in clinical application research.

A sandwich-type electrochemical immunosensor using polythionine/AuNPs nanocomposites as label for ultrasensitive detection of carcinoembryonic antigen

A sandwich-type electrochemical immunosensor was developed in this study for sensitive detection of carcinoembryonic antigen (CEA) based on rGO/CS/AuNPs as a sensing platform and PTh-Au composites as signal labels. Reduced graphene oxide (rGO), Chitosan (CS) and AuNPs were layer by layer modified on glass carbon electrode (GCE), which effectively enhanced electron transfer and provided excellent large electrochemical active surface area. Polythionine-Au composites prepared by chemical reduction method greatly amplified electrochemical signal with high conductivity and large surface area. The prepared immunosensor showed high sensitivity, good stability and selectivity for detection of CEA with a wide range of 0.3 ng/mL to 30 ng/mL (R2 = 0.9972) and a detection limit as low as 0.1471 pg/mL. Furthermore, this sandwich-type immunosensor might be as a versatile platform for reliable early cancer diagnostics clinical.

Gold and silver bio/nano-hybrids-based electrochemical immunosensor for ultrasensitive detection of carcinoembryonic antigen

Carcinoembryonic antigen (CEA) is an important oncomarker for the detection of breast cancer. For ultra-sensitive sensing of CEA with great specificity and accuracy, an innovative and reliable electrochemical immunosensor was developed using various nano-hybrids. A glassy carbon electrode (GC) was modified with thiolated graphene oxide (T-GO) to elevate the active surface area of the electrode. The streptavidin-coated gold nanoparticles (AuNPs) were used to increase the conductivity of the sensing area as well as the loading capacity of the biotinylated monoclonal antibody (mAb). A sandwich-on approach was developed to reach a low limit of detection (LOD). The biotinylated mAb, streptavidin coated silver nanoparticles (AgNPs) and horseradish peroxidase (HRP), altogether, formed the signaling probe of the proposed immunosensor. The electrochemical signal was significantly enhanced in the presence of hydroquinone (HQ) and hydrogen peroxide (H2O2). Under the optimized conditions, the proposed immunosensor presented an excellent performance in a linear range of 100 fg/mL to 5 pg/mL with a low detection limit of 75 fg/mL. The engineered immunosensor displayed excellent specificity for the detection of CEA even in the real human serum, upon which it is proposed for the early detection and monitoring of CEA in the clinic.