Label-free Aptasensor Research Articles

Selection and characterization of novel aptamers specific for patulin and label-free split sensing

The selection of novel aptamers specific for patulin (PAT) and the construction of a label-free split aptasensor for the detection of PAT are described. The ssDNA library was immobilized on streptavidin resin, and the enriched libraries were sequenced via high-throughput sequencing. After sequence homology analyses, the candidate aptamers were identified using isothermal titration calorimetry (ITC). Split aptamers (S6-a-1/S6-b-2) were designed as the sandwich aptasensor for PAT detection. The results from the sequencing indicated that the DNA was enriched in the 18th round. The ITC analysis revealed that the aptamers of family 1 had high affinity for PAT, with kd values ranging from 0.45-3.64 µM. The candidate aptamers were shorter (46 bases) than previously reported PAT aptamers. The LOD of the split aptasensor based on PAT-6 was 0.25 µM, and the aptasensor was able to function properly in a 10 % apple juice matrix. Thus, a novel aptamer specific for PAT was reported, and a label-free split aptasensor with low cost and rapid response time for the detection of PAT residue was developed.

Detection of C-reactive protein using a label-free NIR fluorescent aptasensor with a large Stokes shift based on an AIEE anthracene derivative

BackgroundC-reactive protein (CRP), one of the classic biomarkers of inflammation, is closely related to infectious inflammation, cardiovascular disease, cancer, and other diseases. Therefore, timely and accurate detection of CRP in human blood is crucial for the discovery, diagnosis, and treatment of the aforementioned diseases. Herein, a novel label-free NIR fluorescence aptasensor with a large Stokes shift based on an AIEE anthracene derivative B and a molybdenum disulfide (MoS2) platform was developed and used for the high sensitivity and specificity detection of CRP. ResultsCompound B could emit near-infrared (NIR) fluorescence with a large Stokes shift (190 nm). Notably, this compound could bind with the aptamer of CRP (CRP-Apt) through electrostatic attraction to form a B/CRP-Apt complex, generating an aggregation-induced emission enhancement effect and enhancing the fluorescent intensity of B. B/CRP-Apt could be adsorbed on the surface of MoS2 with the addition of MoS2 to its solution, and the fluorescence of Compound B was quenched. CRP was then added to the above solution. CRP-Apt had a substantially higher affinity for CRP than MoS2. Therefore, B/CRP-Apt detached from the surface of MoS2 and bound to CRP, thereby restoring the fluorescence of B. Experimental results showed a good linear relationship between the fluorescent recovery intensity of B and the concentration of CRP in the concentration range of 0.3–70 ng mL−1, with a limit of detection as low as 0.1 ng mL−1. Significance and NoveltyThe aptasensor integrates the advantages of high sensitivity of NIR fluorescence, high specificity of aptamers, good water-solubility and AIEE effect of Compound B. And it could be applied to the determination of CRP in human serum samples, while most of the reported methods can only determine CRP in spiked human serum samples.

Aptamer regulated peroxidase-like activity of cobalt oxyhydroxide nanosheets for colorimetric detection of kanamycin.

A straightforward label-free colorimetric aptasensor utilizing the aptamer-enhanced peroxidase-like activity of cobalt oxyhydroxide (CoOOH) nanosheets has been established for kanamycin detection. In the kanamycin-free state, aptamers adsorb onto the CoOOH surface through electrostatic forces, enhancing the peroxidase-like activity of CoOOH and thereby resulting in a strong absorption signal and a yellow hue in 3,3',5,5'-tetramethylbenzidine (TMB) upon termination of the reaction with a stop solution. Conversely, upon the introduction of kanamycin, aptamers and CoOOH nanosheets compete for binding to kanamycin, resulting in a significant decrease in the number of aptamers bound to CoOOH. As a result, the activity of CoOOH diminishes, leading to a corresponding reduction in coloration and absorbance of the solution. Hence, the quantitative determination of kanamycin could be realized by analyzing the absorbance variations. Under optimal conditions, the aptasensor demonstrated high sensitivity and specificity, with a linear detection range from 500nM to 5µM and a detection limit as low as 54.6nM. Moreover, the aptasensor effectively identified kanamycin in river water samples, achieving a recovery rate between 91.7% and 102.1%. This approach offers good practicability and provides a novel platform for kanamycin detection in environmental samples.

Enzyme- and label-free cascade isothermal amplification aptasensor for the ultrasensitive detection of ochratoxin A

BackgroundUltrasensitive detection is crucial for the early warning and intervention of risk factors, ultimately benefiting the environment and human health. Low levels of ochratoxin A (OTA) present a hidden yet significant threat, and rapid detection via high-performing biosensors is therefore essential. ResultsA cascade isothermal amplification aptasensor (CIA-aptasensor) was designed for OTA detection. On the surface of a magnetic bead probe, the OTA level was converted into positively correlated trigger cDNA through its competitive binding with OTA-Apt. The released trigger cDNA activated catalytic hairpin assembly followed by coupling with a hybridization chain reaction to achieve CIA. After adding graphene oxide and SYBR Green I, the background interference was eliminated to specifically obtain OTA-related fluorescence. The ultrasensitive limit of detection was 0.22 pg mL−1, an improvement of 1368-fold over conventional enzyme-linked aptamer sorbent assay by the same OTA-Apt, demonstrating satisfactory reliability and practicability. Thus, the CIA-aptasensor provides an enzyme- and label-free simplified homogeneous system with minimal background interference using isothermal conditions. SignificanceThis study provides a polymerase chain reaction–like approach for enhancing the sensitivity and performance of a biosensor, which could be extended for the application of CIA and label-free signaling strategy to other risk factors.

Generation of specific aptamers for constructing CoOOH nanozymes-based colorimetric aptasensor for detection of fleroxacin in milk

The misuse or abuse of fleroxacin (FLE) in livestock and aquaculture can result in elevated levels of FLE in animal-derived foods, posing significant health risks to humans. Detection of FLE has been relying on instrumental analysis methods that need expensive equipment and longer analysis time. Herein we report the first isolation of two specificity aptamers against FLE (FLE-9 and FLE-51) by capture-SELEX, characterized them well and explored the binding mechanism. Furthermore, FLE-9 was selected to construct a CoOOH@Apt based biosensor. The catalytic activity of the biosensor was evaluated using the Michaelis equation, revealing a Vmax of 4.87×10−8 M s−1 and a Km of 0.11 mM. These results suggest that the affinity of CoOOH@Apt is higher than that of CoOOH nanozymes. In the present of FLE, the aptamer FLE-9 specifically binds to FLE, distancing itself from CoOOH nanozymes and thereby reducing the catalytic activity of the biosensor. Finally, the label-free colorimetric aptasensor was successfully applied to detect FLE, with a detection limit of 4.26 ng/mL. The recovery rates ranged from 96.70 % to 101.70 %, with a relative standard deviation (RSD) below 3.02 %. This study presents promising probes and a novel strategy for the determination of FLE in milk samples, contributing to improved food safety monitoring.

Lattice matching enables construction of CaS@NaYF4 heterostructure with synergistically enhanced water resistance and luminescence for antibiotic detection.

Rare earth (RE)-doped CaS phosphors have been widely used as light-emitting components in various fields. Nevertheless, the application of nanosized CaS particles is still significantly limited by their poor water resistance and weak luminescence. Herein, a lattice-matching strategy is developed by growing an inert shell of cubic NaYF4 phase on the CaS luminescent core. Due to their similarity in crystal structure, a uniform core-shell heterostructure (CaS:Ce3+@NaYF4) can be obtained, which effectively protects theCaS:Ce3+ core from degradation in aqueous environment and enhances its luminescence intensity. As a proof of concept, a label-free aptasensor is further constructed by combining core-shell CaS:Ce3+@NaYF4 and Au nanoparticles (AuNPs) for the ultrasensitive detection of kanamycin antibiotics. Based on the efficient FRET process, the detection linear range of kanamycin spans from 100 to 1000 nM with a detection limit of 7.8 nM. Besides, the aptasensor shows excellent selectivity towards kanamycin antibiotics, and has been successfully applied to the detection of kanamycin spiked in tap water and milk samples, demonstrating its highpotential for sensing applications.

Label-Free and Ultra-Sensitive Detection of Dexamethasone Using a FRET Aptasensor Utilizing Cationic Conjugated Polymers.

Dexamethasone (Dex) is a widely used glucocorticoid in medical practice, with applications ranging from allergies and inflammation to cerebral edema and shock. Despite its therapeutic benefits, Dex is classified as a prohibited substance for athletes due to its potential performance-enhancing effects. Consequently, there is a critical need for a convenient and rapid detection platform to enable prompt and accurate testing of this drug. In this study, we propose a label-free Förster Resonance Energy Transfer (FRET) aptasensor platform for Dex detection utilizing conjugated polymers (CPs), cationic conjugated polymers (CCPs), and gene finder probes (GFs). The system operates by exploiting the electrostatic interactions between positively charged CCPs and negatively charged DNA, facilitating sensitive and specific Dex detection. The label-free FRET aptasensor platform demonstrated robust performance in detecting Dex, exhibiting high selectivity and sensitivity. The system effectively distinguished Dex from interfering molecules and achieved stable detection across a range of concentrations in a commonly used sports drink matrix. Overall, the label-free FRET Dex detection system offers a simple, cost-effective, and highly sensitive approach for detecting Dex in diverse sample matrices. Its simplicity and effectiveness make it a promising tool for anti-doping efforts and other applications requiring rapid and accurate Dex detection.

Optical Label-Free Aptasensor Based on Weak Value Amplification for Real-Time and Ultrasensitive Detection of IgE.

Allergy is a prevalent disease, and the potential allergic population is expanding with industrialization and changes in people's living standards. Serum immunoglobulin E (IgE) level is one of the critical indicators for determining allergy. Here, we proposed a simple, real-time monitoring, low chip cost, label-free aptamer biosensing strategy based on weak value amplification (WVA) for the quantitative detection of IgE in serum samples, enabling early and accurate diagnosis of allergic or hypersensitive patients. The aptasensor combined an imaging weak measurement system with the high specificity of the aptamer for the marker IgE. By modifying the amino group at the 3-terminal end, the anti-IgE aptamers can attach to a dopamine-modified prism's surface and selectively recognize IgE in human serum. In the presence of IgE, a specific binding reaction occurred, resulting in a change in the refractive index of the reactive region's surface, manifested as a change in the light intensity of the camera acquired experimental images. As the concentration of IgE increased, the relative light intensity advanced sequentially. The WVA-aptasensing strategy achieved a wide detection range of 0.01 ng/mL to 2 μg/mL in phosphate buffered saline buffer, with the resolution as low as 4.3 pg/mL. IgE testing experiments in human serum have proved the feasibility of our methods in detecting complex samples. In addition, the method specifically recognized IgE without interference from other proteins. We believe that our proposed sensing strategy opens up new possibilities for ultrahigh sensitivity screening of IgE and can be expanded to detecting other biomolecules.

Label-free fluorescent aptasensor for myoglobin detection based on an aggregation-induced emission enhancement imidazole compound and a Fe3O4@4-VP platform

Acute myocardial infarction (AMI) is recognized as one of the deadliest cardiovascular diseases in the world, causing serious public health problems worldwide. Myoglobin (Mb) is an important biomarker for AMI. Therefore, the accurate detection of Mb is crucial for the early detection and clinical diagnosis of AMI. In this study, a novel imidazole Compound C and novel Fe3O4@4-VP microspheres were prepared and used to construct an unlabeled fluorescence aptasensor for Mb detection. Compound C can bind to the aptamer of Mb (Mb-Apt) through electrostatic attraction to form a C/Mb-Apt complex and produce the aggregation-induced emission enhancement effect. Then, Mb was added to the C/Mb-Apt solution. Mb could combine with C/Mb-Apt to form a C/Mb-Apt/Mb complex. Subsequently, Fe3O4@4-VP was added to the above mixture. The bases of Mb-Apt already combined with Mb, and thus, C/Mb-Apt/Mb would no longer interact with the pyridine rings on the surface of Fe3O4@4-VP through π-π stacking. After magnetic separation, the C/Mb-Apt/Mb complex remained in the supernate. The supernate exhibited strong fluorescence and its fluorescent intensity was proportional to the level of Mb. Experimental results showed an excellent linear relationship between the fluorescent intensity of the supernate and the level of Mb within the range of 0.167–20 ng/mL, with a detection limit reaching as low as 0.05 ng/mL (S/N = 3). In addition, the aptasensor exhibited high specificity and could be used for detecting Mb in human serum.

Parylene Double-Layer Coated Screen-Printed Carbon Electrode for Label-Free and Reagentless Capacitive Aptasensing of Gliadin.

Celiac patients are required to strictly adhere to a gluten-free diet because even trace amounts of gluten can damage their small intestine and leading to serious complications. Despite increased awareness, gluten can still be present in products due to cross-contamination or hidden ingredients, making regular monitoring essential. With the goal of guaranteeing food safety for consuming labeled gluten-free products, a capacitive aptasensor was constructed to target gliadin, the main allergic gluten protein for celiac disease. The success of capacitive aptasensing was primarily realized by coating a Parylene double-layer (1000 nm Parylene C at the bottom with 400 nm Parylene AM on top) on the electrode surface to ensure both high insulation quality and abundant reactive amino functionalities. Under the optimal concentration of aptamer (5 μM) used for immobilization, a strong linear relationship exists between the amount of gliadin (0.01-1.0 mg/mL) and the corresponding ΔC response (total capacitance decrease during a 20 min monitoring period after sample introduction), with an R2 of 0.9843. The detection limit is 0.007 mg/mL (S/N > 5), equivalent to 0.014 mg/mL (14 ppm) of gluten content. Spike recovery tests identified this system is free from interferences in corn and cassava flour matrices. The analytical results of 24 commercial wheat flour samples correlated well with a gliadin ELISA assay (R2 = 0.9754). The proposed label-free and reagentless capacitive aptasensor offers advantages of simplicity, cost-effectiveness, ease of production, and speediness, making it a promising tool for verifying products labeled as gluten-free (gluten content <20 ppm).

Portable Aptasensor Based on Parallel Rolling Circle Amplification for Tumor-Derived Exosomes Liquid Biopsy.

Here, a separation-free and label-free portable aptasensor is developed for rapid and sensitive analysis of tumor-derived exosomes (TEXs). It integrated a parallel rolling circle amplification (RCA) reaction, selective binding of metal ions or small molecules to nucleic acid-specific conformations, and a low-cost, highly sensitive handheld fluorometer. Lung cancer, for example, is targeted with two typical biomarkers (mucin 1 and programmed cell death ligand 1 (PD-L1)) on its exosomes. The affinity of aptamers to the targets modulated the amount of RCA products (T-Hg2+-T and cytosine (C)-rich single-stranded DNA), which in turn affected the fluorescence intensity of quantum dots (QDs) and methylene blue (MB). The results revealed that the limit of detection (LOD) of the handheld fluorometer for cell-derived exosomes can be as low as 30 particlesmL-1. Moreover, its specificity, sensitivity, and area under the curve (AUC) are 93% (14/15), 92% (23/25), and 0.956, as determined by the analysis of 40 clinical samples. Retesting 16 of these samples with the handheld fluorometer yielded strong concordance between the fluorometer results and those acquired from clinical computed tomography (CT) and pathology.

Development of ultra-sensitive and label-free ellipsometric aptasensor for the detection of residual fipronil

Fipronil, an insecticide widely employed, poses risks to both the environment and human health. Existing detection methods for fipronil and its metabolites, such as GC–MS, are known; however, these methods are laborious and time-intensive. In this investigation, our aim was to devise a label-free aptasensor strategy for detecting fipronil in food-related scenarios. To achieve this objective, we developed ellipsometric-based aptasensors specifically tailored for fipronil detection. The advantage of ellipsometric sensors lies in their efficacy in analyzing thin and uniform films. Spectrophotometric ellipsometry (SE), utilized in this realm, is preferred due to its sensitivity to molecular accumulation at the substrate surface, as evidenced by the phase shift (Δ). The limit of detection (LOD) observed in the buffer solution for the two aptamers, Anti-FIP1 and Anti-FIP2, used in this study, with lengths of 80 and 73 bases respectively, showed promising results. Additionally, the specificity of these aptamers against bovine serum albumin and ethiprole in the SE sensor approached the reproducibility limit. This is attributed to the wide-ranging cocktail employed during the aptamer selection process. The LOD for Anti-FIP1 was 0.034 nM (33.7 pM), while for Anti-FIP2 it was 0.025 nM (24.9 pM). The limit of quantification (LOQ) was calculated as 0.1 nM (0.044 ng/mL) for Anti-FIP1 and 0.075 nM (0.033 ng/mL) for Anti-FIP2. Utilizing the spike method for fipronil detection by introducing egg and grain samples, the deviation observed was less than ±10 % for recovery. This study presents a dependable aptasensor platform for the testing of fipronil in food samples, employing aptamer-based SE.

Tag-free fluorometric aptasensor for detection of chromium(VI) in foods via SYBR Green I signal amplification and aptamer structure transition.

In response to growing concerns regarding heavy metal contamination in food, particularly chromium (Cr)(VI) contamination, this study presented a simple, sensitive and practical method for Cr(VI) detection. A magnetic separation-based capture-exponential enrichment ligand system evolution (SELEX) method was used to identify and characterize DNA aptamers with a high affinity for Cr(VI). An aptamer, Cr-15, with a dissociation constant (Kd) of 4.42 ± 0.44 μmol L-1 was obtained after only eight rounds of selection. Further innovative methods combining molecular docking, dynamic simulation and thermodynamic analysis revealed that CrO4 2- could bind to the 19th and 20th guanine bases of Cr-15 via hydrogen bonds. Crucially, a label-free fluorometric aptasensor based on SYBR Green I was successfully constructed to detect CrO4 2-, achieving a linear detection range of 60-300 nmol L-1 with a lower limit of detection of 44.31 nmol L-1. Additionally, this aptasensor was able to quantitatively detect CrO4 2- in grapes and broccoli within 40 min, with spike recovery rates ranging from 89.22% to 108.05%. The designed fluorometric aptasensor exhibited high selectivity and could detect CrO4 2- in real samples without sample processing or target pre-enrichment. The aptasensor demonstrated its potential as a reliable tool for monitoring Cr(VI) contamination in fruit and vegetable products. © 2024 Society of Chemical Industry.

Label-free aptasensor targeting Staphylococcus aureus surface Protein A

The rapid detection of Staphylococcus aureus (S. aureus) is of major importance for the biomedical world in the context where the antimicrobial resistance (AMR), the “silent pandemic”, is considered a global public health threat to humanity. There are various approaches to detect S. aureus either as a whole bacterium or via different biomarkers that indicate the presence of this microorganism. Herein, a label-free aptasensor was designed for the detection of a cellular bacterial wall component, protein A (PrA), as a biomarker for the bacteria presence. A rapid procedure, under 5 min, that involves the deposition of the aptamer at the surface of a gold-based screen-printed electrode was applied followed by a blocking step to prevent non-specific adsorption of the target. After the incubation with PrA, the electrochemical detection was achieved, the aptasensor exhibiting good sensitivity across a wide linear range from 25 nM to 1000 nM, with a limit of detection (LOD) of 8.33 nM in standard solutions of the target. S. aureus was detected in commercial human serum and culture samples displaying a good correlation of the signal and the number of bacteria colonies, in the latter case.

A Three-Dimensional AgNPs/TiO2/Ti3C2Tx Composite for Label-Free Thrombin Aptamer Sensor

A one-step hydrothermal method was employed to synthesize a three-dimensional (3D) AgNPs/TiO2/Ti3C2Tx composite. Hydrothermal conditions were used to promote the growth of TiO2 nanorods on the Ti3C2Tx sheet, resulting in the formation of a three-dimensional composite nanomaterial. Glutamic acid served as both a reducing agent and a stabilizer to load Ag nanoparticles (AgNPs) onto the 3D composite nanomaterial. The structure of the composite material provided a large accessible surface area, facilitating the anchoring of Ag NPs. Thrombin aptamers were then linked to Ag NPs through Ag-S bonds, establishing a sensitive and label-free aptasensor for thrombin detection. The proposed aptasensor demonstrated excellent electrochemical performance, with a broad linearity range of 5.0 fM to 500 nM and a relatively low detection limit of 2.0 fM (S/N = 3). These findings indicate the potential of Ag NPs/TiO2/Ti3C2Tx in the development of promising electrochemical biosensors.

A simple Label-Free aptasensor for acrylamide monitoring using a Four-Way arm junction structure of DNA strands

Herein, a sensitive and simple tag-free aptasensor was employed for acrylamide determination via the fluorescent dye SYBR Green I (SGI) with the role of signal indicator. The foundation of this platform was built upon the establishment of a four-way junction structure, which resulted from the hybridization between terminus regions of aptamer and complementary (CP) strands. The preferential interaction of the aptamer sequence with acrylamide led to the disintegration of the four-way junction structure into the single strands, and consequently, a significant decrease in the output fluorescence signal. Under the optimal conditions, the proposed aptasensor was shown to detect acrylamide, with low detection limit (LOD) of 0.28 μmol/L in the linear dynamic range of 1 to 60 μmol/L with high selectivity. The aptasensor possesses remarkable proficiency in detecting acrylamide levels within coffee samples, rendering it as a highly effective tool for ensuring the safety and quality control of food products.

Levan modified patulin specific impedimetric aptasensor with its application in food and biological fluids

In this study, a label-free impedimetric aptasensor was developed for the determination of patulin (PAT) mycotoxin. The pencil graphite electrode (PGE) surface was modified with the levan and then PAT-specific aptamer was immobilized onto the PGE surface. After the interaction of PAT with aptamer EIS measurements were performed. Under optimum conditions, the limit of detection (LOD) in buffer medium was calculated as 0.095 pg/mL in the concentration range of 10−1–105 pg/mL. The selectivity of the developed label-free impedimetric aptasensor was investigated against fumonisin B1 (FB1), ochratoxin A (OTA), and deoxynivalenol (DON) in buffer medium. The implementation of label-free impedimetric aptasensor to patulin determination was performed in apple juice samples as well as in fetal bovine serum (FBS) medium. Accordingly, the LOD of PAT was estimated as 3.27 pg/mL in apple juice and 0.41 pg/mL in the FBS medium. The selectivity of the aptasensor was also investigated in both mediums. It is predicted that the developed aptasensor will have an important place in the fields of food safety and health monitoring in the literature. Also, it is anticipated that the electrochemical determination of mycotoxins, especially in biological fluids, will be a role model for future studies.

Probing aptamer-mucin 1 binding events on polydopamine@carbon nanotubes modified cellulose paper interface using speckle pattern analysis for label free aptasensing

Herein, we have developed a cellulose paper-based aptasensing protocol by employing dynamic laser speckle (DLS) analysis for direct and label-free probing of the binding interface. Cellulose filter paper surface was modified by using the mussel adhesion chemistry of polydopamine modified carbon nanotubes (PDA@CNTS). The mussel chemistry resulted in strong adhesion and binding of PDA@CNTs on cellulose paper surface. The modified surface was subsequently employed in the construction of label free aptasensor for detection of cancer biomarker mucin 1 (MUC1). Taking advantage of DLS technique, it provided us with sensitive and accurate analysis of target biomarker MUC1 by the intrinsic randomness of patterns generated from cellulose based paper surface. The developed aptasensor was evaluated using DLS at various fabrication steps, where the scattered laser beams from these samples were collected and analyzed based on the obtained speckle patterns. Under the optimal experimental conditions, paper-based aptasensor achieved sensitive and selective detection of MUC1, exhibiting excellent linear range (15–100) µM with a limit of detection of 1 µM. This work presents a novel study of promising laser speckle paper-based aptasensor, providing new insights for the development of low-cost, sensitive, and portable paper-based analytical tools for biological applications.

Label-free fluorescence aptasensor for the detection of cadmium(II) ion based on the conformational switching of aptamer and thioflavine T.

A simple label-free Cd2+ fluorescent aptasensor was proposed using aptamer as a recognition element and thioflavine T (ThT) as a signal reporter. The presence of Cd(II) can induce the conformational switching of the aptamer probe, accompanied by a change in fluorescence intensity. According to the difference in fluorescence signals before and after the addition of Cd2+, a fluorescence sensor for Cd2+ assay was established. Under the better experimental conditions, the sensor displayed a good linear range from 2 to 50nM and the excellent detection limit was 0.8nM. The method demonstrated high sensitivity and good selectivity. The aptasensor could detect Cd2+ in simulated water samples with satisfactory results. The proposed method had obvious advantages that was without chemical modification of fluorescent groups and complicated target preconcentration. It provided a new analytical platform for the detection of heavy metal ion pollution in environmental and biomedical fields.

Detecting carcinoembryonic antigen based on the aggregation-induced emission enhancement effect.

In this study, a novel label-free fluorescent aptasensor with an aggregation-induced emission enhancement effect was developed and applied for the detection of carcinoembryonic antigen (CEA). The sensor has a simple detection mechanism, easy operation, high sensitivity (with low limit of detection of 1 pg mL-1), good selectivity, and wide linear range (0.003-10 ng mL-1). In addition, it can be directly applied for the determination of CEA in human serum.