Detection Of Α-fetoprotein Research Articles

Dual-mode detection of α-fetoprotein using the photothermal effect and peroxidase-like activity of Au@Cu/Cu2O-rGO

α-Fetoprotein (AFP) is widely recognized as an important marker for monitoring hepatocellular carcinoma (HCC), and its monitoring using two different transduction mechanisms is an effective way to avoid the risk of false positives or false negatives. In this paper, Au@Cu/Cu2O-rGO was used as a photothermal converter as well as an actuator to promote the decomposition of hydrogen peroxide (H2O2), which was further designed as a probe for dual-mode detection to quantitatively assess AFP. The composite nanomaterials possessed photothermal conversion efficiencies (η) of up to 54.9 % and catalytically generated signals up to 1.6 times greater, relative to a single material. Based on the generated temperature and current signals, AFP has been sensitively detected in the range of 0.01–100 ng/mL, with limits of detection (LOD) of 5.62 pg/mL and 1.23 pg/mL, respectively. The dual-mode assay combines portability with high accuracy for the detection of human health systems.

Construction of a Three-Dimensional-Printed Immunosensing Platform Based on Smartphone Photothermal Signal Integration.

The combination of the photothermal effect and immunoassay serves as a potent tool for crafting cost-effective and user-friendly biosensing systems. To ensure efficient light-to-heat conversion, we integrated three-dimensional-printed (3D printed) technology to devise a novel design. This design functions as the structural support for both the cell phone and laser probe, as well as a means for sample handling. The main body features a three-way cavity structure, securing the test sample at a fixed position to maintain consistent light distance and angle, thereby minimizing testing errors. Card slot insert facilitates precise sample positioning to ensure the adequacy of receiving light. The sample holder's wide front and narrow back design enables the accommodation of fixed samples while providing a broad field of view, with intervals therein effectively preventing cascading heat. Our design employs MB@MOF235 (methylene blue adsorbed by iron terephthalate) as the photothermal reagent, successfully enabling the detection of α-fetoprotein (AFP). The detection range spans from 0.01 to 50 ng/mL, with a lower detection limit (LOD) of 0.032 pg/mL. The detection method, combining simplicity, portability, and visualization, offers a reliable reference for furthering precision medicine toward personalized medicine. Meanwhile, to verify the method's accuracy electrochemical testing was conducted to support the proof using the electro-oxidizing activity of MB.

Tetrahedral DNA-linked aptamer-antibody-based sandwich-type electrochemical sensor with Ag@Au core-shell nanoparticles as a signal amplifier for highly sensitive detection of α-fetoprotein.

The conventional electrochemical detection strategy for alpha-fetoprotein (AFP) is limited by the antigen-antibody (Ag-Ab) reactions and suffers from low sensitivity and poor reproducibility due to the inconsistency of Ab-modified electrodes. Herein, we designed and explored a sandwich-type electrochemical sensor for highly sensitive detection of AFP based on aptamer (Apt)-AFP-Ab interaction mode with silver@gold (Ag@Au) core-shell nanoparticles (NPs) as a signal amplifier. AuNPs were electrodeposited onto MXene (Ti3C2TX)-modified glassy carbon electrode (GCE) to get AuNPs/MXene/GCE and further used as the signal amplification substrate. The tetrahedral DNA-linked AFP aptamers were immobilized onto AuNPs/MXene/GCE surface via Au-S bonds and used as the sensing and recognition platform for AFP capturing. Ag@AuNPs with core-shell structures were synthesized, characterized, and bound with Ab as detection elements by catalyzing H2O2 reduction. In thepresence of AFP, a stable Apt-AFP-Ab sandwich structure was formed owing to the high affinities of aptamer and Ab toward the target AFP. The catalytic current produced by H2O2 reduction increased linearly with thelogarithm ofAFP concentration from 5 × 10-4 ng/mL to 1 × 105 ng/mL, accompanied by a low detection limit (1.6 × 10-4 ng/mL). Moreover, the novel sandwich-type electrochemical sensor shows high sensitivity, outstanding selectivity, and promising performance in the analysis of actual samples, displaying a broad application prospect in bioanalysis.

A sensitive photoelectrochemical biosensor for α-fetoprotein detection based on anthocyanin sensitized La2Ti2O7/poly(5-formylindole) heterojunctions

A photoelectrochemical (PEC) biosensor based on anthocyanin sensitized La2Ti2O7/poly(5-formylindole) (La2Ti2O7/P5FIn) p-n heterojunctions was constructed for the sensitive detection of α-fetoprotein (AFP). The La2Ti2O7/P5FIn heterojunction effectively utilized visible light and improved the electron transport rate, and anthocyanin sensitization greatly enhanced the photocurrent signal and expanded the detection range. Additionally, the energy level matching between CdSe quantum dots (CdSe QDs) and La2Ti2O7, as well as the scavenging of photogenerated holes by electrons from the catalytic reaction between glucose and glucose oxidase (GOD), improved photoelectron conversion efficiency and amplified photocurrent signal significantly. Specific immune responses were used to fix AFP and AFP-CdSe-GOD complexes on anthocyanin-sensitized La2Ti2O7/P5FIn electrodes, enabling sensitive detection of AFP through competitive binding. The linear detection range (LDR) is 0.001–100 ng mL−1 and the detection limit (LOD) is 0.00055 ng mL−1. At the same time, the PEC sensor also has a good analytical ability in detecting AFP in real samples, which also provides a new idea for the development of other protein detection methods.

NIR-II fluorescence lateral flow immunosensor based on efficient energy transfer probe for point-of-care testing of tumor biomarkers

Fluorescence lateral flow immunoassay (LFA) has emerged as a powerful tool for rapid screening of various biomarkers owing to its simplicity, sensitivity and flexibility. It is noteworthy that fluorescent probe mainly determines the analytical performance of LFA. Due to the emission and excitation wavelengths are located in the visible region, most fluorophores are inevitably subject to light scattering and background autofluorescence. Herein, we reported a novel LFA sensor based on the second near-infrared (NIR-II) fluorescent probe with excellent anti-interference capability. The designed NIR-II probe was the Nd3+ and Yb3+ doped rare earth nanoparticles (RENPs) by employing Nd3+ as energy donor and Yb3+ as energy acceptor, which of the donor-acceptor energy transfer (ET) efficiency reached up to 80.7 %. Meanwhile, relying on the convenient and effective encapsulation strategy of poly(lactic-co-glycolic acid) (PLGA) microspheres to RENPs, the surface functionalized NIR-II probe (RE@PLGA) was obtained for subsequent bioconjugation. Benefiting from the optical advantages of NIR-II probe, this proposed NIR-II LFA displayed a good linear relationship ranging from 7 ng/mL to 200 ng/mL for the detection of α-fetoprotein (AFP), an important biomarker of hepatocellular carcinoma (HCC). The limit of detection (LOD) was determined as low as 3.0 ng/mL, which was of 8.3 times lower than clinical cutoff value. It is promising that LFA sensor based on this efficient RENPs probe provides new opportunities for high sensitive detection of various biomarkers in biological samples.

Oxygen Vacancies-Induced Antifouling Photoelectrochemical Aptasensor for Highly Sensitive and Selective Determination of α-Fetoprotein.

Accurate measurement of cancer markers in urine is a convenient method for tumor monitoring. However, the concentration of cancer markers in urine is so low that it is difficult to achieve their measurement. Photoelectrochemical (PEC) sensors are a promising technology to realize the detection of trace cancer markers due to their high sensitivity. Currently, the interference of nonspecific biomolecules in urine is the main reason affecting the high sensitivity and selectivity of PEC sensors in detecting cancer markers. In this work, a strategy of oxygen vacancy (OV) modulation is proposed to construct a fouling-resistant PEC aptamer sensing platform for the detection of α-fetoprotein (AFP), a liver cancer marker. The introduction of OVs induces the formation of intermediate localized states in the photoelectric material, which not only facilitates the separation of photogenerated carriers but also leads to the redshift of the light absorption edge. More importantly, OVs with positive electrical properties can be employed to modify the antifouling layer (C-PEG) with negatively charged groups through an electrostatic interaction. The synergistic effect of OVs, antifouling layer, and aptamer resulted in a TiO2/OVs/C-PEG-based PEC sensor achieves a wide linear range from 1 pg/mL to 100 ng/mL and a low detection limit of 0.3 pg/mL for AFP. In addition, the sensor successfully realized the determination of AFP in urine samples and accurately differentiated between normal people and liver cancer patients in the early and advanced stages. This project is of great significance in advancing the application of photoelectrochemical bioanalytical technology to achieve the detection of cancer markers in urine by investigating the construction of an OVs-regulated fouling-resistant sensing interface.

Construction of a Dual-Mode Immune Platform Based on the Photothermal Effect of AgCo@NC NPs for the Detection of α-Fetoprotein.

Compared with the accuracy of a single signal and the limitation of environmental applicability, the application value of dual-mode detection is gradually increasing. To this end, based on the photothermal effect of Ag/Co embedded N-rich mesoporous carbon nanomaterials (AgCo@NC NPs), we designed a dual-mode signal response system for the detection of α-fetoprotein (AFP). First, AgCo@NC NPs act as a photothermal immunoprobe that converts light energy into heat driven by a near-infrared (NIR) laser and obtains temperature changes corresponding to the analyte concentration on a hand-held thermal imager. In addition, this temperature recognition system can significantly improve the efficiency of Fenton-like reactions. AgCo@NC NPs act as peroxidase mimics to initiate the generation of poly N-isopropylacrylamide (PNIPAM, resistance enhancer) by cascade catalysis and the degradation of methylene blue (MB), thus enabling electrochemical testing. The dual-mode assay ranges from 0.01 to 100 and 0.001-10 ng/mL, with lower limits of detection (LOD) of 3.2 and 0.089 pg/mL, respectively, and combines visualization, portability, and high efficiency, opening new avenues for future clinical diagnostics and inhibitor studies.

Paper-based 3D SERS immunoassay array based on self-assembly of AuNBPs@Ag nanorods for ultrasensitive and highly stable detection of α-fetoprotein

Establishing a simple, sensitive, and accurate α-fetoprotein (AFP) detection methods is of great significance for the early diagnosis of hepatocellular carcinoma (HCC). Surface-enhanced Raman spectroscopy (SERS) has been identified as one of the most promising techniques for clinical monitoring. However, accurate detection of AFP is still challenging due to the poor stability of SERS substrate and the low abundance of AFP in the early stages of HCC. Herein, we developed an ultrasensitive and highly stable paper-based 3D SERS immunoassay array for AFP detection, combining the superior advantages of self-assembled AuNBPs@Ag nanorods, filter paper, and sandwich immunoassay. In the immunoassay array, 4-mercaptobenzoic acid (4-MBA) linked to the secondary antibody was employed as the Raman reporter, while the array modified with antibodies was used to capture AFP. The SERS immunoassay array sensor exhibited a wide linear range (3 pg mL−1 to 10 µg mL−1), low detection limit (0.086 pg mL−1), good specificity, and high signal reproducibility (RSD < 5 %). Meanwhile, the sensor is further used for accurate detection of trace AFP in serum, which paves an avenue for the fabrication of SERS substrates with high stability and provides a new outlook for their application in the early diagnosis of cancer.

A Chemiluminescence Sensor for the Detection of α-Fetoprotein and Carcinoembryonic Antigen Based on Dual-Aptamer Functionalized Magnetic Silicon Composite.

In this work, a dual-aptamer functionalized magnetic silicon composite was prepared and used to construct a chemiluminescence (CL) sensor for the detection of α-fetoprotein (AFP) and carcinoembryonic antigen (CEA). First, SiO2@Fe3O4 was prepared, and polydiallyl dimethylammonium chloride (PDDA) and AuNPs were sequentially loaded on SiO2@Fe3O4. Subsequently, the complementary strand of CEA aptamer (cDNA2) and the aptamer of AFP (Apt1) were attached to AuNPs/PDDA-SiO2@Fe3O4. Then, the aptamer of CEA (Apt2) and G quadruplex peroxide-mimicking enzyme (G-DNAzyme) were sequentially connected to cDNA2, leading to the final composite. Then, the composite was used to construct a CL sensor. When AFP is present, it will combine with Apt1 on the composite to hinder the catalytic ability of AuNPs to luminol-H2O2, achieving AFP detection. When CEA is present, it will recognize and bind with Apt2, so G-DNAzyme is released to solution and catalyzes the reaction of luminol-H2O2 to achieve CEA determination. After the application of the prepared composite, AFP and CEA were detected in the magnetic medium and supernatant, respectively, after simple magnetic separation. Therefore, the detection of multiple liver cancer markers is realized through the CL technology without additional instruments or technology, which broadens the application range of CL technology. The sensor for detecting AFP and CEA shows wide linear ranges of 1.0 × 10-4 to 1.0 ng·mL-1 and 0.0001-0.5 ng·mL-1 and low detection limits of 6.7 × 10-5 ng·mL-1 and 3.2 × 10-5 ng·mL-1, respectively. Finally, the sensor was successfully used to detect CEA and AFP in serum samples and provides great potential for detection of multiple liver cancer markers in early clinical diagnosis.

Label-free photoelectrochemical immunosensing of α-fetoprotein based on Eu-TiO2 nanocomposites sensitized with dye-encapsulated HMA.

In this study, a sensitive photoelectrochemical immunosensor with dye-enhanced anodic photocurrent response was proposed for sensitive detection of α-fetoprotein (AFP). Specifically, europium-doped TiO2 (Eu-TiO2) was used as the photoelectrochemical functional material and coated onto indium tin oxide (ITO) electrode. Doxorubicin (DOX) as an excellent fluorescent dye was encapsulated in the hydrophobically modified alginate (HMA). Then the dye-loaded HMA was modified onto the surface of Eu-TiO2 to further sensitize the photocurrent response. The results showed that the photoelectrical signal was enhanced and stabilized due to the effect of sensitization of DOX on Eu-TiO2 material. The constructed PEC sensor revealed a good linear response to AFP antigen ranging from 0.5 to 100ng/mL with a detection limit of 0.41pg/mL. The clinical patient's serum test results obtained from the proposed PEC immunosensor were consistent with those obtained from the commercial electrochemilunescence assay. The proposed PEC sensing method could be a promising analytical tool for the detection of AFP in clinical analysis.

A dual-channel biomarker detection based on spatiotemporal upconversion-linked immunosorbent assay

Multiplexed detection of different but clinically relevant low-abundance biomarkers is of paramount importance for early-stage disease diagnosis. Herein, we have developed a simple, yet versatile and sensitive upconversion-based sensing platform that leverages the excitation-controlled switchable optical properties of upconversion nanoparticles to achieve the simultaneous detection of α-fetoprotein (AFP) and human chorionic gonadotropin (hCG) biomarkers. The assay yielded a limit of detection of 7.81 pg/mL for AFP and 1.02 × 10−4 IU/mL for hCG in spiked serum. By utilizing the dual-channel luminescent signals as dual input, we have further developed an open-source software for automatic risk assessment of testicular cancer based on a dual-input logic OR gate. Due to the high optical tunability of upconversion luminescence, the technique and software present in this work should inspire new ideas for the early diagnosis of a wide range of diseases.

Recent advances in nanotechnology-enhanced biosensors for α-fetoprotein detection.

α-Fetoprotein (AFP) is a kind of fetal protein that is related to tumor, the increasing concentration of which gives birth to a large variety of diseases, such as liver cancer. Therefore, the detection method with super sensitivity, high selectivity, and less time consumption under trace concentrations in early stage of diseases is becoming a necessity. In recent years, nanomaterials have been regarded as significant resources for the exploration of efficient biosensors with high sensitivity, selectivity, speed, as well as simple process, due to their excellent optical, electrical, and chemical properties. In this paper, we reviewed the research progress of AFP biosensors with enhanced sensitivity and selectivity by nanoparticles. Representative examples have also been displayed in this paper to expound the nanotechnologies utilized in the early detection of AFP. Furthermore, challenges of the clinical application of AFP biosensors based on nanotechnology have been elaborated, as well as the development opportunity in this field in the future. This review provides a comprehensive overview on the various nano-biosensor for AFP detection based on functional nanotechnology.

All-covalent reduced graphene oxide FET immunosensor optimized by interface engineering

Immunosensors with antigen-antibody specific binding exhibit broad application prospects due to their excellent specificity and label-free high-sensitivity detection characteristics. However, it's still a challenge to construct a stable biosensing interface to covalently attach bio-probe, avoiding interference from other substances. Therefore, an all-covalent reduced graphene oxide-based field-effect transistor (RGO-FET) immunosensor was successfully developed, where the reduced graphene oxide active layer was interface modified by cross-linking agent 1-pyrenebutanoicacid, 2,5-dioxo-1-pyrrolidinylester after optimization of its concentration. Then, α-fetoprotein antibody was covalently bonded to construct a high-performance biosensing platform for tumor marker α-fetoprotein detection. In addition, the prepared RGO-FET based immunosensor was blocked with ethanolamine blocking agent, which reduced the influence of non-specific adsorption during α-fetoprotein detection. Through interface engineering design, the immunosensor based on RGO-FET exhibits good sensing performance for α-fetoprotein bioassay and is expected to be applied for various biomarkers detection.

Hand-Operated, Paper-Based Rotational Vertical-Flow Immunosensor for the Impedimetric Detection of α-Fetoprotein.

This study demonstrates a hand-operated, paper-based rotational vertical-flow immunosensor (rotational VFI) platform requiring fewer pipetting steps, designed for the electrochemical detection of α-fetoprotein with multiple and time-sequenced steps. The platform allows users to perform electrochemical measurements without interference from the convective component of fluid motion, which is unfavorable in most techniques. Users can freely transfer-switch-stop fluid flows by manually rotating the paper disk, evidencing the superior flexibility of this sensor compared to other biosensors. Furthermore, the overall assay duration can be considerably shortened to 9 min. The linear range (LR) is determined to be 0.01-500 ng/mL, with a limit of detection (LOD) of 1.65 pg/mL, and the sensitivity can be significantly enhanced simply by switching off the sample stream to ensure detention at the binding zone (for up to 30 min). This additional step can widen the LR to 0.5 pg/mL, with a LOD of 3.54 fg/mL, which is the lowest detectable level ever reported among paper-based sensors. The advantages of the designed rotational VFI qualify it as a suitable alternative to various biosensors.

Development of an Efficient Immunosensing Platform by Exploring Single-Walled Carbon Nanohorns (SWCNHs) and Nitrogen Doped Graphene Quantum Dot (N-GQD) Nanocomposite for Early Detection of Cancer Biomarker.

In this work, a novel electrochemical immunosensor based on nitrogen doped graphene quantum dot (N-GQD) and single-walled carbon nanohorns (SWCNHs) was developed for the detection of α-fetoprotein (AFP), a cancer biomarker. Thus, to fabricate the platform of the immunosensor, nanocomposite architecture was developed by decorating N-GQD on the surface of the SWCNHs. The resulting hybrid architecture (N-GQD@SWCNHs) functioned as an exceptional base for the immobilization of antibody (Anti-AFP) through carbodiimide reaction with good stability and bioactivity. The immunosensor was prepared by evenly distributing the bioconjugates (N-GQD@SWCNHs/Anti-AFP) dispersion on the surface of the glassy carbon electrode, and subsequently blocking the remaining active sites by bovine serum albumin to prevent the nonspecific adsorption. Cyclic voltammetry and electrochemical impedance spectroscopy technique was employed to investigate the assembly process of the immunosensor. Under optimal conditions, the immunosensor exhibited a broad dynamic range in between 0.001 ng/mL to 200 ng/mL and a low detection limit of 0.25 pg/mL. Furthermore, the sensor showed high selectivity, desirable stability, and reproducibility. Measurements of AFP in human serum gave outstanding recovery within 99.2% and 102.1%. Thus, this investigation and the amplification strategy exhibited a potential role of the developed nanocomposite based sensor for early clinical screening of cancer biomarkers.

A dual-signal self-checking photoelectrochemical immunosensor based on the sole composite of MIL-101(Cr) and CdSe quantum dots for the detection of α-fetoprotein

Designing a photoelectrochemical (PEC) immunosensor that can produce dual photocurrent signals which can refer to each other is a great importance but a big challenge. In this manuscript, a novel dual photocurrent signals immunosensor was constructed for the detection of α-fetoprotein (AFP). Unlike the usual method of using two composite materials to provide cathode and anode photocurrent respectively, this work applies only one compound of MIL-101 (Cr) and CdSe quantum dots (QDs). Thereinto, we found that the photocurrent polarity of MIL-101(Cr) would switch by adjusting applied voltage. And then CdSe QDs was introduced by simple ultrasound mixing to boost the dual photocurrent signals. Furthermore, in the composite of M&C, the electron transfer path between MIL-101(Cr) and CdSe QDs may switch between “Z-type” and “Ⅱ-type” by adjusting voltage. Benefiting by the dual signals, the proposed sensor can not only perform sensitively quantitative detection of α-fetoprotein (AFP), but also can intuitively estimate the accuracy and reliability of the test result by determining whether the corresponding relationship of “cathode photocurrent-analyte concentration-anode photocurrent” is established. The linear ranges of the sensing electrodes as cathode and anode are the same, both from 0.1 to 300 ng mL−1. The limit of detection (LOD) is 0.082 ng mL−1 (S/N = 3) when it used as an anode, and the LOD is 0.054 ng mL−1 (S/N = 3) when it served as cathode. Furthermore, this sensor showed acceptable stability, reproducibility, specificity, and feasibility of detecting AFP in human serum, which has broad development prospects in the early clinical diagnosis.

Metal Nanoparticles/MoS2 Surface-Enhanced Raman Scattering-Based Sandwich Immunoassay for α-Fetoprotein Detection.

The detection of cancer biomarkers at an early stage of tumor development is vital for effective diagnosis and treatment of cancer. Current diagnostic tools can often detect cancer only when the biomarker levels are already too high, so that the tumors have spread and treatments are less effective. It is urgent therefore to develop highly sensitive assays for the detection of such biomarkers at the lowest possible concentration. In this context, we developed a sandwich immunoassay based on surface-enhanced Raman scattering (SERS) for the ultrasensitive detection of α-fetoprotein (AFP), which is typically present in human serum as a biomarker indicative of early stages of hepatocellular carcinoma. In the immunoassay design, molybdenum disulfide (MoS2) modified with a monoclonal antibody was used as a capture probe for AFP. A secondary antibody linked to an SERS-encoded nanoparticle was employed as the Raman signal reporter, that is, the transducer for AFP detection. The sandwich immunocomplex “capture probe/target/SERS tag” was deposited on a silicon wafer and decorated with silver-coated gold nanocubes to increase the density of “hot spots” on the surface of the immunosensor. The developed SERS immunosensor exhibits a wide linear detection range (1 pg mL–1 to 10 ng mL–1) with a limit of detection as low as 0.03 pg mL–1 toward AFP with good reproducibility (RSD < 6%) and stability. These parameters demonstrate that the proposed immunosensor has the potential to be used as an analytical platform for the detection of early-stage cancer biomarkers in clinical applications.

Differential expression of long noncoding RNA in hepatocellular carcinoma on top of chronic HCV and HBV infections.

Aim of the studyThe task of long noncoding RNAs (lncRNAs) as a prospective goal for hepatocellular carcinoma (HCC) is a candidate for research. Several lncRNAs are involved in signal transduction, directing gene expression and epigenetic alteration in normal and cancer cells. Dysregulation of diverse lncRNAs has been involved in the pathogenesis and progression of different cancers including HCC. We aimed to investigate the differential expression of lncRNAs (aHIF, hPVT1, ANRIL) in HCC on top of chronic hepatitis C virus (HCV) and hepatitis B virus (HBV) infections.Material and methods182 participants were included: 85 patients with HCC in addition to 50 patients with cirrhosis on top of chronic HCV or HBV, and 47 healthy subjects as controls. HCC was diagnosed by triphasic computed tomography (CT). Detection of α-fetoprotein (AFP) and serological markers of HCVAb and HBsAg by enzyme-linked fluorescent immunoassay (ELFA) and quantitation of lncRNAs by real time PCR were applied.ResultsUpregulation of ANRIL and hPVT1 and downregulation of aHIF were observed in patients with HCC on top of HCV and HBV vs. controls. Circulating aHIF could be of major diagnostic importance to discriminate HCC on top of HCV from cirrhotic patients with sensitivity 86.67% and specificity 91.89% whereas circulating hPVT1 had sensitivity 85.0% and specificity 84.62%; moreover ANRIL had AUC 0.902 and could discriminate HCC on top of HBV from cirrhotic patients.ConclusionsThe differential expression of lncRNAs (ANRIL, hPVT1 and aHIF) might be of major worth in predicting the occurrence of HCC in cirrhotic patients related to chronic viral hepatitis and could be beneficial in the early management.

Highly sensitive immunosensor based on polydopamine-nanofilm modified 3D gold nanoelectrode for α-fetoprotein detection

The sensitivity and selectivity of the electrochemical immunosensor (ECIS) are the key aspect for the biomolecular detection of ultratrace tumor markers. Here we fabricated a novel ECIS for the detection of tumor marker α-fetoprotein (AFP) by a dual electrochemical signal amplification strategy involving 3D gold nanowire electrode (3D-GNE) and recycling redox polydopamine (PDA) nanofilm on 3D-GNE (PDA-3D-GNE). The electrochemical signal was first amplified by depositing Au nanowires on the bare electrode, the as-prepared 3D-GNE possessed a quadrupled active area, 2.6 times increase in oxidation current and fast electron transfer ability. The electrochemical signal was further amplified by reversible redox PDA nanofilm on 3D-GNE, which achieved a sixfold increase in capacitance, excellent binding strength to antibody (Ab) and great biocompatibility. The electrochemical performance and interfacial kinetic property of the immunosensor were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The optimized AFP ECIS exhibited a wide linear range from 0.1 pg·mL−1 to 50 ng·mL−1, a low detection limit of 0.01 pg·mL−1, excellent stability and reproducibility as well as selectivity. Furthermore, it was successfully demonstrated to work well for analyzing AFP in complex real human serum samples.

Reducing background absorbance via a double-lock strategy for detection of alkaline phosphatase and α-fetoprotein.

Lowering the background signal for more sensitive analysis of determinands is as important as amplifying thetarget signal. The photoinduced oxidase of fluorescein has been reported, which can catalyze the oxidization of common substrates in a few minutes. As a metaphor for locks and keys, we designed double locks confining the activity of fluorescein to reduce the background absorbance during colorimetric detection. The first lock inhibits the main activity of fluorescein by phosphating. The second lock almost completely deactivates fluorescein by forming coordination nanoparticles (CNPs) via the self-assembly of cerium chloride and fluorescein diphosphate (FDP). The Ce-FDP CNPs are characterized by scanning electron microscope (SEM), dynamic light scattering (DLS), Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectrum (EDS), which show electrostatic formation and amorphous characterin the morphology. Alkaline phosphatase (ALP), the key to release fluorescein, can destroy Ce-FDP CNPs along with decomposing FDP by degrading phosphate groups. Therefore, a novel colorimetric strategy for sensitive detection of ALP is established. The detection of α-fetoprotein (AFP) is further succeeded by labeling AFP antibody with ALP. By dramatically reducing the background absorbance, the detection limits of ALP and AFP are as low as 0.014mU/mL and 0.023ng/mL, respectively. This convenient, brief, sensitive assay provides a promising prospect for clinical diagnosis. Graphical abstract.