Detection Of Alpha-fetoprotein Research Articles

Three-dimensional nitrogen-doped mesoporous carbon nanomaterials derived from plant biomass: Cost-effective construction of label-free electrochemical aptasensor for sensitively detecting alpha-fetoprotein

We synthesized three kinds of nitrogen-doped nanoporous carbon nanomaterials (represented by N-mC) through a cost-effective method, that is, pyrolysis of plant biomasses (grass, flower, and peanut shells). We further explored their potential as sensitive bioplatforms for electrochemical label-free aptasensors to facilitate the early detection of alpha-fetoprotein (AFP). Chemical structure characterizations revealed that rich functional groups coexisted in as-synthesized N-mC nanomaterials, such as C-C, C-O, C=O, C-N, and COOH. Among the three kinds of N-mC nanomaterials, the one derived from grass (N-mCg) exhibited the lowest carbon defect degree, the highest ID/IG ratio in the Raman spectra, and the largest specific surface area (186.2 m2 g−1). Consequently, N-mCg displayed excellent electrochemical activity and strong affinity toward aptamer strands, further endowing the corresponding aptasensor with sensitive detection ability for AFP. Electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) were used to investigate the whole detection procedure for AFP. The EIS and DPV results showed that the fabricated N-mCg-based aptasensor possessed an extremely low limit of detection of 60.8 and 61.8 fg·mL−1 (s/n = 3), respectively, for detecting AFP within a wide linear range from 0.1 pg mL−1 to 100 ng mL−1. Moreover, the aptasensor displayed acceptable selectivity and applicability, high reproducibility, and excellent stability in serum samples of cancer patients. Therefore, the proposed cost-effective and label-free strategy based on the nitrogen-doped nanoporous carbon derived from plant biomass is a promising approach for the early detection of various tumor markers.

A fluorometric aptamer nanoprobe for alpha-fetoprotein by exploiting the FRET between 5-carboxyfluorescein and palladium nanoparticles.

Alpha-fetoprotein (AFP) is a reliable clinical marker of hepatocellular carcinoma (HCC). A highly sensitive fluorometric aptamer nanoprobe is described for AFP detection. It is based on fluorescence resonance energy transfer (FRET) between AFP aptamer labelled with 5-carboxyfluorescein (FAM) and palladium nanoparticles (PdNPs). The PdNPs quench the green fluorescence of the FAM-AFP aptamer via interactions between nitrogen functional groups of the AFP aptamer and PdNPs. When AFP was introduced into the FAM-AFP aptamer-PdNPs FRET system, the AFP aptamer preferentially combines with AFP. This results in a conformational change and weakens the interaction between the aptamer and the PdNPs. Thus, the fluorescence of FAM recovers. The fluorescence recovery of FAM increases linearly in the 5.0-150ng·mL-1 AFP concentration range and has a 1.4 ng·mL-1 detection limit. The assay was applied to the analysis of spiked diluted human serum. The recovery values ranged from 98.3 to 112.9%, with relative standard deviations of <1.1%. This biosensing strategy provides a reliable and ultrasensitive protocol for the quantification of biomarkers with relevant antigens and aptamers. Graphical abstract Schematic presentation of a fluorometric aptamer nanoprobe for AFP assay based on fluorescence resonance energy transfer (FRET) between AFP aptamer labelled with 5-carboxyfluorescein (FAM) and palladium nanoparticles (PdNPs).

Dually functional polyethylenimine-coated gold nanoparticles: a versatile material for electrode modification and highly sensitive simultaneous determination of four tumor markers.

A novel sandwich-type electrochemical multiplex immunoassay is described for simultaneous detection of the tumor biomarkers alpha fetoprotein (AFP), carcinoembryonic antigen (CEA), prostate-specific antigen (PSA) and interleukin-8 (IL-8). Polyethylenimine-coated gold nanoparticles (PEI-AuNPs) were used for both modification of a screen-printed carbon electrode (SPCE) and as labeling tags. The coated AuNPs can be easily adsorbed on the electrodes which also areloaded with the electroactive metal ions cadmium(II), lead(II) copper(II) and silver(I) and related secondary antibodies (Ab2). These give distinct voltammetric signals at -0.80, -0.55, -0.20 and + 0.05V, respectively (vs Ag/AgCl). Four corresponding capture antibodies (Ab1) were then conjugated to one of the electrodes. After a sandwich-type structure was formed by binding of the analytes and the labeling AuNPs, the electrochemical signal responses were recorded. Under the optimized testing conditions, there is a linear relationship in range from 0.25-10ngmL-1 for AFP, CEA and PSA, and from 0.50-100pgmL-1 for IL-8. The corresponding detection limits are 1.7, 1.6, 0.9 and 1.0fgmL-1, respectively. Cross reactivity, interferences and stability of the modified electrodes and of the signal nanotags are satisfying in that they can be stored for >4weeks without significant signal reduction. The method was successfully applied to the determination of the biomarkers in spiked human serum. Graphical abstract Poly(ethylenimine)-coated gold nanoparticles were used in a sandwich-type multiplex electrochemical immunosensor. Thecoated gold nanoparticles were used for both electrode modification and aselectrochemical nanotags. The resultingvmmunosensor exhibits excellent sensitivity for the four analytes studied,and also displaysselectivity and long-term stability.

Sandwich-type electrochemical immunosensor based on Au@Pt DNRs/NH2-MoSe2 NSs nanocomposite as signal amplifiers for the sensitive detection of alpha-fetoprotein

A sandwich-type electrochemical immunosensor was fabricated for the quantitation of alpha fetoprotein (AFP). To this end, the Au@Pt dendritic nanorods loaded with amino functionalized molybdenum selenide nanosheets (Au@Pt 41 DNRs/NH2-MoSe2 NSs) with enhanced peroxidase-like properties were selected as the secondary antibody label (Ab2) to achieve signal amplification. The as-obtained Au@Pt DNRs/NH2-MoSe2 NSs exhibited better catalytic activity toward hydrogen peroxide reduction and offered rich anchors for bioconjugation. Meanwhile, gold nanoparticles anchored on an amino functionalized graphene (Au NPs/NH2-GS) composite with admirable conductivity and biocompatibility was used as the matrix material to improve sensitivity. Under optimal conditions, amperometric current responses had a good linear relationship with the logarithm values of AFP concentration in the range 10 fg mL–1 to 200 ng mL–1 with a detection limit of 3.3 fg mL–1 (S/N = 3). Additionally, the immunosensor had excellent reproducibility, selectivity, and stability, which indicated superior performance for AFP detection compared with previous reports. The satisfactory results of human serum samples analysis showed that the designed immunosensor has potential applicability for the sensitive detection of other tumor markers.

Development and potential application of a simultaneous multiplex assay of Golgi protein 73 and alpha-fetoprotein for hepatocellular carcinoma diagnosis.

Detecting a single serum marker, such as Golgi protein 73 (GP73) or alpha-fetoprotein (AFP), may not meet the requirements for the early diagnosis of hepatocellular carcinoma (HCC) due to low sensitivity and specificity. Therefore, this study aimed to develop a simultaneous multiplex assay of GP73 and AFP. Anti-human GP73- and AFP-coupled microsphere beads and biotin-labeled detectable antibodies were prepared to develop a multiplex assay of GP73 and AFP using the Luminex xMAP technology. The assay was evaluated for cross-reactivity, standard curve, sensitivity, range of detection, and precision. Additionally, the assay was used to determine the levels of serum GP73 and AFP in healthy controls and patients with chronic hepatitis, liver cirrhosis, and HCC. The multiplex assay was successfully developed to simultaneously detect GP73 and AFP without cross-reactivity. The sensitivity for GP73 detection was 0.215 ng/mL and that for AFP detection was 0.666 ng/mL. The ranges of GP73 and AFP detection were 0.98-861.08 ng/mL and 2.01-1848.73 ng/mL, respectively. The intra- and inter-assay coefficients of variation (CVs) were <10%, indicating good precision, with recovery rates of 75-125%. The levels of serum GP73 in healthy controls, chronic hepatitis patients, liver cirrhosis patients, and HCC patients were 61.64 ± 30.60 ng/mL, 208.4 ± 99.42 ng/mL, 183.7 ± 82.78 ng/mL, and 214.1 ± 160.5 ng/mL, respectively. The levels of serum AFP in healthy controls, chronic hepatitis patients, liver cirrhosis patients, and HCC patients were 24.87 ± 14.52 ng/mL, 134.4 ± 216.5 ng/mL, 66.45 ± 133.4 ng/mL, and 891.4 ± 1278 ng/mL, respectively. The receiver operating characteristic (ROC) results showed that the area under the curves (AUC) for the combination of GP73 and AFP was 0.972, which was larger than the AUC for each marker. The sensitivity and specificity of the combined detection of GP73 and AFP for the diagnosis of HCC were 90.91% and 98.86%, respectively. The multiplex assay demonstrated a good correlation with enzyme-linked immunosorbent assay (ELISA), with correlation coefficients of 0.818 and 0.982 for GP73 (p<0.001) and AFP (p<0.001), respectively. A multiplex assay for the simultaneous detection of GP73 and AFP with high sensitivity and accuracy was developed for the diagnosis of HCC. This assay may provide a reliable reference for the early diagnosis of HCC.

Simultaneous voltammetric immunodetection of alpha-fetoprotein and glypican-3 using a glassy carbon electrode modified with magnetite-conjugated dendrimers.

The authors describe an electrochemical immunoassay for simultaneous determination of alpha-fetoprotein (AFP) and glypican-3 (GPC-3) which are important biomarkers for early detection of hepatocellular carcinoma (HCC). Magnetite (Fe3O4) nanoparticles (NPs) were decorated with hyperbranched amino functionalized dendrimers. The modified NPs were coupled to the antibodies against AFP and GPC-3. The electrochemical behaviour of the Fe3O4 NPs and dendrimer-modified NPs were studied. A glassy carbon electrode was then modified with the NP-conjugated antibodies and biomolecular interactions were studied by using cyclic voltammetry and electrochemical impedance spectroscopy. Dual differential pulse voltammetric sensing was performed by utilizing the redox probes; Prussian blue for AFP and toluidine blue for GPC-3. The biomarkers can be detected best at voltages of 0.25mV and - 0.54mV (vs Ag/AgCl) for AFP and GPC-3, respectively. The low working potentials makes the method more selective over other electroactive species present in real human serum samples. Response is linear in 0.02 to 10ngmL-1 concentration ranges of both AFP and GPC-3; and the respective detection limits are 50 and 70pgmL-1. The method was validated by analysing spiked human serum samples. In our perception, the method is of great clinical significance as combination of GPC-3 and AFP increases the sensitivity of detection of HCC. Graphical abstract Schematic presentation of polyamidoamine (PAMAM) dendrimers modified magnetite (Fe3O4) nanoparticles as electrochemical sensing platform using redox dyes Prussian blue and toluidine blue for simultaneous detection of alpha-fetoprotein (AFP) and glypican-3 (GPC-3), respectively by differential pulse voltammetry.

A label-free electrochemical immunosensor based on rhombic dodecahedral Cu3Pt nanoframes with advanced oxygen reduction performance for highly sensitive alpha-fetoprotein detection

Herein, rhombic dodecahedral Cu3Pt nanoframes (Cu3Pt NFs) were prepared via solvothermal strategy using theobromine as the reductant and structure-directing agent, coupled with cetyltrimethylammonium chloride (CTAC) as the co-structure-director. The samples showed dramatically boosted catalytic performance for oxygen reduction reaction (ORR), owing to their highly open structures with enlarged specific surface areas. Using Cu3Pt NFs catalyzed ORR as signal amplification platform, a novel electrochemical immunosensor was constructed to monitor alpha-fetoprotein (AFP). The as-fabricated immunosensor displayed a wide linear range of 0.1–104 pg mL–1 and a low detection limit of 0.033 pg mL–1.

Electrochemical immunosensors with AuPt-vertical graphene/glassy carbon electrode for alpha-fetoprotein detection based on label-free and sandwich-type strategies

We proposed label-free and sandwich-type electrochemical immunosensors for the quantification of alpha-fetoprotein (AFP), which plays a critical role in the early diagnosis of primary liver cancer. Both detection strategies involved monitoring of the electrochemical response current of the AuPt-vertical graphene (VG)/glassy carbon electrode (GCE) for the oxidation of the redox probe, methyl orange. AuPt nanoparticles, which have good biocompatibility and excellent conductivity, were used to immobilize the primary antibody, Ab1, while VG sheets helped accelerate electron transfer at the liquid-solid and solid-solid interfaces. The sensing electrode played a key role in signal amplification, and the sensitivity of the sandwich-type sensor was higher than that of the label-free sensor. The former exhibited a wide linear range from 1 fg mL−1 to 100 ng mL−1 and a low detection limit of 0.7 fg mL−1 under the optimal experimental conditions. The excellent performance of the AuPt-VG/GCE-based immunosensors in AFP detection in human serum, coupled with their good stability, makes them promising tools for the clinical monitoring of AFP and other tumor markers.

An aptamer-based four-color fluorometic method for simultaneous determination and imaging of alpha-fetoprotein, vascular endothelial growth factor-165, carcinoembryonic antigen and human epidermal growth factor receptor 2 in living cells.

The extraordinary fluorescence quenching capability of graphene oxide (GO) was coupled to the specific recognition capability of aptamers to design a four-color fluorescent nanoprobe for multiplexed detection and imaging of tumor-associated proteins in living cells. Specifically, alpha-fetoprotein (AFP), vascular endothelial growth factor-165 (VEGF165), carcinoembryonic antigen (CEA), and human epidermal growth factor receptor 2 (HER2) were detected. Due to strong π interaction, the fluorescence of labeled aptamers is quenched by GO. Four fluorophore-labeled aptamers that bind the tumor-associated proteins were adsorbed on GO to form the four-color nanoprobe with quenched fluorescence. The nanoprobes were internalized into cells via endocytosis, where the aptamer/GO nanoprobes bind the intracellular tumor-associated proteins. The aptamer-protein complexes thus formed detach from GO, and fluorescence recovers. Each analyte has its typical color (AFP: blue; VEGF165: green; CEA: yellow; HER2: red). As a result, simultaneous detection and imaging of multiple tumor-associated proteins in living cells were achieved. This nanoprobe has a fast response and is highly specific and biocompatible. The linear ranges for AFP, VEGF165, CEA, and HER2 are 0.8nM-160nM, 0.5nM-100nM, 1.0nM-200nM, and 1.2nM-240nM, respectively. Detection limits were 0.45nM for AFP, 0.30nM for VEGF165, 0.62nM for CEA, and 0.96nM for HER2. The probe allows for a fast distinction between tumor cells and normal cells via imaging. Graphical abstract Schematic presentation of the development of a four-color fluorometic method based on aptamer and graphene oxide for simultaneous detection and imaging of alpha-fetoprotein, vascular endothelial growth factor-165, carcinoembryonic antigen and human epidermal growth factor receptor 2 in living cells.

Near-infrared-light-triggered photoelectrochemical biosensor for detection of alpha-fetoprotein based on upconversion nanophosphors

A novel photoelectrochemical (PEC) biosensor based on hybrids of NaYF4:Yb, Tm, zinc oxide (ZnO) and cadmium sulfide (CdS) was constructed to detect alpha-fetoprotein (AFP), which possesses the advantages of low background noise and non-damage to the biological substance. Herein, we prepared NaYF4:Yb,Tm/ZnO/CdS composite film electrode by pulsed laser deposition. The selected materials of ZnO and CdS can make full use of the upconversion luminescence (˜360 nm, ˜480 nm) of NaYF4:Yb,Tm nanophosphors under 980 nm laser excitation. Meanwhile, an effective matching of energy levels between the conduction bands of CdS and ZnO can prompt photoelectrochemical performance of the electrode. The biosensor shows ultrasensitive detection of AFP with a wide linear range from 0.01 ng mL−1 to 200 ng mL−1 and a low detection limit of 5 pg mL−1. Therefore, the proposed PEC biosensor based on upconversion nanophosphors is potentially attractive for achieving excellent photoelectrochemical biosensor for detection of other cancer markers in clinical analysis.

A sensitive label-free immunosensor for alpha fetoprotein detection using platinum nanodendrites loaded on functional MoS2 hybridized polypyrrole nanotubes as signal amplifier

Sensitive detection of alpha fetoprotein (AFP) in serum is an important prerequisite to prompt definitive treatment decisions for reducing mortality rate of hepatocellular carcinoma. In this study, a label-free amperometric immunosensor was developed to detect AFP sensitively. It was based on platinum nanodendrites loaded on poly(diallyldimethylammonium chloride) functionalized molybdenum disulfide nanosheet hybridized polypyrrole nanotubes (Pt NDs/PDDA/MoS2@PPy NTs). The Pt NDs and MoS2 nanosheet improved the catalytic activity, PPy NTs and PDDA increased electron transfer and enhanced the stability. The Pt NDs/PDDA/MoS2@PPy NTs nanocomposite also had large active surface area and immobilized antibodies effectively. Therefore, the nanocomposite showed high catalytic activity, enhancing the electron transfer and immobilizing antibodies effectively, which amplified the current signal. Based on above advantages, the immunosensor had low detection limit of 17fgmL−1, wide linear concentration range from 50fgmL−1 to 50ngmL−1 for AFP (signal-to-noise ratio of 3), good reproducibility, selectivity and stability. The good analysis results of human serum samples implied that the immunosensor had bright potential application in clinical monitoring biomarkers.

Growth of Spherical Gold Satellites on the Surface of Au@Ag@SiO2 Core-Shell Nanostructures Used for an Ultrasensitive SERS Immunoassay of Alpha-Fetoprotein.

The identification and detection of cancer biomarkers in early stages is an important issue for the therapy of cancer. However, most methods are time-consuming and have limited sensing sensitivity and specificity. In this work, we prepared a novel plasmonic multilayered core-shell-satellite nanostructure (Au@Ag@SiO2-AuNP) consisting of a gold nanosphere with a silver coating core (Au@Ag), an ultrathin continuous silica (SiO2) shell, and a high coverage of gold nanosphere (AuNP) satellites. The Au@Ag core is a prominent surface enhanced Raman scattering (SERS) platform, and the thin SiO2 layer exhibits a long-range plasmon coupling between the Au@Ag core to the AuNP satellites, further leading to enhanced Raman scattering. Meanwhile, the outer AuNP satellites have a high biocompatibility and long-term stability. Combining the above advantages, the well-designed metallic nanoassemblies would be a promising candidate for SERS-based applications in biochemistry. For specific detection of alpha-fetoprotein (AFP), we utilized the SERS-active core-shell-satellite nanostructures modified with AFP antibody as immune probes and nitrocellulose membrane (NC) stabilized captured anti-AFP antibodies as solid substrate. To improve the detection performance, we further systematically optimized the parameters, including the silver coating thickness of the Au@Ag core and the density and size of the satellite AuNPs. Under the optimized conditions, AFP could be detected by the SERS-based sandwich immunoassay with an ultralow detection limit of 0.3 fg/mL, and the method exhibited a wide linear response from 1 fg/mL to 1 ng/mL. The limit of detection (LOD) was considerably lower than conventional methods in the literature. This work relies on the unique Au@Ag@SiO2-AuNP nanostructures as the immune probe develops a new outlook for the application of multilayered nanoassemblies and demonstrates the great potential in early tumor marker detection.

An fluorescent aptasensor for sensitive detection of tumor marker based on the FRET of a sandwich structured QDs-AFP-AuNPs

The detection of alpha-fetoprotein (AFP) is of great importance for hepatocellular carcinoma (HCC) diagnosis, but it needs to be further improved because of poor sensitivity and complicated operating steps. In this paper, a simple and sensitive homogeneous apatasensor for AFP has been developed based on Förster resonance energy transfer (FRET) where the AFP aptamer labeled luminescent CdTe quantum dots (QDs) as a donor and anti-AFP antibody functional gold nanoparticles (AuNPs) as an acceptor. In the presence of AFP, the bio-affinity between aptamer, target, and antibody made the QDs and AuNPs close enough, thus the fluorescence of CdTe QDs quenched though the FRET between QD and AuNP. The fluorescent aptasensor for AFP showed a concentration-dependent decrease of fluorescence intensity in the low nanomolar range and a detecting linear range of 0.5–45 ng mL−1, with a detection limit of 400 pg mL−1. Moreover, this homogeneous aptasensor is simple and reliable, and obtained satisfying results for the detection of AFP in human serum samples. With more and more aptamers for biomarkers have been selected gradually, this approach could be easily extended to detection of a wide range of biomarkers. The proposed aptasensor has great potential for carcinoma screening in point-of-care testing and even in field use.

Prussian blue nanoparticle-labeled aptasensing platform on graphene oxide for voltammetric detection of α-fetoprotein in hepatocellular carcinoma with target recycling.

An enzyme-free electrochemical aptasensing platform based on a graphene oxide nanosheet-modified gold-disk electrode was developed for the voltammetric detection of alpha-fetoprotein (AFP) in hepatocellular carcinoma by using a Prussian blue nanoparticle (PBNP)-labeled aptamer. The electroactive PBNP, a typical signal-generation tag, was utilized for the labeling of the aminated AFP aptamer by using covalent conjugation. The electrochemical sensing platform was prepared in a simple manner on the basis of a π-π stacking reaction between the immobilized graphene oxide and the PBNP-labeled AFP aptamer. Upon target AFP introduction, the analyte reacted with the aptamer, thus resulting in the dissociation of the PBNP from the nanosheets. In the presence of DNase I, the newly formed AFP/aptamer-PBNP complex was cleaved to release target AFP, which could react again with the aptamer on the nanosheets, thereby causing target recycling. During this process, the cleaved PBNP-aptamer was far away from the electrode to decrease the voltammetric signal. Under optimum conditions, the voltammetric peak current of the modified electrode decreased with the increment of the target AFP concentration within the linear range of 0.01-300 ng mL-1 at a low detection limit of 6.3 pg mL-1. The precision and reproducibility of the aptasensing protocol were acceptable (CV: <15% for intra-assay and inter-assay). Other possible nontarget biomarkers did not interfere significantly with the voltammetric signal of this system. Human serum samples containing target AFP were assayed with electrochemical aptasensing and a commercial human AFP ELISA kit, and gave well-matched results from these two methods. Importantly, our strategy provides a new horizon for the determination of disease-related proteins.

A multifunctional self-healing G-PyB/KCl hydrogel: smart conductive, rapid room-temperature phase-selective gelation, and ultrasensitive detection of alpha-fetoprotein.

A multifunctional G-PyB/KCl hydrogel showed outstanding self-healability, high conductivity, and rapid room-temperature phase-selective gelation capacity, and was developed as an electrochemical aptamer sensing platform for the ultrasensitive detection of alpha-fetoprotein.

Magneto-controlled flow-injection device for electrochemical immunoassay of alpha-fetoprotein on magnetic beads using redox-active ferrocene derivative polymer nanospheres.

A new electrochemical immunosensing protocol by coupling with a magneto-controlled flow-through microfluidic device was developed for the sensitive detection of alpha-fetoprotein (AFP) on magnetic beads (MB) using ferrocene derivative polymer nanospheres (FDNP) as the electroactive mediators. The immunosensing probe was prepared by covalent conjugation of monoclonal mouse anti-human AFP antibodies with magnetic beads, while the recognition element was constructed by means of immobilizing polyclonal rabbit anti-human AFP antibodies on the redox FDNP. Upon target AFP introduction, the sandwich-type immunoreaction was carried out between the immunosensing probe and the recognition element, and the formed immunocomplex was captured in the detection cell with an external magnet. Ferrocene polymer nanospheres synthesized by infinite coordination polymerization were utilized as the signal-generation tags during the electrochemical measurement. Under optimal conditions, the magneto-controlled flow-through immunosensing platform exhibited good electrochemical responses toward target AFP within a dynamic working range of 0.01-100 ng mL-1 and with a low detection limit of 5.7 pg mL-1. The nanoparticles-based sensing systems also gave good reproducibility, high specificity and long-term stability. Moreover, our strategy displayed well-matched accuracy for the analysis of human serum specimens relative to commercial Roche 2010 Electrochemiluminescence (ECL) Automated Analyzer.

A biomimetic fluorescent nanosensor based on imprinted polymers modified with carbon dots for sensitive detection of alpha-fetoprotein in clinical samples.

A biomimetic fluorescent nanosensor based on molecularly imprinted polymers modified with carbon dots (CDs@MIPs) has been prepared for rapid, selective and sensitive detection of alpha-fetoprotein (AFP) in clinical samples. The nanosensor was produced using vinyl-functionalized CDs (V-CDs) as transducer elements and support materials, AFP as the template protein, N-isopropylacrylamide (NIPAM) and 4-vinylphenylbronic acid (VPBA) as the thermo-responsive and pH-responsive monomer, respectively, and ammonium peroxodisulphate (APS) and N,N'-methylene bisacrylamide (MBA) as the initiator and cross-linker, respectively. The newly synthesized nanosensor was characterized by FT-IR, TEM, XRD and elemental analysis, which unambiguously confirmed the successful formation of the nanosensor. The fluorescence quenching degree of CDs@MIPs exhibited a good linear response to AFP in a concentration range of 10 to 100 ng mL-1, the limit of detection (LOD) of 0.474 ng mL-1, and high recoveries at three spiking levels of AFP ranging from 97.05% to 102.00%, with relative standard deviations (RSDs) below 4.2% being obtained. Moreover, the proposed CDs@MIPs were successfully exploited to detect AFP in human serum samples. This study successfully established a novel method for rapid, convenient, and highly sensitive and selective detection of AFP, which provides new ideas for the detection of tumor markers.

A fluorescence turn-on biosensor based on gold nanoclusters and aptamer for alpha fetoprotein detection

Alpha-fetoprotein (AFP), an important tumor marker, is widely used for the diagnosis of patients with germ cell tumors and hepatocellular carcinoma. Herein, a highly sensitive aptasensor for AFP detection was constructed based on fluorescence resonance energy transfer (FRET) between 5-carboxyfluorescein (FAM) and gold nanoclusters (AuNCs). AuNCs can effectively quench the fluorescence of FAM-AFP aptamer via strong coordination interactions. When AFP was introduced into the FAM-AFP aptamer-AuNCs FRET system, the AFP aptamer preferentially combined with AFP accompanied by conformational change, which greatly weakened the coordination interaction between the AFP aptamer and AuNCs. Thus, fluorescence recovery of FAM was observed. In the range of 10.0 -100.0 ng/mL, a linear relationship between the fluorescence recovery rate and the concentration of AFP was obtained with the detection limit of 6.631ng/mL. The highly sensitive FRET aptasensor with simple configuration showed promising prospect in detecting a variety of biomarkes.

A simple immunosensor for alpha-fetoprotein determination based on gold nanoparticles-dextran-reduced graphene oxide

In this paper, a simple and sensitive immunosensor was fabricated for the detection of alpha-fetoprotein (AFP), which is based on a one-pot synthesized nanocomposite of gold nanoparticles-dextran-reduced graphene oxide (AuNPs-Dex-RGO). The AuNPs-Dex-RGO nanocomposite structure was confirmed by transmission electron microscope (TEM), Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR). With ferricyanide as the electrochemical probe, this method achieved ultrasensitive detection of AFP antigen. The specific immunoreaction between AFP and AFP antibody resulted in a linear relationship between the redox peak current intensity of [Fe(CN)6]4−/3- and AFP concentration. The detection range is 0.01–20ngmL−1, and the detection limit is 0.05pgmL−1. Moreover, the selectivity, reproducibility and stability of the proposed immunosensor were acceptable, which permitted the feasibility for the determination of AFP in human serum with satisfactory results, indicating the great potential for clinical application.

A novel ECL sensor based on a boronate affinity molecular imprinting technique and functionalized SiO2@CQDs/AuNPs/MPBA nanocomposites for sensitive determination of alpha-fetoprotein

In this work, a boronate-affinity sandwich electrochemiluminescence (ECL) sensor was constructed to detect alpha-fetoprotein (AFP) based on a multiple signal amplification strategy. Gold nanoparticles (AuNPs) were utilized and modified on the surface with chitosan in order to facilitate electron transfer. The composite of the molecularly imprinted polymer (MIP) enhanced the selectivity of alpha-fetoprotein detection. 4-mercaptophenylboronic acid (MPBA) was used as the tracing tag for capture of alpha-fetoprotein. SiO2 nanoparticles carried carbon quantum dots (CQDs) labeled with gold nanoparticles and produced an ECL signal. Under the optimum experimental conditions, the linear range for alpha-fetoprotein was between 0.001 and 1000 ng/mL with a correlation coefficient of 0.9952, and the detection limit was 0.0004 ng/mL (S/N = 3). This proposed ECL sensor displayed several advantages, including outstanding selectivity, fine reproducibility, high sensitivity, low detection limit and wide linear range. Furthermore, the newly constructed boronate-affinity sandwich ECL sensor was successfully applied to the determination of alpha-fetoprotein in serum samples, indicating great potential for application in clinical diagnostics.