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Aflatoxin B1 (AFB1) is one of the most contaminated fungal toxins worldwide and is prone to cause serious economic losses, food insecurity, and health hazards to humans. The rapid, on-site, and economical method for AFB1 detection is need of the day. In this study, an AFB1 aptamer (AFB1-Apt) sensing platform was established for the detection of AFB1. Fluorescent moiety (FAM)-modified aptamers were used for fluorescence response and quenching, based on the adsorption quenching function of single-walled carbon nanohorns (SWCNHs). Basically, in our constructed sensing platform, the AFB1 specifically binds to AFB1-Apt, making a stable complex. This complex with fluorophore resists to be adsorbed by SWCNHs, thus prevent SWCNHs from quenching of fluorscence, resulting in a fluorescence response. This designed sensing strategy was highly selective with a good linear response in the range of 10-100 ng/mL and a low detection limit of 4.1 ng/mL. The practicality of this sensing strategy was verified by using successful spiking experiments on real samples of soybean oil and comparison with the enzyme-linked immunosorbent assay (ELISA) method.

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This paper presents a new fluorescent approach for the detection of protein tyrosine phosphatase 1B (PTP1B) based on titanium dioxide-decorated single-wall carbon nanohorns (TiO2-SWCNHs). The novel TiO2-SWCNHs nanocomposite was synthesized and characterized for the first time and the phosphorylated peptide as the substrate of PTP1B was designed. Properties of SWCNHs and TiO2 were combined by growing nano-sized TiO2 particles on SWCNHs, resulting in TiO2-SWCNHs. TiO2 provides SWCNHs a large adsorption surface area and can specifically bind to phosphopeptide substrate. TiO2-SWCNHs effectively quenched the fluorescence of the phosphorylated peptide substrate labeled by the fluorophore, and the system had a low fluorescence background. In the presence of PTP1B, dephosphorylation of the peptide occurred owing to the reaction between PTP1B and the peptide, causing the separation of the dye-labeled peptide from TiO2-SWCNHs, which resulted in fluorescence enhancement of the reaction system. Thus, a simple and rapid strategy for the detection of PTP1B activity was developed, with a detection limit of 0.01 ng/mL and linear range of 0-10 ng/mL. The system can be used to detect PTP1B in serum using the standard addition method. This system provides a new approach for screening PTP1B inhibitors.

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Dopamine (DBA) as an important biomarker, plays a crucial role in disease diagnosis. In this study, we have developed a fast and simple aptamer-based fluorescence strategy which used single-wall carbon nanohorns (SWCNHs) as a quencher for dopamine detection. SWCNHs were negatively charged after pretreated, which improved its dispersion in solution. 5-carboxy-fluorescein (FAM) was used to label dopamine aptamer. In the absence of dopamine, FAM-modified aptamer could be absorbed onto the SWCNHs surface due to π-π interaction, resulting in the fluorescence intensity decreased. Dopamine could specifically bind with FAM-DNA to form G-quadruplex, which could not be absorbed onto the surface of SWCNHs. Hence, the fluorescence of FAM-DNA recovered, and the fluorescent intensity as a function of different concentrations of dopamine was measured. We obtained a detection limit of 5 µM for this detection system with a linear detection range of 0.02-2.20 mM. Furthermore, the feasibility of the innovative detection system has been verified by detecting dopamine in spiked serum samples.

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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.

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Septicemia is a serious disease that requires early diagnosis, and procalcitonin (PCT) serves as a diagnostic biomarker for this disease. Traditional clinical detection (via immune-gold chips) remains difficult and expensive. An electrochemical immunosensor based on new nanomaterials may provide a solving approach. Herein, an ultrasensitive sandwich electrochemical strategy for PCT detection was developed. Firstly, reduced graphene oxide (rGO)-gold (Au) nano-composite film was used as the immunosensor platform to increase the amount of PCT antibody 1(Ab1) immobilized. Next, single-walled carbon nanohorns (SWCNHs)/hollow Pt chains (HPtCs) complex was firstly utilized to label PCT Ab2 as signal tags. For SWCNHs with few side effects, high surface area and HPtCs with higher specific surface, better catalytic activity, complex synthesized from both may provide more advantages. Moreover, to amplify signal, HPtC catalytic activity with H2O2 was enhanced by horseradish peroxidase (HRP) for dual synergy amplification. The whole results demonstrated that the proposed immunosensor exhibited fast operation, high sensitivity, good reproducibility, acceptable stability and ideal selectivity compared with traditional method. The linear calibration of the immunosensor ranged from 1.00 pg/mL to 2.00 × 10(1)ng/mL with a detection limit of 0.43 pg/mL. Analytical application results revealed that the immunosensor matched with the real concentrations of serum samples. Overall this immunosensor may provide a new alternative strategy for PCT detection.

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Oxidized Single-Wall Carbon Nanohorns (o-SWCNHs) were used, for the first time, to assemble chemically modified Screen Printed Electrodes (SPEs) selective towards the electrochemical detection of Epinephrine (Ep), in the presence of Serotonine-5-HT (S-5HT), Dopamine (DA), Nor-Epineprhine (Nor-Ep), Ascorbic Acid (AA), Acetaminophen (Ac) and Uric Acid (UA). The Ep neurotransmitter was detected by using Differential Pulse Voltammetry (DPV), in a wide linear range of concentration (2-2500 µM) with high sensitivity (55.77 A M(-1) cm(-2)), very good reproducibility (RSD% ranging from 2 to 10 for different SPEs), short response time for each measurement (only 2s) and low detection of limit (LOD=0.1 µM). o-SWCNHs resulted in higher analytical performances when compared with other nanomaterials used in literature for electrochemical sensors assembly.

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