Jing Bao

Plant Esterase–Chitosan/Gold Nanoparticles–Graphene Nanosheet Composite-Based Biosensor for the Ultrasensitive Detection of Organophosphate Pesticides

As broad-spectrum pesticides, organophosphates (OPs) are widely used in agriculture all over the world. However, due to their neurotoxicity in humans and their increasing occurrence in the environment, there is growing interest in their sensitive and selective detection. This paper reports a new cost-effective plant esterase-chitosan/gold nanoparticles-graphene nanosheet (PLaE-CS/AuNPs-GNs) biosensor for the sensitive detection of methyl parathion and malathion. Highly pure plant esterase is produced from plants at low cost and shares the same inhibition mechanism with OPs as acetylcholinesterase, and then it was used to prepare PLaE-CS/AuNPs-GNs nanocomposites, which were systematically characterized using SEM, TEM, and UV-vis. The PLaE-CS/AuNPs-GNs composite-based biosensor measured as low as 50 ppt (0.19 nM) of methyl parathion and 0.5 ppb (1.51 nM) of malathion (S/N = 3) with a calibration curve up to 200 ppb (760 nM) and 500 ppb (1513.5 nM) for methyl parathion and malathion, respectively. There is also no interference observed from most of common species such as metal ions, inorganic ions, glucose, and citric acid. In addition, its applicability to OPs-contaminated real samples (carrot and apple) was also demonstrated with excellent response recovery. The developed simple, sensitive, and reliable PLaE-CS/AuNPs-GNs composite-based biosensor holds great potential in OPs detection for food and environmental safety.

A regenerative and selective electrochemical aptasensor based on copper oxide nanoflowers-single walled carbon nanotubes nanocomposite for chlorpyrifos detection

Chlorpyrifos is a commonly used organophosphorus pesticide in agriculture. However, its neurotoxicity poses a huge threat to human health. To detect trace amounts of chlorpyrifos, we herein developed a regenerative electrochemical aptasensor for the sensitive detection of chlorpyrifos. The nanocomposite consisting of copper oxide nanoflowers (CuO NFs) and carboxyl-functionalized single walled carbon nanotubes (c-SWCNTs) was prepared to improve the sensing performance for chlorpyrifos detection. Various characterization methods such as scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and cyclic voltammetry (CV) were used to demonstrate the successful fabrication of biosensor. Differential pulse voltammetry (DPV) was utilized to optimize test conditions and quantify chlorpyrifos. Under optimal conditions, the biosensor obtained a good linearity for chlorpyrifos ranging from 0.1 to 150ng/mL, with a lower detection limit of 70pg/mL. This aptasensor also exhibited high selectivity and outstanding repeatability, and was successfully applied to the determination of chlorpyrifos in spiked apple and celery cabbage with satisfactory recoveries. Furthermore, the sensor can be easily regenerated by urea for continuous application. With all the features, the proposed strategy provides an excellent platform for regenerative and selective detection of chlorpyrifos.

A sandwich-type electrochemical immunoassay for ultrasensitive detection of non-small cell lung cancer biomarker CYFRA21-1

Many studies confirm that the aberrant expression of Cytokeratin 19 fragment 21-1 (CYFRA21-1) is highly correlated with non-small cell lung cancer (NSCLC), especially for squamous cell carcinoma. Herein, we report a sandwich-type electrochemical immunosensor based on signal amplification strategy of multiple nanocomposites to test CYFRA21-1 selectively and sensitively. The proposed immunosensor fabricated by three-dimensional graphene (3D-G), chitosan (CS) and glutaraldehyde (GA) composite on the glass carbon electrode (GCE) with a large surface area is prepared to immobilize primary antibodies (Ab1) and provide excellent conductivity. To further amplify the electrochemical signal, the trace tag on the foundation of gold nanoparticles (AuNPs) is coated with amino-functionalized carbon nanotube (MWCNT-NH2) nanocomposite through thionine linking, which provides more amino groups to capture more horseradish peroxidase-labeled antibodies (HPR-Ab2) and enhances the conductivity. Under optimal conditions, the developed immunosensor exhibits excellent analytical performance for the determination of CYFRA21-1 with a wide linear range from 0.1 to 150ng·mL-1 and a low detection limit (LOD) of 43pg·mL-1. Furthermore, satisfactory results are obtained for the determination of CYFRA21-1 in real clinical serum samples, indicating the potential of the immunoassay to be applied in clinical analysis.

Fluorescent sensor for indirect measurement of methyl parathion based on alkaline-induced hydrolysis using N-doped carbon dots

High-performance measurement of methyl parathion (MP) is of great importance in both agricultural and environmental surveillance. Herein, we presented a facile fluorescent biosensor to indirectly measure MP using N-doped carbon dots (N-CDS) based on the inner filter effect (IFE). Methyl parathion was employed as the substrate of alkaline-catalytic hydrolysis, and p-nitrophenol (p-NP) was obtained by rapid the hydrolysis reaction under strong alkaline conditions without enzymes. Interestingly, the absorption band of p-NP appeared at 403 nm, which presented an overlapping spectrum with the excitation of N-CDs (410 nm). Due to its strong molar absorptivity, p-NP played the part of a powerful absorber in IFE to influence the excitation of fluorophore (N-CDs). Through the competitive absorption, the fluorescence intensity of N-CDs decreased extremely. With optimum conditions selected, the fluorescent sensor presented a concentration-dependent fluorescent response (ΔF) to MP ranging from 0.075 to 15 ppm (R2 =0.9956). The limit of detection was calculated to be 1.87 ppb (S/N = 3) with good selectivity. Successful measurement of MP in spiked river water and apple samples demonstrated that as-proposed optical sensor provided an alternative strategy for real applications in environmental and food safety control.

A sensitive label-free electrochemical immunosensor for detection of cytokeratin 19 fragment antigen 21-1 based on 3D graphene with gold nanopaticle modified electrode

Previous studies have confirmed that CYFRA 21-1 serves as a powerful biomarker in non-small cell lung cancer (NSCLC). Herein, we report for the first time a label-free electrochemical immunosensor for sensitive and selective detection of tumor marker cytokeratin 19 fragment antigen 21-1 (CYFRA21-1). In this work, three-dimensional graphene @ gold nanoparticles (3D-G@Au) nanocomposite was modified on the glassy carbon electrode (GCE) surface to enhance the conductivity of immunosensor. The anti-CYFRA21-1 captured and fixed on the modified GCE through the cross-linking of chitosan (CS), glutaraldehyde (GA) and anti-CYFRA21-1. The DPV peak current change due to the specific interaction between anti-CYFRA21-1 and CYFRA21-1 on the modified electrode surface was utilized to detect CYFRA21-1. Under optimized conditions, the proposed electrochemical immunosensor was employed to detect CYFRA21-1 and exhibited a wide linear range of 0.25~800 ng·mL −1 and low detection limit of 100 pg·mL −1 (S/N=3). Moreover, interference from bovine serum albumin (BSA), carcinoembryonic antigen (CEA), ascorbicacid (AA), dopamine (DA) and uricacid (UA) were nearly negligible. In addition, the recovery rates of serum samples were in the range from 95.2% to 108.7%. Therefore, it is expected that the proposed immunosensor based on a 3D-G@Au has great potential in clinical medical diagnosis of CYFRA21-1.Previous studies have confirmed that cytokeratin 19 fragment antigen 21-1 (CYFRA 21-1) serves as a powerful biomarker in non-small cell lung cancer (NSCLC). Herein, we report for the first time a label-free electrochemical immunosensor for sensitive and selective detection of tumor marker CYFRA21-1. In this work, three-dimensional graphene @ gold nanoparticles (3D-G@Au) nanocomposite was modified on the glassy carbon electrode (GCE) surface to enhance the conductivity of immunosensor. The anti-CYFRA21-1 captured and fixed on the modified GCE through the cross-linking of chitosan (CS), glutaraldehyde (GA) and anti-CYFRA21-1. The differential pulse voltammetry (DPV) peak current change due to the specific interaction between anti-CYFRA21-1 and CYFRA21-1 on the modified electrode surface was utilized to detect CYFRA21-1. Under optimized conditions, the proposed electrochemical immunosensor was employed to detect CYFRA21-1 and exhibited a wide linear range of 0.25-800ngmL-1 and low detection limit of 100pgmL-1 (S/N = 3). Moreover, the recovery rates of serum samples were in the range from 95.2% to 108.7% and the developed immunosensor also shows a good correlation (less than 6.6%) with enzyme-linked immunosorbent assay (ELISA) in the detection of clinical serum samples. Therefore, it is expected that the proposed immunosensor based on a 3D-G@Au has great potential in clinical medical diagnosis of CYFRA21-1.