Search

Abstract: For the specificity of prostate cancer markers, protsate specific antigen (PSA) has been widely used in prostate cancer screening, diagnosis, and treatment after monitoring. In normal male serum, PSA can only be detected in traces of 0–4ngmL−1. In this paper, we constructed an electrochemical immunosensor for PSA detection using a nanocomposite film of graphene sheets–methylene blue–chitosan (GS-MB-CS) as electrode material. The nanocomposite film showed high binding affinity to the electrode and was used to immobilize the antibody of PSA. The modification procedure was monitored by cyclic voltammetry (CV). An amperometric biosensor was easily developed based on the response of peak current to the capture of PSA induced by specific antigen–antibody reactions. Under optimum conditions, the amperometric signal decreased linearly with PSA concentration (0.05–5.00ngmL−1). A low limit of detection (13pgmL−1) and a high selectivity are obtained. Moreover, the prepared immunosensor was applied for the analysis of PSA in serum samples with satisfactory results. The proposed method may have a promising future in biochemical assays for high selectivity, good reproducibility, and stability. [Copyright &y& Elsevier]

Abstract: A novel label-free electrochemical immunosensor for the detection of alpha fetoprotein (AFP) has been developed by immobilizing anti-AFP on graphene sheet (GS) and thionine (TH) modified glassy carbon electrode. The modification procedure was characterized by cyclic voltammetry (CV). The detection is based on the peak current change of the modified electrode before and after the antigen–antibody reaction. Tests relating to the detection of AFP demonstrated that the immunosensor exhibited high sensitivity, wide linear range (0.05–2.00ngmL−1), low detection limit (5.77pgmL−1 based S/N =3) and good long-term stability. The reliability of the developed immunosensor has been proved by the detection of AFP in serum samples with satisfactory results. [ABSTRACT FROM AUTHOR]

An electrochemical immunosensor for quantitative detection of α-fetoprotein (AFP) in human serum was developed using graphene sheets (GS) and thionine (TH) as electrode materials and mesoporous silica nanoparticles (MSNs) loaded with ferroferric oxide (Fe 3 O 4 ) nanoparticles and horseradish peroxidase (HRP) as labels for signal amplification. In this study, the compound of GS and TH (GS–TH) was used as a substrate for promoting electron transfer and immobilization of primary antibody of AFP (Ab 1 ). MSNs were used as a carrier for immobilization of secondary antibody of AFP (Ab 2 ), Fe 3 O 4 , and HRP. The synergistic effect occurred between Fe 3 O 4 and HRP and greatly improved the sensitivity of the immunosensor. This method could detect AFP over a wide concentration range from 0.01 to 25 ng ml −1 with a detection limit of 4 pg ml −1 . This strategy may find wide potential application in clinical analysis or detection of other tumor markers. [ABSTRACT FROM AUTHOR]

Abstract: A sandwich-type electrochemical immunosensor for the ultrasensitive detection of the salbutamol (SAL) antigen based on sodium dodecylbenzene sulfonate-functionalized graphene sheets (SDBS-GS), Pd nanoparticles in functionalized SBA-15 (Pd@SBA-15) and ionic liquid (IL) is described. The primary SAL antibody (Ab1) can be covalently attached to the sulfonic groups of SDBS-GS through the amines of Ab1 with an acyl chloride cross-linking reaction. Pd@SBA-15 was prepared by adsorption of H2PdCl4 onto the SBA-15 surface; the adsorbed H2PdCl4 was then reduced to Pd nanoparticles with sodium borohydride. Pd@SBA-15 was conjugated to the secondary SAL antibody (Ab2) through glutaraldehyde. IL was added to the mixture of Pd@SBA-15 and Ab2 to promote electron transport. The synergistic effect between IL and Pd@SBA-15 retained the bioactivity of Ab2. The sensitivity of the sandwich-type immunosensor using Pd@SBA-15/Ab2/IL for the detection of SAL was much higher than those that used either SBA-15/Ab2 or Pd@SBA-15/Ab2. Under optimal conditions, the electrochemical immunosensor exhibited a wide working range from 0.02 to 15.0ng/mL with a detection limit of 7pg/mL. The precision, reproducibility and stability of the immunosensor were acceptable. The proposed strategy could be easily extended to fabricate immunosensors for other tumor markers. [Copyright &y& Elsevier]

Abstract: Bisphenol A (BPA), which could disrupt endocrine system and cause cancer, has been considered as an endocrine disruptor. Therefore, it is very important and necessary to develop a sensitive and selective method for detection of BPA. Herein, nitrogen-doped graphene sheets (N-GS) and chitosan (CS) were used to prepare electrochemical BPA sensor. Compared with graphene, N-GS has favorable electron transfer ability and electrocatalytic property, which could enhance the response signal towards BPA. CS also exhibits excellent film forming ability and improves the electrochemical behavior of N-GS modified electrode. The sensor exhibits a sensitive response to BPA in the range of 1.0×10−8–1.3×10−6 molL−1 with a low detection limit of 5.0×10−9 molL−1 under the optimal conditions. Finally, this proposed sensor was successfully employed to determine BPA in water samples with satisfactory results. [Copyright &y& Elsevier]

Abstract: A novel label-free electrochemical immunosensor for sensitive detection of kanamycin based on water-soluble graphene sheet (WGS)/prussian blue-chitosan (PB-CTS)/nanoporous gold (NPG) composited film has been reported. PB was selected as an electron transfer mediator, and was modified onto the electrode together with WGS through electrostatic adsorption. Then NPG was immobilized onto the as-prepared film for biomolecules anchoring. The electroactivity of PB was greatly enhanced in the presence of WGS and NPG. It could mainly be ascribed to the fact that the good conductivity of WGS and NPG promoted electron transfer and enhanced the sensitivity. kanamycin antibody, as a model, was immobilized onto the composite film for the detection of kanamycin. Under optimum conditions, the amperometric signal of PB decreased linearly with kanamycin concentration (0.02–14ngmL−1), a linear calibration plot (y =1.3817+4.7544x, r =0.9993), resulting in a low limit of detection (6.31pgmL−1). The novel immunosensor for the detection of kanamycin in real sample with satisfactory results has been proved. In addition, this method would be easily adapted for the detection of other residual antibiotics in animal derived foods. [Copyright &y& Elsevier]