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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]

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]