An ultrasensitive electrochemical immunosensor for the detection of salbutamol based on Pd@SBA-15 and ionic liquid

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 15.0 ng/mL with a detection limit of 7 pg/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.