A novel sandwich impedimetric immunosensor for detection of apolipoprotein-A1 based on the gold nanoparticle-hybridized mercapto-β-cyclodextrin-Pb(II) metal-organic framework

A novel sandwich electrochemical impedimetric immunosensor was proposed to detect apolipoprotein-A1 (Apo-A1), a common biomarker for bladder cancer. The molybdenum disulfide/graphene quantum dot (MoS2/GQD) nanocomposites were modified on the surface of a glassy carbon electrode (GCE) and used to immobilize the biotinylated antibody (Ab(1)) with the help of chitosan and glutaraldehyde (denoted as BSA/Ab(1)/CHIT/MoS2/GQD/GCE). Pb(II)-thiol-beta-cyclodextrin metal-organic framework (denoted as Pb-MOF) was synthesized with lead metal ions and thiol-beta-cyclodextrin ligands by a one-pot solvothermal method, and then, gold nanoparticles were modified on the surface of Pb-MOF (Pb-MOF-AuNPs) by Au-S bond, which was used as signal label for the recombinant antibody (Ab(2)). When the immunosensor of BSA/Ab(1)/CHIT/MoS2/GQD/GCE reacted with Apo-A1, Pb-MOF-AuNPs-Ab(2)/BSA was connected to the electrode when immunoreaction occurred, and an immune sandwich structure was formed, which led to significantly increased charge transfer resistance of electrochemical probe for ferrocyanide (II)/(III) within the frequency range 10(-1) similar to 10(5) Hz at 5 mV amplitude and the potential of 0.180 V (vs. SCE). Based on this principle, the quantitative detection of Apo-A1 was established. The relative change of electrochemical resistance and the logarithmic value of Apo-A1 concentration showed a linear relationship with a linear coefficient of 0.9989 in the range 1.00 pg mL(-1) and 1.00 mu g mL(-1) with the limit of detection of 0.30 pg mL(-1). The selectivity, repeatability, and other performance of the proposed immunosensor were also investigated. The immunosensor was successfully applied to the detection of real serum and urine samples with recovery in the range 96.4 similar to 109.1% (RSD < 3.8%), indicating that it could be helpful for the clinical diagnosis of bladder cancer.

Automated summary

A sandwich electrochemical impedimetric immunosensor was developed for detecting Apolipoprotein-A1 (Apo-A1), a common biomarker for bladder cancer. The immunosensor utilized molybdenum disulfide/graphene quantum dot (MoS2/GQD) nanocomposites to immobilize the biotinylated antibody (Ab(1)). Lead-thiol-beta-cyclodextrin metal-organic framework (Pb-MOF) and gold nanoparticles were employed as signal labels. The immunosensor showed a linear relationship between the relative change of electrochemical resistance and the logarithmic value of Apo-A1 concentration, with a high linear coefficient and a low limit of detection.