Photoelectrochemical sensitive detection of insulin based on CdS/polydopamine co-sensitized WO3 nanorod and signal amplification of carbon nanotubes@polydopamine

- The polydopamine could covalent coupled with antibody and reduce the toxicity of CdS.
- The carbon nanotubes@polydopamine was used for signal amplification.
- The sensor had a wide detecting range and sensitive result.

An ultrasensitive photoelectrochemical sandwich immunosensor was designed for detection of insulin based on WO3/CdS/polydopamine (WO3/CdS/PDA) co-sensitized and PDA@carbon nanotubes (PDA@CNT) conjugates for signal amplification. The CdS nanoparticles were first deposited on the WO3 nanorods via sequential chemical bath deposition to form the WO3/CdS structure to enhance photocurrent. Then equipped with PDA to form the WO3/CdS/PDA photosensitive structure. The PDA was used not only to reduce the toxicity of CdS but also adsorb insulin primary antibodies (Ab1). Meanwhile, insulin secondary antibodies (Ab2) were decorated by PDA@CNT conjugates for signal amplification and further enhance photocurrent. Different photocurrent intensities were obtained by the photoelectrochemical workstation at applied bias of 0 V due to the different amount of the PDA@CNT conjugates introduced by the different concentrations of insulin. A good linear relationship was obtained between the increased photocurrent and insulin concentrations range from 0.01 ng mL−1 to 50 ng mL−1. And a detection limit of 2.8 pg mL−1 was obtained. The proposed sensor was applied to the determination of the insulin in human serum sample, and satisfactory results were obtained. The sensor presented good specificity, reproducibility and stability, thus it might find application in the clinical diagnosis of insulin or other biomarkers in the near future.