Robust Tag-Free Aptasensor for the Visual Determination of Lead Ion Based upon the Peroxidase-Catalytic Activity of Gold Nanoparticles

Abstract

Here, a simple colorimetric strategy was developed to monitor lead ion (Pb²⁺) based upon the catalytic function of gold nanoparticles (AuNPs) regulated by the aptamer strands. The peroxidase-like activity of AuNPs was prevented by the aptamers through masking their surface. Thus, the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) did not proceed. By adding Pb²⁺, the aptamer-Pb²⁺ complex was formed that released the aptamer from the surface of AuNPs. Hence, free AuNPs initiated the oxidation of TMB that changed the solution color from colorless to blue. A linear concentration range was achieved from 0.2 to 200 nM with a detection limit (LOD) of 0.056 nM for Pb²⁺ detection. The aptasensor successfully monitored Pb²⁺ in drinking water, milk, and human serum. With the properties of sensitivity, simplicity, and naked-eye target monitoring, the developed aptamer-included biosensor (aptasensor) is suitable for food safety, health care application, and environmental monitoring.

Keywords:

• Aptamer
• biosensor
• colorimetry
• gold nanoparticles (AuNPs)
• lead ion
• peroxidase-activity
• spectrophotometry

Disclosure statement

The authors declare that they have no competing interests.

Additional information

Funding

This study was financed by Iran National Science Foundation (INSF) as a research project (Project 99012771).