Facile detection of Pb²⁺ based on gold nanoparticles functionalized by specific receptor proteins

A facile colorimetric Pb²⁺ assay system has been developed based on the visible color change of gold nanoparticles (GNPs) modified with α2-microglobulin (α2M) protein. The α2M protein is a soluble and high-affinity receptor for Pb²⁺, which is well studied and regarded as the comparable positive control in Pb-binding protein researches. It was obtained through purifying recombinant protein from the expression of recombinant plasmids in Escherichia coli and was attached on GNPs to form GNPs-α2M sensor nanoparticles for detecting Pb²⁺, which has never been used for sensing Pb²⁺ in previous studies. When Pb²⁺ was introduced into the assay system, GNPs-α2M sensor nanoparticles can be triggered aggregation with the color change from pink to blue. The detection system exhibited good selectivity and sensitivity, which was attributed to the receptor specificity of α2M protein. Using this assay system, it can be distinguished 1.00 μM concentration of Pb²⁺ or more by naked eyes clearly. Furthermore, the UV-Vis absorbance ratio between 620 and 523 nm exhibited linearity relationship with the concentration of Pb²⁺ from 0.05 to 3 μM in assay system. In this research, GNPs-α2M sensor nanoparticles have highly specific capability to recognize Pb²⁺. The assay system constituted by GNPs-α2M sensor nanoparticles displays excellent convenience, selectivity, and sensitivity that provide promising potentials for on-site rapid test of Pb²⁺.