BSA templated cerium/gold nanoclusters as pH and ROS dual sensors

Abstract

Bovine serum albumin (BSA) templated gold NCs (BSA–Au NCs) are interesting sensing materials. Unlike BSA–Au NCs, BSA templated cerium/gold nanoclusters (BSA–Ce/Au NCs) have two emission bands centered at 410 and 680 nm. The optical properties of BSA–Ce/Au NCs can be easily tuned by controlling the molar ratio of Ce(IV)/Au(III) and BSA concentration. Because the two bands are independently sensitive to changes in the pH value and reactive oxygen species (ROS) level, BSA–Ce/Au NCs have been used as a probe for determining pH values and quantitation of ROS. With respect to sensitivity and stability, BSA–Ce/Au NCs prepared from 1 mM Ce(IV), 5 mM Au(III), and 35 mg mL⁻¹ BSA are optimal. At pH 7.0, the BSA–Ce/Au NCs provide limits of detection of 0.8 and 3.2 μM for hydrogen peroxide and sodium hypochlorite, respectively. Based on the interesting pH and ROS concentration dependence of the optical properties of BSA–Ce/Au NCs, IMPLICATION (IMP) and NOT logic gates have been constructed. The biocompatible BSA–Ce/Au NCs allow recording HepG2 cell images that show H₂O₂ induced changes in the ROS level, but an insignificant change in the intracellular pH value.