A Biologically Compatible Colorimetric Sensor for the Selective Recognition of Cu²⁺ Ions in Biological Matrices

Heavy metal ions pollution is posing a major danger to human health across the planet. We present a phenylhydrazone-based colorimetric sensor for detecting Cu²⁺ ions in tap water and human blood plasma. The phenylhydrazone-based sensor (Sensor 1) is extremely selective for recognizing Cu²⁺ ions over other similar metal ions by producing a colorimetric response. Upon interaction with Cu^2+, the colorless sensor 1 changes to dark yellow within a minute producing a bathochromic shift in the absorption spectrum. The AFM, Zetasizer and FTIR spectroscopic techniques were used for Cu²⁺ detection and selectivity of sensor 1. The average size of sensor 1 is around 293.9 nm which changes to 2275 nm upon complexation with Cu²⁺. Sensor 1 was highly selective towards Cu²⁺ as no interference was recorded by various metals ions. The detection limit was found to be 0.1 μM with R² equal to 0.9821. Furthermore, cytotoxic experiments showed that sensor 1 is nontoxic to various cell lines, which revealed that it could detect Cu²⁺ ions in the biological system. Moreover, sensor 1 gives satisfactory results for detecting Cu²⁺ ions in human blood plasma and real water samples.