Co-functionalization with phosphate and carboxylic acid on polydiacetylene for colorimetric detection of calcium ion in serum
In this study, co-functionalization with phosphate and carboxylic acid on polydiacetylene (PDA) was proposed to detect calcium ion in serum, inspired by biologically abundant phosphate-calcium ion and carboxylic acid-calcium ion binding. The cooperative interaction of calcium ion with phosphate and carboxylic acid in PDA induced the change of electronic property in backbone without aggregation of liposomes, accompanying with blue-to-purple color transition. The cooperative effect through the introuction of mixed ligands facilitated the selective detection of calcium ions over magnesium ions, which was a source of major interference on many calcium ion probes, and in the presence of major serum metal ions. The sensor system exhibited highly sensitive detection of calcium ions with an estimated limit of detection of 0.97 µM. In addition, the detection method was employed to determine the concentration of calcium ions in various serums.