Co-functionalization with phosphate and carboxylate on polydiacetylene for colorimetric detection of calcium ions in serum†
In this study, co-functionalization with phosphate and carboxylate on polydiacetylene (PDA) was proposed to detect calcium ions in serum, inspired by biologically abundant phosphate–calcium ion and carboxylate–calcium ion binding. The cooperative interaction of calcium ions with phosphate and carboxylate in PDA induced the change of electronic properties in the backbone without aggregation of liposomes, accompanied by blue-to-purple color transition. The cooperative effect through the introduction of mixed ligands facilitated the selective detection of calcium ions over magnesium ions, which was a source of major interference in 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.