A Remarkable Superquenching and Superdequenching Sensor for the Selective and Noninvasive Detection of Inorganic Phosphates in Saliva

A neutral polyfluorene derivative, poly(9,9-bis(6′-benzimidazole)hexyl) fluorene- alt -1,4-phenylene (PBP), is synthesized and well characterized by 1 H NMR, 13 C NMR, and GPC. PBP exhibits exemplary activity as noninvasive fluorescence sensor and accomplishes in situ monitoring of important biological targets like Fe 3+ and inorganic phosphates in saliva. On binding Fe 3+, the fluorescence of PBP is quenched by 97% in label free conditions. The fluorescence of PBP is regained back on adding inorganic phosphate with a fluorescence enhancement of 106% due to the displacement of Fe 3+ from the PBP. This PBP assay is further used to detect and estimate inorganic phosphate in fresh saliva samples which is also able to enhance the fluorescence by >94%. This ability of PBP to accomplish in situ monitoring and estimation of indispensable biological targets like Fe 3+ and inorganic phosphates rapidly, at very low concentration with very high selectivity corroborates the extension of this assay system for safe clinical applications.