Quenching mechanism of PEG emission by pyrimidines and their detections using PEG as fluorescent sensor

Abstract

Pyrimidines, in particular uracil (UL) and 5-fluorouracil (5FU), are well known anticancerogens and widely used against a variety of cancers. An important concerning issue has been their monitoring and detection in order to adequately control their doses and to minimize their health hazards. Among a variety of methods developed, fluorescence sensing is gaining more attention because of its accuracy, easy operation, and straight visuability. However, in most of the reported studies, the sensors are made from transition metals with sophisticated multi-processes; polymers, particularly biopolymers, are hardly available. We demonstrate herein that aqueous solution of poly(ethylene glycol) (PEG), a commonly known biopolymer, is highly emissive under excitation of 280 nm. While the solutions of selected pyrimidines, i.e. UL and 5FU, are non-emissive under the same excitation, their addition to PEG solution, however, brings about a distinct and concentration dependent quenching for PEG emission. PEG was then used as sensor with good stability for UL and 5FU detections in water. The tests were also done by spiking 5FU in tap water, milk and synthetic urine, confirming that 5FU was practically fully recovered in all the cases. The quenching was ascribed to the interaction between PEG clusters and the heteroatoms on pyrimidine molecules through hydrogen bonding, which is supported by multi-technical analyses, including NMR, FTIR and cluster size tests by DLS. This work provides therefore a full green, easy to operate, low-costing, novel and reliable protocol for pyrimidine monitoring and detection, with the quenching mechanism interpreted based on multi-technical characterizations.