Chitosan-cucurbit[5]uril supramolecular gel-induced room-temperature phosphorescence: A doxorubicin-responsive RTP probe based on PRET mechanism.

A supramolecular gel was constructed based on chitosan (CS) and cucurbit[5]uril (Q[5]) through self-assembly via hydrogen bonds and ion-dipole interactions. This gel possesses a dense three-dimensional network structure that provides a rigid microenvironment for encapsulating 6-bromo-2-methylquinoline (6-Br-2-MQ), successfully inducing room-temperature phosphorescence (RTP) emission at 511 nm with a phosphorescence lifetime of 1.537 ms and a quantum yield of 6.72%. Mechanistic studies indicate that the RTP emission originates from the synergistic effects of the rigid gel matrix, host-guest interactions at the Q[5], and the bromine-induced heavy-atom effect. The RTP system exhibits reversible temperature-responsive "on-off" behavior. Furthermore, based on a resonance energy transfer mechanism, the system serves as a phosphorescence probe for the detection of doxorubicin (DOX) in complex biological matrices with a detection limit of 0.65 μM, utilizing a PRET-based dynamic quenching mechanism. The probe shows good recovery (96.08-100.75%) and high anti-interference capability in artificial urine samples. This study provides a new strategy for developing RTP materials using naturally derived and biocompatible components, and demonstrates their potential as a simple, cost-effective platform for point-of-care biosensing applications in complex biological fluids.