Photophysical Properties of Coumarin 343 and Structural Changes in Reline–Pluronic Systems With Varying Block Composition

ABSTRACT

Experimental and simulation studies reported in the literature largely addressed the role of water as a secondary hydrogen‐bond donor (HBD) or acceptor (HBA) in reline (a Type III deep eutectic solvent). In this work, the effect of reline acting as a ternary component on Pluronic assemblies with varying hydrophilic–lipophilic balances (P123 and F108) was investigated using coumarin 343 as a fluorescent probe through spectroscopic techniques. Through differential scanning calorimetry studies, a decrease in the critical micelle temperature values of Pluronics upon reline loading was observed. A red shift accompanied by a decrease in fluorescence intensity of negatively charged coumarin 343 (C343 ⁻ ) was observed upon reline loading in Pluronic systems, via UV–visible absorption and steady‐state fluorescence studies. Differences in time‐resolved fluorescence emission decay profiles between water‐reline and Pluronic‐reline mixtures confirmed the localization of C343 ⁻ within the micellar systems. A decrease in the fluorescence anisotropy decay times for P123 and an increase for F108 were observed upon reline loading. Fourier transform infrared spectroscopy, dynamic light scattering, and small‐angle neutron scattering measurements were also carried out to characterize the micellar systems. Ultimately, this work facilitates the rational design of hybrid nanocarriers for advanced biomedical applications.