Photophysical Properties of Coumarin 343 and Structural Changes in Reline-Pluronic Systems With Varying Block...

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.