Molecular Level Understanding of Sodium Dodecyl Sulfate (SDS) Induced Sol–Gel Transition of Pluronic F127 Using Fisetin as a Fluorescent Molecular Probe

Abstract

The thermoreversible sol-gel transition of pluronic F127 is markedly altered even with addition of submicellar concentration of sodium dodecyl sulfate (SDS) surfactant. Multiple fluorescence parameters like fluorescence intensity, fluorescence anisotropy and fluorescence lifetime of both the prototropic forms (anion (A*) and phototautomer FT*) of the photoprototropic fluorescent probe fisetin has been efficiently used to understand the molecular level properties like polarity and microviscosity of the PF127-SDS system as a function of temperature. The SDS-induced increase in the interfacial hydrophobicity level is seen to affect the sol-gel phase transition of PF127 (21-18 °C). The E(30) polarity parameter value of anionic emission of fisetin suggests that there is a considerable decrease in the polarity of the PF127 medium with increase in temperature and with the addition of SDS. The microviscosity progressively increases from ∼5 mPa s (sol state, 10 °C) to ∼22.01 mPa s (gel state 35 °C) in aqueous solution of PF127. The variation in microviscosity with addition of SDS in PF127-SDS mixed system is significant in sol phase whereas in gel phase this variation is significantly less. Temperature dependent fluorescence lifetime of FT* indicates that there is heterogeneity in distribution of fisetin molecules at different domains of PF127. This work also show-cases the sensitivity of fisetin toward change in polarity and change in sol-gel transition temperature of copolymer PF127 with variation in temperature (both forward and reverse directions) and SDS.

Probing the Local Polarity in Biocompatible Nanocarriers with Solvatofluorochromism of a 4-Carbazole-1,8-naphthalimide Dye

“…It is demonstrated that the calculated dielectric constants for polymeric nanocarriers are very close to literature values for these polymers, which validates NI 3 as an adequate fluorescent dye to probe local polarity in polymeric nanoparticles. However, the calculated apparent polarity for surfactant micelles is lower than those determined in other works using solvatochromic dyes [34,35]. These differences may be attributed to conformational effects due to the smaller size of micelles compared to polymeric NPs, or to a localization of 3 within the micelle hydrophobic center.…”

Estimation of Micropolarity and Microviscosity of Pluronic F127–Surfactant Mixed Systems Using Fisetin as a Fluorescent Molecular Probe

“…In our previous study we have observed that, with increase in SDS concentration, hydrophobicity of the PF127 medium increases. This decrease in medium hydrophobicity leads to decrease the transition temperature . A molecular level understanding on the interaction of higher concentration of surfactants on the transition temperature of PF127 copolymer requires a detailed analysis of the fluorescence intensity and lifetime data of both the prototropic forms of fisetin which will be discussed further.…”

“…The longer lifetime value decreases with increase in temperature from sol‐gel phase of PF127, PF127+TW20 and PF127+CTAB whereas it almost remains constant for PF127+SDS. In our previous study, we have reported that the shorter lifetime value originates from core‐corona domain whereas the longer lifetime value originates from aqueous‐corona domain, so the increase in lifetime value of shorter component from nonionic to ionic surfactant indicates the increase in microviscosity at the core‐corona domain of PF127 in presence of surfactants. The variation in the corresponding relative amplitudes of both the components is represented in Figure S5.…”

“…It is observed that the full width half maximum (FWHM) value of shorter component increases along with a decrease in FWHM value of longer component from PF127‐ PF127+TW20 ‐ PF127+CTAB ‐ PF127+SDS. As discussed in the fluorescence lifetime study, the shorter component of FT* emission originates from core‐corona domain whereas the longer component originates from aqueous‐corona domain, so in presence of additives like TW20, CTAB and SDS the local environmental heterogeneity sense by fisetin FT* species increases in the core‐corona domain whereas it significantly decreases in the aqueous‐corona domain . Like sol phase, the distribution plot and corresponding distribution data of fisetin FT* emissions in the gel phase are given in Figure B and Table S6.…”

Nature of Saccharide-Induced F127 Micellar Dehydration: An Insight with FDAPT (2-Formyl-5-(4′-N,N-dimethylaminophenyl)thiophene), a Multiparametric Fluorescent Probe

“…Various additives like salts, − ionic liquids, − nonelectrolytes, − nanoparticles, surfactants, alcohols, − carbohydrates, , and polymers , were reported to change the CMT of different Pluronic systems. ,,, Among these materials, saccharide molecules, which play several important roles in various biological processes, − exhibit a significant effect on the aggregation behavior of Pluronics. Kim et al reported lowering of the lower critical solution temperature (LCST) of thermoresponsive polymers in the presence of different saccharides based on the cloud point measurements .…”