A Comparison of the Behavior of Monomolecular and Dual Molecular Probes in F127/Cyclodextrin Systems

Abstract

Molecular probes are often used to describe local interactions and to characterize inhomogeneities in complex systems. In this study, two series of monomolecular probes (paramagnetic or fluorescent) and a series of dual molecular probes are used to evaluate local changes and the regions targeted by these probes in three pluronic F127 systems, in the absence and in the presence of 2‐hydroxypropyl‐β‐cyclodextrin, which have been previously characterized. All molecular probes used in this study have as a common structural unit the short oligoethylene chains that link (2,2,6,6‐Tetramethylpiperidin‐1‐yl)oxyl (TEMPO) and/or pyrene moieties. Using these probes, changes in hydrophobicity inside the pluronic micelles are evidenced and the micelle‐to‐gel phase transition is characterized.

Cyclodextrins as Bricks for Tuning Polymer Properties

“…Being water soluble, CDs will be more probable to target the region of the micelles placed at the water interface. Two studies involving EPR and fluorescence spectroscopies along with rheological and tube inversion methods explore the effect of 2-hydroxypropyl-β-CD on the micelle-to-gel phase transition of pluronic F127 [34,35]. It was revealed that the spectral parameters of molecular probes (commercially available spin probes, spin-labeled CDs, CDs labeled with fluorophores, or dual molecular probes) deviate from the linear dependence with temperature (Figure 2), thus indicating that the macroscopically observed phase transformation is related to changes at the nanoscale level.…”

Non-covalent interactions evidenced by EPR spectroscopy in cyclodextrin complexes

“…This non-linear behaviour of EPR and fluorescence parameters can provide distinct information in complex systems in which hostguest interactions occur, 42 and in block copolymer micelles where the hydrophilic/hydrophobic properties are non-uniform. 47 The interaction between Py(EG) n T dual probes and β-CD was elucidated by following the changes in the EPR and fluorescence spectral features and parameters. At high β-CD concentration, the appearance of the vibrational fine structure of pyrene emission was observed.…”

“…The Py(EG) n T dual probes were also used to investigate the micelle-to-gel phase transition occurring in systems containing pluronic F127, in the absence and in the presence of HPB. 47 It was shown that the structural particularities of the probes markedly influenced the probe response. The analysis of the fluorescence and EPR spectra recorded in a temperature range around the micelle-to-gel transition temperature revealed the fact that only the EPR parameter a N was sensitive to the polarity changes accompanying the phase transition.…”

“…17 In our group, we studied the influence of cyclodextrin on the phase transition occurring in pluronic F127 systems. 47,66 For this purpose, we combined methods that offer global and local information on the systems. We used spin probes that have similar structure with F127 (spin-labelled pluronics), 66 as well as dual molecular probes that allowed us to evidence which spectral method is more sensitive for studying such systems.…”

“…We used spin probes that have similar structure with F127 (spin-labelled pluronics), 66 as well as dual molecular probes that allowed us to evidence which spectral method is more sensitive for studying such systems. 47 Spin-labelled cyclodextrins have been used to monitor the formation of covalent gel networks resulted by crosslinking the cyclodextrin with isocyanate end-capped polyethylene oxides (Fig. 19).…”