Understanding self-assembly behavior and nanocapsule formation of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) : application as vehicle for curcumin delivery and fluorescence sensing.

Abstract

F108 is a water-soluble non-ionic triblock copolymer. It belongs to the class of block copolymers, so called pluronics or poloxamers. These copolymers have dual character: hydrophilic and hydrophobic which establishes these molecules as amphiphilic species that can self-assemble in aqueous media into micelles having a hydrophobic core and a hydrophilic surface. Micellization occurs above a certain concentration, known as critical micelle concentration (CMC)and-or above a certain temperature, called critical micelle temperature (CMT). There has been extensive research on the utility of these micellar structures in different fields. On the other hand, extensive research is being held on curcumin, known for its therapeutic effects. However, this efficiency is still limited due to its low water-solubility and oral bioavailability. Therefore, various methods were developed to enhance solubility of curcumin. Moreover, due to its responsive fluorescence properties, curcumin is being extensively used as a probe to target specific systems. In this work, properties of F108 are studied in solution using fluorescence technique and curcumin as the molecular probe. Fluorescence of curcumin has been tracked in solutions of different concentrations of F108. The CMC and CMT have been found to be 23.2 µM and 35 °C respectively. Furthermore, fluorescence quenching technique, using Cetylpyridinium Bromide (CPB), has established the position of curcumin. Effect of ionic strength and bile salt on the CMC and CMT values of F108 is evaluated through curcumin probing.CMC has decreased with the increase in the concentration of the three salts except for NaC. The effect has been arranged in decreasing order as follows: NaDC NaClNaC. On the other hand, the effect of the three salts on the CMT of F108 has been found to be less remarkable, with a 1-fold decrease for NaCl and NaDC and almost no change for NaC. Lastly, quenching results, using CPB which has proved to be a better quencher, have established that curcumin is locate