Interaction of methylparaben and propylparaben with P123/F127 mixed polymeric micelles

This paper reports the interaction between Pluronic F127, P123 and their mixed micelles with methylparaben and propylparaben. The UV studies revealed that, the spectral behavior of mixed micelle of F127 and P123 with parabens lay between their individual micellar behaviors. The cloud point studies have shown similar results. It was observed that the intensity of fluorescence spectra, compared with the single micelle-drug combinations was much higher with the mixed micelle-methylparaben combinations and lower with the mixed micelle-propylparaben combinations. The number of binding sites was calculated. Static nature of quenching was observed. The dissociation constant K_D for methylparaben - mixed pluronic and propylparaben - mixed pluronic combinations were 21.18 × 10^-3 L mol^-1 and 32.57 × 10^-3 L mol^-1 respectively. This suggests that there was stronger binding between methylparaben and mixed micelle compared to propylparaben and mixed micelle. Dynamic light scattering studies indicated that the addition of NaCl to the mixed micelle and parabens facilitated the micellar aggregation and better encapsulation efficiency for the drug. Scanning electron microscope images showed the incorporation of methylparaben and propylparaben molecules into the surface cavities of mixed micelle, pointing towards the change in morphology. This is probably the first report on interaction study of parabens with mixed micelles.