The fluorescence study of the quenching of nanoemulsion by protoporphyrin IX (PPIX)

Nanoemulsion is a unique and versatile fluid that solubilizes both ionic and non-ionic molecules. It has been used extensively for drug delivery. Nanoemulsion, prepared with water-oil-surfactant and co-surfactant, is fluorescent at or the near IR region of electromagnetic spectrum. However, when protoporphyrin (PPIX), a useful photosensitizer in PDT modality, and a poorly water-soluble compound, is introduced into the nanoemulsion medium, the observed fluorescence of the nanoemulsion is quenched. We have used the steady-state fluorescence technique to study the mechanism of this quenching. It is observed that the interaction between nanoemulsion and PPIX is 1:1 and the interaction constant, Ka, is about 2.37 x 105/mol and the Free energy of interactions, Ga, is -30.66 kJ/mol.