Differential Interaction of β-Cyclodextrin with Lipids of Varying Surface Charges: A Spectral Deciphering Using a Cationic Phenazinium Dye

Interaction of phenosafranin (PSF), a biologically potent cationic dye molecule, has been studied with zwitterionic and anionic lipid membranes of dimyristoyl-l-α-phosphatidylcholine (DMPC) and dimyristoyl-l-α-phosphatidylglycerol (DMPG), respectively. The effect of cyclic oligosaccharide, β-cyclodextrin (β-CD), on the stability of these probe-bound lipid bilayers has also been investigated exploiting steady state and time-resolved fluorescence, steady state fluorescence anisotropy, and dynamic light scattering techniques. An interpretation of membrane destabilization upon interaction of cyclodextrin with the lipids was drawn exploiting PSF as an extrinsic fluorescent probe. The fluorophore showed discernible interactions with DMPC and DMPG vesicles. Experimental results reveal that the extent of interaction of PSF with DMPG is greater compared to that with DMPC. Addition of β-CD into the PSF-bound lipids showed a differential effect for the two lipids of varying surface charge characteristics. In the case of DMPC, addition of β-CD resulted in a preferential interaction of the probe with CD. However, addition of β-CD to PSF-bound DMPG resulted in the selective interaction of DMPG with the added CD leading to the release of the probe into the bulk aqueous medium.