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

Abstract

Interaction of phenosafranin (PSF), a biologically potent cationic dye molecule, has been studied with zwitterionic and anionic lipid membranes of dimyristoyl-L-alpha-phosphatidylcholine (DMPC) and dimyristoyl-L-alpha-phosphatidylglycerol (DMPG), respectively. The effect of cyclic oligosaccharide, beta-cyclodextrin (beta-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 beta-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 beta-CD resulted in a preferential interaction of the probe with CD. However, addition of beta-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.

Studies of Triton X-165–β-cyclodextrin interactions using both extrinsic and intrinsic fluorescence

“…In a different context, a detail study of the interaction of PSF with b-CD has been reported in one of our recent publications [55]. The essence of the study relevant to our present work is the value of the binding constant (K b = 82.0 l mole À1 ) for the formation of the PSF-b-CD inclusion complex.…”

“…The essence of the study relevant to our present work is the value of the binding constant (K b = 82.0 l mole À1 ) for the formation of the PSF-b-CD inclusion complex. The low value of K b implies a partial encapsulation of the probe inside the CD cavity which is justified from the relative dimensions of PSF and b-CD cavity [55].…”

Binding interaction of differently charged fluorescent probes with egg yolk phosphatidylcholine and the effect of β-cyclodextrin on the lipid–probe complexes: A fluorometric investigation

“…The lipid solution was prepared following the same method as adopted and illustrated in our previous publications [10,11]. The required amount of solid lipid was dissolved in 2:1 (v/v) chloroform:methanol mixture.…”

“…1(A)) [10,13]. On addition of EYPC lipid to the aqueous buffered solution of PSF, absorbance of PSF decreases with a bathochromic shift of the band maximum.…”

“…Interestingly, studies dealing with phospholipid-β-CD interaction and systematic photophysical studies involving lipid-probe-CD interactions are rather obscure. Considering the importance and biophysical relevance, we have been interested in such studies taking lipids as model membranes and fluorescent probes as model drugs [10][11][12].…”