title: Effect of Bilayer Partitioning of Curcumin on the Adsorption and Transport of a Cationic Dye Across POPG Liposomes Probed by Second-Harmonic Spectroscopy.
abstract: The effect of Curcumin partitioning into the bilayer during the adsorption and transport of a cationic dye, LDS, across a negatively charged POPG bilayer was investigated by the interface-selective second-harmonic (SH) spectroscopic technique. The intensity of SH electric field (E2ω) arising due to LDS adsorbed on the outer bilayer of the POPG liposome was observed to increase instantaneously (<1 s) following the addition of Curcumin. The fractional increase in the SH electric field (Ef2ω) and the bilayer transport rates (kT) of LDS were studied with respect to the pH of the solution and also with the Curcumin content in the lipid bilayer. Results obtained indicate that compared with the anionic form of the drug, its neutral form is more conducive of increasing the Ef2ωof LDS. With increasing Curcumin content in the lipid bilayer, two distinct regimes could be observed in terms of Ef2ωand kTvalues of LDS. For Curcumin:Lipid (C/L) ratio ≤0.02, the Ef2ωof LDS increases rapidly, while kTremains unchanged; and for C/L ratio ≥0.02, the Ef2ωvalues remains more or less constant, while there is a significant (∼40 times) increase followed by a modest increase in the kTvalues of LDS. The observed results support an earlier two-state binding model of Curcumin with the POPG bilayer. In addition, it is further proposed that at low C/L ratio Curcumin binds to the surface of the bilayer replacing the counterions (Na+) bound to the lipid head groups, which changes the bilayer surface charge density, thereby causing more LDS cations to adsorb on the bilayer surface. At high C/L ratio, Curcumin intercalates within the hydrophobic domain of the bilayer, altering its hydrophobicity and inducing enhanced transport of the LDS cation. Results presented in this work provide further insights into how Curcumin alters bilayer properties when it partitions from the aqueous to the bilayer phase.
authors.affiliation: Optical Spectroscopy & Diagnostic Lab, Laser Bio-Medical Applications Section, Raja Ramanna Center for Advanced Technology , Indore, Madhya Pradesh 452013, India.|Homi Bhabha National Institute , Training School Complex, Anushakti Nagar, Mumbai 400094, India.
authors.forename: G K
authors.initials: GK
authors.lastname: Varshney
authors.affiliation: Optical Spectroscopy & Diagnostic Lab, Laser Bio-Medical Applications Section, Raja Ramanna Center for Advanced Technology , Indore, Madhya Pradesh 452013, India.|Homi Bhabha National Institute , Training School Complex, Anushakti Nagar, Mumbai 400094, India.
authors.forename: S R
authors.initials: SR
authors.lastname: Kintali
authors.affiliation: Optical Spectroscopy & Diagnostic Lab, Laser Bio-Medical Applications Section, Raja Ramanna Center for Advanced Technology , Indore, Madhya Pradesh 452013, India.|Homi Bhabha National Institute , Training School Complex, Anushakti Nagar, Mumbai 400094, India.
authors.forename: P K
authors.initials: PK
authors.lastname: Gupta
authors.affiliation: Optical Spectroscopy & Diagnostic Lab, Laser Bio-Medical Applications Section, Raja Ramanna Center for Advanced Technology , Indore, Madhya Pradesh 452013, India.|Homi Bhabha National Institute , Training School Complex, Anushakti Nagar, Mumbai 400094, India.
authors.forename: K
authors.initials: K
authors.lastname: Das
mesh_terms: D000327:Adsorption / Q000187:drug effects; D055592:Biophysical Phenomena / Q000187:drug effects; D002070:Butadienes / Q000737:chemistry*; D003474:Curcumin / Q000737:chemistry*; D004058:Diffusion; D005456:Fluorescent Dyes / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D010715:Phosphatidylglycerols / Q000737:chemistry*; D011726:Pyridinium Compounds / Q000737:chemistry*; D000073798:Second Harmonic Generation Microscopy
chemical_list: D002070:Butadienes; D005456:Fluorescent Dyes; C582868:LDS-698; D008051:Lipid Bilayers; D008081:Liposomes; D010715:Phosphatidylglycerols; D011726:Pyridinium Compounds; C060037:1-palmitoyl-2-oleoylglycero-3-phosphoglycerol; D003474:Curcumin