Effect of three pluronic polymers on the transport of an organic cation across a POPG bilayer studied by Second Harmonic spectroscopy

Kintali, Srinivasarao; Varshney, G.K.; Das, Kaustuv

doi:10.1016/j.cplett.2017.07.002

Cited by 1 publication

(4 citation statements)

References 40 publications

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“…Before addition of LDS + ions, the observed E 2ω signal arises due to hyper-Rayleigh scattering from the liposomes . For all the cases, the instantaneous (<1 s) increase in the E 2ω (Δ E 2ω t0 ) as soon as LDS + ions were added is due to the rapid electrostatic adsorption of the LDS + ions on the negative charged outer bilayer surface as has been demonstrated in numerous studies earlier. − Therefore, the SH electric field, after addition of LDS + ions, is dominated by the E 2ω signal of LDS + ions ( E 2ω (LDS + )) which then decreases gradually due to transport of the LDS + ions from the outer to inner lipid bilayer . Although all the liposomes showed similar zeta potential values, it was observed that bilayer rigidity plays a crucial role in the adsorption of the LDS + ions (Δ E 2ω t0 ) on the outer surface of the bilayer.…”

Section: Resultssupporting

confidence: 84%

“…The SH experimental setup used for this study was identical to that described in our previous reports. − The average laser power used in the experiments was 500 mW, and the generated SH light (at 400 ± 2 nm) was detected at right angles with respect to the fundamental (800 nm) by a PMT using single photon counting technique. The SH signal integration time was kept at one second.…”

Section: Methodsmentioning

confidence: 99%

“…The electric field of the SH signal ( E 2ω ) was obtained from the observed SH signal ( I 2ω ) as − where I (2ω)dye+liposome ( t ) is the SH signal detected at 2ω at time t and I (2ω)background represents the contributions from the SH field generated by the liposome suspended in buffer solution. The decays of SH electric field ( E 2ω ) of LDS + ions are fitted to exponential decay functions of the following form: For fluorescence anisotropy measurements, DPH (1 μM) was incubated overnight with 100 μM liposome solutions and the temperature dependent fluorescence anisotropy were measured by exciting DPH at 360 ± 2 nm and monitoring the emission at 420 ± 4 nm.…”

Section: Methodsmentioning

confidence: 99%

“…Although the adsorption and bilayer transport of an ion is primarily driven by the electrostatic force of attraction between the oppositely charged ion and the bilayer head group, it can change drastically during the partitioning of a lipophilic molecule from aqueous to bilayer phase. ,,− For example, utilizing the SHG spectroscopic technique, we have shown that curcumin, a well-known drug, increases the adsorption and transport of a cationic hemicyanine dye, LDS + , across a negatively charged POPG (1-palmitoyl-2-oleoyl- sn -glycero-3-phospho-(1′-rac-glycerol) bilayer while partitioning from the aqueous to the bilayer phase . Interestingly, the increase in the adsorption of LDS + ions was attributed to curcumin induced release of Na + counterions from the bilayer head group region.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Curcumin Addition on the Adsorption and Transport of a Cationic Dye across DPPG-POPG Liposomes Probed by Second Harmonic Spectroscopy

2017

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The effect of addition of curcumin on the adsorption and transport characteristics of a cationic dye, LDS, across negatively charged bilayers composed of POPG and DPPG lipids were investigated by the interface selective second harmonic (SH) spectroscopic technique. Curcumin induced changes in the SH electric field signal of the LDS ions (E (LDS)) were observed to depend critically on the bilayer acyl chain saturation/unsaturation ratio (S/U). Following earlier works, the increase in the E (LDS) signal is attributed to the release of the Na counterions present in the head group region of the bilayer by curcumin and the decay of the E (LDS) signal is attributed to the bilayer intercalated state of curcumin. While the changes observed in the E (LDS) signal in the presence of POPG liposomes were consistent with our earlier study ( Varshney, G. K. et al. Langmuir , 2016 , 32 , 10415 - 10421 ), they were significantly different for DPPG liposomes, following curcumin addition. While the increase in the E (LDS) signal in the presence of POPG liposomes, is marginal (∼10-20%) and instantaneous (<1 s) followed by a rapid decay (completed within ∼100 s), in the presence of DPPG liposomes it was observed to increase slowly and at saturation shows a substantial increase (100-200%), following curcumin addition. When liposomes consisting of a mixture of POPG and DPPG lipids are used, curcumin induced kinetic characteristics of the E (LDS) signal showed a mixture of the individual kinetic characteristics observed for the unsaturated (POPG) and saturated (DPPG) liposomes. The observed kinetic trends of the E (LDS) signal following curcumin addition are explained on the basis of the relative strength of the Na-POPG and Na-DPPG interaction. Higher ordering of the lipid acyl chain region in DPPG liposome makes the Na-DPPG interaction much stronger than the Na-POPG interaction. Further, it is proposed that, in POPG-DPPG liposomes, individual domains of POPG and DPPG lipids exist at low temperature as suggested by the observed temperature dependent kinetic characteristics of the E (LDS) signal following curcumin addition. These domains are dependent on the S/U ratio and phase state of the bilayer. The gel phase was observed to be more conducive for individual domain formation. Results presented in this work not only support the notion that biological activity of curcumin is associated with its bilayer altering properties, but more interestingly it provides a qualitative insight about how bilayer phase separation can be achieved by modulating the hydrophobic interactions between the lipid acyl chains.

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