Investigation of Drug–Model Cell Membrane Interactions Using Sum Frequency Generation Vibrational Spectroscopy: A Case Study of Chlorpromazine

Abstract

Sum frequency generation (SFG) vibrational spectroscopy and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy were applied to study interactions between an antipsychotic agent, chlorpromazine (CPZ), and model cell membranes consisting of either distearoylphosphatidylcholine (DSPC) or dipalmitoylphosphatidylglycerol (DPPG). The PC and PG lipids represent the zwitterionic and anionic components of the cell membranes, respectively. For an isotopically asymmetric bilayer composed of a deuterated lipid leaflet and a hydrogenated lipid leaflet, the time-dependent SFG signals from the lipids revealed that CPZ can significantly accelerate the flip-flop process of the neutral DSPC bilayer and such an acceleration effect is more pronounced at higher CPZ concentrations. While for the negatively charged DPPG bilayer, it was found that CPZ molecules can immediately bind to and disrupt the outer lipid leaflet and then gradually reduce the ordering of the inner lipid leaflet. A higher CPZ concentration in the subphase leads to a faster disordering effect on the inner leaflet. The association of CPZ to the lipid membranes can be verified by the change in the SFG spectra of the OH stretching vibration of the interfacial water molecules. ATR-FTIR results revealed that addition of CPZ to the subphase did not exert significant effect on the dDSPC/dDSPC bilayer, especially at low CPZ concentrations (<2 mM). It was found that CPZ can cause gel-to-fluid phase transition of the dDPPG/dDPPG bilayer at CPZ concentrations below 2 mM, and higher CPZ concentrations can lead to dissolution of the bilayer. This work demonstrated that SFG (along with ATR-FTIR) is a powerful in situ and label-free technique that can be used to study various aspects of the drug–membrane interactions at the molecular level.

Molecular interactions between gold nanoparticles and model cell membranes

“…[31][32][33][34][35][36][37][38][39][40] SFG is a second order nonlinear laser spectroscopy with intrinsic surface/interface sensitivity due to its special selection rule. SFG can provide molecular details on how membrane lipid bilayers interact with various molecules or materials.…”

“…SFG can provide molecular details on how membrane lipid bilayers interact with various molecules or materials. [31][32][33][34][35][36][37][38][39][40] SFG has been widely applied to study the interactions between lipid bilayers and proteins/peptides such as melittin, 31 tachyplesin I, 32 magainin 2, 33 MSI-78, 34 alamethicin, 35-37 G Protein-Coupled Receptor Kinase 5, 38 and human islet amyloid polypeptide 40 and so on. 41,42 SFG can also detect and monitor the molecular structure and dynamics of both lipids and their interacting molecules in situ in real time without exogenous labeling.…”

Qualitative and Quantitative Analyses of the Molecular-Level Interaction between Memantine and Model Cell Membranes

“…Finally, Both I CH 3 and I CD 3 remained unchanged until around 2000 s, suggesting that the flip-flop process of the dDPPC/DPPC bilayer finished in a shorter time as compared with that of the dDSPC/DSPC bilayer. 7 For comparison, the time-dependent SFG signal intensities of I CH 3 and I CD 3 for the dDPPC/DPPC bilayer with the addition of 5 mM memantine were also monitored ( Figure 2B). For a quantitative comparison, all the time-dependent curves in Figure 2 were fitted using a reported method 6,7,50,51 (see details in the Supporting Information).…”

“…7 For comparison, the time-dependent SFG signal intensities of I CH 3 and I CD 3 for the dDPPC/DPPC bilayer with the addition of 5 mM memantine were also monitored ( Figure 2B). For a quantitative comparison, all the time-dependent curves in Figure 2 were fitted using a reported method 6,7,50,51 (see details in the Supporting Information). The fitting results for the 2875 cm −1 revealed that the flip-flop rate (k) and the half-life (t 1/2 ) of the neat lipid bilayer were (3.6 ± 0.8) × 10 −4 s −1 and (9.6 ± 2.7) × 10 2 s, respectively.…”

In Situ Visualization of Lipid Raft Domains by Fluorescent Glycol Chitosan Derivatives

“…Model lipid membranes prepared in the form of supported lipid bilayers (SLBs) [37][38][39][40][41][42][43][44][45][46][47] and giant unilamellar vesicles (GUVs) [48][49][50][51][52][53][54] were applied as the platforms for imaging phase-separated lipid raft domains using confocal fluorescence microscopy.…”