Nanoplasmonic Sensing and Capillary Electrophoresis for Fast Screening of Interactions between Phosphatidylcholine Biomembranes and Surfactants

Abstract

Nanoplasmonic sensing (NPS), based on localized surface plasmon resonance, with sensors composed of glass covered with golden nanodisks and overlaid with a SiO2 coating was applied in this study. Egg phosphatidylcholine (eggPC), being an easily accessible membrane-forming lipid, was used for preparation of biomimicking membranes. Small unilamellar vesicles with an approximate hydrodynamic diameter of 30 nm, formed by sonication in 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid buffer, were adsorbed within 10 min on the sensor surface either as intact vesicles or as a planar bilayer. The adsorbed biomembrane systems were further utilized for interaction studies with four different well-known surfactants (negatively and positively charged, zwitterionic, and nonionic) and each surfactant was tested at concentrations below and above the critical micelle concentration (CMC). Our results allowed the evaluation of different NPS patterns for every particular supported membrane system, surfactant, and its concentration. The most significant effect on the membrane was achieved upon the introduction of zwitterionic surfactant micelles, which in fact completely solubilized and removed the lipid membranes from the sensor surface. Other surfactant micelles interacted with the membranes and formed mixed structures remaining on the sensor surface. The studies performed at the concentrations below the CMCs of the surfactants showed that different mixed systems were formed. Depending on the supported membrane system and the type of surfactant, the mixed systems indicated different formation kinetics. Additionally, the final water rinse revealed the stability of the formed systems. To investigate the effect of the studied surfactants on the overall surface charge of the biomembrane, capillary electrophoresis (CE) experiments were carried out in parallel with the NPS analysis. The electroosmotic flow mobility of an eggPC-coated fused silica capillary was used to measure the total surface charge of the biomembrane after its treatment with the surfactants. Our results indicated in general good correlation between CE and NPS data. However, some discrepancies were seen while applying either zwitterionic or positively charged surfactants. This confirmed that CE analysis was able to provide additional data about the investigated systems. Taken together, the combination of NPS and CE proved to be an efficient way to describe the nature of interactions between biomimicking membranes and amphiphilic molecules.

Calcium Dependent Reversible Aggregation of Escherichia coli Biomimicking Vesicles Enables Formation of Supported Vesicle Layers on Silicon Dioxide

“…In our recent study, eggPC vesicles diluted in sodium HEPES buffer (Na-HEPES) formed a SVL on a SiO 2 sensor surface after treatment of the surface with 2 M HNO 3 . In contrast, eggPC SLB was formed on the same surface using Na-HEPES buffer containing 5 mM CaCl 2 (Ca-HEPES) (Duša et al, 2018). In the case of E. coli vesicles no SVL was formed when using the same HNO 3 treatment with Na-HEPES (data not shown).…”

“…The vesicles were prepared in the same manner as described in our previous study (Duša et al, 2018). Briefly, the calculated amount of 32.46 mM stock solution of E. coli total lipid extract dissolved in chloroform was transferred to a glass vial.…”

“…Recently, we developed a method for the immobilization of egg phosphatidylcholine (PC) onto SiO 2 nanoplasmonic sensing (NPS) sensor surfaces as supported lipid bilayers (SLBs) and SVLs (Duša et al, 2018). However, the phosphatidyl choline mixture from chicken egg is substantially different from the rather complex E. coli total lipid extract.…”

Intelligent polymeric micelles for multidrug co-delivery and cancer therapy

“…The stability of the micelle was maintained when the concentration of the copolymer in the solution was near or above the CMC. Conversely, the micelles were dissociated into a copolymer when the concentration of the copolymer in the solution was lower than the CMC [33,34]. Therefore, the effective reduction of the CMC of the micelles was advantageous for improving its stability in vivo.…”

Liposomes as models for membrane integrity

“…Nanoplasmonic sensing has been used to investigate membrane curvature 71 and how this affects membrane--protein interactions as well as the role of cholesterol in membrane stability 1 . The disruptive effects of amphiphillic compounds such as detergents upon small unilamellar vesicles 72 , and the effects of ionic liquids upon liposomes have also been investigated using this technique 1 . Recent research has also analysed lipid bilayers supported on silica--coated nanowell and nanodisk sensing platforms 72 .…”