Supported Lipid Bilayer Platform for Characterizing the Membrane-Disruptive Behaviors of Triton X-100 and Potential Detergent Replacements

Triton X-100 (TX-100) is a widely used detergent to prevent viral contamination of manufactured biologicals and biopharmaceuticals, and acts by disrupting membrane-enveloped virus particles. However, environmental concerns about ecotoxic byproducts are leading to TX-100 phase out and there is an outstanding need to identify functionally equivalent detergents that can potentially replace TX-100. To date, a few detergent candidates have been identified based on viral inactivation studies, while direct mechanistic comparison of TX-100 and potential replacements from a biophysical interaction perspective is warranted. Herein, we employed a supported lipid bilayer (SLB) platform to comparatively evaluate the membrane-disruptive properties of TX-100 and a potential replacement, Simulsol SL 11W (SL-11W), and identified key mechanistic differences in terms of how the two detergents interact with phospholipid membranes. Quartz crystal microbalance-dissipation (QCM-D) measurements revealed that TX-100 was more potent and induced rapid, irreversible, and complete membrane solubilization, whereas SL-11W caused more gradual, reversible membrane budding and did not induce extensive membrane solubilization. The results further demonstrated that TX-100 and SL-11W both exhibit concentration-dependent interaction behaviors and were only active at or above their respective critical micelle concentration (CMC) values. Collectively, our findings demonstrate that TX-100 and SL-11W have distinct membrane-disruptive effects in terms of potency, mechanism of action, and interaction kinetics, and the SLB platform approach can support the development of biophysical assays to efficiently test potential TX-100 replacements.

The Mechanism of Vesicle Solubilization by the Detergent Sodium Dodecyl Sulfate

Membrane solubilization by sodium dodecyl sulfate (SDS) is indispensable for many established biotech-nological applications, including viral inactivation and protein extraction. Although the ensemble thermo-dynamics have been thoroughly explored, the underlying molecular dynamics have remained inaccessible, owing to major limitations of traditional measurement tools. Here, we integrate multiple advanced biophysical approaches to gain multi-angle insight into the time-dependence and fundamental kinetic steps associated with the solubilization of single sub-micron sized vesicles in response to SDS. We find that the accumulation of SDS molecules on in-tact vesicles triggers biphasic solubilization kinetics comprising an initial vesicle expansion event followed by rapid lipid loss and micellization. Our findings support a general mechanism of detergent-induced membrane solubilization and we expect the framework of correlative biophysical technologies presented here will form a general platform for elucidating the complex kinetics of membrane perturbation induced by a wide variety of surfactants and disrupting agents.

Structural Modification of Styrene Maleic Anhydride Copolymers for Plant Bioactive Compound Extraction

Ability of poly (styrene-alt-maleic anhydride) (PSMA) to undergo a conformational transition into an amphipathic α-helix coil offers one possible mechanism by which PSMA surface activity can be switched on or off in response to the pH change. This behaviour allows it to be useful in membrane solubilization for extraction technology. Bioactive compounds are recovered from plant tissues for different reasons. One of the most important reasons is due to the increased demand in nutraceuticals market and modern therapeutics. Despite this, aqueous-based extraction of these compounds has been reported to give low extraction yield. A development of new green extraction protocol is still a challenging task for all researchers nowadays. This study demonstrated, for the first time, possible use of PSMA as a lysis agent for plant bioactive compound extraction. To enhance its membrane affinity at physiological pH, the polymer was esterified with methanol. Both PSMA and its derivative (ePSMA) were characterized in terms of their membrane binding affinity through a combined use of both surface characterization and physical techniques. Analysis of the ternary phase diagrams suggested that ePSMA could facilitate stronger hydrophobically-driven interactions with the lipid. This was convinced by the reduced critical PSMA/lipid mass ratio from 7:1 (PSMA) to 1:1 (ePSMA), as observed in the ternary phase diagrams. Last but not the least, the crude extracts of Coffea robusta leaves obtained from ePSMA-based extraction showed a total phenolic content of 20.32±0.75 mg/g sample, significantly higher than that from the PSMA- (14.24±1.27 mg/g sample) and aqueous-based (16.33±1.03 mg/g sample) extractions. A structural manipulation of PSMA is thus a key to tailor its membrane solubilization and so, the extraction efficacy of bioactive compounds from plant cells.