Curvature-sensing peptide inhibits tumour-derived exosomes for enhanced cancer immunotherapy.

Tumour-derived exosomes (T-EXOs) impede immune checkpoint blockade therapies, motivating pharmacological efforts to inhibit them. Inspired by how antiviral curvature-sensing peptides disrupt membrane-enveloped virus particles in the exosome size range, we devised a broadly useful strategy that repurposes an engineered antiviral peptide to disrupt membrane-enveloped T-EXOs for synergistic cancer immunotherapy. The membrane-targeting peptide inhibits T-EXOs from various cancer types and exhibits pH-enhanced membrane disruption relevant to the tumour microenvironment. The combination of T-EXO-disrupting peptide and programmed cell death protein-1 antibody-based immune checkpoint blockade therapy improves treatment outcomes in tumour-bearing mice. Peptide-mediated disruption of T-EXOs not only reduces levels of circulating exosomal programmed death-ligand 1, but also restores CD8+ T cell effector function, prevents premetastatic niche formation and reshapes the tumour microenvironment in vivo. Our findings demonstrate that peptide-induced T-EXO depletion can enhance cancer immunotherapy and support the potential of peptide engineering for exosome-targeting applications.

Membrane-Disruptive Effects of Fatty Acid and Monoglyceride Mitigants on E. coli Bacteria-Derived Tethered Lipid Bilayers.

We report electrochemical impedance spectroscopy measurements to characterize the membrane-disruptive properties of medium-chain fatty acid and monoglyceride mitigants interacting with tethered bilayer lipid membrane (tBLM) platforms composed of E. coli bacterial lipid extracts. The tested mitigants included capric acid (CA) and monocaprin (MC) with 10-carbon long hydrocarbon chains, and lauric acid (LA) and glycerol monolaurate (GML) with 12-carbon long hydrocarbon chains. All four mitigants disrupted E. coli tBLM platforms above their respective critical micelle concentration (CMC) values; however, there were marked differences in the extent of membrane disruption. In general, CA and MC caused larger changes in ionic permeability and structural damage, whereas the membrane-disruptive effects of LA and GML were appreciably smaller. Importantly, the distinct magnitudes of permeability changes agreed well with the known antibacterial activity levels of the different mitigants against E. coli, whereby CA and MC are inhibitory and LA and GML are non-inhibitory. Mechanistic insights obtained from the EIS data help to rationalize why CA and MC are more effective than LA and GML at disrupting E. coli membranes, and these measurement capabilities support the potential of utilizing bacterial lipid-derived tethered lipid bilayers for predictive assessment of antibacterial drug candidates and mitigants.

pH-Modulated Nanoarchitectonics for Enhancement of Multivalency-Induced Vesicle Shape Deformation at Receptor-Presenting Lipid Membrane Interfaces.

Multivalent ligand-receptor interactions between receptor-presenting lipid membranes and ligand-modified biological and biomimetic nanoparticles influence cellular entry and fusion processes. Environmental pH changes can drive these membrane-related interactions by affecting membrane nanomechanical properties. Quantitatively, however, the corresponding effects on high-curvature, sub-100 nm lipid vesicles are scarcely understood, especially in the multivalent binding context. Herein, we employed the label-free localized surface plasmon resonance (LSPR) sensing technique to track the multivalent attachment kinetics, shape deformation, and surface coverage of biotin ligand-functionalized, zwitterionic lipid vesicles with different ligand densities on a streptavidin receptor-coated supported lipid bilayer under varying pH conditions (4.5, 6, 7.5). Our results demonstrate that more extensive multivalent interactions caused greater vesicle shape deformation across the tested pH conditions, which affected vesicle surface packing as well. Notably, there were also pH-specific differences, i.e., a higher degree of vesicle shape deformation was triggered at a lower multivalent binding energy in pH 4.5 than in pH 6 and 7.5 conditions. These findings support that the nanomechanical properties of high-curvature lipid membranes, especially the membrane bending energy and the corresponding responsiveness to multivalent binding interactions, are sensitive to solution pH, and indicate that multivalency-induced vesicle shape deformation occurs slightly more readily in acidic pH conditions relevant to biological environments.

Unraveling Membrane-Disruptive Properties of Sodium Lauroyl Lactylate and Its Hydrolytic Products: A QCM-D and EIS Study.

Membrane-disrupting lactylates are an important class of surfactant molecules that are esterified adducts of fatty acid and lactic acid and possess industrially attractive properties, such as high antimicrobial potency and hydrophilicity. Compared with antimicrobial lipids such as free fatty acids and monoglycerides, the membrane-disruptive properties of lactylates have been scarcely investigated from a biophysical perspective, and addressing this gap is important to build a molecular-level understanding of how lactylates work. Herein, using the quartz crystal microbalance-dissipation (QCM-D) and electrochemical impedance spectroscopy (EIS) techniques, we investigated the real-time, membrane-disruptive interactions between sodium lauroyl lactylate (SLL)-a promising lactylate with a 12-carbon-long, saturated hydrocarbon chain-and supported lipid bilayer (SLB) and tethered bilayer lipid membrane (tBLM) platforms. For comparison, hydrolytic products of SLL that may be generated in biological environments, i.e., lauric acid (LA) and lactic acid (LacA), were also tested individually and as a mixture, along with a structurally related surfactant (sodium dodecyl sulfate, SDS). While SLL, LA, and SDS all had equivalent chain properties and critical micelle concentration (CMC) values, our findings reveal that SLL exhibits distinct membrane-disruptive properties that lie in between the rapid, complete solubilizing activity of SDS and the more modest disruptive properties of LA. Interestingly, the hydrolytic products of SLL, i.e., the LA + LacA mixture, induced a greater degree of transient, reversible membrane morphological changes but ultimately less permanent membrane disruption than SLL. These molecular-level insights support that careful tuning of antimicrobial lipid headgroup properties can modulate the spectrum of membrane-disruptive interactions, offering a pathway to design surfactants with tailored biodegradation profiles and reinforcing that SLL has attractive biophysical merits as a membrane-disrupting antimicrobial drug candidate.

Effect of Membrane Curvature Nanoarchitectonics on Membrane-Disruptive Interactions of Antimicrobial Lipids and Surfactants.

Single-chain lipid amphiphiles such as fatty acids and monoglycerides along with structurally related surfactants have received significant attention as membrane-disrupting antimicrobials to inhibit bacteria and viruses. Such promise has motivated deeper exploration of how these compounds disrupt phospholipid membranes, and the membrane-mimicking, supported lipid bilayer (SLB) platform has provided a useful model system to evaluate corresponding mechanisms of action and potency levels. Even so, it remains largely unknown how biologically relevant membrane properties, such as sub-100 nm membrane curvature, might affect these membrane-disruptive interactions, especially from a nanoarchitectonics perspective. Herein, using the quartz crystal microbalance-dissipation (QCM-D) technique, we fabricated intact vesicle adlayers composed of different-size vesicles (70 or 120 nm diameter) with varying degrees of membrane curvature on a titanium oxide surface and tracked changes in vesicle adlayer properties upon adding lauric acid (LA), glycerol monolaurate (GML), or sodium dodecyl sulfate (SDS). Above their critical micelle concentration (CMC) values, LA and GML caused QCM-D measurement shifts associated with tubule- and bud-like formation, respectively, and both compounds interacted similarly with small (high curvature) and large (low curvature) vesicles. In marked contrast, SDS exhibited distinct interactions with small and large vesicles. For large vesicles, SDS caused nearly complete membrane solubilization in a CMC-independent manner, whereas SDS was largely ineffective at solubilizing small vesicles at all tested concentrations. We rationalize these experimental observations by taking into account the interplay of the headgroup properties of LA, GML, and SDS and curvature-induced membrane geometry, and our findings demonstrate that membrane curvature nanoarchitectonics can strongly influence the membrane interaction profiles of antimicrobial lipids and surfactants.

Unraveling How Cholesterol Affects Multivalency-Induced Membrane Deformation of Sub-100 nm Lipid Vesicles.

Cholesterol plays a critical role in modulating the lipid membrane properties of biological and biomimetic systems and recent attention has focused on its role in the functions of sub-100 nm lipid vesicles and lipid nanoparticles. These functions often rely on multivalent ligand-receptor interactions involving membrane attachment and dynamic shape transformations while the extent to which cholesterol can influence such interaction processes is largely unknown. To address this question, herein, we investigated the attachment of sub-100 nm lipid vesicles containing varying cholesterol fractions (0-45 mol %) to membrane-mimicking supported lipid bilayer (SLB) platforms. Biotinylated lipids and streptavidin proteins were used as model ligands and receptors, respectively, while the localized surface plasmon resonance sensing technique was employed to track vesicle attachment kinetics in combination with analytical modeling of vesicle shape changes. Across various conditions mimicking low and high multivalency, our findings revealed that cholesterol-containing vesicles could bind to receptor-functionalized membranes but underwent appreciably less multivalency-induced shape deformation than vesicles without cholesterol, which can be explained by a cholesterol-mediated increase in membrane bending rigidity. Interestingly, the extent of vesicle deformation that occurred in response to increasingly strong multivalent interactions was less pronounced for vesicles with greater cholesterol fraction. The latter trend was rationalized by taking into account the strong dependence of the membrane bending energy on the area of the vesicle-SLB contact region and such insights can aid the engineering of membrane-enveloped nanoparticles with tailored biophysical properties.

Chemical design principles of next-generation antiviral surface coatings.

The ongoing coronavirus disease 2019 (COVID-19) pandemic has accelerated efforts to develop high-performance antiviral surface coatings while highlighting the need to build a strong mechanistic understanding of the chemical design principles that underpin antiviral surface coatings. Herein, we critically summarize the latest efforts to develop antiviral surface coatings that exhibit virus-inactivating functions through disrupting lipid envelopes or protein capsids. Particular attention is focused on how cutting-edge advances in material science are being applied to engineer antiviral surface coatings with tailored molecular-level properties to inhibit membrane-enveloped and non-enveloped viruses. Key topics covered include surfaces functionalized with organic and inorganic compounds and nanoparticles to inhibit viruses, and self-cleaning surfaces that incorporate photocatalysts and triplet photosensitizers. Application examples to stop COVID-19 are also introduced and demonstrate how the integration of chemical design principles and advanced material fabrication strategies are leading to next-generation surface coatings that can help thwart viral pandemics and other infectious disease threats.

Mechanistic Evaluation of Antimicrobial Lipid Interactions with Tethered Lipid Bilayers by Electrochemical Impedance Spectroscopy.

There is extensive interest in developing real-time biosensing strategies to characterize the membrane-disruptive properties of antimicrobial lipids and surfactants. Currently used biosensing strategies mainly focus on tracking membrane morphological changes such as budding and tubule formation, while there is an outstanding need to develop a label-free biosensing strategy to directly evaluate the molecular-level mechanistic details by which antimicrobial lipids and surfactants disrupt lipid membranes. Herein, using electrochemical impedance spectroscopy (EIS), we conducted label-free biosensing measurements to track the real-time interactions between three representative compounds-glycerol monolaurate (GML), lauric acid (LA), and sodium dodecyl sulfate (SDS)-and a tethered bilayer lipid membrane (tBLM) platform. The EIS measurements verified that all three compounds are mainly active above their respective critical micelle concentration (CMC) values, while also revealing that GML induces irreversible membrane damage whereas the membrane-disruptive effects of LA are largely reversible. In addition, SDS micelles caused membrane solubilization, while SDS monomers still caused membrane defect formation, shedding light on how antimicrobial lipids and surfactants can be active in, not only micellar form, but also as monomers in some cases. These findings expand our mechanistic knowledge of how antimicrobial lipids and surfactants disrupt lipid membranes and demonstrate the analytical merits of utilizing the EIS sensing approach to comparatively evaluate membrane-disruptive antimicrobial compounds.

Distinct Binding Properties of Neutravidin and Streptavidin Proteins to Biotinylated Supported Lipid Bilayers: Implications for Sensor Functionalization.

The exceptional strength and stability of noncovalent avidin-biotin binding is widely utilized as an effective bioconjugation strategy in various biosensing applications, and neutravidin and streptavidin proteins are two commonly used avidin analogues. It is often regarded that the biotin-binding abilities of neutravidin and streptavidin are similar, and hence their use is interchangeable; however, a deeper examination of how these two proteins attach to sensor surfaces is needed to develop reliable surface functionalization options. Herein, we conducted quartz crystal microbalance-dissipation (QCM-D) biosensing experiments to investigate neutravidin and streptavidin binding to biotinylated supported lipid bilayers (SLBs) in different pH conditions. While streptavidin binding to biotinylated lipid receptors was stable and robust across the tested pH conditions, neutravidin binding strongly depended on the solution pH and was greater with increasingly acidic pH conditions. These findings led us to propose a two-step mechanistic model, whereby streptavidin and neutravidin binding to biotinylated sensing interfaces first involves nonspecific protein adsorption that is mainly influenced by electrostatic interactions, followed by structural rearrangement of adsorbed proteins to specifically bind to biotin functional groups. Practically, our findings demonstrate that streptavidin is preferable to neutravidin for constructing SLB-based sensing platforms and can improve sensing performance for detecting antibody-antigen interactions.

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.

Biophysical Characterization of LTX-315 Anticancer Peptide Interactions with Model Membrane Platforms: Effect of Membrane Surface Charge.

LTX-315 is a clinical-stage, anticancer peptide therapeutic that disrupts cancer cell membranes. Existing mechanistic knowledge about LTX-315 has been obtained from cell-based biological assays, and there is an outstanding need to directly characterize the corresponding membrane-peptide interactions from a biophysical perspective. Herein, we investigated the membrane-disruptive properties of the LTX-315 peptide using three cell-membrane-mimicking membrane platforms on solid supports, namely the supported lipid bilayer, intact vesicle adlayer, and tethered lipid bilayer, in combination with quartz crystal microbalance-dissipation (QCM-D) and electrochemical impedance spectroscopy (EIS) measurements. The results showed that the cationic LTX-315 peptide selectively disrupted negatively charged phospholipid membranes to a greater extent than zwitterionic or positively charged phospholipid membranes, whereby electrostatic interactions were the main factor to influence peptide attachment and membrane curvature was a secondary factor. Of note, the EIS measurements showed that the LTX-315 peptide extensively and irreversibly permeabilized negatively charged, tethered lipid bilayers that contained high phosphatidylserine lipid levels representative of the outer leaflet of cancer cell membranes, while circular dichroism (CD) spectroscopy experiments indicated that the LTX-315 peptide was structureless and the corresponding membrane-disruptive interactions did not involve peptide conformational changes. Dynamic light scattering (DLS) measurements further verified that the LTX-315 peptide selectively caused irreversible disruption of negatively charged lipid vesicles. Together, our findings demonstrate that the LTX-315 peptide preferentially disrupts negatively charged phospholipid membranes in an irreversible manner, which reinforces its potential as an emerging cancer immunotherapy and offers a biophysical framework to guide future peptide engineering efforts.

Comparing Protein Adsorption onto Alumina and Silica Nanomaterial Surfaces: Clues for Vaccine Adjuvant Development.

Protein adsorption onto nanomaterial surfaces is important for various nanobiotechnology applications such as biosensors and drug delivery. Within this scope, there is growing interest to develop alumina- and silica-based nanomaterial vaccine adjuvants and an outstanding need to compare protein adsorption onto alumina- and silica-based nanomaterial surfaces. Herein, using alumina- and silica-coated arrays of silver nanodisks with plasmonic properties, we conducted localized surface plasmon resonance (LSPR) experiments to evaluate real-time adsorption of bovine serum albumin (BSA) protein onto alumina and silica surfaces. BSA monomers and oligomers were prepared in different water-ethanol mixtures and both adsorbing species consistently showed quicker adsorption kinetics and more extensive adsorption-related spreading on alumina surfaces as compared to on silica surfaces. We rationalized these experimental observations in terms of the electrostatic forces governing protein-surface interactions on the two nanomaterial surfaces and the results support that more rigidly attached BSA protein-based coatings can be formed on alumina-based nanomaterial surfaces. Collectively, the findings in this study provide fundamental insight into protein-surface interactions at nanomaterial interfaces and can help to guide the development of protein-based coatings for medical and biotechnology applications such as vaccines.

Lipid Nanoparticle Technology for Delivering Biologically Active Fatty Acids and Monoglycerides.

There is enormous interest in utilizing biologically active fatty acids and monoglycerides to treat phospholipid membrane-related medical diseases, especially with the global health importance of membrane-enveloped viruses and bacteria. However, it is difficult to practically deliver lipophilic fatty acids and monoglycerides for therapeutic applications, which has led to the emergence of lipid nanoparticle platforms that support molecular encapsulation and functional presentation. Herein, we introduce various classes of lipid nanoparticle technology and critically examine the latest progress in utilizing lipid nanoparticles to deliver fatty acids and monoglycerides in order to treat medical diseases related to infectious pathogens, cancer, and inflammation. Particular emphasis is placed on understanding how nanoparticle structure is related to biological function in terms of mechanism, potency, selectivity, and targeting. We also discuss translational opportunities and regulatory needs for utilizing lipid nanoparticles to deliver fatty acids and monoglycerides, including unmet clinical opportunities.

Cyclodextrin-based Pickering emulsions: functional properties and drug delivery applications.

Cyclodextrins (CDs) are biocompatible, cyclic oligosaccharides that are widely used in various industrial applications and have intriguing interfacial science properties. While CD molecules typically have low surface activity, they are capable of stabilizing emulsions by inclusion complexation of oil-phase components at the oil/water interface, which results in Pickering emulsion formation. Such surfactant-free formulations have gained considerable attention in recent years, owing to their enhanced physical stability, improved tolerability, and superior environmental compatibility compared to conventional, surfactant-based emulsions. In this review, we critically describe the latest insights into the molecular mechanisms involved in CD stabilization of Pickering emulsions, including covering practical aspects such as methods to prepare CD-based Pickering emulsions, lipid encapsulation, and relevant stability issues. In addition, the rheological and textural features of CD-based Pickering emulsions are discussed and particular attention is focused on promising examples for drug delivery, cosmetic, and nutraceutical applications. The functionality of currently developed CD-based Pickering emulsions is also summarised, including examples such as antifungal uses, and we close by discussing emerging possibilities to utilize the molecular encapsulation of CD-based emulsions for translational medicine applications in the antiviral and antibacterial spaces.

Supported Lipid Bilayer Formation from Phospholipid-Fatty Acid Bicellar Mixtures.

Supported lipid bilayers (SLBs) are versatile cell membrane-mimicking biointerfaces for various applications such as biosensors and drug delivery systems, and there is broad interest in developing simple, cost-effective methods to achieve SLB fabrication. One promising approach involves the deposition of quasi-two-dimensional bicelle nanostructures that are composed of long-chain phospholipids and either short-chain phospholipids or detergent molecules. While a variety of long-chain phospholipids have been used to prepare bicelles for SLB fabrication applications, only two short-chain phospholipids, 1,2-dihexanoyl-sn-glycero-3-phosphocholine and 1,2-diheptanoyl-sn-glycero-3-phosphocholine (collectively referred to as DHPC), have been investigated. There remains an outstanding need to identify natural alternatives to DHPC, especially ones that are more affordable, to improve fabrication prospects and application opportunities. Herein, we explored the potential to fabricate SLBs from bicellar mixtures composed of long-chain phospholipids and lauric acid (LA), which is a low-cost, naturally abundant fatty acid that is widely used in soapmaking and various industrial applications. Quartz crystal microbalance-dissipation (QCM-D) experiments were conducted to track bicelle adsorption onto silica surfaces as a function of bicelle composition and lipid concentration, along with time-lapse fluorescence microscopy imaging and fluorescence recovery after photobleaching (FRAP) experiments to further characterize lipid adlayer properties. The results identified optimal conditions where it is possible to efficiently form SLBs from LA-containing bicelles at low lipid concentrations while also unraveling mechanistic insights into the bicelle-mediated SLB formation process and verifying that LA-containing bicelles are biocompatible with human cells for surface coating applications.

Unraveling How Ethanol-Induced Conformational Changes Affect BSA Protein Adsorption onto Silica Surfaces.

Protein adsorption at solid-liquid interfaces is highly relevant to a wide range of applications such as biosensors, drug delivery, and pharmaceuticals. Understanding how protein conformation in bulk solution impacts adsorption behavior is fundamentally important and could also lead to the development of improved protein-based coatings. To date, relevant studies have been conducted in aqueous solutions, while it remains largely unknown how organic solvents and more specifically solvent-induced conformational changes might influence protein adsorption. Herein, using the quartz crystal microbalance-dissipation (QCM-D) and localized surface plasmon resonance (LSPR) techniques, we systematically investigated the real-time adsorption behavior of bovine serum albumin (BSA) protein onto silica surfaces in different water-ethanol mixtures ranging from 0 to 60% (v/v) ethanol. The results showed that there was greater protein adsorption at higher ethanol fractions in the 10-30% range, while more complex adsorption profiles were observed in the 40-60% range. The combination of QCM-D and LSPR measurements led us to further identify specific cases in water-ethanol mixtures where washing steps caused densification of the adsorbed protein layer as opposed to typical desorption of weakly adsorbed molecules in aqueous conditions. We discuss mechanistic factors that drive these overall adsorption trends by taking into account how ethanol fraction affects BSA conformation in bulk solution. Together, our findings demonstrate that BSA proteins can adsorb onto silica surfaces across a wide range of water-ethanol mixture conditions, while specific adsorption profiles depended on the ethanol fraction in a manner closely linked to solution-phase conformational properties.

Medicinal Activities and Nanomedicine Delivery Strategies for Brucea javanica Oil and Its Molecular Components.

Brucea javanica oil (BJO) is widely used in traditional Chinese medicine to treat various types of cancer and inflammatory diseases. There is significant interest in understanding the medicinal activities of BJO and its molecular components, especially quassinoids, and in exploring how they can be incorporated into nanomedicine delivery strategies for improved application prospects. Herein, we cover the latest progress in developing different classes of drug delivery vehicles, including nanoemulsions, liposomes, nanostructured lipid carriers, and spongosomes, to encapsulate BJO and purified quassinoids. An introduction to the composition and medicinal activities of BJO and its molecular components, including quassinoids and fatty acids, is first provided. Application examples involving each type of drug delivery vehicle are then critically presented. Future opportunities for nanomedicine delivery strategies in the field are also discussed and considered within the context of translational medicine needs and drug development processes.

Therapeutic treatment of Zika virus infection using a brain-penetrating antiviral peptide.

Zika virus is a mosquito-borne virus that is associated with neurodegenerative diseases, including Guillain-Barré syndrome1 and congenital Zika syndrome2. As Zika virus targets the nervous system, there is an urgent need to develop therapeutic strategies that inhibit Zika virus infection in the brain. Here, we have engineered a brain-penetrating peptide that works against Zika virus and other mosquito-borne viruses. We evaluated the therapeutic efficacy of the peptide in a lethal Zika virus mouse model exhibiting systemic and brain infection. Therapeutic treatment protected against mortality and markedly reduced clinical symptoms, viral loads and neuroinflammation, as well as mitigated microgliosis, neurodegeneration and brain damage. In addition to controlling systemic infection, the peptide crossed the blood-brain barrier to reduce viral loads in the brain and protected against Zika-virus-induced blood-brain barrier injury. Our findings demonstrate how engineering strategies can be applied to develop peptide therapeutics and support the potential of a brain-penetrating peptide to treat neurotropic viral infections.

Characterizing the Membrane-Disruptive Behavior of Dodecylglycerol Using Supported Lipid Bilayers.

Monoglycerides are esterified adducts of fatty acid and glycerol molecules that disrupt phospholipid membranes, leading to a wide range of biological functions such as antimicrobial activity. Among monoglycerides, glycerol monolaurate (GML) exhibits particularly high antimicrobial activity, although enzymatic hydrolysis of its ester group can diminish potency. Consequently, there have been efforts to identify more chemically stable versions of GML, most notably its alkylglycerol ether equivalent called dodecylglycerol (DDG). However, despite high structural similarity, biological studies indicate that DDG and GML are not functionally equivalent and it has been speculated that the two compounds might have different interaction profiles with phospholipid membranes. To address this outstanding question, herein, we employed supported lipid bilayer (SLB) platforms to experimentally characterize the interactions of DDG with phospholipid membranes. Quartz crystal microbalance-dissipation experiments identified that DDG causes concentration-dependent membrane morphological changes in SLBs and the overall extent of membrane remodeling events was greater than that caused by GML. In addition, time-lapsed fluorescence microscopy imaging experiments revealed that DDG causes extensive membrane tubulation that is distinct from how GML induces membrane budding. We discuss how differences in the head group properties of DDG and GML contribute to distinct membrane interaction profiles, offering insight into how the molecular design of DDG not only improves chemical stability but also enhances membrane-disruptive activity.

Influence of NaCl Concentration on Bicelle-Mediated SLB Formation.

The deposition of two-dimensional bicellar disks on hydrophilic surfaces is an emerging approach to fabricate supported lipid bilayers (SLBs) that requires minimal sample preparation, works at low lipid concentrations, and yields high-quality SLBs. While basic operating steps in the fabrication protocol mimic aspects of the conventional vesicle fusion method, lipid bicelles and vesicles have distinct architectural properties, and understanding how experimental parameters affect the efficiency of bicelle-mediated SLB formation remains to be investigated. Herein, using the quartz crystal microbalance-dissipation and localized surface plasmon resonance techniques, we investigated the effect of bulk NaCl concentration on bicelle-mediated SLB formation on silicon dioxide surfaces. For comparison, similar experiments were conducted with vesicles as well. In both cases, SLB formation was observed to occur rapidly provided that the NaCl concentration was sufficiently high (>50 mM). Under such conditions, the effect of NaCl concentration on SLB formation was minor in the case of bicelles and significant in the case of vesicles where it is expected to be related primarily to osmotic pressure. At lower NaCl concentrations, bicelles also formed SLBs but slowly, whereas adsorbed vesicles remained intact. These findings were complemented by time-lapsed fluorescence microscopy imaging and fluorescence recovery after photobleaching measurements that corroborated bicelle-mediated SLB formation across the range of tested NaCl concentrations. The results are discussed by comparing the architectural properties of bicelles and vesicles along with theoretical analysis of the corresponding adsorption kinetics.