Self-propelled object that generates a boundary with amphiphiles at an air/aqueous interface

A benzoic acid (BA) disk was investigated as a novel self-propelled object whose driving force was the difference in surface tension. 4-Stearoyl amidobenzoic acid (SABA) was synthesized as an amphiphile to control the nature of motion based on intermolecular interactions between BA and SABA. The BA disk exhibited characteristic motion depending on the surface density of the SABA on the aqueous phase, that is, reciprocating motion as a one-dimensional motion and restricted and unrestricted motion as a two-dimensional motion. The trajectory of the reciprocating motion was determined by the initial direction of motion, and the boundary between an aqueous surface and the BA-SABA condensed molecular layer was used as the field's boundary. The presented results indicate that the characteristic nature of motion can be designed at the molecular level based on the intermolecular interactions between an energy-source molecule and an amphiphile.

Synthesis and Characterization of Bola-Amphiphilic Porphyrin-Perylenebisimide Architectures

We report on the synthesis and characterization of a family of three water-soluble bola-amphiphilic zinc-porphyrin-perylenebisimide triads containing oligo carboxylic-acid capped Newkome dendrons in the periphery. Variations of the perylenebisimide (PBI) core geometry and dendron size (G1 and G2 dendrons with 3- and 9-carboxylic acid groups respectively) allow for tuning the supramolecular aggregation behavior with respect to variation of the molecular architecture. The triads show good solubility in basic aqueous media and aggregation to supramolecular assemblies. Theoretical investigations at the DFT level of theory accompanied by electrochemical measurements unravel the geometric and electronic structure of the amphiphiles. UV/Vis and fluorescence titrations with varying amounts of THF demonstrate disaggregation.

Development of cannabidiol derivatives as potent broad-spectrum antibacterial agents with membrane-disruptive mechanism

The emergence of antibiotic resistance has brought a significant burden to public health. Here, we designed and synthesized a series of cannabidiol derivatives by biomimicking the structure and function of cationic antibacterial peptides. This is the first report on the design of cannabidiol derivatives as broad-spectrum antibacterial agents. Through the structure-activity relationship (SAR) study, we found a lead compound 23 that killed both Gram-negative and Gram-positive bacteria via a membrane-targeting mechanism of action with low resistance frequencies. Compound 23 also exhibited very weak hemolytic activity, low toxicity toward mammalian cells, and rapid bactericidal properties. To further validate the membrane action mechanism of compound 23, we performed transcriptomic analysis using RNA-seq, which revealed that treatment with compound 23 altered many cell wall/membrane/envelope biogenesis-related genes in Gram-positive and Gram-negative bacteria. More importantly, compound 23 showed potent in vivo antibacterial efficacy in murine corneal infection models caused by Staphylococcus aureus or Pseudomonas aeruginosa. These findings would provide a new design idea for the discovery of novel broad-spectrum antibacterial agents to overcome the antibiotic resistance crisis.

Influence of docosahexaenoic acid on the interfacial behavior of cholesterol-containing lipid membranes: Interactions with small amphiphiles and hydration properties

Cholesterol is known to significantly modify both the structural and the dynamical properties of lipid membranes. On one side, the presence of free cholesterol molecules has been determined to stiffen the membrane bilayer by stretching the hydrophobic tails. Additionally, recent experimental and computational findings have made evident the fact that cholesterol also alters the dynamics and the hydration properties of the polar head groups of DPPC model lipid membranes. In turn, we have recently shown that the Omega-3 fatty acid docosahexaenoic acid, DHA, counteracts the effect of cholesterol on DPPC membrane's mechanical properties by fluidizing the bilayer. However, such behavior represents in fact a global outcome dominated by the larger lipid hydrophobic tails that neither discriminates between the different parts of the membrane nor elucidates the effect on membrane hydration and binding properties. Thus, we now perform molecular dynamics simulations to scrutinize the influence of DHA on the interfacial behavior of cholesterol-containing lipid membranes by characterizing their hydration properties and their binding to amphiphiles. We find that while cholesterol destabilizes interactions with amphiphiles and slightly weakens the lipid's hydration layer, the incorporation of DHA practically restores the interfacial behavior of pure DPPC.

Self-assembled Trehalose Amphiphiles as Molecular Gels: A Unique Formulation to Wax-free Cosmetics

Trehalose has been used as an emollient and antioxidant in cosmetics. However, we aimed to explore trehalose amphiphiles as oil structuring agents for the preparation of gel-based lip balms as part of wax-free cosmetics. This article describes the synthesis of trehalose fatty acyl amphiphiles and their corresponding oleogel-based lip balms. Trehalose dialkanoates were synthesized by esterifying the two primary hydroxyls of trehalose with fatty acids (C4-C12) using a facile, regioselective lipase catalysis. The gelation potential of as-synthesized amphiphiles was evaluated in organic solvents and vegetable oils. Stable oleogels were subjected to X-ray diffraction (XRD), thermal (DSC), and rheological studies and further used for the preparation of lip balms. Trehalose dioctanoate (Tr8), trehalose didecanoate (Tr10) were found to be super gelators as their minimum gelation concentration is ≤ 0.2 wt%. XRD studies revealed their hexagonal columnar molecular packing while forming the fibrillar networks. Rheometry proved that the fatty acyl chain length of amphiphiles can influence the strength and flow properties of oleogels. Further rheometry (at 25 °C, 37 °C, and 50 °C) and DSC studies have validated that Tr8- and Tr10-based oleogels are stable for commercial applications. Tr8- and Tr10-based olive oil oleogels were used for the preparation of lip balms. The preliminary results suggested that the cumulative effect of trehalose's emolliency and vegetable oil gelling nature can be achieved with trehalose amphiphiles, specifically, Tr8 and Tr10. This study has also demonstrated that Tr8- and Tr10-based lip balms can be used as an alternative to beeswax and plant wax lip balms, indicating their huge potential to succeed as a new paradigm to formulate wax-free cosmetics.

Interfaces with Fluorinated Amphiphiles: Superstructures and Microfluidics

This Minireview discusses recent developments in research on the interfacial phenomena of fluorinated amphiphiles, with a focus on applications that exploit the unique and manifold interfacial properties associated with these amphiphiles. Most notably, fluorinated amphiphiles form stable aggregates with often distinctly different morphologies compared to their nonfluorinated counterparts. Consequently, fluorinated surfactants have found wide use in high-performance applications such as microfluidic-assisted screening. Additionally, their fluorine-specific behaviour at solid/liquid interfaces, such as the formation of superhydrophobic coatings after deposition on surfaces, will be discussed. As fluorinated surfactants and perfluorinated materials in general pose potential environmental threats, recent developments in their remediation based on their adsorption onto fluorinated surfaces will be evaluated.

Atom Economical QPCs: Phenyl-Free Biscationic Quaternary Phosphonium Compounds as Potent Disinfectants

Quaternary ammonium compounds (QACs) are vital disinfectants for the neutralization of pathogenic bacteria in clinical, domestic, and commercial settings. After decades of dependence on QACs, the emergence of antimicrobial resistance to this class of compounds threatens the ability of existing QAC products to effectively manage rising bacterial threats. The need for new disinfectants is therefore urgent, with quaternary phosphonium compounds (QPCs) emerging as a new class of promising antimicrobials that boast significant activity against highly resistant bacteria. Reported here is a series of twenty-one novel QPCs that replace phenyl substituents on the phosphorus center with alkyl groups yet allow for rapid synthetic routes in high yields. Within this series are structures containing methyl, ethyl, or cyclohexyl phosphonium substituents on bisphosphane scaffolds bearing ethyl linkers, affording atom economical structures and ones that represent exact analogs to nitrogenous amphiphiles. The resultant bisQPC structures display high antibacterial efficacy enjoyed by comparably constructed QACs, with three structures in the single-digit micromolar activity range despite structural simplification.

Design, synthesis, and biological evaluation of tetrahydroquinoline amphiphiles as membrane-targeting antimicrobials against pathogenic bacteria and fungi

The rising prevalence of drug-resistant pathogens is one of the biggest threats to human health. The development of new antibiotics that can overcome drug resistance is in urgent need. Herein, we designed and synthesized a series of amphiphilic tetrahydroquinoline derivatives as small-molecule-based antimicrobial peptidomimetics. Two lead compounds 36 and 52 which contained the tetrahydroquinoline core, hydrophobic alkyl chains (n-nonyl or isoprenyl group), different spacer lengths (n = 4 or 8), and cationic guanidine moiety, showed poor hemolytic activity, low cytotoxicity, and potent broad-spectrum antimicrobial activity against Gram-positive and Gram-negative bacteria, as well as fungi. The further biological evaluation revealed that compounds 36 and 52 can kill bacteria and fungi rapidly via membrane-targeting action and avoid drug resistance development. More importantly, compounds 36 and 52 exhibited similarly potent in vivo antimicrobial activities in a murine corneal infection caused by Staphylococcus aureus ATCC29213 or Pseudomonas aeruginosa ATCC9027, as compared to vancomycin or gatifloxacin. These results suggest that compounds 36 and 52 have great potential as new broad-spectrum antimicrobial agents to combat microbial resistance.

Rigidity-Activity Relationships of bisQPC Scaffolds Against Pathogenic Bacteria

Biscationic quaternary phosphonium compounds (bisQPCs) represent a promising class of antimicrobials, displaying potent activity against both Gram-negative and Gram-positive bacteria. In this study, we explored the effects of structural rigidity on the antimicrobial activity of QPC structures bearing a two-carbon linker between phosphonium groups, testing against a panel of six bacteria, including multiple strains harboring known disinfectant resistance mechanisms. Using simple alkylation reactions, 21 novel compounds were prepared, although alkene isomerization as well as an alkyne reduction were observed during the respective syntheses. The resulting bisQPC compounds showed strong biological activity, but were hampered by diminished solubility of their iodide salts. One compound (P2P-10,10 I) showed single digit micromolar activity against the entire panel of bacteria. Overall, intriguing biological activity was observed, with more rigid structures displaying better efficacy against Gram-negative strains and less rigid structures demonstrating slightly increased efficacy against S. aureus strains.

Synthesis of Phospholipids Under Plausible Prebiotic Conditions and Analogies with Phospholipid Biochemistry for Origin of Life Studies

Phospholipids are essential components of biological membranes and are involved in cell signalization, in several enzymatic reactions, and in energy metabolism. In addition, phospholipids represent an evolutionary and non-negligible step in life emergence. Progress in the past decades has led to a deeper understanding of these unique hydrophobic molecules and their most pertinent functions in cell biology. Today, a growing interest in "prebiotic lipidomics" calls for a new assessment of these relevant biomolecules.

Methods for Small-Angle Scattering Measurements on Peptiplexes of DNA with Cell-Penetrating Peptides

Peptiplexes are soft biomaterials formed through the noncovalent association between cell-penetrating peptides and nucleic acids. Although internalization often involves electrostatic anchoring followed by endocytosis, the mode of action of these transporters remains elusive in many cases, and proper understanding of mechanisms behind their penetrating capabilities necessarily entails structural data at the nanoscopic scale. In this chapter, we examine the structural landscape of peptiplexes, emphasizing the complex behavior of these polyelectrolyte self-assemblies and how supramolecular order impacts their translocation efficiency. We discuss experimental tools commonly used to investigate the structure of peptiplexes and pay special attention to small-angle X-ray scattering (SAXS) as a suitable method for unveiling their nanoscale organization. A roadmap for standard SAXS measurements in CPP/DNA samples is presented alongside a selection of observations from our own experience dealing with SAXS applied to the investigation of CPPs.

Imide Condensation as a Strategy for the Synthesis of Core-Diversified G-Quadruplex Ligands with Anticancer and Antiparasitic Activity*

A facile imide coupling strategy for the one-step preparation of G-quadruplex ligands with varied core chemistries is described. The G-quadruplex stabilization of a library of nine compounds was examined using FRET melting experiments, and CD, UV-Vis, fluorescence and NMR titrations, identifying several compounds that were capable of stabilizing G-quadruplex DNA with interesting selectivity profiles. The best G4 ligand was identified as compound 3, which was based on a perylene scaffold and exhibited 40-fold selectivity for a telomeric G-quadruplex over duplex DNA. Surprisingly, a tetra-substituted flexible core, compound 11, also exhibited selective stabilization of G4 DNA over duplex DNA. The anticancer and antiparasitic activity of the library was also examined, with the lead compound 3 exhibiting nanomolar inhibition of Trypanosoma brucei with 78-fold selectivity over MRC5 cells. The cellular localization of this compound was also studied via fluorescence microscopy. We found that uptake was time dependant, with localization outside the nucleus and kinetoplast that could be due to strong fluorescence quenching in the presence of small amounts of DNA.

Oleate-modified hyaluronan: Controlling the number and distribution of side chains by varying the reaction conditions

In this work, low molecular weight hyaluronan was chemically modified by oleoyl moieties utilising mixed anhydrides methodology. The activation of oleic acid with benzoyl chloride in organic solvents miscible with water was followed by NMR spectroscopy. The product selectivity correlates with the solvent's Hildebrand solubility parameter. Furthermore, the effect of the solvent for the mixed anhydride formation was elucidated by density functional theory (DFT) and showed that the reactions are faster in acetonitrile or alcohols than in hexane. Furthermore, the solvent demonstrated to control the substituent distribution pattern along HA chain during esterification. An even distribution of substituents was observed in reactions performed in water mixed with ethers. The substituent distribution pattern clearly influenced the aggregation behaviour of amphiphilic HA, controlling the stability of the delivery system, while increasing the encapsulation capacity.

Amphiphiles capsaicin and triton X-100 regulate the chemotherapy drug colchicine's membrane adsorption and ion pore formation potency

Chemotherapy drugs (CDs), e.g. colchicine derivative thiocolchicoside (TCC) and taxol, have been found to physically bind with lipid bilayer membrane and induce ion pores. Amphiphiles capsaicin (Cpsn) and triton X-100 (TX100) are known to regulate lipid bilayer physical properties by altering bilayer elasticity and lipid monolayer curvature. Both CDs and amphiphiles are predicted to physically accommodate alongside lipids in membrane to exert their membrane effects. The effects of their binary accommodation in the lipid membrane are yet to be known. Firstly, we have performed experimental studies to inspect whether membrane adsorption of CDs (colchicine or TCC) gets regulated due to any membrane effects of Cpsn or TX100. We find that the aqueous phase presence of these amphiphiles, known to reduce the membrane stiffness, works towards enhancing the membrane adsorption of CDs. Our recently patented technology 'direct detection method' helps address the membrane adsorption mechanisms. Secondly, in electrophysiology records, we measured the amphiphile effects on the potency of ion channel induction due to CDs. We find that amphiphiles increase the CD induced channel induction potency. Specifically, the membrane conductance, apparently due to the ion channel induction by the TCC, increases substantially due to the Cpsn or TX100 induced alterations of the bilayer physical properties. Thus we may conclude that the binary presence of CDs and amphiphiles in lipid membrane may influence considerably in CD's membrane adsorption, as well as the membrane effects, such as ion pore formation.

Towards the Prediction of Antimicrobial Efficacy for Hydrogen Bonded, Self-Associating Amphiphiles

Herein we report 50 structurally related supramolecular self-associating amphiphilic (SSA) salts and related compounds. These SSAs are shown to act as antimicrobial agents, active against model Gram-positive (methicillin-resistant Staphylococcus aureus) and/or Gram-negative (Escherichia coli) bacteria of clinical interest. Through a combination of solution-state, gas-phase, solid-state and in silico measurements, we determine 14 different physicochemical parameters for each of these 50 structurally related compounds. These parameter sets are then used to identify molecular structure-physicochemical property-antimicrobial activity relationships for our model Gram-negative and Gram-positive bacteria, while simultaneously providing insight towards the elucidation of SSA mode of antimicrobial action.

Development of pyrene-based fluorescent ether lipid as inhibitor of SK3 ion channels

We report the synthesis of three bioactive pyrene-based fluorescent analogues of Ohmline which is the most efficient and selective inhibitor of SK3 ion channel. The interaction of these Ohmline-pyrene (OP1-3) with liposomes of different composition reveals that only OP2 and OP3 are readily integrated into liposomes. Fluorescence measurements indicate that, depending on their concentration, OP2 and OP3 exist either as monomer or as a mixture of monomer and excimers within the liposome bilayer. Among the three Ohmline Pyrene compounds (OP1-3) only OP2 is able to reduce SK3 currents and is the first efficient fluorescent modulator of SK3 channel as revealed by patch clamp measurements (- 71.3 ± 13.3% at 10 μM) and by its inhibition of SK3-dependent cancer cell migration at (-32.5% ± 4.8% at 1 μM). We also report the first fluorescence study on living breast cancer cells (MDA-MB-231) showing that OP2 is rapidly integrated in bio-membranes followed by cell internalization.

Inhibition of starch digestion: The role of hydrophobic domain of both α-amylase and substrates

The physicochemical mechanism of starch digestion is very complicated since it may be affected by the non-valence interactions of the amylase inhibitor with the substrate or the enzyme. The role of hydrophobic interaction in the process of starch digestion is not clear. In this study, pluronics (PLs) with different hydrophobicity were used as model amphiphilic compounds to study their inhibition on starch digestion using multi-spectroscopic methods. The results showed that the hydrophobic nature of PLs changed starch structure, but it had a greater effect on the structure of α-amylase by exposing more tryptophan residues and increasing α-helix and β-sheet contents. Further investigation by using different chain-length fatty acids confirmed the results. The finding in this study is informative to design and fabricate α-amylase inhibitors for controlling starch digestion at the molecular level.

Pendant-bearing glucose-neopentyl glycol (P-GNG) amphiphiles for membrane protein manipulation: Importance of detergent pendant chain for protein stabilization

Glucoside detergents are successfully used for membrane protein crystallization mainly because of their ability to form small protein-detergent complexes. In a previous study, we introduced glucose neopentyl glycol (GNG) amphiphiles with a branched diglucoside structure that has facilitated high resolution crystallographic structure determination of several membrane proteins. Like other glucoside detergents, however, these GNGs were less successful than DDM in stabilizing membrane proteins, limiting their wide use in protein structural study. As a strategy to improve GNG efficacy for protein stabilization, we introduced two different alkyl chains (i.e., main and pendant chains) into the GNG scaffold while maintaining the branched diglucoside head group. Of these pendant-bearing GNGs (P-GNGs), three detergents (GNG-2,14, GNG-3,13 and GNG-3,14) were not only notably better than both DDM (a gold standard detergent) and the previously described GNGs at stabilizing all six membrane proteins tested here, but were also as efficient as DDM at membrane protein extraction. The results suggest that the C14 main chain of the P-GNGs is highly compatible with the hydrophobic widths of membrane proteins, while the C2/C3 pendant chain is effective at strengthening detergent hydrophobic interactions. Based on the marked effect on protein stability and solubility, these glucoside detergents hold significant potential for membrane protein structural study. Furthermore, the independent roles of the detergent two alkyl chains first introduced in this study have shed light on new amphiphile design for membrane protein study. STATEMENT OF SIGNIFICANCE: Detergent efficacy for protein stabilization tends to be protein-specific, thus it is challenging to find a detergent that is effective at stabilizing multiple membrane proteins. By incorporating a pendant chain into our previous GNG scaffold, we prepared pendant chain-bearing GNGs (P-GNGs) and identified three P-GNGs that were highly effective at stabilizing all membrane proteins tested here including two GPCRs. In addition, the new detergents were as efficient as DDM at extracting membrane proteins, enabling use of these detergents over the multiple steps of protein isolation. The key difference between the P-GNGs and other glucoside detergents, the presence of a pendant chain, is likely to be responsible for their markedly enhanced protein stabilization behavior.

Non-ionic PEG-oligoglycerol dendron conjugated nano-carriers for dermal drug delivery

A new class of non-ionic amphiphiles have been synthesised using a combination of polyethylene glycol (PEG) and oligoglycerol dendrons as hydrophilic units and an alkoxy aryl moiety as hydrophobic unit. The resulting amphiphiles were found to aggregate in aqueous medium. Their aggregation behaviour was studied using dynamic light scattering (DLS), fluorescence spectroscopy, and cryogenic electron microscopy (cryo-TEM). The inner hydrophobic core of these aggregates in aqueous medium is capable of encapsulating lipophilic guest molecules. The encapsulation behaviour was studied using Nile red as a hydrophobic dye as well as Curcumin and Dexamethasone as hydrophobic drug candidates. Furthermore, for biological evaluation, cytotoxicity and cellular uptake was studied using different cancer cell lines. The biomedical application of synthesised amphiphiles was further investigated for dermal drug delivery on excised human skin using Nile red encapsulated in the nanocarrier. The release profile of drug/dye encapsulated amphiphiles was studied under physiochemical conditions in the presence of immobilized lipase Novozym 435.

Novel thymoquinone loaded chitosan-lecithin micelles for effective wound healing: Development, characterization, and preclinical evaluation

While the wound healing activity of thymoquinone (TQ) is well known, its clinical effectiveness remains limited due to the inherently low aqueous solubility, resulting in suboptimal TQ exposure in the wound sites. To address these problems, TQ loaded chitosan-lecithin micelles for wound healing were prepared and its efficacy was determined in vivo in the excision wound model. Firstly, the co-block polymer of chitosan and soya lecithin was synthesized which has low critical micelle concentration (CMC). Its employment in the development of TQ loaded polymeric micelles by Self-assembly method resulted in the stable polymeric micelle composition having requisite small particle size (<100 nm), narrow size distribution (close to zero) and high entrapment efficiency (98.77 %) of TQ. The designed nano-carriers not only substantially entrapped the drug but also controlled the release rate of TQ. The TQ-polymeric micelle hydrogel exhibited superior wound healing efficacy to the native TQ and Silver Sulphadiazine.

The rational design of cell-penetrating peptides for application in delivery systems

Cell penetrating peptides (CPPs) play a crucial role in the transportation of bioactive molecules. Although CPPs have been used widely in various delivery systems, further applications of CPPs are hampered by several drawbacks, such as high toxicity, low delivery efficiency, proteolytic instability and poor specificity. To design CPPs with great cell-penetrating ability, physicochemical properties and safety, researchers have tried to develop new methods to overcome the defects of CPPs. Briefly, (1) the side chain of arginine containing the guanidinium group is essential for the facilitation of cellular uptake; (2) the hydrophobic counterion complex around the guanidinium-rich backbone can "coat" the highly cationic structure with lipophilic moieties and act as an activator; (3) the conformation-constrained strategy was pursued to shield the peptide, thereby impeding access of the proteolytic enzyme; (4) targeting strategies can increase cell-type specificity of CPPs. In this review, the above four aspects were discussed in detail.

Molecular crowding effects on the distribution of amphiphiles in biological media

Biological systems are the result of the interactions established among their many distinct molecules and molecular assemblies. The high concentration of small molecules dissolved in the aqueous media alter the water properties with important consequences in the interactions established. In this work, the effects of high concentrations of the disaccharide trehalose on the solubility of a homologous series of fluorescent amphiphiles (NBD-Cn, n=4-16) and on their interaction with a lipid bilayer and a serum protein are quantitatively characterized. Both kinetic and equilibrium aspects are reported for a better understanding of the effects observed. The aqueous solubility of the most hydrophobic amphiphiles (n ≥ 8) is strongly increased by 1 M trehalose, while no signifcant effect is observed for the most polar amphiphile (n = 4). This results from a decrease in the magnitude of the hydrophobic effect at molecular crowding conditions. A small decrease is observed on the equilibrium association with serum albumin. This is most significant for amphiphiles with longer alkyl chains, in agreement with their increased solubility in the aqueous media containing trehalose. The effects on the association of the amphiphiles with lipid bilayers are influenced by both equilibrium and kinetic aspects. On the one hand, the decreased magnitude of the hydrophobic effect leads to a decrease in the affinity of the amphiphiles towards the membrane. However, this tendency may be overbalanced by the effects on the kinetics of the interaction (insertion/desorption) due to the increase in the viscosity of the aqueous media. It is shown that the distribution of amphiphilic drugs in the crowded biological media is significantly different from that predicted from studies in dilute solutions and that the effects are dependent on the solute's hydrophobicity.

An efficient and environmental-friendly dispersant based on the synergy of amphiphilic surfactants for oil spill remediation

Eliminating the adverse environmental impact of chemical dispersants for oil spill has been a significant challenge since decades ago. Here, we prepared an effective and environmentally-friend dispersant with stable emulsifying capacity by the soybean lecithin and Tween 80. The mean droplet diameters of emulsions prepared by decane decreased from 11.3 to 4.1 μm, the emulsification index of emulsion climbed from 0 to 22.0% by 0.5 wt% dispersant. This dispersant exhibits favorable emulsifying capacity when the temperature ranges from 10 to 40 °C, pH within 5-7, and the concentration of inorganic cation is 30000 mg/L. Fluorescence microscopy analysis, FTIR, and the interfacial tension meter were employed to investigate the interaction between the soybean lecithin and Tween 80, a clear redshift of the hydroxyl group on the lecithin/Tween 80 dispersant and the detected surfactants over the oil-water interface confirm that there exists a synergy between the lecithin and Tween 80 due to the electrostatic attractions, which tremendously contribute to the reduction in the interfacial tension between water and oil. To further understand the influence of the dispersant on the oil hydrocarbon concentration in the water column, visualization simulation with the varying depths were performed. The results showed that the oil hydrocarbon concentration in the water column bottom was proportional to the addition of the dispersant, which facilitates spilled oil dispersing into smaller droplets, accelerates the biodegradation process. Hence, the lecithin/Tween 80 dispersant can be perceived as a promising alternative for oil spill remediation.

Development of dilipid polymyxins: Investigation on the effect of hydrophobicity through its fatty acyl component

Continuous development of new antibacterial agents is necessary to counter the problem of antimicrobial resistance. Polymyxins are considered as drugs of last resort to combat multidrug-resistant Gram-negative pathogens. Structural optimization of polymyxins requires an in-depth understanding of its structure and how it relates to its antibacterial activity. Herein, the effect of hydrophobicity was explored by adding a secondary fatty acyl component of varying length onto the polymyxin structure at the amine side-chain of l-diaminobutyric acid at position 1, resulting to the development of dilipid polymyxins. The incorporation of an additional lipid was found to confer polymyxin activity against Gram-positive bacteria, to which polymyxins are inherently inactive against. The dilipid polymyxins showed selective antibacterial activity against Pseudomonas aeruginosa. Moreover, dilipid polymyxin 1 that consists of four carbon-long aliphatic lipids displayed the ability to enhance the antibacterial potency of other antibiotics in combination against P. aeruginosa, resembling the adjuvant activity of the well-known outer membrane permeabilizer polymyxin B nonapeptide (PMBN). Interestingly, our data revealed that dilipid polymyxin 1 and PMBN are substrates for the MexAB-OprM efflux system, and therefore are affected by efflux. In contrast, dilipid polymyxin analogs that consist of longer lipids and colistin were not affected by efflux, suggesting that the lipid component of polymyxin plays an important role in resisting active efflux. Our work described herein provides an understanding to the polymyxin structure that may be used to usher the development of enhanced polymyxin analogs.

Structural organization of lipid-functionalized-Au nanoparticles

Gold nanoparticles (AuNPs) are considered suitable systems for drug delivery and diagnostics with several applications in biomedicine. Size, shape and surface functionalization of these nanoparticles are important parameters influencing their behavior in a biological environment. This study describes the preparation and the characterization of lysophosphocholine coated AuNPs by means of Small Angle Neutron Scattering (SANS), Electron Paramagnetic Resonance (EPR) and Fluorescence Spectroscopy. In particular the structure of the functionalized AuNP suspension, as well as the physical properties, of the nanoparticle organic coating are discussed. The experimental results indicated that functionalized lysophosphocholine-AuNPs form aggregates, which are composed by nanoparticles with core-shell structure. Nevertheless, the nanoparticle suspension resulted to be stable, without significant structural rearrangements even when the temperature was increased to 50 °C. At the same time, experimental evidences also suggested that the 18LPC layer around AuNPs presented a reduced chain packing compared to pure 18LPC aggregates.

Bioinspired supramolecular engineering of self-assembling immunofibers for high affinity binding of immunoglobulin G

Many one-dimensional (1D) nanostructures are constructed by self-assembly of peptides or peptide conjugates containing a short β-sheet sequence as the core building motif essential for the intermolecular hydrogen bonding that promotes directional, anisotropic growth of the resultant assemblies. While this molecular engineering strategy has led to the successful production of a plethora of bioactive filamentous β-sheet assemblies for interfacing with biomolecules and cells, concerns associated with effective presentation of α-helical epitopes and their function preservation have yet to be resolved. In this context, we report on the direct conjugation of the protein A mimicking peptide Z33, a motif containing two α-helices, to linear hydrocarbons to create self-assembling immuno-amphiphiles (IAs). Our results suggest that the resulting amphiphilic peptides can, despite lacking the essential β-sheet segment, effectively associate under physiological conditions into supramolecular immunofibers (IFs) while preserving their native α-helical conformation. Isothermal titration calorimetry (ITC) measurements confirmed that these self-assembling immunofibers can bind to the human immunoglobulin G class 1 (IgG1) with high specificity at pH 7.4, but with significantly weakened binding at pH 2.8. We further demonstrated the accessibility of Z33 ligand in the immunofibers using transmission electron microscopy (TEM) and confocal imaging. We believe these results shed important light into the supramolecular engineering of α-helical peptides into filamentous assemblies that may possess an important potential for antibody isolation.

Divergent effects of anesthetics on lipid bilayer properties and sodium channel function

General anesthetics revolutionized medicine by allowing surgeons to perform more complex and much longer procedures. This widely used class of drugs is essential to patient care, yet their exact molecular mechanism(s) are incompletely understood. One early hypothesis over a century ago proposed that nonspecific interactions of anesthetics with the lipid bilayer lead to changes in neuronal function via effects on membrane properties. This model was supported by the Meyer-Overton correlation between anesthetic potency and lipid solubility and despite more recent evidence for specific protein targets, in particular ion-channels, lipid bilayer-mediated effects of anesthetics is still under debate. We therefore tested a wide range of chemically diverse general anesthetics on lipid bilayer properties using a sensitive and functional gramicidin-based assay. None of the tested anesthetics altered lipid bilayer properties at clinically relevant concentrations. Some anesthetics did affect the bilayer, though only at high supratherapeutic concentrations, which are unlikely relevant for clinical anesthesia. These results suggest that anesthetics directly interact with membrane proteins without altering lipid bilayer properties at clinically relevant concentrations. Voltage-gated Na⁺ channels are potential anesthetic targets and various isoforms are inhibited by a wide range of volatile anesthetics. They inhibit channel function by reducing peak Na⁺ current and shifting steady-state inactivation toward more hyperpolarized potentials. Recent advances in crystallography of prokaryotic Na⁺ channels, which are sensitive to volatile anesthetics, together with molecular dynamics simulations and electrophysiological studies will help identify potential anesthetic interaction sites within the channel protein itself.

Thiolated chitosan micelles: Highly mucoadhesive drug carriers

Current study was aimed to generate thiolated chitosan micelles based on amphiphilic chitosan-stearic acid conjugate (CSA) and to evaluate adhesive properties on mucosal membranes. Chitosan-stearic acid-thioglycolic acid (CSA-TGA) conjugate was synthesized via stearic acid linkage to chitosan and later, thioglycolic acid was covalently attached to CSA. CSA-TGA and CSA were characterized by degree of amine substitution, thiol group determination, ATR-FTIR and cytotoxicity analysis. Micelle size was 13.40±9.38 and 26.30±26.86nm and zeta potential -0.01 and 0.03mV for CSA and CSA-TGA, respectively. In porcine mucus CSA-TGA micelles exhibited 1.80-, 2.12- and 1.72-fold increase in dynamic viscosity, elastic modulus and viscous modulus, respectively. Compared to CSA micelles CSA-TGA micelles remained up to 56.1- fold and 28.6- fold higher degree attached on intestinal and vaginal mucosa, respectively. Taking possibility to incorporate both lipophilic and hydrophilic drugs into these micelles into account, thiol functionalized micelles could be promising carriers for mucosal drug delivery.

Hyaluronic acid and phospholipid interactions useful for repaired articular cartilage surfaces-a mini review toward tribological surgical adjuvants

This mini review is focused on the emerging nexus between the medical device and pharmaceutical industries toward the treatment of damaged articular cartilage. The physical rationale of hyaluronic acid and phospholipid preparations as tribological surgical adjuvants for repaired articular cartilage surfaces is explored, with directions for possible new research which have arisen due to the therapeutic advance of the physiochemical scalpel. Because synovial joint lubrication regimes become dysfunctional at articular cartilage lesion sites as a result of the regional absence of the surface active phospholipid layer and its inability to reform without surgical repair, hyaluronic acid and phospholipid intra-articular injections have yielded inconsistent efficacy outcomes and only short-term therapeutic benefits mostly due to non-tribological effects. Parameters for hydrophobic-polar type interactions as applied to the lubricating properties of normal and osteoarthritic synovial fluid useful for repaired articular cartilage surfaces are discussed.

Development of siloxane-based amphiphiles as cell stabilizers for porous shape memory polymer systems

HYPOTHESIS

Polyurethane foaming surfactants are cell stabilized at the polymer-gas interface during foam blowing to prevent bubble coalescence. Siloxane-based surfactants are typically used to generate a surface tension gradient at the interface. The chemical structure of the hydrophobic and hydrophilic units affects surfactant properties, which can further influence foam morphology.

EXPERIMENTS

Siloxane-polyethylene glycol (PEG) ether amphiphiles were synthesized in high yield via hydrosilylation to serve as surfactants for shape memory polymer (SMP) foams. Hydrophobic units consisted of trisiloxane and polydimethyl siloxane, and PEG allyl methyl ether (n=8 or 25) was the hydrophilic component. Upon confirming successful synthesis of the surfactants, their surface tension was measured to study their suitability for use in foaming. SMP foams were synthesized using the four surfactants, and the effects of surfactant structure and concentration on foam morphology were evaluated.

FINDINGS

Spectroscopic data confirmed successful siloxane-PEG coupling. All surfactants had a low surface tension of 20-21mN/m, indicating their ability to reduce interfacial tension. SMP foams were successfully fabricated with tunable cell size and morphology as a function of surfactant type and concentration.

Pod-Like Supramicelles with Multicompartment Hydrophobic Cores Prepared by Self-Assembly of Modified Chitosan

In this paper, pod-like supramicelles with multicompartment hydrophobic cores were prepared by self-assembly of amphiphilic N-phthaloylchitosan-g-poly(N-vinylcaprolactam) (PHCS-g-PNVCL) in aqueous medium. The employed biocompatible amphiphilic polymer was synthesized by grafting the carboxyl terminated poly(N-vinylcaprolactam) (PNVCL-COOH) chains onto N-phthaloylchitosan (PHCS) backbone. ¹H NMR and FTIR results confirmed the molecular structure of the copolymers. The morphology of the supramicelles assembled by PHCS-g-PNVCL was revealed by means of TEM and polarized light microscope. In solution, the supramicelles were very stable as monitored by DLS and zeta potential measurements. Temperature and pH presented significant influences on the size and size distribution of the supramicelles. These supramicelles with multicompartment hydrophobic cores should be ideal biomimetic systems with promising applications in drug delivery.

Sacrificial amphiphiles: Eco-friendly chemical herders as oil spill mitigation chemicals

Crude oil spills are a major threat to marine biota and the environment. When light crude oil spills on water, it forms a thin layer that is difficult to clean by any methods of oil spill response. Under these circumstances, a special type of amphiphile termed as "chemical herder" is sprayed onto the water surrounding the spilled oil. The amphiphile forms a monomolecular layer on the water surface, reducing the air-sea surface tension and causing the oil slick to retract into a thick mass that can be burnt in situ. The current best-known chemical herders are chemically stable and nonbiodegradable, and hence remain in the marine ecosystem for years. We architect an eco-friendly, sacrificial, and effective green herder derived from the plant-based small-molecule phytol, which is abundant in the marine environment, as an alternative to the current chemical herders. Phytol consists of a regularly branched chain of isoprene units that form the hydrophobe of the amphiphile; the chain is esterified to cationic groups to form the polar group. The ester linkage is proximal to an allyl bond in phytol, which facilitates the hydrolysis of the amphiphile after adsorption to the sea surface into the phytol hydrophobic tail, which along with the unhydrolyzed herder, remains on the surface to maintain herding action, and the cationic group, which dissolves into the water column. Eventual degradation of the phytol tail and dilution of the cation make these sacrificial amphiphiles eco-friendly. The herding behavior of phytol-based amphiphiles is evaluated as a function of time, temperature, and water salinity to examine their versatility under different conditions, ranging from ice-cold water to hot water. The green chemical herder retracted oil slicks by up to ~500, 700, and 2500% at 5°, 20°, and 35°C, respectively, during the first 10 min of the experiment, which is on a par with the current best chemical herders in practice.

In situ template synthesis of gold nanoparticles using a bis-imidazolium amphiphile-based hydrogel

HYPOTHESIS

Gemini-type bis-imidazolium amphiphiles are able to stabilize gold nanoparticles (GNPs) and also form hydrogels. It should be possible to obtain GNPs synthesized within these hydrogels and stabilized by the bis-imidazolium molecules.

EXPERIMENTS

Hydrogels containing a gold salt were formed using 1,3-bis[(3-octadecyl-1-imidazolio)methyl]benzene dibromide. After aging of the gel, upon addition of the reducing agent in a solvent the formation of GNPs was assessed. The gel was characterised and the GNPs were observed using High Resolution Transmission Electron Microscopy (HRTEM).

FINDINGS

Monodisperse GNPs with an average size of ca. 5 nm and well defined icosahedral geometry were formed in situ using the bis-imidazolium amphiphile-based hydrogel as template. Furthermore the gelator is also the stabilizing ligand of the GNPs, allowing the recovery of the GNP by disassembling the gel without aggregation of the inorganic colloid.

Synthesis, Structure-Activity Relationship, and Mechanistic Investigation of Lithocholic Acid Amphiphiles for Colon Cancer Therapy

We report a structure-activity relationship of lithocholic acid amphiphiles for their anticancer activities against colon cancer. We synthesized ten cationic amphiphiles differing in nature of cationic charged head groups using lithocholic acid. We observed that anticancer activities of these amphiphiles against colon cancer cell lines are contingent on nature of charged head group. Lithocholic acid based amphiphile possessing piperidine head group (LCA-PIP1 ) is ~10 times more cytotoxic as compared to its precursor. Biochemical studies revealed that enhanced activity of LCA-PIP1 as compared to lithocholic acid is due to greater activation of apoptosis.LCA-PIP1 induces sub G0 arrest and causes cleavage of caspases. A single dose of lithocholic acid-piperidine derivative is enough to reduce the tumor burden by 75% in tumor xenograft model.

Novel cationic polyene glycol phospholipids as DNA transfer reagents--lack of a structure-activity relationship due to uncontrolled self-assembling processes

Cationic glycol phospholipids were synthesized introducing chromophoric, rigid polyenoic C20:5 and C30:9 chains next to saturated flexible alkyl chains of variable lengths C6-20:0. Surface properties and liposome formation of the amphiphilic compounds were determined, the properties of liposome/DNA complexes (lipoplexes) were established using three formulations (no co-lipid, DOPE as a co-lipid, or cholesterol as a co-lipid), and the microstructure of the best transfecting compounds inspected using small angle X-ray diffraction to explore details of the partially ordered structures of the systems that constitute the series. Transfection and cytotoxicity of the lipoplexes were evaluated by DNA delivery to Chinese hamster ovary (CHO-K1) cells using the cationic glycerol phospholipid 1,2-dioleoyl-sn-glycero-3-ethylphosphocholine (EPC) as a reference compound. The uncontrollable self-association of the molecules in water resulted in aggregates and liposomes of quite different sizes without a structure-property relationship. Likewise, adding DNA to the liposomes gave rise to unpredictable sized lipoplexes, which, again, transfected without a structure-activity relationship. Nevertheless, one compound among the novel lipids (C30:9 chain paired with a C20:0 chain) exhibited comparable transfection efficiency and toxicity to the control cationic lipid EPC. Thus, the presence of a rigid polyene chain in this best performing achiral glycol lipid did not have an influence on transfection compared with the chiral glycerolipid reference ethyl phosphocholine EPC with two flexible saturated C14 chains.

Macrocyclic imidazolium-based amphiphiles for the synthesis of gold nanoparticles and delivery of anionic drugs

In the present work, we have explored the use of amphiphilic bis-imidazolium based macrocycles and an open chain analog for the successful synthesis of gold nanoparticles (AuNPs). The macrocyclic ligands incorporate hydrophobic chains of different lengths, and the newly synthesized ligands were further used for the synthesis of AuNPs in a biphasic system. The successfully synthesized AuNPs were thoroughly characterized. The sizes of the AuNPs were ca. 8 nm, using macrocyclic ligands bearing two 10 carbon atoms alkyl chains, ca. 5 nm in the case of macrocyclic ligands with two 18 carbon atoms alkyl chains, and ca. 7 nm for the open chain ligand with two 18 carbon atoms alkyl chains. Their possible application as vehicles to load and release anionic drugs (such as sodium ibuprofenate) was also assessed and compared with previously described open chain analogs. In this case, it was observed that the AuNPs had high efficiency in extracting sodium ibuprofenate from an aqueous solution. The application as a drug delivery vehicle was confirmed by in vitro release experiments at different pH values.

Detection of stealthy small amphiphilic biomarkers

Pathogen-specific biomarkers are secreted in the host during infection. Many important biomarkers are not proteins but rather small molecules that cannot be directly detected by conventional methods. However, these small molecule biomarkers, such as phenolic glycolipid-I (PGL-I) of Mycobacterium leprae and Mycobactin T (MbT) of Mycobacterium tuberculosis, are critical to the pathophysiology of infection, and may be important in the development of diagnostics, vaccines, and novel therapeutic strategies. Methods for the direct detection of these biomarkers may be of significance both for the diagnosis of infectious disease, and also for the laboratory study of such molecules. Herein, we present, for the first time, a transduction approach for the direct and rapid (30min) detection of small amphiphilic biomarkers in complex samples (e.g. serum) using a single affinity reagent. To our knowledge, this is the first demonstration of an assay for the direct detection of PGL-I, and the first single-reporter assay for the detection of MbT. The assay format exploits the amphiphilic chemistry of the small molecule biomarkers, and is universally applicable to all amphiphiles. The assay is only the first step towards developing a robust system for the detection of amphiphilic biomarkers that are critical to infectious disease pathophysiology.

Synthesis and evaluation of N-alkyl-9-aminoacridines with antibacterial activity

A series of 9-alkylaminoacridines were synthesized and evaluated for activity against two strains of methicillin-resistant and one strain of methicillin-sensitive Staphylococcus aureus. Results are presented that show a clear structure activity relationship between the N-alkyl chain length and antibacterial activity with peak MIC99 values of 2-3 μM for alkyl chains ranging from 10 to 14 carbons in length. Although prior work has linked the function of acridine-based compounds to intercalation and topoisomerase inhibition, the present results show that 9-alkylaminoacridines likely function as amphiphilic membrane-active disruptors potentially in a similar manner as quaternary ammonium antimicrobials.

A Lysoganglioside/Poly-L-glutamic Acid Conjugate as a Picomolar Inhibitor of Influenza Hemagglutinin

Based on the principle of a multivalent interaction, the amphiphilic polymer 1, present in solution as an aggregate (see below right), is able to inhibit infection with the influenza virus. After recognition of a specific sialyllactose epitope through hemaglutinin (HA) on the virus surface, the sphingosine residues and the fluorescent tag form a stable complex with HA through hydrophobic interactions. Polymer 1 shows in vitro inhibitory activity 10⁶ -fold greater than that of sialyllactose. PGA=polyglutamic acid.