A novel type of highly effective nonionic gemini alkyl O-glucoside surfactants: a versatile strategy of design

Chemical synthesis of amphiphilic glycoconjugates: Access to amino, fluorinated and sulfhydryl oleyl glucosides

Amphiphilic glycoconjugates offer an important prospect for development as chemical biology tools and biosurfactants. The chemical synthesis of such materials is required to expedite such prospect, compounded by the example of oleyl glycosides. Herein, we report a mild and reliable glycosylation method to access oleyl glucosides, glycosidating oleyl alcohol with α-trichloroacetimidate donors. We demonstrate capability for this methodology, extending it to synthesise the first examples of pyranose-component fluorination and sulfhydryl modifications within glucosides and glucosamines of oleyl alcohol. These compounds provide an exciting series of tools to explore processes and materials that utilise oleyl glycosides, including as probes for glycosphingolipid metabolism.

Oligomeric cationic Gemini surfactants: synthesis, surface activities and rheological properties as thickener

In this study, three oligomeric cationic Gemini surfactants (Ⅲ1, Ⅲ2, and Ⅲ3) were prepared from different major raw materials, including long-chain alkyl amine (dodecyl amine, tetradecyl amine or cetyl amine), formic acid, formaldehyde, diethyl amine hydrochloride and epichlorohydrin. The synthesis conditions for one of the three surfactants, bis-[2-hydroxy-3-(N,N-dimethyl-N-dodecyl)propyl]dipropylammonium chloride (Ⅲ1), were optimised by orthogonal experiments. The optimum synthesis conditions were: molar ratio of intermediate Ⅱ to intermediate Ⅰ1 = 1.0:2.2, reaction temperature = 85 °C and reaction time = 16 h. The structures of the three prepared compounds were characterised by FTIR and 1H NMR. Their thermal properties were evaluated by thermal gravimetric analysis (TGA). The Geminisurfactants prepared exhibited better surface active properties than conventional single chain cationic surfactants. With increasing carbon chain length from C12 to C16, both CMC and surface tension γ CMC decreased, while the viscosity of the thickening solution prepared with the synthesised oligomeric cationic Gemini surfactants as the main component increased. The optimum thickening formula was: 2.0 wt% Ⅲ3 + 0.8 wt% sodium salicylate (NaSal) + 0.6 wt% KCl. The viscosity of the optimum thickening formulation was 190.4 mPa s. Gemini oligomeric cationic surfactants could be used as thickeners in the production of fracturing fluids, flooding agents and drilling fluids for oil and gas production in oil fields.

Study of interactions of the cationic 12–2–12 Gemini surfactant with saccharides in aqueous solution: volumetric, compressibility and viscometric analysis

In the present study, the interaction behaviour of 12–2–12 Gemini surfactant in aqueous saccharide solutions (lactose and maltodextrin solutions) is investigated using density, sound velocity and viscosity measurements. The density and sound velocity data were used to determine the volume and compressibility parameters. The effects of temperature and concentration/strength of the solutions on the interaction behaviour were analysed by conductivity studies over a wide temperature (293.15–313.15) K and concentration range of the saccharides as well as of the surfactant. It was found that predominantly hydrophobic interactions together with ionic/hydrophilic interactions between 12–2–12 Gemini surfactant and the saccharides maltodextrin and lactose play a role. In addition, the structural changes in the 12–2–12 Gemini solutions induced by lactose and maltodextrin were investigated by viscosity measurements. The results confirm the observations from the volume and compressibility studies. The study of the different hydrophobic/hydrophilic interactions in the Gemini surfactant-sacharide-water mixtures are very helpful to understand the structural behaviour of Gemini surfactants in the view of their biological significance.

Interaction of calf thymus DNA and glucose-based gemini cationic surfactants with different spacer length: A spectroscopy and DLS study

The interactions between calf thymus DNA and a series of glucose-based cationic gemini surfactants 1a-1c with different spacer length, n = 4, 6 and 8, were studied by UV absorption, fluorescence spectroscopy, circular dichroism, FT-IR, dynamic light scattering and zeta potential measurements. The results showed that all the surfactants could interact with DNA efficiently. On addition of increasing concentration of the surfactants, UV absorption hypochromicity with insignificant blue shift were observed, until the DNA signal disappeared. The surfactant 1c was more efficient in the reduction of absorption intensity of DNA. According to the fluorescence quenching experiments by ethidium bromide exclusion, 1c exhibited the highest binding properties, with the binding constant at 3.25 × 10⁸ L·mol^-1. The spectroscopy study indicated that the surfactants bound with the DNA by a non-intercalative mode, mainly electrostatic interaction between the positively charged headgroups of the surfactants and negatively charged phosphate groups of DNA at low concentration, and the hydrophobic interaction among the alkyl chains at high concentration. The conformation of DNA during the interaction process could be kept B-form of DNA. For 1c, the DNA molecules can be compacted to about 103 nm in hydrodynamic diameter at 0.2 mM, while the minimum sizes of DNA were 140 nm and 133 nm, respectively, in the presence of 1a and 1b. The impact of the cationic gemini surfactants on the DNA compaction and condensation would shed light on their potential applications in gene delivery.

Fabrication of hydrolase responsive diglycerol based Gemini amphiphiles for dermal drug delivery applications

Since biocatalysts manoeuvre most of the physiological activities in living organisms and exhibit extreme selectivity and specificity, their use to trigger physicochemical change in polymeric architectures has been successfully used for targeted drug delivery. Our major interest is to develop lipase responsive nanoscale delivery systems from bio-compatible and biodegradable building blocks. Herein, we report the synthesis of four novel non-ionic Gemini amphiphiles using a chemo-enzymatic approach. A symmetrical diglycerol has been used as a core that is functionalised with alkyl chains for the creation of a hydrophobic cavity, and for aqueous solubility (polyethylene glycol) monomethyl ether (mPEG) is incorporated. Such systems can exhibit a varied self-assembly behaviour leading to the observance of different morphological structures. The aggregation behaviour of the synthesised nanocarrier was studied by dynamic light scattering (DLS) and critical aggregation concentration (CAC) measurements. The nanotransport potential of amphiphiles was investigated for hydrophobic guest molecules, i.e. Nile red, nimodipine and curcumin. Cytotoxicity of the amphiphiles was studied using HeLa and MCF7 cell lines at different concentrations, i.e. 0.05, 0.1, and 0.5 mg mL⁻¹. All nanocarriers were found to be non-cytotoxic up to a concentration of 0.1 mg mL⁻¹. Confocal laser scanning microscopy (cLSM) study suggested the uptake of encapsulated dye in the cytosol of the cancer cells within 4 h, thus implying that amphiphilic systems can efficiently transport hydrophobic drug molecules into cells. The biomedical application of the synthesised Gemini amphiphiles was also investigated for dermal drug delivery. In addition, the enzyme-mediated release study was performed that demonstrated 90% of the dye is released within three days. All these results supported the capability of nanocarriers in drug delivery systems.

Lipase responsive diglycerol based Gemini amphiphiles have been synthesized via a chemo-enzymatic approach and their application in dermal drug delivery has been explored.

Engineering Thermotoga maritima β-glucosidase for improved alkyl glycosides synthesis by site-directed mutagenesis

Alkyl glycosides are well-characterized nonionic surfactants, and can be prepared by transglycosylation reactions with retaining GH1 glycosidases being normally used for this purpose. The produced alkyl glycosides can also be hydrolyzed by the glycosidase, and hence, the yields of alkyl glycosides can be too low for industrial use. To improve the transglycosylation-to-hydrolysis ratio for a β-glucosidase from Thermotoga maritima (TmBglA) for the synthesis of alkyl glycoside, six mutants (N222F, N223C, N223Q, G224A, Y295F, and F414S) were produced. N222F, N223C, N223Q, G224A improved catalytic activity, F295Y and F414S are hydrolytically crippled with p-nitrophenol-β-d-glucopyranoside (pNPG) as substrate with an 85 and 70-fold decrease in apparent k_cat, respectively; N222F shows the highest k_cat/k_m value for pNPG. The substrate selectivity altered from pNPG to pNP-β-d-fucoside for N222F, F295Y, and F414S and from cellubiose to gentiobiose for N222F and F414S. Using pNPG (34 mM) and hexanol 80% (vol/vol), N222F, Y295F, and F414S synthesized hexyl-β-glycoside (HG) yields of 84.7%, 50.9%, and 54.1%, respectively, HG increased from 14.49 (TmBglA) to 22.8 mM (N222F) at 2 hr by 57.42%. However, this higher transglycosylation effect depended on that three mutants creates an environment more suited for hexanol in the active site pocket, and consequently suppressed its HG hydrolysis.

Newer Non-ionic A2 B2 -Type Enzyme-Responsive Amphiphiles for Drug Delivery

A new series of nonionic gemini amphiphiles have been synthesized in a multi-step chemoenzymatic approach by using a novel A₂ B₂ -type central core consisting of conjugating glycerol and propargyl bromide on 5-hydroxy isophthalic acid. A pair of hydrophilic monomethoxy poly(ethylene glycol) (mPEG) and hydrophobic linear alkyl chains (C₁₂ /C₁₅ ) were then added to the core to obtain amphiphilic architectures. The aggregation tendency in aqueous media was studied by dynamic light scattering, fluorescence spectroscopy and cryogenic transmission electron microscopy. The nanotransport potential of the amphiphiles was studied for model hydrophobic guests, that is, the dye Nile Red and the drug Nimodipine by using UV/Vis and fluorescence spectroscopy. Evaluation of the viability of amphiphile-treated A549 cells showed them to be well tolerated up to the concentrations studied. Being ester based, these amphiphiles exhibit stimuli-responsive sensitivity towards esterases, and a rupture of amphiphilic architecture was observed in the presence of immobilized Candida antarctica lipase (Novozym 435), thus facilitating release of the encapsulated guest from the aggregate.

Self-Assembly of Amphiphilic Compounds as a Versatile Tool for Construction of Nanoscale Drug Carriers

This review focuses on synthetic and natural amphiphilic systems prepared from straight-chain and macrocyclic compounds capable of self-assembly with the formation of nanoscale aggregates of different morphology and their application as drug carriers. Since numerous biological species (lipid membrane, bacterial cell wall, mucous membrane, corneal epithelium, biopolymers, e.g., proteins, nucleic acids) bear negatively charged fragments, much attention is paid to cationic carriers providing high affinity for encapsulated drugs to targeted cells. First part of the review is devoted to self-assembling and functional properties of surfactant systems, with special attention focusing on cationic amphiphiles, including those bearing natural or cleavable fragments. Further, lipid formulations, especially liposomes, are discussed in terms of their fabrication and application for intracellular drug delivery. This section highlights several features of these carriers, including noncovalent modification of lipid formulations by cationic surfactants, pH-responsive properties, endosomal escape, etc. Third part of the review deals with nanocarriers based on macrocyclic compounds, with such important characteristics as mucoadhesive properties emphasized. In this section, different combinations of cyclodextrin platform conjugated with polymers is considered as drug delivery systems with synergetic effect that improves solubility, targeting and biocompatibility of formulations.

Development of a Gemini Interfacial Antioxidant for Oil in Water Emulsion with Gallic Acid and Dodecyl Gemini Chains

In this study, development of the gemini gallate (GG) interfacial antioxidant for oil in water (O/W) emulsion was performed employing Steglich esterification with gallic acid and dodecyl gemini chains through a prepacked column and peristaltic pump-based purification system. The structural identity and purity of the prepared GG and monogallate (MG) were confirmed by NMR, Fourier transform infrared spectroscopy, and high-performance liquid chromatography-mass spectrometry. Further evaluation revealed that the GG possessed excellent radical scavenging activity and superior antioxidant activity in an O/W emulsion relative to the MG, especially under the condition of a reduced amount of the emulsifier. Microscopic investigation by a fluorescent probe and transmission electron microscopy (TEM) unveiled that the extraordinary antioxidant performance in the O/W emulsion was presumably attributed to preferable interfacial location because of the unique gemini molecular architecture. The superior antioxidant activity of the gemini antioxidant holds great promise for antioxidation in O/W emulsions.

Interactions with ctDNA of novel sugar-based gemini cationic surfactants

The interactions between calf thymus DNA, ctDNA, and a series of sugar-based gemini cationic surfactants with different hydrophobic chains were investigated. The surface properties of the cationic gemini surfactants were firstly examined, and then their interactions with DNA and induced condensation of DNA were studied by UV-vis, ethidium bromide exclusion assay, circular dichroism, dynamic light scattering, zeta potential and atomic force microscopy. With the increase of hydrophobic chains of the surfactants, critical micelle concentrations decreased significantly, and the interactions with DNA were remarkably strengthened, with the binding constant up to 1.95 × 10⁷ L·mol^-1 according to fluorescence quenching experiments by ethidium bromide exclusion. The gemini surfactant with hexadecyl hydrocarbon chain, 1c, exhibited the highest compaction capacity for DNA, accompanied with conformation changes, as confirmed by CD and DLS measurements. The DNA molecules could be compacted to about 140 nm in hydrodynamic diameter at 0.2 mM of 1c, and the overall shifts of the positive band and significant increase of negative molar ellipticity indicated the formation of a supramolecualr chiral order of ѱ phase in which DNA were supposed to be tightly packed.

Interaction between Gemini Dodecyl O-Glucosides-Based Multilayer Vesicles and β-Lactoglobulin: The Dominant Role of Surface Charge

Novel Gemini dodecyl O-glucoside-based primary, secondary, and tertiary vesicles were developed in this work utilizing layer-by-layer deposition of polysaccharides (e.g., sodium carboxymethyl cellulose and chitosan), and their interaction with β-lactoglobulin (BLG) was carefully investigated. The increase of polysaccharide layers on primary vesicles led to a monotonic increase in size and consecutive reversal of surface charge. Polysaccharide deposition significantly retarded the vesicle aggregation and degradation of entrapped catechin laurate during storage. Steady-state fluorescence, isothermal titration calorimetry, and protein precipitation analyses revealed the surface charge dependence of the interactions between vesicles and a model milk protein BLG, which were much stronger when they were charged oppositely than when they presented the same type of surface charge. It was highlighted that the surface charge of vesicles could be tuned by differently charged coatings to accommodate to that of the milk proteins in the food matrix. This work will contribute to the practical application of niosomal vesicles loaded with bioactive compounds to fortify dairy products.

Advances in the synthesis, molecular architectures and potential applications of gemini surfactants

Gemini surfactants have been the subject of intensive scrutiny by virtue of their unique combination of physical and chemical properties and being used in ordinary household objects to multifarious industrial processes. In this review, we summarize the recent developments of gemini surfactants, highlighting the classification of gemini surfactants based on the variation in headgroup polarity, flexibility/rigidity of spacer, hydrophobic alkyl chain and counterion along with potential applications of gemini surfactants, depicting the truly remarkable journey of gemini surfactants that has just come of age. We have focused on those objectives which will act as suitable candidates to take the field forward. The preceding information will permit us to estimate the effect of structural variation on the aggregation behavior of gemini surfactants for nanoscience and biological applications like antimicrobial, anti-fungal agent, better gene and drug delivery agent with low cytotoxicity and biodegradability, which makes them more advantageous for a number of technological processes and hence reduces the impact of these gemini surfactants on the environment.

Self-assembly of triangular amphiphiles into diverse nano/microstructures and release behavior of the hollow sphere

Amphiphilic triangular derivatives containing imine bond have been designed and used as building blocks for the construction of soft colloidal materials. The acylhydrazone derivative was found to form various nano/microstructures in different solvents. The microspheres, flower-like, and hollow spheres were formed in the polar solvents, while organogels with microporous structures were formed in nonpolar solvents. However, the simple Schiff base amphiphile without amide group did not form any ordered structures in the tested solvents. Therefore, besides the π-π stacking between the aromatic core and the van der Waals interactions between the alkyl chains, the hydrogen bonding between the acylhydrazone moieties played an important role in promoting the formation of various organized structures. More interestingly, the hollow sphere structure which was formed in THF could be used to encapsulate and release the rhodamine B. It was found that rhodamine B was encapsulated within their interiors under neutral conditions and released in an acidic condition due to the breakage of the imine bond.

Effect of amide bonds on the self-assembly of gemini surfactants

The effect of amide bonds on micellar aggregation of gemini surfactants was studied by small angle neutron scattering and conductivity methods. The micellar aggregation properties were found to depend strongly on the number and position of amide bonds in the molecules.