Self-assembling properties of glycolipid biosurfactants and their potential applications

Biosurfactants (BS) produced by a variety of microorganisms show unique properties (e.g. mild production conditions, multi-functionality, higher environmental compatibility) compared to their chemical counterparts. The numerous advantages of BS have prompted applications not only in the food, cosmetic, and pharmaceutical industries but in environmental protection and energy-saving technology as well. Among BS, “Glycolipid type” BS are the most promising, due to high productivity from renewable resources and versatile interfacial and biochemical properties. Mannosylerythritol lipids (MELs), which are glycolipid BS produced by yeast strains of the genus Pseudozyma, not only exhibit excellent surface activities but also self-assemble to form different lyotropic liquid crystalline phases such as sponge (L₃), bicontinuous cubic (V₂) or lammellar (L_α). They also show induction of cell-differentiation against human leukemia cells, and high binding affinity towards lectins and immunoglobulins. Recently, the cationic liposome bearing MELs has been demonstrated to increase dramatically the efficiency of gene transfection into mammalian cells. These features of BS should broaden the applications in new advanced technologies. The current status of R&D on glycolipid BS, especially their functions and potential applications, is discussed.     

Kinetic studies on the interactions between glycolipid biosurfactant assembled monolayers and various classes of immunoglobulins using surface plasmon resonance

Kinetic studies on the interactions between self-assembled monolayers of mannosylerythritol lipids (MELs), which are glycolipid biosurfactants abundantly produced by microorganisms, and various classes of immunoglobulins including human IgG, IgA, and IgM were performed using surface plasmon resonance (SPR). The effect of the MEL structure on the binding behavior of HIgG was examined. Assembled monolayers of MEL-A having two acetyl groups on the headgroup gave a high affinity (K_d = 1.7 × 10⁻⁶ M) toward HIgG, while those of MEL-B or MEL-C having only one acetyl group at C-6′ or C-4′ position gave little affinity. Our kinetic analysis revealed that the binding manner of HIgG, HIgA (K_d = 2.4 × 10⁻⁷ M), and HIgM (K_d = 2.2 × 10⁻⁷ M) to the assembled monolayers of MEL-A is not the monovalent mode but the bivalent mode, and both the first and second rate association constants (k_a1, k_a2) increase with an increase in the number of antibody binding sites, while those for dissociation (k_d1, k_d2) changed little. Moreover, we succeeded in directly observing great amounts of HIgG, HIgA, and HIgM bound to MEL-A monolayers using atomic force microscopy (AFM). Finally, we found that MEL-A assembled monolayer binds toward various IgG derived from mouse, pig, rabbit, horse, goat, rat, and bovine as well as human IgG (HIgG), and the only exception was sheep IgG. These results clearly demonstrate that MEL-A assembled monolayers would be useful as noble affinity ligand system for various immunoglobulins.     

New Positive‐Type Photoresists Based on Enzymatically Synthesized Polyphenols

Summary: New positive‐type photoresist systems based on enzymatically synthesized polyphenols have been developed. The photoresist thin film consisting of the polyphenol and a diazonaphthoquinone derivative was prepared on copperfoil‐coated epoxy resins and exposed to UV light with different doses. The polyphenols from the bisphenol monomers exhibited high photosensitivity, comparable with a conventional cresol novolac. The sensitivity could be controlled by changing the structure of the polyphenols. Furthermore, the present photoresist showed excellent etching resistance.

Characteristic exposure curves of poly( 1 )/DNQ and poly( 5 )/DNQ (both 70:30 wt.‐%) with different phenylene unit contents.     

Determination of a new orally active cephalosporin in human plasma and urine by high-performance liquid chromatography using automated column switching

Analytical procedures have been investigated for the separation, detection, identification and quantitation of some metabolites of N-benzyl-4-substituted anilines. Techniques based on gas-liquid chromatography were investigated and found to be unsatisfactory. By the use of reversed-phase high-performance liquid chromatography with gradient and ion-pairing techniques, methods were devised for the simultaneous analyses of a variety of metabolites. The method involves minimum sample work-up (acetonitrile precipitation) and allows easy and prompt analysis in biological media avoiding undue decomposition of unstable metabolites.     

High-performance liquid chromatographic determination of prifinium quaternary ammonium ion in human serum and urine

A simple, sensitive method for the determination of the prifinium ion, a quaternary ammonium ion, in human serum and urine is described. The method is based on extraction of the test solution with chloroform in the presence of saturated potassium bromide solution and normal-phase high-performance liquid chromatography using aqueous methanol as the mobile phase at pH 10. To prevent the dissolution of silica from the analytical column, the mobile phase is pre-saturated with silica by using a silica saturation column. Quantitation is possible down to 0.5 ng/ml of prifinium ion using 2 ml of serum and down to 5 ng/ml using a 1 ml of urine. The coefficients of variation of the method are less than 1.3% in both serum and urine. Serum levels and urinary excretion data obtained with this method are given for three healthy volunteers who had received a 60-mg oral dose of prifinium bromide.     

Synthesis of a New Class of High‐Molecular‐Weight Soluble Poly(amino acid)s by Oxidative Polymerization of Polyfunctional Macromolecules

Oxidative coupling of phenol‐containing macromolecules, polyglutamine and polyasparagine derivatives, has been examined to produce a new class of poly(amino acid)s. Under the conditions applied, the Fe‐salen‐catalyzed oxidative coupling of the polymers proceeded homogeneously, yielding exclusively soluble polymers of high molecular weight, avoiding the formation of insoluble gels.     

Chemical composition,and antibacterial and antioxidant activities of essential oils from Laggera tomentosa Sch. Bip. ex Oliv. et Hiern (Asteraceae)

Laggera tomentosa Sch. Bip. ex Oliv. et Hiern (Asteraceae), an endemic Ethiopian medicinal plant, is traditionally used to treat various ailments. Previously, the chemical constituents of the essential oil (EO) of its leaves and inflorescence were documented. However, no data about the chemical compositions of other parts of the EOs of the plant have been reported to date. Moreover, there are no previous biological activity reports on any parts of the EOs of this plant. Thus, in this study, the EOs were isolated from the stem bark and roots of this plant by hydrodistillation and analyzed using gas chromatography-mass spectrometry to identify their components. In addition, antibacterial potentials of the oils were evaluated using the disc diffusion and minimal inhibitory concentration (MIC) methods. 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide methods were also employed to assess their antioxidant properties. Oxygenated monoterpenes (71.82% and 77.51%), of which 2,5-dimethoxy- p -cymene (57.28% and 64.76%) and thymol methyl ether (9.51% and 8.93%) were identified as major components in the EOs of stem bark and roots of L. tomentosa and the oils, were the most potent in the DPPH (IC50, 0.33 ± 1.10 and 0.39 ± 0.97 mg/mL) assay, respectively. Moreover, the EOs demonstrated appreciable activity towards the gram+ ( S. aureus and B. cereus ) bacteria. Among these oils, the oil of the stem bark showed the greatest activity to the gram+ (MIC = 0.625 mg/mL) bacteria. Therefore, the overall results suggested that the EOs of L. tomentosa may be a promising prospect for pharmaceutical, food, and other industrial applications.     

Synthesis of Mannosylerythritol Lipid Analogues and their Self-Assembling Properties,Recovery Effects on Damaged Skin Cells,and Antibacterial Activity

Synthesis of three types of purpose-designed mannosylerythritol lipid (MEL)-D analogues with decanoyl groups, β-GlcEL-D, α-GlcEL-D, and α-MEL-D, was accomplished utilizing our boron-mediated aglycon delivery (BMAD) methods. Their self-assembling properties, recovery effects on damaged skin cells, and antibacterial activity were evaluated. It was revealed, for the first time, that α-GlcEL-D and α-MEL-D only generated giant vesicles, indicating that slight differences in the steric configuration of an erythritol moiety and fatty acyl chains affect the ability to form vesicles. Analogue α-MEL-D exhibited significant recovery effects on damaged skin cells. Furthermore, α-MEL-D exhibited antibacterial activity as high as that for MEL-D, indicating that α-MEL-D is a promising artificial sugar-based material candidate for enhancing the barrier function of the stratum corneum, superior to a known cosmetic ingredient, and possesses antibacterial activity.     

Phase behavior of ternary mannosylerythritol lipid/water/oil systems

Due to the great importance of new therapeutic routes for morphine in pain treatment, several investigations are under development. In this way, the design of a liquid system for the oral administration of morphine would be of great help, especially in patients with difficulties in swallowing (children and elderly people). The systems studied in this work are kollidon^® SR microparticles, a biodegradable polymer classically used as excipient in the design of solid dosage forms, as vehicles for morphine. A detailed investigation of the capabilities of the polymer particles to load this drug at their surface is described. Electrophoretic mobility and optical absorbance determinations were used with this aim. The main factors determining the drug incorporation, after incubation of the microparticles in the morphine solutions, were the adsorption time, the type of electrolyte and its concentration, and the drug concentration. The optimum loading conditions were used to perform morphine release evaluations, finding that the release profiles were biphasic since the drug adsorbed was slowly released during 24 h after an initial burst release phase.