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Monolayers of poly(alpha,beta-aspartic acid) with long alkyl chains and miscibility with L-alpha-phosphatidylcholine at air-water interface
No full textSurface pressure/area isotherms of polypeptides modified with long alkyl chains and their miscibility with DPPC were investigated. The modified polypeptides formed stable monolayers due to their hairy-rod structure and limiting area increased as the degree of substitution increased. Collapse pressure of mixed monolayers deviated from ideal mixture and the free energies of mixing were negative values in all composition
Micellar aggregation and structure of dodecyl heptaethoxylates (C12E7) with different oxyethylene distributions in aqueous media
No full textThe micellar aggregation and structure, including aggregation number, hydrophobicity, micelle size, and micelle shape, were studied for four dodecyl heptaethoxylates with different oxyethylene distributions (Pure-7, NRE-7, BRE-7, and xBRE-7) using fluorescence, NMR, dynamic light scattering (DLS), and small angle neutron scattering (SANS). The aggregation number, measured from a steady state fluorescence quenching method, increased with the polydispersity of oxyethylene chain and with concentration. It was shown from the line half-width of proton NMR signals that the intermediate layer becomes wider as the polydispersity of the chain is increased. Changes in the hydrodynamic radius and radius of gyration show that micelles take different shapes with changing oxyethylene distributions and there is a transition, probably from rodlike to spherical, at a specific concentration. At very low concentrations, the fitted core and shell radii of monodisperse C12E7 from SANS experiment's showed a marked change with concentration. The aggregation number estimated from a polydisperse core-shell sphere model showed fairly good agreement with that from steady state fluorescence quenching. However, the fitted results for broad ethoxylates using sphere, prolate, and oblate models were physically meaningless. Two possible explanations are suggested: first, a rough surface of micelles, and-second, polydispersity of micelles in shape and size
The effect of different oil types on the dispersion stability and transdermal administration of lipid emulsion prepared by Microfluidizer
No full textStructural transition of self-aggreagates from poly(2-hydroxyethyl aspartamide) grafted with lactic acid oligomers in aqueous solution
No full textThe effect of different oil types on the dispersion stability and transdermal administration of lipid emulsion prepared by Microfluidizer
No full textOligoarginine peptide conjugated poly(amino acid) derivatives as a novel intracellular delivery carrier
No full textPolymer micelle-like aggregates of novel amphiphilic biodegradable poly(asparagine) grafted with poly(caprolactone)
No full textNovel amphiphilic graft copolymers composed of poly(asparagine) (PAsn) as the hydrophilic backbone and poly(caprolactone) (PCL) as the hydrophobic segment were successfully synthesized by grafting PCL-HMDs to poly(succinimde). After tosylating PCL-diol with p-toluenesulfonylchloride (TsCl), tosylated poly(caprolactone) (PCL-OTs) was then reacted with hexamethylenediamine (HMD). The reaction of the amine terminated PCL with poly(succinimide) (PSI) and the following aminolysis resulted in poly(aspargine)-graft-poly(caprolactone) (PAsn-g-PCL). The degree of substitution (DS) and grafting reaction was confirmed by C-13 NMR, FT-IR spectroscopy and elemental analysis. X-ray diffraction and DSC thermogram showed that the crystalline domain originated from PCL became apparent with an increase of DS. The amphiphilic comb-type graft polymer formed self-aggregates in aqueous solution when precipitated and dialysed against distilled water. Strong hydrophobic interaction of associated PCL grafts facilitated primary aggregate formation with DS, significantly reducing critical aggregation concentration and secondary aggregates also appeared in DLS measurements. Self-aggregates showed a bimodal size distribution originated from the self-aggregation and kinetically controlled particle aggregation, although the smaller primary aggregates was predominant. Spherical and dispersed aggregates of about 20 nm in diameter were observed by a transmission electron microscope. (C) 2002 Elsevier Science Ltd. All rights reserved
Self-aggregates of hydrophobically modified poly(2-hydroxyethyl aspartamide) in aqueous solution
No full textDehydrocholic acid (DHA) grafted poly(2-hydroxyethyl aspartamide) (PHEA)s were successfully synthesized and their self-aggregates in aqueous solution were characterized by fluorescence spectra and light scattering. PHEA was obtained by a simple reaction of ethanolamine with synthesized poly(succinimide) (PSI), and then PHEA-g-DHA was synthesized through an ester linkage between DHA and PHEA. The degree of substitution (DS) of DHA groups, defined by grafted mole%, was determined from both H-1-NMR and elemental analysis. The grafting reaction of DHA was retarded up to almost 10 mole% feed ratio of DHA/PHEA, but increased linearly above the threshold ratio. Nano-size self-aggregates in aqueous solution were examined with four DSs less than 10. As DS increased, the critical aggregation concentrations (CAC) of polymers were continuously reduced and the size of primary aggregates reduced to as small as 40 nm in diameter. When stored, the sonicated aggregates of high DS were destabilized, apparently forming large aggregates with small curvatures. The formation of irreversible interfused secondary structures would be induced by the curvature change or aggregation of primary particles. A simple calculation indicates that a small change of separation between grafted DHA groups may induce the large curvature shift, in fact, sphere-to-planar surface transition
Oligoarginine peptide conjugated poly(amino acid) derivatives as a novel intracellular delivery carrier
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