Anionic surfactant with hydrophobic and hydrophilic chains for nanoparticle dispersion and shape memory polymer nanocomposites.

An anionic surfactant comprising a hydrophilic poly(ethylene glycol) (PEG) chain, hydrophobic alkyl chain, and polymerizable vinyl group was synthesized as a capping agent of nanoparticles. TiO(2) nanoparticles modified by this surfactant were completely dispersible in various organic solvents with a wide range of polarities, such as nitriles, alcohols, ketones, and acetates. Furthermore, these particles were found to be dispersible in various polymers with different properties, such as thermosetting epoxy resins and radical polymerized poly(methylmethacrylate) (PMMA). A polymer composite of surface-modified TiO(2) nanoparticles in epoxy resins prepared by using the developed surfactant also possessed temperature-induced shape memory properties.

[Characterization of Surface Interaction between Chitosan-modified Liposomes and Mucin Layer by Using CNT Probe AFM Method].

　In order to characterize the adhesion and deformation behavior between chitosan-modified liposomes and the mucin layer of the small intestine, mucin was coated on hydrophobic surface-modified carbon nanotube (CNT) probe of an atomic force microscope. The interaction between this mucin layer and the liposomes with or without chitosan modification in phosphoric acid buffer solution was determined by atomic force microscopy. The pH of the buffer solution was controlled at 2.8 and 7.0. The chitosan modification increased the attractive force between the liposomes and mucin layer during the separation process under both pH conditions. This result corresponded with that from a previous study about the liposome adhesion behavior on the surface of the small intestine of rats. By using the mucin-coated CNT probe, the long range and different types of attractive forces between the chitosan-modified liposomes and mucin layer was observed. Furthermore, the small-scaled deformation behavior change on the liposomal surfaces due to chitosan modification was also observed by the CNT probe. The detail deformation and adhesion behavior of the liposomes with or without chitosan modification was detected.

Microstructure control of iron hydroxide nanoparticles using surfactants with different molecular structures.

To control the morphology and crystal phase of iron oxide nanoparticles within several 10 nm in diameter, a microbial-derived surfactant (MDS) with a high carboxyl-group density and relatively low molecular weight (about 650 g/mol) or an artificially synthesized polyacrylic acid sodium salt (PAA) was added into the raw material aqueous solution before iron oxide particle synthesis by the gel-sol method. While pseudo-cubic hematite particles with a diameter of 500 nm were prepared without surfactant addition, spherical iron hydroxide nanoparticles with a diameter of 20 nm were prepared by MDS addition. In contrast, needle-type iron hydroxide nanoparticles with a length of 100 nm along the long axis were prepared by PAA addition. Complex formation due to the interaction between COO- groups in each surfactant and Fe3+ ions, as well as the template role prior to the synthesis of iron oxide in raw aqueous solution, inhibited the phase transition from iron hydroxide to hematite. Furthermore, the morphology of the iron hydroxide nanoparticles depended on the molecular structure of the surfactants.

Direct measurement of interactions between stimulation-responsive drug delivery vehicles and artificial mucin layers by colloid probe atomic force microscopy.

A novel thermo- and pH-sensitive nanogel particle, which is a core-shell structured particle with a poly(N-isopropylacrylamide) (p(NIPAAm)) hydrogel core and a poly(ethylene glycol) monomethacrylate grafted poly(methacrylic acid) (p(MMA-g-EG)) shell, is of interest as a vehicle for the controlled release of peptide drugs. The interactions between such nanogel particles and artificial mucin layers during both approach and separation were successfully measured by using colloid probe atomic force microscopy (AFM) under various compression forces, scan velocities, and pH values. While the magnitudes of the compression forces and scan velocities did not affect the interactions during the approach process, the adhesive force during the separation process increased with these parameters. The pH values significantly influenced the interactions between the nanogel particles and a mucin layer. A large steric repulsive force and a long-range adhesive force were measured at neutral pH due to the swollen p(MMA-g-EG) shell. On the other hand, at low pH values, the steric repulsive force disappeared and a short-range adhesive force was detected, which resulted from the collapse of the shell layer. The nanogel particles possessed a pH response that was sufficient to protect the incorporated peptide drug under the harsh acidic conditions in the stomach and to effectively adhere to the mucin layer of the small intestine, where the pH is neutral. The relationships among the nanogel particle-mucin layer interactions, pH conditions, scan velocities, and compression forces were systemically investigated and discussed.