Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications

https://imechanica.org/files/Qiu_environmental_sensitive_hydrogel.pdf

Environment-sensitive hydrogels for drug delivery

Colloidal particles act in many ways like surfactant molecules, particularly if adsorbed to a fluid–fluid interface. Just as the water or oil-liking tendency of a surfactant is quantified in terms of the hydrophile–lipophile balance (HLB) number, so can that of a spherical particle be described in terms of its wettability via contact angle. Important differences exist, however, between the two types of surface-active material, due in part to the fact that particles are strongly held at interfaces. This review attempts to correlate the behaviour observed in systems containing either particles or surfactant molecules in the areas of adsorption to interfaces, partitioning between phases and solid-stabilised emulsions and foams.

Particles as surfactants—similarities and differences

RGD modified polymers: biomaterials for stimulated cell adhesion and beyond

Temperature-sensitive aqueous microgels.

Precipitation polymerization of N-isopropylacrylamide (NIPAM) with methylenebisacrylamide (MBAAm) in water at 70°C gave thermosensitive hydrogel microspheres. The adsorbability of proteins on the poly-NIPAM microspheres was found to depend on temperature. Below the lower critical solution temperature (LCST) of poly-NIPAM in an aqueous medium, that is, around 32°C, the microspheres hold a large amount of water inside and their surface is hydrophilic enough to suppress the adsorption of proteins. On the contrary, above 32°C, the micropheres deswell and their surface becomes hydrophobic and, consequently, susceptible to adsorption of a large amount of proteins. Proteins once adsorbed on the microspheres at a high temperature could be desorbed more or less by lowering the temperature to below 32°C. The extent of desorption at low temperatures was found to depend on the incubation time for adsorption at high temperatures.

Hydrogel microspheres III. Temperature-dependent adsorption of proteins on poly-N-isopropylacrylamide hydrogel microspheres

Ozone-induced graft polymerization was carried out to improve polymer surfaces. The polymers were exposed to ozone and the surface density of peroxides formed was determined by three methods; iodide, DPPH, and peroxidase method. The peroxide production could be readily controlled by the ozone concentration and the ozone exposure time. In addition, it was dependent on the kind of polymer. Further, it seemed probable that the ozone oxidation introduced peroxides not only on the outermost surface but also into a layer deeper from the outermost surface. Such polymeric peroxides were capable of initiating graft polymerization onto PU. All the physical and biological measurements on the grafted surface indicated that ozone-induced graft polymerization has effectively made the PU surface covered with the grafted water-soluble chains, their location being restricted to the film surface region. The interaction of the PU surface with blood components could be greatly reduced by the surface graft polymerization. © 1993 John Wiley & Sons, Inc.

Ozone‐induced graft polymerization onto polymer surface

The electrophoretic mobility and the size of two types of model latex particles with a core-shell structure were measured and compared with those for latex particles with no shell structure. These latex particles have a negatively charged core, covered with negatively charged or uncharged temperature-sensitive poly ( N -isopropylacrylamide) hydrogel layers. The charge density and the "softness" of the latex surface layer were obtained from the electrophoretic mobility data of the latex particles, showing a sudden change around the phase transition temperature (33°C) of poly( N -isopropylacrylamide). Also, these changes are correlated with a change in the size of the latex particles around 33°C. The temperature dependence of the hydrogel layer thickness on the particle accounts for the above observations. The negatively charged poly( N -isopropylacrylamide) surface gel layer shrinks as temperature increases, leading to an accumulation of the poly( N -isopropylacrylamide) segments on the particle core. This makes the particle harder. The uncharged poly( N -isopropylacrylamide) surface gel layer, on the other hand, does not change its thickness appreciably, but a change in configuration of the polymer segments occurs as the temperature increases, so that the surface layer becomes softer, probably because void spaces are created in the surface layer by the accumulation of polymer segments.

Surface Structure of Latex Particles Covered with Temperature-Sensitive Hydrogel Layers

Many synthetic microspheres are spherical and symmetrical because of the thermodynamical limitations of the reaction systems. We developed modification techniques to prepare spherical microspheres with intrinsic unsymmetry, for example, a microsphere with both an anionic and a cationic part. The modification was performed at the liquid−solid interface. Reactive microspheres with p-nitrophenyl moieties were settled onto the IgG-preadsorbed substrate, and the reaction between the activated ester moieties and IgG molecules proceeded only at the interface upon attachment. After the reaction, the modified microspheres were detached from the substrate with ultrasonication. In another modification at the air−water interface, the dispersion of reactive microspheres in ethanol was first spread on a water surface to produce the monolayer of microspheres, and then hydrolysis at the water side of the monolayer was performed by adding a NaOH aqueous solution to the subphase. After this unsymmetrical hydrolysis, we car...

Keiji Fujimoto

Papers

Hydrogel microspheres III. Temperature-dependent adsorption of proteins on poly-N-isopropylacrylamide hydrogel microspheres

Ozone‐induced graft polymerization onto polymer surface

Surface Structure of Latex Particles Covered with Temperature-Sensitive Hydrogel Layers

Preparation of unsymmetrical microspheres at the interfaces

Electrophoretic Mobility of Latex Particles Covered with Temperature-Sensitive Hydrogel Layers