Surface morphology and biological activity of protein thin films produced by electrospray deposition

Protein thin films were prepared by the electrospray deposition (ESD) method from aqueous solutions of alpha-lactalbumin (alpha-LA) at different concentrations, and their surface morphologies and biological activities were characterized. The surface morphologies of the deposited films were observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM and AFM images showed that the film surfaces had a fine porous structure, in which the pore diameters ranged from 40 to 600 nm. The biological activities of the cross-linked protein films were tested by the mechanochemical method. The response to calcium ion (Ca(2+)) demonstrated that the biological activity of the films was preserved. These results indicate that the ESD method is potentially useful for the fabrication of active protein thin films. The freestanding protein thin films prepared by ESD and postdeposition cross-linking provide novel options for protein-based biomaterials.     

Organometallic Compounds XIV. Formation of novel [4]ferrocenophanes by the acid-catalyzed reaction of 1,1′-bis (α-hydroxy-α-phenylethyl) ferrocene

The acid-catalyzed reaction of 1,1′-bis(α-hydroxy-α-phenylethyl)ferrocene gave several [4] ferrocenophanes including a peroxide derivative. Their structures have been confirmed by spectrometric methods and from a study of their reaction behavior.     

de Haas-van Alphen effect in ZrZn2 under pressure: crossover between two magnetic states

We report measurements of the de Haas-van Alphen effect in ZrZn2 under hydrostatic pressures up to 21 kbar where the Curie temperature vanishes. The exchange splitting of a Fermi surface changes in behavior with increasing magnetic field, which is qualitatively consistent with the behavior of the high-field magnetization, suggesting the existence of a crossover between two distinct magnetic states. These and previously unexplained findings may be understood in terms of a p-T-B phase diagram qualitatively similar to that of the ferromagnetic superconductor UGe2.     

Thermosensitive copolymers having soluble and insoluble monomer units,poly(N‐vinylacetamide‐co‐methyl acrylate)s: Effect of additives on their lower critical solution temperatures

New thermosensitive polymers were synthesized by copolymerization between N‐vinylacetamide (NVA) and methyl acrylate whose homopolymers are soluble and insoluble in water, respectively. The lower critical solution temperature (LCST) of the obtained copolymers ranged between 59 and 83 °C, and the LCST increased with an increasing NVA content in the copolymers. The effectiveness of various salts addition on lowering the LCST of the copolymer solutions followed Hoffmeister series. NaCl and Na₂SO₄ addition linearly lowered the LCST with an increasing salts concentration, and slopes of the lines were almost constant regardless of the copolymer composition. The effectiveness of alcohols with various alkyl chain lengths on lowering the LCST did not follow the viscosity B coefficient values of the alcohols, which was probably the result of preferential adsorption of the alcohols to the copolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2651–2658, 2004     

Determination of dexamethasone in human plasma and urine by electron-impact mass spectrometry

A gas chromatographic-electron-impact mass spectrometric method for the determination of dexamethasone in biological fluids has been developed. Quantitation by isotopedilution mass spectrometry was carried out by selected-ion monitoring on the molecular ions of the tetra(trimethylsilyl) derivative of dexamethasone and of dexamethasone M+9 (m/z 680 and 689, respectively). The sensitivity, specificity, precision and accuracy of the method were demonstrated to be satisfactory for application to pharmacokinetic and bioavailability studies of dexamethasone after administration of a therapeutic dose.     

Enhancing the effect of the nanofiber network structure on thermoresponsive wettability switching

This letter reports the enhancing effects of a nanofiber network structure on stimuli-responsive wettability switching. Thermoresponsive coatings composed of nanofibers were prepared by electrospinning from thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAAm). The nanofiber coatings showed a large amplitude of thermoresponsive change in the wettability from hydrophilic to hydrophobic states compared to a smooth cast film. In particular, the combination of the surface chemistry and unique topology of the electrospun nanofiber coatings enables a transition from the Wenzel state to the metastable Cassie-Baxter state with an increase in temperature and consequently an enhanced amplitude of change in the water contact angles: the apparent contact angle differences between 25 and 50 °C are Δθ*(25-50?°C?)= 108 and 10° for the nanofiber coatings with a diameter of 830 nm and a smooth cast film, respectively. The fabrication of the 3D nanofiber network structure by electrospinning from stimuli-responsive materials is a promising option for highly responsive surfaces in wettability.     

Development of electrospun poly(vinyl alcohol) fibers immobilizing lipase highly activated by alkyl-silicate for flow-through reactors

Electrospun fibrous membranes composed of poly(vinyl alcohol) (PVA) fibers of approximately 1 μm in diameter, and immobilizing highly activated lipase entrapped in silicate cages with smaller dimensions than the fibers, were developed; and their feasibility as a component of flow-through reactors was studied. The electrospun PVA fibers were prepared from a mixture of PVA solution and a sol obtained from silicon alkoxide(s)—either tetramethoxysilane (TMOS) or dimethyldimethoxysilane (DMDMOS), or both, containing lipase. The fastest initial transesterification rate converting (s)-glycidol to glycidyl n-butyrate with vinyl n-butyrate in batchwise reactions was accomplished by treatment of lipase using the sol obtained from DMDMOS and TMOS together. The values were 4.5-, 21.8-, and 1.8-fold faster than those of systems using lipases that were either non-modified or modified using TMOS alone or DMDMOS alone, respectively. The higher activity of the lipase modified using both DMDMOS and TMOS and immobilized in PVA fibers resulted in a flow-through reactor having a higher degree of conversion at the same retention time compared with that using immobilized non-modified lipase. These results show the feasibility of flow-through reactors composed of electrospun PVA fibers immobilizing lipase highly activated by alkyl-silicate.     

Soluble-insoluble-soluble transitions of aqueous poly(N-vinylacetamide-co-acrylic acid) solutions

Several poly(N-vinylacetamide-co-acrylic acid)s with various copolymer compositions have been synthesized, and their unique phase-transition behavior in aqueous salt (Na2SO4 or NaCl) solutions was investigated. Copolymers containing more than 51 mol % N-vinylacetamide (NVA) show reentrant soluble-insoluble-soluble transitions with increasing temperature. The soluble-insoluble transition temperature (T(p1)) increased linearly with increasing NVA content, whereas the insoluble-soluble transition temperature (T(p2)) was almost constant irrespective of the NVA content. Potentiometric titration of the copolymer solutions suggested that the acrylic acid (AA) carboxyl groups form hydrogen bonds with the NVA amide groups even under soluble conditions. Dehydration of the NVA amides and their consequent hydrogen bonding with the AA carboxyl groups during the soluble-insoluble transition process was indicated by FTIR measurements. Addition of salt (Na2SO4 or NaCl) to the aqueous media reduces the solvent quality and enhances the intra- and interchain interactions of the copolymers. Thus, T(p1) was observed to decrease and T(p2) was observed to increase with increasing salt concentration. However, the addition of urea to the media reverses the concentration dependence of T(p1) and T(p2) by disturbing the intra- and interchain interactions of the copolymers.     

Macromol. Biosci. 3/2009

The effect of Ph‐OH group content on gelation time, mechanical properties, hydrophobicity, and cellular adhesiveness of hydrogels produced from carboxymethylcellulose derivatives is investigated. A higher Ph‐OH group content induces faster gelation and yields more brittle and hydrophobic gels. After 4 h of seeding, a larger number of L929 fibroblasts adhere to the hydrogel of the CMC‐Ph that contains 15.4 Ph‐OH groups per 100 repeat units of uronic acid (97% adhesion rate) than to the gel of CMC‐Ph with only 8.4 Ph‐OH groups (62% adhesion rate). The results demonstrate that controlling the Ph‐OH group content is an effective and useful way to control cellular adhesion and proliferation on the hydrogels, as well as gelation time and mechanical properties of the gels.