Aqueous Gelatin Solution Research Articles

Nanotube Foam Prepared by Gelatin Gel as a Template

It has been known that simply mixing single-walled carbon nanotubes (SWCNTs) in an aqueous solution of gelatin disperses SWCNTs well for a period of months. Gels made from the gelatin-SWCNT mixture are also stable and have a clear, black color. Scanning electron microscopy shows that gelatin molecules self-organize into a foamlike structure. All SWCNTs are embedded in the gelatin film that makes up the foam walls. Those SWCNTs belonging to one face of the foam cell cannot approach other faces to make van der Waals contact. Thus, the foam structure is associated with stabilization of the SWCNT dispersion. The gelatin can be removed thermally while maintaining the foam structure to give a sponge made of nanotube foams. This highly porous solid is electrically conducting and mechanically stable and can be used as a structural frame for composite materials.

Preparation and characterization of magnesium doped hydroxyapatite–gelatin nanocomposite

Magnesium (Mg) doped hydroxyapatite (HAP)–gelatin (GEL) one-dimensional nanofibers were prepared in the aqueous GEL solution at low temperature (38 °C). The influence of GEL and Mg on morphology and crystal structure was systematically investigated. Different amount Mg doped HAP–GEL and HAP–GEL nanofibrils doped with different amounts of Mg were obtained by self-assembly along with gelatin, and pure HAP and HAP doped with Mg were sphere nanoparticles in the absence of GEL. Fourier transform infrared (FT-IR) analysis showed that chemical bonding between calcium ions of HAP and carboxyl groups of GEL molecules led to a red shift of the 1395 cm−1 band of GEL. The incorporation of Mg ions into the composite phase caused the decrease of the lattice parameters and Ca/P molar ratio in the HAP solid samples. Differential thermal analysis and thermogravimetric analysis (DTA/TG) features and FT-IR spectra of HAPGEL composite materials were very similar to those of dentine.

Evaluation of Fungal Pathogens as Biological Control Agents for Cogongrass (Imperata cylindrica)1

Based on field surveys and evaluations in the greenhouse, two fungal pathogens,Bipolaris sacchari and Drechslera gigantea, were identified as promising biological control agents for cogon- grass. In greenhouse trials, the application of spore suspensions of these fungi containing 10 5 spores/ ml in a 1% aqueous gelatin solution to cogongrass plants and their incubation in a dew chamber for 24 h resulted in disease symptoms that ranged from discrete lesions to complete blighting of leaves. Disease severity (DS), based on a rating scale for southern corn leaf blight with 50% as the maximum DS rating, ranged from 42 to 49%. In greenhouse experiments, the application of spores formulated in an oil emulsion composed of 4% horticultural oil, 10% light mineral oil, and 86% water resulted in higher levels of foliar blight with no dew exposure or shorter periods of dew exposure (4, 8, or 12 h) as compared with the application of spores formulated in 1% gelatin. Field trials demonstrated that under natural conditions, the application of a spore and an oil emulsion mixture containing 10 5 spores/ml of either fungus could cause foliar injury from disease and phytotoxic damage from the oil emulsion. Depending on the application rate (100 or 200 ml/plot), the level of foliar injury ranged from 40 to 86% (based on a field assessment scale of 0 to 100% foliar injury) with B. sacchari as the test fungus. However, with D. gigantea as the test fungus, foliar injury ranged from 9 to 70% depending on the application volume and the oil concentration used. Although B. sacchari and D. gigantea were capable of causing foliar blight on cogongrass, the regenerative ability of the rhizomes allowed cogongrass to recover from the damage caused by these fungi. However, the level of injury caused by these fungi is sufficient to support their use as components for integrated management of cogongrass. Nomenclature: Cogongrass, Imperata cylindrica (L.) Beauv. # 3 IMPCY; corn, Zea mays L. Additional index words: Bioherbicide, biological control, Bipolaris sacchari (E.J. Butler) Shoe- maker, Drechslera gigantea (Heald & F.A. Wolf) Ito. Abbreviations: CRD, completely randomized design; DAI, days after inoculation; DS, disease se- verity; RH, relative humidity; SOE, spore and oil emulsion mixture; WAI, weeks after inoculation; WM, weed mortality.

Evolution of water structure in biopolymer solutions during the gelation process

The evolution of water structure in train of gelation process is examined in aqueous solution of gelatin using Raman spectroscopy of the O–H stretching band. The measurements have been performed at room temperature for four concentrations of gelatin, which yields different dimensions of nanopores in the network of the created gel. We have found that during the sol–gel transition the number of molecules that participate in the regular tetrahedral H-bond structure increases, and the effect is stronger for higher concentration of the biopolymer.

Overshoot and oscillation in surface tension of gelatin solutions

The experimental data of the surface tension of aqueous gelatin solution reported by Sato and Ueberreiter [H. Sato, K. Ueberreiter, Macromol. Chem. 180 (1979) 829; H. Sato, K. Ueberreiter, Macromol. Chem. 180 (1979) 1107; H. Sato, K. Ueberreiter, ACS Polym. Preprints 20 (1979) 907] were analyzed with a theory of adsorption kinetics with time delay. It is found that the observed overshoot and oscillation of the surface tension are well explained by the present theory. The delay time and the rate constants of adsorption and desorption of gelatin molecules onto the air/gelatin solution interface have been evaluated.

Some factors influencing growth of nano-sized AgBr/I particles in aqueous gelatin solution

AgBr/I nanoparticles were prepared in a gelatin colloid medium using the double-jet precipitation method. The difference in growth behaviour of AgBr/I nanoparticles in two types of gelatin, fish gelatin and bovine gelatin, was observed, and was considered to result from differences in conformation and component contents. The average size of AgBr/I nanoparticles prepared in aqueous fish gelatin solution increased with decreasing addition rate of reactants from 4.0 mmol min-1 to 1.7 mmol min-1 or increasing precipitation temperature from 30°C to 60°C. On the basis of the dependence of the growth rate of AgBr/I nanoparticles on precipitation temperature, the activation energy of the growth rate of the nanoparticles was estimated as 20.4 kJ mol-1. The protective role of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene (TAI) for AgBr/I nanoparticles made in aqueous fish gelatin solution was explored. The results showed that TAI was adsorbed on the surface of AgBr/I nanoparticles to restrict growth and to deflocculate particles.

Purification of Single Wall Carbon Nanotubes Using Gelatin

We have developed a simple procedure for the purification of single wall carbon nanotubes (SWNTs) with gelatin as the dispersing reagent. The steps of this procedure were performed in the following order: annealing in air, sonication in an aqueous solution of gelatin, and soaking in hydrochloric acid solution. The advantage of using gelatin as a dispersing reagent is not only that it is useful for untangling the SWNT bundles, but also that the gelatin molecule and the metallic catalyst can be removed using HCl.

Application of Oestrogen Receptor Ligand Binding Domain to the Generic Isolation of Oestrogens by Receptor Affinity Chromatography

Human oestrogen receptor (alpha) ligand binding domain (hER-LBD) was expressed in E. coli and isolated using a novel approach. The solubilised recombinant receptor had the expected biological activity in terms of ligand binding affinity and selectivity, indicating the potential for use in the proposed receptor affinity chromatography (RAC) application. Subsequent covalent binding of hER-LBD to agarose support provided an affinity matrix capable of selective binding of oestrogenic ligands, with a capacity for 17β-oestradiol of ∼6 ng/mL wet gel. In initial studies, a yield of ∼75% of bound ligand from the affinity matrix was obtained by elution with aqueous ethanol. Immobilised hER-LBD eluted with ethanol retained the majority of its capability to bind 17β-oestradiol (E2), indicating the possibility of reuse of the receptor matrix. In ligand-receptor displacement studies, using [3H]E2-saturated immobilised hER-LBD, direct extraction of the xenoestrogen 2′,3′,4′,5′-tetrachloro-4-biphenylol (TeCBol) from a model food (aqueous gelatin solution) was inhibited at the highest concentration of gelatin tested (1%), however, prior precipitation and extraction with ethanol enabled dose dependent binding of TeCBol. The present studies thus provide preliminary proof of principle for the application of hER-LBD for the purpose of RAC and for the generic extraction of oestrogens and xenoestrogens from biological matrices.

A theory of adsorption kinetics with time delay and its application to overshoot and oscillation in the surface tension of gelatin solution

A theory of adsorption kinetics with time delay [Ohshima et al. (1992) Colloid Polym. Sci. 270:707] is developed and applied to the surface tension of a polymer solution. It is found that the general appearance of the overshoot and oscillation in the time course of the surface tension of aqueous gelatin solution observed by Sato and Ueberreiter [(1979) Makromol. Chem. 180:829, 1107; (1979) Polym. Prepr. Am. Chem. Soc. Div. Polym. Chem. 20:907) can be explained by the present theory.

Interaction between a Partially Fluorinated Alkyl Sulfate and Gelatin in Aqueous Solution

The interaction of a partially fluorinated alkyl sulfate, sodium 1H,1H,2H,2H-perfluorooctyl sulfate (C6F13CH2CH2OSO3Na), with the polyampholyte gelatin has been examined in aqueous solution using surface tension and small-angle neutron scattering (SANS). The 19F chemical shift of each fluorine environment in the surfactant is unaltered by the addition of gelatin, indicating that there is no contact between the gelatin and the fluorocarbon core of the micelle. The chemical shift of the two methylene groups closest to the headgroup is altered when gelatin is present, disclosing the location of the polymer. The critical micelle concentration (cmc) of the surfactant, cmc = 17+/-1 mM, corresponds to an effective alkyl chain (CnH2n+1) length of n = 11. In the presence of gelatin, the cmc is substantially reduced as expected, cmc(1) = 4+/-1 mM, which is also consistent with an effective alkyl chain length of n = 11. In the presence of the fluorosurfactant, the monotonic decay of the SANS from the gelatin-only system is replaced by a substantial peak at an intermediate Q value mirroring the micellar interaction. At low ionic strengths, the gelatin/micelle complex can be described by an ellipsoid. At higher ionic strengths, the electrostatic interaction between the micelles is screened and the peak in the gelatin scattering disappears. The correlation length describing the network structure decreases with increasing SDS concentration as the bound micelles promote a collapse of the network.

Solvation Dynamics of DCM in a Polypeptide−Surfactant Aggregate: Gelatin−Sodium Dodecyl Sulfate

Solvation dynamics of 4-(dicyanomethylidene)-2-[p-(dimethylamino)styryl]-6-methyl-4H-pyran (DCM) is studied in a polypeptide-surfactant aggregate consisting of gelatin and sodium dodecyl sulfate (SDS) in potassium dihydrogen phosphate (KP) buffer. The average solvation time (tauS) in gelatin-SDS aggregate at 45 degrees C is found to be 1780 ps, which is about 13 times slower than that in 15 mM SDS in KP buffer at the same temperature. The fluorescence anisotropy decay in gelatin-SDS aggregate is also different from that in SDS micelles in KP buffer. DCM displays negligible emission in the presence of gelatin in aqueous solution. Thus the solvation dynamics in the presence of gelatin and SDS is exclusively due to the probe (DCM) molecules at the gelatin-micelle interface. The slow solvation dynamics is ascribed to the restrictions imposed on the water molecules trapped between the polypeptide chain and micellar aggregates. The critical association concentration (cac) of SDS for gelatin is determined to be 0.5 +/- 0.1 mM.

Behavior of hepatocytes inoculated in gelatin-immobilized polyurethane foam

We have fabricated gelatin-immobilized polyurethane foams (PUFG) by dipping polyurethane foam (PUF) in an aqueous solution containing gelatin and by subsequent reaction with glutaraldehyde after freeze-drying. Gelatin aqueous solutions of different concentrations were used as the dipping solutions to control the amount of immobilized gelatin. The average pore size of PUF decreased with an increase in gelatin concentration. It was found from the hepatocyte adhesion experiment that the amount of hepatocytes seeded on PUFG1, prepared by using a 1% aqueous gelatin solution, was higher than that on other PUFGs. The hepatocytes inoculated in PUFG1 were slightly aggregated as the incubation time increased. The cells inoculated in PUFG1 showed higher ammonia removal ability than those monolayer-cultured on a gelatin-immobilized polystyrene dish (PSG) after 1 and 4 days of incubation time. The inoculated cells exhibited higher albumin secretion relative to monolayer-cultured hepatocytes on PSG. Albumin secretion by hepatocytes seeded on PUFG1 was increased by the presence of serum and was further increased by both the presence of serum and cytokines. The results obtained from a 3-(3,4-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay indicated that PUFG can provide a better microenvironment for hepatocyte culture along with nutrition and metabolite transfer through the high porosity of PUF.

Kinetics of Triple Helix Formation in Semidilute Gelatin Solutions

Using optical rotation to study the triple helix reversion of gelatin in aqueous solutions demonstrates that the reversion is a combination of first-order and second-order kinetic processes. On the basis of this observation, we propose a new two-step mechanism of triple helix formation in polypeptides, that leads to an expression distinct from the one obtained by Flory and Weaver. The rate-limiting step is formation of a two-stranded nucleus, which can be intramolecular (first order) or intermolecular (second order). The triple helix is formed by subsequent wrapping of a third strand onto this nucleus. We estimate the minimum stable helix length and the size of the loop at the end of an intramolecular helix from our kinetics analysis. The new two-step mechanism of triple helix formation is consistent with all existing literature data and allows prediction of concentration and temperature dependencies of helix formation rate.

Effect of added gelatin on the properties of calcium phosphate cement

This study investigates the effect of gelatin on the setting time, compressive strength, phase evolution and microstructure of calcium phosphate cement. The composite cement powder (about 18 wt% gelatin, and 82 wt% α-tricalcium phosphate) was prepared from the solid compound obtained by casting a gelatin aqueous solution containing α-tricalcium phosphate. 5 wt% of CaHPO 4·2H 2O were added to the powder before mixing with the liquid phase. Two cement formulations were prepared using two different liquid/powder ratios, and their properties compared with those of control samples, prepared without gelatin. The final setting time increases from 10 min to more than 45 min when the L/ P ratio increases from 0.3 to 0.4 ml/g. The presence of gelatin accelerates the setting reaction, and improves the mechanical properties of the cements. The compressive strength increases with the setting reaction up to 10.7–14.0 MPa for the gelatin cements, whereas the control samples exhibit much lower values. The improved mechanical properties of the composite cements with respect to the controls can be related to their reduced total porosity and more compact microstructure.

Rheological Properties of the Interfacial Layers of Hydrophobized Gelatins

Rheological properties of the interfacial layers of gelatins chemically modified with N-hydroxysuccinimide ester of caprylic acid (the degree of modification is 10, 30, and 85%) are studied. Interfacial layers are spontaneously formed at the aqueous gelatin solution–toluene interface. Rheological characteristics (yield strength, modulus of elastic deformation, Schwedoff and Bingham viscosities) increase in proportion to the degree of modification (hydrophobization) of gelatin.

Systematic of alcohol-induced simple coacervation in aqueous gelatin solutions.

Turbidity measurements performed at 450 nm were used to follow the process of simple coacervation when 1% (w/v) aqueous alkali processed gelatin (type-B) solutions were titrated with methanol, ethanol, propanol, and tert-butyl alcohol at various pHs of the solution ranging from pH = 5 to 8 and ionic strengths varying from I = 0.01 to 0.1 M NaCl. The titration profiles clearly established the transition points in terms of the percentage of volume of alcohol added relative to that of solvent corresponding to the first occurrence of turbidity (Vt) and a point of turbidity maximum (Vp). Addition of more alcohol drove the system toward precipitation. The values of Vt and Vp characterized the initiation of intramolecular folding and intermolecular aggregate formation of the charge neutralized gelatin molecules and the subsequent micro coacervate droplet formation. The state of intermolecular aggregates and that of folded gelatin molecules could be characterized by dynamic laser light scattering experiments, which implied spontaneous segregation of particle sizes preceding coacervation. The aggregates constitute the coacervate phase while the folded gelatin molecules mostly stay dispersed in the supernatant. The data taken together reveal the role played by solution entropy in addition to that of electrostatic and solute-solvent interactions, which had been overlooked hitherto.

Preparation of hydroxyapatite-gelatin nanocomposite

A nanocomposite of gelatin[GEL]-hydroxyapatite[HAp] was prepared using the biomimetic process. The hydroxyapatite nanocrystals were precipitated in aqueous solution of gelatin at pH 8 and 38°C. The chemical bonding between calcium ions of HAp and carboxyl ions of GEL molecules induced a red-shift of the 1339 cm −1 band of GEL in FT-IR analysis. TEM images and electron diffraction patterns for the nanocomposite strongly indicate the self-organization of HAp nanocrystals along the GEL fibrils. Electron diffraction for the nanocomposites showed a strong preferred orientation of the (0 0 2) plane in HAp nanocrystals. The development of HAp nanocrystals in an aqueous GEL solution was highly influenced by the concentration ratio of GEL to HAp. A higher concentration of GEL induced the formation of tiny crystallites (4 nm×9 nm size), while a lower concentration of GEL contributed to the development of bigger crystallites (30 nm×70 nm size). From DT/TGA data, the HAp-GEL nanocomposite showed typically three exothermic temperatures. The increase in decomposition temperatures indicates the formation of a primary chemical bond between HAp and GEL. The higher concentration of GEL supplies abundant reaction sites containing groups such as carboxyl, which can bind with calcium ions. The abundant supply of reaction sites leads to a very large number of HAp nuclei. However, the formation of a large number of nuclei depletes the concentration of calcium ions that available for growth to the extent that the nuclei cannot grow very large. This in turn will lead to the creation of a large number of tiny nanocrystals at this higher GEL concentration.

Porous spherical hydroxyapatite and fluorhydroxyapatite granules: processing and characterization

This study is aimed at the development of a method to fabricate porous spherical hydroxyapatite (HA)—fluorapatite (FA) granules. The method to produce porous granules is based on liquid immiscibility effect. A suspension of HA–FA powder mixtures in aqueous solution of gelatin and oil as a dispersion media were used. By stirring the mixtures of these immiscible liquids, granules of 50—200 mm diameter can easily be produced. The granules were characterized with respect to their microstructure, phase composition and specific area. In vitro testing of human plasma protein adsorption onto the granules of HA and fluorhydroxyapatite were performed. No kind of difference in the dynamic protein adsorption between pure HA and the HA up to 10 wt% FA materials has been revealed.

Influence of the Molecular‐Mass Distribution of Gelatins Modified with a LIKI‐1 Tanning Agent on the Rheological Parameters of Interphase Adsorption Layers at the Interfase of an Aqueous Solution of Gelatin–Metaxylene

The influence of the interaction of gelatin with a protected formaldehyde tanning agent on the rheological parameters of interphase adsorption layers formed at the interface of a 0.1% aqueous solution of gelatin–metaxylene has been investigated as a function of the mass‐molecular distribution of initial gelatins. It has been shown that the chemical modification of gelatin with tanning agents weakens the process of gel formation in the interphase layer directly with the depth of the tanning process. This dependence is the most pronounced for gelatin with a high content of fractions with a molecular mass of more than 285 kDa.

Fabrication of micropored elastomeric film-covered stents and acute-phase performances.

To prevent thrombus formation in the acute phase and restenosis in the subacute to chronic phase after stenting of atherosclerotic arteries, we developed a covered stent with a micropored elastomeric film, the blood-contacting surface of which was coated with a photocured gelatin layer immobilized with heparin. Segmented polyurethane (SPU) film (30 microm in wall thickness) as a cover material was multiply micropored by excimer laser-directed microprocessing (pore diameter, 30 microm; interpore distance, 125 microm). An aqueous mixed solution of benzophenone-derivatized gelatin and heparin was coated on the micropored SPU film. Upon ultraviolet light irradiation, a thin layer of a gelatin gel immobilized with heparin was formed and simultaneously fixed on the SPU film. The fully covered stents were assembled by wrapping a balloon-expandable stent with gelatin/heparin gel-layered SPU film and subsequently suturing and then gluing. To assess the validity of this covered stent in vivo, "half-covered" stents, in which half at the distal side was covered with the gel-layered SPU film, was implanted in rabbit common carotid arteries (about 3 mm in diameter). After 3 months of implantation, all the half-covered stents (n = 7) were patent. Regardless of the covered or noncovered region of the stents, the entire luminal surface of the stents was fully endothelialized and a thin neointimal tissue was formed. The potential advantages of a covered stent as designed above are discussed.