Showing papers on "Gelatin published in 1996"

Fabrication of biodegradable polymer scaffolds to engineer trabecular bone

Abstract: We present a novel method for manufacturing three-dimensional, biodegradable poly(DLlactic-co-glycolic acid) (PLGA) foam scaffolds for use in bone regeneration. The technique involves the formation of a composite material consisting of gelatin microspheres surrounded by a PLGA matrix. The gelatin microspheres are leached out leaving an open-cell foam with a pore size and morphology defined by the gelatin microspheres. The foam porosity can be controlled by altering the volume fraction of gelatin used to make the composite material. PLGA 50 : 50 was used as a model degradable polymer to establish the effect of porosity, pore size, and degradation on foam mechanical properties. The yield strengths and moduli in compression of PLGA 50: 50 foams were found to decrease with increasing porosity according to power law relationships. These mechanical properties were however, largely unaffected by pore size. Foams with yield strengths up to 3.2 MPa were manufactured. From in vitro degradation studies we establishe...

Chemical and Swelling Evaluations of Amino Group Crosslinking in Gelatin and Modified Gelatin Matrices

Abstract: Purpose. To determine the extent of amino group crosslinking in gelatin matrices by chemical assay, and to compare these results to crosslinking evaluations from swelling measurements. Methods. Matrices crosslinked with a water soluble carbodiimide (EDC/G), glutaraldehyde (GTA/G), as well as a GTA crosslinked matrix prepared from gelatin modified to contain 230% greater crosslinking sites (GTA/Mod) were evaluated. Crosslinking extent, X c, was determined by a UV assay of uncrosslinked amino groups before and after crosslinking, and was used to obtain crosslinking densities. Equilibrium swelling ratios, Q m at 37°C in isotonic pH 7.4 were used to calculate crosslinking degree from the Flory equation for swelling of ionic polymers for comparison to the chemically determined crosslinking densities. Results. Of the original 33 × 10−5 moles e-amino groups/g gelatin, 91 to 95% were crosslinked in EDC/G and GTA/G. GTA/Mod lost 95% of the original 108 × 10−5 moles amino groups/g gelatin. Crosslinking densities were 4.1 × 10−4 and 4.2 × 10−4 moles/mL for EDC/G and GTA/G, respectively. The value for GTA/Mod increased to 14.2 × 10−4 moles/mL. Values of Q m followed the same trend. The Flory crosslinking degrees for both gelatin matrices were 12 × 10−4 and 13 × 10−4 moles/mL, respectively. The value for the more extensively crosslinked GTA/Mod was 280 × 10−4moles/mL. Conclusions. The swelling and chemical evaluations of crosslinking are in general agreement for matrices with the lower of two crosslinking levels. The chemical determination appears suitable for evaluating amino group crosslinking in gelatin and it may be suitable for other proteinaceous materials.

A new biological glue from gelatin and poly(L-glutamic acid)

Abstract: This study describes the potentiality of hydrogels composed of gelatin and poly(L-glutamic acid) (PLGA) as a biological glue for soft tissues and compares its effectiveness with that of a conventional fibrin glue. Water-soluble carbodiimides (WSC) were used to crosslink the aqueous mixture of gelatin and PLGA. The mixed aqueous solution of gelatin and PLGA set to a hydrogel by use of WSC as rapidly as BOLHEAL® fibrin glue. An addition of PLGA to gelatin aqueous solution reduced not only its gelation time but also the WSC concentration necessary for hydrogel formation. The cured hydrogel exhibited firm adhesion to the mouse skin and other soft tissues with a higher bonding strength than BOLHEAL® fibrin glue. Cohesive failure in the hydrogel was observed when the gel-tissue bond was broken, in contrast to BOLHEAL® fibrin glue. The bonding strength of the gelatin-PLGA hydrogel became higher with the increasing PLGA concentration. The inflammatory reaction around the gelatin-PLGA hydrogel subcutaneously implanted in mice was mild, and the hydrogel was gradually absorbed with time in vivo. A toxicity test demonstrated that the concentration of WSC necessary as a biological glue was low enough not to induce its toxicity. © 1996 John Wiley & Sons, Inc.

Preparation and Some Properties of Type I Collagen from Fish Scales

Abstract: Soluble collagen from fish (sardine) scales was yielded at about 5% with 0.5 M acetic acid after demineralization with EDTA, while a great portion of the collagen remained insoluble. The solubility of this insoluble collagen was about 20% at 45 degrees C (denaturation temperature of soluble collagen) for 24 h. The remaining 80% of the insoluble collagen was denatured in the form of insoluble gelatin, and that may be an interesting food material.

Interaction between gelatin and anionic surfactants

Abstract: The effects of alkyl chain length of homologous alkyl sulfate surfactants ranging from C8 to C14 on the diffusion behavior of both the surfactant and gelatin have been investigated by pulsed-gradient spin-echo NMR spectroscopy. Changes in the diffusivity of the surfactant can be rationalized in terms of a two-state model consisting of gelatin-bound micelles in equilibrium with freely diffusing unimeric surfactant. A minimum in the diffusivity of gelatin is observed when the binding of surfactant amounts to about 1 micelle/strand. The depth of this minimum increases with the chain length of the surfactant. These effects are explained in terms of micelle-mediated transient cross-links as proposed by Greener et al. (Macromolecules 1987, 20, 2490). The effective strength of the cross-links is a decreasing function of the number of micelles/strand because of the electrostatic repulsion between the micelles; the strength increases with an increase in the size of the micelles.

Mechanical properties and transition temperatures of cross-linked oriented gelatin. 1. Static and dynamic mechanical properties of cross-linked gelatin

Abstract: This study is an extension of previous work on cellulosics [(1994)Colloid Polym Sci 272: 284, 393] that showed that unusually good mechanical properties can be obtained by drying a swollen network of semirigid chains in a state of strain. This novel approach is applied in this investigation to gelatin, because of its attractive environmental characteristics but poor mechanical properties in the unmodified form. Since drawing of non-crosslinked gelatin is not practical, crosslinking by formaldehyde was used, followed by swelling, drawing and drying at fixed length. Mechanical tests were performed in static and dynamic modes. In this way improvements of Young's modulusE, and stress at breakσ b were determined as a function of gelatin concentration during drying. An increase inE andσ b up to 2–3 times, and in the dynamic modulusE′ up to 6 times, was obtained when the draw ratio λ reached 4–5, after whichE, E′, andσ b were found to decrease. Such behavior is explained by the highest orientation being achieved at λ=4–5, as proved by x-ray analysis. At λ=10–20 the orientation is lost due to relaxation of chain segments, which is preceded by partial destroying of the network structure (chemical and physical), possibly via chain scission, but probably mostly by the pulling out of chains from crystallites. In any case, the mechanical properties become poor again. The improvements reported above were referred to the undrawn but crosslinked gelatin. Compared to the starting isotropic non-crosslinked material, the improvement is slightly higher. The observation that the improvements are less than those obtained for the cellulosics is explained by the coexistence of interpenetrating chemical and physical networks, which is typical of gelatin. This structural feature drastically reduces the orientability of the chains and the improvements that can be expected in the mechanical properties.

Hydrogels of Gelatin-Sodium Carboxymethyl Cellulose: Synthesis and Swelling Kinetics

Abstract: Hydrogels of gelatin crosslinked with glutaraldehyde and sodium carboxymethyl cellulose (NaCMC) of several compositions were prepared. The swelling kinetics as a function of composition, temperature. pH, and ionic strength was studied. The rate of swelling and equilibrium swelling were found to depend on the NaCMC content in all cases. The equilibrium swelling increased with the temperature. The gels, which were weakly acidic, registered increased swelling at higher pH. Swelling was suppressed in aqueous salt solutions. In agreement with predictions of the Donnan theory, swelling in monovalent salt solutions is greater than in divalent salt solutions.

Protein ternary phase diagrams. 1. Effect of ethanol, ammonium sulfate, and temperature on the phase behavior of type B gelatin

Abstract: The effect of ethanol or (NH4)2SO4 addition on aqueous gelatin solution (pH 7.0) phase behavior was examined in the temperature range from 10 to 70 °C for protein and solute concentrations of 0−100 wt %. Ternary phase diagrams were used to effectively illustrate the relationship between the seven protein morphologies observed. Gelatin only exists as a random coil structure above 40 °C. As a result, in ethanol and salt systems below 30 °C, one-phase or two-phase gel and liquid morphologies dominated. In contrast, above 50 °C, one-phase sol or two-phase coacervate morphologies occupied significant portions of the two phase diagram systems. Between 30 and 50 °C, a wide range of morphologies was observed in both systems, as the gelatin gradually transformed to a more random structure. Differences observed between the various gelatin phase diagrams were a result of altered protein−solute, intraprotein, and interprotein interactions caused by changing temperature, ethanol, and (NH4)2SO4 concentrations. Keywords...

Edible Coatings from Candelilla Wax Microemulsions

Abstract: Candelilla wax coatings with good gloss were made. The gloss of coatings from ammonia-based microemulsions was improved by addition of gelatin or hydroxypropyl methylcellulose, which also decreased oxygen permeability and decreased water vapor permeability. As coatings on grapefruit, candelilla wax with up to 25% gelatin was usable; much higher gelatin content resulted in anaerobic fermentation. Candelilla coatings with good gloss were also made from morpholine-based wax microemulsions with minimal oleic acid content.

A Self-Diffusion Study of the Complex Formed by Sodium Dodecyl Sulfate and Gelatin in Aqueous Solutions

Abstract: The diffusion behavior of both the anionic surfactant sodium dodecyl sulfate and gelatin have been studied by pulsed-gradient spin-echo NMR spectroscopy (PGSE-NMR) in aqueous solutions at 44 °C, well above the setting temperature. The studies were made as a function of both surfactant and gelatin concentration for two different lime-processed gelatin samples: one the standard photographic material, the other a fractionated sample. Above c*, the fractionated and standard gelatins exhibit different behavior in both the presence and absence of SDS. Adding SDS slows the diffusion of the gelatin, which passes through a minimum with increasing surfactant concentration. The diffusion data are compared to light scattering, small-angle neutron scattering and viscosity data from similar systems. An isotherm characterizing the SDS binding to the gelatin has been derived from the self-diffusion data.

Improved topical application emulsions

Abstract: The present invention relates in general to products for topical application to the skin, and more particularly to improved stable emulsions for containing water-soluble active ingredients, such as Vitamin C, glycolic acid, etc., which may nonetheless be packaged with gelatin capsules, and which have demonstrated improved stability. In particular, the invention relates to a novel polyethylene glycol-in-oil emulsion that is compatible with gelatin capsules.

Gelatin capsule having adjusted water activity

Abstract: A gelatin capsule having adjusted water activity and preserved in a closed system, which contains, packed herein, an additive(s) selected from the group consisting of carboxymethyl cellulose calcium, crosscarmellose sodium, partially gelatinized starch and polyvinyl polypyrrolidone in the proportion of 50 to 150 wt. % of the total quantity of the gelatin of the said capsule.

Cross-linking of gelatin with carbodiimides.

Abstract: Carbodiimides were employed for cross-linking of gelatin through amide bond formation to avoid any foreign bond incorporation into the cross-linked gelatin molecules. Cross-linking of gelatin was performed not in aqueous solution but in the form of a film under a heterogenous condition. Ethanol-water mixtures were used as the reaction medium to prevent dissolution of gelatin films. The optimal ethanol concentration in the ethanol-water mixtures was around 80 vol%, and the water content of the cross-linked gelatin film attained after swelling with water at 25 degrees C was as low as 55 wt%. A water-soluble carbodiimide (l-ethyl-3[3-dimethylaminoprophyl] carbodiimide) was more effective for gelatin cross-linking than a water-insoluble carbodiimide (1,3-dicyclohexyl carbodiimide). The optimal temperature for cross-linking with the water-soluble carbodiimide ranged between 15 and 25 degrees C. It was concluded that gelatin cross-linking with carbodiimides is as effective as that with glutaraldehyde, which is most widely used despite the toxicity, at least, so far as the water content of cross-linked gelatin film is concerned.