Evaluation of Hardening Using the Sol Fraction of Gelatin Films (Review)

The low molecular weight component of gelatin has been investigated by determination of the molecular weight distribution of the sol fraction from hardened gelatin films. The hardeners used were formaldehyde and mucochloric acid. Different hardening conditions and gelatin types were studied. It was observed that a couple of weeks were needed to reach a stable level of hardening. Acid- processed gelatins exhibited higher reactivity than lime-processed gelatins. The results indicate that the method seems to be effective as an evaluation of gelatin hardening.     

Gelatin capsule residue-based films crosslinked with the natural agent genipin

This study focused on the development and characterization of biodegradable films based on gelatin capsule residue crosslinked with the natural agent genipin extracted from genipap (Genipa americana L.). Their potential on maintaining the quality attributes (level of peroxides, conjugated dienes and trienes and color) of extra-virgin olive oil under accelerated storage conditions was investigated. Results showed that the genipin-crosslinked films had a dark blue appearance. Their total soluble matter, water vapor permeability, tensile strength, ultraviolet and visible light barriers and thermal properties were improved in relation to the uncrosslinked film, whereas their moisture content and microstructure were not affected. In general, films presented comparable properties to those of glutaraldehyde-crosslinked films. The developed films successfully protected the packed oil from primary and secondary oxidation and maintained the color over the storage period. Therefore, this study demonstrated the effectiveness of genipin on improving the properties of gelatin-based films and the promising application of films as food packaging.     

聚合物坚膜助剂的合成与性能研究

坚膜剂是重要的照相有机物助剂，照相明胶的坚膜是决定胶片物理机械性能和保证感光性能的主要因素，本研究合成了一系列聚合物型坚膜助剂并对其与明胶的作用进行了研究。     

Bio-nanocomposites by assembling of gelatin and layered perovskite mixed oxides

A new class of bio-nanocomposites based on hybrid gelatin-perovskite hydrogels was prepared by mixing exfoliated perovskite-tetraalkylammonium species in aqueous suspensions with gelatin solutions. Colloidal nanosheets derived from the CsCa2Nb3O10 layered perovskite re-stacked in the gelatin solutions give bio-nanocomposite materials with different content in the inorganic moiety. These films can be easily processed as homogeneous self-supported films. The partial exfoliation of the pristine mixed oxide is produced from alkylammonium exchanged phases, being the tetraalkylammonium ions (tetraethylammonium, TEA+) an efficient intermediate to give the colloid phase constituted by well exfoliated materials useful to generate homogeneous films. The nanosheets are highly oriented in the bio-nanocomposite films in agreement with the XRD patterns and the FTIR dichroism. This orientation could be considered as a characteristic of this type of hybrid materials leading to new potential applications. In this way, we have observed that the assembling of perovskite to gelatin produces a greater increase of the dielectric permittivity than the dielectric loss in the studied samples.     

Physical Ripening of Photographic Emulsions with Hardened Gelatin

The paper presents information about the conditions in which the hardeners formaldehyde and chromic acetate can effect the kinetics of the physical ripening of “neutral” and ammoniacal silver bromide emulsions obtained at various excesses of potassium bromide. When a gelatin is partially hardened, there is no effect on the physical ripening of fine-grained emulsions. The crystal growth is restrained as a consequence of the hardening only when the emulsion grains are larger. In this case it is assumed that on the grain surface are formed thicker or more compact adsorption layers of gelatin, which reduce the rate of the diffusion processes and, hence, the rate of crystal growth. Chromic acetate exerts very strong restraining action on ammoniacal emulsions. This effect is explained not by the hardening of gelatin, but by the formation of chromic ammonia complex ions, which block the active centres of crystal growth on grain surface.     

Contributions of Chemical Crosslinks and Ordered Structure to the Physical Properties of Swollen Gelatin Films (Summary)

Chemical crosslinks in gelatin films formed by reaction with bisacryloylurea have been quantitated using amino acid analysis and radiochemical techniques. Swollen hot-dried, crosslinked films were found to show the same specific optical rotation as gelatin solutions at 40°C and are felt to be without ordered structure. The number of crosslinks in hot-dried films was calculated from tensile measurements on the swollen films using rubber elasticity theory. These figures agreed well with the chemical analysis. Hot-dried and cold-dried films at the same level of bisacryloyurea showed roughly the same amount of reaction with the bisacryloylurea. However, the moduli of elasticity of the swollen cold-dried films were three to ten times greater than those of hot-dried films containing the same number of chemical crosslinks. The crosslinks in the cold-dried films maintain levorotation indicative of ordered structure at temperatures and volume fractions at which similar structure in uncrosslinked gels and in hot-dried films has melted.

Similar work has been carried out using ¹⁴C-tagged formaldehyde as the crosslinking reagent. Levels of both free and bound formaldehyde were found to be much higher than the actual number of physical crosslinks.     

Hydrogel-elastomer composite biomaterials: 2. Effects of aging methacrylated gelatin solutions on the preparation and physical properties of interpenetrating polymer networks

This study was conducted to understand the effects of aging methacrylated gelatin solutions on the properties of gelatin-HydroThane^TM Interpenetrating Polymer Network (IPN) films. The latter were prepared from methacrylated gelatin solutions that were either freshly made or stored at different concentrations and temperatures for various periods. The morphology, swelling stability and mechanical properties of the IPNs were then accordingly characterized. The IPNs prepared with aged solutions showed a reduced phase separation; changed from a network-like structure to a continuous phase structure; and demonstrated higher swelling stabilities and higher elasticity under optimal aging conditions, compared to the IPN prepared with a fresh methacrylated gelatin solution. An increase in viscosity and a change in phase transition of aged methacrylated gelatin solutions were also observed, presumably due to the physical structuring of methacrylated gelatin chains (e.g., by the formation of a helix structure), thus altering the resulting IPN characteristics. A better understanding of the effects of aging methacrylated gelatin solution on the formation and properties of gelatin-HydroThane^TM IPNs should enable us to further develop our composite biomaterials for different dressing applications.     

The Mechanism of the Crosslinking Reaction of Gelatin with Hardener

The reaction, in solution, between gelatin and various hardeners has been examined by gel permeation chromatography, HPLC and amino acid analysis. It is concluded that there are two types of crosslinking reaction. One of them is the reaction between the hardener and the lysine and hydroxylysine residues in gelatin, whilst the other is the reaction between the hardener and the amino acid residues, except lysine and hydroxylysine. The crosslinking reactions are influenced by the reaction conditions including pH value, concentration etc. The amount of unrcacted lysine, determined by amino acid analysis, correlates with the reduction in the level of a-component due to the crosslinking reaction. It is considered that the results suggest that interchain crosslinking reactions, at the lysine and hydroxylysine residues, mainly take place in gelatin solution.     

感光乳剂快速坚膜剂

本文扼要总结了用于制备感光乳剂,尤其是彩色胶片的新型有机坚膜剂,其应用能使胶片感光层快速坚膜,适应高温快速冲洗加工。     

Development of chitosan/gelatin/keratin composite containing hydrocortisone sodium succinate as a buccal mucoadhesive patch to treat desquamative gingivitis

The aim of this research was to develop chitosan/gelatin/keratin composite containing hydrocortisone sodium succinate as a buccal mucoadhesive patch to treat desquamative gingivitis, which was fabricated through an environmental friendly process. Mucoadhesive films increase the advantage of higher efficiency and drug localization in the affected region. In this research, mucoadhesive films, for the release of hydrocortisone sodium succinate, were prepared using different ratios of chitosan, gelatin and keratin. In the first step, chitosan and gelatin proportions were optimized after evaluating the mechanical properties, swelling capacity, water uptake, stability, and biodegradation of the films. Then, keratin was added at different percentages to the optimum composite of chitosan and gelatin together with the drug. The results of surface pH showed that none of the samples were harmful to the buccal cavity. FTIR analysis confirmed the influence of keratin on the structure of the composite. The presence of a higher amount of keratin in the composite films resulted in high mechanical, mucoadhesive properties and stability, low water uptake and biodegradation in phosphate buffer saline (pH?=?7.4) containing 10⁴?U/ml lysozyme. The release profile of the films ascertained that keratin is a rate controller in the release of the hydrocortisone sodium succinate. Finally, chitosan/gelatin/keratin composite containing hydrocortisone sodium succinate can be employed in dental applications.     

Release of liposome-encapsulated calcein from liposome entrapping gelatin-carboxymethylcellulose films: a presentation of different possibilities

Liposome entrapment in films consisting of gelatin (GEL) or GEL/sodium carboxymethylcellulose (NaCMC) mixtures, as a method to alter drug release kinetics from polymeric films and/or incorporate sensitive bioactive molecules in solid films, was investigated. Bulk or thin complex (liposome trapping) films were formed by crosslinking (with glutaraldehyde) solutions of GEL or GEL/NaCMC in presence of calcein-encapsulating or rhodamine-labeled liposomes (Rho-Lip). Rho-Lip were observed by confocal microscopy to be homogenously distributed in the films. Calcein release from films was evaluated for periods up to 25 d, and it was found that several possibilities, concerning the release of the liposome-encapsulated molecule from the films, are offered; (i) Release can be sustained, if large liposomes are entrapped in the films. In this case the liposome-encapsulated molecules are released from the films only after they have been released from the vesicles, and the release can be controlled by modifying the film composition, the network density and/or the film geometry. (ii) Intact small unilamellar liposomes (SUV) can be released from the polymeric films depending on their swelling degree. The later can be controlled by modulating the film composition and amount of crosslinker. Film composition also affects the integrity of the film-entrapped liposomes during the crosslinking process, possibly due its effect on the density of the polymeric network of the film.     

Effect of chemical treatment on the mechanical properties,water vapour permeability and sorption isotherms of gelatin‐based films

Proteins contain hydrophilic groups, which can bind to water molecules through hydrogen bridges, resulting in water vapour adsorption. An increase in the degree of cross‐linking can be a method to improve the cohesiveness force and functional properties of protein‐based films. Thus, the objective of this work was to evaluate the effect of chemical treatment of gelatin with formaldehyde and glyoxal on the mechanical properties, water vapour permeability (WVP) and water vapour sorption characteristics of gelatin‐based films. Films were produced using gelatin, with and without chemical treatment. The formaldehyde treatments caused a significant increase in the tensile strength and a reduction in the WVP of films. The Guggenheim‐Anderson‐De Boer and Halsey models could be used to model the sorption isotherms of films. It was observed that an increase in temperature produced a decrease in water sorption, and the chemical modifications did not affect the monolayer moisture content. Copyright © 2007 John Wiley & Sons, Ltd.     

明胶/海藻酸钠(京尼平交联)互穿网络膜的制备与性能

为了提高海藻酸钠与明胶各自的性能,首先,以海藻酸钠和明胶为原料,以京尼平、CaCl2为交联剂,采用分步交联法制备了明胶/海藻酸钠互穿网络膜。然后,利用FTIR对明胶/海藻酸钠互穿网络结构进行了表征与分析,根据FTIR结果推测了互穿网络结构形成的机制。最后,探讨了京尼平的加入量和明胶与京尼平的质量比对互穿网络膜力学性能和交联度的影响,及海藻酸钠与明胶的质量比对互穿网络膜力学性能、断面形貌、热稳定性和吸水保水性能的影响。结果表明:当明胶与京尼平的质量比为200∶1、海藻酸钠与明胶的质量比为2∶1时,互穿网络膜具有最佳的力学性能、吸水保水性能和相容性;此外,互穿网络膜的力学性能也优于纯海藻酸钠膜与纯明胶膜的。明胶的加入提高了互穿网络膜在低温区的热稳定性,但降低了高温区的热稳定性。海藻酸钠与明胶之间可能以分子间作用力、氢键及离子键等相互作用,提高了二者各自的初始分解温度与最大热分解温度。研究解决了海藻酸钠与明胶力学性能差的问题,为拓展海藻酸钠在医用领域的应用提供参考。     

Mechanical Properties of Gelatin Film

Abstract

The mechanical properties of gelatin films were investigated. We prepared gelatin films under various conditions, such as changing temperature, storage time and humidity. The stress-strain curves were obtained by measuring the tensile-strength of sample films at various humidities. These results suggest that mechanical properties of gelatin films depend on the structure and water content of the sample. It was found that the structure of gelatin films was influenced by the drying process and the thermal history of the gelatin.     

明胶-壳聚糖复合膜的制备与性能

制备了一系列不同配比的明胶-壳聚糖复合膜,研究了壳聚糖含量对复合膜力学性能、吸湿性能的影响,通过X射线衍射和红外光谱分析了复合膜的结构。结果表明,复合膜及纯壳聚糖膜的断裂伸长率和拉伸强度均大于纯明胶膜,壳聚糖的加入可改善膜的力学性能。随壳聚糖含量的增加,复合膜的吸湿率增大。明胶与壳聚糖分子间存在较强的相互作用,与明胶共...     

可食性明胶-魔芋葡甘聚糖共混膜的制备与性能研究

采用溶液共混法制备了一系列不同比例的明胶-魔芋葡甘聚糖共混膜,研究了明胶含量(质量分数)对共混膜的力学性能、吸湿性能、透光性能的影响。结果表明,明胶的引入,有利于改善魔芋葡甘聚糖膜的力学性能,减小魔芋葡甘聚糖膜的吸水率,明胶与魔芋葡甘聚糖的相容性良好。     

The Diffusion of Potassium Bromide through Gelatin Gels

The diffusion coefficient of potassium bromide in gelatin gels was determined by setting the gel, containing a little silver chromate os an indicator, in a capillary tube, and observing the movement of the boundary of silver bromide formed when one end of the capillary tube was immersed in 0·1 M potassium bromide solution.

The diffusion coefficient was independent of intrinsic properties of the gelatin but depended on the concentration of the gel. This conclusion is likely to apply equally to the diffusion of other low-molecular-weight substances that do not interact strongly with gelatin. The rate of diffusion decreased linearly with gelatin concentration up to a value of 40 per cent at which concentration it was 0·35 times the value in water.

Sodium sulphate and sucrose added to the gelatin only, or distributed equally in gel and solution, reduced the diffusion rate by an amount approximately equal to that of an equal weight of gelatin. Cyanamer had a rather greater effect than gelatin.

It is concluded that hardening of photographic films by reduction of swelling will decrease the diffusion coefficient within the layer, but will increase the rote of penetration of solutions into the layer due to the reduction in diffusion path length.     

花青素-明胶/聚乙烯醇-淀粉复合膜制备与表征

目的 制备花青素明胶/聚乙烯醇淀粉双层复合膜,以期提高花青素单层膜的综合性能.方法 采用流延法分别制备紫薯、紫甘蓝、黑米、黑枸杞、玫瑰、玫瑰茄等6种花青素明胶/聚乙烯醇淀粉双层复合膜,并对比研究膜层的微观组织结构、含水率、力学性能及光学性能.结果 从红外光谱图中可以看出,双层复合膜分子结构没有出现新的特征峰,双层膜结合方式为物理结合,没有新的结构生成,且除紫甘蓝明胶/聚乙烯醇淀粉双层复合膜外,其余复合膜均存在明显的分层界线,2层结合处膜层结构均匀致密,结合良好.不同双层膜的含水率差异显著,而双层复合膜比花青素单层膜的含水率明显降低,不同双层膜的拉伸强度和断裂伸长率差异不显著,与单层花青素明胶复合膜相比,双层复合膜的拉伸强度和断裂伸长率大幅增加,其中紫薯双层膜的拉伸强度增加了75％,断裂伸长率增加了22.9％;所有双层复合膜的透光率相差不大,均在80％以上;与花青素明胶单层膜相比,双层膜的雾度增加了20％左右.结论 制备的双层膜改善了单层膜的力学性能,提高了花青素明胶单层膜的综合性能.     

阿魏酸和明胶对大豆蛋白包装膜性能的影响

添加阿魏酸和明胶,制备大豆蛋白包装膜,研究了阿魏酸、明胶对大豆蛋白包装膜的力学性能、透湿性能、雾度、透光率的影响。研究表明:加入阿魏酸后,大豆蛋白膜的性能明显提高,膜的拉伸强度、断裂伸长率、撕裂强度都显著上升;加入阿魏酸和明胶后,冲击强度、撕裂强度进一步上升,而拉伸强度和断裂伸长率下降;加入阿魏酸和明胶后,膜的透光率下降,雾度上升。     

Preparation of reduced graphene oxide/gelatin composite films with reinforced mechanical strength

Graphene oxide (GO) was reduced by chitosan/gelatin solution and added to gelatin (Gel) to fabricate reduced graphene oxide/gelatin (RGO/Gel) films by a solvent-casting method using genipin as cross-linking agent. The structure and properties of the films were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) and UV–vis spectroscopy. The addition of RGO increased the tensile strength of the RGO/Gel films in both dry and wet states, but decreased their elongation at break. The incorperation of RGO also decreased the swelling ability of the films in water. Cell cultures were carried out in order to test the cytotoxicity of the films. The cells grew and reproduced well on the RGO/Gel films, indicating that the addition of RGO has no negative effect on the compatibility of the gelatin. Therefore, the reduced graphene oxide/gelatin composite is a promising biomaterial with excellent mechanical properties and good cell compatibility.