明胶及其酰化产物的沉降性能

本文研究了明胶和酰化明胶溶液的沉降性能,考察了试剂用量及pH值对沉降性能的影响,找出了一些基本的规律,发现了氯化钠盐析与乙醇、丙酮溶剂沉降时,明胶和酰化明胶沉降效率的不同,并从理论上进行了初步的探讨。     

热降解明胶的研究

报道了明胶热降解反应,并考察了明胶质量分数、降解时间、降解温度、明胶溶液pH值等因素对明胶热降解反应的影响规律。结果表明:热催化是明胶降解的有效方法,较合适的降解条件为明胶质量分数10%,体系pH值7.00,降解温度121℃,降解时间2 h。     

明胶对明胶/壳聚糖共混膜性能影响的研究

采用溶液共混法制备出了一系列明胶／壳聚糖共混膜,并考察了制备条件对膜性能的影响。结果表明：明胶的溶解方式对吸水率和溶胀比影响很小;随明胶分子量增加,共混膜的吸水率和孔洞体积增大;而随共混体系中明胶质量分数的增加,吸水率和孔洞体积亦增加,但溶胀比下降。     

Electrospinning and mechanical characterization of gelatin nanofibers

This paper investigates electrospinning of a natural biopolymer, gelatin, and the mass concentration-mechanical property relationship of the resulting nanofiber membranes. It has been recognized that although gelatin can be easily dissolved in water the gelatin/water solution was unable to electrospin into ultra fine fibers. A different organic solvent, 2,2,2-trifluoroethanol, is proven suitable for gelatin, and the resulting solution with a mass concentration in between 5 and 12.5% can be successfully electrospun into nanofibers of a diameter in a range from 100 to 340 nm. Further lower or higher mass concentration was inapplicable in electrospinning at ambient conditions. We have found in this study that the highest mechanical behavior did not occur to the nanofibrous membrane electrospun from the lowest or the highest mass concentration solution. Instead, the nanofiber mat that had the finest fiber structure and no beads on surface obtained from the 7.5% mass concentration exhibited the largest tensile modulus and ultimate tensile strength, which are respectively 40 and 60% greater than those produced from the remaining mass concentration, i.e. 5, 10, and 12.5%, solutions.     

Crosslinking of the electrospun gelatin nanofibers

Gelatin (Gt) nanofibers have been prepared by using an electrospinning process in a previous study. In order to improve their water-resistant ability and thermomechnical performance for potential biomedical applications, in this article, the electrospun gelatin nanofibers were crosslinked with saturated glutaraldehyde (GTA) vapor at room temperature. An exposure of this nanofibrous material in the GTA vapor for 3 days generated a crosslinking extent sufficient to preserve the fibrous morphology tested by soaking in 37 °C warm water. On the other hand, the crosslinking also led to improved thermostability and substantial enhancement in mechanical properties. The denaturation temperature corresponding to the helix to coil transition of the air-dried samples increased by about 11 °C and the tensile strength and modulus were nearly 10 times higher than those of the as-electrospun gelatin fibers. Furthermore, cytotoxicity was evaluated based on a cell proliferation study by culturing human dermal fibroblasts (HDFs) on the crosslinked gelatin fibrous scaffolds for 1, 3, 5 and 7 days. It was found cell expansion took place and almost linearly increased during the course of whole period of the cell culture. The initial inhibition of cell expansion on the crosslinked gelatin fibrous substrate suggested some cytotoxic effect of the residual GTA on the cells.     

Characterization of gelatin nanofiber prepared from gelatin-formic acid solution

Gelatin, well known as a biocompatible polymer, was dissolved in formic acid and gelatin nanofiber was successfully prepared by the electrospinning using gelatin-formic acid dope solution. Stability of the dope solution was evaluated by measuring viscosity change with time. Even though the viscosity dropped markedly after 5 h, the spinnability and morphology of gelatin nanofiber were not affected at all. The parameters, such as electric field, spinning distance, and concentration of dope solution, were examined for studying the effects on electrospinnability and morphology (size, size distribution, uniformity, bead formation, etc.) of gelatin nanofiber web. The gelatin nanofibers, in the mean size of 70-170 nm, could be prepared by controlling the dope concentration under proper conditions. The electrospun gelatin nanofiber exhibited a mixture of α-helical and random coil conformation, which was amorphous structure with very low crystallinity. The structural transformation, from a helical (α-helix and triple-helix) to random coil conformation, might occur when formic acid was used for the dissolution of gelatin in electrospinning.     

Concentration of gelatin solution with polyethersulfone ultrafiltration membranes

In this work, polyethersulfone (PES) flat sheet ultrafiltration (UF) membranes were prepared by immersion precipitation phase inversion process with polyvinylpyrrolidone (PVP 30K) and acetone as additives. The best preparation condition for PES membranes with high water flux and rejection (to BSA) was decided. It was found that the optimal composition of the polymer casting solution was: 16 wt% (PES), 2 wt% (PVP 30K), and 1 wt% (acetone). Pure water flux of the membrane prepared at this condition reached to 373 L/m² h at 0.1 MPa, and the rejection to BSA was 91%. Compared with other reports, the rejection was slightly low but the flux of the PES membrane was high. When the membrane was used to concentrate gelatin solutions, the rejection value was over 75%. It was found that increasing the feed temperature and transmembrane pressure enhanced the permeation flux, but the rejection decreased slightly. However, increasing the cross-flow velocity of the feed solution simultaneously increased both the permeation flux and the rejection.     

Studies on preparation and properties of PAA/gelatin core-shell nanoparticles via template polymerization

Taking advantage of the simultaneous polymerization and self-assembly between the components during the template polymerization, narrowly distributed nanoparticles with core-shell structure were prepared at high concentrations via polymerizing acrylic acid (AA) in aqueous solution of template gelatin. The influences of various polymerization parameters such as medium pH, concentration, and ratio of AA/gelatin were systematically investigated, which indicates that the size and structure of the nanoparticles can be adjusted by changing the reaction conditions. The nanoparticles are stimuli-responsive: the nanoparticles' size increases when increasing or decreasing pH value from about 2.8 while it first decreases slightly and then increases monotonically as salt concentration increases. Also, the nanoparticles exhibit a stronger salt-resistance as compared with those prepared by dropping method. The structure of the nanoparticles was further locked by selectively crosslinking gelatin with glutaraldehyde. The size and swelling capacity of the nanoparticles decrease with the increase of crosslinking degree.     

Influence of thermal treatments on the structure and stability of gelatin gels

The influence of thermal history on the structure of gelatin gels has been investigated by measuring the specific optical rotation [α]_λ at λ = 436 nm. The helix content χ in the gels was derived by reference to the native collagen. Two types of thermal treatments have been applied: (a) cooling and heating at constant rates, and (b) quenching and annealing for long periods. Our results support the idea that the gels are non-equilibrium systems and exhibit thermal hysteresis. The kinetics of helix formation were analysed by the Avrami theory and compared to other techniques. The stability of the structures formed suggests the existence of several mechanisms of hydrogen bonding of the helices: disordered aggregation or partial collagen renaturation.     

治理明胶生产废水污染研究进展

本文参考文献38篇,详细论述了废水处理技术在明胶生产废水治理中的应用与发展。在分析明胶废水污染现状、废水水质特性的基础上,从混凝、生物处理、污泥处理、超滤膜处理、蛋白质回收、环境健康研究几个方面综述了迄今为止围绕明胶生产废水治理所开展的有关研究工作和治理技术。     

明胶等电点对明胶微球分散度影响的研究

以不同等电点的明胶为原料,用浊度分光光度法和毛细管等电点聚焦法测定了它们的等电点,用乳化法在归一化的介质酸碱度下制备了一系列微球,考察了明胶等电点对所制得微球的分散度的影响。结果表明,等电点越接近溶液pH值的明胶,制得的微球直径越小,分布越均匀,球形和流动性越好;等电点偏离溶液pH值越远的明胶,制得的微球直径越大,分布越不均匀,球形和流动性越差。因此,乳化法制备明胶微球时应该把溶液pH值调至尽可能接近所用明胶的等电点值。这是微球设计和制备必须遵循的一条重要准则。     

明胶微球载药及其体外释放性能研究

以阿司匹林为药物模型分子,制备了载阿司匹林明胶微球。SEM研究表明,明胶微球在载药后,表面结构变得更为紧实。载药性能探讨表明,当阿司匹林的投药量为16mg时,明胶微球的载药性能较优（载药量为7．3％,包封率为57．5％）。对明胶微球在人工体液中的释药性能研究显示,载阿司匹林明胶微球具有良好的缓释性能。由于具有较大的酸性和胃蛋白酶的存在,微球在人工胃液中药物释放效率较高,在人工胃液和人工肠液中药物的释放率分别为40％和28％,且一级动力学模型对微球的体外药物释放情况拟合度较高。     

Mechanical properties with respect to water content of gelatin films in glassy state

Changes on the structural and molecular level of gelatin films induced by hydration below 25±3% water content (glass–rubbery transition at ambient temperature) were identified with DSC and FTIR spectroscopy. Three main stages of hydration were distinguished: (I) water bound by high-energy sorption centres; (II) structural water; (III) polymolecular layer water. The mechanical behaviour of gelatin films at each stage of hydration was characterized. Relaxation of the films during hydration was taken into account in the analysis of results. Hydrated gelatin films were characterized as brittle below the glass–rubbery transition at ambient temperature, however some improvement of mechanical properties related to a higher renaturation level was showed between 7 and 14% of water content in stage II (structural water).     

Effects of gelatin addition on the microstructure of freeze-cast porous hydroxyapatite ceramics

Porous hydroxyapatite (HAP) ceramics was prepared by freeze casting and gelatin was used to adjust the pore morphology and microstructure of the porous HAP ceramics. With the gelatin concentration increase, the viscosity of HAP slurry was increased, and the linear shrinkage ratio of the specimen sintered at 1300 °C was also increased. The gelatin addition had great effects on the pore size and pore morphology of the porous HAP ceramics. The experimental results showed that the pore morphology of HAP ceramics was changed from a two-dimensional flat pore to a three-dimensional reticulated pore after gelatin addition.     

Effect of polyols on the molecular organization and thermodynamic properties of low water content gelatin oligomers

We use Positron Annihilation Lifetime Spectroscopy (PALS) in conjunction with calorimetric measurements to investigate the effects of two polyols (sorbitol and glycerol) and water on the molecular packing and thermodynamic state of low water content gelatin matrices. Our calorimetric measurements show that water, sorbitol and glycerol all reduce the glass transition and dissociation/denaturation temperatures of the gelatin matrices. Glycerol has a more pronounced effect on the thermodynamic state of the matrices compared to sorbitol, while both polyols alter the molecular organization and water sorption behaviour in a similar way, despite the large differences in molecular weight. Our PALS measurements show that over the concentration ranges studied, both sorbitol and glycerol act as packing enhancers, causing similar reductions in the average hole size, v_h, of the gelatin matrices. Finally, we observe complex changes in v_h as a function of increasing level of hydration, showing two apparent regimes related to the state of water molecules in the gelatin matrices.     

海藻酸钠/明胶混合水溶液的流变性能

借助旋转黏度计考察了海藻酸钠/明胶混合水溶液的流变性能,发现混合溶液具有剪切变稀的非牛顿假塑性流体特征;随体系中明胶含量的增加,相应混合溶液的稠度系数增大而黏性指数下降,同时溶液的触变性能得以增强,该混合溶液体系具有协同增效性。     

Ultimate tensile measurements of filled gelatin gels

Ultimate tensile measurements were performed on the model system of glass filled gelatin gels. By using a range of sizes of glass ballotini, and also shape sorted fragments of fractured ballotini (denoted ‘cubes’) at varying phase volume of filler, the effect of size, shape and phase volume on the ultimate tensile properties of the filled gel samples was investigated. By constructing a force-extension failure envelope, a relationship was developed which enabled all the fracture data for the samples to be simply related, and this empirical relation was within experimental error identical to previously derived theoretical treatments of the dependence of small deformation modulus on phase volume.     

Thermal stability of gelatin gels: Effect of preparation conditions on the activation energy barrier to melting

10, 20, and 40 wt.% aqueous gelatin gels were prepared under isothermal (annealing at 15, 20, and 25 °C for 15 to 120 min) and nonisothermal (cooling at 1 °C min⁻¹) conditions. Isoconversional kinetic analysis of DSC data on gel melting (gel-sol transition) of all types of gels revealed significant variations in the activation energy throughout the process. Activation energy barrier to melting of isothermally prepared gels was in the range 160-190 kJ mol⁻¹ and found to increase with increasing the annealing temperature that was the major effect discovered. Activation energy barrier to melting of nonisothermally prepared gels was determined to be around 120-140 kJ mol⁻¹ and increase with increasing the concentration. Local reversibility of the gel melting was demonstrated by using temperature modulated DSC.     

Gold flails by electrochemical deposition: The role of gelatin

In this paper, we report on novel flail-like gold architectures obtained by a simple and template-free electrochemical method. The addition of gelatin plays a major role in the fabrication of this original structure and might open new possibilities for electrochemical deposition of other metals. The size of the flail-like gold structures can be varied very precisely from 250 nm to 8.5 μm by controlling the electrodeposition time. Importantly, as a preliminary application, such flail-like gold structures show a strong SERS effect associated with their geometry and size.     

Self-assembly and metal ions-assisted one step fabrication of recoverable gelatin hydrogel with high mechanical strength

ABSTRACT

Gelatin hydrogel has been widely applied in bio-applications due to their good biocompatibility and high water content. However, poor mechanical properties of gelatin hydrogel greatly limit their application. Here we present a facile one-step soaking method to fabricate a recoverable gelatin hydrogel with high mechanical property, which is based on hydrogen bonds and metal ionic interaction. The mechanical properties of gelatin hydrogels can be tuned with different metal ions, temperatures and soaking times. Especially, gelatin-Fe³⁺ hydrogel can reach to 65 MPa compression stress with the compressive strain over 99% and possess good fatigue resistance under cyclic loadings. Besides, hydrogels crosslinked with metal ions show better antibacterial ability against Escherichia coli and Staphylococcus aureus. This work suggested an alternative for the design of tough gelatin-based hydrogels with desirable properties, which may hold promising for potential bio-applications under physiological conditions.