Papers by Keyword: Freeze-Drying

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Authors: D. Sakloetsakun, S. Dünnhaupt, J. Barthelmes, W. Pfaller, A. Bernkop-Schnürch
Abstract: The scope of the study was to investigate the potential of thiolated chitosan as scaffold material for tissue engineering. Porous scaffolds were fabricated by freeze-drying method and stailized via disulfide bond formation. Characterizations were focused on morphological structure and degree of disulfide cross-linking. Renal proximal tubule epithelial cells (RPTECs) were used as model cell line. Chitosan-thioglycolic acid conjugate (chitosan-TGA) displayed 624.8 ± 21.2 and 1195.9 ± 61.0 µmol thiol groups/g polymer (chitosan-TGA 625 and chitosan-TGA 1196, respectively). After 4 days of incubation, the attachment of cells on the chitosan-TGA 625 and chitosan-TGA 1196 scaffolds were 101 ± 6.36 and 157.5 ± 2.82 cells/mm2, respectively. However, RPTECs did not grow on the unmodified chitosan scaffolds. These results confirm the potential utility of chitosan-TGA as a novel candidate being used as scaffold material in tissue engineering.
Authors: Fail R. Sultanov, Z.A. Mansurov, S.S. Pei, S.C. Chang, S. Xing, F. Robles-Hernandez, Y.W. Chi, K.P. Huang
Abstract: In this research aerogels were synthesized by homogenization of carbon nanotubes and chitosan under ultrasonic treatment and active magnetic stirring, followed by freeze-drying in order to remove the liquid from its structure. Freeze-drying is characterized by a certain ratio of pressure and temperature at which the solid phase, in our case - the ice, turns into a gas without passing through a liquid phase. Freeze-drying was carried out at a temperature of-5 ° C and a pressure of 30-80 Pa. After freeze-drying which lasted for 20 hours, the as-obtained aerogels were carbonized at temperature of 800 °C in an inert atmosphere. Surface morphology of resulting aerogels was studied using scanning electron microscopy. The hydrophobicity and sorption capacity of these aerogels to organic liquids characterized by different densities were investigated. In addition, composite aerogels with the presence of graphene layers in the structure were obtained and the influence of introduction of graphene on aerogel’s properties was analyzed. It was found that composite aerogels based on graphene and carbon nanotubes with chitosan as a glue matrix are characterized by a better-developed porosity of surface with a smaller pore sizes, and their sorption capacity for organic liquids is also higher compared with the aerogels based on carbon nanotubes.
Authors: Iulian Vasile Antoniac
Abstract: Composite materials based on collagen matrix could have the different properties in the case of reinforcement with different bioceramics. Not just the chemical composition of bioceramics used as reinforcement component have an influence on the composite properties, but also the microstructural aspects of bioceramics such as morphology, grain size and shape, homogeneity and distribution. We present in this paper the effect of the bioceramics type (TCP, hydroxyapatite) and ratio on the composite material structure and the biodegradation properties of some collagen based composites obtaining using the freeze-drying process. Also, we measure the porosity before made the biodegradation test using collagenase as medium and immersion in simulated body fluid in order to see the bioactivity properties.
Authors: Tao Lin, Xiang Chao Zhang
Abstract: Titanium dioxide thin film has been successfully synthesized deposited on ITO glass substrates by the sol–gel dip-coating method using freeze drying technique. The precursor and TiO2 film were characterized using XRD, AFM and UV-vis absorption spectra analysis technologies. The XRD result demonstrates that the TiO2 film is well crystallized and consists of anatase phase only with (101) plane. The morphology of the nanoparticles of TiO2 thin film is spherical shape with grain size of 30.1 nm in average diameter and the surface of the TiO2 film is smooth. There is a strong wide UV absorption band around 387 nm and the calculated band gap (Eg) value of the TiO2 thin film is about 3.18 eV. The water contact angles for the thin film was only about 12°. The freeze drying-assisted sol-gel technique offers a novel process route in treating hydrophilic glasses for self-cleaning building materials and would be widely application for building energy saving.
Authors: Conor T. Buckley, K.U. O’Kelly
Abstract: Tissue-engineering scaffold-based strategies have suffered from limited cell depth viability when cultured in vitro, with viable cells existing within the outer 250-500μm from the fluid-scaffold interface. This is primarily believed to be due to the lack of nutrient delivery into and waste removal from the inner regions of the scaffold construct. Other issues associated with porous scaffolds involve poor seeding efficiencies and limited cell penetration resulting in heterogeneous cellular distributions. This work focuses on the development a novel hydroxyapatite multi-domain porous scaffold architecture (i.e. a scaffold providing a discrete domain for cell occupancy and a separate domain for nutrient delivery) with the specific objectives of embodying in one scaffold the structures required to optimise cell seeding, cell proliferation and migration and potentially to facilitate vascularisation once implanted in vivo. This paper presents the development of the multidomain architecture and preliminary results on cell viability which show a significant improvement in cell viability in the scaffold interiors.
Authors: Chuan Jie Zhang, Liu Wang, Jin Chao Zhao, Ping Zhu
Abstract: Bacterial cellulose (BC) gelatinous films prepared in stationary culture were dried by three different drying methods: hot air drying, vacuum drying and vacuum freezing drying. The structure of dried bacterial cellulose films was characterized using scanning electron microscopy (SEM), infrared spectroscopy (IR) and X-ray diffraction (XRD), and mechanical properties were tested. The results showed that the surface of films prepared by hot air drying were uniform and dense, cavities and cracks configurations existed in vacuum dried films, and layer and porous structures were observed in vacuum freezing dried films. FTIR spectra and X-ray pattern confirmed that vacuum freezing drying reduced the strength of hydrogen bonds between cellulose macromolecules and the degree of crystallinity of BC films but had little influence on the crystal structure. For those reasons, mechanical properties of BC films prepared by vacuum freezing drying were lower than that of those films by other methods.
Authors: Kyung Sik Oh, Kwang Jin Kim, Young Keun Jeong, Yong Ho Choa
Authors: He Chen, Qiu Hong Zhang, Qian Luo, Guo Wei Shu
Abstract: effect of five materials including sucrose, lactose, skim milk, yeast, vitamin B2 on survival rate of Lactobacillus bulgaricus during freeze-drying was studied by measured survival and the number of viable cells. Designed different concentrations of these different protective agents, respectively, freeze-drying perfectly and then counted the survival ratio of Lactobacillus bulgaricus and the number of viable cells. Results were as follows: addition of skim milk and yeast had significant effects while addition of vitamin B2 had minimal impact on survival rate of Lactobacillus bulgaricus. The optimum concentration of single protective agent of Lactobacillus bulgaricus during freeze-drying was that 25% (W/V) sucrose, 20% (W/V) lactose, 25% (W/V) skim milk, 20% (W/V) yeast and 25% (W/V) vitamin B2, respectively, and survival rate was 24.5%, 35.6%, 64.4%, 62.2%, and 16.3%.
Authors: Qi Ma, Tao Qin, He Chen, Guo Wei Shu
Abstract: Effect of four materials including glycine, arginine, proline and sodium glutamate on survival of Bifidobacterium bifidum during freeze-drying was studied by measuring the viable counts of before and after freeze-drying. The addition of glycine, arginine, proline and sodium glutamate (%, w/v) were all 1.0%, 2.0%, 3.0%,4.0% and 5.0%. Results were as follows: addition of glycine, arginine, proline and sodium glutamate into B. bifidum paste could significantly improve the survival rate of B. bifidum and the number of viable cells of lyophilized powder. The optimal concentrations of glycine, arginine, proline and sodium glutamate were 4.0%, 4.0%, 3.0% and 2.0%, the survival of B. bifidum was 87.49%, 84.28%, 67.50% and 69.01%, respectively.
Authors: Tao Qin, Qi Ma, He Chen, Guo Wei Shu
Abstract: Effect of four materials including trehalose, soluble starch, raffinose and galactose on survival of Lactobacillus acidophilus was studied by counting viable cells before and after freeze-drying. The concentrations of five carbohydrates were all 3%, 6%, 9%, 12% and 15%. Results showed as follows: the optimal concentrations of trehalose, soluble starch, raffinose and galactose were 12%, 9%, 3% and 15%, the survival of Lactobacillus acidophilus was 42.62%, 56.50%, 45.05% and 42.69% and the viable cells of lyophilized powder were 0.40×1011cfu/g,0.45×1011cfu/g, 0.52×1011 and 1.09×1011cfu/g, respectively.
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