Papers by Keyword: Lyophilization

Abstract: In this study, biodegradable scaffolds based on hydroxyethyl cellulose (HEC) (5 wt%) and poly (vinyl alcohol) (PVA) (15 wt%) with different percentages of celullose nanocrystal (CNC) (1 and 7 wt%) were fabricated by lyophilization method to get highly porous scaffolds. These scaffolds were made water insoluble by cross-linking via heat treatment. The morphology and thermal properties of HEC/PVA/CNCs scaffolds were characterized by using Scanning Electron Microscope (SEM) and Thermogravimetric Analysis (TGA). The morphological study showed that both prepared scaffold have highly porous structures with good pore interconnected structure. It was observed that thermal properties of scaffolds increased significantly as the concentration of CNCs increased. Cytotoxicity studies on scaffolds were carried out by utilizing human fetal osteoblast (hFOB) cells using DAPI nuclear stain and then confirmed using SEM. hFOB cells were able to attach and spread on all scaffolds. Incorporated CNCs as reinforcing nanofiller on scaffolds promising a superior functionality in bone tissue engineering.

Abstract: Tissue engineering (TE) is a modern medical approach to reconstruct damage tissue in a shorter period. Scaffold is the main structure for cells adhesion and provides 3D space for cell proliferation and growth. Biomaterials were selected to fabricate a scaffold according to properties and target tissues. In this study, Hydroxyapatite (HA), Silk Fibroin (SF), and Chitosan (CS) were selected to fabricate the scaffold in different combination ratios by freeze drying (FD) technique. According to the physical properties of the fabricated scaffold, cartilage tissue was selected as a study target area for the future medical application. Scaffold characterization was performed to observe the scaffolds properties in each materials ratio. In this study, CS scaffold provided highest abilities which related to cartilage tissue structure. Moreover, the combination of SF in CS provided highest ability for cartilage cell proliferation in vitro. Therefore, CS could be used as a cartilage scaffold for cartilage TE and SF could be added to increased the cells viability of the scaffold.

Abstract: The process of adding soy lecithin to milk (lecithination), followed by the agglomeration stage and drying, are the goal to increase the powder dispersion in water. This work studies the physical characteristics of milk lecithinated by the addition of raw and clarified lecithins with hydrogen peroxide, which was dried by lyophilization. The main objective was to compare the behavior between the particles of powdered milk, added 0.4% (w/v), 0.8% (w/v) and 1.0% (w/v) lecithin raw and clarified. The amount of added soy lecithin was determined on the basis of dry matter content of the full UHT milk used in the experiment. Lecithinated of fluid milk samples were put on aluminum forms and frozen by contact with liquid nitrogen and were placed inside the lyophilizer chamber. The lyophilization stage was carried out for approximately 7 hours under vacuum of 460 mmHg and temperature of -38 ° C. Dried samples were fragmented in porcelain pestle and kept in oven at 40°C until analyses. The powder milk added with lecithin clarified had shorter wettability to the concentration of 1.0% (w/v), the lowest percentage of retained insoluble after solubilization in water and the micrographs of the powder showed that most adding more clarified formed lecithin agglomerates of the milk powder added lecithin raw. So, the lecithin clarified give improvements in the particles for the milk added.

Abstract: This study reports the effects of the mixing ratio of hydroxyapatite (HA), silk fibroin (SF) and chitosan (CS) on the physical properties of the scaffold used in tissue engineering. Experimental design based on mixture design was implemented to investigate the degradation rate of the scaffolds fabricated from various ratios of those biomaterials. Furthermore, pore morphology and pore size were evaluated to confirm the compatibility of the scaffold topography for cell growth and adhesion. The results from the study showed that all ratios, except pure HA solution, can be fabricated into porous scaffolds with an interconnected pore structure and appropriate pore sizes to allow all types of human cells to pass through. Furthermore, the scaffold solutions with high CS ratio resulted in a uniform pore structure and lower rates of biodegradation. Therefore, CS is recommended as the main structure because it provides the highest resistance to biodegradation. The scaffolds from various ratios may be applied for different tissue replacements in the near future.

Abstract: Highly porous silica ceramics were prepared by in-situ gelation of an aqueous suspension with well dispersed silica particles and N’N-dimethylacrylamide (DMAA) monomer, followed by lyophilization and pressureless sintering. The gelcasting process was imparted by polymerization of DMAA. The silica raw materials used in this experiment are the dusts collected from the exhaust fumes of silicon industry. The as-obtained porous silica ceramics had three-dimensional and hierarchical pore structure and the porosity ranged from 75 to 88 % as the sintering temperature varied from 850 to 1050 °C. In addition, the porous silica ceramics appeared to have strong mechanical strength. Compressive strength of the porous silica ceramics was as high as 3.2 MPa even when the porosity was nearly 80%. The gelcasting-lyophilization method was proved to be a novel and promising route for the preparation of highly porous and mechanically strong materials.

Abstract: A study was conducted to determine the most optimal preservation technique for P. sajor-caju spawns which produce maximum specific growth rate and shortest doubling time by using contois kinetic model. The analyzed experimental data showed that lyophilized P. sajor-caju spawn showed the highest maximum specific growth rate, and shortest doubling time compared to cryopreserved P. sajor-caju spawn and 4oC stored P. spawn. There was no significant difference in aspect of growth rate between the lyophilization and cryopreservation techniques which were; 0.148 (μ_max)/ (g/day) and 0.147(μ_max)/ (g/day) respectively. Based on the result, lyophilization technique was considered as the best preservation technique for preserving P. sajor-caju spawn due to high maximum growth rate which indicates high survival after exposure to preservation treatment.

Abstract: The aim of the present work was to optimize the formula of cryoprotectants for freeze drying process of the previous selected Bifidobacterium animailis subsp.lactis Qq08 (Bl Qq08). Single factor and orthogonal experiments were conducted to optimize the cryoprotectants formula. The formula of cryoprotectants was optimized as follows: skim milk 15%, lactose 8%, Vc 1.5% and glycerol 3%. In the triplicate lyophilization tests, the average survival rate of Bl Qq08 reached 91.23%.The optimized formula of cryoprotectants was suitable for freeze drying of the Bl Qq08.

Abstract: A new method to fabricate porous chitosan nerve conduits with multi-channels was described. A uniquely designed mold was composed of 7-50 stainless steel needles and a set of plastic pedestals. Porous or imperforate chitosan tubes with 2-5mm inner diameter and 0.2-1.0 mm wall thickness were made firstly. The chitosan tubes were injected with 3% chitosan gel. The stainless steel needles longitudinally perforated through the chitosan tubes filled with chitosan gel, and the plastic pedestals were used to fix the needles. Lyophilization was used to finish fabrication. The diameter of channels was 0.2-0.4mm. Swelling property and biodegradability of Multi-channeled chitosan conduits were investigated. Wright’s staining and scanning electron microscope (SEM) were used to observe spread and proliferation of Neuroblastoma cells (N2A, mouse) on the conduits. It is promising that the porous chitosan nerve conduits with multi-channels are used as nerve tissue engineering scaffolds in repair of peripheral nerve and spinal cord injuries.