Study on thermophysical properties and effect of lyoprotectants in freezing human hepatoma Hep-G cells / 生物医学工程学杂志

Cell freeze-drying can be divided into the freezing and drying processes. Mechanical damage caused by ice crystals and damage from solute during freezing shall not be ignored and lyoprotectants are commonly used to reduce those damages on cells. In order to study the mechanism of lyoprotectants to protect cells and determine an optimal lyoprotectant formula, the thermophysical properties and percentage of unfrozen water of different lyoprotectants in freezing were investigated with differential scanning calorimeter (DSC). The survival rate indicated by trypan blue exclusion test and cell-attachment rate after 24 h using different lyoprotectants to freeze hepatoma Hep-G cells were measured after cell cryopreservation. The results show that 40% (W/V) PVP + 10% (V/V) glycerol + 15% (V/V) fetal bovine serum + 20% (W/V) trehalose formula of lyoprotectant demonstrate the best effect in protecting cells during freezing, for cell-attachment rate after 24 h is 44.56% ± 2.73%. In conclusion, the formula of lyoprotectant mentioned above can effectively protect cells.

Cyclic fatigue resistance, torsional resistance, and metallurgical characteristics of M3 Rotary and M3 Pro Gold NiTi files

OBJECTIVES: To evaluate the mechanical properties and metallurgical characteristics of the M3 Rotary and M3 Pro Gold files (United Dental). MATERIALS AND METHODS: One hundred and sixty new M3 Rotary and M3 Pro Gold files (sizes 20/0.04 and 25/0.04) were used. Torque and angle of rotation at failure (n = 20) were measured according to ISO 3630-1. Cyclic fatigue resistance was tested by measuring the number of cycles to failure in an artificial stainless steel canal (60° angle of curvature and a 5-mm radius). The metallurgical characteristics were investigated by differential scanning calorimetry. Data were analyzed using analysis of variance and the Student-Newman-Keuls test. RESULTS: Comparing the same size of the 2 different instruments, cyclic fatigue resistance was significantly higher in the M3 Pro Gold files than in the M3 Rotary files (p < 0.001). No significant difference was observed between the files in the maximum torque load, while a significantly higher angular rotation to fracture was observed for M3 Pro Gold (p < 0.05). In the DSC analysis, the M3 Pro Gold files showed one prominent peak on the heating curve and 2 prominent peaks on the cooling curve. In contrast, the M3 Rotary files showed 1 small peak on the heating curve and 1 small peak on the cooling curve. CONCLUSIONS: The M3 Pro Gold files showed greater flexibility and angular rotation than the M3 Rotary files, without decrement of their torque resistance. The superior flexibility of M3 Pro Gold files can be attributed to their martensite phase.

Study on formulation of liquid-solid compressed tablets of total triterpenoids from Sclerotii Poriae Cortex / 中草药

Objective: To improve the dissolution rate of total triterpenoids from Sclerotii Poriae Cortex. Central composite design response surface methodology was used to optimize formulation of liquid-solid compressed tablets. Methods: The types and ratio of excipients were determined by preliminary test and single factor experiments. Central composite design response surface methodology was used in the optimization of formulation, with dissolution rate as the index. Liquisolid compacts powders, crude drugs, and excipients were characterized by differential scanning calorimetry (DSC). Results: The best prescription was as follow: Liquid ratio was 1:1.67; R value was 18.25; Disintegrating agent was 8%; The ratio of PVPPXL-10 and CMSNa was 1.27 and the tablets hardness was 40-50 N. DSC showed that the characteristic peaks of drug in liquisolid tablets had vanished, and suggested that drugs might be present in liquid-solid compressed tablets as amorphous substance. Conclusion: The formulation of liquid-solid compressed tablet is reasonable. Liquisolid compacts can increase the dissolution rate of total triterpenoids from Sclerotii Poriae Cortex, and suggest that drugs may be present in liquid-solid compressed tablets as amorphous substance.

Rheological characterization of thermoplasticized injectable gutta percha and resilon / 대한치과보존학회지

OBJECTIVES: The purpose of this study was to observe the change in the viscoelastic properties of thermoplasticized injectable root canal filling materials as a function of temperature and to compare the handling characteristics of these materials. MATERIALS AND METHODS: Three commercial gutta perchas and Resilon (Pentron Clinical Technologies) in a pellet form were heated in the Obtura-II system (Obtura Spartan) at 140degrees C and 200degrees C, and the extrusion temperature of the thermoplasticized materials was measured. The viscoelastic properties of the materials as a function of temperature were evaluated using a rheometer. The elastic modulus G', viscous modulus G", loss tangent tandelta, and complex viscosity eta* were determined. The phase transition temperature was determined by both the rheometer and a differential scanning calorimeter (DSC). The consistency of the materials was compared under compacting pressure at 60degrees C and 40degrees C by a squeeze test. RESULTS: The three gutta perchas had dissimilar profiles in viscoelastic properties with varying temperature. The phase transition of softened materials into solidification occurred at 40degrees C to 50degrees C, and the onset temperatures obtained by a rheometer and a DSC were similar to each other. The onset temperature of phase transition and the consistency upon compaction pressure were different among the materials (p < 0.05). Resilon had a rheologically similar pattern to the gutta perchas, and was featured between high and low-flow gutta perchas. CONCLUSIONS: The rheological characteristics of the thermoplasticized root canal filling materials changed under a cooling process. The dissimilar viscoelastic properties among the materials require different handling characteristics during an injecting and compacting procedure.