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Objective To investigate the correlation between mechanical properties and hemostatic ability of the sealing hydrogels. Methods The gelation time, elastic modulus, viscous modulus, bursting strength and hemostatic ability of the hyaluronic acid/gelatin hydrogels were measured. Compared with fibrin sealant, gelation time and mechanical parameters were proposed to judge the feasibility of sealing hydrogels to be used for hemostasis in clinic. Results Hydrogels with a long gelation time, low elastic modulus, low viscous modulus and small bursting strength were merely suitable for hemostasis in minor bleeding. The hydrogels with short gelation time, high elastic and viscous modulus and large bursting strength could effectively reduce the blood loss in the cases of massive bleeding. Conclusions The hemostatic ability of a hydrogel was correlated to its gelation time, elastic modulus, viscous modulus and bursting strength. To achieve hemostasis as effective as fibrin sealant, the gelation time of a sealing hydrogel should be less than 120 s, its elastic and viscous modulus should exceed 600 Pa and 120 Pa, respectively. For the damage with diameter of 2 mm in the tissue model, the burst strength should exceed 10.7 kPa and preferably be larger than 16.0 kPa.
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The rheological properties of six compound gels that consists of kappa carrageenan (KC) and another excipient such as konjac gum were explored through comparison of their viscosity measured by the rotation method. The gel fluid type was dependent on the rheological curve fitted by the power-law equation. The effect of concentration on the viscosity of different compound gels was investigated by establishing the linear equation between their viscosity and concentration, the slope of which was used to determine the relation between viscosity and concentration of different compound gels. The viscous flow activation energy (Eη) was calculated by the Arrhenius equation, which was able to investigate the effect of temperature on their viscosity. The interaction between monomer and compound gels was also studied by measuring their viscosity. The results showed that six compound gels were pseudoplastic fluid. Among all compound gels, the KC-xanthan gum (KC-XG) solution exhibited the most obvious shear thinning, the strongest pseudoplasticity, while the smallest Eη, resulting in the best thermal stability of viscosity. Furthermore, the concentration of KC-sodium hyaluronate (KC-HA-Na) solution affected its viscosity significantly. The viscosity of six compound gels was greater than the summation of the two kinds of monomer gels, which suggests that there is a synergistic-viscosity interaction between KC and another excipient.
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OBJECTIVE: To investigate the rheological property of Kappa carrageenan and the effects of standing time, concentration, and temperature on the viscosity of carrageenan solution. METHODS: The fluid type was determined by fitting the rheological profiles to Power law model. The effect of temperature on the rheological behavior was investigated according to the viscous flowactivation energy(Eη) which was calculated by the Arrhenius formula. RESULTS: The viscosity of carrageenan solution decreased with the increase of shear rate and temperature, whereas it increased with the concentration. There existed a positive correlation between Eη and concentration. Furthermore, the effects of different cations on the viscosity were also studied and the results indicated that the viscosity increased significantly with the ionic concentration, especially that of potassium chloride. CONCLUSION: Carrageenan was inferred to be pseudo-plastic fluid which hasthe character of shear thinning effect and its viscosity is significantly affected by cationic species.
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OBJECTIVE: To prepare crossed-linked sodium hyaluronate (CHA) gel and study its rheological property. METHODS: CHA was prepared using 1, 4-butanediol diglycidyl ether (BDDE). The linear viscoelastic properties and creep recovery of hyalouronan(HA) and CHA were measured with a rheometer. The influencing factors of rheological properties were analyzed, such as concentration, proportion of cross-linker and temperature. RESULTS: Cross-linked sodium hyaluronate gel was prepared. The viscoelasticity was measured with a pair of 20 mm stainless steel plates at the frequency of 1 Hz and shear-strain of 1 Pa at (25±0.1)℃. As shown by the creep recovery test, CHA had a smaller strain and shorter time to recover to the minimum strain than HA, which showed typical linear viscoelastic and creep recovery properties. CONCLUSION: CHA is a non-Newtonian fluid, which is easy to administer and conforms completely to the requirements for viscoelastic supplementation materials for intra-articular injection. Compared with HA, CHA has more advantageous viscoelastic property and stability.
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The aim of this study was to develop a method for measuring the slumping resistance of flowable resin composites and to evaluate the efficacy using rheological methodology. Five commercial flowable composites (Aelitefil flow:AF, Filtek flow:FF, DenFil flow:DF, Tetric flow:TF and Revolution:RV) were used. Same volume of composites in a syringe was extruded on a glass slide using a custom-made loading device. The resin composites were allowed to slump for 10 seconds at 25degrees C and light cured. The aspect ratio (height/diameter) of cone or dome shaped specimen was measured for estimating the slumping tendency of composites. The complex viscosity of each composite was measured by a dynamic oscillatory shear test as a function of angular frequency using a rheometer. To compare the slumping tendency of composites, one way-ANOVA and Turkey's post hoc test was performed for the aspect ratio at 95% confidence level. Regression analysis was performed to investigate the relationship between the complex viscosity and the aspect ratio. The results were as follows. 1. Slumping tendency based on the aspect ratio varied among the five materials (AF < FF < DF < TF < RV). 2. Flowable composites exhibited pseudoplasticity in which the complex viscosity decreased with increasing frequency (shear rate). AF was the most significant, RV the least. 3. The slumping tendency was strongly related with the complex viscosity. Slumping resistance increased with increasing the complex viscosity. The slumping tendency could be quantified by measuring the aspect ratio of slumped flowable composites. This method may be applicable to evaluate the clinical handling characteristics of flowable composites.