Ruey-Yug Tsay

A video‐enhanced plate method for simultaneous measurements of surface tension and contact angle

The assumption of zero contact angle of the Wilhelmy plate method causes error for the surface pressure‐area characteristics of some spread monolayers. To avoid this problem, a video‐enhanced plate method is developed to monitor the dynamic surface tension and contact angle simultaneously. According to this method, the profile of the air–water interface adjacent to a flat plate is captured by an image digitization technique. The surface tension and contact angle are obtained from the best fit between the edge coordinates of the captured image and a theoretical equation derived from the Young–Laplace equation. Preliminary results show satisfactory agreement between the curve of the air–water interface obtained from experimental data and the theoretical curve for obtained values of surface tension and contact angle. Twenty tests for pure water at 25 °C give an average surface tension 72.0±0.2 mN/m, which confirms the accuracy of this method. A preliminary dynamic test also indicates that the effect of the c...

Evaluation of decellularized extracellular matrix of skeletal muscle for tissue engineering

Objective We evaluated the effectiveness of enzyme-detergent methods on cell removal of mouse skeletal muscle tissue and assessed the biocompatibility of the decellularized tissues by an animal model. Methods The mouse latissimus dorsi (LD) muscles underwent decellularization with different enzyme-detergent mixtures (trypsin-Triton X-100, trypsin-sodium dodecyl sulfate (SDS), trypsin-Triton X-100-SDS). The effectiveness of decellularization was assessed by histology and DNA assay. The content in collagen and glycosaminoglycan was measured. The biomechanical property was evaluated in uniaxial tensile tests. For biocompatibility, the decellularized muscle specimens were implanted in situ and the tissue samples were retrieved at day 10, 20, and 30, to evaluate the host-graft inflammatory reaction. Results Extensive washing of the mouse LD muscles with an enzyme-detergent mixture (trypsin and Triton X-100) can yield an intact matrix devoid of cells, depleted of more than 93% nuclear component and exhibiting comparable biomechanical properties with native tissue. In addition, we observed increased infiltration of inflammatory cells into the scaffold initially, and the presence of M1 (CD68)-phenotype mononuclear cells 10 days after implantation, which decreased gradually until day 30. Conclusions The enzyme-detergent method can serve as an effective method for cell removal of mouse skeletal muscle. In short-term follow-up, the implanted scaffolds revealed mild inflammation with fibrotic tissue formation. The decellularized extracelluar matrix developed herein is shown to be feasible for further long-term study for detailed information about muscle regeneration, innervation, and angiogenesis in vivo.

Adsorption kinetics of soluble surfactants and the phase transition model. 1. Theoretical simulation

Surfactants with strong cohesion can have purely diffusive adsorption and mixed re-equilibration relaxations. This idea is illustrated in this study by theoretical simulations of the relaxation in surface tension due to adsorption onto an initially clean planar interface and re-equilibration of an interface containing a monolayer which has been perturbed. A phase transition model is utilized to describe the adsorption kinetics of soluble surfactants with strong intermolecular attractions between the adsorbed molecules. The cohesion forces lead to the formation of a surface liquid phase, raise the energy barrier for desorption of the adsorbed molecule into the bulk sublayer and correspondingly lower the desorption rate. Novel regions are identified where the surface tension relaxation for adsorption onto a clean interface is diffusion controlled, and that for re-equilibration is mixed. The effects of the bulk concentration, the cohesion energy, and the compression ratio are also reported. Within these regions, adsorption experiments can be done to measure the diffusion coefficient, and re-equilibration experiments can be used to obtain the sorption rate constants.

An investigation on the correlation between the mechanical property change and the alterations in composition and microstructure of a porcine vascular tissue underwent trypsin-based decellularization treatment

PURPOSE The nonlinear pseudoelastic behavior of a native/decellularized vascular tissue is closely related to the detailed composition and microstructure of the extracellular matrix and is important in maintaining the patency of a small-caliber vascular graft. A commonly used enzyme-detergent based decellularization protocol is effective in cell component removal but it also changes the microstructure and composition of the decellularized tissues. Previous studies provide limited information to correlate the mechanical property change with the alterations in composition and microstructure in a decellularization process. In this study, the correlations were studied by implementing a previously established fiber-progressive-engagement model to describe the nonlinear pseudoelastic behavior of a vascular tissue and to evaluate the effects of trypsin concentration and exposure duration on porcine coronary artery decellularization RESULTS: Results showed that tissue length and width increased and thickness and wet weight decreased with the exposure of trypsin. The effects of trypsin exposure times on the four mechanical parameters, i.e. initial strain, turning strain, initial modulus and stiffness modulus, in the longitudinal and circumferential directions were similar, but stronger in the circumferential direction. Major components of the extracellular matrix were vulnerable to the trypsin-based decellularization process. The decreases in initial and turning strain and the increase in initial modulus in circumferential direction were correlated with the significant decrease of collagen and glycosaminoglycans in the media layer. CONCLUSIONS Although trypsin-based decellularization achieved cell component removal and preservation of ultimate tensile stress, the microstructure and composition changed with alterations in the pseudoelastic behavior of the porcine coronary artery. Taken together, the current observations suggested less waviness, early engagement, or re-alignment of insoluble collagen fibers in the media layer, which resulted in turning from anisotropic into isotropic uniaxial mechanical property of porcine vascular tissue. Selecting the proper trypsin concentration (< 0.03-0.5%) and duration (< 12 h) of trypsin exposure in combination with other methods will achieve optimal porcine coronary artery decellularization.

The Effects of the Finite Dissolution Rate on the Drug Release of Spherical Particles Loaded with Uniformly Dispersed Drugs

Higuchi’s well known model, which has traditionally been applied to describe the release of non-swellable and non-erodible drug-loaded microspheres, neglects the effects of the finite drug dissolution rate and assumes that a depletion layer extending inward leaches drugs. Although many release models have amended Higuchi’s model, the effects of the finite dissolution rate are generally still ignored. This study takes the effects of the finite dissolution rate into account and proposes a more generalized drug release model. The numerical solution of the present generalized model was validated by its agreement with a short time analytical solution. The solution reveals that the dynamic curves showing the moving boundary of the depletion layer and the remaining drugs exhibit a sinusoidal shape of decrease with time. Results also indicate that due to the assumption of instantaneous dissolution, Higuchi’s model can be applied only when the ratio of diffusion rate/dissolution rate B is small. It is also found that in spite of the pseudo-steady state approximation, drug release curves predicted by Higuchi’s model for a drug loading ratio K as low as 1 are still close to the present results. This suggests that the significant difference between the present solution and Higuchi’s solution for a large K is mainly due to the effects of the finite dissolution rate.