Biomedical subjects

Kuo-Kang Liu

Publications and source records attributed to Kuo-Kang Liu.

7 recordsLinked to original sources

PubMed2006

The deformation of an erythrocyte under the radiation pressure by optical stretch.

In this paper, the mechanical properties of erythrocytes were studied numerically based upon the mechanical model originally developed by Pamplona and Calladine (ASME J. Biomech. Eng., 115, p. 149, 1993) for liposomes. The case under study is the erythrocyte stretched by a pair of laser beams in opposite directions within buffer solutions. The study aims to elucidate the effect of radiation pressure from the optical laser because up to now little is known about its influence on the cell deformation. Following an earlier study by Guck et al. (Phys. Rev. Lett., 84, p. 5451, 2000; Biophys. J., 81, p. 767, 2001), the empirical results of the radiation pressure were introduced and imposed on the cell surface to simulate the real experimental situation. In addition, an algorithm is specially designed to implement the simulation. For better understanding of the radiation pressure on the cell deformation, a large number of simulations were conducted for different properties of cell membrane. Results are first discussed parametrically and then evaluated by comparing with the experimental data reported by Guck et al. An optimization approach through minimizing the errors between experimental and numerical data is used to determine the optimal values of membrane properties. The results showed that an average shear stiffness around 4.611x10-6 Nm(-1), when the nondimensional ratio of shear modulus to bending modulus ranges from 10 to 300. These values are in a good agreement with those reported in literature.

Cell Size↗

PubMed2005

Characterizing the viscoelastic properties of thin hydrogel-based constructs for tissue engineering applications.

We present a novel indentation method for characterizing the viscoelastic properties of alginate and agarose hydrogel based constructs, which are often used as a model system of soft biological tissues. A sensitive long working distance microscope was used for measuring the time-dependent deformation of the thin circular hydrogel membranes under a constant load. The deformation of the constructs was measured laterally. The elastic modulus as a function of time can be determined by a large deformation theory based on Mooney-Rivlin elasticity. A viscoelastic theory, Zener model, was applied to correlate the time-dependent deformation of the constructs with various gel concentrations, and the creep parameters can therefore be quantitatively estimated. The value of Young's modulus was shown to increase in proportion with gel concentration. This finding is consistent with other publications. Our results also showed the great capability of using the technique to measure gels with incorporated corneal stromal cells. This study demonstrates a novel and convenient technique to measure mechanical properties of hydrogel in a non-destructive, online and real-time fashion. Thus this novel technique can become a valuable tool for soft tissue engineering.

Biocompatible Materials↗

PubMed2005

Coupling bending and shear effects on liposome deformation.

Cell membrane deformation induced by external mechanical stimuli has been studied extensively over the past three decades. The present study focuses on the coupling of in-plane shear H and out-of-plane bending B of liposome membrane and its influences on the deformation of a single vesicle subjected to (i) external compressive load via two parallel platens and (ii) contact forces caused by a rigid substrate. Our results show that the increase of membrane resultant stress in both loading configurations causes the liposome to become more rigid and the degree of vesicle deformation decreases when the in-plane shearing effect is dominant. A theoretical approach is developed to facilitate cell membrane characterization under different biomechanical stimuli.

Animals↗

PubMed2004

Bioadhesive characterization of poly(methylidene malonate 2.12) microparticle on model extracellular matrix.

The efficacy of a drug delivery system is predicated on its retention in the target tissue. Microparticle is one of the most popular and effective drug delivery configurations. Recently, it has been shown that the interaction between drug-loaded microparticles and tissues is related to the effectiveness of paclitaxel delivery to the bladder wall of mice for treating superficial bladder cancer. In this study, the adhesive interaction between poly(methylidene malonate 2.12) or PMM 2.1.2 microparticles and collagen, which serves as the model extracellular matrix for bladder wall, was probed with confocal reflectance interference contrast microscopy (C-RICM), single-particle compressive force measurement and contact mechanics theory. Young's modulus of single PMM 2.1.2 microparticle was determined as 1.56 +/- 0.25 x 10(4)N/m(2). For plain PMM 2.1.2 microparticle in water (pH 5.5), the degree of deformation (a/R) on collagen coated substrate decreased from 0.77 to 0.26 against the increase of mid-plane diameter from 2 to 18 microm. The adhesion energy of PMM 2.1.2 microparticle was determined from Maguis-JKR theory and remained at around 1.5 mJ/m(2) against the increase of particle diameter. At pH 4, the average degree of particle deformation and adhesion energy was increased by 11% and 32%, respectively, in comparison with that at pH 5.5. The loading of paclitaxel in PMM 2.1.2 microspheres enhanced the deformation and adhesion of microspheres at pH 5.5. It is hypothesized that the electrostatic repulsion between paclitaxel and collagen at pH 4 reduces the adhesion energy of PMM 2.1.2-paclitaxel microsphere. This study may offer insight for design of future microparticulate delivery systems by providing the experimental and theoretical tools to study the bioadhesive interaction between drug-loaded microparticles and model extracellular matrices.

Adhesiveness↗

PubMed2004

Shape recovery of an optically trapped vesicle: effect of flow velocity and temperature.

A new biophysical approach based on optical tweezers is developed to measure the time-dependent shape transformation and recovery of a single liposome, which is induced by the sudden stop of a moving liposome from various flow velocities at constant temperature. A simple viscoelastic model has been applied to correlate the temporal geometric parameter of the deformed liposome with a characteristic time constant, i.e., the ratio of membrane viscosity to elasticity. Our results show that membrane viscosity becomes dominant in governing the shape recovery rate when sample temperature goes beyond the main phase transition temperature of the phospholipid bilayer. More importantly, flow speed and vesicle size are demonstrated as key physical determinants for the shape recovery of liposome.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2003

Thermal effect on a viscously deformed liposome in a laser trap.

The viscous drag and mechanical deformation of a single vesicle under hydrodynamics flow during the phase transition of a lipid bilayer is determined by optical tweezers experiments with the aid of computational fluid dynamics simulations. Based on the experimental geometry of the vesicle under hydrodynamics flow, the surface stresses and drag force are numerically calculated. It is found that the vesicle is less rigid and the viscous drag force of the vesicle decreases with the increase of temperature at low Reynolds number flow during sample heating. Interestingly, these mechanical properties are reversible and depend strongly on the liposome's thermotropic phase transition temperature. Overall, this study provides new insights into highly coupled thermal and hydrodynamics effects on the biomechanical properties of model membrane vesicle in physiological flow systems.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2003

Contact deformation of liposome in the presence of osmosis.

The role of osmotic pressure on the geometry of adherent liposome remains an intricate question in the mechanics of supramolecular structures. In this study, confocal reflection interference contrast microscopy in combination with cross-polarized microscopy was applied to probe the geometry of deformed liposome on fused silica substrates through the determination of a vesicle-substrate separation profile. In parallel, a theoretical model which describes the large deformation of the lipid bilayer membrane under both out-plane bending and in-plane shear forces is developed. Then, the global deformation geometry of the adherent liposome is rigorously compared with our experimental data. It is shown that the adhesion contact area increases in dimension, the liposome volume decreases, and the vesicle height decreases under the reduced osmotic pressure. The coupling of experimental data and a modified theoretical framework of the adherent liposome provides a more explicit result in comparison with previous studies and demonstrates the possibility of modeling the change of liposome mechanics under the influence of osmosis.

Adsorption↗