Molecular delivery using ultrasound (US) and nano/microbubbles (NBs), i.e., sonoporation, has applications in gene therapy and anticancer drug delivery. When NBs are destructed by ultrasound, the surrounding cells are exposed to mechanical impulsive forces generated by collapse of either the NBs or the cavitation bubbles created by the collapse of NBs. In the present study, experimental, theoretical and numerical analyses were performed to investigate cavitation bubbles mediated molecular delivery during sonoporation. Experimental observation using lipid NBs indicated that increasing US pressure increased uptake of fluorescent molecules, calcein (molecular weight: 622), into 293T human, and decreased survival fraction. Confocal microscopy revealed that calcein molecules were uniformly distributed throughout the some treated cells. Next, the cavitation bubble behavior was analyzed theoretically based on a spherical gas bubble dynamics. The impulse of the shock wave (i.e., the pressure integrated over time) generated by the collapse of a cavitation bubble was a dominant factor for exogenous molecules to enter into the cell membrane rather than bubble expansion. Molecular dynamics simulation revealed that the number of exogenous molecules delivered into the cell membrane increased with increasing the shock wave impulse. We concluded that the impulse of the shock wave generated by cavitation bubbles was one of important parameters for causing exogenous molecular uptake into living cells during sonoporation.

Keywords

Nanoparticles, Membrane Permeabilization, DDS, Fluorescence

Paper information

Tetsuya KODAMA, Yukio TOMITA, Yukiko WATANABE, Kenichiro KOSHIYAMA, Takeru YANO and Shigeo FUJIKAWA, “Cavitation Bubbles Mediated Molecular Delivery During Sonoporation”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 1 (2009), pp.124-140 . doi:10.1299/jbse.4.124

Over the last few decades several methods have been used to compute the propagation coefficient, which is a complex number that provides information about the viscoelastic properties of blood vessels. Results from these methods show a considerable disparity between them and when they are compared to theoretical values. Moreover, the attenuation and phase velocity obtained by the three-point method shows more significant discrepancies than those obtained by the other methods. In order to clarify the source of the disparity of results carried out by various methods concerning the estimation of phase velocity and attenuation in the arterial network, we made investigations using numerical tool several methods. We studied, for each method, the effects of distance between measurement sites, the sampling interval and measurement errors on the determination of the propagation coefficient by each of these methods. The values of wave speed and attenuation computed by these methods were compared to the known input values. Our simulation demonstrates that the distance between measurement sites and the sampling interval may introduce significant errors when the noise becomes high. Moreover the error on the values of attenuation and phase velocity obtained by occlusion and three-point methods is significantly higher than the error on the values obtained by RV-I and RV-II methods for all experimental conditions studied within the examined frequency range. This result supports the idea that the discrepancy between studies reported in literature seems to be due to the inaccuracy of experimental measurement techniques and not associated with the methods themselves as concluded by some authors.

Keywords

Propagation Coefficient, Numerical Simulation, Phase Velocity, Attenuation

Paper information

Khaled BEN ABDESSALEM, Saber BEN ABDESSALEM, Wasila SAHTOUT and Zouhaier FAKHFAKH, “The Influence of Experimental Condition on the Derivation of Propagation Coefficient in Arterials Systems: Numerical Investigation”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 1 (2009), pp.141-152 . doi:10.1299/jbse.4.141

The human forearm with elbow joint has two degrees of freedom of motion. Especially it is noticed that the wide range for the rotation of the forearm (pronation-supination) is attained according to the sophisticated complexity of the human forearm with elbow joint. The elucidation of its movement mechanism is useful for the functional evaluation for the medical treatment and application to the welfare devices for the upper limb. The purpose of this study is to develop the arm model that functionally mimics the musculoskeletal system of the human forearm with elbow joint. In this paper, we made a physical model and the computational models, which replicate the bionic function of the forearm with elbow joint. By estimating the moment arms in a physical model, the mobility of the simplified physical model was evaluated. In the three-dimensional computational forearm bone models different in the geometry, the beneficial property of the centroidal lines of the bones was confirmed to extend the range of motion for the pronation-supination.

Keywords

Biomechanics, Forearm, Elbow Joint, Musculoskeletal System

Paper information

Yu MORIWAKI, Nobuo SAKAI, Yoshinori SAWAE and Teruo MURAKAMI, “Development of Forearm Models Based on Human Musculoskeletal System”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 1 (2009), pp.153-164 . doi:10.1299/jbse.4.153