Simulation of blood flow in arteries with aneurysm: Lattice Boltzmann Approach (LBM).

BACKGROUND AND OBJECTIVE: In most countries, the higher death rates are due to cardiovascular disease and stroke. These problems often derive from irregular blood flow and the circulatory system disorder. METHODS: In this paper, the blood flow is simulated in a created aneurysm in the artery upon using Lattice Boltzmann Method (LBM). Blood is selected as a non-Newtonian fluid which was simulated with power-law model. The lattice Boltzmann results for non-Newtonian fluid flow with power-law model and the curved boundary are compared and validated with previous studies which show a good agreement. In this study, simulations are carried out for two types of aneurysms. For the first aneurysm, three power-law exponents of 0.6, 0.8 and 1.0 at Reynolds number of 100 for three different cases are investigated. RESULTS: The results show that the wall shear stress increases with increasing the power-law exponent. In addition, in the main duct of artery where the velocity is larger, shear stress is lower due to the smaller velocity gradient. For the second Aneurysm, the simulations are done for three Reynolds numbers of 100, 150 and 200, and three Womersley numbers of 4, 12 and 20. The blood flow is pulsating at the inlet such as the real pulsating wave in the blood. Results show that with increasing the Womersley number, the velocity profiles in the middle of the aneurysm are closer at a constant Reynolds number. CONCLUSIONS: With increasing the Reynolds number, the range of vortices and values of velocity and tension grow in the aneurysm.

Molecular dynamics simulation of Doxorubicin loading with N-isopropyl acrylamide carbon nanotube in a drug delivery system.

BACKGROUND AND OBJECTIVE: Doxorubicin is one of the common drugs used for cancer therapy. Molecular dynamics were applied to investigate the loading of Doxorubicin with thermosensitive N-isopropyl acrylamide Carbon nanotube carrier. METHODS: The results showed that the smaller polymer chain length has more decrease of gyration radius. A decrease of gyration radius resulted in more concentrated aggregation with stronger bonds. Therefore, the shorter the polymer chain lengths, the more stable polymer interaction and better Doxorubicin delivery. Smaller polymers also form more hydrogen bonds with the drug leading to stronger and more stable carriers. RESULTS: A lower amount of wall shear stress was found near the inner wall of the artery, distal to the plaque region (stenosis), and in both percentages of stenosis the maximum wall shear stress will accrue in the middle of the stenosis; however it is much more in the higher rate of stenosis. CONCLUSIONS: The results indicated that N-isopropyl acrylamide - Carbon nanotube is suitable for the delivery of Doxorubicin, and five mer N-isopropyl acrylamide is the optimum carrier for Doxorubicin loading.

pH-sensitive loading/releasing of doxorubicin using single-walled carbon nanotube and multi-walled carbon nanotube: A molecular dynamics study.

BACKGROUND AND OBJECTIVE: Doxorubicin is one of the drugs used to treat cancer, and many studies have been conducted to control its release. In this study, carbon nanotubes have been proposed as a doxorubicin carrier, and the effect of carboxyl functional group on the controlled release of doxorubicin has been studied. METHODS: This study has been done by molecular dynamics simulation and was based on changing the pH as a mechanism controller. RESULTS: This work is intended to test the efficacy of this drug carrier for the release of doxorubicin. A comparison was also made between single-walled and double-walled carbon nanotubes to answer the question of which one can be a better carrier for doxorubicin. The study of DOXORUBICIN adsorption and release showed that the DOXORUBICIN adsorption on single-walled carbon nanotube and multi-walled carbon nanotube in neutral pH was stronger than it was in acidic pH, which could be due to the electrostatic interactions between the carboxyl group of nanotubes and DOXORUBICIN. Based on this and according to the investigation of hydrogen bonds, diffusion coefficients, and other results it was clear that the drug release in acidic pH was appropriate for body conditions. Since cancer tissues pH is acidic, this shows the suitability of carbon nanotube in drug delivery and DOXORUBICIN release in cancer tissues. In addition, it was shown that the blood pH (pH = 7) is suitable for DOXORUBICIN loading on the carbon nanotube and carbon nanotube-DOXORUBICIN linkage remained stable at this pH; accordingly, the carbon nanotube could deliver DOXORUBICIN in blood quite well and release it in cancerous tissues. This suggests the carbon nanotubes as a promising drug carrier in the cancer therapy which can be also investigated in experiments. CONCLUSION: It was revealed that the bonds between multi-walled carbon nanotube and DOXORUBICIN was stronger and this complex had a slower release in the cancer tissues compared to the single-walled carbon nanotube; this can be regarded as an advantage over the single-walled carbon nanotube in the DOXORUBICIN delivery and release.

The effect of the second excitation frequency mode under different conditions on the fluid streaming and microparticles acoustophoresis with the aim of separating biological cells.

BACKGROUND AND OBJECTIVE: In this study, the effect of the second excitation frequency mode under different conditions on the fluid streaming and its microparticles displacement is investigated. METHODS: For this purpose, some variable parameters such as the particle diameter, microchannel aspect ratio, and applied frequency modes have been selected to study. The resulted acoustic streaming was scrutinized to understand the physics of the problem under different geometrical and input conditions. Finally, the effect of the increasing the microparticle size and aspect ratio of the microchannel, simultaneously, has been evaluated. RESULTS: The results demonstrated that increasing the microparticle size accelerates the displacement of the microparticles. On the other hand, changing the aspect ratio affects the formation of the microparticle distribution and it also changes the velocity of the microparticles due to the gradient of the second-order pressure. CONCLUSIONS: The obtained results have wide applications in the military, medical, petrochemical, and other related studies.