Shock Dynamic Study of Laser Ablation Induced Drug Delivery

在东北大学跨学科冲击波研究中心，我们的目标是将冲击波现象应用于医学。我们已经完成了体外冲击波碎石术，目前正在努力开发脑血栓血运重建系统，预计在不久的将来就能完成。在这些话题中，冲击波总是扮演着重要的角色。当调Q激光将一个光斑聚焦在金属箔表面时，一个等离子体云瞬间从该光斑射出，并作为反应在金属箔内部产生冲击波，该冲击波从另一个表面传播和反射。等离子体的形成被称为激光烧蚀。反射波膨胀后，铝箔以2~5公里/S的速度瞬间膨胀，当小颗粒附着在金属表面时，这些小颗粒会在激光照射的瞬间以如此高的速度被喷射出来。这一原理已应用于加速干式…更多的药物颗粒或金属颗粒*大约一微米量级进入人体组织。我们用调Q的Nd：YAG激光聚焦在一块5 mm厚的玻璃板上，在0.1 mm厚的铝箔上附着着钨或金颗粒。我们测量了粒子抛射速度为1~2公里/S的数量级，将这些粒子注入琼脂细胞、小鼠肝脏和小鼠皮肤，测量了它们的穿透深度，发现每种材料的最大穿透深度约为6 mm。这种小颗粒的自由飞行属于高超声速Stokes流，在现场气体动力学中从来没有认真讨论过。我们已经开发了数值方案来估计粒子的自由飞行以及对软组织的渗透。我们用这种方法研究了液体溶液中钨对细胞的渗透，观察到一微米的钨颗粒漂亮地渗透到细胞中。在这些基础研究的基础上，我们得出结论，这种方法优于现有的机械式基因传递系统，并且非常坚固和紧凑，可以重新设计为一种治疗装置。我们相信我们已经实现了我们最初提出的主要目标。较少

In the Interdisciplinary Shock Wave Research Center, Tohoku University, we have aimed to apply the shock wave phenomena to medicine. We have already finished the extracorporeal shock wave lithotripsy and now are working for the development of system for revascularization of cerebral thrombosis, which is expected to be completed in very near future. In these topics a shock wave plays always an important role*. When a Q-switched laser beam focused a spot on a metal foil surface, instantaneously a plasma cloud ejected from the spot and as its reaction a shock wave is generated inside the metal foil which propagate and reflected from the other surface. The plasma formation is called laser ablation. The reflected wave an expansion one and as a result of it the foil is instantaneously bulged at 2 to 5 km/s. When small* particles are attached on the metal surface these would be ejected at such a high speed at the moment laser beam irradiation. This principle has been applied to accelerate dry … More drug particles or metal particles* of the order of magnitude of one micron or so into human tissue. We have used Q-switched Nd:YAG laser focused on the surface of a 5 mm thick glass plate backed up with 0.1 mm this aluminum foil on which tungsten or gold particles were attached. We measured the particle ejection speed to be in the order of magnitude of 1 to 2 km/s. Injecting these particles against agarose cell, mouse liver, and mouse skin, we measured penetration depths against these and found the maximum penetration depth was about 6 mm for individual materials. The free flight of such small particles belongs to hypersonic Stokes flow which has never be discussed seriously in the field gas dynamics. We have developed numerical scheme to estimate particle free flight as well as penetration into soft tissues. We have examined with this method the penetration into cell lines in liquid solution and observed a beautiful penetration of a one micron tungsten particle into a cell. Based on these basic studies we concluded that this method is superior to the existing mechanical gene delivery systems and so robust and compact that it can be redesigned as a therapeutic device. We believe we have accomplished our main goal which we proposed at first. Less