four methods used for reducing restenosis; but the effects are not
ideal[3]. Among those methods, anticoagulants does not achieve high
local drug concentrations surrounding the stent. Radiation can easily
cause hemal brittleness, increasing the rate of cancer. At present,
gene therapy is still not a safe, effective and stable method for
enabling the objective gene to express in the target organs. The longterm
efficacy of drug-eluting stents has not yet been determined;
however, the risk of inducing thrombosis has already been proven[4].
Therefore, there is an urgent clinical need for establishing a method
that has a long-term efficacy and can conveniently, safely, and
efficiently inhibit intimal hyperplasia; as well as preventive methods
for vascular restenosis.
In recent years, it has been found that ultrasonic irradiation can
inhibit proliferation and promote vascular smooth muscle cell
apoptosis[5]. This method can be used for treating vascular restenosis,
which promises positive results in clinical practice. However, the
efficiency of inhibiting cells’ proliferation is rather low. Study of
Zhang et al revealed that cell apoptosis is only around 3%[6] after
ultrasonic irradiation. Consequently, researchers are studying the
effect of the combination of ultrasonic irradiation and microbubbles.
And it turned out that the combination method performed better
than using ultrasonic irradiation purely, which could led 20% cells’
apoptosis after s ultrasonic irradiation for 24 hour[7]. What’s more,
with the same irradiation frequency and intensity, different types of
microbubbles can have a direct impact on ultrasonic intervention,
which may be associated with the number of microbubbles, the
expansion size at a certain frequency and radiation intensity, and the
jets and shock waves that occurs when a bubble bursts. Atomic force
acoustic microscopy (AFAM) has been developed to observe the
morphology and internal information of a cell. AFAM can produce
high-resolution images by atomic force microscopy (AFM) and
provide a non-destructive imaging method by acoustic microscopy.
These features can help observe atomic force micrographs and
acoustic microscopy in situ, simultaneously. AFAM can obtain the
internal information of cells through acoustic waves at a nanometerlevel
resolution. Once the ultrafine images and elastic coefficients
of the same internal and surface areas are acquired, a 3D image of
the sample can be easily obtained. The elasticity information of cells
can also be observed by AFAM, which has become a powerful tool
for observing cell morphology. The research aims to observe the
morphological changes of vascular smooth muscle cells (A7r5 cells)
after ultrasound, and microbubble ultrasound irradiation by AFAM.
We hope to explain the effects of microbubbles on single vascular
smooth muscle cells and to explore the mechanisms of vascular
smooth muscle cell apoptosis. Providing experimental basis and
reference would be helpful in exploring the most suitable frequency
and microbubble dose for further studies.