• Journal of Life Science
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• v.18 no.4
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• pp.542-549
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• 2008

Cisplatin (cis-diamminedichloroplatinum II : CDDP) is the most widely used anticancer drug against a variety of human neoplasms. However, its clinical use is limited by the onset of severe side effects, including ototoxicity and nephrotoxicity. Even though a number of evidences in cytotoxic mechanism of cisplatin have been suggested, the role of pro-inflammatory cytokines in cisplatin cytotoxicity of auditory cells has not yet been demonstrated. Herein our data clearly demonstrated that cisplatin decreased the viability of HEI-OC1 auditory cells, which was inhibited by the addition of neutralizing $anti-TNF-{\alpha}$, $anti-IL-1{\beta}$ and anti-IL-6 antibodies. Consistently, Neutralization with antibodies against pro-inflammatory cytokines ameliorated the cell death and disarrangement of cochlea hair cell layers in the rat primary cochlear explants which were treated with cisplatin. Furthermore, exogeneous supplementation with free radical scavengers, including GSH and NAC, significantly prevented the cytotoxicity of cisplatin in the rat primary cochlea explants. We also observed that $TNF-{\alpha}$ was predominantly expressed in Deiters and Hensen's cells located in hair cell zone of cisplatin-treated cochlear explants. These findings suggest that pro-inflammatory cytokines, including $TNF-{\alpha}$, $IL-1{\beta}$ and IL-6, may play a pivotal role in the pathophysiology of hair cell damages caused by ototoxic drug cisplatin.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.11
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• pp.1077-1082
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• 2007

We present a micromechanical active amplifier, inspired from the principle of the outer hair cells in cochlea, amplifying both displacement and force. The present micromechanical active amplifier modulates the resonant carrier motion using the variable stiffness spring whose stiffness changes proportionally to the input motion. We design, fabricate, and characterize two types of the amplifiers A and B, each having the variable stiffness spring fur the maximum displacement gain and force gain, respectively. In the experimental study, the amplifier A shows the displacement gain of 5.62, which is 2.15 times larger than that of the amplifier 3. The amplifier B shows the force gain of 10.0, resulting in 1.26 times larger value compared to that of the amplifier A. We experimentally verify that the haircell-inspired micromechanical amplifiers are capable to amplify both displacement and force.

• Journal of Biomedical Engineering Research
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• v.22 no.1
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• pp.91-99
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• 2001

청각기관에서 소리가 전달되어지는 과정에 대한 이론적인 전기/기계적 모델이 이루어진다면 이명환자의 분류 및 전기자극을 이용한 치료방법의 선택에 크게 기여할 수 있을 것이다. 본 연구에서는 기존 청각기관의 모델에 대한 장단점을 파악하여 이를 보완하는 실제의 시스템에 가장 근접한 모델을 수립하고, 청각시스템의 변화를 객관적으로 관찰할 수 있는 이론적인 배경을 수립하고자 하였다. 즉, 유모세포의 상면을 질량을 가진 성분으로 가정하고 그러한 질량의 경도와 제동을 위한 소자들을 첨가하여 새롭게 청각 모델을 수립하였다. 그리고 수립된 모델을 수학적으로 해석하여 전달함수의 영점이 극점보다 작게 나타남으로써 신경 조율 데이터를 이용한 기존의 연구와 일치함을 확인할 수 있었고, 제동주파수와 극점 주파수의 관계에 대한 가정들이 정당화됨을 확인할 수 있었다.

• Elastomers and Composites
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• v.44 no.2
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• pp.98-105
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• 2009

The cochlea of the inner ear has two core components, basilar membrane and hair cells. The basilar membrane disperses incoming sound waves by their frequencies. The hair cells are on the basilar membrane, and they are the sensory receptors generating bioelectric signals. In this paper, a biomimetic technology using ZnO piezoelectric nano-pillar was studied as the part of developing process for artificial cochlea and novel artificial mechanosensory system mimicking human auditory senses. In particular, ZnO piezoelectric nano-pillar was fabricated by both low and high temperature growth methods. ZnO piezoelectric nano-pillars were grown on solid (high temperature growth) and flexible (low temperature growth) substrates. The substrates were patterned prior to ZnO nano-pillar growth so that we can selectively grow ZnO nano-pillar on the substrates. A multi-physical simulation was also conducted to understand the behavior of ZnO nano-pillar. The simulation results show electric potential, von Mises stress, and deformation in the ZnO nano-pillar. Both the experimental and computational works help characterize and optimize ZnO nano-pillar.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.5
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• pp.522-528
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• 2011

Artificial basilar membranes made of PVDF(polyvinylidene fluoride) are manufactured using microfabrication processes. The mechanical behavior of PVDF artificial basilar membrane was measured to evaluate its performance as a mechanical frequency analyzer using scanning LDV(laser Doppler vibrometer). The experimental setup consists of the microfabricated artificial basilar membrane, a loud speaker connected to an amplifier for generating acoustic pressure of specific spectral pattern, and a scanning LDV with controlling unit for measuring the displacement of the membrane on the incoming acoustic stimulation. The microfabricated artificial basilar membrane was attached tightly upon a package containing a chamber which can be filled with silicone oil before placed on the experimental setup stage. The experiment results showed that the microfabricated artificial basilar membrane has a property as a mechanical frequency analyzer.