臺灣博碩士論文加值系統

中文摘要
　　神經銬狀電極是一種被廣泛應用於神經義肢的微電極，它應用電刺激與神經訊號量測技術來恢復受損的周邊神經系統功能。當電極植入體內後，因生物分子與電極表面的作用，常造成電極阻抗上升使得電極效能不佳；我們應用微機電製程技術製造並測試新的多極式神經銬狀電極，電極由自我組成有機薄膜表面處理的微電極與聚亞醯胺基材所構成，經過處理的電極表面能在分子層級控制生物分子的沾黏附著，實驗中應用不同碳鍊長度的有機薄膜分子化學合成在電極表面來探討蛋白質吸附與細胞黏著現象。

　　在蛋白質吸附實驗中，自我組成有機薄膜在電極表面提供了一個疏水性的環境，可減緩蛋白質的初始吸附與後續堆疊，降低電極阻抗的上升，電極阻抗的改變主要是容抗所造成與蛋白質堆疊過程有關；表面處理能降低部分蛋白質在電極表面的吸附，此效應與薄膜分子碳鍊長度相關，在未處理金面上則緊密的吸附上蛋白質層。

　　在細胞黏著實驗中，自我組成有機薄膜增加了電極表面的水滴接觸角與初始電極阻抗，它提供了一個低離子強度的表面使得細胞無法完全的吸附黏著；為了探討液相環境裡的表面單細胞黏著力學，我們應用三角形懸臂樑的原子力顯微鏡探針，測試刮起細胞所需的力與工，結果顯示刮起細胞所需的力與工在未處理的金面上遠大於有機薄膜處理的金面並與薄膜分子碳鍊長度相關。

　　電極效能退化問題一直是影響植入系統成功與否的關鍵，在本研究中嘗試應用自我組成有機薄膜表面處理改質技術產生蛋白質與細胞難吸附的電極表面，改善植入式神經電極性能；實驗證明多極神經電極在表面處理後能降低蛋白質與細胞的沾黏吸附。

Abstract
　Nerve cuff electrodes are one of the electrode types utilized in neuroprosthetic applications. The microelectrode spiraled as a cuff type can be used for restoring nerve function via electrical stimulation or nerve signal sensing on the peripheral nerve. However, an increase of electrode impedance might occur during implantation, which will decrease the electrode performance. The crucial factor comes from the interface between the biomolecule and the surface of microelectrode. A new thin film multi-polar spiral cuff electrode, composed of self-assembled monolayer (SAMs) treated electrodes and flexible polyimide substrate, was manufactured and tested. Since the gold electrodes after the SAMs treatment can control the interactions of the biomolecule-electrode surface at the molecular scale, SAMs of varied chain lengths adsorbed upon Au-coated nerve microelectrodes were employed for protein absorption and cell adhesion studying.

　In protein absorption study, thin-film SAMs treatment upon Au/polyimide (PI) surface of the microelectrode provided a hydrophobic characteristic, which retarded protein adsorption at the initial stage and subsequent pile-up (or thickening) process. The protein-resistant effect exhibited comparable for SAMs of different chain lengths adsorbed upon Au/PI surfaces. The increase of electrode impedance as a function of protein deposition time was mainly correlated with the addition of reactance that was associated with the pile-up thickness of the deposited protein. Particularly the SAMs-modified surface was capable to detach a significant portion of the accumulated protein from the protein-deposited SAMs/Au/PI, whereas the protein-deposited layers exhibited firm adhesion upon Au/PI surface.

　In cell adhesion study, thin-film SAMs adsorbed on Au/PI provided a passive or hydrophobic surface that increased water contact angle and initial total impedance, or therefore decreased cell coverage rate. Thin-film SAMs as a dense-packed spacer provided with a relatively low ionic strength that resulted in incomplete cell sealing. To study cell-surface interactions, cell detachment test used a triangular probe tip of AFM cantilever was experimented in medium containing a comparable single cell. Overall, both the peaks forces (Fcell) and the work required to remove a comparable single cell from the anchoring domain correspond well with the increased length of alkyl chains adsorbed upon Au/PI, which was much smaller than those of the pristine surface.

　This work thus approaches to establish a consistent means to create protein-resistant and cell-repulsive characteristics on the microelectrode surface. It is therefore very promising to apply thin film SAMs adsorbed upon Au-coated surface for bio-invasive devices that have the need of functional electrical stimulations or sensing nerve signals during chronic implantation.

Table of Contents
Chinese Abstract..........................................................................................................................i
Abstract.......................................................................................................................................ii
Acknowledgments......................................................................................................................iv
Table of Contents........................................................................................................................v
List of Tables...........................................................................................................................viii
List of Figures............................................................................................................................ix

Chapter 1 Introduction................................................................................................................1
1.1 Introduction to neural prostheses..........................................................................................1
1.2 Introduction to implantable nerve cuff electrodes................................................................2
1.3 Considerations of electrode implants....................................................................................4
1.4 Surface modification techniques...........................................................................................6
1.5 The kinetics of interfacial reaction of the microelectrode....................................................8
1.6 Motivation and specific aims..............................................................................................10

Chapter 2 Materials and Methods.............................................................................................12
2.1 Fabrication of multi-polar spiral cuff microelectrode.........................................................12
2.2 Surface modification of Au substrate..................................................................................19
2.3 Sample characterization by contact angle measurement.....................................................21
2.4 Chemistry of the modified surface......................................................................................21
2.5 Protein adsorption along time and protein detachment test................................................24
2.6 Cell culture and cell coverage rate on SAMs/Au/PI...........................................................24
2.7 Measurement of AC impedance for cuff microelectrode....................................................27
2.7.1 Measurement of AC impedance for the protein absorption on electrode........................27
2.7.2 Measurement of AC impedance for the cell proliferation on electrode...........................27
2.8 Cell detachment test using a probe tip of AFM cantilever..................................................28

Chapter 3 Results......................................................................................................................33
3.1 Contact angles of SAMs treated surface.............................................................................33
3.2 Pristine SAMs/Au/PI surfaces............................................................................................35
3.3 Measurement of AC impedance for the cuff microelectrode..............................................37
3.3.1 Measurement of AC impedance for the protein absorption on electrode........................37
3.3.2 Measurement of AC impedance for the cell proliferation on electrode...........................42
3.4 Surface morphology and adhesion of protein on the microelectrode surfaces...................46
3.5 Cell adhesion test................................................................................................................51
3.6 Cell detachment test............................................................................................................54

Chapter 4 Discussion................................................................................................................57
4.1 Protein adsorption relaed to total impedance on the respective surface.............................57
4.2 Kinetics of protein adsorption.............................................................................................59
4.3 Surface morphology and adhesion of protein on the microelectrode surfaces...................60
4.4 Cell adhesion on a reaction surface.....................................................................................61
4.5 Cell adhesion related to total impedance on the respective surface....................................64
4.6 Cell adhesion and cell detachment process.........................................................................65

Chapter 5 Conclusions..............................................................................................................68

Chapter 6 Furture Prospective...................................................................................................71
6.1 Plasma-induced graft copolymerization on polymer surface..............................................71
6.2 Cell adhesion test by shear stress under flow......................................................................75

References.................................................................................................................................77

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