Over the past few years, several studies have been made on microelectrodes for invasive Brain-Machine Interface (BMI). In this field, one of the main issues is the formation of glia scar that acts as insulating layer on the surface of the implanted microelectrodes. Therefore, it is essential to modify the surface of the microelectrodes to enhance the life time of the microelectrodes. In this study, the effect of nanoporous topography on SU-8 surface was investigated for neurite development using PC12 (neuron like cell) cells. Well-organized nanoporous SU-8 surface was fabricated using nanosphere lithography (NSL) by means of polystyrene nanoparticles. The diameter of nanopores was approximately 200 nm. Its size is similar to the size of filopodia. Cells were cultured on SU-8 surfaces with four different conditions: smooth bare surface, smooth bare surface coated with poly-L-lysine (PLL), nanoporous surface and nanoporous surface coated with PLL. The objective of this study is investigation of the neurite development on the four different surfaces. The results of differentiation level showed cells were nearly not differentiated on smooth surface. However, PLL coated smooth, nanoporous and PLL coated nanoporous surface showed about 25 % of differentitation level and had no significant difference between them. The results of the neurite numbers showed very low neurite numbers on smooth surface than that on other surfaces. On the other hand, no obvious effect was found on PLL coated smooth, nanoporous and PLL coated nanoporous surfaces. The results neurite length also show the shortest neurite length in smooth surface. Interestingly, PLL coated smooth surface had low neurite length compared to nanoporous and PLL coated nanoporous surface. It was found that nanopores enhanced nerite development as long as similar to PLL coated smooth surface while smooth bare surfaces showed very poor differentiation level and neurite outgrowth. These findings suggest that the nanoporous topography did affect neurite development. The results of this study suggest the effect of the nanoporous SU-8 surface on the in vitro neurite outgrowth of PC12 cells. Therefore, if this nanoporous surface is applied to the surface of implantable neural probe, we could expect the improved results as long-term neuronal recordings than the neural probe with smooth surface. That may because such bioactive surface (nanostructured porous SU-8) is able to allow for neuron to interact with electrode sites (recording sites) which have nano-scale features. By using surface topography, we can to control cell development for biomedical applications not only neural microelectrode and microrobot but also drug delivery and cell guidance, etc. ⓒ 2013 DGIST
Table Of Contents
I. INTRODUCTION 1 -- 1.1 Objectives and motivations 1 -- 1.2 Hypotheses 3 -- 1.3 Background information 4 -- 1.3.1 Neural microelectrodes 4 -- 1.3.2 The cellular response to implanted microelectrodes 5 -- 1.3.3 Re-engineering the cellular response 7 -- 1.3.4 Nanosphere lithography for nanopore arrays 9 -- II. MATERIALS AND METHODS 13 -- 2.1 Fabrication of nanopore arrays on SU-8 surface 13 -- 2.1.1 Materials 13 -- 2.1.2 Fabrication process 14 -- 2.1.3 Evaluation of surface structure by SEM or AFM 17 -- 2.2 PC12 cell culture test 18 -- 2.2.1 Materials 18 -- 2.2.2 Preparing substrates for cell culture 19 -- 2.2.3 PC12 cell culture 20 -- 2.2.4 Image analysis 21 -- 2.2.5 Reverse Transcriptase (RT)-Polymerase Chain Reaction (PCR) for NSE 21 -- 2.2.6 Cell culture sample preparation for SEM analysis 21 -- III. CHARACTERIZATIONS OF NANOPORES 23 -- IV. RESULTS OF PC12 CELL OUTGROWTH 29 -- V. CONCLUSIONS 50 -- 5.1 Conclusions 50 -- 5.2 Future work 51 -- REFERENCES 52