摘要：氮化鎵(Gallium nitride, GaN)為半導體材料，硬度高、抗化性強，由於它獨特的物理和化學性質，已被選為多種微電子和高溫氣體感測器應用發展的材料，但在生醫材料的應用上還是相當有限，本實驗室在先前的研究[Biomaterials 29 (2008) 1573-1582; 27 (2006) 3361-3367]已證實氮化鎵晶片能促進小腦顆粒神經細胞的貼附與生長，本計畫的目的則是要進一步探討氮化鎵晶片誘導神經細胞與神經幹細胞生長之原理與應用，長期的目標則是要結合氮化鎵在電學和生物學的特性，發展以氮化鎵為系統的神經晶片。第一年將先探討氮化鎵影響PC12細胞生長的訊息傳遞路徑，PC12細胞分享神經細胞的許多的生理特性，藉此可了解氮化鎵晶片誘導神經細胞生長之原理，雖然有很多文獻探討PC12細胞的訊息傳遞路徑，但他們的研究大多是將PC12細胞培養在塗佈polylysine或者自然基材的表面，再加以藥物刺激，據我們所知，並無研究直接探討PC12細胞培養在生醫材料或氮化鎵上的訊息傳遞路徑。第二年我們將探討氮化鎵對初代神經細胞培養的影響，著重在神經細胞樹突與軸突的生長與分化，如GAP-43, synapsin Ι 與 synaptophysin等蛋白質的表現，其假設是神經細胞培養的訊息傳遞與其分化功能的發展密切相關，因此可與第一年的成果相互結合。若神經細胞培養在氮化鎵後，仍能具有特定的分化功能，則神經幹細胞培養在氮化鎵上亦大有可為，我們假設氮化鎵應可促進神經幹細胞的生長並分化成神經細胞，因此第二年同時會進行神經幹細胞在氮化鎵上的培養，如此將更符合發展氮化鎵神經晶片。最後，我們將探討神經幹細胞培養在氮化鎵上的訊息傳遞路徑，因為我們不知道神經細胞與其先驅神經幹細胞在同一材料上是否有相同的反應機制，此一課題將在第三年進行深入探討。此外氮化鎵和神經細胞與神經幹細胞相互作用的專一性將被檢驗，在氮化鎵上被觀察到的功能將在其他III-V族半導體材料被檢驗，例如AsGa 和AlN等。本計畫執行三年後期盼經由實驗之結果能更進一步提昇了解氮化鎵材料如何控制神經細胞與神經幹細胞，使氮化鎵能發揮最大的功效，配合國內半導體工業的發展，具有各種應用之價值。本結果將發表於國際著名的期刊，並訓練參與人員使其具有實作能力。
Abstract: Gallium nitride (GaN) is a so-called III-V compound semiconductor material with a wide bandgap and a relatively high bandgap voltage. Due to its unique physical and chemical properties, GaN devices have been developed for a variety of microelectronic and high-temperature gas sensor applications. In our previous studies [Biomaterials 29 (2008) 1573-1582; 27 (2006) 3361-3367], GaN chip has been shown to mediate the response of cerebellar granule neurons to promote cell adhesion and differentiation. The objective of the present project is to investigate the mechanism and application of GaN chips for maintaining growth of neurons and neural stem cells. Therefore, the long term ultimate goal is to develop a neural chip based on the GaN system from the integration of electronics and biological system for use in a microelectrode array.In the first year, the neuroprotection mechanism of regulating the signal pathway by GaN in pheochromocytoma (PC12) cells will be examined. PC12 cells resemble adrenal chromaffin cells, which share many physiological properties of neurons. Although there are many papers published for measurement of the signal pathway of PC12 cells, their principle research efforts are dedicated to PC12 cells cultured on polylysine-coated surface or natural substrates under the stimulation of drugs or growth factors. To our knowledge, no study has been devoted to the identification of the effect of biomaterial or GaN on activating PKB/Akt and MAPK/ERK signal pathways.In the second year, Western blot analysis and immunocytochemical characterization will be used to analyze neurite and axon growth of primary cerebellar granule neurons cultured on GaN, such as GAP-43, synapsin Ι and synaptophysin. Based on these results, we can know whether neuronal connections and function can be formed on GaN and its relation with Akt or MAPK activation. In addition to neurons, neural stem cells will be tested to analyze the role of GaN in determining the fate of neural stem cells. It is reasonable to assume that GaN can be considered as an optimum substrate for the differentiation of neural stem cells into neurons since GaN can be considered as a neuron-favorable material.In the third year, the intracellular mechanisms involved in GaN mediated neural stem cell differentiation will be examined. We will investigate the specific proteins-dependent signaling pathways on neural stem cell differentiation. It is interesting to know neurons and neural stem cells on GaN are mediated by similar or different mechanisms. Therefore, we will investigate whether the novel effect of GaN in neural stem cells is mediated by the Akt and/or MAPK signaling pathway. Finally, whether the interaction of GaN and neurons is specific will be studied. The neuroprotection effects observed in GaN will be examined for other III-V compound semiconductor materials such as AsGa and AlN.At the end of this project, the mechanism of GaN chips for maintaining growth of neurons and neural stem cells can be clarified, which is beneficial to the development of a neurochip requiring the integration of biological system and semiconductor material. The outcome will be published in famous journals, and the entire people join this project will gain good training.
Gallium nitride (GaN)
neural stem cells