生醫微型裝置於增進DNA雜合反應效率及細胞間交互作用之研究

Biomedical microdevices for DNA hybridization enhancement and cell-cell interaction study

味正唯(Cheng-Wey Wei)

指導教授 ： 楊台鴻

共同指導教授 ： 鄭郅言

國立臺灣大學/工學院/醫學工程學研究所/博士(2005年)

https://doi.org/10.6342/NTU.2005.01862

摘要

本研究利用直寫式CO2雷射達到快速原型發展且可兼具量產的塑膠微流體晶片製作方法為目的。雷射於蝕刻壓克力載體因其粗糙的表面和有限制的改質能力而有所影響，然而可藉由表面熱處理和創新之化學改質等方法來克服問題。此外，利用雷射蝕刻法可不受等向性化學濕蝕刻深寬比之限制，深寬比1/10至7以上的微流道可輕易達成。利用掃瞄式電子顯微鏡（Scanning Electron Microscopy，SEM）和原子力顯微鏡（Atomic Force Microscopy，AFM）為量測表面性質工具。而表面化學改質部份則利用衰減全反射傅立葉轉換紅外線光譜儀（Attenuated Total Reflectance – Fourier Transform Infrared Spectroscopy，ATR–FTIR）和X 射線光電子光譜儀（X-ray Photoelectron Spectroscopy，XPS）來印證改質成效。經此程序，成功的改良CO2雷射加工機台應用於發展快速原型塑膠微流體晶片之應用性。
於發展新型快速DNA微陣列晶片中，應用離散型液滴混合（Discrete drops mixing）原理於雜合反應，藉此提升雜合反應效能與速率，進而減少試劑量及反應所需時間。於此系統中，液滴來回式雜合反應（Shuttle hybridization）意指液滴於通道中來回運動。整合DNA陣列式玻璃晶片晶片和PMMA微流道，並利用夾具作結合。應用液滴來回式雜合反應可使樣本反應體積縮小（1/100）、時間加快及提高雜合反應的訊噪比（Signal to noise ratio，S/N）。於單一核苷酸多態型（Single Nucleotide Polymorphism，SNP）實驗中，成功辨別單鹼基對錯配（Single-base-pair-mismatch）。於此系統研究中，可得到非常小的偵測極限（4.2 amol）。此方法和前人所發表之微流體陣列式整合晶片之最大差異點，為本系統之裝置適用各種通用的玻璃或塑膠微陣列晶片，不受局限某特殊材質。
最後，本研究利用微流體分流技術來研究細胞與細胞間交互作用機制，將上游細胞所分泌的一些細胞激素（Cytokines）或免疫反應的產生物，準確的控制化學濃度梯度來刺激下游另外一種細胞，達到高通量分析（High throughput assay）、非接觸式（non-contact）且即時偵測（Real-time monitoring）之細胞共同培養系統（Coculture system）方式，此系統將可用來研究幹細胞（Stem cell）分化的機制或藥物的快速篩選開發。

關鍵字

雷射蝕刻 ； PMMA改質 ； 微流體 ； DNA 微陣列 ； 混擾離散液滴混合 ； 細胞共同培養 ； 濃度梯度

並列摘要

The use of direct-write laser micromachining on poly(methyl methacrylate) (PMMA) to fabricate microfluidic chip has the potential for fast prototyping and production. However, the advantage has been diminished by the rugged surface and the limited surface chemistry modification available. To overcome this problem, we have developed a flexible and economic pipeline including PMMA micromachining, surface smoothness improvement, and a universal surface modification for introduction of various functional groups. The micromachining is accomplished by a commercial laser scriber, to which a user designed computer drawing is sent directly for grooving. The typical trench width is 140 micrometer while the aspect ratio up to more than 7 is easily achieved. Smooth surface is obtained after a one-step thermal annealing treatment after machining. The chemical modification is performed by a simple reduction reaction followed by the widely used organosilane chemistry to introduce diverse functional groups such as perfluoroalkyl (-CnF2n+2), amino (-NH2), and sulfhydryl (-SH) for surface passivation or further biomolecule immobilization. The surface smoothness after thermal annealing has been examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM) to be comparable to pristine surface. The surface chemistry modification has been confirmed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The whole procedure provides a very efficient micromachining platform to fabricate PMMA microfluidic chip for both prototyping and production.
In the shuttle hybridization for DNA microarray. 20-mer and 80-mer oligonucleotide probes and singly labeled 20-mer and 80-mer targets, representative of the T-cell acute lymphocytic leukemia 1 (TAL1) gene, has been used to elucidate the performance of this hybridization approach. In this format, called shuttle hybridization, a conventional flat glass DNA microarray is integrated with a PMMA microfluidic chip to reduce the sample and reagent consumption to 1/100 that associated with the conventional format. The trench spacing is compatible with the inter-spot distance in standard microarrays. The microtrench chip and microarray chip are easily aligned and assembled manually so that the microarray is integrated with a microfluidic channel. Discrete sample plugs are employed in the microchannel for hybridization. Flowing through the microchannel with alternating depths and widths scrambles continuous sample plug into discrete short plugs. These plugs are shuttled back and forth along the channel, sweeping over microarray probes while re-circulation mixing occurs inside the plugs. Integrating the microarrays into the microfluidic channel reduces the DNA-DNA hybridization time from 18 hours to 500 seconds. Additionally, the enhancement of DNA hybridization reaction by the microfluidic device is investigated by determining the coefficient of variation (CV), the growth rate of the hybridization signal and the ability to discriminate single-base mismatch. Detection limit of 19 attomoles was obtained for shuttle hybridization. 1 µl target was used to hybridize with an array that can hold 5000 probes.
A novel microfluidic coculture system was developed for more accurately modelling the interaction of macrophages and osteoblasts. The microfluidic coculture chip was fabricated by CO2 laser direct-writing on poly(methyl methacrylate) (PMMA) and was designed to separate two cell types by a microchannel, while permitting cellular media to transfer. The released inflammatory cytokines (ex: IL-1β, TNF-α) activated in upstream macrophages flow through a microfluidic system and generate linear concentration gradients in down-stream wells and induce down-stream osteoblasts to release prostaglandin E2 (PGE2), which is well-known as a bone resorption marker. Colorimetric MTT assay was used to examine the osteoblast viability. This system can be used to evaluate the cell-cell interaction while physically separate the interacting cells.

並列關鍵字

Laser-micromachining ； PMMA modification ； microfluidic ； DNA microarray ； chaotic droplet mixing ； coculture ； concentration gradients

參考文獻

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