Development of Color-Based Bacterial Biosensor for Arsenic Detection

砷為重金屬污染物之一，為已知人體致癌物。許多研究指出，使用含砷地下水做為飲用水、灌溉水已在世界各地造成人類健康危害。現行砷污染檢測技術雖具有相當高的靈敏度與準確度，但應用於大規模即時檢測及其價格，仍有其限制性。因此，本研究開發快速及經濟現地檢測地下水中砷之細菌生物感測器。本研究使用非致病菌E. coli DH5α為宿主(host cell)，利用arsR與lacZ之基因組合建構，以顏色改變為其訊號基礎，發展利用目測或光度計檢測水樣中砷之生物感測器。本研究建構之生物感測器，其定量範圍為10至500 μg/l之間，檢測時間約為1到3小時。本研究亦分析細菌數量(以OD600值表示)對於生物感測器呈色能力之差異，結果顯示，較高OD600值之生物感測器，呈色強度亦較高，且檢測時間較短，但量測值變動較大。本研究所建構之生物感測器應用於含砷地下水樣品分析，成功檢測三價砷濃度。另外，本研究分析不同保存條件，以及不同OD600值，在保存期限上的差異。結果顯示，不同OD600值對於保存期限影響不明顯；其中，以液體保存於4℃，具有最長之保存期限，約為九天，其餘保存方式之保存期限，約為三至四天左右。本研究建構之生物感測器，具有低成本、可定量，以及操作簡單等優勢，能應用於砷污染調查檢測，結合現有化學檢測技術，可提升環境污染管理之效率。Arsenic is one of the heavy metal pollutants and a known human carcinogen. Using arsenic contaminated groundwater for drinking or irrigation has caused major health problems for humans around the world. Current arsenic detecting techniques based on physicochemical methods have high sensitivity and accuracy. Yet, in addition to high cost, the applications to large scale detection were still limited. Therefore, this study developed a color-based bacterial biosensor which is easy and inexpensive for arsenic screening and could be complementary to physicochemical methods. The arsR-lacZ recombinant gene cassette in nonpathogenic strain E. coli DH5α was used in the color-based biosensor which could be measured by eyes or spectrometer. The developed bacterial biosensor demonstrates a quantitative ranging from 10 - 500 μg/l in 1 - 3 hours reaction time. In addition, the result showed that biosensor with higher OD600 has higher induction and lower response time, but lower accuracy. Furthermore, the biosensor was able to successfully detect and estimate arsenic concentration in groundwater samples. The result further showed that OD600 did not affect the shelf life of biosensor. Among different storage methods, biosensor in liquid at 4℃ showed the longest shelf life about 9 days, whereas others were about 3 - 4 days. In conclusion, this study showed that the arsenic biosensor with reliable color signal makes it useful for large scale rapid screening of arsenic pollutants providing the potential for better management strategies for environmental quality control