大腸桿菌為常見的感染菌之一，傳統的鑑定方式包括培養法以及生化檢測，但是這些方法往往需要耗費大量時間 (一天以上)。拉曼光譜具有可對細菌進行快速且非侵入性檢測之優勢，藉由不同細菌之指紋圖譜可應用於鑑定，但是細菌之拉曼訊號並不強，而表面增顯拉曼光譜(SERS)可讓某些特徵峰訊號增強，因而近年來此類SERS技術常被用來檢測細菌。本實驗使用一種具有中孔洞二氧化矽包覆奈米銀的複合性材料，其奈米銀的含量為16%，以DTNB為探針分子，發現中孔洞二氧化矽包覆奈米銀可明顯增顯其拉曼散射訊號。吾人將此材料以不同壓力壓製成錠 (100, 200, 300, 400 kg/cm2)，配合使用銀膠體溶液與大腸桿菌菌液預混合樣本滴於錠材表面所建立之一套可供快速及有效獲得SERS的鑑定分析法。實驗結果發現，使用壓力愈大，樣本液體被過濾完全所需的時間愈長，而奈米銀預混合的大腸桿菌在錠材上之分布也愈不均勻。因此，吾人使用最佳壓力條件100 kg/cm2為最後錠材的製備規格，以利後續實驗進行大腸桿菌表面增顯拉曼光譜的收集。吾人發現此套基於SERS的鑑定分析法，當奈米銀與大腸桿菌菌液預混合樣本裡的液體被過濾完之後，表面吸附奈米銀之大腸桿菌會以小黑點嵌留於錠材表面，此大腸桿菌受到奈米銀有效包覆下受光產生明顯的SERS，使特徵峰訊號明顯得到提升。相信未來此套鑑定分析法定應能用於大腸桿菌造成的嚴重疾病之臨床輔助診斷上，並且推展至其它致病細菌之診斷與鑑定。

Escherichia coli (E. coli) is a common cause of human bacterial infections. Classical identification methods for E. coli infection include conventional culture and biochemical tests, in either the clinical diagnostic stage or the species identification stage. Most of these methods are very time-consuming. Raman spectroscopy, a novel microbial detection instrument, can provide a rapid and non-invasive detection of bacteria in several previous studies. However, some characteristic Raman signals are not strong enough for bacterial differentiation because of the limitation in bacterial number for some clinical scenarios. Surface-enhanced Raman spectroscopy (SERS) is an advanced technique to enhance the specific Raman signals, frequently used to identify different bacteria. In this study, 16%AgNPs@mesoporousSiO2, a promising new composite for SERS proved by previous studies, was tested for E. coli identification. A SERS test was carried out by using DTNB as a probing molecule. We found the characteristic Raman signals of DTNB were greatly enhanced through parametric optimization in our experiments. 16%AgNPs@mesoporousSiO2 substrate is fabricated from the best pressure 100 kg/cm2 for following tests because of this conditioned substrate having the optimal location for E. coli, and the fastest filtration rate. The excellent E. coli localization breaks through the conventional detection limit down to 104~105 CFU/mL. The filtration rate promises a powerful clinical application. Pre-mixing silver colloid solution with samples having E. coli were dropped on and filtered by 16%AgNPs@mesoporousSiO2 substrate for E. coli SERS detection. The SERS characteristic signals of E. coli were greatly enhanced and rapidly detected by this novel preparation, silver colloid solution premixing and 16%AgNPs@mesoporousSiO2 filtrating and localizing. In the future, we can expect this assay may be used to identify other bacteria other than E. coli.

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