Synthesis of Fluorescent Carbohydrate-Protected Au Nanodots for Detection of Concanavalin A and Escherichia coli

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• 作者：Chih-Ching Huang ; Chao-Tsen Chen ; Yen-Chun Shiang ; Zong-Hong Lin ; Huan-Tsung Chang
• 刊名：Analytical Chemistry
• 出版年：2009
• 出版时间：February 1, 2009
• 年：2009
• 卷：81
• 期：3
• 页码：875-882
• 全文大小：330K
• 年卷期：v.81,no.3(February 1, 2009)
• ISSN：1520-6882

文摘

This study describes a novel, simple, and convenient method for the preparation of water-soluble biofunctional Au nanodots (Au NDs) for the detection of Concanavalin A (Con A) and Escherichia coli (E. coli). First, 2.9 nm Au nanoparticles (Au NPs) were prepared through reduction of HAuCl₄·3H₂O with tetrakis(hydroxymethyl)phosphonium chloride (THPC), which acts as both a reducing and capping agent. Addition of 11-mercapto-3,6,9-trioxaundecyl-α-D-mannopyranoside (Man-SH) onto the surfaces of the as-prepared Au NPs yielded the fluorescent mannose-protected Au nanodots (Man-Au NDs) with the size and quantum yield (QY) of 1.8 (±0.3) nm and 8.6%, respectively. This QY is higher than those of the best currently available water-soluble, alkanethiol-protected Au nanoclusters. Our fluorescent Man-Au NDs are easily purified and by multivalent interactions are capable of sensing, under optimal conditions, Con A with high sensitivity (LOD = 75 pM) and remarkable selectivity over other proteins and lectins. To the best of our knowledge, this approach provided the lowest LOD value for Con A when compared to the other nanomaterials-based detecting method. Furthermore, we have also developed a new method for fluorescence detection of E. coli using these water-soluble Man-Au NDs. Incubation with E. coli revealed that the Man-Au NDs bind to the bacteria, yielding brightly fluorescent cell clusters. The relationship between the fluorescence signal and the E. coli concentration was linear from 1.00 × 10⁶ to 5.00 × 10⁷ cells/mL (R² = 0.96), with the LOD of E. coli being 7.20 × 10⁵ cells/mL.