Novel Fluorescence Detection Of DNA Based On Gold Nanoparticles

Living things depend on genes. Genes hold the information of heredity. Detection of gene is important to disease diagnosis and prevention. Breast cancer is one of the most common malignancies of women. It threats women's health seriously. Breast cancer susceptibility gene 1 (BRCA1) plays an important role in cell cycle regulation, gene transcription regulation and maintaining the stability of gene. The mutations of BRCA1 will weaken these functions and lead to an increased risk for breast cancer. Thus, detection of BRCA1 gene will offer an opportunity to early diagnosis, cancer prediction and help patients to take the appropriate treatments.In recent years, the rapid development of nanomaterials provides a new way to molecular biology. Nanomaterials have many special properties, such as surface effect, small-size effect, quantum-size effect and bulk quantum Hall effect, which result in serials of important applications in the area of disease diagnosis, contagion detection, environment monitoring, medicine research and medicolegal Identification. As an important kind of nanomaterial, gold nanoparticle is widely used as DNA detection probe, DNA supporter and fluorescence quencher.Sensitivity and simplicity are important in DNA detection. In this work, we establish two different DNA fluorescence assays using gold nanoparticles as quenchers and the different absorption between GNPs and different DNA. We attempt to improve the sensitivity and the detection time of DNA assays.The main contents are as follows:1. DNA structure and its common detection methods are simply introduced. DNA fluorescent probe, the properties of GNPs and their applications in DNA detection are described in detail.2. A new label free DNA fluorescence assay based on GNPs quenching the fluorescence of RB is established. The assay is based on the following two properties. One is the different adsorption properties of single-stranded and double-stranded DNA on GNPs in colloidal solution. The other is the different quenching ability of aggregated GNPs and dispersed GNPs on RB. The GNPs aggregation-dependent fluorescence change caused by different DNA hybridization is used for DNA detection with high sensitivity. Under optimal conditions, the detection limit of this method achieves 2.9×10-13 mol L-1. The method requires no modification and the whole detection process is simple and fast.3. A homogeneous DNA detection based on GNPs and circle fluorescence amplification strategy by exonucleaseⅢ(ExoⅢ) is studied. On the basis of GNPs as quenchers, not only the different adsorption properties of single-stranded and double-stranded DNA on GNPs in colloidal solution but also the digestion of ExoⅢis used. In the assay, the FAM-labeled probe DNA is non-fluorescent in the presence of GNPs and cannot be digested by ExoⅢ. When target DNA hybridizes with probe DNA, the hybridization leads to release of ds-DNA, which is then digested by ExoⅢto produce free non-quenched fluorophore and ultimately release the target. The released target can then hybridize with another to start a new cycle. Because a single target sequence can lead to the release and digestion of numerous fluorophore strands from the surface of GNPs, a remarkable signal amplification is achieved. Under optimal conditions, an excellent liner relationship between△F and the t-DNA concentration is obtained over the range of 2.5×10-11 mol L-1 to 1.0×10-9 mol L-1. The detection limit of the assay is determined to 1.0×10-11 mol L-1.