DNA detection is in progress using various methods, including polymerase chain reaction, optical sensor and Kelvin probe force microscopy. However, these detection methods have many disadvantages, such as price, time, and complexity.<br/>However, detection based on catalytic hairpin assembly (CHA) technique has great advantages: 1. It can amplify the DNA signal isothermally. 2. Various detection method can be adapted easily. Despite of the advantages, the sensitivity and selectivity of normal existing catalytic hairpin assembly technique were not adequate for practical usage. Also, it is not effective to detect long DNAs. For these reasons, an isothermal, label-free, enzyme-free, ultrasensitive DNA detection technique using gold nanoparticles colorimetry and three ways target switching catalytic hairpin assembly was developed. As shown in figure 1, there are two steps in the method. The first step is target switching step. It is very difficult to detect long DNAs directly with high selectivity. For this reason, we used catalytic DNA (c-DNA) and catalyst complementary DNA (c-c DNA). And the second step is three ways catalytic hairpin assembly step.<br/>When the target DNA exists, c-DNAs are freed. The freed c-DNAs act like a catalytic DNA and it activate hairpin probe DNAs (H1, H2 and H3). When the branched junction structure is formed by the activation of hairpin DNAs, AuNPs that are attached to H1 and H2 aggregate each other and the color of the total solution changes from red to blue. By evaluating the degree of aggregation of AuNPs using UV-vis spectrum, we calculated the limit of detection of the proposed method (7.7 fM). Also, due to its high selectivity, it is possible to detect the target even in the presence of large amounts of wildtype DNA as in real blood sample (1%). The technique has great potential to be used to detect DNA in actual samples.

Cancer DNA detection using gold nanoparticle colorimetry and three ways target switching catalytic hairpin assembly

2019 Fall National Meeting

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