Linear light-scattering of gold nanostars for versatile biosensing of nucleic acids and proteins using exonuclease III as biocatalyst to signal amplification

摘要

Gold nanomaterials promise a wide range of potential applications in chemical and biological sensing, imaging, and catalysis. In this paper, we demonstrate a facile method for room-temperature synthesis of gold nanostars (AuNSs) with a size of similar to 50 nm via seeded growth. Significantly, the AuNSs are found to have high light-scattering properties, which are successfully used as labels for sensitive and selective detection of nucleic acids and proteins by using exonuclease III (Exo III) as a biocatalyst. For DNA detection, the binding of targets to the functionalized AuNS probes leads to the Exo III-stimulated cascade recycling amplification. As a result, a large amount of AuNSs are released from magnetic nanoparticles (MNPs) into solution, providing a greatly enhanced light-scattering signal for amplified sensing process. Moreover, a binding-induced DNA three-way junction (DNA TWJ) is introduced to thrombin detection, in which the binding of two aptamers to thrombin triggers assembly of the DNA motifs and initiates the subsequent DNA strand displacement reaction (SDR) and Exo III-assisted cascade recycling amplification. The detection limits of 89 fM and 5.6 pM are achieved for DNA and thrombin, respectively, which are comparable to or even exceed that of the reported isothermal amplification methods. It is noteworthy that based on the DNA TWJ strategy the sequences are independent on target proteins. Additionally, the employment of MNPs in the assays can not only simplify the operations but also improve the detection sensitivity. Therefore, the proposed amplified light-scattering assay with high sensitivity and selectivity, acceptable accuracy, and satisfactory versatility of analytes provides various applications in bioanalysis. (C) 2015 Elsevier B.V. All rights reserved.