Synthesis Of Protein-like Silver-cysteine Hybrid Nanowires And Related Applications In Biosensors

Metal-organic hybrid materials have emerged as a class of novel materials over the last two decades. Especially one-dimensional (ID) nanomaterials have been intensively investigated because the intrinsic properties of these hybrid materials not only rely on their chemical composition and crystal structure but also are affected by their size, surface chemistry and morphology. In this dissertation, we prepared novel protein-like silver-cysteine hybrid nanowires (p-SCNWs) by a simple and green one-step non-template seed-less aqueous chemical synthetic strategy. The p-SCNWs were used as the signal amplifying labels for ultrasensitive and highly selective detection of the cancer biomarker, DNA hybridization and thrombin by chemiluminescence (CL) and visual colorimetry. This dissertation consists of following five chapters.In chapter 1, the general introduction, the signification, classifications and the historical perspective of metal-organic hybrid materials and biosensors, and the applications of hybrid materials in biosensors, and the mechanisms of CL were described based on the investigation of the literatures, the purpose and signification of this dissertation were also demonstrated.In chapter 2, a novel p-SCNWs were prepared by a simple and green one-step non-template seed-less aqueous chemical synthetic strategy. The pH of solution, ratio of reactants, and the concentrations of silver ion and cysteine played the key roles in the formation of the p-SCNWs. The effects of these experimental conditions were described and discussed to reveal the growth mechanism and three-dimensional structure of p-SCNWs. We have studied the CL properties of p-SCNWs by a coupling chemiluminescent (CL) reaction system (Ag+- Mn2+-2S2O8-H3PO4-luminol), and detected the concentration of silver ion in p-SCNWs.In chapter 3, the biofunctionalized p-SCNWs were used as excellent signal amplifying chemiluminescence labels for ultrasensitive and highly selective detection of important antigens, such as cancer biomarkers. To prepare a sandwich immunocomplex, paramagnetic microspheres-loaded capture antibody were used to capture CEA by the immunoreaction. By the novel p-SCNW labels, CEA could be detected in the linear range from 5 to 400 fg/mL with a limit of detection (LOD) of 2.2 fg/mL (3 σ), which is much lower than that obtained by commercially available enzyme-linked immunosorbent assay (ELISA).In chapter 4, an ultrasensitive DNA hybridization detection method based on visual colorimetry and CL using p-SCNWs as signal amplification labels, was developed. The assay relied on a sandwich-type and the p-SCNWs on the hybrids were dissolved in HNO3 solution to release numerous Ag+. The strong catalysis of Ag+on the reaction of K2S2O8-Mn2+-H3PO4 led to the production of purple KMnO4. Based on the solution color change, a novel method for detection of the target was developed. Meanwhile, the purple KMnO4 could oxidize luminol under alkaline condition and give a strong chemiluminescent signal. The detection limits of visual colorimetry and CL were 7.5 fM and 0.34 fM (3σ), respectively. The single-base pair mismatched DNA and noncomplementary DNA could be distinguished well from the visual color comparison related to the complementary DNA hybridization.In chapter 5, to demonstrate the versatility of the nucleic acid-modified p-SCNWs, a thrombin binding aptamer was chosen as the model to study the application of the platform in the detection of protein. Two aptamers (Apt1 and Apt2), which could recognize their two corresponding distinct sites of thrombin, were coupled to the surfaces of PMs and p-SCNWs, respectively. Then they could be hybridized with thrombin through the specific recognition of the two aptamers to form a sandwich structure. The detection limits of visual colorimetry and CL were 5 pM and 0.17 pM (3σ), respectively.