Electrochemically Synthesized Shape-controlled Hierarchical Flower-like Gold Nanostructures And Their Application In Biosensors

The biosensor is an important scientific detection technology in current scientific research because it involves multidisciplinary. Among many biosensors, the electrochemical biosensor has been widely used in clinical medicine, environmental monitoring, agriculture analysis, food safety, and other fields due to its fast response, high sensitivity, high selectivity, ease of operation, low cost and so on. Meanwhile, gold nanomaterials have been widely used in catalysis, biosensing, bioimaging, electronics and biomedicine due to their excellent electrical conductivity, biocompatibility, electrocatalysis, large specific surface area and other properties. Introducing gold nanomaterials into biosensors can greatly improve the sensitivity and specificity of electrochemical biosensors. Herein, a facile and one-step electrodeposition method was used to prepare three dimensional and shape-controlled gold nanostructures via tuning the experimental conditions. On the basis of successful synthesis, such gold nanostructures have been employed to construct electrochemical biosensors for DNA and microRNA detection. After system studying, hierarchical flower-like gold nanostructures(HFGNs) was chose to construct electrochemical DNA biosensor for microRNA-21 detection with high sensitivity and selectivity. More importantly, such biosensor could monitor mi RNA-21 expression level in cancer cell and determine microRNA-21 in real sample. The specific researches are as the following:1. Fabrication of gold nanostructures with different morphologies. Shape-controlled and three dimensional gold nanostructures have been synthesized by using a simple and controllable electrodeposition method via changing deposition potential, HAuCl4 concentration, deposition time and composition of electrolyte. SEM, UV-vis and SERS and other equipments were used to characterize the properties and performances of gold nanostructures. Finally, we also described the formation mechanism of the three-dimensional gold nanostructures.2. Construction of label-free electrochemical DNA biosensors. Four typical morphology of gold nanostructures were selected to construct electrochemical DNA biosensors. Compared with the efficient electrode area, linear range and detection limitation of four gold nanostructures-based electrochemical biosensors, it can be found that electrochemical DNA sensor had a lower detection limition when it possessed larger specific surface area. Considering all influence factors, we have chosen a smooth three-dimensional hierarchical gold nanostructure as a potential electrochemical detection platform because it has a wider linear range and lower detection limition.3. Construction of label-free electrochemical DNA microRNA-21 biosensors. This HFGNs-based biosensor exhibited excellent sensitivity and selectivity toward the detection of miRNA-21 with a detection limit of 1 fM. Moreover, this biosensor was also employed to monitor miRNA-21 expression level from human lung cancer cell(A549) lysates, which could detect as low as 100 A549 cells. More importantly, such biosensor could work well in 100% serum, suggesting HFGNs-based biosensor had high application potential for disease diagnosis and biological analysis.