Design Of Metal Nanoparticles Probe And Its Applications In Biosensor

Biomaterials nanotechnology act as a major aspect in the field of nanotechnology, the progress and development of it leads the booming of biomedical and drug delivery fields. It is important to combine the identified ability of biomolecule with the excellent properties of nanomaterials for developing a variety of novel functional nanomaterials probe in the field of biosensor, targeted therapy and photoelectric materials. One of the key question in the field of biomaterials nanotechnology is how to design a functional nanomaterials probe to take advantage of biological molecules (such as DNA, RNA and protein, etc.) and nanomaterials. This paper aims to construct probes based on metal nanoparticle for detecting nucleic acid molecule. This thesis can be divided into four parts.1. Single silver nanocube nanoprobes for real-time detection of the lung cancer associated miRNAAs a promising biomarker for cancer, MicroRNA regulates many cellular processes, however,because of the low abundance and short size of MicroRNA, it is challenging to develop simple, fast and inexpensive biosensor to detect them. Herein, a plasmonic nanobiosensor for detecting microRNA-21 (miR-21) has been developed by using single silver nanocubes (AgNCs) modified with thiolated ssDNA as probes. The nucleic acid hybridization process were observed in situ on a single AgNC surface. Both the theoretical results by finite-difference time-domain (FDTD)simulations and experimental results suggested that the refractive index (RI) on the surface of AgNCs is increased when the miR-21 hybridized with ssDNA, which result in the red-shift of localized surface plasmon resonance (LSPR) peak. As the concentration of miR-21 increases, the hybridization between ssDNA and miR-21 on the AgNC surface results in a linear red-shifting of the scattering peak, and detection limit of 1 fM. In addition, the mechanism of the reaction has been explained successfully by FDTD simulations, and the each individual AgNC can act as a probe for the detection of miR-21.2. Single Au@Ag core-shell nanocube nanoprobes used for single-molecule detection and logic operationsStudies at the single-molecule level have revealed molecular interactions, kinetics and conformational changes in many biomolecular systems. However, currently available methods usually require substrate of fluorescent label, which is prone to photobleaching, low signal-to-noise and unsuitable for direct detection of subtle structures. Here, a smart plasmonic nanobiosensor for detecting microRNA-21 (miR-21) and performing DNA-based logic operations as well as bio-memory has been developed by using individual Au@Ag core-shell nanocube (Au@Ag NC)modified with tetrahedron-structured DNA (tsDNA) as probes. An average wavelength redshift of approximately 0.4 nm is obtained of single miR-21 hybridization event. This system doesn't only allow real-time detection of miR-21 with aM sensitivity over a large dynamic range from laM to InM, but also successfully performs DNA-based logic operations as well as bio-memory by using miR-21,Kpnl, and StuI-responded assay as the model.3. Single-layer transition metal dichalcogenide nanosheet based nanosensors for multiplexed detection of DNARapid and sensitive detection of multiple target molecules simultaneously is a great challenge in gene expression profiling and molecular diagnostics. To address the problem, the probes are designed based on single-layer transition metal dichalcogenide (TMD) nanosheets (NSs), including MoS2, TiS2 and TaS2. Novel fluorescence sensing platforms for sensitive and selective detection of DNA based on the high fluorescence quenching ability and different affinity toward the dye-labeled single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) of the TMD nanosheets. Notably, the single-layer TaS2 NS-based sensor presents quenching efficiency of 99% and detection limit of 0.05 nM. Importantly, for the first time, the single-layer TaS2NS-based multiplexed analysis of H1H1 and H5N1 sensor is also developed.4. DNA-templated silver nanoclusters for multiplexed fluorescent DNA detectionCompared with organic dyes, metal nanoparticles have stronger stability, higher fluorescence intensity and longer life. Herein, novel label-free molecular beacons (MBs) are designed based on DNA templated-silver nanoclusters (Ag NCs) for multiplexed DNA detection. Two types of DNA-templated Ag NCs, with green emission (507 nm) and orange emission (597 nm), respectively, are used as fluorescent hosts in this sensitive and label-free analysis system. This method offers an inexpensive and label-free platform for multiplexed analysis of H1N1 and H5Nlwith low detection limit (25 nM).