Application Of Gold Nanoparticles Based Plasmonic Nanoprobes In Biological Analysis

With the rapid development of nanotechnology,nanoplasmonic materials exhibit unique light-scattering properties,which have attracted great attention from researchers and rapidly developed and applied in the field of biochemical sensing.Recently,light-scattering from plasmonic materials（noble metal nanoparticles）has become one of the most used techniques for the quantification and characterization of different nanoparticles.Noble metal nanoparticles have received extensive attention due to their easy preparation,biocompatibility,inertness,and strong color.In particular,gold nanoparticles are widely used in the field of biosensing detection due to their unique optical properties.In this study,we discussed in detail the currently developed biosensors based on the unique optical characteristics of Au NPs.Mainly,we discuss two different plasmonic biosensing,including local surface plasmon resonance（LSPR）and surface-enhanced Raman spectroscopy（SERS）based sensors.Based on these backgrounds,this dissertation focuses on the design of Au NP-based plasmonic nanoprobes and aims to study the application of Au NP-based plasmonic nanoprobes for chemical biosensing.This content can be divided into four parts.1.Multifunctional shape-dependent plasmonic nanoprobe by enzymatic etching of single gold triangular nanoplateHydrogen peroxide（H₂O₂）plays a vital role in various signaling transduction processes,aging,and diseases.However,the excessive production of H₂O₂ causes various diseases.Herein,a multifunctional shape-dependent plasmonic nanoprobe is developed for H₂O₂ detection.Due to the enzymatic anisotropic etching of Au TNPs in the presence of trace H₂O₂,the plasmonic nanoprobes show blueshifts in LSPR scattering spectra and a notable scattering color change in dark-field microscopy（DFM）images.The peak position in the scattering spectra blue-shifts linearly with the increase of H₂O₂ concentration,and exhibits high sensitivity to H₂O₂ in a large range from 2.5 to 100μM with a lower LOD of 0.74μM.Moreover,the experimental results are supported by the simulated results via the finite-difference time-domain（FDTD）method.The nanoprobes have been further used for intracellular H₂O₂ detection in live cells.In addition,after careful analysis of the raw data of Au TNP@HRP etching,the etching of Au NT also provides an alternative method to design novel plasmonic logic chips and write-once plasmonic memories.2.Tetrahedral DNA-assisted core-satellite assembly as SERS sensor for mercury ions at the single-nanoparticle levelWith years of outrageous mercury emissions,it is an urgent need to develop sensitive and selective methods for detecting mercury ions(Hg²⁺)to deal with the increasingly serious mercury pollution in water.Herein,we design a SERS sensor based on tetrahedral DNA-assisted core-satellite assembly for the detection of Hg²⁺at the single-molecule level under DFM-correlated Raman spectroscopy.The SERS sensor consists of a core Au NP,satellite Au NPs,and tetrahedral DNA structures as the linkers.One edge of the tetrahedron is made up of single-stranded DNA containing Hg²⁺aptamer.In the presence of Hg²⁺,the interparticle distance changes from 4.5 to 1.2 nm,thus leading to the enhancement of the SERS signal.The SERS signal enhancement shows a linear correlation with the concentration of Hg²⁺.Moreover,both the experimental results and FDTD calculations have verified that the SERS intensity is linear with the concentration of Hg²⁺.In addition,this SERS sensor shows high specificity for identifying Hg²⁺.Furthermore,the SERS sensor is applied for the detection of trace Hg²⁺in tap water and lake water.With its high selectivity,the SERS sensor has the potential to discriminate Hg²⁺in the fields of environmental monitoring and food safety.3.Real-time monitoring of molecule conformational change at single-molecule level via SERS molecular-rulerReal-time analysis of a single DNA aptamer conformational dynamics is essential to understanding the function of DNA aptamers at the single-molecule level.Herein,we design tetrahedral DNA-assisted core-satellite nanostructures as SERS molecular-rulers to monitor the change process of single mercury ions(Hg²⁺)aptamers by Hg²⁺stimuli-responsive under DFM-correlated Raman spectroscopy.The individual Hg²⁺aptamer conformational change event is triggered by the presence of Hg²⁺,leading to the stepwise closing of the satellite to the core.Benefiting from the morphology change,the stepwise rises of SERS intensity with a certain waiting time are observed.Based on these results,our SERS molecular-ruler is employed to monitor the change process of the single Hg²⁺aptamer.Moreover,individual Hg²⁺aptamer conformational change events were well confirmed by in-situ scanning electron microscopy（SEM）and FDTD calculations.Furthermore,it is also demonstrated that our SERS molecular-ruler is a valid method to obtain the intermediate states,the binding sites in an aptamer,and the kinetics of Hg²⁺aptamer conformation changes.For future applications,our SERS molecular-rulers have the potential to realize multi-level optical storage.4.Revealing the intracellular force in the endocytosis process by SERS of 1,4-Benzenedithio-mediated nanogap at the single-particle levelStudying the endocytic uptake force is essential for mediating the cellular uptake process.However,the correlation between the endocytic force and the endocytosis trajectory remains unclear.Herein,we develop 1,4-benzenedithiol（BDT）bridged core-satellite nanostructures as SERS mechanical probes to simultaneously trace the dynamic alterations of nanomechanics in the cell membrane and the trajectory of nanoparticles in real-time during the endocytosis process.These mechanical probes exhibit a good responsibility in SERS intensity ratios while undergoing mechanical pressure,which is verified by density functional theory（DFT）simulation and could be attributed to the great difference in the chemical enhancement between non-bridging and bridging BDT molecules.Combined with the trajectory of nanoparticles,we reveal the correlations between the mechanical force alterations and the locations of nanoparticles in live cells.Furthermore,we achieve visualization of the dynamic alterations of endocytic force at multiple locations and establish a direct criterion to discriminate between cancer cells and normal cells.These findings illustrate the dynamics of the endocytosis process from the viewpoint of mechanical force and provide valuable information to assist in the design of the control of drug release,the nanomachines,and the nanomotor.