Fabrication Of 3D Si-based Micro/nano-arrays Structure For Specific Applications In Mass Spectrometry

The occurrence of many diseases is related to genetic defects.Therefore,investigations on the human genome have become more and more intensive in the related scientific research.With the completion of human genome sequencing,gene detection technology has been further developed.The application of Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry(MALDI-TOF MS)in gene detection has drawn wide attention,due to its high-throughput,low-cost and fast response.However,MALDI-TOF MS technology is still inadequate for detecting nucleic acids,including the insufficient detection resolution and low intensity in response signals.The strategies to improve the performances of MALDI-TOF MS are mainly focused on the optimization of MS and selection of matrixes,while the attention on target plates,commonly used for supporting the samples and matrixes,needs to be further strengthened.The three-dimensional(3D)noble metal semiconductor composite micro/nanoarrays is expected to be used as a potential target plate to improve the performance of MS in the gene detection,due to the structural advantages including high specific surface area and uniform morphologies,unique Physical and chemical properties,and feasible fabrication by mature micro/nano processing technology.Therefore,in this thesis,3D noble metal semiconductor composite target plates with different micro/nanoarray structures were designed and fabricated to demonstrate the corresponding applications to the nucleic acid detection by MALDI-TOF MS,through which the improved detection sensitivity and resolution were accomplished compared to using the commercial stainless-steel target plate.Furthermore,the relevant MALDI ionization mechanisms were investigated in details both experimentally and theoretically.In a summary,the main investigation contents are as follows:Firstly,the fabrication of Au/Si composite mcriorods array(Au/Si MRs)structure as the target plate of MS for nucleic acid detection.Initially,the Au/Si MRs structure was prepared on Si substrate using nanosphere self-assembly technology followed by inductively coupled plasma(ICP)etching,and magnetron sputtering technologies.Subsequently,the photolithography and scribing process were employed to prepare the target plates with the Au/Si MRs structure on the top surface of the plate,on which the matrix and nucleic acid were introduced by dripping.Then,the nucleic acid was tested by MALDI-TOF MS.The experimental results well demonstrated the effective nucleic acid detection with improved intensity and resolution of the MS signals by the Au/Si MRs structure target plate,compared with those using the commercial stainless-steel target plate.The corresponding performance improvement mechanisms based on MALDI ionization processes were further investigated by relevant experimental characterizations and theoretical calculations using finite difference time domain(FDTD)method.The micro/nanoarray structure in the target plates would facilitate not only the uniform distribution of the matrix and samples on the plate,but also the confinement of the incident light into the gaps of the noble metal composite nanorods array,generating a "gap effect",thus the surface plasmon resonance(SPR)effect around the Au nanoparticles.Therefore,the ionization of the matrix and the samples were synergistically promoted resulting in the enhanced MALDI-TOF MS detection for nucleic acid samples.Secondly,the Fabrication of Au/TiO2/Si-based network composite nanoarrays(Au/TiO2/Si NAs)structure as the target plate of MS for nucleic acid detection.Initially,We use the nanosphere self-assembly technology、thermal annealing、ICP etching、and sputtering technologies to prepared the Au/TiO2/Si NAs structure on the silicon wafer.we found that the structure have great characteristics,through acquiring the morphology information and element distribution by the SEM and TEM,and observing the optical characteristic of the nanoarray structure.For the structure could be used in the gene detection,the photolithography and scribing process were employed to prepare the target plates with the Au/TiO2/Si NAs structure on the top surface of the plate,on which the matrix and nucleic acid were introduced by dripping.Then,the nucleic acid was tested by MALDI-TOF MS.Experimental results show that the intensity and resolution of the MS signals be improved by used the target plate with Au/TiO2/Si NAs structure,which maybe attribute to the structural advantage of the plate and the photocatalytic effect of the TiO2 accelerated samples ionization.The photocatalytic effect have been strengthened for the SPR induced by Au nanoparticle,that would be ulteriorly enhanced the ionization efficiency of the matrix and nucleic acid.The work of this chapter proved that the Si based TiO2 micro/nano arrays has good application potential in the MALDI MS.In summary,two kinds of 3D Si-based composite target plates with micro/nanoarray structures produced by micro/nano fabrication technologies were well demonstrated in the application of MALDI-MS for nucleic acid detections with improved sensitivity and resolution.This work provides experimental and theoretical basis for further application of Si-based target plates for highly sensitive detection in MALDI-TOF Mass Spectrometry.