The Research Of Individual Au-Cube Based Plasmonic Nanoprobe For MicroRNA Detection

Recently, detection of cancer biomarkers, such as proteins, DNA and RNA, has been considered as an accurate and effective method in cancer diagnosis. Among all the biomarkers, MicroRNAs(miRNAs), as a significant tumor biomarker, is of vital importance for the lung cancer’s diagnosis. MiRNA205 has been confirmed overexpression in serum and sputum of lung cancer patients. Over the past decades, a variety of analytical methods have been used to detect oligonucleotides. Surface plasmon resonance(SPR) scattering signals of noble mental nanoparticles, especially gold(Au) and silver(Ag), is becoming an effective way of oligonucleotides detection due to its unique optical properties, positional accuracy, nontoxicity and real-time monitoring. So that we developed a novel and label-free biosensor based on DNA modified nanocubes using localized surface plasmon resonance(LSPR) technology to realize a real-time monitoring.In this work, we firstly synthesis the gold nanocubes(AuNCs) of edge length 50 ± 3 nm by following a seed-mediated growth approach in aqueous solution and characterized their specific morphology and optical properties by UV-vis, TEM and SEM measurements, respectively. Then the AuNCs were absorbed on the surface of the ITO slide physically and modified with a single strand DNA which can be matched with MicroRNA205. At last, hybridization processes between the nanobiosensor with the label-free target mi RNA was real-time monitored by the SPRS spectroscopy taken by dark-field microscopy(DFM) at single-nanoparticle level and a red shift of SPRS spectra can be observed. The limit of detection of single nanocube based biosensor was up to 10 pM.In order to get an accurate characterization of single nanoparticle’s SPR signal properties, we need to combine high resolution optical microscope and spectrometer, which put forward a new requirement for the acquisition of opitical signals. Presently, the SPR signal was 16 bits black and white images obtained by full array acquisition mode. To read out the effective spectrum data from the images quickly, we developed an image processing software to improve the work efficiency and provide a reliable algorithm to analyze the relationship between signal’s peak position and the corresponding material concentration.Moreover, we also use gold nanoparticles with different shapes as templates to prepare cavity silica shell with different structure.