Research
1. Single-molecule detection and sequencing by plasmonic nanopores.
Because proteins cannot be amplified, current protein analysis and sequencing relies on mass spectroscopy that generally needs 1 billion copies of the proteins. The low sensitivity of mass spectroscopy leads to a huge challenge in detection of low-abundance proteins in human biofluids and thus spurs extensive research interests in single-molecule protein sequencing. Jian-an developed a plasmonic nanopore system by electro-plasmonic trapping of a gold nanoparticle in a gold nanopore to generate single SERS hot spot. The nanopore was so sensitive and localized that it not only distinguished single DNA bases in single single-strand DNA [1] but also discriminated single amino acid residue in single polypeptide [2]. In addition to the sub-molecular resolution, the plasmonic nanopre system has demonstrated single-molecule detection of 10 different types of amino acids by their Raman spectra [2], which has paved a completely new way to single-molecule protein sequencing. To apply the nanopore system to single-molecule sequencing, a microfluidic method will be integrated to stretch the DNA or protein molecules and slow down their passage through the nanopore.
Related works:
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J.A. Huang et al., SERS discrimination of single DNA bases in single oligonucleotides by electro-plasmonic trapping, Nature Communications 10, 5321 (2019)
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J.A. Huang*et al., Multiplex characterization of single amino acid residue in polypeptide by single SERS hot spot, Angewandte Chemie International Edition, 59, 11423-11431 (2020)
2. Single-cell analysis by plasmonic nanotubes. Although sensitive single-cell analysis approaches have been developed, they need cell lysis to extract the cytosolic contents, which provide static information only at a single snapshot in time. A plasmonic nanotube system prepared by coating gold layer on polymer nanotube array on a silicon nitride membrane allowed tight wrapping of cell membrane on them, which thus could electroporate single cell membrane with low voltage and high cell viability. The nanotube allowed continuous extraction and real-time SERS spectroscopic analysis of cytosolic molecules of living cells [1]. Meanwhile, platform could deliver single nanoparticle into living cells on demand [2], solving the long-standing problem of nanoparticle aggregation by endocytosis in studies of single-cell intracellular mechanism. The nanotube system will be used in continuous extraction of selected live cancer cells to study influence of local environment to the cancer cell development.
Related works:
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V. Caprettiniet al., Enhanced Raman investigation of cell membrane and intracellular compounds by 3D plasmonic nanoelectrode arrays, Advanced Science 5 (12), 1800560 (2018)
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J.A. Huang et al., On-Demand Intracellular Delivery of Single Particles in Single Cells by 3D Hollow Nanoelectrodes, Nano Letters, 19 (2), 722-731(2019)
3. Biomarker detection in biofluid by plasmonic nanopillars. Despite of the single-molecule sensitivity, SERS based on nanoparticles suffered from signal irreproducibility that hindered its application to practical biosensing. Jian-an's doctoral work developed plasmonic nanopillars that exhibited propagating surface plasmon to generate wide-range hot spot for stable and reproducible SERS detection of double-strand DNA [1]. Consequently, he and his colleagues embedded the nanopillars in a microfluidic channel to demonstrate quantitative detection of DNA at different concentrations [2] and further real-time monitoring of chemical reactions [3]. The microfluidic nanopillar system will be functionalized with capturing ligands to capture and quantify the protein biomarkers in human biofluids, such as serum and sweat.
Related works:
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JA Huang et al., Ordered Ag/Si nanowires array: wide-range surface-enhanced Raman spectroscopy for reproducible biomolecule detection, Nano Letters, 13 (11), 5039–5045 (2013)
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YQ Zhao et al., Quantitative analysis of multiplex-components and double stranded DNA by wide-range surface-enhanced Raman spectroscopy based on ordered Ag/Si nanowire arrays, Journal of Materials Chemistry A, 2, 10218-10224 (2014)
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YQ Zhao et al., Plasmonic nanopillar array embedded microfluidic chips: an in situ SERS monitoring platform, Journal of Materials Chemistry A, 3, 6408-6413 (2015)