KOSEN 한인과학기술자네트워크

Smart Nanostructures with Plasmonic Functionalities for Biomedical and Environmental Applications
 






Plasmon Resonance Energy Transfer (PRET) Probes for In Vivo Molecular Imaging



 We reported the first observation of quantized plasmon quenching dips in the resonant Rayleigh scattering light by plasmon resonance energy transfer (PRET) from a single metallic nanoparticle to adsorbed metalloproteins cytochome c in journal Nature Methods. PRET permits to develop an innovative label-free biomolecular absorption nanospectroscopy with sub-100 nm spatial resolution and ultrahigh molecular sensitivity. Now we are developing the multiplexed nanoplasmonic PRET probes that allow in-vivo nanospectroscopic molecular imaging of metalloproteins in living cells.











Single Nanoplasmonic Probes for Ultra-sensitive and Selective Metal Ion Detection
 

 Since metal ions play a vital role in the catalytic function of many enzymes in gene regulation and in free radical homeostasis, elucidation of the spatio-temporal distribution and functional states is critical for understanding the molecular and transport mechanisms in cell biology and medicine. However, current techniques are based on organic fluorophores and chromophores, which are limited by kinetic stability, sensitivity, and water-solubility. We pioneered innovative metal ion detection method based on Metal-Ligand (ML) Coordination Chemistry and Plasmonic Resonance Energy Transfer (PRET) will allow (1) nanoscale spatial-resolution via a 50 nm single gold nanoplasmonic probe (GNP), (2) a high sensitivity (based on the quantitative quenching spectra by the energy transfer from GNP to the conjugated ML) due to the increased optical cross section along with the ability to resolve a single nanoplasmonic scattering, and (3) an extreme selectivity by dual refining processes which are the highly selective recognition of target ion by its counterpart ligands as well as selective energy transfer from GNP (donor) to the conjugated ML (acceptor) occurring onlyif the frequency matching condition between them satisfies.









Surface-enhanced Raman Spectroscopy (SERS) Probes (Standalone & Array)
 

 Techniques for single molecular level detection and recognition of biomolecules are important in medical, defense, and environmental sensing applications. In this field, optical methods based on spectroscopy have been predominant owing to their non-destructive nature. Especially promising methods are label-free schemes such as Raman or extinction spectroscopy. Recently these spectroscopic techniques gain reinforced interests due to technical advances in metallic nanostructures. Under optical excitations of proper frequency, a metallic nanostructure sustains a plasmon resonance that result in highly enhanced local electromagnetic fields and distinct spectral extinction characteristics. For sensing applications, the field enhancement is utilized for surface-enhanced Raman spectroscopy (SERS) and the spectral extinction characteristics are used to detect the changes in local refractive index. The plasmon resonance characteristic depends strongly on the topology of each nanostructure. The shape of the nanostructures; however, has been limited to be symmetric and/or particulate due to fabrication constraints. We develop the nanofabrication techniques and spectroscopic applications of nanostructures with unconventional shapes for ultrasensitive nanobiophotonic applications.












Innovative Bio-platform with Integrated Multiple Signal Transducer
 

 Complementary measurement modalities provide more information and better cross checks for a precise characterization of biological and chemical events than either method alone can yield. Here we demonstrate an innovative transparent submicron gap electrode for combined optical dark-field imaging and dielectric relaxation spectroscopy (DRS) measurement of amyloid-β fibrillization. Such a submicron gap electrode can be easily fabricated by using indium-tin oxide (ITO) coated glass as a transparent electrode and 50 nm polystyrene (PS) bead as a dielectric spacer. Since transparent electrode with submicron gap (< 1 µm) allows real-time observation of changes in both hydrodynamic radii and optical properties of object of interest, optical dark-field imaging and DRS measurement based on our electrode can be successfully employed for in-situ characterization of amyloid-β fibrillization. Such a dual-mode technique with the transparent submicron gap electrode may therefore prove valuable for elucidating the mechanism of amyloid fibrillization and ultimately for designing possible diagnostic methods.