Sinyoung Jeong

Single-step and rapid growth of silver nanoshells as SERS-active nanostructures for label-free detection of pesticides.

We explored a single-step approach for the rapid growth of Ag nanoshells (Ag NSs) under mild conditions. Without predeposition of seed metals, a uniform and complete layer of Ag shells was rapidly formed on silica core particles within 2 min at 25 °C via single electron transfer from octylamine to Ag(+) ions. The size and thickness of the Ag NSs were effectively tuned by adjusting the concentration of silica nanoparticles (silica NPs) with optimal concentrations of AgNO3 and octylamine. This unusually rapid growth of Ag NSs was attributed to a significant increase in the reduction potential of the Ag(+) ions in ethylene glycol (EG) through the formation of an Ag/EG complex, which in turn led to their facile reduction by octylamine, even at room temperature. A substantial enhancement in the surface-enhanced Raman scattering (SERS) of the prepared Ag NSs was demonstrated. The Ag NSs were also utilized as SERS-active nanostructures for label-free detection of the pesticide thiram. The Ag NS-based SERS approach successfully detected thiram on apple peel down to the level of 38 ng/cm(2) in a label-free manner, which is very promising with respect to its potential use for the on-site detection of residual pesticides.

Target-specific near-IR induced drug release and photothermal therapy with accumulated Au/Ag hollow nanoshells on pulmonary cancer cell membranes.

Au/Ag hollow nanoshells (AuHNSs) were developed as multifunctional therapeutic agents for effective, targeted, photothermally induced drug delivery under near-infrared (NIR) light. AuHNSs were synthesized by galvanic replacement reaction. We further conjugated antibodies against the epidermal growth factor receptor (EGFR) to the PEGylated AuHNS, followed by loading with the antitumor drug doxorubicin (AuHNS-EGFR-DOX) for lung cancer treatment. AuHNSs showed similar photothermal efficiency to gold nanorods under optimized NIR laser power. The targeting of AuHNS-EGFR-DOX was confirmed by light-scattering images of A549 cells, and doxorubicin release from the AuHNSs was evaluated under low pH and NIR-irradiated conditions. Multifunctional AuHNS-EGFR-DOX induced photothermal ablation of the targeted lung cancer cells and rapid doxorubicin release following irradiation with NIR laser. Furthermore, we evaluated the effectiveness of AuHNS-EGFR-DOX drug delivery by comparing two drug delivery methods: receptor-mediated endocytosis and cell-surface targeting. Accumulation of the AuHNS-EGFR-DOX on the cell surfaces by targeting EGFR turned out to be more effective for lung cancer treatments than uptake of AuHNS-EGFR-DOX. Taken together, our data suggest a new and optimal method of NIR-induced drug release via the accumulation of targeted AuHNS-EGFR-DOX on cancer cell membranes.

Fluorescence-Raman Dual Modal Endoscopic System for Multiplexed Molecular Diagnostics

Optical endoscopic imaging, which was recently equipped with bioluminescence, fluorescence, and Raman scattering, allows minimally invasive real-time detection of pathologies on the surface of hollow organs. To characterize pathologic lesions in a multiplexed way, we developed a dual modal fluorescence-Raman endomicroscopic system (FRES), which used fluorescence and surface-enhanced Raman scattering nanoprobes (F-SERS dots). Real-time, in vivo, and multiple target detection of a specific cancer was successful, based on the fast imaging capability of fluorescence signals and the multiplex capability of simultaneously detected SERS signals using an optical fiber bundle for intraoperative endoscopic system. Human epidermal growth factor receptor 2 (HER2) and epidermal growth factor receptor (EGFR) on the breast cancer xenografts in a mouse orthotopic model were successfully detected in a multiplexed way, illustrating the potential of FRES as a molecular diagnostic instrument that enables real-time tumor characterization of receptors during routine endoscopic procedures.

One-step synthesis of silver nanoshells with bumps for highly sensitive near-IR SERS nanoprobes

A seedless, one-step synthetic route to uniform bumpy silver nanoshells (AgNSs) as highly NIR sensitive SERS substrates is reported. These substrates can incorporate Raman label compounds and biocompatible polymers on their surface. AgNS based NIR-SERS probes are successfully applied to cell tracking in a live animal using a portable Raman system.

Direct Identification of On-Bead Peptides Using Surface-Enhanced Raman Spectroscopic Barcoding System for High-Throughput Bioanalysis

Recently, preparation and screening of compound libraries remain one of the most challenging tasks in drug discovery, biomarker detection, and biomolecular profiling processes. So far, several distinct encoding/decoding methods such as chemical encoding, graphical encoding, and optical encoding have been reported to identify those libraries. In this paper, a simple and efficient surface-enhanced Raman spectroscopic (SERS) barcoding method using highly sensitive SERS nanoparticles (SERS ID) is presented. The 44 kinds of SERS IDs were able to generate simple codes and could possibly generate more than one million kinds of codes by incorporating combinations of different SERS IDs. The barcoding method exhibited high stability and reliability under bioassay conditions. The SERS ID encoding based screening platform can identify the peptide ligand on the bead and also quantify its binding affinity for specific protein. We believe that our SERS barcoding technology is a promising method in the screening of one-bead-one-compound (OBOC) libraries for drug discovery.

Preparation of plasmonic magnetic nanoparticles and their light scattering properties

Fe3O4@SiO2@Au nanoparticles (NPs) that have plasmonic and magnetic properties were prepared by simple immobilization method of Au NPs to silica coated magnetic NPs. The Fe3O4@SiO2@Au exhibit 5 times higher light scattering compared to the same sized gold NPs. The experimental results were supported by the simulations.

Simultaneous Detection of EGFR and VEGF in Colorectal Cancer using Fluorescence-Raman Endoscopy

Fluorescence endomicroscopy provides quick access to molecular targets, while Raman spectroscopy allows the detection of multiple molecular targets. Using a simultaneous fluorescence-Raman endoscopic system (FRES), we herein demonstrate its potential in cancer diagnosis in an orthotopically induced colorectal cancer (CRC) xenograft model. In the model, epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) were targeted with antibody-conjugated fluorescence and surface-enhanced Raman scattering (F-SERS) dots. FRES demonstrated fast signal detection and multiplex targeting ability using fluorescence and Raman signals to detect the F-SERS dots. In addition, FRES showed a multiplex targeting ability even on a subcentimeter-sized CRC after spraying with a dose of 50 µg F-SERS dots. In conclusion, molecular characteristics of tumor cells (EGFR in cancer cell membranes) and tumor microenvironments (VEGF in the extracellular matrix) could be simultaneously investigated when performing a colonoscopy.

Highly sensitive and reliable SERS probes based on nanogap control of a Au–Ag alloy on silica nanoparticles

We developed highly sensitive surface-enhanced Raman scattering (SERS) probes based on SiO2@Au@Ag nanoparticles (NPs) using the Ag growth onto Au NP seeds method. The SiO2@Au@Ag NPs were synthesized by reducing Ag ions under mild conditions (ascorbic acid) and using the structure-directing agent polyvinylpyrrolidone (PVP). SERS activities of the NPs were tuned by adjusting AgNO3 concentration, resulting in the growth of the Ag shell on the surface of the Au NP seeds and the formation of narrow gaps between two Ag NPs on the surface of the probes. The NPs exhibited strong Raman signals originating from a highly enhanced E-field at the gaps. The SiO2@Au@Ag NPs exhibited a low limit of detection (LOD) value of 2.4 nM for ATP, which proves that they are highly sensitive probes. Moreover, reproducible Raman signals of the SiO2@Au@Ag NPs toward ATP were obtained in batch-to-batch experiments which is very promising for potential use in on-site detection.

Fine size-regulation of nanocrystalline anatase-TiO2via sol–gel synthesis and subsequent phase transformation by calcination

Nanocrystalline TiO2 particles were prepared via the sol–gel process. The particle size and nanostructure of the TiO2 sol were controlled through the ageing process accompanied by hydrolysis–polycondensation. The resultant TiO2 particles were analysed by BET, HR-TEM, PSA, TGA, turbidity, XRD, and zeta potential analyses. The TiO2 size increased with increasing ageing time and reaction temperature. A phase transformation from anatase to rutile occurred with heat treatment at 500 °C. The phase transformation is strongly influenced by the primary particle sizes of TiO2, which were characterised via XRD and Raman spectroscopic analyses.

A fast and reliable readout method for quantitative analysis of surface-enhanced Raman scattering nanoprobes on chip surface

Surface-enhanced Raman scattering techniques have been widely used for bioanalysis due to its high sensitivity and multiplex capacity. However, the point-scanning method using a micro-Raman system, which is the most common method in the literature, has a disadvantage of extremely long measurement time for on-chip immunoassay adopting a large chip area of approximately 1-mm scale and confocal beam point of ca. 1-μm size. Alternative methods such as sampled spot scan with high confocality and large-area scan method with enlarged field of view and low confocality have been utilized in order to minimize the measurement time practically. In this study, we analyzed the two methods in respect of signal-to-noise ratio and sampling-led signal fluctuations to obtain insights into a fast and reliable readout strategy. On this basis, we proposed a methodology for fast and reliable quantitative measurement of the whole chip area. The proposed method adopted a raster scan covering a full area of 100 μm × 100 μm region as a proof-of-concept experiment while accumulating signals in the CCD detector for single spectrum per frame. One single scan with 10 s over 100 μm × 100 μm area yielded much higher sensitivity compared to sampled spot scanning measurements and no signal fluctuations attributed to sampled spot scan. This readout method is able to serve as one of key technologies that will bring quantitative multiplexed detection and analysis into practice.