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.

Ag-coated Au nanoparticle (NP)-embedded silica nanospheres (SiO2@Au@Ag NSs) were prepared using three different Au NPs of 2.5, 7 and 15 nm diameter to investigate their optical properties.

Antibody-conjugated nanoparticles (NPs) have attracted great attention in diagnostic and therapeutic applications due to their high sensitivity and specificity for biotargets, as well as their wide applicability. Unfortunately, these features are significantly affected by antibody conjugation methods in terms of conjugation efficiency, orientation of the target binding site in the antibody, and denaturation during chemical conjugation reactions. Furthermore, the number of conjugated antibodies on each NP and the overall targeting efficacy are critical factors for a quantitative bioassay with antibody-conjugated NPs. Herein, we report a versatile and oriented antibody conjugation method using copper-free click chemistry. Moreover, the number of conjugated antibodies and their binding capacity were quantitatively and experimentally evaluated using fluorescently-labeled antibodies and antigens. The strong binding capability of antibody-conjugated NPs prepared using the copper-free click chemistry-based conjugation strategy was 8 times superior to the binding capability seen following the use of the EDC/NHS-coupling method. Additionally, the versatility of the developed antibody conjugation method was also demonstrated by conjugation of the antibody to three kinds of silica-encapsulated NPs.

Surface-enhanced Raman scattering (SERS) spectroscopy is attractive in various detection analysis fields. However, the quantitative method using SERS spectroscopy remains as an area to be developed. The key issues in developing quantitative analysis methods by using SERS spectroscopy are the fabrication of reliable SERS-active materials such as nanoparticle-based structures and the acquisition of the SERS signal without any disturbance that may change the SERS signal intensity and frequency. Here, the fabrication of seamless multilayered core–shell nanoparticles with an embedded Raman label compound as an internal standard (MLRLC dots) for quantitative SERS analysis is reported. The embedded Raman label compound in the nanostructure provides a reference value for calibrating the SERS signals. By using the MLRLC dots, it is possible to gain target analyte signals of different concentrations while retaining the Raman signal of the internal standard. The ML4‑BBT dots, containing 4-bromobenzenethiol (4-BBT) as an internal standard, are successfully applied in the quantitative analysis of 4-fluorobenzenethiol and thiram, a model pesticide. Additionally, ratiometric analysis was proved practical through normalization of the relative SERS intensity. The ratiometric strategy could be applied to various SERS substrates for quantitative detection of a wide variety of targets.

No abstract

We designed a β-CD dimer on silver nanoparticles embedded with silica nanoparticles (Ag@SiO2 NPs) structure to detect polycyclic aromatic hydrocarbons (PAHs). Silica NPs were utilized as a template for embedding silver NPs to create hot spot structures and enhance the surface-enhanced Raman scattering (SERS) signal, and a thioether-bridged dimeric β-CD was immobilized on Ag NPs to capture PAHs. The assembled Ag NPs on silica NPs were confirmed by TEM and the presence of β-CD dimer on Ag@SiO2 was confirmed by UV-vis and attenuated total reflection-Fourier transform infrared spectroscopy. The β-CD dimer@Ag@SiO2 NPs were used as SERS substrate for detecting perylene, a PAH, directly and in a wide linearity range of 10−7 M to 10−2 M with a low detection limit of 10−8 M. Also, the β-CD dimer@Ag@SiO2 NPs exhibited 1000-fold greater sensitivity than Ag@SiO2 NPs in terms of their perylene detection limit. Furthermore, we demonstrated the possibility of detecting various PAH compounds using the β-CD dimer@Ag@SiO2 NPs as a multiplex detection tool. Various PAH compounds with the NPs exhibited their distinct SERS bands by the ratio of each PAHs. This approach of utilizing the assembled structure and the ligands to recognize target has potential for use in sensitive analytical sensors.

It is very challenging to accurately quantify the amounts of amyloid peptides Aβ40 and Aβ42, which are Alzheimer's disease (AD) biomarkers, in blood owing to their low levels. This has driven the development of sensitive and noninvasive sensing methods for the early diagnosis of AD. Here, an approach for the synthesis of Ag nanogap shells (AgNGSs) is reported as surface‐enhanced Raman scattering (SERS) colloidal nanoprobes for the sensitive, selective, and multiplexed detection of Aβ40 and Aβ42 in blood. Raman label chemicals used for SERS signal generation modulate the reaction rate for AgNGSs production through the formation of an Ag‐thiolate lamella structure, enabling the control of nanogaps at one nanometer resolution. The AgNGSs embedded with the Raman label chemicals emit their unique SERS signals with a huge intensity enhancement of up to 107 and long‐term stability. The AgNGS nanoprobes, conjugated with an antibody specific to Aβ40 or Aβ42, are able to detect these AD biomarkers in a multiplexed manner in human serum based on the AgNGS SERS signals. Detection is possible for amounts as low as 0.25 pg mL−1. The AgNGS nanoprobe‐based sandwich assay has a detection dynamic range two orders of magnitude wider than that of a conventional enzyme‐linked immunosorbent assay.

Morphology control of the surface of a nanostructure is a key issue in modulating its surface plasmon resonance and scattering properties. Here, we studied the effect of alkylamines on morphology control during the one-step fabrication of silver nanoshells (NSs) for highly enhanced Raman scattering. Various types of alkylamines were used to study the effects of chain length, existence of hydroxyl groups, and degree of alkyl chains on the surface morphology of silver NSs. The alkylamines influenced the silver ion reduction and the growth of silver domains, resulting in distinctive morphology changes. The optical properties of the silver NSs of different surface morphologies were characterized by surface-enhanced Raman spectra. Especially, when long alkylamines were used, intense and uniform surface-enhanced Raman scattering signals were obtained at the visible and near-infrared (NIR) region, and their enhancement factor was ∼107. To detect cancer biomarkers in vivo, as a feasibility test, silver NSs were modified to highly NIR-active nanoprobes and successfully applied to detect colon cancer without causing nonspecific interactions. Our one-step fabrication method of silver NSs is simple and can overcome various hurdles of morphology control and can be extended to other metal nanostructures of controlled surface morphologies or shape.