Diagnosis of Tamiflu-Resistant Influenza Virus in Human Nasal Fluid and Saliva Using Surface-Enhanced Raman Scattering.

Influenza viruses cause respiratory infection, spread through respiratory secretions, and are shed into the nasal secretion and saliva specimens. Therefore, nasal fluid and saliva are effective clinical samples for the diagnosis of influenza virus-infected patients. Although several methods have been developed to detect various types of influenza viruses, approaches for detecting mutant influenza viruses in clinical samples are rarely reported. Herein, we report for the first time a surface-enhanced Raman scattering (SERS)-based sensing platform for oseltamivir-resistant pandemic H1N1 (pH1N1) virus detection in human nasal fluid and saliva. By combining SERS-active urchin Au nanoparticles and oseltamivir hexylthiol, an excellent receptor for the pH1N1/H275Y mutant virus, we detected the pH1N1/H275Y virus specifically and sensitively in human saliva and nasal fluid samples. Considering that the current influenza virus infection testing methods do not provide information on the antiviral drug resistance of the virus, the proposed SERS-based diagnostic test for the oseltamivir-resistant virus will inform clinical decisions about the treatment of influenza virus infections, avoiding the unnecessary prescription of ineffective drugs and greatly improving therapy.

Low-Temperature Vapor-Phase Synthesis of Single-Crystalline Gold Nanostructures: Toward Exceptional Electrocatalytic Activity for Methanol Oxidation Reaction.

Au nanostructures (Au NSs) have been considered promising materials for applications in fuel cell catalysis, electrochemistry, and plasmonics. For the fabrication of high-performance Au NS-based electronic or electrochemical devices, Au NSs should have clean surfaces and be directly supported on a substrate without any mediating molecules. Herein, we report the vapor-phase synthesis of Au NSs on a fluorine-doped tin oxide (FTO) substrate at 120 °C and their application to the electrocatalytic methanol oxidation reaction (MOR). By employing AuCl as a precursor, the synthesis temperature for Au NSs was reduced to under 200 °C, enabling the direct synthesis of Au NSs on an FTO substrate in the vapor phase. Considering that previously reported vapor-phase synthesis of Au NSs requires a high temperature over 1000 °C, this proposed synthetic method is remarkably simple and practical. Moreover, we could selectively synthesize Au nanoparticles (NPs) and nanoplates by adjusting the location of the substrate, and the size of the Au NPs was controllable by changing the reaction temperature. The synthesized Au NSs are a single-crystalline material with clean surfaces that achieved a high methanol oxidation current density of 14.65 mA/cm² when intimately supported by an FTO substrate. We anticipate that this novel synthetic method can widen the applicability of vapor-phase synthesized Au NSs for electronic and electrochemical devices.

Intra-nanogap controllable Au plates as efficient, robust, and reproducible surface-enhanced Raman scattering-active platforms.

Practical application of surface-enhanced Raman scattering (SERS)-active platforms requires that they provide highly uniform and reproducible SERS signals. Moreover, to achieve highly stable and consistent SERS signals, it is important to control the nanostructured gaps of SERS-active platforms precisely. Herein, we report the synthesis of gap-controllable nanoporous plates and their application to efficient, robust, uniform, and reproducible SERS-active platforms. To prepare well-defined nanoporous plates, ultraflat, ultraclean, and single-crystalline Au nanoplates were employed. The Au nanoplates were transformed to AuAg alloy nanoplates by reacting with AgI in the vapor phase. The Ag in the alloy nanoplates was then chemically etched, thus forming well-defined SERS-active nanoporous plates. For the precise control of gaps in the nanoporous plates, we investigated the alloy forming mechanism based on X-ray photoelectron spectroscopy and transmission electron microscopy analyses. According to the mechanism, the composition of Ag was tunable by varying the reaction temperature, thus making the nanostructured gaps of the porous plates adjustable. We optimized the nanoporous plates to exhibit the strongest SERS signals as well as excellent uniformity and reproducibility. The computational simulation also supports the experimental SERS signals of nanoporous plates. Furthermore, we successfully performed label-free detection of a biocide mixture (5-chloro-2-methyl-4-isothiazolin-3-one/2-methyl-4-isothiazol-3-one) up to 10 ppm using Au nanoporous plates. The adoption of single-crystalline Au nanoplates, the novel synthesis method for alloy nanoplates in the vapor phase, and the investigation of alloy forming mechanisms synergistically contributed to the formation of well-defined nanoporous plates. We anticipate that the nanoporous plates will be useful for the practical sensing of trace chemical and biological analytes.

Multivalent Antibody-Nanoparticle Conjugates To Enhance the Sensitivity of Surface-Enhanced Raman Scattering-Based Immunoassays.

Multivalent immunoprobes can improve the sensitivity of biosensors because increased valency can strengthen the binding affinity between the receptor and target biomolecules. Here, we report surface-enhanced Raman scattering (SERS)-based immunoassays using multivalent antibody-conjugated nanoparticles (NPs) for the first time. Multivalent antibodies were generated through the ligation of Fab fragments fused with Fc-binding peptides to immunoglobulin G. This fabrication method is easy and fast because of the elimination of heterologous protein expression, high degrees of antibody modifications, and covalent chemical ligation steps. We constructed multivalent antibody-NP conjugates (MANCs) and employed them as SERS immunoprobes. MANCs improved the sensitivity of SERS-based immunoassays by 100 times compared to standard antibody-NP conjugates. MANCs will increase the feasibility of practical SERS-based immunoassays.

Attomolar detection of extracellular microRNAs released from living prostate cancer cells by a plasmonic nanowire interstice sensor.

Prostate cancer (PC) is the second leading cause of cancer death for men worldwide. The serum prostate-specific antigen level test has been widely used to screen for PC. This method, however, exhibits a high false-positive rate, leading to over-diagnosis and over-treatment of PC patients. Extracellular microRNAs (miRNAs) recently provided valuable information including the site and the status of the cancers and thus emerged as new biomarkers for several cancers. Among them, miR141 and miR375 are the most pronounced biomarkers for the diagnosis of high-risk PC. Herein, we report an attomolar detection of miR141 and miR375 released from living PC cells by using a plasmonic nanowire interstice (PNI) sensor. This sensor showed a very low detection limit of 100 aM as well as a wide dynamic range from 100 aM to 100 pM for all target miRNAs. In addition, the PNI sensor could discriminate perfectly the diverse single-base mismatches in the miRNAs. More importantly, the PNI sensor successfully detected the extracellular miR141 and miR375 released from living PC cell lines (LNCaP and PC-3), proving the diagnostic ability of the sensor for PC. We anticipate that the present PNI sensor can hold great promise for the precise diagnosis and prognosis of various cancer patients as well as PC patients.