Solid/liquid-interface-dependent synthesis and immobilization of copper-based particles nucleated by X-ray-radiolysis-induced photochemical reaction.

X-ray-radiolysis-induced photochemical reaction of a liquid solution enables the direct synthesis and immobilization of nano/micro-scale particles and their aggregates onto a desired area. As is well known, the synthesis, growth and aggregation are dependent on the pH, additives and X-ray irradiation conditions. In this study, it was found that the topography and composition of synthesized particles are also dependent on the types of substrate dipped in an aqueous solution of Cu(COOCH3)2 in the X-ray-radiolysis-induced photochemical reaction. These results are attributed to the fact that a secondary electron induced by the X-ray irradiation, surface or interface on which the particles are nucleated and grown influences the particle shape and composition. This study will shed light on understanding a novel photochemical reaction route induced under X-ray irradiation. The development of this process using the X-ray-radiolysis-induced photochemical reaction in aqueous liquids enables us to achieve the rapid and easy operation of the synthesis, growth and immobilization of special nano/micro-scale complex materials or multifunctional composites.

Controllability of cupric particle synthesis by linear alcohol chain number as additive and pH control in cupric acetate solution using X-ray radiolysis.

Synthesis and immobilization of caltrop cupric particles onto a Si substrate using X-ray radiolysis directly from a liquid solution of Cu(COOCH3)2 is demonstrated. Caltrop cupric oxide particles are formed in the X-ray radiolysis of aqueous solutions of Cu(COOCH3)2, which also contain methanol, ethanol, 2-propanol or 1-propanol as ^\bulletOH scavenger. The blade lengths of the caltrop particles are dependent on the alcohol chain length. In particular, it was found that an alkyl alcohol whose chain length is longer than four is unable to synthesize any particles in aqueous solutions of Cu(COOCH3)2 in X-ray radiolysis. These results are attributed to the alkyl alcohol chain length influencing the rate of reaction of radicals and determines the solvable ratio of its alcohol into water. In addition, it was found that the synthesized particle geometric structure and composition can also be controlled by the pH of the aqueous solution in the X-ray radiolysis. This study may open a door to understanding and investigating a novel photochemical reaction route induced under X-ray irradiation. The development of the X-ray radiolysis process enables us to achieve the rapid and easy process of synthesis and immobilization of higher-order nano/microstructure consisting of various materials.

Rapid detection of hypnotics using surface-enhanced Raman scattering based on gold nanoparticle co-aggregation in a wet system.

Sensitive detection of drugs using a method with high qualification capability is important for forensic drug analysis. Vibrational spectroscopy is a powerful screening technique because it can provide detailed structural information of the compounds included in samples with simple experimental protocols. Among various spectroscopic techniques, surface enhanced Raman scattering (SERS) spectroscopy has attracted enormous attention owing to its ultra-high sensitivity. In this study, we developed a method for rapid detection of hypnotics using SERS with gold nanoparticle co-aggregation in a wet system. The developed method required a simple analytical protocol. This enabled rapid analysis with high stability and repeatability. We analyzed various hypnotics (19 types including benzodiazepines and nonbenzodiazepines) to investigate the structure-spectrum relationship. As a proof of concept for application to real crime samples, simulated spiked beverages containing one hypnotic (etizolam, flunitrazepam, zolpidem, or zopiclone) were analyzed. Diluting the beverage samples decreased the matrix effect and allowed for detection of these hypnotics. Except for flunitrazepam, strong signals were observed for all hypnotics, and the estimated lower limit of detection was 50 ppm in apple drink. The developed approach is a rapid method for screening analysis of hypnotics with low sample requirements.

Rapid detection of synthetic cannabinoids in herbal highs using surface-enhanced Raman scattering produced by gold nanoparticle co-aggregation in a wet system.

Synthetic cannabinoids (SCs) are a major category of new psychoactive substances that are frequently distributed after addition to plants. To date, various SCs with small differences in their chemical structures have prevailed in the illegal drug market. Thus, the development of a method for rapid detection with high discrimination capability is critically important for the forensic field. Vibrational spectroscopy is a possible analytical technique for this purpose because it can sensitively reflect differences among chemical structures. In this study, we applied surface-enhanced Raman scattering (SERS) with gold nanoparticle co-aggregation in a wet system to plant samples containing SCs. The experimental protocol used was simple and involved only mixing of the sample with several other solutions. It was possible to detect SERS spectra from various stock solutions of SCs by this method. The method was then applied to street samples containing SCs. Some of the plant samples containing SCs did not produce significant SERS signals even though stock solutions of the same SCs did produce SERS spectra. We investigated the reason for this discrepancy and speculated that the solubility in aqueous solutions was a factor determining whether a significant SERS signal could be detected or not. According to this hypothesis, minimal sample pre-treatment methods were applied. This allowed for the detection of SERS spectra from the examined plant samples. The developed approach is a powerful method for screening analysis of SCs in plant fragments.

Caltrop particles synthesized by photochemical reaction induced by X-ray radiolysis.

X-ray radiolysis of a Cu(CH3COO)2 solution was observed to produce caltrop-shaped particles of cupric oxide (CuO, Cu2O), which were characterized using high-resolution scanning electron microscopy and micro-Raman spectrometry. X-ray irradiation from a synchrotron source drove the room-temperature synthesis of submicrometer- and micrometer-scale cupric oxide caltrop particles from an aqueous Cu(CH3COO)2 solution spiked with ethanol. The size of the caltrop particles depended on the ratio of ethanol in the stock solution and the surface of the substrate. The results indicated that there were several synthetic routes to obtain caltrop particles, each associated with electron donation. The technique of X-ray irradiation enables the rapid synthesis of caltrop cupric oxide particles compared with conventional synthetic methods.

Application of stealth nanobeacon for traceability assurance in pharmaceutical tablets via surface-enhanced Raman scattering during the tablet coating process.

Microtaggant technologies for on-dose authentication have garnered significant interest for use in the anti-counterfeit activities and traceability of pharmaceutical dosage forms. Previously, we proposed a stealth nanobeacon (NB) comprising self-assembled colloidal gold nanoparticles with reporter molecules that demonstrated characteristic surface-enhanced Raman scattering (SERS) activity. However, the integration of such microtaggants into standard production lines remains underexplored. In this study, we demonstrate the incorporation of NB into tablet coatings using a simple mixing method with conventional coating solutions. Rapid and discernible SERS responses from the NB-coated tablets were observed in response to laser excitation at 785 nm for 0.1s, implying that it is an advanced and efficient method for counterfeit detection. In addition, the SERS intensity of NB increased with coating time, suggesting that NB can be used as a tracer for the real-time monitoring of coating thickness. Furthermore, NB-coated tablets were indistinguishable from NB-free tablets, even during colorimetric analysis. These results suggest that the NB possesses stealth properties and can be easily incorporated into counterfeit detection products.

Physical stability of stealth nanobeacon using surface-enhanced Raman scattering for anti-counterfeiting and monitoring medication adherence: Deposition on various coating tablets.

Microtaggant technologies can encode individual numbers on coating tablet to authenticate pharmaceutical products and, therefore, combat the global spread of falsified medicine. In this study, a novel microtaggant, stealth nanobeacon (NB), with surface-enhanced Raman scattering (SERS) activity was applied to various coating tablets and its physical stability was evaluated. The NBs were composed of a reporter molecule (AH, adenine hydrochloride) and prepared with different sizes of gold nanoparticles (AuNPs). The NBs were directly deposited on the surface of various model coatings (e.g., hydroxypropyl cellulose, hydroxypropyl methyl cellulose, Eudragit® RS30D, ethyl cellulose). To investigate physical stability of the NB on the coating tablets, SERS spectra of the NB after friability test and acceleration test (store at 75% RH, 40 °C) were evaluated using a portable Raman spectrometer. After the friability test, there was no significant decrease in the peak intensity of the SERS signal (PH) for authentication in all samples. In the acceleration test, the SERS signals of the samples were attenuated, but sufficient SERS signal intensity (PH > 70) was maintained in the seven types of coating for authentication. These results demonstrate that the microtaggant NB has the potential to be used for a wide range of coating tablets.

[Microtaggant Technology for Ensuring Traceability of Pharmaceutical Formulations: Potential for Anti-counterfeiting Measures, Distribution and Medication Management].

The globalization of drug trade has led to the increased production of falsified medicines. In addition, poor medication adherence increases the costs of healthcare. The need to manage medication has given rise to marketing of highly functional networked digital medicine. Therefore, a growing need has emerged to ensure the traceability of pharmaceutical products from shipment to patient distribution. Microtaggant technologies that can encode individual numbers on pharmaceutical products are expected to serve achieving this goal. Taggants are a class of materials that can be applied to an object to make it identifiable, like barcodes and holograms. Since the smaller size of microtaggant make it invisible to naked eyes, it is more difficult to reverse-engineer than conventional taggants. The U.S. Food and Drug Administration (FDA) has established guidelines for the use of microtaggants. Many studies have explored the use of various analytical technologies and materials as the microtaggants. However, the advantages and disadvantages of each method have not been established yet. In this review, recent research on the use of microtaggants for anti-counterfeiting is summarized and compared to current anti-counterfeiting technologies with spectrographic methods, distribution management systems with barcodes, and medication management systems with sensor devices. We also discuss the microtaggants implementation costs and security level.

Physically unclonable functions taggant for universal steganographic prints.

Counterfeiting of financial cards and marketable securities is a major social problem globally. Electronic identification and image recognition are common anti-counterfeiting techniques, yet they can be overcome by understanding the corresponding algorithms and analysis methods. The present work describes a physically unclonable functions taggant, in an aqueous-soluble ink, based on surface-enhanced Raman scattering of discrete self-assemblies of Au nanoparticles. Using this stealth nanobeacon, we detected a fingerprint-type Raman spectroscopy signal that we clearly identified even on a business card with a pigment mask such as copper-phthalocyanine printed on it. Accordingly, we have overcome the reverse engineering problem that is otherwise inherent to analogous anti-counterfeiting techniques. One can readily tailor the ink to various information needs and application requirements. Our stealth nanobeacon printing will be particularly useful for steganography and provide a sensitive fingerprint for anti-counterfeiting.

Gold Nanoparticles Enhance EGFR Inhibition and Irradiation Effects in Head and Neck Squamous Carcinoma Cells.

Cetuximab, an epidermal growth factor receptor inhibitor (EI), is currently the only targeted molecular therapy used in combination with radiotherapy for head and neck squamous cell carcinoma (HNSCC). Gold nanoparticles (AuNPs) are expected to enhance radiotherapy effects in cancers. To investigate whether AuNPs combined with AG1478, an EI, enhanced irradiation effects on HNSCC cells, we first examined AG1478 adsorption on AuNP surfaces, using surface-enhanced Raman scattering, which indicated an adsorption equilibrium of AG1478 to AuNPs. We then used transmission electron microscopy to find internalization rates of AuNP alone and AuNP+AG1478; we found that intracellular uptake of AuNP alone and AuNP+AG1478 did not significantly differ. We compared cell numbers, proliferation, apoptosis, and migration between control cells and those treated with or without 60 nm AuNP (1.0 nM), AG1478 (0.5 µM), and irradiation (4 Gy). We found that AuNP+AG1478 inhibited proliferation more than AG1478 alone; the combination of irradiation+AuNP+AG1478 significantly reduced total cell numbers compared with the combination of irradiation+AuNP; AuNP+AG1478 increased apoptotic reaction to irradiation; the combinations of AuNP+AG1478 and irradiation+AuNP induced more apoptosis than AG1478+irradiation. Whereas AuNP+AG1478 enhanced cytotoxicity in human HNSCC cells by inhibiting proliferation, irradiation+AuNP enhanced cytotoxicity by inducing apoptosis.

Au nanorod arrays tailored for surface-enhanced Raman spectroscopy.

We have demonstrated surface-enhanced Raman spectroscopy (SERS) on arrays of Au nanorods aligned in line by a dynamic oblique deposition technique. For light polarized along the major axes of the nanorods, the plasma resonance of the Au nanorods has been tuned to a wavelength suitable for Raman spectroscopy. Raman scattering on the discrete nanorods is significantly enhanced compared with that on semicontinuous Au films. Since the preparation process is physically bottom-up, it is robust in its selection of the materials and is useful for providing SERS sensors at low cost.

Ag nanorod arrays tailored for surface-enhanced Raman imaging in the near-infrared region.

Using a dynamic oblique angle deposition technique, we demonstrate the direct formation of Ag nanorods with quasi-parallel major axes on a template layer of oxide having a strongly anisotropic surface morphology. The optical properties of the nanorods are tuned by varying the deposition conditions without any pre- or post-treatment, and the resulting Ag nanorod arrays exhibit high surface-enhanced Raman scattering (SERS) activity. In addition to high macroscopic uniformity over a large area, our nanorod arrays contain a high density of isolated nanorods. Using the optimum Ag nanorod arrays, the SERS imaging of the microdroplets of a rhodamine 6G solution is successfully demonstrated. The space resolution of the imaging is of the order of at least a few µm. These features are suitable for the SERS imaging of biomaterials.