Blood Compatibility of Drug-Inorganic Hybrid in Human Blood: Red Blood Cell Hitchhiking and Soft Protein Corona.

A drug-delivery system consisting of an inorganic host-layered double hydroxide (LDH)-and an anticancer drug-methotrexate (MTX)-was prepared via the intercalation route (MTX-LDH), and its hematocompatibility was investigated. Hemolysis, a red blood cell counting assay, and optical microscopy revealed that the MTX-LDH had no harmful toxic effect on blood cells. Both scanning electron microscopy and atomic force microscopy exhibited that the MTX-LDH particles softly landed on the concave part inred blood cells without serious morphological changes of the cells. The time-dependent change in the surface charge and hydrodynamic radius of MTX-LDH in the plasma condition demonstrated that the proteins can be gently adsorbed on the MTX-LDH particles, possibly through protein corona, giving rise to good colloidal stability. The fluorescence quenching assay was carried out to monitor the interaction between MTX-LDH and plasma protein, and the result showed that the MTX-LDH had less dynamic interaction with protein compared with MTX alone, due to the capsule moiety of the LDH host. It was verified by a quartz crystal microbalance assay that the surface interaction between MTX-LDH and protein was reversible and reproducible, and the type of protein corona was a soft one, having flexibility toward the biological environment.

Development of enzyme/titanate nanosheet complex coated with molecularly imprinted polydopamine for colorimetric quercetin assay.

A novel hybrid material, which is an enzyme/inorganic nanosheet complex coated by molecularly imprinted polymer (MIP), was developed, and applied to colorimetric quercetin assay. First, an enzyme/inorganic nanosheet complex was prepared from horseradish peroxidase (HRP) enzyme and titanate nanosheet (TiOx), using electrostatic interactions between them in acetate buffer. In the next place, dopamine self-polymerization was performed in the presence of HRP/TiOx complex with quercetin as a template, to prepare MIP membrane onto the HRP/TiOx complex. After washing process, a new hybrid material, MIP-coated HRP/TiOx complex (MIP-HT) was obtained. MIP-HT adsorbed quercetin efficiently, compared with NIP-HT that is an HRP/TiOx complex coated with non-imprinted polydopamine. MIP-HT showed enzymatic activity for an oxidation reaction of guaiacol, which is a chromogenic substrate of HRP, whereas the enzymatic activity of NIP-HT was significantly suppressed. The amount of brown product, formed by the color reaction, reduced owing to the presence of quercetin in sample solution, and a good liner relationship was observed between the concentration of quercetin and the increment of absorbance at 470 nm. The investigation using several biomolecules indicates that MIP-HT has the ability to detect quercetin and its analogues with selectivity. Therefore, MIP-HT shows great promise as a new and attractive material for use in colorimetric assay of quercetin or quercetin analogues.

Toluene-sensing Properties of Mixed-potential Type Yttria-stabilized Zirconia-based Gas Sensors Attached with Thin CeO2-added Au Electrodes.

Toluene-sensing properties of mixed-potential type yttria-stabilized zirconia (YSZ)-based sensors attached with a thin CeO2-added Au sensing electrode (SE, CeO2 content: 4 - 16 mass%, thickness: 30 - 100 nm), which was fabricated by using a spin-coating method, were examined and the effects of their SE thickness and the additive amount of CeO2 on their toluene response were discussed in this study. The toluene response of the sensors attached with a 16 mass% CeO2-added Au SE increased with an increase in the SE thickness, and the sensor attached with the thickest 16 mass% CeO2-added Au SE showed the largest response, among all the sensors tested. This behavior probably arises from the increase in the number of active sites for electrochemical toluene oxidation in the CeO2-added Au SE.

Enhanced catalytic activity and thermal stability of lipase bound to oxide nanosheets.

The present study reports the effects of binding of lipase, which is an inexpensive digestive enzyme (candida antarctica lipase) that catalyzes the hydrolysis reaction and is frequently utilized for artificial synthesis of a variety of organic molecules, to titanate nanosheets (TNSs) on their biocatalytic activities and stabilities under several lipase concentrations. TNSs were prepared through a hydrolysis reaction of titanium tetraisopropoxide (TTIP) with tetrabutylammonium hydroxide (TBAOH), resulting in formation of a colorless and transparent colloidal solution including TNSs with nanometric dimensions (hydrodynamic diameter: ca. 5.6 nm). TNSs were bound to lipase molecules through electrostatic interaction in an aqueous phase at an appropriate pH, forming inorganic-bio nanohybrids (lipase-TNSs). The enzymatic reaction rate for hydrolysis of p-nitrophenyl acetate (pNPA) catalyzed by the lipase-TNSs, especially in diluted lipase concentrations, was significantly improved more than 8 times as compared with free lipase. On the other hand, it was confirmed that heat tolerance of lipase was also improved by binding to TNSs. These results suggest that the novel lipase-TNSs proposed here have combined enhancements of the catalytic activity and the anti-denaturation stability of lipase.

Time-resolved Fluorescent Detection for Glucose Using a Complex of Luminescent Layered Titanates and Enzymes.

Luminescent europium-doped layered titanates (Eu-TiOx) were synthesized and complexed with horseradish peroxidase (HRP) and glucose oxidase (GOx). The emission of a resultant Eu-TiOx/HRP/GOx complex decreased upon the addition of glucose in the presence of guaiacol. The emission decrease was dependent on the concentrations of glucose, and the detection limit for glucose was 3.1 µM. The proposed system would be promising as a new detection method for glucose.

Multicolour photochromism of colloidal solutions of niobate nanosheets intercalated with several kinds of metal ions.

Colourless and transparent colloidal solutions of niobate nanosheets intercalated with some kinds of metal ions (M-NNS, M: metal) showed quasi-reversible photochromism. Ultraviolet light irradiation of the solutions induced a change in color while maintaining the transparency, and the color change was dependent on the metal ions. The coloured solutions were bleached by exposure to an oxidizing atmosphere. This cycle could be repeated several times.

Visible-Light-Induced Activity Control of Peroxidase Bound to Fe-Doped Titanate Nanosheets with Nanometric Lateral Dimensions.

Catalytic performance of horseradish peroxidase (HRP) electrostatically adsorbed on nanometric and semiconducting Fe-doped titanate (FT) nanosheets was successfully manipulated by visible light illumination. A colloidal solution of FT with a narrow band gap corresponding to a visible light region was fabricated through a hydrolysis reaction of metals sources. HRP could be easily bound to the FT at pH = 4 through an electrostatic interaction between them, and the formed HRP-FT was utilized for the visible-light-driven enzymatic reaction. Under exposure to visible light with enough energy for band gap excitation of the FT, catalytic activity of HRP-FT was dramatically enhanced as compared with free (unbound) HRP and was simply adjusted by light intensity. In addition, wavelength dependence of an enzymatic reaction rate was analogous to an optical absorption spectrum of the FT. These results substantiated an expected reaction mechanism in which the photoenzymatic reaction was initiated by band gap excitation of FT followed by transferring holes generated in the valence band of irradiated FT to HRP. The excited HRP oxidized substrates (amplex ultrared: AUR) accompanied by two-electron reduction to regenerate the resting state. In addition, the catalytic activity was clearly switched by turning on and off the light source.

Enzyme-mimetic activity of Ce-intercalated titanate nanosheets.

Colloidal solutions of Ce-doped titanate nanosheets (Ce-TNS) with tiny dimensions (<10 nm) were fabricated through a hydrolysis reaction of titanium tetraisopropoxide and Ce(NO3)3, and their annihilation activity for reactive oxygen species (ROS) was investigated. The obtained Ce-TNS had an akin crystal structure to layered tetratitanate (Ti4O9(2-)) and Ce ions occupied interlayer space between the host layers with a negative charge. The Ce-TNS possessed a superoxide dismutase (SOD) mimetic activity for disproportionation of superoxide anion radicals (O2(-)) as target ROS. It was explained that the annihilation of O2(-) caused a valence fluctuation of Ce ions existing in the interlayer. Moreover, the activity of Ce-TNS exceeded that of CeO2 nanoparticles recently attracting much attention as an inorganic SOD mimic. The superior performance was explained mainly by a high dispersion stability of the Ce-TNS bringing about a huge reaction area. Moreover, the Ce-TNS protected DNA molecules from ultraviolet light induced oxidative damage, demonstrating effectiveness as one of the new inorganic protecting agents for biomolecules and tissues.

Morphology-selective synthesis of polyhedral gold nanoparticles: what factors control the size and morphology of gold nanoparticles in a wet-chemical process.

Polyhedral gold nanoparticles below 100 nm in size were fabricated by continuously delivered HAuCl(4) and PVP starting solutions into l-ascorbic acid aqueous solution in the presence of gold seeds, and under addition of sodium hydroxide (NaOH). By continuously delivered PVP and HAuCl(4) starting solutions in the presence of gold seed, the size and shape of polyhedral gold were achieved in relatively good uniformity (particle size distribution=65-95 nm). Morphological evolution was also attempted using different growth rates of crystal facets with increasing reaction temperature, and selective adsorption of PVP.