Yan-Yan Song

Amphiphilic TiO2 nanotube arrays: an actively controllable drug delivery system.

Amphiphilic TiO(2) nanotube arrays are fabricated by a two-step anodization procedure combined with hydrophobic monolayer modification after the first step. These tubes can be used as biomolecular carriers, where the outer hydrophobic barrier provides an efficient cap against drug leaching to the environment. By utilizing the photocatalytic ability of TiO(2), a precisely controlled removal of the cap and a highly controlled release of the hydrophilic payload (drug) can be achieved.

Synthesis of Magnetically Separable Ag3PO4/TiO2/Fe3O4 Heterostructure with Enhanced Photocatalytic Performance under Visible Light for Photoinactivation of Bacteria

Silver orthophosphate (Ag3PO4) is a low-band-gap photocatalyst that has received considerable research interest in recent years. In this work, the magnetic Ag3PO4/TiO2/Fe3O4 heterostructured nanocomposite was synthesized. The nanocomposite was found to exhibit markedly enhanced photocatalytic activity, cycling stability, and long-term durability in the photodegradation of acid orange 7 (AO7) under visible light. Moreover, the antibacterial film prepared from Ag3PO4/TiO2/Fe3O4 nanocomposite presented excellent bactericidal activity and recyclability toward Escherichia coli (E. coli) cells under visible-light irradiation. In addition to the intrinsic cytotoxicity of silver ions, the elevated bactericidal efficiency of Ag3PO4/TiO2/Fe3O4 can be largely attributed to its highly enhanced photocatalytic activity. The photogenerated hydroxyl radicals and superoxide ions on the formed Ag/Ag3PO4/TiO2 interfaces cause considerable morphological changes in the microorganisms cells and lead to the death of the bacteria.

TiO2 nano test tubes as a self-cleaning platform for high-sensitivity immunoassays.

Since their discovery by Iijima in 1991, carbon nanotubes have attracted tremendous scientific and technological interest due to a combination of unique inherent properties and high expectations regarding their applications. Apart from carbon, over the past fewyears a number of ‘‘inorganic’’ nanotubular or nanoporous systems have also been reported that can be grown by a self-organizing electrochemical anodization process on various metallic or semiconductor substrates. A particular advantage is that distinct tubular features can be formed in regular arrays perpendicular to the substrate surface. This arrangement makes such structures ideal for use as nano test tubes for capturing, concentrating, releasing load, or probing formolecules, and such features have been reported for silica and alumina. Herein, we show how to use titania-nanotube (TiNT) arrays as a small-volume, high-sensitivity immunoassay detection system. Due to the unique photocatalytic properties of TiO2 these arrays have self-cleaning features, which makes themmost attractive for reusable devices. TiNTarrays canbe tuned in geometry (diameter, aspect ratio), ‘‘crystal’’ structure (amorphous, anatase, rutile), electronic and biomedical properties, and even freestanding membranes can be fabricated, and therefore a very versatile nanoscale architecture can be built. Up to now an unexploited path is the direct use of such nanotube arrays as reusable immunoassay platforms. In general, one of the key goals in immunoassay research is lowering the detection threshold, ultimately reaching singlecell and single-molecule diagnostics and reducing the probe volume to aminimum. In the present work, we use high-aspectratioTiNTs (whichprovidea longobservation length combined with a small volume) to enhance the detection level of fluorescence-labeled proteins in an immunoassay concept. Self-organized TiNT arrays were grown by anodization of Ti foils in ethylene glycol electrolytes containing NH4F, as described in the Experimental Section. The resulting TiNT layers are shown in the scanning electron microscopy (SEM)

Signal-amplified platform for electrochemical immunosensor based on TiO2 nanotube arrays using a HRP tagged antibody-Au nanoparticles as probe.

In this study, a novel signal-amplified electrochemical immunosensor was proposed by using TiO(2) nanotube (TiNT) arrays as the platform. Due to the distinct tubular features-large surface area, high pore volume and good electrochemical conductivity, the TiNT based electrodes exhibited excellent signal-amplified effects. gold nanoparticle (AuNP) was further utilized to bind horseradish peroxidase (HRP) tagged antibodies as recognition elements. Compared to the immunosensor based on either flat electrode, the immunosensors using TiNT layer as electrode showed higher amplified electrochemical signals from the catalytic reaction of HRP relative to hydrogen peroxide (H(2)O(2)). Under optimal conditions, the proposed immunosensor exhibited a good electrochemical behavior to antigen in a concentration range from 0.1 ng mL(-1) to 10(5) ng mL(-1) with a detection limit of 0.01 ng mL(-1). The results showed that the TiNT-based electrochemical immunosensing platform could provide a great potential in clinical application for detection of low-abundant proteins.

Development of Amperometric Glucose Biosensor Based on Prussian Blue Functionlized TiO2 Nanotube Arrays

Amperometric biosensors consisting of oxidase and peroxidase have attracted great attention because of their wide application. The current work demonstrates a novel approach to construct an enzymatic biosensor based on TiO2 nanotube arrays (TiNTs) as a supporting electrode on which Prussian Blue (PB)-an “artificial enzyme peroxidase” and enzyme glucose oxidase (GOx) have been immobilized. For this, PB nanocrystals are deposited onto the nanotube wall photocatalytically using the intrinsic photocatalytical property of TiO2, and the GOx/AuNPs nanobiocomposites are subsequently immobilized into the nanotubes via the electrodeposition of polymer. The resulting electrode exhibits a fast response, wide linear range, and good stability for glucose sensing. The sensitivity of the sensor is as high as 248 mA M−1 cm−2, and the detection limit is about 3.2 μM. These findings demonstrate a promising strategy to integrate enzymes and TiNTs, which could provide an analytical access to a large group of enzymes for bioelectrochemical applications including biosensors and biofuel cells.

Nickel Hydroxide Nanoparticle Activated Semi‐metallic TiO2 Nanotube Arrays for Non‐enzymatic Glucose Sensing

Semi-metallic TiO2 nanotube arrays (TiOx Cy NTs) have been decorated uniformly with Ni(OH)2 nanoparticles without the aid of a polymer binder. The resulting hybrid nanotube arrays exhibit excellent catalytic activity towards non-enzymatic glucose electro-oxidation. The anodic current density of the glucose oxidation is significantly improved compared with traditional TiO2 nanotubes decorated with Ni(OH)2 . Moreover, the Ni(OH)2 /TiOx Cy NT-based electrode shows a fast response, high sensitivity, wide linear range, good selectivity and stability towards glucose electro-oxidation, and thus provides a promising and cost-effective sensing platform for non-enzymatic glucose detection.

Galvanic deposition of nanostructured noble-metal films on silicon

Galvanic Deposition of Nanostructured Noble-Metal Films on Silicon Yan-Yan Song, Zhi-Da Gao, John J. Kelly,* and Xing-Hua Xia Key Laboratory of Analytical Chemistry for Life Science, Department of Chemistry, Nanjing University, Nanjing 210093, China Department of Physics, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China Debye Institute, Utrecht University, 3584 CC Utrecht, The Netherlands

Visible-Light-Triggered Drug Release from TiO2 Nanotube Arrays: A Controllable Antibacterial Platform

In this work, we use a double-layered stack of TiO2 nanotubes (TiNTs) to construct a visible-light-triggered drug delivery system. The key for visible light drug release is a hydrophobic cap on the nanotubes containing Au nanoparticles (AuNPs). The AuNPs allow for a photocatalytic scission of the hydrophobic chain under visible light. To demonstrate this principle, we loaded ampicillin (AMP) into the lower part of the TiO2 nanotube stack, triggered visible-light-induced release, and carried out antibacterial studies. The release from the platform becomes most controllable if the drug is silane-grafted in the hydrophilic bottom layer for drug storage. Thus, visible light photocatalysis can also determine the release kinetics of the active drug from the nanotube wall.

One-Step to Prepare Self-Organized Nanoporous NiO/TiO2 Layers and its Use in Non-Enzymatic Glucose Sensing

A highly ordered nanoporous NiTi oxide layers were fabricated on Ti alloys with high Ni contents (50.6 at.%) by a combination of self-organizing anodization at 0°C and subsequent selective etching in H2O2. The key for successful formation of such layers is to sufficiently suppress the dissolve of NiO by applying lower temperature during anodization. The resulting nanoporous structure is connected and well-adhered, which exhibits a much higher electrochemical cycling stability in 0.1 M NaOH. Without further surface modification or the use of polymer binders, the layers can be behave as a low-cost, stable and sensitive platform in non-enzymatic glucose sensing.

Covalent functionalization of TiO2 nanotube arrays with EGF and BMP-2 for modified behavior towards mesenchymal stem cells

In the present work we show the covalent immobilization of two bioactive molecules, epidermal growth factor (EGF) and bone morphogenetic protein-2 (BMP-2), on TiO(2) nanotube surfaces and the resulting influence on the behavior of mesenchymal stem cells. Covalent immobilization of these growth factors onto the oxide surfaces was achieved by N,N-carbonyldiimidazole (CDI) coupling via binding to amine groups of the proteins either directly or via a spacer, namely 11-hydroxy-undecylphosphonic acid (PhoA). The behavior of mesenchymal stem cells can be significantly altered by such an activation procedure. The effect is depending on the diameters of the nanotubes. Most importantly, on 100 nm diameter tubes the cell activity and cell number were drastically increased by grafting such nanotube surfaces with EGF. This demonstrates that the strong diameter dependence on cell activity in the range between 15 and 100 nm observed in prior work can be compensated by coating of the nanotube surfaces with EGF.