Stabilization of Rutile-related Thin Film on TiO\u3csub\u3e2\u3c/sub\u3e Substrates

Conducting metal oxide thin films are of broad interest because they have a wide variety of magnetic and electronic properties. Materials exist that range from superconducting to insulating, are ferromagnetic and are ferroelectric. These properties make thin conducting oxide films attractive for many industrial applications. A class of metal oxides exists that adapt the rutile crystal structure; the structure of the mineral rutile, TiO2. These metal oxides have the general formula MO2 where M is a metal cation of valence +4. Metal oxides crystallizing in the rutile structure also display a wide variety of physical properties. The objective of this research was to examine the ability of single crystal rutile (TiO2) substrates to stabilize various isostructural MO2 compounds prepared by chemical vapor deposition (CVD). This included metastable and unusual valence state metal oxide compounds. The materials examined in this thesis included CrO2 and RuO2. CrO2 is a ferromagnetic material of significant interest because it has been theoreticcally predicted to have complete spin-polarization of the conduction electrons. This exciting intrinsic property makes CrO2 a leading candidate for breakthrough devices in the field of magnetoelectronics. RuO2 is a highly conductive oxide with metallic properties. It has attracted significant interest in the development of ultralarge scale integrated circuits as a conducting layer combined with new classes of high dielectric oxide materials. In addition, RuO2 is an ideal non-magnetic metal layer (NM) for magnetoelectronic devices based upon CrO2. In order for advances in magnetoelectronics to occur using rutile-based materials, ultra thin multilayer structures must be fabricated with precise thickness and interfacial homogeneity control. A first step in realizing this goal is gaining a fundamental understanding of the thermodynamic processing space for stabilizing each compound. A second step is understanding factors which influence film roughness and physical properties. This thesis attempts to understand some of these major issues for ultimately fabricating novel magnetoelectronic devices based upon metal oxides that crystallize in the rutile structure. The characterization of the films included the crystalline structure by x-ray diffraction and surface morphology by atomic force microscopy

A Novel Multifunctional Nanowire Platform for Highly Efficient Isolation and Analysis of Circulating Tumor-Specific Markers

Circulating tumor-specific markers are crucial to understand the molecular and cellular processes underlying cancer, and to develop therapeutic strategies for the treatment of the disease in clinical applications. Many approaches to isolate and analyze these markers have been reported. Here, we propose a straightforward method for highly efficient capture and release of exosomes and circulating tumor cells (CTCs) in a single platform with well-ordered three-dimensional (3D) architecture that is constructed using a simple electrochemical method. Conductive polypyrrole nanowires (Ppy NWs) are conjugated with monoclonal antibodies that specifically recognize marker proteins on the surface of exosomes or CTCs. In response to electrical- or glutathione (GSH)-mediated stimulation, the captured exosomes or cells can be finely controlled for retrieval from the NW platform. A surface having nano-topographic structures allows the specific recognition and capture of small-sized exosome-like vesicles (30–100 nm) by promoting topographical interactions, while physically blocking larger vesicles (i.e., microvesicles, 100–1,000 nm). In addition, vertically aligned features greatly improve cell capture efficiency after modification with desired high-binding affinity biomolecules. Notably, exosomes and CTCs can be sequentially isolated from cancer patients' blood samples using a single NW platform via modulating electrochemical and chemical cues, which clearly exhibits great potential for the diagnosis of various cancer types and for downstream analysis due to its facile, effective, and low-cost performance

Chitosan nanoparticle-based neuronal membrane sealing and neuroprotection following acrolein-induced cell injury

<p>Abstract</p> <p>Background</p> <p>The highly reactive aldehyde acrolein is a very potent endogenous toxin with a long half-life. Acrolein is produced within cells after insult, and is a central player in slow and progressive "secondary injury" cascades. Indeed, acrolein-biomolecule complexes formed by cross-linking with proteins and DNA are associated with a number of pathologies, especially central nervous system (CNS) trauma and neurodegenerative diseases. Hydralazine is capable of inhibiting or reducing acrolein-induced damage. However, since hydralazine's principle activity is to reduce blood pressure as a common anti-hypertension drug, the possible problems encountered when applied to hypotensive trauma victims have led us to explore alternative approaches. This study aims to evaluate such an alternative - a chitosan nanoparticle-based therapeutic system.</p> <p>Results</p> <p>Hydralazine-loaded chitosan nanoparticles were prepared using different types of polyanions and characterized for particle size, morphology, zeta potential value, and the efficiency of hydralazine entrapment and release. Hydralazine-loaded chitosan nanoparticles ranged in size from 300 nm to 350 nm in diameter, and with a tunable, or adjustable, surface charge.</p> <p>Conclusions</p> <p>We evaluated the utility of chitosan nanoparticles with an in-vitro model of acrolein-mediated cell injury using PC -12 cells. The particles effectively, and statistically, reduced damage to membrane integrity, secondary oxidative stress, and lipid peroxidation. This study suggests that a chitosan nanoparticle-based therapy to interfere with "secondary" injury may be possible.</p

Inorganic surfaces modified by TAT peptides: Tuning lithographic strategies, surface science characterization, and biocompatibility assessment

The complexation of TAR RNA and the TAT protein is one of the most studied interactions. The basic question that researchers are trying to address is centered on the specificity and strength of binding of the arginine rich region of the TAT protein with the target RNA. The TAT peptide molecules were immobilized on surfaces using three different methodologies: adsorption from solution, microcontact printing, and scanning probe lithography. Features as small as 100 nm were generated by self-assembling approaches on three different inorganic surfaces: Au, Si/SiOx and GaAs. The nanoscopic features generated by scanning probe lithography were compared with monolayers created from adsorption from solution and microcontact printing to understand the structure of the TAT peptide monolayer generated by the different methods. The modified surfaces were characterized by Contact Angle Measurements, Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS), and Fourier Transform-Infrared Reflection Absorption Spectroscopy (FT-IRRAS). The thesis work also explored the use of chemical force microscopy in order to quantify the interaction between TAR RNA and Tat peptide lithographic features on GaAs. An AFM tip functionalized with TAR RNA was used in order to record adhesion maps. Specific vs. non-specific interactions were investigated under different pH conditions. The findings showed an increased interaction between TAR RNA and the peptide sequence that is rich in arginines. The final portion of this work focused on modifying GaAs in order to make it more biocompatible because the unprotected GaAs surface can release heavy metal compounds such as AsOx which are toxic to living cells. Experiments were performed to compare the cell spreading behavior on the GaAs substrates modified by different chemical approaches. The results suggest that when the toxicity of the GaAs surface is reduced or eliminated, the cells\u27 viability and spreading depend on the chemical and topographical nature of the surface

STABILIZATION OF RUTILE-RELATED THIN FILM ON TiOz SUBSTRATES BY

Conducting metal oxide thin films are of broad interest because they have a wide variety of magnetic and electronic properties. Materials exist that range from superconducting to insulating, are ferromagnetic and are ferroelectric. These properties make thin conducting oxide films attractive for many industrial applications. A class of metal oxides exists that adapt the rutile crystal structure; the structure of the mineral rutile, TiO2. These metal oxides have the general formula MO2 where M is a metal cation of valence +4. Metal oxides crystallizing in the rutile structure also display a wide variety of physical properties. The objective of this research was to examine the ability of single crystal rutile (TiO2) substrates to stabilize various isostructural M02 compounds prepared by chemical vapor deposition (CVD). This included metastable and unusual valence state metal oxide compounds. The materials examined in this thesis included CrO2 and RuO2. Cr02 is a ferromagnetic material of significant interest because it has been theoreticcally predicted to have complete spin-polarization of the conduction electrons. This exciting intrinsic property makes Cr02 a leading candidate for breakthrough devices in the field of magnetoelectronics