Effect of crystalline phases of titania nanotube arrays on adipose derived stem cell adhesion and proliferation.

The aim of this work was to evaluate the cellular response to titanium nanotube arrays with variable crystalline structure. Cytotoxicity, viability and the ability of the titania nanotube arrays to stimulate adhesion and proliferation of adipose derived stem cells (ADSCs) was evaluated. Titania nanotube arrays were fabricated by electrochemical anodization of titanium in diethyleneglycol/hydrofluoric acid electrolyte at 60 V for 6 h, then annealed at 300, 530 and 630 °C for 5 h. The nanotube arrays were characterized using scanning electron microscopy (SEM), contact angle goniometry, x-ray diffraction (XRD) and protein adsorption. ADSCs were cultured on titania nanotube arrays at a density of 1 × 104 cells/ml. The cells were allowed to adhere and to proliferate for 1, 4 and 7 days. Cell viability was characterized by the CellTiter-Blue® Cell Viability Assay; and cell morphology was characterized by SEM. Cell adhesion, proliferation and morphology were characterized using fluorescence microscopy by staining the cells with DAPI and rhodamine/phalloidin. The results from this study showed that the annealing at 300 and 530 °C formed anatase phase, and annealing at 630 °C formed anatase/rutile phase. The results indicated that the modification of the crystalline structure (i.e. anatase/rutile phase) of titania nanotube arrays influenced the ADSC adhesion and proliferation. Future studies are now directed towards evaluating differentiation of this cellular model in osteoblasts.

Tube-Super Dielectric Materials: Electrostatic Capacitors with Energy Density Greater than 200 J·cm-3.

The construction and performance of a second generation of super dielectric material based electrostatic capacitors (EC), with energy density greater than 200 J·cm-³, which rival the best reported energy density of electric double layer capacitors (EDLC), also known as supercapacitors, are reported. The first generation super dielectric materials (SDM) are multi-material mixtures with dielectric constants greater than 1.0 × 105, composed of a porous, electrically insulating powder filled with a polarizable, ion-containing liquid. Second-generation SDMs (TSDM), introduced here, are anodic titania nanotube arrays filled with concentrated aqueous salt solutions. Capacitors using TiO2 based TSDM were found to have dielectric constants at ~0 Hz greater than 107 in all cases, a maximum operating voltage of greater than 2 volts and remarkable energy density that surpasses the highest previously reported for EC capacitors by approximately one order of magnitude. A simple model based on the classic ponderable media model was shown to be largely consistent with data from nine EC type capacitors employing TSDM.