Composite chitosan and calcium sulfate scaffold for dual delivery of vancomycin and recombinant human bone morphogenetic protein-2

A biodegradable, composite bone graft, composed of chitosan microspheres embedded in calcium sulfate, was evaluated in vitro for point-of-care loading and delivery of antibiotics and growth factors to prevent infection and stimulate healing in large bone injuries. Microspheres were loaded with rhBMP-2 or vancomycin prior to mixing into calcium sulfate loaded with vancomycin. Composites were evaluated for set time, drug release kinetics, and bacteriostatic/bactericidal activity of released vancomycin, induction of ALP expression by released rhBMP-2, and interaction of drugs on cells. Results showed the composite set in under 36 min and released vancomycin levels that were bactericidal to S. aureus (>MIC 8–16 μg/mL) for 18 days. Composites exhibited a 1 day-delayed release, followed by a continuous release of rhBMP-2 over 6 weeks; ranging from 0.06 to 1.49 ng/mL, and showed a dose dependent release based on initial loading. Released rhBMP-2 levels were, however, too low to induce detectable levels of ALP in W20-17 cells, due to the affinity of rhBMP-2 for calcium-based materials. With stimulating amounts of rhBMP-2 (>50 ng/mL), the ALP response from W-20-17 cells was inhibited when exposed to high vancomycin levels (1,800–3,600 μg/mL). This dual-delivery system is an attractive alternative to single delivery or preloaded systems for bone regeneration since it can simultaneously fight infection and deliver a potent growth factor. Additionally, this composite can accommodate a wide range of therapeutics and thus be customizable for specific patient needs, however, the potential interactive effects of multiple agents must be investigated to ensure that functional activity is not altered.     

Thin-Film Encapsulated RF MEMS Switches

A wafer-level thin-film encapsulation process has been demonstrated to package radio-frequency (RF) microelectromechanical systems (MEMS) switches in this paper. Individual shunt capacitive switches were packaged in a ~1nL inorganic enclosure with process temperatures not exceeding 300 degC. A shell covering the switch consisted of 10 nm of sputtered alumina and 1.67 mum of sputtered silicon nitride dielectric film. The switch and dielectric shell were simultaneously wet-released through access channels in the shell. Following release, access channels were sealed with 10 nm of sputtered alumina and 2-4 mum of either plasma-enhanced chemical vapor deposited silicon dioxide or silicon nitride. Electromagnetic simulation and RF test results before and after sealing show minimal RF degradation of switch performance. Before sealing, the insertion loss and isolation at 10 GHz averaged 0.12 and 10.7 dB, respectively. After sealing, the same devices had an average insertion loss and isolation of 0.12 and 10.1 dB, respectively. Complete characterization of the package atmosphere was not completed due to challenges in assessing nanoliter-scale volumes     

Tuning the Phase and Microstructural Properties of TiO<Subscript>2</Subscript> Films Through Pulsed Laser Deposition and Exploring Their Role as Buffer Layers for Conductive Films

Titanium oxide (TiO₂) is a semiconducting oxide of increasing interest due to its chemical and thermal stability and broad applicability. In this study, thin films of TiO₂ were deposited by pulsed laser deposition on sapphire and silicon substrates under various growth conditions, and characterized by x-ray diffraction (XRD), atomic force microscopy (AFM), optical absorption spectroscopy and Hall-effect measurements. XRD patterns revealed that a sapphire substrate is more suitable for the formation of the rutile phase in TiO₂, while a silicon substrate yields a pure anatase phase, even at high-temperature growth. AFM images showed that the rutile TiO₂ films grown at 805°C on a sapphire substrate have a smoother surface than anatase films grown at 620°C. Optical absorption spectra confirmed the band gap energy of 3.08 eV for the rutile phase and 3.29 eV for the anatase phase. All the deposited films exhibited the usual high resistivity of TiO₂; however, when employed as a buffer layer, anatase TiO₂ deposited on sapphire significantly improves the conductivity of indium gallium zinc oxide thin films. The study illustrates how to control the formation of TiO₂ phases and reveals another interesting application for TiO₂ as a buffer layer for transparent conducting oxides.     

Large area Ba1 − xSrxTiO3 thin films for microwave applications deposited by pulsed laser ablation

Large area Ba_1 − xSr_xTiO₃ (BST) thin films with x = 0.4 or x = 0.5 were deposited on 75 mm diameter Si wafers in a pulsed laser deposition (PLD) chamber enabling full-wafer device fabrication using standard lithography. The deposition conditions were re-optimized for large PLD chambers to obtain uniform film thickness, grain size, crystal structure, orientation, and dielectric properties of BST films. X-ray diffraction and microstructural analyses on the BST films grown on Pt/Au/Ti electrodes deposited on SiO₂/Si wafers revealed films with (110) preferred orientation with a grain size < 100 nm. An area map of the thickness and crystal orientation of a BST film deposited on SiO₂/Si wafer also showed (110) preferred orientation with a film thickness variation < 6%. Large area BST films were found to have a high dielectric tunability of 76% at an electric field of 400 kV/cm and dielectric loss tangent below 0.03 at microwave frequencies up to 20 GHz and a commutation quality factor of ~ 4200.     

Female and male sexual responses in female cats with ventromedial hypothalamic lesions.

Following preoperative testing for receptivity, proceptivity, and male mating behavior, 27 female cats received either lesions in the anterior or posterior portion of the ventromedial hypothalamus (VMH) or sham lesions. Neither of the VMH lesion placements reduced proceptivity and receptivity scores. However, the female mating pattern was significantly altered in that although females in both lesion groups initially allowed a stud male to mount, they usually did not allow the male to intromit. As in rodents, the VMH in the cat appears to be an important neural area for the display of normal female sexual behavior. Low levels of male sexual behavior were seen in the 3 groups preoperatively, and no changes were observed in the levels of male behavior following lesion placement. Thus, because lesions that disrupted female behavior did not affect male sexual behavior, it appears that the neural areas controlling homotypical and heterotypical sexual behaviors are not necessarily neurally linked. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Growth of II-IV-V<Subscript>2</Subscript> chalcopyrite nitrides by molecular beam epitaxy

Synthesis of crystalline MgGeN₂ thin solid films is achieved using the technique of molecular beam epitaxy (MBE). The details of the epitaxial process are described. The microstructures of these films are investigated by both x-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). Comparison of the lattice structure with powder diffraction standards suggests the lattice structure may be orthorhombic with a high degree of texture. Morphology is evaluated by atomic force microscopy, and a periodic pattern of growth mounds is observed. A formalism for dynamical roughening is applied to quantify the mounded surface features. Mounds are found to have an average spacing of 235 nm, and the surface exhibits a saturation value of 22 nm for the root mean correlated height difference. Diffusion bias is discussed as a mechanism for the formation of surface mounds.     

Tungsten masking against boron implantation

Electron-beam evaporated and ion-beam sputtered films have been successfully used as masks against high-dosage boron implantation. Evaporated films were found to be somewhat more effective, probably because of their higher density. The predicted value for the required mask thickness was in satisfactory agreement with the experimentally determined value.