Design and evaluation of mucoadhesive microspheres of repaglinide for oral controlled release

Gastro retentive dosage forms have potential for use as controlled-release drug delivery systems. Multiple unit systems avoid the “all-or-none gastric” emptying nature of single-unit systems. A controlled release system designed to increase its residence time in the stomach with contact with the mucosa was achieved through the preparation of mucoadhesive microspheres by the emulsion solvent evaporation technique consisting of (I) chitosan mucoadhesive (ii) repaglinide, an oral hypoglycemic agent; and (iii) Eudragit RS-100 as polymer. The microspheres were evaluated for surface morphology and particle shape by scanning electron microscope. The microspheres were also evaluated for their microencapsulation efficiency, in vitro wash-off mucoadhesion test, in vitro drug release and in vivo study. The microspheres were found to be spherical and free flowing. The microencapsulation efficiency was in the range of 61.44±1.16 to 79.90±1.17and microspheres exhibited good mucoadhesive property in the in vitro wash off test. The drug-polymer concentration of dispersed phase influences the particle size and drug release properties. All the formulations were followed by Matrix-Peppas model. The drug release was also found to be slow and extended for 24 h. In vivo testing of the mucoadhesive microspheres in diabetic albino rats demonstrated significant antidiabetic effect of repaglinide. The hypoglycemic effect obtained by mucoadhesive microspheres was for more than 16 whereas repaglinide produced an antidiabetic effect for only 10 h suggesting that mucoadhesive microspheres are a valuable system for the long term delivery of repaglinide.Keywords: Controlled Release, Repaglinide, Solvent Evaporation, Microspheres, Mucoadhesive

Non-destructive determination of ultra-thin GaN cap layer thickness in AlGaN/GaN HEMT structure by angle resolved x-ray photoelectron spectroscopy (ARXPS)

Angle resolved X-ray photoelectron spectroscopy (ARXPS) and secondary ion mass spectrometry (SIMS) investigations have been carried out to characterize the GaN cap layer in AlGaN/GaN HEMT structure. The paper discusses the qualitative (presence or absence of a cap layer) and quantitative (cap layer thickness) characterization of cap layer in HEMT structure non-destructively using ARXPS measurements in conjunction with the theoretical modeling. Further the relative sensitive factor (RSF=σGaσAl) for Ga to Al ratio was estimated to be 0.963 and was used in the quantification of GaN cap layer thickness. Our results show that Al/Ga intensity ratio varies with the emission angle in the presence of GaN cap layer and otherwise remains constant. Also, the modeling of this intensity ratio gives its thickness. The finding of ARXPS was also substantiated by SIMS depth profiling studies

Ion irradiation-induced, localized sp(2) to sp(3) hybridized carbon transformation in walls of multiwalled carbon nanotubes

In this report, ion irradiation-induced localized sp(2) to sp(3) hybridized carbon transformation in multiwalled carbon nanotubes (MWCNTs) was observed after irradiating MWCNTs with high-energy Au+8 ions (100 MeV). The used MWCNTs were grown using cobaltocene and benzene as catalyst and carbon source, respectively'by the thermal CVD technique and consist of both unfilled and Co-filled tubes. Prior to irradiation, the MWCNT sample was characterized using scanning electron microscope and micro-Raman and photoluminescence spectrometers. The effect of ion fluence on MWCNT walls and transformation of sp(2) to sp(3) sites was analyzed by Raman spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. We found that as the fluence increased, the localized transformation from sp(2) to sp(3) sites occurred in the walls of MWCNTs, which was evident by the emergence of peak at approximately 1543 cm(-1) associated with the G peak in tetrahedral amorphous carbon (ta-C) and the vanishing of 2D band (2700 cm(-1)). Furthermore, we observed broadening in D and G, with slight shift in their positions and consistent decrease in 2D band intensity, as fluence increased

As-pyrolyzed sugarcane bagasse possessing exotic field emission properties

The present study aims to demonstrate the application of sugarcane bagasse as an excellent field emitter. Field emission property of as-pyrolyzed sugarcane bagasse (p-SBg) before and after the plasma treatment has been investigated. It has been observed that electronic nature of p-SBg transformed from semiconducting to metallic after plasma treatment. Maximum current and turn-on field defined at 10 mu A/cm(2) was found to be 800 mu A/cm(2) and 2.2 V/mu m for as-pyrolyzed sugarcane bagasse (p-SBg) and 25 mu A/cm(2) and 8.4 V/mu m for H-2-plasma treated p-SBg. These values are found to be better than the reported values for graphene and activated carbon. In this report, pyrolysis of bagasse has been carried in a thermal chemical vapor deposition (Th-CVD) system in inert argon atmosphere. Scanning electron microscopy (SEM), X-ray Diffraction (XRD), High-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) have been used to study the structure of both pre and post plasma-treated p-SBg bagasse's sample. HRTEM study reveals that carbonaceous structures such as 3D-nanographene oxide (3D-NGO), graphite nanodots (GNDs), carbon nanotubes (CNTs), and carbon onions are present in both pre-treated and plasma-treated p-SBg. Hence, we envision that the performed study will be a forwarding step to facilitate the application of p-SBg in display devices

Fe3C-filled carbon nanotubes: permanent cylindrical nanomagnets possessing exotic magnetic properties

The present study aims to deduce the confinement effect on the magnetic properties of iron carbide (Fe3C) nanorods filled inside carbon nanotubes (CNTs), and to document any structural phase transitions that can be induced by compressive/tensile stress generated within the nanorod. Enhancement in the magnetic properties of the nanorods is attributed to tensile stress as well as to compression, present in the radial direction and along the nanotube axis, respectively. Finally, the growth of permanent cylindrical nanomagnets has been optimized by applying a field gradient. Besides presenting the growth model of in situ filling, we have also proposed the mechanism of magnetization of the nanotubes. Magnetization along the tube axis has been probed by confirming the pole formation. Fe3C has been selected because of its ease of formation, low TC and incompressibility

Facile Synthesis of Semiconducting Ultrathin Layer of Molybdenum Disulfide

In this paper, we have reported a simple and efficient method for the synthesis of uniform, highly conducting single or few layer molybdenum disulfide (MoS2) on large scale. Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM) have been used for the confirmation of mono or few layered nature of the as-synthesized MoS2 sheets. X-ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD) and Raman Spectroscopy have also been used to study the elemental, phase, and molecular composition of the sample. Optical properties of as-synthesized sample have been probed by measuring absorption and photoluminescence spectra which also compliment the formation of mono and few layers MoS2 Current-voltage (I-V) characteristics of as-synthesized sample in the pellet form reveal that MoS2 sheets have an ohmic character and found to be highly conducting. Besides characterizing the as-synthesized sample, we have also proposed the mechanism and factors which play a decisive role in formation of high quality MoS2 sheets

Observation of Skyrmions at Room Temperature in Co2FeAl Heusler Alloy Ultrathin Film Heterostructures

Magnetic skyrmions are topological spin-textures having immense potential for energy efficient spintronic devices. Here, we report the observation of stable skyrmions in unpatterned Ta/Co2FeAl(CFA)/MgO thin film heterostructures at room temperature in remnant state employing magnetic force microscopy. It is shown that these skyrmions consisting of ultrathin ferromagnetic CFA Heusler alloy result from strong interfacial Dzyaloshinskii-Moriya interaction (i-DMI) as evidenced by Brillouin light scattering measurements, in agreement with the results of micromagnetic simulations. We also emphasize on room temperature observation of multiple skyrmions which can be stabilized for suitable combinations of CFA layer thickness, perpendicular magnetic anisotropy, and i-DMI. These results provide a significant step towards designing of room temperature spintronic devices based on skyrmions in full Heusler alloy based thin films