Purpose: The objective of the present study was to prepare and evaluate microcapsules for the controlled release of lamivudine using various cellulose polymers Methods: The microcapsules were prepared by the solvent evaporation method. The prepared microcapsules were characterized for the percent drug content, entrapment efficiency, FTIR, DSC, scanning electron microscopy (SEM) and in vitro dissolution studies. Accelerated stability studies were also carried out. Results: The microcapsules were spherical and free flowing. The entrapment efficiency was 76-86%. The release of drug from the microcapsules extended up to 8 to 12 hours. FTIR and DSC thermograms showed the stable character of lamivudine in the microcapsules. SEM revealed that the microcapsules were porous in nature. The release kinetics study revealed that the prepared microcapsules were best fitted to the zero order for F-2, F-4 and F-5 formulations and Higuchi model, for F-1 and F-3 microcepsules Conclusion: The release kinetics data and characteristion studies indicate that drug release from microcapsules was diffusion-controlled and that the micrapsules were stable..

Nano-crystalline Cr x CoFe 2−x O 4 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) ferrites were synthesized by sol-gel method. The X-ray diffraction patterns of all the samples provide information about the existence of single phase spinel structure. The SEM and TEM micrographs show the uniform particle distribution and SAED pattern represents the polycrystalline nature of the resultant ferrite nano-particles. High purity of the sample is confirmed by energy dispersive X-ray analysis. The FTIR spectra show two strong absorption bands in the range of 600 -400 cm −1 , which confirm the presence of M-O stretching band in ferrites. The magnetic properties of the synthesized samples were investigated by using vibrating sample magnetometer at room temperature. According to VSM reports the main magnetic parameters like saturation magnetization (M s ), coercivity (H c ) were found to decrease with the substitution of Cr 3+ content. Possible mechanisms which are responsible for the results are scrutinized minutely in this paper.

Cr x Zn Fe 2-x O 4 (with x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) spinel ferrite nanoparticles have been synthesized via sol-gel method. The precursor compound was calcined at a temperature of 900°C for 3 h. The aim of this study was to investigate the effect of Cr 3? ion substitution on the structural and magnetic properties of Cr-Zn ferrite. The size, shape, and chemical state of the synthesized powders were structurally characterized by powder XRD, SEM, TEM, HRTEM, SAED, energy-dispersive X-ray analysis (EDAX), and Fourier transform infrared spectroscopy (FTIR) spectral techniques. The XRD pattern of Cr-Zn ferrite provides information about single-phase formation of spinel structure with cubic symmetry. Both crystallite size and lattice parameter decrease with increasing Cr content. Formation of spinel structure is affirmed by using FTIR and FTIR spectra which shows that the bands t1 and t2 are found to shift gradually toward the higher frequency side with substitution of Cr, which have been attributed to the decrease in the lattice constant. SEM and TEM micrographs demonstrated that nanoparticles with narrow size distribution were obtained. The average grain size was found to be in nanometer range and of the order of 43-63 nm obtained using TEM images. Compositional stoichiometry was confirmed by EDAX technique. The magnetic properties of synthesized chromium-substituted Zn ferrite nanoparticles were studied using vibrating sample magnetometer at room temperature under the applied magnetic field of 15 KG. The result indicated that the amount of Cr contents significantly influenced the crystal morphology and structural and magnetic properties of Cr-doped Zn ferrite nanoparticles.

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The series of Cr-Zn nano ferrites having the general composition Cr x ZnFe 2−x O 4 (0 ≤ x ≤ 0.5) have been synthesized successfully in the nanocrystalline form using the sol-gel method. The samples were sintered at 900˚C for 3 hours. The effect of chromium substitution on dielectric properties of Zn-ferrites is reported in this paper. The analysis of XRD patterns revealed the formation of single phase cubic spinel structure for all the Cr-Zn ferrite samples. The FTIR spectra show two strong absorption bands in the range of 400-600 cm −1 , which corroborate the spinel structure of the samples. The average grain size was found to be in the nanometer range and of the order of 43-63 nm obtained using TEM images. The lattice parameter and crystallite size decrease with increase in Cr concentration (x). The investigation on dielectric constant (ε'), dissipation factor (D) and ac conductivity (σ ac) was carried out at a fixed frequency 1 kHz and in the frequency range of 100 Hz to 1 MHz at room temperature using LCR meter. The plots of dielectric constant (ε') versus frequency show the normal dielectric behavior of spinel ferrites. The value of ac conductivity (σ ac) increases with increase in frequency for all the compositions. The appearance of the peak for each composition in the dissipation factor versus frequency curve suggests the presence of relaxing dipoles in the Cr-Zn nano ferrite samples. It is also found that the shifting of the relaxation peak towards lower frequency side with an increase in chromium content (x) is due to the strengthening of dipole-dipole interactions. The composition and frequency dependence of the dielectric constant, dielectric loss and ac-conductivity are explained based on the Koop's two-layer model, Maxwell-Wagner polarization process, and Debye relaxation theory.