Diffusion Kinetics of Vitamin B12 from Alginate and Poly(vinyl acetate) Based Gel Scaffolds for Targeted Drug Delivery

Abstract

The research described here probed the thermodynamics and kinetics of Vitamin B₁₂ release from two types of polymeric gel scaffolds for targeted drug delivery applications. The polymeric gel scaffolds were successfully prepared from sodium alginate and polyvinyl acetate (PVA) using crosslinking and casting mechanisms, respectively. Vitamin B₁₂ was effectively blended into the polymeric gel scaffolds during their synthesis processes. The release of Vitamin B₁₂ from the polymeric gel scaffolds was characterized by immersing the scaffolds in a brine solution at various temperatures (25?°C, 32?°C and 37?°C) and, simultaneously, the transient concentrations were measured using a UV visible spectrophotometer. The sodium alginate gel scaffolds exhibited a more rapid release of Vitamin B₁₂ as compared to the PVA gel scaffolds. The Vitamin B₁₂ release kinetics from the alginate and PVA scaffolds were characterized by fitting the experimental data with various diffusion kinetic models. The Vitamin B₁₂ release from the alginate gel scaffolds followed the Peppas-Sahlin model, whereas releases from the PVA gel scaffolds were fitted to the Hopfenberg model. The diffusion coefficients for the alginate scaffolds with respect to the three temperatures were found to be 15.72?m²/s, 17.17?m²/s and 18.58?m²/s respectively whereas the diffusion coefficients for the PVA scaffolds with respect to the three temperatures were found to be 0.23?m²/s, 0.29?m²/s and 0.32?m²/s respectively. The activation energies (E_a) for the two types of polymeric scaffolds were calculated using the Stannett equation and found to be 10.38?kJ.mol^?1 and 20.47?kJ.mol^?1 for the alginate and PVA scaffolds, respectively, for all three temperatures.     

The formation and stability of quasicrystal in Al80Mn14Si6 under high static pressure

Abstract

The method of quenching in fusing state under high static pressure (MQFSHP) was applied for the first time to prepare the quasicrystal icosahedral phase of Al₈₀Mn₁₄Si₆ alloy. The pressure was from 2.8GPa to 3.1GPa and the cooling rate during quenching was of about 100°C/s. Some sharp electron diffraction spots showing an arrangement with a five-fold symmetry axis and noncrystalline ring have been observed in electron diffraction experiment.

The crystallization temperature of I phase obtained from high pressure(HP) is close to that of rapid cooling ribbon, but the cooling rate of the sample obtained is lower than that of rapid cooling ribbon.     

Cu1.5PMo12O40 as an efficient, mild and heterogeneous catalyst for the condensation of indole with carbonyl compounds

Bis(indoyl)methanes have been synthesized in excellent yields in the presence of catalytic amount of Cu_1.5PMo₁₂O₄₀ in molten tetraethylammonium chloride as an ionic liquid. The catalyst is recovered and recycled.     

Vortex phase diagram studies in the weakly pinned single crystals of YNi2B2C and LuNi2B2C

We present a study of magnetization measurements performed on the single crystals of YNi₂B₂C and LuNi₂B₂C. For both the compounds, we find flux jumps in magnetisation values in the respective field regions, where the structural transitions in the flux line lattice symmetry have been reported in these systems via the small angle neutron scattering experiments. The magnetisation hysteresis loops and the AC susceptibility measurements show pronounced peak effect as well as second magnetisation peak anomaly for both YNi₂B₂C and LuNi₂B₂C. Based on these results, a vortex phase diagram has been constructed for YNi₂B₂C forH∥c depicting different glassy phases of the vortex matter.     

Optically-Pumped Far-Infrared Laser Lines of Methanol Isotopomers: 12CH3OH, 12CH3OD, and 12CH2DOH

Twenty-seven new far-infrared laser lines from the isotopomers of methanol: ¹²CD₃OH, ¹²CH₃OD, and ¹²CH₂DOH, were obtained by optically-pumping the molecules with an efficient cw CO₂ laser. The CO₂ laser provided pumping from regular, sequence, and hot-band CO₂ laser transitions. The 2-m long far-infrared cavity was a metal-dielectric waveguide closed by two, flat end mirrors. Several short-wavelength (below 100 m) lines were observed. The frequencies of 28 laser lines observed in this cavity (including new lines and already known lines) were measured with a fractional uncertainty limited by the fractional resetability of the far-infrared laser cavity, of 2 parts in 10⁷.     

Optically Pumped Far-Infrared Laser Lines of Methanol Isotopomers: 12CD3OH, 12CH3OD, and 12CH2DOH

Twenty-seven new FIR, far-infrared, laser lines from the isotopomers of methanol: ¹²CD₃OH, ¹²CH₃OD, and ¹²CH₂DOH, were obtained by optically pumping the molecules with an efficient cw CO₂ laser. The CO₂ laser provided pumping from regular, sequence, and hot-band CO₂ laser transitions. The 2 m long far-infrared cavity was a metal-dielectric waveguide closed by two, flat end mirrors. Several short-wavelength (below 100 m) lines were observed. The frequencies of 28 laser lines observed in this cavity (including new lines and already known lines) were measured with a fractional uncertainty limited by the fractional resetability of the far-infrared laser cavity, of 2 parts in 10⁷.     

Possible coexistence of superconductivity and magnetic order in NdPt2B2C

Coexistence of superconductivity and magnetic order has been one of the exciting aspects of the quaternary borocarbide superconductors, So far, RNi₂B₂C (R=Tm, Er, Ho and Dy) are the only known magnetic superconductors in this family. Here, we present our resistivity, magnetization and heat capacity studies on NdPt₂B₂C (nominal composition, NdPt_1.5Au_0.6B₂C and NdPt_2.1B_2.4C_1.2). We find superconductivity in both samples with T _c,onset ∼ 3 K. Bulk magnetic order is found to occur below 1.7 K. We suggest that NdPt₂B₂C is a possible magnetic superconductor.     

Crystallization of amorphous FeNiZrB and FeNiCoZrB alloys

Solid xenon layers are proposed as an alternative to graphite catchers for collecting samples at on-line separators. The formation of solid xenon layers is described. Sample atoms of bismuth have been held for up to a day in such layers before being released as cold free atoms for laser spectroscopy measurement. An application to studying daughter nuclei produced by α-decay is considered. It involves a two-stage process where daughter recoils are first accumulated in the xenon layer and subsequently released into flowing helium for laser-ionization and counting.     

Effects of gamma radiation on the microstructure,luminescence and medical properties for nano-Mn3B7O13Cl

ABSTRACT

A nano-Mn₃B₇O₁₃Cl crystal was synthesized by a sol–gel method, and the structure, morphology and size were characterized by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy. Effects of gamma radiation on the microstructure, luminescence properties, and medical performance for Mn₃B₇O₁₃Cl have been discussed. The results show that Mn₃B₇O₁₃Cl nanocrystals are uniform, and the average crystal size is about 50?nm. Under the 202?Gy measurement of gamma-ray irradiation, there are a large number of crystal defects in a chambersite crystal, and the defect is given priority with point defects and dislocations especially in gamma-ray irradiation with high energy. The luminescence intensity of natural chambersite in red light wavelengths increased obviously, and the luminescence intensity increased by 3.5 times. Nano-Mn₃B₇O₁₃Cl exhibited the most significant antitumor activity and antiseptic effects. The best inhibition concentration of natural chambersite to A549 is 100?µg/ml, and its inhibition rate reaches 80%. Addition of natural chambersite in the solution significantly lowers the concentrations of Escherichia coli BL21, and the value is reduced by 97.6%. Therefore, chambersite has important application in the field of medical and shielding materials.     

Synthesis and Characterization of Monodispersed SiO2@Y3Al5O12:Er3+ Core-Shell Particles

Submicron core-shell structure particles SiO₂@Y₃Al₅O₁₂:Er³⁺, which silica spherical particles was coated with an yttrium aluminum garnet (Y₃Al₅O₁₂) layer doped with Er³⁺, were prepared by the modified Pechini-Type sol-gel method for the first time. The structure and morphology of samples were detected by the X-ray powder diffraction (XRD) measurement, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), respectively. The results indicate that well-crystallized garnet nanocrystallines were formed on the surface of the silica particles. The luminescent spectra in near infrared and visible region of the core-shell structured SiO₂@Y₃Al₅O₁₂:Er³⁺ powders were also investigated and compared with those of the pure Y₃Al₅O₁₂:Er³⁺ and the Er³⁺ doped silicate glass. The results show that mono-dispersed SiO₂@Y₃Al₅O₁₂:Er³⁺ core-shell spherical particles with the near infrared, red and green luminescent emissions under the excitation of 980 nm laser diode have been successfully synthesized.     

A Sensitive Isotope Selective Nondispersive Infrared Spectrometer for 13CO2 and 12CO2 Concentration Measurements in Breath Samples

We present a nondispersive infrared spectrometer (NDIRS) for the measurement of the ¹³CO₂/¹²CO₂-ratio in breath samples. A commercial NDIR spectrometer for CO₂ concentration measurements in industrial process control was modified using two separate optical channels for the ¹³CO₂ and ¹²CO₂ detection. Cross interference due to overlapping absorption lines of both isotopic gases was successfully eliminated. The sensitivity of this device is ± 0.4‰ of the ¹³CO₂/¹²CO₂-ratio in a range of 2.5 to 5% of total CO₂. This is sufficient for biomedical applications. Our spectrometer is small in size, cheap and simple to operate and thus a true alternative to isotope ratio mass spectrometers (IRMS). Several biomedical applications with breath samples were demonstrated and were compared in very good agreement with IRMS.     

Calculations of the optical and EPR spectral data for Cr3+ ion in Y3Ga5O12 crystal from the complete diagonalisation method

The complete diagonalisation (of energy matrix) method is applied in this paper to calculate together the optical and electron paramagnetic resonance (EPR) spectral data for Cr³⁺ ion at the trigonal Ga³⁺ site of Y₃Ga₅O₁₂ crystal. The method is founded on the two-spin-orbit-parameter model where in addition to the contributions from the spin-orbit parameter of central dⁿ ion (i.e., one-spin-orbit-parameter model) in the traditional crystal field theory, those from the spin-orbit parameter of ligand ion via covalence effect is also considered. The calculated results propose that by using only four adjustable parameters, the 12 observed spectral data (nine optical band positions and three EPR parameters g_//, g_⊥ and D) in Y₃Ga₅O₁₂: Cr³⁺ are reasonably explained. The impurity-induced local lattice distortion of Cr³⁺ in Y₃Ga₅O₁₂ crystal is also estimated through the calculations. The results are discussed.     

Synthesis and characterization of monodisperse spherical core-shell structured SiO2@Y3Al5O12:Ce3+/Tb3+ phosphors for field emission displays

Nanocrystalline Y₃Al₅O₁₂: Ce³⁺/Tb³⁺ (average crystalline size 30 nm) phosphor layers were coated on non-aggregated, monodisperse and spherical SiO₂ particles by the sol-gel method, resulting in the formation of core-shell structured SiO₂@Y₃Al₅O₁₂:Ce³⁺/Tb³⁺ particles. X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, photoluminescence, cathodoluminescence spectra, as well as lifetimes were utilized to characterize the core-shell structured SiO₂@Y₃Al₅O₁₂:Ce³⁺/Tb³⁺ phosphor particles. The obtained core-shell structured phosphors consist of well-dispersed submicron spherical particles with a narrow size distribution. The thickness of the Y₃Al₅O₁₂:Ce³⁺/Tb³⁺ shells on the SiO₂ cores (average size about 500 nm, crystalline size about 30 nm) could be easily tailored by varying the number of deposition cycles (100 nm for four deposition cycles). Under the excitation of ultraviolet and low-voltage electron beams (1–3 kV), the core-shell SiO₂@Y₃Al₅O₁₂:Ce³⁺/Tb³⁺ particles show strong yellow-green and green emission corresponding to the 5d–4f emission of Ce³⁺ and ⁵D₄–⁷F _J (J = 6, 5, 4, 3) emission of Tb³⁺, respectively. These phosphors may have potential application in field emission displays.     

On the electronic contribution to the elastic constants in strained quantum wire superlattices of non-parabolic semiconductors with graded structures: Theory and suggestion for experimental determination

Summary  We study the electronic contribution to the second- and third-order elastic constants in strained quantum wire superlattices of non-parabolic semiconductors with graded structures and compare the same with the constituent materials, by formulating the appropriate dispersion laws. It is found, taking InSb/GaSb quantum wire superlattice as an example, that the said contributions increase with decreasing thickness and with increasing electron concentration in oscillatory manners together with the fact that the influence of the finite interface width enhances their numerical values. An experimental method is suggested for determining the electronic contribution to the elastic constants in materials having arbitrary dispersion laws. In addition, the well-known results for constituent semiconductors in the absence of stress have also been obtained as special cases of our generalized formulations.     

Hyperfine interactions of iron in ternary alloys with B82 type structures

The recoilless absorption spectra of iron in the ternary alloys CoFeGe, CoFeSb and FeMnGe, which possess B8₂ type structure, reveal the existence of different ordering temperatures of moments at 2(a) and 2(d) sites. Using the Einstein model to describe the second order Doppler shift, it has been found thatΘ _E appropriate to the thermal motions of iron atoms at 2(a) and 2(d) sites in CoFeGe are different, which is also suggested by the temperature dependences of the relative areas of the corresponding component spectra. In CoFeSb, on the other hand, relative areas of the component spectra are independent of temperature, and give the relative distribution of iron at the inequivalent sites. A large difference in the isomer shifts of 2(a) and 2(d) site spectra indicates a larger number of d-electrons in the atomi configuration for 2(a) atoms. The isomer shift change is negative for 2(a) site nuclei and positive for 2(d) site nuclei with increase in temperature. The magnetic fields at 2(d) site nuclei in CoFeGe and CoFeSb alloys indicate that the moments of the parent atoms are not much different from the value in iron metal.     

Ultrasound-assisted dispersion of SrFe<Subscript>12</Subscript>O<Subscript>19</Subscript> nanoparticles in organic solvents and the use of the dispersion as magnetic cosmetics

A new method of dispersing the aggregated strontium hexaferrite (SrFe₁₂O₁₉) magnetic nanoparticles in organic solvents such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol (PG), and glycerol, by an ultrasonic bath is reported herein. The particles size of SrFe₁₂O₁₉ after treatment with the PGMEA is in the range 70–100 nm. The structure of dispersed SrFe₁₂O₁₉ was characterized using transmission electron microscopy (TEM), high resolution scanning electron microscopy (HR SEM) and thermo gravimetric analysis (TGA). This dispersed material was used for the preparation of a topical magnetic cosmetic product as follows: The dispersion of SrFe₁₂O₁₉ in PG was mixed with “Dermud-Ahava Body Cream”, an ‘oil in water’ emulsion of a Dead Sea mineral cosmetic, “AHAVA”, and the magnetic properties of the created composite were determined. The ferrimagnetic behavior of the composite has been demonstrated as being very similar to the behavior of strontium hexaferrite itself.     

Unified calculations of the optical and electron paramagnetic resonance spectral data for Ce ion in Y3Ga5O12 crystal

Seven crystal field energy levels (obtained from the optical spectra) and three g factors g_x, g_y and g_z (obtained from electron paramagnetic resonance (EPR) spectra) for Ce³⁺ ion in Y₃Ga₅O₁₂ crystal are calculated together by diagonalizing a complete energy matrix. The Hamiltonian of this energy matrix includes all the interactions for 4f¹ ion Ce³⁺ in rhombic crystal field and under an external magnetic field, and so the optical and EPR data can be studied in a unified way. The calculated crystal field energy levels are in better agreement with the experimental values than the calculated values in the previous paper, and the g factors (which have not been calculated previously) are explained reasonably. The results are discussed.     

Structural and electronic properties of neutral clusters Ga12X (X=C, Si, Ge, Sn, and Pb) and their anions from first principles

The structural and electronic properties of neutral and negatively charged Ga₁₂X (X=C, Si, Ge, Sn, and Pb) clusters are calculated by the first-principles method. The results show that the most stable symmetry depends on the doped atom rather than the geometry structure. However, the geometry symmetry plays an important role in calculating the energy gap. In addition, in the anionic clusters, the added electron would reduce the energy gap by about 0.4 eV. As for the density of states (DOS), clusters with the same symmetry show a similar trend of DOS. The major impact on DOS by adding an electron is the occurrence of relative energy shift.     

Development of a “Built-in” Scanning Near Field Microscope Head for an Atomic Force Microscope System and Stress Mapping of an Al2O3/ZrO2 Eutectic Composite

We constructed a scanning near-field optical microscope (SNOM) on a commercially available atomic force microscopy (AFM) apparatus (SPM-9500J2; Shimadzu Corp.) to measure the stress distribution in ceramic composite materials. Features of our SNOM system are: (1) a compact SNOM head substituted for the original AFM head; (2) a wide scanning range (125 × 125 μm²) inherited from the original scanner; (3) use of conventional shear-force regulation; (4) an optical system for the illumination-collection (I-C) mode; (5) excitation by a 488 nm line of an Ar-ion laser, and (6) light detection by photon counting or a polychromator equipped with an electronically cooled charge coupled device (CCD). This SNOM system was used to measure the surface structure and stress distribution of an Al₂O₃/ZrO₂ eutectic composite. We simultaneously measured topographic images and fluorescence spectra of an Al₂O₃/ZrO₂ eutectic composite. We estimated its peak intensity, peak position, and peak width from the fluorescence spectrum during scanning, which respectively correspond to the abundance of Al₂O₃, stress in the grain, and the anisotropy of that stress. Mapping images showed that the stress and its anisotropy were weaker in the center of the Al₂O₃ grain than its boundary between Al₂O₃ and ZrO₂. That observation suggests that Al₂O₃ underwent intense anisotropic stress induced by volume expansion in the phase transition of ZrO₂ from the cubic phase to the monoclinic phase during preparation.     

Backbone-only restraints for fast determination of the protein fold: the role of paramagnetism-based restraints. Cytochrome b562 as an example

CH(alpha) residual dipolar couplings (Deltardc's) were measured for the oxidized cytochrome b562 from Escherichia coli as a result of its partial self-orientation in high magnetic fields due to the anisotropy of the overall magnetic susceptibility tensor. Both the low spin iron (III) heme and the four-helix bundle fold contribute to the magnetic anisotropy tensor. CH(alpha) Deltardc's, which span a larger range than the analogous NH values (already available in the literature) sample large space variations at variance with NH Deltardc's, which are largely isooriented within alpha helices. The whole structure is now significantly refined with the chemical shift index and CH(alpha) Deltardc's. The latter are particularly useful also in defining the molecular magnetic anisotropy parameters. It is shown here that the backbone folding can be conveniently and accurately determined using backbone restraints only, which include NOEs, hydrogen bonds, residual dipolar couplings, pseudocontact shifts, and chemical shift index. All these restraints are easily and quickly determined from the backbone assignment. The calculated backbone structure is comparable to that obtained by using also side chain restraint. Furthermore, the structure obtained with backbone only restraints is, in its whole, very similar to that obtained with the complete set of restraints. The paramagnetism based restraints are shown to be absolutely relevant, especially for Deltardc's.