PH-sensitive chitosan films for baker's yeast immobilization

Dried baker's yeast cells were immobilized on a chitosan film, which is a natural polymer. Prepared chitosan films were treated with glutaraldehyde to facilitate the immobilization of the cells. The effects of the amount of glutaraldehyde, incubation time, pH, and temperature on immobilization were investigated. The amount of glutaraldehyde was chosen to be 0.01% (weight). The highest amount of yeast immobilization was obtained with 5 h incubation. It was determined that optimum temperature for immobilization is 25degreesC, and the optimum pH for immobilization is 6. Immobilized cells were allowed to stand for 3 d in distilled water and buffer solution (pH 6) to investigate the desorption, but no desorption was found. The maximum immobilization capacities were found to be 90 mug protein cm(-2) film in optimum conditions

Uranyl ion binding properties of poly(hydroxamic acid) hydrogels

Poly(hydroxamic acid) (PHA) hydrogels, obtained from the synthesis of crosslinked poly(acrylamide) (PAAm) gels have been prepared, and their uranyl ion binding properties from two different sources were investigated. Swelling and binding parameters of crosslinked PHA gels were determined from swelling and uranyl ion adsorption studies. The effect of uranyl ion concentration, pH, temperature and mass of adsorbent on the uranyl ion adsorption were examined. The binding process between PHA and uranyl ions complies with the S type adsorption according to Giles classification. Free energies of the adsorptions found as negative values indicating spontaneous adsorption process. The structure and hydrophilicity of the used crosslinkers, the ionogenity of PHA polymers and the source of uranyl ions found to be effective on the swelling and binding behaviors of PHA hydrogels

A comparison of adsorption isotherms of crosslinked poly(N-vinylpyrrolidone) basic brown 1 binding system

In this study, the binding of a basic dye such as basic brown 1 [BB 1] onto a crosslinked poly(N-vinylpyrrolidone) [CPVP] was investigated. Adsorption of the azo dye onto the CPVP was studied by the batch adsorption technique at 25 degrees C. In adsorption experiments a Langmuir type (L) adsorption was found with respect to the Giles classification system. Binding parameters such as initial binding constant (K-i), equilibrium constant (K), monolayer coverage (n), site-size (u), and maximum fractional occupancy (), and thermodynamic parameters such as heat of adsorption (Delta H), free energy of adsorption (Delta G) and entropy of adsorption (Delta S) for the CPVP/BB 1 system were calculated by using Klotz, Scatchard, and Langmuir linearization methods

Kinetic investigation of some steroids by thermogravimetry

The kinetic values of thermal degradation of some steroids were calculated by using TG and DTG curves and the Freeman-Carroll and the Jeres methods. The n and Ea values calculated by the Jeres method are more reasonable. The kinetic thermal stabilities of the simple functional groups of the steroids were compared by using the Ea values of Jeres, and the following sequences were found: 17?-OH>17-octy 1>17-Ac-CHO>17-keto; 3?-OH> 3-keto>3a-OH; and 5a-H>5?-H>?5(6)>?4. The k, Z, ?H*, ?S* and ?G* values were calculated at the maximum decomposition rate temperatures by using the Jeres values. The ?S* values are negative and suggest a high ordering of the transition state. The ?H* and ?G* values are positive, as expected. © 1990 Wiley Heyden Ltd, Chichester and Akadémiai Kiadó, Budapest

Synthesis, characterization and evaluation of IPN hydrogels for antibiotic release

We prepared new ternary interpenetrating polymeric networks (IPN) systems containing chitosan, poly(N-vinylpyrrolidone) and poly(acrylamide) polymers. IPNs were synthesized by radical polymerization of acrylamide monomers in presence of glutaraldehyde (G) and N,N'-methylenebisacrylamide as crosslinkers and the other polymers. These IPNs were named as C-P-A. Glutaraldehyde were used in different concentration to control the network porous of IPNs. Spectroscopic and thermal analyses of these cylindrical shaped IPNs were made with fourier transform infrared spectroscopy analysis, thermogravimetric analysis, and thermomechanical analysis. Swelling studies of IPNs were carried out at pH 1.1 and pH 7.4 at 37degreesC. The swelling and diffusion parameters of IPNs in these solutions were calculated. Amoxicillin as a bioactive species was entrapped to the IPNs during synthesis. In vitro release kinetics of IPNs were investigated. The experimental data of swelling and release studies suggest clearly that the swelling and release process obeys second-order kinetics. The release of the entrapped bioactive species from IPNs depends on the degree of crosslinking of the polymer and pH of the medium at body temperature. We observed that amoxicillin release at pH 1.1 was higher than at pH 7.4. As a result, IPNs-based chitosan with different cross-linker concentration could be promising candidates for formulation in oral gastrointestinal delivery systems

A comparison of adsorption isotherms of crosslinked poly(N-vinylpyrrolidone)/basic brown 1 binding system

In this study, the binding of a basic dye such as basic brown 1 [BB 1] onto a crosslinked poly(N-vinylpyrrolidone) [CPVP] was investigated. Adsorption of the azo dye onto the CPVP was studied by the batch adsorption technique at 25°C. In adsorption experiments a Langmuir type (L) adsorption was found with respect to the Giles classification system. Binding parameters such as initial binding constant (Ki), equilibrium constant (K), monolayer coverage (n), site-size (u), and maximum fractional occupancy (??), and thermodynamic parameters such as heat of adsorption (?H), free energy of adsorption (?G) and entropy of adsorption (?S) for the CPVP/BB 1 system were calculated by using Klotz, Scatchard, and Langmuir linearization methods

Removal of phenoxyacetic acid based herbicides by crosslinked poly(N-vinyl pyrrolidone)

In this study, binding of herbicides such as p-chlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid and the ammonium salt of 2,4-dichlorophenoxyacetic acid onto poly(N-vinyl pyrrolidone) and the adsorption of these herbicides to crosslinked poly(N-vinyl pyrrolidone) are investigated. It is shown that there are electrostatic interactions between anionic sites of the herbicides with cationic sites of poly(N-vinyl pyrrolidone). The adsorption of these herbicides to crosslinked poly(N-vinyl pyrrolidone) shows Type III adsorption isotherms. The values of percentage sorption of the low concentrations of herbicides are higher than those at the high concentrations of herbicides

In vitro dynamic swelling behaviors of polyhydroxamic acid hydrogels in the simulated physiological body fluids

Influence of some simulated physiological body fluids on the dynamic swelling behaviour of polyelectrolytic hydroxamic acid hydrogels (PHA) was investigated at 37 degreesC in vitro. The simulated physiological body fluids are distilled water, human sera, physiological saline (0.89% NaCl), isoosmotic phosphate buffer at pH 7.4, gastric fluid at pH 1.1, (gylicine-HCl buffer), urea (0.3 mol L-1), and the aquatic solutions of K2HPO4 and KNO3 (the sources of K+). The values of equilibrium swelling of PHA hydrogels varied in the range of 130-4625%, while the values of equilibrium fluid content of the hydrogels varied in the range of 57-97%. The initial rate of swelling, diffusional exponent, and, diffusion coefficient were calculated using swelling kinetics data. Diffusion of the fluids into the hydrogel was found to be non-Fickian character. The diffusion coefficients of the hydrogel varied between 0.6x10(-6) - 8.1x10(-6) cm(2) s(-1)

Adsorption of some anionic azo dyes onto crosslinked poly(N-vinylpyrrolidone) from aqueous solutions

In this study, bindings of anionic azo dyes containing sulphonyl group such as acid red 26, acid red 103, direct yellow 9, acid black 1 and acid orange 52 onto crosslinked poly(N-vinylpyrrolidone) (CPVP) have been investigated. Adsorption of anionic azo dyes onto CPVf were studied by batch adsorption technique. In the experiments of adsorption, L (Langmuir) type adsorption in the Giles classification system was found. Binding parameters such as initial binding constant (K(i)), equilibrium constant (K); monolayer coverage (n), site-size (u), maximum fractional occupancy (theta), and thermodynamic parameters such as heat of adsorption (Delta H), free energy of adsorption (Delta G) and entropy of adsorption (Delta S) for CPVP/anionic azo dye systems were calculated using Klotz method