Influence Of Polyvinylpyrrolidone Research Articles

Effects of PVP on structure of TiO 2 prepared by the sol-gel process

The synthesis of nanocrystalline TiO 2 powders obtained from the hydrolysis of Ti(OBu n ) 4 in the presence of polyvinylpyrrolidone (PVP) was investigated. Porous titania with a Brunauer–Emmett–Teller surface area up to 65 m 2 g −1 and distribution of pores in the range of mesopores were obtained after heat treatment at 500 °C devoted to the removal of PVP from TiO 2/PVP composites. The influence of PVP on the phase transformation of TiO 2 from anatase to rutile was investigated by using X-ray diffraction and Raman spectra. It was found that PVP could noticeably enhance the transformation by reducing the onset transformation temperature. The obtained powders were also characterized by differential scanning calorimeter, transmission electron microscopy and high-resolution electron microscopy.

Characterization of protein-loaded poly(?-caprolactone microparticles based on a factorial design

This study was designed to systematically investigate the characteristics of bovine serum albumin (BSA) loaded poly(epsilon-caprolactine) (PCL) microparticles based on a 2(4) factorial experiment. The influences of polyvinyl pyrrolidone (PVP) concentration, BSA/PCL ratio, w/o/o/o ratio, and PEG/PCL ratio on the surface morphology, particle size, as well as the yield of microparticles, encapsulation efficiency of BSA, and in vitro release properties were evaluated. The microparticles were prepared by the w/o/o/o solvent evaporation method. The structure of BSA retained its integrity using this technique. The mean particle sizes of BSA-loded microparticles were in the range of 20-50 microm, and a highly porous morphology existed in these microparticles, irrespective of the formulations. The production yields of microparticles were in the range of 52.1-89.0%, and the encapsulation efficiencies were in the range of 13.8-68.3%. The burst release of BSA was in the range of 6.9-69.0%. The volume ration of the multi-phases significantly affected the encapsulation efficiency of BSA in PCL microparticles, and the initial amount of BSA encapsulated by PCL in terms of BSA/PCL ratio significantly affected the amount of BSA released at the end of 14 days (p < 0.05).

THE EFFECT OF REDUCTION OF EXUDED PHENOLIC SUBSTANCES LEVEL ON ROOTING OF OAK MICROCUTTINGS

In this study we have followed the influence of polyvinylpyrrolidone (PVP) on the development of root system of oak microcuttings (Quercus robur L.), changes in the contents of phenolic substances in roots, and in the culture media. The microcuttings from explants cultured in vitro for 2 years have been used for rooting. Originally, the explants were taken from 150 years old oak tree. For the induction of rooting on agar medium with high concentration of 1-α- naphthaleneacetic acid (NAA, 14.0 mg l -1 ) has been used. After 1 week of etiolation, the microcuttings were displaced in light and transferred to agar media without NAA and with or without I % PVP. On the medium enriched with PVP 86.6 % of microcuttings rooted after 6 weeks. No substantial differences in average rooting of control microcuttings, cultured without PVP, were found (81.5 %). The enhancement of the lenght of adventitious roots after 6 and 10 weeks of cultivation was observed in microcuttings cultured with PVP. Addition of PVP decreased the endogenous contents of phenolic substances in the roots (by about 20 %) as well as in the culture media after 10 weeks of cultivation.

The Influence of Polyvinylpyrrolidone on Freezing of Bovine IVF Blastocysts Following Biopsy

A study was conducted to develop a better freezing protocol for in vitro developed biopsied bovine blastocysts. Biopsied blastocysts were exposed to 1.8 M ethylene glycol (EG) + 0.05 M trehalose (T) and different concentration (5, 10, and 20%) of polyvinylpyrrolidone (PVP). Exposure to the solutions alone did not affect their in vitro development (Experiment 1). Experiments 2, 3, and 4 tested the viability of biopsied blastocysts cryopreserved in 1.8 M EG + different concentrations of T (0, 0.05, 0.1, and 0.3 M), 1.8 M EG + different concentrations of PVP (0, 5, 10, and 20%), and 1.8 M EG + 0.05 M T + different concentrations of PVP (0, 5, 10, and 20%), respectively. The proportion of biopsied blastocysts that reexpanded following cryopreservation in 1.8 M EG + 0.05 M T (38.5%) and 1.8 M EG + 0.1 M T (36.1%) was significantly (P < 0.05) higher than the proportion that reexpanded in 1.8 M EG + 0.3 M T (13.9%) (Experiment 2). The viability and the percentage of embryos that developed to >250 μm in diameter in the 5, 10, and 20% PVP groups (77.8 and 50.0%, 78.1 and 43.8%, 76.9 and 65.4%, respectively) were significantly higher than those that developed cryopreserved without PVP (55.1 and 20.7%) (Experiment 3). Optimum development of in vitro culture of frozen-thawed biopsied blastocysts was obtained using 1.8 M EG + 0.05 M T and 20% PVP. Analysis of blastocysts >250/μm in diameter showed that the number of ICM cells of biopsied blastocysts cryopreserved in 1.8 M EG + 0.05 M T with or without PVP was not different from the number of unfrozen biopsied blastocysts. These results indicate that PVP has some beneficial effect on freezing of biopsied bovine blastocysts.

On the Influence of Polyvinylpyrrolidone (PVP) during the Synthesis of Ultrafine Emulsions

The influence of PVP as well as the influence of the excess of silver ions, and the quantity of silver iodide in the crystal phase, on the physical ripening of Lipmann’s emulsions are investigated. It is established that PYP favours the formation of ultrafine emulsions. Its inhibitory influence on physical ripening makes it possible to regulate and equalize the activity of the gelatins, used in the synthesis of Lipmann’s emulsions.Emulsions with a resolving power of 3200 1/mm satisfactory sensitivity and edge sharpness are synthesized.

A Kinetic Study of the Polymerization of Acrylic Acid in the Presence of Polyvinylpyrrolidone

Abstract The polymerization of acrylic acid (AA) in a dilute aqueous solution in the presence of polyvinylpyrrolidone (PVP) has been studied kinetically, with the extent of polymerization followed by a bromometric titration method. The rate of the polymerization changed characteristically with the amount of PVP in the solution and went through a maximum at a certain initial mole ratio of PVP and AA, [PVP]0/[AA]0, under a constant [AA]0 value. The mole ratio which gave the maximum rate was almost proportional to the reciprocal of [AA]0. In the course of the polymerization, a polymer complex consisting of PVP and polymerized AA was precipitated. Its composition, (PAA)c/(PVP)c, has been found to be different as the polymerization conditions are varied. Hardly no comparable data between the bromometric method and a turbidimetric method used to measure the rate were obtained. The influence of PVP on the polymerization was assumed to be caused by the local concentration of AA in the vicinity of PVP. A mechanism based on the effect of the local concentration, the “polymer atmosphere binding mechanism,” has been found to explain the experimental results well.

Polymerization in an interacting polymer system

The influence of polyvinyl pyrrolidone (PVP) on the polymerization of acrylic acid in dilute aqueous solution has been studied. The fact that the system becomes heterogeneous has been used to provide a turbidimetric method for following the polymerization. The rate of polymerization has been found to depend on the concentration of PVP, reaching a maximum at close to equimolar concentrations, based on monomer units. The kinetics of the system have been studied and have been found to exhibit characteristics of both heterogeneous polymerizations, and what might be expected of a “replica polymerization”. The complex formed as a result of the polymerization has been examined by intrinsic viscosity and electrophoresis studies, and has been found to consist apparently of PVP, polyacrylic acid (PAA) and a graft copolymer of these polymers.