ABSTRACT
Porous materials were produced based on high internal phase emulsions (HIPE) formulation stabilized by modified cellulose nanocrystals (CNCs). CNCs were first modified with bromoisobutyryl bromide and used as Pickering emulsion stabilizers to formulate highly concentrated inverse emulsions. Solid foams with an open porosity were successively produced by free radical polymerization of styrene/divinylbenzene continuous phase. The final materials were characterized regarding their cell size distribution, porosity and mechanical properties and then compared with well-known styrene/DVB polyHIPE stabilized either with usual surfactants or solid particles.
ABSTRACT
Dextran-coated silica beads are excellent supports for affinity chromatography of proteins. They can be easily grafted using conventional coupling methods with different active ligands, such as heparin. Fibroblast growth factors develop specific interactions with heparin through well-defined amino acids sequences. The heparin-dextran coated silica phases exhibit an affinity for these growth factors. Under our experimental conditions, the basic form can be absorbed on the solid support at a moderate salt concentration (0.5 M sodium chloride) and can be selectively desorbed by increasing the ionic strength of the eluent. The purification performances of such phases are compared to those obtained on the heparin grafted soft gels. Because of their mechanical properties, the dextran-coated silica supports were also used in high-performance affinity chromatography to purify fibroblast growth factors from a bovine brain crude extract.
Subject(s)
Chromatography, Affinity/methods , Fibroblast Growth Factors/analysis , Heparin , Silicon Dioxide , Animals , Brain Chemistry , Cattle , Fibroblast Growth Factors/metabolismABSTRACT
Basic fibroblast growth factor (bFGF) is a heparin-binding growth factor, so it was usually purified by affinity chromatography on a heparin-grafted support. It was previously observed that, among several modified polystyrene that exhibit anticoagulant heparin-like properties, insoluble polystyrenes modified by chlorosulphonation substituted with serine (PSSer) develop specific interactions with bFGF in solution. These PSSer resins were used as stationary phases in high-performance affinity chromatography in order to separate the radiolabelled growth factor from a bovine brain crude extract. The growth factor is strongly bound to the solid phase, as demonstrated by the adsorption isotherms. It can be adsorbed on the resin at low ionic strength and be desorbed by raising the salt concentration in the eluent. The effects of flow-rate, of the initial buffer and of the slope of the salt gradient on the adsorption and on the desorption of bFGF were investigated in order to study the thermodynamic and the kinetic parameters of the interactions and to define the optimum conditions for a fast and efficient separation of the growth factor.
Subject(s)
Chromatography, Affinity , Fibroblast Growth Factors/isolation & purification , Animals , Brain Chemistry , Cattle , Polystyrenes , Resins, Plant , Serine , Thermodynamics , Tissue Extracts/analysisABSTRACT
The heparin-binding growth factors aFGF and bFGF (acidic and basic fibroblast growth factor) from crude bovine brain extract were co-eluted with purified [125I]aFGF and/or [125I]bFGF as tracers from heparin-Sepharose and from several insoluble substituted polystyrenes used as stationary phases in low-pressure affinity chromatography. The ability of the resins to isolate FGFs was determined by measuring the eluted radioactivity. It was demonstrated that the various substituted polystyrene resins retain [125I]aFGF and [125I]bFGF with different specificities according to the chemical nature of the substituted groups bound to the polystyrene support. Bifunctional resins substituted with sulphonate and phenylalanine sulphamide groups adsorbed both [125I]aFGF and [125I]bFGF whereas bifunctional resins substituted with sulphonate and sulphamide serine adsorbed only [125I]bFGF. These stationary phases could be adapted to high-performance affinity chromatography and used to isolate growth factors of the FGF family.
