Improving the binding capacity of Ni2+ decorated porous magnetic silica spheres for histidine-rich protein separation.

Biomagnetic immobilization of histidine-rich proteins based on the single-step affinity adsorption of transition metal ions continues to be a suitable practice as a cost effective and a up scaled alternative to the to multiple-step chromatographic separations. In our previous work, we synthesised Porous Magnetic silica (PMS) spheres by one-step hydrothermal-assisted modified-stöber method. The obtained spheres were decorated with Ni(2+) and Co(2+), and evaluated for the capture of a H6-Tagged green fluorescence protein (GFP-H6) protein. The binding capacity of the obtained spheres was found to be slightly higher in the case Ni(2+) decorated PMS spheres (PMSNi). However, comparing with commercial products, the binding capacity was found to be lower than the expected. In this way, the present work is an attempt to improve the binding capacity of PMSNi to histidine-rich proteins. We find that increasing the amount of Ni(2+) onto the surface of the PMS spheres leads to an increment of the binding capacity to GFP-H6 by a factor of two. On the other hand, we explore how the size of histidine-rich protein can affect the binding capacity comparing the results of the GFP-6H to those of the His-tagged α-galactosidase (α-GLA). Finally, we demonstrate that the optimization of the magnetophoresis parameters during washing and eluting steps can lead to an additional improvement of the binding capacity.

Reversible aggregation and chemical resistance of magnetic nanoclusters for their recycling and repetitive use in industrial bioprocesses.

Magnetic nanoclusters are widely used as carriers for biomedical and bioindustrial applications. The chemical resistance of the nanoclusters is a key factor for the recycling the magnetic beads for a repetitive use in the industrial bioprocesses. In this work, a study of the chemical resistance of Fe2O3 silica-coated nanoclusters at different pH is presented. The use of Horizontal Low Gradient Magnetic Field (HLGMF) for the control and separation of the magnetic nanoclusters at diferent magnetic field gradients is also investigated. For these purposes Fe2O3 silica-coated nanoclusters are synthesised and characreized by SQUID, TEM, Zeta potential techniques. The magnetophoresis study was performed at 15 T/m and 30 T/m magnetic field gradients. Recycling aspects of the nanoclusters were estimated by evaluating their resistance to pH variation from acid to basic solutions of about pH 2.5 and 10.

Nanoparticle dispersion and electroactive phase content in polyvinylidene fluoride/Ni0.5Zn0.5Fe2O4 nanocomposites for magnetoelectric applications.

Ni0.5Zn0.5FeO4 ferrite/polyvinylidene fluoride composite films were prepared by a solution method and melt processing. As nanoparticle dispersion and polymer electroactive phase content are some of the key factors for improving magnetoelectric coupling in the composites, the dispersion of ferrite nanoparticles in the polymeric matrix was studied by preparing samples by two alternative dispersion routes: ultrasound and citric acid nanoparticle surfactation. The nucleation of the electroactive beta-phase of the polymer was observed in composites produced by nanoparticle dispersion by ultrasound. This fact avoids the need of stretching composites at elevated temperature in order to obtain the electroactive phase and obtain magnetoelectric composites. By this method, nevertheless, large nanoparticle agglomerates are obtained. Nanoparticle dispersion is largely improved by citric acid surfactation of the nanoparticles. On the other hand, the beta-phase of the polymer is not nucleated due to the modification of the nanoparticle-polymer interaction due to the presence of the surfactant.

Design and characterization of Ni2+ and Co2+ decorated Porous Magnetic Silica spheres synthesized by hydrothermal-assisted modified-Stöber method for His-tagged proteins separation.

The complete elimination of enzymes from the reaction mixture and the possibility of its recycling for several rounds result in great benefits, allowing the reduction of the enzyme consumption and their usability in continuous processes. In this work, it is evaluated the capture of a H6-tagged green fluorescence protein (GFP-H6) on porous magnetic spheres using the Co(2+) and Ni(2+) affinity adsorption as a possible cost-effective and up-scaled alternative way for the immobilization of His-tagged proteins. For this purpose, Porous Magnetic Silica (PMS) spheres were synthesized by one-step hydrothermal-assisted modified-Stöber method. The obtained spheres have a homogenous size distribution of 400 nm diameter. The γ-Fe(2)O(3) nanoparticles are homogenously distributed in the silica matrix. The obtained PMS spheres have a saturation magnetization of about 10 emu/g. Magnetophoresis measurements show a total separation time of 16 min at 60 T/m. The obtained PMS spheres were successfully and homogenously decorated with Co(2+) and Ni(2+) and then evaluated for the capture of a GFP-H6 protein. The results were compared with the performance of the commercial beads Dynabeads® His-Tag Isolation & Pulldown.

Simple analytical model for the magnetophoretic separation of superparamagnetic dispersions in a uniform magnetic gradient.

Magnetophoresis--the motion of magnetic particles under applied magnetic gradient--is a process of great interest in novel applications of magnetic nanoparticles and colloids. In general, there are two main different types of magnetophoresis processes: cooperative magnetophoresis (a fast process enhanced by particle-particle interactions) and noncooperative magnetophoresis (driven by the motion of individual particles in magnetic fields). In the case of noncooperative magnetophoresis, we have obtained a simple analytical solution which allows the prediction of the magnetophoresis kinetics from particle characterization data (size and magnetization). Our comparison with new experimental results shows good quantitative agreement. In addition, we show the existence of a universal curve onto which all experimental results should collapse after proper rescaling. The range of applicability of the analytical solution is discussed in light of the predictions of a magnetic aggregation model [Soft Matter 7, 2336 (2011)].