Andrej Krafcik

Application of Pulsed Magnetic Ponderomotive Force for Intra-Cellular Gene Delivery

A novel method of the aerosolized gene delivery is proposed, and its feasibility is computationally analyzed. Aerosolized DNA or siRNA attached to magnetic particles can be accelerated using ponderomotive force to high velocities in a pulsed magnetic fleld of a solenoid and e-ciently delivered to cell culture or to the lung epithelium. The proposed noninvasive method of intra-cellular gene delivery can be considered as a combination of principles of classical high-pressure air jet gene delivery with magnetophoresis.

Proton Gradients as a Key Physical Factor in the Evolution of the Forced Transport Mechanism Across the Lipid Membrane

A critical phase in the transition from prebiotic chemistry to biological evolution was apparently an asymmetric ion flow across the lipid membrane. Due to imbalance in the ion flow, the early lipid vesicles could selectively take the necessary molecules from the environment, and release the side-products from the vesicle. Natural proton gradients played a definitively crucial role in this process, since they remain the basis of energy transfer in the present-day cells. On the basis of this supposition, and the premise of the early vesicle membrane’s impermeability to protons, we have shown that the emergence of the proton gradient in the lipid vesicle could be a key physical factor in the evolution of the forced transport mechanism (pore formation and active transport) across the lipid bilayer. This driven flow of protons across the membrane is the result of the electrochemical proton gradient and osmotic pressures on the integrity of the lipid vesicle. At a critical number of new lipid molecules incorporated into the vesicle, the energies associated with the creation of the proton gradient exceed the bending stiffness of the lipid membrane, and overlap the free energy of the lipid bilayer pore formation.

Comparative magnetic field measurements for homogeneity adjustment of magnetic resonance imaging equipments

The goal of this paper is to demonstrate three methods for static magnetic field measurement on a whole body magnetic resonance imager. The measured data are serving for computation of feeding currents of correcting coils for the static magnetic field used in NMR imaging. The methods suggest to measure the magnetic field in selected points twice: 1. correcting coils are switched off and 2. measurement of magnetic field changes caused by switching on the feeding current of particular correcting coil in each of selected measuring points. Measurements are realized using: magnetometer based on Hall effect, NMR point magnetometer and gradient echo imaging method applied to circular test tubes. All three measurements measure magnetic field on a circle (12 measuring points) and one point in the center. A set of linear equations, determination of a target function and optimization computations are procedures that provide optimal values of currents for correcting coils. Results of all three methods are compared and discussed. The proposed method is suitable for periodic testing and magnet in homogeneities correction for MRI magnets.

Coupled Nernst-Planck and Navier-Stokes equations for incompressible laminar flow of magnetic beads through bifurcation with magnetic stent

Presented paper deal with theoretical model of magnetic vascular stent in vessel bifurcation. Magnetic fluid flow was described as laminar incompressible continuum of many-bead system, using magnetic variant of Nernst-Planck equation coupled with Navier-Stokes equation, solved numerically by finite element method. Results are showing on reduction of magnetic bead flow rate through treated bifurcation arm by capturing of particles to the luminal surface of this stented vessel.