Evaluation of the magnetic field requirements for nanomagnetic gene transfection

Abstract

The objective of this work was to examine the effects of magnet distance (and by proxy, field strength) on nanomagnetic transfection efficiency.

Methods: non-viral magnetic nanoparticle-based transfection was evaluated using both static and oscillating magnet arrays.

Results: Fluorescence intensity (firefly luciferase) of transfected H292 cells showed no increase using a 96-well NdFeB magnet array when the magnets were 5 mm from the cell culture plate or nearer. At 6 mm and higher, fluorescence intensity decreased systematically.

Conclusion: In all cases, fluorescence intensity was higher when using an oscillating array compared to a static array. For distances closer than 5 mm, the oscillating system also outperformed Lipofectamine 2000™.

Keywords: magnetic field; magnetic nanoparticle-based gene transfection; magnetic nanoparticles; non-viral gene delivery.

Fig. 1

Proposed mechanism of oscillating nanomagnetic transfection (After ref. (17). Plasmid DNA or siRNA is attached to magnet nanoparticles and incubated with cells in culture (left). An oscillating magnet array below the surface of the cell culture plate pulls the particle into contact with the cell membrane (i) and drags the particles from side-to-side across the cells (ii), mechanically stimulating endocytosis (iii). Once the particle/DNA complex is endocytosed, proton sponge effects rupture the endosome (iv) releasing the DNA (v), which then transcribes the target protein (vi).

Fig. 2

Redcliffe MagScan image of a nanoTherics Ltd. magnet array obtained at 3 mm distance between the scanning probe and the magnet surface.

Fig. 3

Luciferase activity in NCI-H292 human lung mucoepidermoid carcinoma cells transfected with pCIKLux luciferase reporter construct using Chemicell Polymag particles (‘no magnet’, ‘static field’ and ‘oscillating field’), Lipofectamine (LF2000) and DNA (control).

Fig. 4

Luciferase activity in NCI-H292 cells transfected with pCIKLux luciferase reporter construct using Chemicell Polymag particles (‘static field’ and ‘oscillating field’).