Promoting DNA loading on magnetic nanoparticles using a DNA condensation strategy

Maximizing DNA loading on magnetic nanoparticles (MNPs) is crucial for their successful utilization in gene transfer, DNA isolation, and bio-analytical applications. This enhancement is typically achieved by altering particle size and surfaces as well as charge density and ionic strength. We demonstrate a novel route for promoting DNA loading on amino-modified silica-coated magnetic nanoparticles (ASMNPs) by prior condensation of elongated DNA to a compact globule before adsorption. The enhanced DNA-loading capacity, as demonstrated by a reduction in the number of ASMNPs needed to achieve complexation, was presumably due to the elimination of DNA wrapping around nanoparticles and substantially reduced electrostatic interactions of DNA with nanoparticles because the compacted DNA globule conformation decreases its exposed surface charge. The maximum loading capacity of ASMNPs for condensed DNA was 4.4 times greater than that for elongated coiled DNA, achieving the highest ever reported value of 385 μg mg(-1). Practical applications for plasmid DNA isolation from cleared lysate confirmed the reliability of the proposed method.