Magnetic nanoparticles offer several advantages for isolation of biological materials. Since they are broadly used in diagnostic immunoassays and in various reactions involving enzymes, proteins, and DNA, this study considers the interaction of four surface modified magnetic microparticles with selected DNA fragments. The magnetic microparticle precursors are prepared by reduction of from iron (III) nitrate and sodium borohydride in ammonia solution. Different surface modifications, named as MAN 37, MAN 127, MAN 158 and MAN 164 were obtained by targeted chemical treatments. The zeta potential and particle size measurements were performed in a zetasizer MALVERN instrument. All considered magnetic microparticles are characterized by positive zeta-potentials, while the DNA fragments in solution show an approx. zeta-potential of -0.22 mV. All the particles were polycharged. MAN 37 and MAN 127 reveal the highest initial zeta potentials. Upon exposure to DNA, MAN 37 and MAN 127 particles lowered their zeta-potential near zero, meanwhile due to the DNA binding, in the case of MAN 164 the zeta potential decreases until -1.25 mV. All particles considered are classified as monodisperse systems. MAN 37 showed the smallest sizes of approx. 0.5 μm and almost no difference in size toward DNA exposure. MEN 158 distinguished for their initial high size of approx. 3.75 μm compared to MAN 127 and MAN 158, possessing sizes of approx. 3 μm each. MAN 164 particles exhibit the biggest change in contact to DNA, from approx. 3.0 μm up to 5 μm when exposed to DNA fragments. All results were confirmed by quantitative real-time PCR.Keywords: Magnetic micro particles, DNA binding, zeta potential, particle size
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