Abstract
This research prepared superparamagnetic nanoparticles surface modified with single strand DNA, which would selectively bind to target DNA molecules and formed two-dimensional magnetic clusters. Using high sensitivity magnetic measurement, the magnetic difference between the as-formed magnetic clusters and native magnetic nanoparticles was clearly observed, demonstrating the feasibility of using magnetism difference to prepare magnetic DNA probes. We prepared iron oxides magnetic nanoparticles by high temperature pyrolysis in oil phase. The hot-soup method was subsequently used to accomplish surface modification by thio-functional molecules. TEM and FT-IR were used to verify features of uniform particle size and surface functional group. The functionalized nanoparticles were reacted with Mn、Ni、Pb、Zn and Cu heavy metals for testing surface activities. Good recoveries obtained by ICPMS confirmed the expected surface activities. Two same-length and different-sequence ssDNA were bound to the functionalized nanoparticles using cross-linking reagent to form magnetic DNA probe. The magnetic DNA probe would selectively bind to target complementary DNA, which was confirmed as magnetic-DNA cluster by PAGE analysis. Hysteresis loop measurements of magnetic-DNA clusters and magnetic nanparticles by SQUID show significant differences in magnetization saturation (MS) and magnetization remanence (MR). The results evidence that the magnetic DNA probe is of potential to detect DNA by magnetism differences in biomedical analysis.