Preparation of ZnFe2O4 nanoparticles in the template of silk-fibroin peptide and their neuro-cytocompability in PC12 cells

There is an urgency to prepare non-neurotoxic nanoparticles (NPs) as MRI contrast agent. We prepared ZnFe2O4 NPs with monocrystal structure in the template of silk-fibroin (SF) peptide at room temperature. Analyses of their crystallite size and NPs diameter after the growth of 1 d and 8 d indicated that SF peptide could promote nucleation, growth and dispersion of NPs. Results of EDS, Raman and TG proved that there was 4 wt% of the chemical composition of SF in as-prepared NPs. A possible growth mechanism of ZnFe2O4 NPs in the template of SF is proposed. The saturation magnetizations of NPs with SF (SF-NPs) were about 15 and 30 emu/g for 1 and 8 d, respectively. SF-NPs obviously promoted the viability of PC12 cells at NPs concentration of 0.0625 mg/mL in 2 d and 5 d of co-culture. Analysis of neurite length indicated no significant decreases of the experimental groups at different SF-NPs concentrations (from 0.0625 to 0.5 mg/mL) after 5 d cell co-culture, because SF peptide coating could slow the release of iron/zinc ions from NPs. Furthermore, SF-NPs did not destroy the organelles, karyotheca and the neurite using the observation in the cell ultrathin sections. Based on their good magnetic property and neuro-cytocompatibility, the potential application of ZnFe2O4 NPs with SF as MRI contrast agents would be envisioned.