(1) DMF stimulation of SPIO-Au NPs significantly upregulated β3-tubulin expression compared to NPs alone and SMF + NPs (P < 0.01 and P < 0.001, respectively) (2) SMF and DMF stimulation of NGF-SPIO-Au NPs significantly upregulated β3-tubulin expression compared to NGF-SPIO-Au NPs alone (P < 0.01 and P < 0.05, respectively) while there was no significant upregulation of β3-tubulin expression between SMF and DMF stimulations