2.2. Neuron Culture and transfection
All animal experiments were approved by the Animal Care and Use Committee of the Institutional Animal Committee of Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences. Primary neuron culture was performed according to the previous article.[17] Briefly, hippocampal neurons from embryonic day 18 (E18) Balbc rats (Cavens Lab Animal Co., Changzhou, China) were dissected and dissociated by trypsin, the single-cell suspension was plated on 12 mm 0.01% laminine-coated, 0.1% poly-D-lysine pre-coated coverslips at a density of 2,400 cells/cm2. The cells were cultured in Neurobasal media including 1% penicillin-streptomycin and 1% L-Glutamine supplemented with 2% B27 and 1% sodium pyruvate. Neuron transfection was operated after 5 days of culture. Each coverslip was renewed with merely Neurobasal media 4 hours in advance, followed by liposome transfection. The amount of vector was applied empirically to allow sparse transfected cells to be visualized.