Fig. 5. (a) Current change value of the APOE4 electrochemical immunosensor for different protein including BSA, APOE2, APOE3, APOE4. (b) The current response of APOE4 electrochemical immunosensor for goat serum containing different concentration human APOE4. (c) The histogram of current change value of (b). The error bars represent relative standard deviation (n = 5).