Ultrasensitive electrochemical immunosensor for HE4 based on rolling circle amplification

► AuNPs/chitosan-TiC/nanocomposite film modified ITO electrode. ► Rolling circle amplification and electroactive indicator doxorubicin hydrochloride. ► Response amplification mechanism of the novel electrochemical sandwich-immunosensor. ► Ultrasensitive detection was realized from 3 to 300 pM with the detection limit 0.06 pM. ► This method exhibits good stability and specificity to HE4.