Electric field-induced alignment of Ag/Au nanowires for ultrasensitive in situ detection of Interleukin-6

Interleukin-6 (IL-6) is a key parameter and critical role in cancer progression. However, for detection of IL-6 in colorectal cancer diagnosis, developing a sensitive biosensor is necessary and very important. In this paper, to enhance the sensitivity of IL-6 electrochemical biosensor, the electric field was used to orient arrangement of silver nanowires (AgNWs) to be free-standing AgNWs electrode. Gold nanoparticles (AuNPs) were electro-reduced around the surface of each AgNWs to solve the rapid oxidization problem of the AgNWs at very low potential (<70 mV) during the electrochemical detection. Oxidation peak current of the free-standing AgNWs/AuNPs electrode only decreased by 5% after 500 scanning cycles, while the free-standing AgNWs electrode without AuNPs decreased by 90.7% after 8 CV scanning cycles. The oxidation peak current of free-standing AgNWs/AuNPs electrode was 500 times of bare electrode. This biosensor showed a wide linear range from 0.001 ng ml⁻¹ to 100 ng ml⁻¹ and a low detection limit of 0.322 pg ml⁻¹ for IL-6. In the end, IL-6 secreted by Caco-2 cell was detected by the fabricated biosensor which integrated into the gut-on-a-chip. IL-6 secretion achieved 11.3 pg ml⁻¹ during 10-days culturing.