A facile way to fabricate manganese phosphate self-assembled carbon networks as efficient electrochemical catalysts for real-time monitoring of superoxide anions released from HepG2 cells

Quantification of superoxide anions (O 2 •− ) is significant in the monitoring of many serious diseases and the design of enzyme-mimic catalysts plays the main role in the development of non-enzymatic O 2 •− sensors. Herein, we proposed a facile self-assembly process to synthesize manganese phosphate modified carbon networks using three kinds of widely-used carbon materials (MWCNTs, NGS and GO) as pillar connectors. Characterizations demonstrate that manganese phosphate is widely dispersed inside and on the surface of carbon networks without visible morphology. Meanwhile, all three kinds of synthesized catalysts were successfully immobilized on the screen-printed carbon electrodes to evaluate the electrochemical performance of fabricated sensors. The results indicate that sensors based on Mn x (PO 4 ) y modified MWCNTs exhibit high sensitivity with an extremely low detection limit of 0.127   μM (S/N = 3) and a wide liner range of 0–1.817   mM (R 2 = 0.998). We further employed the recommended sensors in the real-time monitoring of HepG2 cells released O 2 •− under the stimulating of Zymosan (20   mg/mL). Noticeably, the proposed sensors exhibit not only sensitive response but also stable current steps upon different addition of Zymosan. The calculated concentrations of cell-released O 2 •− vary from 6.772 to 24.652   pM cell −1 for the Zymosan amount used in this work. The established novel sensors display low background current and signal noises, thus holding unique advantages in the trace analysis of O 2 •− in biological samples and in vivo environment.