Nicking site enzyme assisted catalytic hairpin assembly based scaffold for sensitive monitoring of miRNA-21

•PSGGSE has tunable porosity and improved interface stability via added the SnO2.•The 1-(4-cyanophenyl)guanidine provides more sites for of Na+ transport.•This new type of composite gel electrolyte exhibits good cycling stability.•The PSGGSE has a high ionic conductivity of 0.232 mS cm−1 at 70 °C.