Mesoporous SiO₂-(l)-lysine hybrid nanodisks: Direct electron transfer of superoxide dismutase, sensitive detection of superoxide anions and its application in living cell monitoring

The mesoporous SiO₂-(l)-lysine hybrid nanodisks have been synthesized via hydrolyte polycondensation of tetraethylortho-silicate in the presence of cetyltri-methylammonium bromide and (l)-lysine. The prepared hybrid nanodisks have a high surface area (570 m² g^-1) and ordered mesopores with the size of about 2.9 nm. Due to the presence of the biomolecule, (l)-lysine, the obtained hybrid nanodisks possess excellent biocompatibility. When superoxide dismutase (SOD) is immobilized on those hybrid nanodisks, the bioactivity of SOD can be effectively preserved, and the direct electrochemical behaviours of SOD are observed. Based on this result, an electrochemical biosensor for superoxide anions (O₂^-) is fabricated. This biosensor has a wide linear range, low detection limit, high sensitivity and selectivity for detecting O₂^- at a suitable potential (0.05 V). Furthermore, it can be exploited for monitoring O₂^- from living normal and cancel cells that directly adhered to the modified electrode surface, indicating that O₂ ^- may serve as a biomarker of cancer.