Studies Of The Third-Generation Electrochemical Biosensors Based On Inorganic Nanosheets

Much attention has been devoted to the development of the third-generation electrochemical biosensor based on direct electrochemistry of enzymes.It is expected to find a simple,reliable and effective immobilization strategy to retain high activity of the immobilized biomolecules and allow efficient electron transfer between the electrode and a redox protein.In this paper,the nanosheets(layered double hydroxide nanosheets and graphite nanosheets) were used to immobilize myoglobin(Mb),horseradish oeroxidease(HRP),hemoglobin(Hb) or glucose oxidase(GOD) and investigate the electrochemical properties.The main contents of the thesis are given as follows:1.Zn-Al Layered double hydroxide nanosheets(Zn-Al-LDHNS) were firstly applied to the immobilization of Mb as a support matrix.Mb almost retained bioactivity in the film.The electrochemical results revealed that LDHNS could improve greatly the direct electrochemistry of Mb,while layered double hydroxide nanoparticles(LDHNP) can not achieve the direct electrochemistry of Mb.The catalytic ability of the protein toward the reduction of H₂O₂ was also studied and a third-generation H₂O₂ biosensor was fabricated.2.HRP has been intercalated into Ni-Al-LDHNS by delamination and restacking,and the direct electron transfer between the intercalated HRP and the underlying electrode was studied for the first time.HRP intercalated into Ni-Al-LDHNS retained its native secondary structure.The HRP-Ni-Al-LDHNS /GCE showed good electrocatalytic activity in the reduction of both H₂O₂ and TCA.The resulting biosensor showed excellent analytical performance.3.A novel nanosheets GNS was first successfully combined with Nafion and Hb to construct an afforded and highly sensitive mediator-free H₂O₂ and NO₂^- biosensor.Hb retained its native secondary structure in the GNS composite film,and exhibited facilitated direct electron transfer and good bioactivity.The prepared H₂O₂ biosensor displayed high sensitivity,wide linear range,low detection limit,fast response,good reproducibility, selectivity and long-term stability.4.The direct electrochemistry of GOD immobilized in the exfoliated graphite nanoplates(GNS) Nafion composite film was investigated for the first time.The direct electron communication between GOD and electrode was achieved with a very fast electron transfer rate(12.6 s^-1).The prepared glucose biosensor displayed high sensitivity,fast response,good reproducibility,good selectivity and long-term stability.