The Construction Of The Novel Sensing Platform Based On Porous Graphene Composites And The Detection For Releasing Of Hydrogen Peroxide From Living Cells

Hydrogen peroxide?H₂O₂?is the most common representative of reactive oxygen species?ROS?studied in physiological environments,mainly regulating protein synthesis,DNA damage,cell apoptosis,etc.Therefore,detection of H₂O₂ in cells and measurements of its dynamic release process from living cells are essential to provide reliable diagnosis of pathological conditions.Porous graphene?PGN?,which refers to graphene containing nanopores in the two-dimensional basal plane,has aroused great interest.PGN not only retains the excellent intrinsic properities of original graphene,but also improves mass transfer efficiency,enlarges specific surface area,increases the active sites.Moreover,the existing nanopores can effectively prevent aggregation of graphene sheets,and is beneficial of the adsorption.These merits make porous graphene?PGN?an excellent supporting material and make the opportunity for improving the properties of biosensors and promoting the development of biosensors effectively.This dissertation focused on the study of the enzyme biosensor and nonenzyme biosensor based on enzyme/porous graphene composite and metal nanoparticles/porous graphene composite,respectively.And the application for detection of H₂O₂ in cancer cells was also investigated.The main contents were summarized as follows:1.In this chapter,the prepared method of porous graphene was initially explored.We present the innovative synthesis of PGN using silver nanoparticles?AgNPs?etching.And PGN was characterized by different methods to prove that it has been synthesized successfully.Then a novel enzyme biosensor was fabricated by combining PGN and horseradish peroxidase?HRP?.The constructed electrode displayed good electrocatalytic activity toward H₂O₂ reduction,and the peak current was 4.8 times as large as that of bare glass carbon electrode,which attribute to that PGN with large specific area and good biocompatible was used to load on great amount of enzyme to increase the response current of H₂O₂.Moreover,the electrocatalytic mechanism of H₂O₂ reduction on HRP/PGN/GC electrode was also explored.2.From the first chapter,we found that the method of using silver nanoparticles?AgNPs?etching was effective.But from TEM image,we observed that the porosity of PGN was small.In this chapter,in order to obtain high porosity of PGN,we changed the surfactant and the ratio of AgNPs and GO.Then an enzymatic H₂O₂sensor based on PGN and HRP was also fabricated.The experimental results demonstrated that the constructed electrode exhibited excellent electrochemical performance toward H₂O₂ with a determination limit as low as 0.0267 nM and wide linear range of 7 orders of magnitude,which was superior to other H₂O₂electrochemical sensors.Most importantly,the outstanding features of PGN,combined with the excellent selective catalysis of HRP,enable this biosensor to be used for determining the release of H₂O₂ from living cells with satisfaction.3.In this chapter,the platinum nanoparticles?PtNPs?and PGN were combined skillfully by the carbothermic method,and the non-enzymatic sensor was fabricated.Scanning electron microscopy?SEM?investigations for the PtNPs/PGN composites indicate that Pt nanoparticles were embedded into porous graphene,something that was rarely reported.The experimental results demonstrated that this sensor exhibited excellent detection capability for H₂O₂,and a wide linear range from 6.0×10^-11 to6.49×10^-4mol/L was obtained with a limit of detection?LOD?of 2.0×10^-11mol/L.The outstanding performance of H₂O₂ was attributed that the pore structure of PGN can promote the electron transfer and platinum nanoparticles can catalyze the H₂O₂reduction.Finally,the application of this sensor was further explored in cancer detection and the kinetics of H₂O₂ releasing was also studied.