Development Of New Biosensor System Based On Nanomaterials

Nano-materials have unique light,electricity,magnetic properties so exhibiting some chemical properties such as catalytic activity.Compared with natural enzymes,nanomaterial have the advantages of simple production,preferential anti-degeneration ability,high catalytic activity,low cost and easy storage.However,the nanomaterial has the disadvantages of low catalytic efficiency,limited catalytic type and the specificity of substrate selection is not high.So,in order to improve the catalytic efficiency,researchers develop nanomaterials which can activate natural enzymes.This way not only improve the catalytic efficiency but also can expand the application of nanomaterials and natural enzymes.So,this paper studies the nanomaterials triggering the peroxidase activity of horseradish peroxidase?HRP?and applied to analysis.The main contents are as follows:?1?Tyrosinase?TYR?stimulates the biocatalyzed hydroxylation of L-tyrosine to dihydroxyphenylalanine?L-DOPA?containing enediol-ligands,which can be captured easily by the undercoordinated surface Ti atoms on titanium dioxide nanoparticles TiO₂ NPs due to the formation of DOPA-Ti IV charge transfer?CT?complex.The TiO₂/DOPA complex act as a nano-mediator to switch on the activity of HRP under visible light???400 nm?irradiation without adding hydrogen peroxide?H₂O₂?.Therefore,an enzymatic cascade reaction with triple amplification effects is developed for probing the activity of TYR with high sensitivity:TYR–mediated biocatalysis generates L-DOPA?the first amplification step?activated TiO₂ NPs and,in turn,the formed TiO₂/DOPA produces multiple reactive species such as photogenerated holes?h⁺?and superoxide anion(O₂^·-)?the second amplification process?to activate a second enzyme?HRP?for the catalyzed oxidization of TMB?the third amplification process?,resulting in powerful signal amplification.The proposed strategy can be used to detect the TYR activity and further apply this method to immunoassay.?2?The synthesized graphite g-C₃N₄ nanocomposite not only have light-induced mimic enzymatic activity and can trigger the activity of HRP under visible light irradiation,which can amplifies the detection signal.The combination g-C₃N₄ trigger the activity HRP under visible light???400 nm?irradiation with tyramine signal amplification?TSA?was used to construct a new immunosensor for the detection of?-fetoprotein?AFP?.The immunosensor has a wide detection range and high sensitivity and successfully applied inhuman serum sample.?3?The highly solubile and photocatalytic carbon quantum dot?CDs?could oxidize the typical substrate of TMB of the HRP under visible light???400 nm?causing the color signal.The coordination function between CDs and copper ions(Cu²⁺)has been prepared and applied to be turn-on colorimetric probe for the detection of pyrophosphate?PPi?.It was confirmed that the introduction of Cu²⁺into CDs solution resulting the assembly of CDs and will suppress the oxidise mimicking activity of CDs.Upon addition of PPi into the above solution,the disassembly of the CDs due to the competitive binding of PPi with Cu²⁺and the mimic enzymatic activity of CDs recovery.Thus,CDs can be used to detect PPi with high selectivity and sensitivity.