Biosensor Researches Based On The Synergistic Effect Of Nanopourous Gold And Enzyme

Biosensors are novel methods for quantitative analysis of substances that possess many unique advantages.In clinical area,biosensors are applied in detecting different compounds in human serum,benefiting the miniaturization and cost control of medical devices.For environmental protection,biosensors are widely used in fields such as water quality monitoring,improving many shortcomings of traditional water quality monitoring equipments.However,the existing biosensors showed poor environmental adaptability,easy inactivation,poor selectivity,and other defects,restricting the further development of biosensors.Meanwhile,the interaction of enzyme and its immobilization material still needs further research.In this study,a glassy carbon electrode(GCE)was modified with lipase-nanoporous gold(NPG)biocomposite(denoted as lipase/NPG/GCE).Triglycerides can be hydrolyzed into glycerol,fatty acids,and protons by lipase,changing the pH of solution in three-electrode cell.The redox peak currents of NPG can be sensitively changed with the changing of solution pH.Therefore,triglycerides detection is achieved by the detection of the changes of NPG reduction peak currents using the lipase/NPG/GCE bioelectrode.Linear responses were obtained for tributyrin concentrations ranging from 50 to 250 mg dL-1 and olive oil concentrations ranging from 10 to 200 mg dL-1.The value of apparent Michaelis-Menten constant for tributyrin was 10.67 mg dL-1 and the detection limit was 2.68 mg dL-1 towards tributyrin.Further,the lipase/NPG/GCE bioelectrode had strong anti-interference ability against urea,glucose,cholesterol,and uric acid as well as a long shelf-life.For the detection of triglycerides in human serum,the values given by the lipase/NPG/GCE bioelectrode were in good agreement with those of an automatic biochemical analyzer.These properties along with a long self-life make the lipase/NPG/GCE bioelectrode an excellent choice for the construction of triglycerides biosensor.Promoting the electrocatalytic oxidation of glucose is crucial in glucose biosensor design.In this study,nanoporous gold(NPG)was selected for glucose oxidase(GOx)immobilization and glucose biosensor fabrication because of its open,highly conductive,biocompatible,and interconnected porous structure,which also facilitates the electrocatalytic oxidation of glucose.The electrochemical reaction on the surface of the resulting GOx/NPG/GCE bioelectrode was attributed to the co-catalytic effect of GOx and NPG that offered better catalysis activity than each of GOx or NPG.A surface-confined reaction in a phosphate buffer solution was observed for the bioelectrode during cyclic voltammetry experiments.Linear responses were observed for large glucose concentrations ranging from 50?M to 10 mM,with a high sensitivity of 12.1?A mM-1cm-2 and a low detection limit of 1.02?M.Furthermore,the GOx/NPG/GCE bioelectrode presented strong anti-interference capability against cholesterol,urea,tributyrin,ascorbic acid,and uric acid,along with a long shelf-life.For the detection of glucose in human serum,the data generated by the GOx/NPG/GCE bioelectrode were in good agreement with those produced by an automatic biochemical analyzer.These unique properties make the GOx/NPG/GCE bioelectrode an excellent choice for the construction of a glucose biosensor.Aromatic compounds,such as phenols and aromatic amines,are environmental contaminants suspected of posing human health risks.For phenols and aromatic amines reliable detection,promoting selectivity and sensitivity for phenols and aromatic amines is crucial in biosensor design.Here,a biosensor combined the advantages of both enzymatic and nonenzymatic electrochemical sensors is constructed.Nanoporous gold(NPG)is selected as an enzyme carrier for horseradish peroxidase(HRP)biosensor fabrication due to its three-dimension structure with unique properties.It is firstly discovered that NPG can achieve electrochemical oxidation for phenols and aromatic amines.Based on the co-catalytic effect of HRP and NPG towards phenols and aromatic amines,better sensing performance was achieved as a result of enhanced electrochemical oxidation signal.Thus,the electrochemical reaction on the resulting HRP/NPG/GCE bioelectrode is attributed to the co-catalysis of HRP and NPG.For the detection of catechol(Cat),4-aminophenol(p-AP),o-phenylenediamine(o-PD),and p-phenylenediamine(p-PD),linear responses are observed in large concentration ranges with high sensitivities and low detection limits.Further,the HRP/NPG/GCE bioelectrode presents strong reproducibility,specificity,selectivity,and anti-interference capability in detecting the mixture of phenols and aromatic amines along with a long shelf-life.Especially,and the real sea water sample analysis was achieved.These unique properties make the HRP/NPG/GCE bioelectrode an excellent choice for phenols and aromatic amines reliable detection.Based on above results,enzyme and its immobilization materials could exhibit synergistic effect or co-catalytic effect during electrochemical detection,which could provide enhanced catalysis and higher sensitivity.Such biosensor combines the advantages of both enzymatic and nonenzymatic sensor.NPG possess excellent biocompatibility for enzyme immobilization as well as electrocatalytic activities towards many substances.Due to the synergistic effect of NPG/Enzyme,the performance of biosensors would be greatly improved in practical applications.