Study On Detection Method Of Milk Lipase Biosensor

As a type of new detection technology,biosensing technology is developed from interdisciplinary interaction,and it mainly combined with biology,chemistry,physics and electronics.As a newly emerging sensing technique,photoelectrochemical（PEC）bioanalysis has many advantages of high sensitivity,good selectivity,low cost and fast analysis speed,it has been widely used in many fields,such as food safety inspection,clinical diagnosis and biomedicine.When the（PEC）sensor is working,photoelectrochemically active species are excited by light on the electrode,and the detection signal is photocurrent.PEC bioanalysis has obtained extensive attention owing to low background signal and easy miniaturization.It has become a research topics in the field of bioanalytical chemistry.Compared with single nanomaterials,composite nanomaterials have the multiple advantages of compatibility.In this paper,three PEC biosensors based on nanocomposites were constructed and were applied to the analysis of bioactive substances.1.A novel ultrasensitive PEC immunosensor for determination of Cardiac troponin（c Tn I）was developed upon dual inhibition effect of Ag@Cu₂O core-shell nanoparticles（NPs）toward Cd S sensitized the facets of titanium dioxide nanosheet（Ti O₂/Cd S）.Ti O₂/Cd S QDs electrode was successfully constructed.Compared with the Ti O₂ electrode alone,the photocurrent increased by 2.8 times.The Ti O₂/Cd S electrode not only provided stable and excellent basal signal,but also provided binding sites to immobilize capture antibodies（Ab₁）.To improve sensor sensitivity,Ag@Cu₂O core-shell NPs were used as labels,owning to competitive absorption of light and consumption of electron donor,less light energy and electron donors arrived at the Ti O₂/Cd S electrode;the remarkable steric hindrance effect of Ag@Cu₂O core-shell NPs labeled secondary antibodies（Ag@Cu₂O core-shell NPs-Ab₂）conjugates obstructed the transfer of electrons and diffusion of the electron donors to the photoelectrode surface,leading to further decrease of photocurrent.The immunosensor have a sensitive response to c Tn I in a liner range of 0.01 ng·m L^-1 to 50ng·m L^-1 with a low detection limit of 6.7 fg·m L^-1,and exhibited high sensitivity and good stability.2.A new label-free aptasensor with high visible-light PEC activity was fabricated for the detection of AFB1 based on N-doped graphene quantum dots（N-GQDs）sensitized Zn doped Sn S₂（Zn-Sn S₂）nanocomposites.N-GQDs sensitized Zn-Sn S₂ showed eminent PEC performance.The specific binding between AFB1 aptamer and AFB1 resulted in the linear decrease of photocurrent with the increase of logarithm of AFB1 concentration in the range of 0.01 ng·m L^-1 to 20 ng·m L^-1 with a detection limit of 3 pg·m L^-1.3.2-ascorbate（AAP）,which could be hydrolyzed by lipase to produce ascorbic acid（AA）,was synthesized.Lipase belongs to the genus pseudomonas fluorescens in milk.AAP was applied to the construction of PEC lipase biosensor.（1）A PEC sensor was fabricated to detect lipase activity in homogeneous solution.Ti O₂/Cd S QDs electrode were prepared to detect the AA concentrations.The different AA concentrations generated difference electrical signals in the solution,which reflected the different activity of lipase.（2）A PEC biosensor based on Ti O₂/N-GQDs/Cd S QDs/Lipase was developed.The sensor could sensitively detect AA within the range of 0.1～0.0001 mol·L^-1.This work has provided a new method for the detection of enzyme activity.The enzyme activity could be obtained according to the enzyme concentrations,electrical signal strength and time.