Study On Novel Liposome Photoelectrochemical Biosensor

The detection principle of photoelectrochemical bioanalysis is that the recognition element has a biometric interaction with the target biomolecule under the condition of a certain wavelength of light,which makes the electrical signal change.Photoelectrochemical biosensors have attracted more attention in life analysis,such as enzyme sensing,immunoassay,DNA analysis and cell analysis,because of their advantages such as low price,simple device,easy miniaturization,high sensitivity and low background signal.Generally speaking,the construction of photoelectrochemical sensors mainly starts from two aspects:the construction of photoelectric active materials and the construction of analytical strategies.At present,the commonly used optoelectronic active materials are organic and inorganic photoactive materials,and their composite materials.The commonly used analytical strategies include energy transfer,steric hindrance,sensitization effect,in situ generation of electron donors and active substances as markers.Liposome is a kind of spherical vesicle composed of phospholipid and cholesterol with phospholipid bilayer structure.Some lipophilic substances can be encapsulated in the phospholipid bilayer of liposomes,while some hydrophilic substances can be encapsulated in the spherical vesicles of liposomes.At present,liposomes are enthusiastically used as drug carriers,which have the functions of targeted drug delivery in vivo,reducing drug side effects,locating,timing and speed release of drugs and so on.This paper focuses on liposomes encapsulating water-soluble substances and realizing the immune sandwich complex by glutaraldehyde coupling method and secondary antibody connection,so as to realize the study of photoelectrochemical biosensor.Based on this,this paper has carried out the following aspects of work:1. Study on photoelectrochemical immunoassay of sensitive liposomes based on AA and glucose double signalsIn this work,the cavity of liposome was used to encapsulate two kinds of water-soluble small molecules AA and glucose.Among them,AA sensitized nano-granular titanium dioxide to enhance the photocurrent,so as to achieve the quantitative detection of prostate specific antigen,while glucose was quantitatively detected by blood glucose meter.Under the interference of brain natriuretic peptide,carcinoembryonic antigen,human fatty acid binding protein,human phospholipase A₂and other antigens,the biosensor has obvious selectivity for prostate specific antigen.Prostate specific antigen has high tissue and organ specificity,and it is also the preferred marker for the diagnosis of prostate cancer.The innovation of this system is to use the cavity of liposomes to detect two kinds of signals.Titanium dioxide,the base material used in the system,was deposited on ITO by the reaction of boric acid and ammonium fluorotitanate at 25 degrees for 48 hours,then annealed and sintered.It can be found to be granular by SEM characterization.Titanium dioxide is an anodic semiconductor material.The dihydroxyl on AA can form a five-membered ring with Ti,so that electrons can be quickly transferred to titanium dioxide,and then transferred to the ITO electrode,so as to achieve the increase of photocurrent.2. Preparation of polypyrrole@Bi₂WO₆organic-inorganic heterojunction and its application in photoelectrochemical immunoassayIn this work,the organic-inorganic heterojunction composed of inorganic semiconductor material Bi₂WO₆and organic semiconductor material polypyrrole was used as the substrate to detect creatine kinase.Firstly,Bi₂WO₆was synthesized by hydrothermal synthesis of Bi?NO₃?₃·5H₂O and Na₂WO₄·2H₂O,and then the Bi₂WO₆of 5mg/m L was coated on the newly prepared ITO and annealed in muffle furnace for 1 hour.Then,polypyrrole Bi₂WO₆/ITO was assembled by photocatalytic oxidative polymerization of polypyrrole PPy.The specific method is to insert the Bi₂WO₆/ITO electrode into a certain concentration of pyrrole aqueous solution,and then photooxidize under the condition of 500W xenon lamp for 3 hours to obtain PPy/Bi₂WO₆/ITO.At this time,the organic-inorganic heterostructure is formed,and the photocurrent increases obviously.Finally,creatine kinase was detected by immune sandwich complex.The principle is that 5-bromo-4-chloro-3-indole phosphate under the condition of streptavidin labeled alkaline phosphatase.It is oxidized into biological precipitation,which covers the surface of the electrode with PPy/Bi₂WO₆/ITO so that it can not contact with the solution,so that the photocurrent decreases obviously.The detection object of this system is creatine kinase,which can be used for the diagnosis of cardiomyopathy and skeletal muscle diseases.3. Study on photoelectrochemical immunoassay based on dopamine bond and affinity of cadmium sulfide liposomes with phenylboric acidIn this work,inorganic quantum dot cadmium sulfide is an anodic semiconductor material.In PBS solution containing 0.1M AA,AA is used as an electron donor,so a large photocurrent can be measured.The homeopathic dihydroxyl formed by dopamine and phenylboric acid can be broken under certain acidic conditions,resulting in a significant decrease in photocurrent.If it is incubated again,the photocurrent can be increased again,and the cycle is reversible to achieve the increase of photocurrent.In immunoassay,the liposome encapsulating Dopa-Cd S is first connected with a certain concentration of glutaraldehyde,then the aldehyde group at the other end of glutaraldehyde is coupled with the second antibody,that is,the so-called glutaraldehyde coupling,and then the excess aldehyde group is blocked by BSA,and finally the secondary antibody and BSA which can not be connected are centrifuged.The detection object of this system is cancer blank antigen,which can be used as a specific marker for the diagnosis of early rectal and colon cancer.