Application Of Gold Nanoparticles And Its Composite In The Biomedical Sensing For Homocysteine

Homocysteine is an important amino acid containing sulfhydryl groups.It is an important intermediate product produced during the metabolism of methionine and cysteine.It does not participate in protein synthesis.Under normal circumstances,the concentration of homocysteine is maintained at a normal level because homocysteine can be decomposed in the body.However,primary or secondary reasons can influce the metabolic process of homocysteine and increase its concentration,which may lead to hyperhomocysteinemia.Hyperhomocysteinemia can directly or indirectly cause vascular endothelial cell damage,promote the proliferation of vascular smooth muscle cells,affect the oxidation of low-density lipoprotein,enhance platelet function,and promote thrombosis.Therefore,homocysteine has been regarded as an important indicator of human health.The highly sensitive,rapid and accurate detection of homocysteine will provide important auxiliary information for the diagnosis of clinically related diseases.At present,a variety of methods have been proposed to realize the accurate detection of homocysteine in biological samples.Among them,biomedical sensing method has attracted the most attention because of its simple operation,low cost,fast response,high sensitivity,high sensitivity and no derivatization is required.Nanomaterials exhibit many unique physical and chemical properties due to their small size effect,surface effect,quantum size effect,macroscopic quantum tunneling effect and dielectric confinement effect.Thus,they have been widely used as a sensitive functional material for coustructign biomedical sensors.In this paper,gold nanoparticles and carbon nanomaterials(graphene and acetylene black)have been applied to construct nanosensing interface and fabricate effective homocysteine biomedical sensor.The application of these biomedical sensors has been studied and the main contents are as follows:1.Biomedical sensing of homocysteine based on gold nanoparticles modified glassy carbon electrode: the gold nanoparticles were electropolymerized on the surface of the glassy carbon electrode by cyclic voltammetry scanning to form a uniform and stable film.Due to the good biocompatibility,conductivity,high surface chemical activity and catalytic activity of gold nanoparticles,and the good affinity between gold nanoparticles and the sulfhydryl group in the homocysteine structure.The sensor has higher sensitivity and shorter response time.At the mean time,the sensor has good reproducibility and stability,and high accuracy.2.Biomedical sensing of homocysteine based on gold nanoparticles/acetylene black-dihexadecyl phosphate modified glassy carbon electrode: A homocysteine electrochemical sensor based on gold nanoparticles/acetylene black-dihexadecyl phosphate composite membrane was prepared by electropolymerizing gold nanoparticles onto the surface of a glassy carbon electrode modified with acetylene black-dihexadecyl phosphate(DHP).Due to the large specific surface area and strong adsorption capacity of acetylene black,and the good conductivity and strong coordination ability of gold nanoparticles,the overpotential of homocysteine on the sensor has been greatly reduced.At the same time,the oxidation peak current of homocysteine has been greatly improved.The modified electrodes were characterized by electrochemical techniques such as cyclic voltammetry and linear sweep voltammetry.In addition,the electrochemical reaction mechanism of homocysteine on the sensor was discussed,and satisfactory results were obtained.3.Biomedical sensing of homocysteine based on gold nanoparticles modified graphene carbon paste electrode: A hand made graphene carbon paste electrode was prepared and gold nanoparticles were deposited on its surface to fabricate a novel homocysteine biomedical sensor.Characterization results obtained from electrochemical scanning electron microscopy technology show that a large number of gold nanoparticles can be observed on the surface of the gold nanoparticle-graphene nanocomposite film electrode.The whole electrode surface presents a loose and porous structure,which is conducive to the enrichment of homocysteine on the electrode surface and the improvement of the sensing sensitivity.Furthermore,the good conductivity of gold nanoparticles and graphene and accelerate the electron transfer between homocysteine and the electrode,and shorten the response time of the sensor.In addition,through standard addition method,the average recovery rate of homocysteine in serum samples was measured using the sensor as 97.3%,which indicates the good accuracy of the senor.In short,this thesis constructed three homocysteine biomedical sensing interfaces based on gold nanoparticles and their complexes.The first construction based on gold nanoparticles modified glassy carbon electrode sensing interface,the operation is simple and controllable,but the sensitivity of the detection of homocysteine needs to be improved.Therefore,another nanomaterial,acetylene black,was introduced in the construction of the second sensor interface.Compared with pure gold nanoparticles,the gold nanoparticle-acetylene black nanocomposite film exhibits better catalytic performance.To a certain extent,the sensitivity of the sensor is improved,but acetylene black as a carbon nanomaterial needs to go through a more complicated functionalization and solvent dispersion process before it is modified on the electrode surface.In order to avoid this tedious operation,the third nano-sensing interface was developed.In the process of constructing the sensor interface,the carbon nanomaterial graphene is used directly without any treatment,which greatly simplifies the operation and saves time.At the same time,it provides a basis for the miniaturization of homocysteine biomedical sensors.