Fabrication And Application Of Photocatalysis-Induced Renewable Field-Effect Transistor Biosensors

With the continuous development of biomedicine,more and more new medical diagnosis technologies are emerging.Among these technologies,the biosensor,an emerging technology,has been widely used in the field of life science and medical laboratory.The field-effect transistor?FET?biosensor is one of the important members of the biosensors.It has a lot of advantages,such as label-free detection,high sensitivity and specificity,in detecting various biological molecules,making it very important in the field of biosensors.During the development of the nanomaterials,a mass of new nanomaterials,such as silicon nanowire?SiNW?,carbon nanotube?CNT?,molybdenum disulfide?MoS₂?and graphene,have arisen and been used to fabricate the nanomaterial-based FET biosensors.However,the present FET biosensors were manufactured by complicated and cost-effective micro and nano fabrication technology,and the manufactured FET chips are always for one time usage.Hence,it is very important to build the FET biosensor which can be regenerated after detection because the residual analyte is difficult to clean in the practical application of clinical medicine.In these materials,graphene is the most widely applied in the FET biosensor recently because graphene has many merits compared with othermaterials.For example,graphene has high surface area,great conduction,excellent electronic mobility,good biocompatibility and ease of functionalization.Currently,the chemically reduced graphene oxide?RGO?is the one kind of graphene.Not only does RGO have the advantages of graphene,but also it easily composites with other materials and makes this nanomaterial owning other functions because it is reduced from graphene oxide?GO?.Tiranium dioxide?TiO₂?is a photocatalytic material.It has excellent photocatalytic efficiency and could degrade the organic molecules.The compound of graphene and TiO₂ could keep the advantages of graphene as well as obtain the optical performance of TiO₂.This composite was combined with the FET biosensor,and a regenerated FET biosensor by photocatalysis-inducing is built.In this work,the RGO was composited with TiO₂ and the nanocomposite was used to build the RGO@TiO₂ FET.After these processes,the FET device could be used for detecting bioactive molecules by modifying various bioactive receptors on the surface of the nanomaterials.The main contents are consisted of the following three parts:? Fabrication and characterization of photocatalysis-induced renewable FET device.Firstly,the method of chemical reduction was used to reduce the graphite oxide?GO?,and the reduced graphene oxide?RGO?was prepared.Meanwhile,the aminopropyltrimethoxysilane?APTMS?is one kind of silane reagent.When it was modified onto the TiO₂ surface,the surface of TiO₂ was positively charged because the amino-modified TiO₂ surface is positively charged,which would combine with GO?negative charge?through electrostatic interaction.Soon afterwards,the hydrazine hydrate was used to reduce the GO/TiO₂ to RGO/TiO₂.To prove that the RGO and RGO/TiO₂ nanocomposite was formed successfully,the ultraviolet absorption spectrum,transmission electron microscopy?TEM?and X-ray photoelectron spectroscopy?XPS?were used to characterize the GO,RGO and RGO/TiO₂ nanocomposite.Afterwards,the prepared RGO was drop-casted onto the electrodes to fabricate RGO FET device.Whereafter,the prepared RGO/TiO₂ was drop-casted on the surface of RGO to fabricate RGO@TiO₂ FET device.The FET device was characterized by optical microscope to observe the chip's construction.The field effect scanning electron microscope?FE-SEM?was used to observe the morphology of sensing surfaces of RGO FET and RGO@TiO₂ FET devices.In addition,the electrical characterizations of these devices were also conducted.The electrical transfer curves showed obvious bipolar and the RGO@TiO₂ FET device was p-type.? Photocatalysis-induced renewable FET biosensor for protein detection.The 1-pyrenebutanoic acid succinimidyl ester?PASE?was used as a linker molecule to immobilize anti-D-Dimer on the surface of biosensor.Afterwards,the anti-D-Dimer immobilized FET biosensor detected D-Dimer in the phosphate buffer solution?PBS?and serum respectively.The limits of detection?LOD?were 10 pg/ml in the PBS and 100 pg/ml in serum,respectively.After the completion of the detection,the biosensor was exposed under the UV-light.At last,the FET device accomplished regeneration and it could detect the same or different antigens by immobilizing the same or different antibodies.? Photocatalysis-induced renewable FET biosensor for calcium ion(Ca²⁺)detection.The Ca²⁺ probe,Fluo-4am,was modified on the surface of RGO@TiO₂FET device through ?-? stacking,after which the Fluo-4am-modified FETdevice could detect Ca²⁺ specifically and sensitively in the PBS buffer.This method would provide a new way to explore the release of Ca²⁺ in the cell,and it has a very important value for life science.