Stuides On The Preparation Of Modified Screen-Printed Electrodes And The Applications In Detection Of Cellular Viability And Heavy Metal

The screen-printed carbon paste electrodes prepared by the screen-printed technology have some advantages including fast fabricating,mass producing and low costs and etc.,they have wide applications in the field of electrochemical sensing.However,the performances of the screen-printed electrodes using graphite powder carbon paste(CP)are difficult to meet the requirement of high sensitivity for the electrochemical sensing.It is necessary to modify the screen-printed CP electrodes to improve the electrochemical property.In this paper,the modified screen-printed CP electrodes are prepared by using nanomaterials and conductive polymer,and are used as the gate electrodes of the organic electrochemistry transistors(OECTs)and the working electrodes of the traditional three-electrodes system.The effect of nanomaterials on the cellular viability is investigated by OECTs,and the heavy metal ions(lead and cadmium)are detected by stripping voltammetry using the modified CP electrodes.The main works are as follows:1.The CP electrodes were prepared on PET substrate by using the Electrodag 581ss graphite powder carbon paste,and these electrodes were used as the source,drain and gate electrodes of OECTs.The OECT devices were prepared using poly 3,4-ethylenedioxythiophene:polystyrene sulfonic acid(PEDOT:PSS)as the organic polymer semiconductor materials.The Pt NPs/MWCNTs/CP modified electrodes were prepared by drop-coating of the MWCNTs aqueous suspension,followed by electro-deposition of Pt NPs on the CP electrode surface.The responses characteristics of OECTs in cell culture medium(RPMI 1640)were studied in detail.The results show that the modification of the CP electrodes with MWCNTs and Pt NPs greatly improved the electrochemical performance of the resulting electrodes(the electron transfer resistance was about 380 Ω).The OECT devices using the Pt NPs/MWCNTs/CP gate electrodes have sensitive adjusting properties in PBS and RPMI 1640.Moreover,the devices show good stability during measurements.The drain and source current-time(IDS-t)of the OECT devices was measured and the results demonstrate that the electro-active substances in RPMI 1640 can lead to the change of IDS.However,when RPMI 1640 was used as the blank electrolyte,this interference can be deducted as the background current.2.The OECTs were combined with Transwell.The HeLa cells in the Transwell were induced by fMLP peptide to produce H2O2,which can be detected by OECTs.By this way,the cellular viability can be evaluated by OECTs.The cell culture time and cell number were optimized.The proposed method was used to evaluate the effect of Au NPs and graphene on the viability of HeLa cells,and the results were compared with those obtained by WST-8 assays.The results suggest that the OECTs using the Pt NPs/MWCNTs/CP gate electrodes have sensitive responses to addition of H2O2.Under optimal conditions,the absolute value of the IDS of the OECT devices decreased after the HeLa cells were incubated with Au NPs or graphene at given concentration,which indicates that the cellular viability decreased.The results were consistent with those obtained by WST-8 assays,suggesting that the OECTs integrated with Transwell can be used to evaluate the effect of nanomaterials on cellular viability.3.The CP electrode was modified by the MWCNTs and PEDOT:PSS.The doping amounts of MWCNTs was optimized.The electrochemical properties of the modified electrode were characterized by cyclic voltammetry(CV).The MWCNTs-PEDOT:PSS/CP electrode was used to detect the lead and cadmium heavy metal ions by stripping voltammetry.The detection conditions such as pH value、parameters of differential pulse voltammetry and so on were optimized.The results show that under the optimal conditions,the potential difference of the redox peaks of the[Fe(CN)6]3-/4-probes at the modified electrode was about 160 mV.The modified electrode has good stability during CV measurements.The linear range for lead ion detection was 0.1 μg L-1～80μg L-1(R2 = 0.9991).The lower detection limit was 0.043 μg L-1,and the sensitivity was 0.06917 μA μg-1 L.The linear range for cadmium ion detection was 2 μL-1～50 μg L-1(R2 = 0.9902).The lower detection limit was 0.44 μg L-1,and the sensitivity was 0.04061 μA μg-1 L.