Study On The Sensing Of Tumor Cells Based On The Organic Electrochemical Transistors

Organic electrochemical transistor(OECTs) is a kind of organic thin film transistor, which have been developed in recent thirty years. Since reported by Wrighton et al. in 1984 for the first time, the studies on OECTs and their applications have received extensive attentions, especially in biological sensing field, such as glucose sensor, urea sensor, DNA sensor, and etc. In this work, OECT devices were prepared using poly 3,4-ethylenedioxythiophene: polystyrene sulfonic acid(PEDOT: PSS) as organic polymer semiconductor, and screen printed carbon paste(CP) electrodes as source and drain electrodes. Moreover, the study on tumor cell sensing based on OECTs using the glassy carbon(GC) electrode, screen-printed CP electrode, or their modified electrode as the gate electrodes of OECTs was carried out. The main works are as follows:1. The boric acid group was modified on the surface of gate electrode(GC electrode) by electro-polymerizing of 3-aminophenylboric acid. Under the suitable p H value, the interaction between the boric acid group and vicinal hydroxyl groups of sialic acid(SA) is specific, and it can change the potential drop at the interface of gate electrode and electrolyte solution, which can lead to an adjustment of channel currents(IDS) of OECTs and hence, SA could be detected based the proposed principle. By the same way, this method can be used to identify the tumor cells(He La cells as a model), on which the SA was overexpressed. The linear range to free SA detection was 0.1 m M ~ 2 m M(R2 = 0.9927) and the detection limit was 8 μM; the linear range for He La cell detection was 5 × 104 ~ 5 × 105 cells m L-1(R2 = 0.9951).2. N-Formyl-Met-Leu-Phe(f MLP) is a kind of potent neutrophil peptide, which can induce macrophages metabolizing, accelerating the respiratory rate, and producing hydrogen peroxide. Considering the large specific surface area of multi walled carbon nanotubes(MWCNTs) and the effective catalysis of platinum nanoparticles(Pt NPs) to electrooxidation of hydrogen peroxide, Pt NPs/MWCNTs/GC electrodes were prepared and used as the gate electrodes of OECTs. Hydrogen peroxide produced by the cell-f MLP(MCF7 cells as a model) interactions was electrooxidized at the gate electrode surface, and produced a faraday current. The faraday current can change the potential drop at the interface of gate electrode and the electrolyte solution, leading to a current response(|ΔIDS|). There is a linear relationship between the normalized current response(NCR = |ΔIDS/I0|) of OECTs and logarithm of concentration of hydrogen peroxide: the linear range was 0.2 μM ~ 0.1 m M(R2 = 0.9955), and the detection limit was 0.1 μM. The NCR to MCF7 cell, and HUVEC cell(the concentration were 1 × 104 cells m L-1) was 0.075 and 0.032.3. The OECTs using GC electrode, gold electrode, platinum electrode, and other disk electrodes as the gate electrode have a larger space and do not conducive for the practical applications. Therefore, the CP gate electrodes were prepared by screen-printing technique, which effectively reduce the structure space of OECTs, and make it more suitable for practical applications. The results show that the output performances and transfer performances of the bare CP gate electrode can not meet the requirements of the application. Therefore, MWCNTs and Pt NPs were modified on the surface of the bare CP electrodes. It was found that the output performances and transfer performances of the modified CP gate electrodes have been greatly improved, and the modified CP electrodes can be used to sensitively detect hydrogen peroxide and cancer cells. The results as follows: the linear range for hydrogen peroxide determination was 0.5 μM ~ 0.1 m M(R2 = 0.9757) and the detection limit was 0.2 μM; The NCR to 1 × 104 cells m L-1 MCF-7 cells was 0.030.