Application Of Organic Electrochemical Transistors In Enzyme Biosensors

Organic electrochemical transistors(OECTs)have attracted widespread attention for chemical and biological sensing applications due to their low cost,easy fabrication,low working voltage(<1 V),good electrochemical activity,flexible,excellent environmental stability and good biocompatibility.Owing to their advantages of high detection sensitivity and low detection limit,the OECT-based enzymatic biosensors have very good application prospect in the prevention and diagnosis of some diseases.In this thesis,we mainly focus on the enzymatic biosensors based on organic electrochemical transistors.The preparation and characterization of OECT devices were optimized.OECT-based sarcosine sensor was studied for highly sensitive detection of sarcosine.Moreover,OECT-based noninvasive salivary glucose test strips and glucose meters were also studied for practical applications.First of all,the fabrication process of the OECT device was optimized.The result shows that the device can work stably in PBS solution.The channel current of the device can be modulated by more than 1 order of magnitude(VGS<1 V),which is beneficial to its application in enzyme biosensor.When VGS is more than or equal to 0.7 V,IDS will be faster to achieve a relatively balanced state,about 20 s,indicating that the device can quickly reach to a steady state.In order to improve the detection performance of OECT-based sarcosine sensors,carbon nanotubes,platinum nanoparticles,and anodic porous alumina(AAO)were used to modify the gate electrodes.The result shows that the detection limits of the devices are 50 nM,5 nM,and 50 nM,respectively,which are 1-3 orders of magnitude lower than that of non-modified device.As the specific surface area of the gate electrode can be increased by the modification of nanomaterials,the effective amount of sarcosine oxidase on the gate electrode will also be increased.Meanwhile,carbon nanotubes and platinum nanoparticles have good electrocatalytic ability,so the detection performance of the OECT-based sarcosine sensor has been effectively improved.As the detection limit of OECT-based sarcosine sensor(5 nM)is lower than the sarcosine concentration of normal people and prostate cancer patients in urine,it can meet the practical application requirements.Finally,OECT-based noninvasive salivary glucose test strips and glucose meters were also studied for practical applications.The test strip with platinum electrode has the best detection performance as platinum has very good electrocatalytic ability and good conductivity.At the same time,the glucose meter is compatible with OECT-based noninvasive salivary glucose test stripe.A certain linear relationship between the numerical reading of the glucose meter and the blood glucose concentration of diabetics was gotten.It can be indicated that the morning fasting state is the ideal condition for saliva sampling.The preliminary result shows that OECT-based noninvasive salivary glucose test strips can be used for the detection of salivary glucose.