Highly Sensitive Electrochemical Biosensor Based On Organic Electrochemical Transistor

Enzymatic electrochemical biosensor,as the earliest developed reliable method to detect bioactive molecules,has mature electrode modification and preparation methods,and electrochemical testing methods.At the same time,the specific recognition of enzyme enhances the sensitivity of electrode and the selection of specific molecules,which makes it have extensive value on practical applications in the field of biosensor.Organic electrochemical transistor(OECT),as a new type of biosensor,combines its high signal amplification ability from enzymatic electrochemical biosensor,so as to realize high selectivity and high sensitivity of the sensor,and becomes a new type of sensor that may replace the traditional electrochemical sensor and realize multifunctional application.However,when the enzymatic electrochemical biosensor based on the OECT is applied to the solution to be tested containing a variety of biological molecules,the ability to recognize specific molecules is reduced and the selectivity is reduced.In order to realize the high selectivity and high sensitivity detection of the enzyme sensor based on OECT,and to apply it to the study of detecting the biomolecules in the rat cerebral dialysis fluid,the modification of enzyme and the modification of semiconductor film need to be started.In this paper,the modified electrode method was mainly studied to obtain a sensor that can be detected for a long time and has high sensitivity and selectivity.We applied it to the specific detection of glucose and glutamate in rat cerebral dialysis fluid.The specific results can be summarized as follows:(1)Firstly,the organic electrochemical transistor sensor based on glucose oxidase and glutamate oxidase with ferrocene as the interface molecule as the gate electrode,and PEDOT: PSS as the channel semiconductor material of the OECT.The catalytic activity and selectivity of the sensor to substrate(glucose or glutamate)in complex systems were studied.It is found that under the condition of constant gate electrode selectivity,it is the covered semiconductor film between the source electrode and the drain electrode that determines the selectivity of the whole organic electrochemical transistor.(2)In order to achieve the selective detection of complex samples(such as a mouse dialysate)(such as glucose)and avoid the object under test with the influence of electroactive molecules,we chose to use respectively with polymer molecular selfassembly of positive and negative charges in the electrodes and the semiconductor film surface,find the adaptation ratio and concentration,guarantee the high sensitive electrode at the same time,realized the high selectivity in the complex samples.When the experiment in the beaker was sufficiently repeatable,the prepared electrode was used to measure the glucose concentration in the cerebral dialysis fluid of normal rats,and the concentration was at the range of 450~500 ?M,which was consistent with the range provided in the literature.It is proved that the sensor can be used to detect the concentration of the substance to be tested in complex samples(3)Based on the modified high selectivity enzymatic electrochemical biosensor system and the recently reported ferredoxin-dependent glutamate synthase(Fd-GltS)modified gate electrode,we first studied the application of Fd-GltS to the catalytic oxidation of glutamate by ferrocene in the second-generation biosensor and proved its feasibility.Moreover,the glutamate sensor has the advantages of oxygen independence and enzyme catalytic activity higher than glutamate oxidase during detection,so we modified it on the gate electrode of the organic electrochemical sensor to realize the detection of glutamate with high selectivity and high sensitivity,and it is expected to be applied to in vivo online detection.