Stimuli-responsive polymers for interface engineering toward enhanced electrochemical analysis of neurochemicals

Neurochemical monitoring can provide important insights into the chemical communications in the brain and neurological diseases. Although electrochemical sensors have promoted the development of neurochemical analysis, the limited analytical performance of the existing sensors restrict our understanding of the roles that chemical signals play in the brain. The central nervous system is composed of a large number of neurochemical species. Meanwhile, it is difficult to monitor neurochemicals with high sensitivity because of the kinetic barrier of mass transport and electron/ion transfer. More importantly, to fabricate a "smart" electrochemical sensor for neurochemicals, the engineering of an electrode surface with switchable properties and a response is urgently needed. This review focuses on the construction and application of electrochemical sensors based on stimuli-responsive polymers. The response of polymers to external stimuli can not only enhance the target recognition, but also modulate the electrochemical signals, thus providing smart electrochemical sensing platform with improved analytical performance, including high selectivity, sensitivity, and controllability. In this review, we first introduce the design strategy of bio-responsive stimuli-responsive polymers and highlight the relationship between their structure and molecular recognition efficiency. Then, we summarize the electrochemical techniques with different sensing principles and emphasize the contribution that stimuli-responsive polymers made to the conversion of chemical/electrochemical reactions into electric signals. Finally, the opportunities and limitations of stimuli-responsive polymer-modified electrochemical sensors for neurochemical analysis will be discussed. Taking advantage of the development of novel materials, electrochemical techniques and microelectronic engineering, the advanced devices (e.g., antifouling, flexible, miniaturized, and multi-functional) with remarkable analytical performance will benefit the evaluation of neurochemicals, which can promote a deep understanding of brain events and the diagnosis and treatment of neurological diseases.