Polydopamine/Graphene/MnO₂ Composite-Based Electrochemical Biological Sensor

In vivo detection of active small molecules in plant tissues is one of the key technologies for the development of precision agriculture.In this paper,tryptophan（Trp）is used as the detection object to develop an enzyme-free electrochemical sensor suitable for in situ detection of active small molecules in plant tissues.To this end,this paper studies a polydopamine（PDA）/reduced graphene oxide（RGO）-MnO₂nanocomposite material that is selective to Trp,and discusses its in-situ electroporation on a glassy carbon electrode（GCE）.In the deposition process,a PDA/RGO-MnO₂ modified sensing electrode with pore structure was developed.Under the synergistic effect of the selectivity of PDA and the catalytic activity of RGO-MnO₂,PDA/RGO-MnO₂/GCE has a high electrocatalytic response to Trp.In addition,in order to cope with the variability of the p H value of plant tissues,a reliable Trp detection scheme was proposed to select a quantitative detection model based on the p H value of plant tissues.To this end,based on PDA/RGO-MnO₂/GCE,a series of linear regression models were constructed in the p H range of 4.0～7.0.In this p H range,the linear detection range of Trp is 1～300μM,the sensitivity is 0.39～1.66μAμM^-1,and the detection limit is 0.22～0.39μM.In addition,the quantitative determination of Trp content in tomato fruits and juices proved the practicality of the PDA/RGO-MnO₂/GCE sensor.The sensor provides reliable Trp levels in both in vitro and in vivo detection methods,which also proves that this article proposes a new strategy suitable for the development of plant electrochemical sensors.