**Two-Dimensional Layered Nanomaterial-Based Electrochemical Biosensors for Detecting Microbial Toxins**

#### **Zhuheng Li 1,2,**†**, Xiaotong Li 2,**†**, Minghong Jian 2, Girma Selale Geleta 2,3,\* and Zhenxin Wang 2,\***



† These authors contributed equally.

Received: 4 November 2019; Accepted: 27 December 2019; Published: 31 December 2019

**Abstract:** Toxin detection is an important issue in numerous fields, such as agriculture/food safety, environmental monitoring, and homeland security. During the past two decades, nanotechnology has been extensively used to develop various biosensors for achieving fast, sensitive, selective and on-site analysis of toxins. In particular, the two dimensional layered (2D) nanomaterials (such as graphene and transition metal dichalcogenides (TMDs)) and their nanocomposites have been employed as label and/or biosensing transducers to construct electrochemical biosensors for cost-effective detection of toxins with high sensitivity and specificity. This is because the 2D nanomaterials have good electrical conductivity and a large surface area with plenty of active groups for conjugating 2D nanomaterials with the antibodies and/or aptamers of the targeted toxins. Herein, we summarize recent developments in the application of 2D nanomaterial-based electrochemical biosensors for detecting toxins with a particular focus on microbial toxins including bacterial toxins, fungal toxins and algal toxins. The integration of 2D nanomaterials with some existing antibody/aptamer technologies into electrochemical biosensors has led to an unprecedented impact on improving the assaying performance of microbial toxins, and has shown grea<sup>t</sup> promise in public health and environmental protection.

**Keywords:** two dimensional layered nanomaterials; electrochemical biosensors; microbial toxin detection; antibodies; aptamers

**Key Contribution:** This review updates the construction strategies of electrochemical biosensors such as immunosensors and aptasensors for cost-effective determination of microbial toxins with high sensitivity given by rapidly developing two dimensional layered (2D) nanomaterial-based labels and substrates. We summarize the roles of 2D nanomaterials and their nanocomposites in the configuration of electrochemical biosensors, as well as the advantages they provide to the analyses, and address the major challenges and perspectives of these electrochemical biosensors for future commercialization.
