Know4Nano

Bacterial flagellin, a key protein in the locomotor system of the organism, is a protein that can self-assemble and polymerize in vitro. Distinct parts of flagellin are responsible for its polymerization ability, and the D3 domain, the surface part of the long filaments it forms, can be genetically engineered to be versatile without compromising its self-assembling ability. By modifying or substituting the D3 domain, variants with binding, enzymatic activity or signaling properties can be developed. These can be used to build multifunctional mixed or block polymers under in vitro conditions, with up to tens of thousands of sensing units on their surface, resulting in excellent signal amplification in biosensing. In addition, flagellin variants can be incorporated into the filaments to provide both anchoring to the sensor surface and stabilization of the filaments by cross-linking. This strategy makes biosensors functionalized with sensing flagellar filaments superior to other protein (e.g. antibody)-based biosensors. Furthermore, as the D3 domain has a stable structure on its own, it is a suitable scaffold protein for directed evolutionary processes that can respond efficiently and rapidly to sensor development for the detection of emerging contaminants.