Table 1.

Advantages and disadvantages of tuning strategies for biosensors.

Tuning Strategy	Advantages	Disadvantages	References
Promoter engineering	Several approaches, including changing the number or location of TF operator sites and introducing point mutations to the TF operator sites or the −35 and −10 binding sites; useful for fine-tuning sensitivity, detection range, dynamic range, cooperativity, or signal output intensity	Cannot be used to adjust sensor specificity for target metabolites	[36,37,38,39,40,41]
TF engineering	Can tune binding with target metabolite or DNA; useful for fine-tuning specificity, sensitivity, and dynamic range	Requires knowledge of TF structure and binding mechanism; TF expression level changes with cell growth conditions; mutations specific to one TF (e.g., specific base substitutions in one TF ligand-binding domain) may not be readily applicable to other TFs	[36,40,41,42,43,44,45,46,47,48]
RBS engineering	Can be used to control the rate of TF or reporter protein production; can be combined with transcriptional control for multi-layered control strategies; useful for fine-tuning the dynamic range	Cannot be used to adjust sensor specificity for target metabolites	[49,50,51,52,53]