Following the regulations regarding maximum permitted presence of general E. coli or STEC in different types of food samples, a sensitive sensor for detection of E. coli and STEC should be able to detect <100 CFU/mL. However, a limitation of assessing the suitability of biosensors reported in this review is that an LOD was often expressed by authors in molar concentration due to use of synthetic DNA strands for a proof-of-concept studies. This LOD cannot be directly translated into CFU/ml due to a higher complexity of the sample if a chromosomal DNA was used. However, few authors have studied the developed biosensors with both synthetic and chromosomal DNA. This allows an approximate estimation of the required sensitivity in M concentration for the sensor to detect <100 CFU/mL in bacterial samples. For instance, Widaningrum et al. ( ) detected 5.6x10 -19 M of synthetic DNA and 17 CFU/mL using STEC culture suggesting the LOD would need to reach zM to achieve such high sensitivity. A similar or lower LOD was only demonstrated by and among the selected literature. Several authors reported LOD in aM range which may also be sufficient to detect ~100 CFU/mL. More studies are, however, needed to correlate the LOD in M and CFU/mL. In addition, the use of complex samples, such as food or faeces, was very limited and therefore it is difficult to predict how these systems may perform in POC applications. Typically, DNA extracted from bacterial cultures was only used for validation. The future development of POC nucleic acid based electrochemical sensors should focus on simple ways to prepare the sample or/and incorporate this step into a fully integrated device. As such, development of an easy way for DNA extraction is highly critical key achievement for success. Recycling of the nucleic acid-based biosensors is another crucial factor which clearly may have an impact on their introduction to the market. That means reusing the nucleic acid-based biosensor after dehybridising the target strand and allowing for several uses of a single sensor. Typically, a strong base such as NaOH is used to break the hydrogen bonds in the double-strand DNA.