A novel approach for improving the sensitivity of nucleic acid-based sensor was proposed by who immobilized a 3D probe DNA nanostructure onto a gold electrode via thiols, see Figure . (A). The nanostructure comprised of four DNA strands specifically designed to form a 3D structure to avoid surface steric hindrance effect without its overcrowding. The detection was undertaken using amperometry and enzymatically labelled reporter. The developed sensor demonstrated an LOD of 10 -15 M with the synthetic DNA and it was applied to detect PCR amplicons of E. coli genomic DNA to assess its selectivity. An alternative probe DNA attachment approach was used by Li et al 2018 who used poly-adenine (poly-A) blocks instead of thiols. This immobilisation method has been previously reported by other authors offering advantages to the thiolated DNA such as lower cost, faster immobilisation and easier way to control probe density by testing different length of poly-A blocks . A different length of poly-adenine blocks was tested with 30 adenine blocks chosen as most optimal. The enzymatic detection using HRP tagged reporter probe achieved an LOD of 5x10 -15 M. The assay was performed in less than 3 hours, including the PCR amplification. modified the gold electrode with mesoporous silica thin films that offer larger surface area and hydroxyl groups content for biomolecules attachment. The heptylamine-phosphoramidite moiet modified probe, complementary to 16s rRNA sequence of E. coli was immobilised on top of the modified electrode and the detection was done using CV in 5 mM Fe -3-/Fe 4-. This method achieved an LOD of 2.5 x 10 -14 M and tests were done with RNA extracted from the E. coli bacterial culture in around one hour, including the RNA extraction.