**3.2 Environmental monitoring**

For *E. coli* detection in water, a group of authors established and reported a rise in sensitivity of lateral flow assay based on T7 phage amplification. The assay was founded on phage-based reporter proteins: maltose-binding protein and alkaline phosphatase with 10-folds and 100-folds increased sensitivities, respectively. The increased sensitivity enabled *E. coli* detection of 103 CFU/mL in broth while 100 CFU/100 mL of *E. coli* in inoculated river water. Such combination of phage-based diagnosis on paper fluidics offer new platforms to establish innovative detection techniques owing to sensitivity, robustness, and specificity and are personal friendly [47]. Additional improvement in the sensitivity of this method was reported by using fluorescent quantum dots (QDs) for phage labeling. QDs increased the stability and intensity of luminous signal and also enhanced the sensitivity of epifluorescence microscopy and flow cytometry-based detection platforms. The phage head was modified with biotin tagging peptide. The QDs coated with streptavidin were permitted to become bounded to biotinylated bacteriophages. By this approach, detection limit of for *E. coli* was only 20 CFU/ mL in water with detection time of 60 min [5].

Similarly, on the basis of phage fluorescent-based detection assays, *Salmonella* in sea water was detected with the help of genetically modified bacteriophages P22 with assay time of 1 h and LOD of 10 CFU/mL [48], while TNT and TNB 1 ng/mL were detected in water with the help of phage display-selected scFv [49]. Likewise, 104 CFU/g of *B. anthracis* in soil was detected with the help of Wβ phage involving fluorescence assay [50]. A magnetoelastic biosensor involving JRB7 phage as a bio-recognition element detected 104 spores/mL of *B. anthracis* in water [51], while impedimetric biosensor based on *S. arlettae* specific phage detected 200 CFU/mL of *S. arlettae* in river water [52].
