**3.1 Antibodies**

To accomplish the requisite for up-to-date and fast bio-sensing schemes, antibodies (Abs) have become important affinity ligands to detect pathogens in clinical and food samples. Definitely, Abs when immobilized on a surface, these interact with specific antigens present on microbial surfaces, thus inducing a computable signal by an output detector. Abs popularity ascends from numerous benefits, for example, adaptability, ease of incorporation into diverse systems and are highly specific to their target antigens [21].

**161**

*Principle and Development of Phage-Based Biosensors DOI: http://dx.doi.org/10.5772/intechopen.86419*

From the time of first biosensor (glucose sensor by Clark and Lyons in 1962), enzyme-based biosensors have shown immense progress in many applications. Enzymes are precise competent bioanalytical agents, having the ability to precisely mark out their substrates. This distinctive property mark enzymes potent implements in the development of analytical devices [18]. These biosensors company closely a biocatalyst-comprising a detecting coating with a transducer. Its operational principal is based on the catalysis and binding abilities for specific

The sequence of nucleic acids for a precise detection was established in 1953 and is still developing widely [20]. These biosensors involve nucleic acids as a bio-recognition-prob. The high specific binding between the two single strands of DNA (ssDNA) sequences to make double stranded DNA (dsDNA) sequence is used to develop nucleic acids-based biosensor. This technique validated to develop DNA-built-biosensor from the old-style technique like pairing of radio iso-tropic and electrophoretic separations that are costly, dangerous, and time

These biosensors involve living cells as a bio-probe and detecting component. They are constructed on the basis of living cell ability to sense the physiological parameters, and the extracellular and intracellular micro-environmental conditions, and as a result a response is produced by the reaction between cell and stimulus [19]. Microbial cells, for example fungi and bacteria are commonly used to develop whole cell based biosensors to sense particular molecules or the inclusive

Phages are virus particles, infecting and reproducing only within bacterial cells. Because of their associated evolution along with bacteria, phages have extremely specific machineries to identify and then infect their host bacteria for propagation. Phages generally have two distinctive chunks, the head comprising genetic material while the tail accountable to recognize and attach to bacterial cell [22]. Phages have several biomedical applications, and owing to their specificity they are extensively used for specific and sensitive detection of bacteria [23]. Most significant feature of phages is that they can only identify, and attack living bacterial cells. This exciting feature was well demonstrated by Fernandes et al., to detect viable, viable but not culture-able, or totally dead *Salmonella* cells on a biochip that was bio-functionalized with either phage or antibody as a bio-recognition element [24]. Interestingly dead cells were still capable to interact with the antibody, phage probes enabled a superior difference among viable and dead *Salmonella*. Additionally, some of phages are very specific and infecting only one bacterial specie [25]. This property will permit the recognition of target pathogenic bacterial species in a complex flora. Comprehensive explanation of bacteriophage based recognition elements employed

as bio-probes in development of a biosensor to detect pathogenic bacteria, is

**3.2 Enzymes**

detection.

consuming.

**3.4 Cells**

**3.3 DNA/nucleic acid**

"condition" of the nearby environs.

outlined in the following section.

**3.5 Bacteriophages**
