*2.1.1 Phage-SPR-based sensors*

Surface plasmon resonance (SPR) works on the principle of oscillation phenomenon that happens between the interfaces of any two materials. The change in the refractive index close to the sensor surface caused by contact of target analyte in the medium with the bio-probe (phage) present on transducer surface is measured by SPR biosensors. Phages have been widely immobilized as bio-probes on the surfaces of SPR transducers to offer facility of specific recognition of bacterial detection. The immobilized phage on SPR transducer successfully detected *E. coli* K12 [15], *S. aureus* [16], methicillin-resistant *Staphylococcus aureus* (MRSA), and *E. coli* O157:H7 [17]. Typically, the LOD was ranging from 102 to 103 CFU/mL. Phage RBPs have been utilized as bio-probes in SPR approaches for specific bacterial screening, such as Singh et al.'s activated gold-coated plates, by immobilizing genetically engineered tailspike proteins from P22 phage to demonstrate selective, specific, and real-time *Salmonella* detection with 103 CFU/mL sensitivity [18].

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*Applications of Phage-Based Biosensors in the Diagnosis of Infectious Diseases, Food Safety…*

For bacterial quantitative detection in samples, bioluminescence analyses that are rapid, sensitive, and simple are used by assessing the emitted light from intracellular components. Bacterial lysis is the first step of this type assays, to discharge intracellular cell components followed by reaction with luciferase and are screened by bioluminescent. A lytic bacteriophage is involved as a bio-recognition probe for target bacterial detection following lysis. Infectious bacteria like *E. coli* and *Salmonella Newport* were detected by an adenosine triphosphate bioluminescence assay using lytic bacteriophage as bio-probe lysis of target bacterial cell [19]. The sensitivity was enhanced 10–100-folds by addition of adenylate kinase as an alter-

*A graphical representation of target pathogen detections based on reporter phage, adapted from [14].*

Later it was demonstrated that the quantity of discharged adenylate kinase from lysed cells is dependent on the growth stage, bacterial type, the infection time, and

An innovative Raman method, i.e., surface-enhanced Raman spectroscopy (SERS), is enhancing the intensity by vibrational absorbance of definite elements when they are near the surface of nano-organized noble metals by the influence of numerous orders of magnitude. The improved intensity of SERS method is dependent on the molecules' capability to release a Raman signal and the contained fields of plasmon in their neighborhood [21]. For instance, a report stated a phage-SERS biosensor for *E. coli* detection using phage immobilization on nano-figured thin sheet of silver over substrates of silica (**Figure 2**) [22] established by exploitation of metallic nanosculptured thin silver film. The silver film exterior is activated by self-assembled monolayer of 4-aminothiophenol and glutaraldehyde for T4 immobilization to screen *E. coli*. As a reporter molecule, 4-aminothiophenol monitored the Raman band enhancement. Other reports of phage-SERS-based biosensors have

CFU/mL of *E. coli* was reported in ˂1 h [19].

*DOI: http://dx.doi.org/10.5772/intechopen.88644*

*2.1.2 Phage-bioluminescence sensors*

**Figure 1.**

nate cell marker, while less than 104

*2.1.3 Phage-SERS-based sensors*

been reported and are briefed in **Table 1**.

the phage type [20].

*Applications of Phage-Based Biosensors in the Diagnosis of Infectious Diseases, Food Safety… DOI: http://dx.doi.org/10.5772/intechopen.88644*

**Figure 1.**

*Biosensors for Environmental Monitoring*

detection in clinical, food, and environmental samples.

**2.1 Phage optical biosensors**

*2.1.1 Phage-SPR-based sensors*

*Salmonella* detection with 103

[17]. Typically, the LOD was ranging from 102

**2. Phage-based biosensors for infectious pathogen detection**

for detection of pathogenic bacteria, which are briefed as follows:

Bacteriophage as a bio-probe has been used in different transduction platforms

Optical phage-based sensors owing from their reasonably rapid screening, sensitivity, and flexibility to a broad-ranging assay situations have been extensively explored for bacterial detection. Optical methods are classified into two core subclasses on the basis of their working principles, label-free and labeled. The best frequently used optical methods for bacterial screening are fluorescence spectrometry [8], surface plasmon resonance (SPR) [10], and bio- or chemiluminescence [13]. In the subsequent subsection, our focus is on phage bio-probe-based optical biosensors for detection of pathogens with special emphasis on food safety and environmental monitoring. **Figure 1** represents a reporter phage-based optical sensing scheme.

Surface plasmon resonance (SPR) works on the principle of oscillation phenomenon that happens between the interfaces of any two materials. The change in the refractive index close to the sensor surface caused by contact of target analyte in the medium with the bio-probe (phage) present on transducer surface is measured by SPR biosensors. Phages have been widely immobilized as bio-probes on the surfaces of SPR transducers to offer facility of specific recognition of bacterial detection. The immobilized phage on SPR transducer successfully detected *E. coli* K12 [15], *S. aureus* [16], methicillin-resistant *Staphylococcus aureus* (MRSA), and *E. coli* O157:H7

been utilized as bio-probes in SPR approaches for specific bacterial screening, such as Singh et al.'s activated gold-coated plates, by immobilizing genetically engineered tailspike proteins from P22 phage to demonstrate selective, specific, and real-time

CFU/mL sensitivity [18].

to 103

CFU/mL. Phage RBPs have

withstanding harsh environmental conditions. Establishing phage-based biosensors for application in food safety and environmental monitoring is a motivating and interesting research topic and is the urgent need of this modern era. The key point is to enhance phage-based cheap recognition tools with maximum levels of selectivity, consistency, and sensitivity with minimum times of assay. Significant struggles have been dedicated on enhancing the transducer surface of biosensor for improved detection and sensitivity. Phage-based bio-probes have been used in transducer development for several analytical approaches to offer specific and selective detection. Bacteriophages as a bioprobe have been successfully applied for bacterial detection in clinical samples (urine) [3], food samples (milk, tomatoes) [4], and environmental samples (river water) [5]. Furthermore, different analytical approaches relying on phage-based bio-probes have been reported like electrochemical [6], bioluminescence [7], fluorescence [8], mass spectrometry [9], magnetoelastic [4], surface plasmon resonance [10], lateral flow assay [11], etc. In the following context, we will review biosensor transduction platforms involving phage-based probes for transducer development to detect infectious bacteria in the field of food and environmental safety monitoring [12]. In this chapter we will highlight applications of different phage-based analytical approaches for bacterial

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*A graphical representation of target pathogen detections based on reporter phage, adapted from [14].*
