**2. OB classification**

There are a broad range of OB classification. Generally, the classification can be divided into two main classes: label-free and label-dependent classes.

**19**

*Optoelectronics and Optical Bio-Sensors DOI: http://dx.doi.org/10.5772/intechopen.96183*

application in detection technologies [15].

**4. OB working method**

**Figure 3** [36].

**5. Types of OB**

**5.1 Evanescent wave fluorescence**

between virus-protein and whole cell [37].

as follow:

**3. OB detector elements – Bio-recognisers**

some of their applications and features in biosensing.

In label-free class the measured signal is produced directly by the interaction between transducer and the bio-analyte. Whereas in label-based sensors, a label is needed to produce signal, which can be measured later by a colorimetric, luminescent or fluorescent method as can be illustrated in **Figure 2** [14].

Label-free mode is more economically efficient in comparison to label dependent mode. It requires less effort and expertise and eliminate the experimental errors such that resultant from label shelf life, signal noise background. These are commonly seen in antibody–antigen interaction using label, which has a wide

Different bio-recognisers are used in the OB detection and quantifying technologies. The diversity of the detected materials required a suitable recognizing element. Examples of analytes in the samples; genetic material, toxins, drugs, enzymes, heavy metals [16–19]. Enzymes, nucleic acids, antibodies, cells and micro-organisms are commonly used as bio-recognisers [20–24]. **Table 1** shows

An optical measurement concept is used by optical biosensors devices. Fiber optics are used along with optoelectronic transducers in these devices. The opt rode term is composed of optical and electrode terms. Enzymes and antibodies such as transducing elements are examples of what types of elements involved in these sensors. A secure non-electrical is permitted in optical biosensors, in which a sensing of equipment is inaccessible [34]. An additional advantage is that devices do not require reference sensors [35]. The reason behind that is that a light source can generate a comparative signal, which is similar to that of the sampling sensor. In order to ecxite the sensing element, optical source such as LED or Laser should be focused into substrate and photodetector capture the output signal as shown in

Biosensors in general divided into categories which are Bioreceptor and Transducer. While, Optical biosensors are divided into two groups, which are: direct optical biosensor detection and labeled optical biosensor detection

Evanescent wave-based biosensors are used to investigate the exponential growth in life science applications. They include the dissociation and binding kinetics of receptor-ligand pairs and antibodies, epitope mapping, interactions between protein-DNA and DNA–DNA, phage, show libraries, and interactions

Waveguide interferometers have remarkable significance, because they merge both sensitive techniques that are: wave guiding and interferometry techniques. Hence, they provide great reliability and potential miniaturization and integration

**Figure 2.** *Illustration graph showing label and label free recognition classes of OB.*

*Optoelectronics and Optical Bio-Sensors DOI: http://dx.doi.org/10.5772/intechopen.96183*

*Optoelectronics*

**2. OB classification**

*Schematic diagram illustrate biosensor structure [7].*

**Figure 1.**

North America in the 2020 [13]. There is no universal or standard OB for detection; however, there are groups of OBs developed for specific applications and targets.

There are a broad range of OB classification. Generally, the classification can be divided into two main classes: label-free and label-dependent classes.

**18**

**Figure 2.**

*Illustration graph showing label and label free recognition classes of OB.*

In label-free class the measured signal is produced directly by the interaction between transducer and the bio-analyte. Whereas in label-based sensors, a label is needed to produce signal, which can be measured later by a colorimetric, luminescent or fluorescent method as can be illustrated in **Figure 2** [14].

Label-free mode is more economically efficient in comparison to label dependent mode. It requires less effort and expertise and eliminate the experimental errors such that resultant from label shelf life, signal noise background. These are commonly seen in antibody–antigen interaction using label, which has a wide application in detection technologies [15].

### **3. OB detector elements – Bio-recognisers**

Different bio-recognisers are used in the OB detection and quantifying technologies. The diversity of the detected materials required a suitable recognizing element. Examples of analytes in the samples; genetic material, toxins, drugs, enzymes, heavy metals [16–19]. Enzymes, nucleic acids, antibodies, cells and micro-organisms are commonly used as bio-recognisers [20–24]. **Table 1** shows some of their applications and features in biosensing.

## **4. OB working method**

An optical measurement concept is used by optical biosensors devices. Fiber optics are used along with optoelectronic transducers in these devices. The opt rode term is composed of optical and electrode terms. Enzymes and antibodies such as transducing elements are examples of what types of elements involved in these sensors. A secure non-electrical is permitted in optical biosensors, in which a sensing of equipment is inaccessible [34]. An additional advantage is that devices do not require reference sensors [35]. The reason behind that is that a light source can generate a comparative signal, which is similar to that of the sampling sensor. In order to ecxite the sensing element, optical source such as LED or Laser should be focused into substrate and photodetector capture the output signal as shown in **Figure 3** [36].

#### **5. Types of OB**

Biosensors in general divided into categories which are Bioreceptor and Transducer. While, Optical biosensors are divided into two groups, which are: direct optical biosensor detection and labeled optical biosensor detection as follow:

#### **5.1 Evanescent wave fluorescence**

Evanescent wave-based biosensors are used to investigate the exponential growth in life science applications. They include the dissociation and binding kinetics of receptor-ligand pairs and antibodies, epitope mapping, interactions between protein-DNA and DNA–DNA, phage, show libraries, and interactions between virus-protein and whole cell [37].

Waveguide interferometers have remarkable significance, because they merge both sensitive techniques that are: wave guiding and interferometry techniques. Hence, they provide great reliability and potential miniaturization and integration


*Optoelectronics*

**Table 1.**

**21**

*Optoelectronics and Optical Bio-Sensors DOI: http://dx.doi.org/10.5772/intechopen.96183*

are stimulated as seen in **Figure 4** [37–40].

*Schematic for optical biosensor working method [36].*

**5.2 Optical fibers**

**Figure 3.**

two different types:

polarization [42].

extrinsic optical biosensor) [44].

in optical chips. Through the utilization of evanescent wave technology, the interaction between biomolecules and receptors are measure by the waveguide interferometer in real time without using labels. On a sensor surface, receptors are frozen and the interaction with the close biomolecules leads to a variation in the refractive index. With being far from the surface, the evanescent wave decays exponentially, usually over the distance of 100 nm to approximately a wavelength. Due to the reason that the evanescent wave is a near-surface phenomena, therefore, by using the detection of evanescent wave stimulation to produce fluorescent signal is surface-sensitive. This means that solely fluorescent molecules close to the surface

Fiber optic is an example of analytical devices that works as a transduction item, in which it generates a signal proportional to the density of chemical or biochemical elements with react of the biological element. In addition, they transfer light with silica glass or plastic fiber optic fiber based on the Total Internal Reflection (TIR) principle to the analysis site [41]. The fiber optics biosensors are categorized into

• Intrinsic sensors: the environmental changes are transformed by the internal property of the optical fiber itself into light signal modulation. This light signal modulation may be in the form of phase, intensity, and frequency or it may be

• Extrinsic sensors: on the other hand, the extrinsic sensors can use the fiber as carriers of information leading to a black box. In addition, these sensors produce a light signal based on the received information at black box. This black box can be made of gas, mirrors liquid cells or several other optical signal generation mechanisms (**Figure 5**) show the difference between Intrinsic and

The fiber-optical sensors essential benefits can vary from their: 1) capability of hard environment to robust EMI (electromagnetic interference immunity),

*Different bio-recognition, their applications and features.*

#### **Figure 3.**

*Optoelectronics*

**20**

**Biorecognition**

Enzyme

**(Bio)sensors** Multilayers of silver metal and tantalum oxide nanoflakes with

acetylcholinesterase enzyme OB [25]

Tyrosinase on Fe3o4@Au core shell nanoparticles bio-probe [26]

Carbon nanofiber gold nanoparticles tyrosinase [27]

DNA - AuNTs-PC electrode

Disposable electrodes were fabricated by thermal evaporation on

polyethylene terephthalatesubstrates covered with a nanometric

gold layer manufactured in three-contact configurations

Antibody against Aflatoxin immunosensor [30, 31]

Graphene oxide (GO) composite and staphylococcal protein A

[32]

Bioelectric Recognition Assay [33]

Aflatoxin detection

ND

100 pg./mL

in food

Human IgG

40–120 um/ml

10 ng/mL

102 CFU/mL

detection

*L. monocytogenes*

ND

detection

Antibodies and

Immuonsensor

Cell/Microbial


*NM = not determined.*

**Table 1.**

*Different bio-recognition, their applications and features.*

Nucleic acids

Detection of ferulic

acid in cosmetics

Human papilloma

0.01pM to 1 μM.

1 fM

visus 16 & 18 [28]

Zika virus [29]

25nM and 340nM

25 nM

Detection of

Linear response in the concentration range

5.0–75.0 μM, 10.0–100.0 μM for phenol

and dopamine and 50.0–500.0 M for

catechol

ND

2.89 × 10−9 mol/L

dopamine, phenol

and catechol

**Selected application**

Alzahimer's disease

diagnosis

**Physical transducer/liner range**

50–400 uM

**Detection limit**

8.709 nm/μM and a

remarkable LOD value of

38 nM

ND

*Schematic for optical biosensor working method [36].*

in optical chips. Through the utilization of evanescent wave technology, the interaction between biomolecules and receptors are measure by the waveguide interferometer in real time without using labels. On a sensor surface, receptors are frozen and the interaction with the close biomolecules leads to a variation in the refractive index. With being far from the surface, the evanescent wave decays exponentially, usually over the distance of 100 nm to approximately a wavelength. Due to the reason that the evanescent wave is a near-surface phenomena, therefore, by using the detection of evanescent wave stimulation to produce fluorescent signal is surface-sensitive. This means that solely fluorescent molecules close to the surface are stimulated as seen in **Figure 4** [37–40].
