**1. Introduction**

The biosensor is an analytical device or probe that combines biological elements (enzymes or antibodies) with an electronic component to produce signals that can easily be measured. It can also be defined as an integrated single device with the

capacity to provide results by recognizing a biological element that is in direct contact with a transducer [1]. This electronic device identifies, processes, and communicates data about the physiological changes of an analyte and the presence of various chemical or biological materials in the environment.

All these biosensors are produced in a variety of sizes and shapes. They can detect and measure even low levels of infections, harmful chemicals, and pH values. On the other hand, biosensing is the act of measuring or detecting the presence of particular chemicals in a physiological activity with the aid of a biosensor device. The major components of the biosensor including the transducer are displayed in **Figure 1**, and they are briefly defined in the following section.

**Analyte**: This biosensor component is the biochemical substance of interest to be identified by the biosensor. A typical example of an analyte in blood glucose can be detected by the glucometer (biosensor) [2].

**Bioreceptor**: This is a biological molecule that recognizes the analytes. Some examples include enzymes, cells, aptamers, deoxyribonucleic acid (DNA), and antibodies. The biological receptor generates a signal in the form of light, heat, pH, charge, or mass change when it interacts with a target analyte in the process known as biorecognition [2].

**Transducer**: This component converts the biochemical signal received from the biological receptor into a measurable and quantifiable signal in a process known as signalization [2].

**Electronics**: This part processes the transduced signals and prepares them for display. Its electronic circuitry is complex, and it also performs signal conditioning such as amplification and conversion of an analog signal into a digital form [2].

**Display**: The display unit consists of a user interpretation system such as the liquid crystal display (LCD) of a computer or a direct printer that generates numbers or curves understandable by the user. It usually consists of a combination of hardware and software that generates results of the biosensor in a user-friendly manner. The output signal on the display can be numeric, graphic, tabular, or an image, depending on the end user's requirements [2].

#### **Figure 1.**

*The main components of a biosensor arranged in chronological order. It begins with the analyte and ends with the end user.*

*Recent Advances in Biosensing in Tissue Engineering and Regenerative Medicine DOI: http://dx.doi.org/10.5772/intechopen.104922*

## **1.1 History of biosensors**

The concept of biosensors has gone through a series of evolution in terms of what is referred to as a "biosensor." Accordingly, biosensing devices have metamorphosed into complex systems since their first invention.

The premier reported idea of biosensing rather than its "term" began in 1906 by M. Cremer. He emphasized that the concentration of an acid suspended in an aqueous solution is equal to the electric potential produced between sections of the solution when separated by a glass membrane [2]. Cremer's discovery led to the introduction of pH by Soren Peder Lauritz Sorensen in 1909. After the invention of an electrode to measure the pH was achieved by Hughes in 1922, 34 years later, an oxygen probe was developed by Leland C. Clark who eventually became the father of biosensors after building what is described as a "real biosensor" in 1959 [3]. Based on this study, he described how "to make electrochemical sensors (pH, polarographic, potentiometric, or conductometric) more intelligent 'by incorporating' enzyme transducers as membrane-enclosed sandwiches" at a conference in New York in 1962 [4].

The term "enzyme electrode" which was originally used to describe the first biosensor was adopted by Updike and Hicks to describe a similar device in 1967 [5]. Guilbault & Montalvo [6] used glass electrodes coupled with urease to measure urea concentration by potentiometric measurement instead of the amperometric method.

In the electrochemical community during that period, the research on ion ionselective electrodes (ISEs) was very active, and the idea of extending the range of sensors to non-electrochemical active compounds had been widely accepted, even for nonionic substances like glucose [5, 7]. Since then, great strides have been made in developing highly sensitive and selective biosensing devices where biological elements are combined with electrochemical sensors [5, 8]. Some of these changes are listed as follows:

