**4.2. Application of biosensors**

Dr. Leland C. Clark established the concept of a biosensor as a biological sensing element whose change its properties when reacting biochemically with a specific compound or ana‐ lyte [27]. Such reaction is converted into an electronic signal for its quantification. Dr. Clark developed a glucose oxidase enzyme electrode for detecting glucose.

There are two different approaches which can be carried out by biosensors.


Biosensors are tools basically conformed of a substrate (silicon, glass or polymers). Common polymers are: polymethyl methacrylate, polydimethyl siloxane, etc. The substrate is often coated with a conductive layer like: polysilicon, silicon dioxide, silicon nitrite, gold, and metal oxides. The specific recognition elements include: antigens, antibodies, nucleic acids, whole cells, proteins, enzymes, DNA/RNA probes, and phage-derived biomolecular recog‐ nition probes. The changes in these elements are detected via optical, electrochemical, calori‐ metric, acoustic, piezoelectric (quartz crystal, potassium sodium tartrate, lithium niobate), magnetic, and micromechanical transducers [28].

#### **4.3. Biosensor based on optical techniques**

Optical sensors are analytical tools that satisfy requirements as accuracy, precision and spe‐ cificity in the selection of the analyte, allowing *in vivo* or *in vitro* investigations. Optical tech‐ niques provide a large realm of possibilities based on properties such as absorbance, reflectance and luminescence of single elements or groups of analytes [29].

Among the optical techniques used in biosensors it can be found: non linear optics (based on surface plasmon resonance) [30], resonant mirror, fiber-optics [31], complementary metal ox‐ ide semiconductors, fluorescence/phosphorescence [32], reflectance, light scattering, chemi‐ luminescence, and refractive index [33].

samples; using of highly specific monoclonal antibodies; and incorporating amplification

Characteristics of Mycotoxin Analysis Tools for Tomorrow

http://dx.doi.org/10.5772/51683

299

Latest researches on nanomaterials, such as carbon nanotubes, metal nanoparticles, nano‐ wires, nanocomposite and nanostructurated materials reveal to be a key points in the design

The aforementioned methods to quantify aflatoxins present several disadvantages, for in‐ stance those based on chromatography, however they have laborious and time-consuming process [41]. Therefore, a pathway to improve AFs detection is through biosensors. This term was first used by Cammaann in 1977 [42], who defined it as a device that enables the identification and quantification of the interest sample (e.g. water, air, food, solutions, among others). Nevertheless, the main characteristic in a biosensor is the biological recogni‐ tion element that is capable to create a response of interest. Such element can be an anti‐

There are many kinds of biosensors applied to detection aflatoxins, however they majorly work in conjunction with immunochemical methods. Such junctions are based on the high affinity of antigen-antibody interaction and have the aim of increasing the sensitivity and

These kinds of sensors use mainly immunological receptor units such as antibodies or anti‐ gens, and detection methods as optic effects ( e.g. fluorescence and plasmon resonance), electrochemical, or acoustical readout [44]. The majorly of these techniques are comprised of three main steps: First, the extraction of the aflatoxin from de complex mixtures of materials in which it is found; then, the purification of the sample for removing pollutants; and final‐

The main challenges of these types of biosensors are the design and construction of proto‐ types which minimize their handling. Besides, they must use the best immunochemical techniques, with the aim to generate automated sensors that replace the existing large, complex, cumbersome, and chemical laboratory analysis systems. Such immunochemical biosensors would offer the benefit of an increasingly developing of modular design that would permit the rapid substitution of other reagents to detect different toxics with the

In [45] is reported a biosensor that it is based in the property of fluorescence. This fluores‐ cence system consists on an arc lamp that generates a microsecond flash and a lens that fo‐ cuses in the radiation into the sample. Such sample was previously treated, with process shown on the Figure 3 which in turn shows the three main steps before the antigen detection with the automated process placed in the arrows. Then the detection consists in using a filter which allows the passing of UV radiation, around 365 nm. This wavelength excites the fluo‐

of the near future biosensing systems with applications in aflatoxin detection [40].

steps to generate stronger signals [26].

body, an antigen or an enzyme [43].

**4.6. Immunochemical**

same platforms [45].

rescence of aflatoxins.

decreasing the detection time of the toxic element [41].

ly, the detection and quantification of the toxins [45].

Such advantages, plus their easy operation and wide detection capacity, have made of opti‐ cal biosensors useful tools for the detection of dangerous organisms as aflatoxins.
