**4. Biosensors for aflatoxins**

Aflatoxins are harmful organisms. Their toxicity is due to their capacity to covalent binding DNA and proteins. The most acutely and chronically toxic aflatoxin is the B1. The legal lim‐ its set for AFB1 or for total aflatoxins vary from country to country [25]. The detection and quantification of aflatoxins are the first steps in the challenging task of controlling such or‐ ganisms.

The rearing of livestock, the storage of grains, and the stock of their derivatives are daily life activities which are susceptible to be infected with pests and diseases. Such infections may cause human death and economical losses.

Every topic exposed in this chapter is so vast that could be by itself a single chapter. The aims of this chapter are to give a general overview of all the existing methods for the meas‐ urement and quantification of aflatoxins; to signalize their principles of operation; and to ex‐ pose their tendencies.

Biosensors are multidisciplinary tools with an enormous potential in detection and quantifi‐ cation of aflatoxins. Thus, such devices have a huge impact in healthcare, food management, agronomical economy and bio-defense [26].

#### **4.1. Biosensors**

**3.4. Recent advances**

296 Aflatoxins - Recent Advances and Future Prospects

increase its sensitivity.

reported materials.

ganisms.

**4. Biosensors for aflatoxins**

cause human death and economical losses.

ELISA has been modified by using electrochemical techniques. Antibodies or antigens may be immobilized on an electrode with a free and enzyme-conjugate. So in a competitive as‐ say, some enzyme-conjugate will bind to the electrode, and enzyme density can be shown by current produced from the catalytic oxidation reaction of the enzyme with the substrates. In a non-competitive assay, the formation of an Ab-Ag complex generates a barrier of direct electrical communication between the immobilized enzyme and the electrode surface.

Some authors have reported the use of electrochemical sensors. In [19] developed a sensor based on enzymatic silver deposition amplification to detect AFB1 in rice. A linear sweep voltage was done in order to read the sensor response. In [20] the authors proposed the use

Optical ELISAs often uses surface plasmon resonance (SPR). They are similar to electro‐ chemical sensors, but in SPR, Ab or Ag is immobilized in an optical-sensitive surface. As AFB1 changes, the angle of Spectral Power Distribution (SPD) varies. A combination of com‐ petitive-direct ELISA and an immunochromatographic assay was done by [21], in order to

In recent years, some articles have developed modifications on ELISAs (e.g. with the using of nano particles). In [22] the authors refined the ELISA process for aflatoxin detection by using anti-AFB1 single chain fragment variables, in order to detect only free AFB1 instead of an AFB1-protein conjugate. In the references [23] developed an ultra-sensitive ELISA by cou‐ pling a micro plate ELISA with sensitive magnetic particles. An important feature of this hy‐ brid system is its small column size, high capture efficiency and lower cost over other

A combination of a competitive direct ELISA and gold nanoparticle immunochromatograph‐ ic strip was done by [21], with a detection limit of 1.0 ng/ml for AFM1 in milk. Immunochro‐ matographic assay (ICA) is rapid and simple, and can be carried out by untrained personnel without using electronic devices. However, this type of assay has low selectivity, so in [24],

Aflatoxins are harmful organisms. Their toxicity is due to their capacity to covalent binding DNA and proteins. The most acutely and chronically toxic aflatoxin is the B1. The legal lim‐ its set for AFB1 or for total aflatoxins vary from country to country [25]. The detection and quantification of aflatoxins are the first steps in the challenging task of controlling such or‐

The rearing of livestock, the storage of grains, and the stock of their derivatives are daily life activities which are susceptible to be infected with pests and diseases. Such infections may

an improved ICA by using a new monoclonal antibody against AFB1 was developed.

of electrical impedance spectroscopy and free-labeled molecules.

The International Union of Pure and Applied Chemistry (IUPAC) define biosensor as:

"A device that uses specific biochemical reactions mediated by isolated enzymes, immuno‐ systems, tissues, organelles or whole cells to detect chemical compounds usually by electri‐ cal, thermal or optical signals".
