19.4.3 Conducting Polymer-Based Sensors for Foodborne Toxins, Food

Spoilage, and Foodborne Pathogens

The presence of pathogens, toxins in food, and food spoilage, in general, are of great

concern because they can cause serious health problems. Therefore, there is a continuous

effort to develop effective techniques for sensing foodborne toxins and pathogens [18,42].

One of the techniques used in recent times is biosensors. Conducting polymers have been

fairly applied in biosensor technologies for toxin and food pathogen detection [43].

Ochratoxin A, a mycotoxin found in food products, meat, and breastmilk, was previously

detected by Yu et al. [44]. The research demonstrated for the first time; a chlorine-doped

polypyrrole-based surface plasmon resonance sensor for the toxin [44]. Khan et al. also

detected ochratoxin A using a composite of polyaniline and chitosan (PANi-CS). They

immobilized a rabbit IgG on the composite for the interaction. This impedimetric sensor

produced a detection limit of 1 ng/mL [42]. Another research by Khan et al. reported a

polyaniline and acacia gum-based ochratoxin sensor [45].

Aflatoxin B1, another mycotoxin, is known to be hepatotoxic and carcinogenic.

Determination of the levels of this toxin is very important. Linting et al. proposed gra­

phene and conducting polymer-based immunosensor for aflatoxin B1. The composite was

constituted by 2,5-di-(2-thienyl)-1-pyrrole-1-(p-benzoic acid) (DPB) and graphene oxide.

The sensitivity of the sensor was very impressive. The detection limit was as low as 1 fM

(1 × 10⁻¹⁵) and a very wide linear range of 3.2 fM to 3.2 Pm [46]. Similarly, PEDOT was

used in another immunosensor for aflatoxin B1 [47].

Degradation of food is in principle, accompanied by the release of molecules into their

immediate environment. These molecules produced because of degradation are sometimes

useful for the detection of food spoilage. Several researchers have demonstrated the prospect

of conducting polymers for spoilage sensors. Polyaniline was used in a sensor for the de­

tection of ammonia gas emanating from the spoilage of protein-rich foods [48,49]. Also, there

are several commercially available electronic nose sensors such as Cyranose−320™ [50] and

Aromascan A32S that make use of conducting polymers. Food spoilage is sometimes caused

by microorganisms. The use of conducting polymers for the detection of foodborne micro­

organisms has been reviewed in detail by Arshak et al. [18]. From their review, they noted

that conducting polymers have been used extensively for the detection of foodborne pa­

thogens. Polyaniline and polypyrrole were the most used polymers in this regard.

19.5 Conclusion and Future Prospective

The application of conducting polymers to develop electrochemical sensors for detecting

metabolites such as drugs, biomolecules, foodborne toxins, and pathogens is increasing.

This is due to their unique properties that include high electrocatalytic activity and good

conductivity. However, over the years, it has been discovered that electrochemical sensors

made up of pure conducting polymers are affected by some disadvantages such as poor

selectivity, low sensitivity, and surface poisoning due to adsorbed intermediates and in­

terface from other species. Also, these polymers are fragile structures with poor adhesion to

the electrode. To overcome these drawbacks, nanostructured conducting polymers and

nanocomposites consisting of conducting polymers and various nanomaterials are being

developed. More studies still need to be done on nanostructured conducting polymers for

metabolite sensing.

Conducting Polymer Composites

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