**4.4 Detection of metal contaminants**

*Novel Nanomaterials*

**4.2 Detection of mycotoxins**

a detection limit of 7 nM [58, 59].

**4.3 Detection of pesticides**

*Escherichia coli (E. coli)* O157:H7 has been detected using synthesized attractive 3D architecture of silver (Ag) nanoparticles as nanoflowers as the interface material for electrochemical biosensing [49]. Bovine serum albumin (BSA) has been used as stabilizing agent for proper conjugation of Ag nanoflowers. *Salmonella* spp. a food pathogenic organism responsible for causing salmonellosis diseases, [50] millions of people are naffected by this disease annually in all over the World [50–52]. Magnetic nanoparticles and TiO2 nanocrystals are used to detect the *Salmonella* in milk [53]. In this method the pathogen is first captured by antibody-immobilized magnetic NPs. Then antibody-conjugated TiO2 binds the MNP–*Salmonella* complexes and this was monitored by absorbance measurement. This method sensitive enough to

Mycotoxin is the toxic metabolites secreted by fungus during its growth and development. Some of the major example for mycotoxin are ochratoxin synthesized by penicillium, aflatoxin secreted by *Aspergillus.* Many agricultural and horticultural food crops are easily affected by different group of pathogenic fungi so invariably food material produced from the affected plants contaminated with mycotoxins. The importance of the mycotoxin is, these create severe health complication even at in small concentrations [54, 55]. Many type of nanomaterial are used to synthesize the nanobiosensor, among all carbon based nanomaterials graphene and its derivatives have great oppurtunity to detect the mycotoxins from various food sample. A nanocomposite of graphene oxide and gold nanocomposites (GO/AuNCs) has high sensitivity detection of aflatoxin B1 (AFB1) in peanut samples [56, 57]. The improvement in sensitivity of the biosensor is due to better quenching ability of nanocomposite. Moreover low detection limit with wide linear range leads to better reliability and wider applicability of such biosensors. Gold nanoparticle (AuNP) based aptasensor is used to detect the aflatoxin B1 with

After green revolution the application and usage of chemical pesticide shoots very high in order to get more yield. In this farmers might have got success in the sense of productivity but at the same time contamination of food material with chemical pesticide is also unavoidable, this issue creates insecurity in the food safety. Organophosphorus (OP) and carbamates (C) are the pesticides used mostly representing ~40% of the world pesticide market [60, 61]. Acetylcholinesterase (AChE) is one of the important enzyme in our body, this catalyses the hydrolysis of neurotransmitter acetylcholine. Primarily the pesticide molecule inhibit this enzyme activity, hence pesticide toxin presence in food ultimately affect the human body dangerously [62, 63]. In order to avoid this the food material should be analysed and detected the amount of pesticide residues exist before its consumption. Commercially many techniques such as chromatographic techniques (GC and HPLC) and coupled chromatographic-spectrometric procedures such as GC–MS and HPLC-MS are available, perhaps these methods are more costlier and not able to do the real time analysis [64]. Mostly pesticide detection is done by measuring AChE activity before and after exposure to the pesticides through colorimetric Ellman assay [65]. AuNPs (3 nm) nanoparticles based biosensors are used to detect the many pesticide molecule like paraoxon, dimethoate, carbaryl, chlorpyrifos, carbofuran, etc. at a concentration of 24 μg/mL [66–69]. The Lum-AgNPs were used in conjunction with a H2O2 based CL detection to generate

detect of 100 CFU/mL for Salmonella in milk sample [53].

**202**

Heavy metal ions like mercury, lead, cadmium, arsenic etc., are present in the environment. When food crops are cultivated in such environment, heavy metal residues are accumulated in food. Consumption of this heavy metal contaminated food will create various disorders and health issues such as neurological, reproductive, cardiovascular problems [71]. AuNP-based sensors working based upon colorimetric detection was used to detect the metal ions in water with the detection limits of 30 ppb for Pb2+ and 89 ppb for Al3+ [72]. AuNPs based sensors also used to detect the other heavy metals like Hg2+ [73–77], Cu2+ and Ag+ [78], Mn2+ [79], Cd2+ [80, 81], Fe3+, Pb2+, Al3+, Cu2+, and Cr3+ [77].

## **4.5 Nanobiosensors for intelligent food packaging or smart packaging**

Normally packaging of food helps to maintain the nutrient content and increasing the shelf life. But smart packaging is have an added option, it indicate the temporal and spatial changes occur in the food constituents that contains with in it. Intelligent tags and stickers are combined with nanobiosensing material inside the packaging and nanobiosensor connected with consumers through electronic devises will indicate the real time sensing data about the food material present whether normal or deteriorated from time to time [82–84]. These work by sensing through a nanobiosensor integrated with polymer film or polymer matrix and radio frequency identification (RFID) components are used by intelligent tags to sensing [85, 86]. Biosensors for food packaging can function in particular physico-chemical conditions in the packaged microenvironment. Zeolite-molybdate tablets are prepared by placing Ammonium molybdate in to the zeolite nanopores used to detect and measure ethylene in avocados packages. In ten day old package, the zeolite-molybdate tablet changes its colur from yellow to blue because of the redction of Mo(VI) to Mo(V) [87–89].

#### **4.6 Nanobiosensors in E-nose technology**

Most common factors for food rotting and developing of foul odor in food is pathogenic bacteria. Above certain level of odors can be sensed by the human nose, but sometimes it may not be useful to prevent of food poisoning. Therefore, rapid assessment of odor at earlier stage should be most useful, in this regard nanobiosensors can be used for the detection of these odors with high sensitivity. Nanoparticles help in better absorption of gas on sensor surface due to more surface area than macroscopic particles [90, 91].

Electronic nose (E-nose) is used to identify different types volatile organic compounds present in food to ensure good quality, uniformity and consistency of raw material during mixing, cooking and of final product during packaging and storage processes [92]. Gas sensors composed of nanoparticles e.g. ZnO nanowires are used to detect the gas. More amount of ethylene gas fruits and vegetables deteriorates its quality, Tungsten oxide–tin oxide nanocomposites have been employed for ethylene sensing [93]. SWCNT field-effect transistor functionalized with human olfactory receptor 2AG1 protein has been employed for sensing fruit odorant amyl butyrate

in apricot [94, 95]. Olfactory receptors-functionalized carbon nanotubes-based transistor has been documented for the selective detection of hexanal as olfactory indicator of spoiled milk and oxidized food [96].
