Applications of Nanotechnology in Agriculture and Food Science

Module 2Bioe298 DP

Nanotechnology has applications in all areas of food science, from agriculture to food processing to security to packaging to nutrition and neutraceuticals.

Duncan, J. Colloid and Interface Sc. 2011.

‘Nano’ foods nowAll foods contain nanoparticles. Examples of foods that contain nanoparticles include milk and meat.

Milk contains caseins, a form of milk protein present at the nanoscale. Meat is made up of protein filaments that are much less than 100nm thin.

The organisation and change to the structures of these affects the texture and properties of the milk or meat.

Applications of nanotechnology

Uses for nanotechnology in food

• nanocarrier systems for delivery of nutrients and supplements;

• organic nano-sized additives for food, supplements and animal feed;

Nanotechnologies are being developed all the time. Here are some examples that are being used:

• food packaging applications e.g. plastic polymers containing or coated with nanomaterials for improved mechanical or functional properties;

• nanocoatings on food contact surfaces for barrier or antimicrobial properties;

• nano-sized agrochemicals (a chemical used in agriculture, such as a pesticide or a fertilizer.);

• nanosensors for food labelling.

Nanoparticles are being used to deliver vitamins or other nutrients in food and drinks without affecting the taste or appearance. These nanoparticles encapsulate the nutrients and carry them through the stomach into the bloodstream.

Food examples

Nanoparticle emulsions are being used in ice cream and various spreads to improve the texture and uniformity.

New developments in nanoscience and nanotechnology will allow more control and have the potential of increased benefits. These include:

• healthier foods (e.g. lower fat, lower salt) with desirable sensory properties;

• ingredients with improved properties; • potential for removal of certain additives without loss

of stability;• smart-aids for processing foods to remove allergens

such as peanut protein.

Food examples

Packaging examples

Researches have produced smart packages that can tell consumers about the freshness of milk or meat.When oxidation occurs in the package, nanoparticles indicates the colour change and the consumer can see if the product is fresh or not.

Incorporation of nanoparticles in packaging can increase the barrier to oxygen and slow down degradation of foodduring storage.

Bottles made with nanocomposites minimise the leakage of carbon dioxide out of the bottle.

This increases the shelf life of fizzy drinks without having to use heavier glass bottles or more expensive cans.

Food storage bins have silver nanoparticles embedded in the plastic. The silver nanoparticles kill bacteria from any food previously stored in the bins, minimising harmful bacteria.

Packaging examples

Gene deliveryMomentumKinetic energyCurrentCharge

https://sites.google.com/site/activecarephysiotherapyclinic/parkinsons-disease

Gene Delivery

http://gene-therapy.yolasite.com/process.php

• Biolistic particle delivery system, originally designed for plant transformation

• Device for injecting cells with genetic information. The payload is an elemental particle of a heavy metal coated with plasmid DNA.

• This technique is often simply referred to as bio-ballistics or bio-listics.

Gene Gun

Comparative study of different delivery systems

Source: Rai,M., Deshmukh, S. , Gade, A., Elsalam, K.A. 2012 . Current Nanoscience .8 : 170-179

Vehicles for Nuclear Transformation in Plants

Agro-bacterium mediated:

Most extensively used, wide host range (mostly dicotyledonous)Incompatibility between tissues of plant species

Electroporation:Generate transgenic plants by protoplast transformation Cell damage by electric pulses of wrong length, ion imbalance and cell death

Microparticle Bombardment:

Capable of delivering DNA into nucleus, mitochondriaCell Damage, high copy number of transgene, expensive equipment

Purpose: To introduce MSN into plants with gene gun system

Figure: Gene gun system for bombarding micro/nano particles

Source: http://swineflucaretips.blogspot.com/2012/06/dna-vaccines-and-gene-gun.html

Purpose : To deliver different biogenic species simultaneously

• Release the encapsulated chemicals in a controlled fashion• Generate transgenic tobacco containing inducible promoter controlled GFP gene

• Expression of GFP observed only when chemical β-oestradiol is present• Transgenic plantlets bombarded with Type-IV MSNs ( filled with β-oestradiol) , and pores capped with gold nanoparticles• Release of β-oestradiol is triggered by DTT ( Dithiotheritol)

Nanoparticle Mediated Genetic Transformation

• Decreasing the particle size from micro to nano scale, hindrance due to cell wall can be removed

• Cell Damage can be minimized• The particle can reach the chloroplast

and mitochondria easily

• Different NPs used are calcium phosphate, Carbon materials, silica, gold magnetite, strontium phosphate.

• Enable controlled release conditions

Nanoparticles combined with chemical compounds deliver genes into target cells

Figure: Synthesis of mesoporous silica

Source: http://www.rmat.ceram.titech.ac.jp/research-e/mesoporus-e.html

Mesoporous silica Nanoparticles for plant cell internalization

Experiment with MSNs – Genetic Transformation

Figure : Type-I and Type-II MSNs

Synthesize series of MSNs with different surface functional groups/caps

Investigation of MSN in protoplasts (plant cells with cell wall removed)

Protoplasts incubated with Type-I MSN didn’t take up nanoparticles, Type-II MSN ( Type-I functionalized with

triethylene glycol) entered the protoplasts

• MSN system can serve as a new and versatile tool for plant endocytosis and cell biology studies

Purpose: To investigate interaction of MSN with plant cells

Antimicrobial Activity of Silver Nanoparticles

• Silver has antibacterial properties. However as nanoparticles the antibacterial properties are magnified, as the surface area to volume ratio is increased, allowing them to easily interact with and fight with bacteria more efficiently. Silver nanoparticles

AgNPs are potent broad spectrum antimicrobials: minimum inhibitory concentrations of 2–4 g/mL for AgNPs with diameters 45–50 nm against E. coli, V. cholerae, S.flexneri, and at least one strain of S. aureus, have been reported, which rivals the bactericidal properties of penicillin against nonresistant strains.

Potency can be easily manipulated through the unique physical effects offered by nanomaterials.

Silver nanowires are subjected to external electric fields, they have 18.5–63% better antimicrobial potency due to enhanced silver ion production at the wire termini.

Also, photoexcitation of AgNPs coated with a thin (1-2 nm) layer of porous silica at visible light frequencies which are in resonance with AgNP surface plasmon bands has been shown to enhance antimicrobial activity against E. coli significantly, either through photosensitized ROS generation or photocatalyzed silver ion release; this effect is also reversible, providing a portal into photo-switchable antimicrobial behavior.

Uses of silver nanoparticles

• In refrigerators, washing machines, air-conditioners, clothing, baby pacifiers, food containers, detergent, surgical instruments, etc.

Absorption spectra of Ag nanoparticle solutions (A). The solid line is for Ag nanoparticle solution as prepared, the dashed one is for the ten-time concentrated one after diluted back to the original concentration, and the dotted one is for the solution left after the Ag nanoparticles are removed by sedimentation. The maximum potential peaks of Ag nanoparticles were measured at -0.33mV (B). The effective zeta-potential in aqueous solution were measured by particle characterizer bDelsa 440 SXQ (Coulter Ltd., Miami, FL), and the mean values were averaged from 3 times assay data.

(A) A TEM image of Ag nanoparticles dispersed on a TEM copper grid (a, scale bar: 30 nm). (B) A histogram showing size distribution of Ag nanoparticles.

Growth inhibition of Ag nanoparticles against yeast. Itraconasol, distilled water, and solution devoid of Ag stand were used for the positive control, negative control, and vehicle control. The concentration of gold nanoparticles was 30 nM.

Mechanisms of Silver Nanoparticle Bacteriocidicity. (A and B) Silvernanoparticles (AgNPs) are lethal to bacteria in part because they damage cell membranes. The figure shows pictures from separate studies demonstrating adherence of AgNPs to and subsequent pitting of the membrane surface of E. coli.(C) Due at least in part to damage of cell membranes, the presence of AgNPs reduces E. coli growth and viability. Here, a photograph shows growth of E. coli on LB plates containing AgNPs at (i) 0, (ii) 10, (iii) 20 and (iv) 50 lgcm3. (D) Numerous studies have explored factors which influence AgNP lethality. This plot relates the number of bacterial colonies able to grow on plates incubated with various amounts of AgNPs, as a function of AgNP shape. Other factors which influence AgNP antimicrobial efficiency include particle size, surface charge, and the nature of substituents featured on the particles’ surfaces.

Antimicrobial activity of silver nanoparticles

Problem:An adulterant used to artificially inflate the measured protein content of pet foods and infant formulas.

Melamine is - "Harmful if swallowed, inhaled or absorbed through the skin. Chronic exposure may cause cancer or reproductive damage. Eye, skin and respiratory irritant."

Solution: The melamine-induced aggregation causes AuNPs to undergo a reproducible, analyte-concentration-dependent color change from red to blue, which can be used to precisely measure the melamine content in raw milk and infant formula at concentrations as low as 2.5 ppb with the naked eye

Detection of Small Organic Molecules

Nanosensors and nanotechnology-based assays for food relevant analytes

(a) Schematic showing colorimetric detection of melamine in solution using modified gold nanoparticles (AuNPs). AuNPs are conjugated to a cyanuric acid derivative, which selectively binds to melamine by hydrogen bonding interactions. When bound to melamine, aggregated AuNPs (blue) exhibit different absorptive properties than ‘‘free’’ AuNPs (red). (b) Visual color changes of AuNP-melamine sensor in real milk samples: (1) AuNP solution without any addition; (2) with the addition of the extract from blank raw milk; (3), (4) and (5) with the addition of the extract containing 1 ppm (final concentration: 8 ppb) melamine, 2.5 ppm (final concentration: 20 ppb) melamine and 5 ppm (final concentration: 40 ppb) melamine,respectively.

Detection of Gasses

Photographs of O2 sensors which utilize UV-activated TiO2 Nanoparticles and methylene blue indicator dye, one placed inside of a food package flushed with CO and one placed outside. In (a) the package is freshly sealed and both indicators are blue. The photograph in (b) shows the indicators immediately after activation with UVA light. After a few minutes, the indicator outside of the package returns to a blue color, whereas the indicator in an oxygen-free atmosphere remains white (c) until the package is opened, in which case the influx of oxygen causes it to change back to blue (d). This system could be used to easily and noninvasively detect the presence of leaks in every package immediately after production and at retail sites.

Moisture sensor which utilizes carbon-coated copper nanoparticles dispersed in a polymer matrix (a). Ethanol vapor exposure results in rapid and reversible iridescent coloration (b). Water vapor exposure swells the polymer, which causes the nanoparticles to exhibit larger inter particle separation distances and thus different observable optical behavior (c). As moisture dissipates (d–f), the sensor reverts back to its native state and appearance. Reprinted with permission

(a) Antibodies selective for specific bacterial strains or species (e.g., E. coli) are bound to the surfaces of magnetic nanoparticles (e.g., Fe). Only the targeted organisms will bind to the functionalized magnetic nanoparticles. (b) A complex matrix (e.g., food, blood, milk, etc.) contains the target analyte as well as numerous potential interferences, such as other bacterial species, viruses, proteins, food or blood particles, etc. Functionalized magnetic nanoparticles are added to the matrix, where they bind selectively and with high capture efficiency to the target analyte. A magnetic field isolates the analyte-bound magnetic particles, after which the supernatant is then carefully decanted. The remaining material is then subjected to quantification assays. In more sophisticated systems, the magnetic nanoparticles themselves are the means of detection and quantification

IMS-based detection methods using magnetic nanoparticles.

Barrier Applications of Polymer Nanocomposites

• A critical issue in food packaging is that of migration and permeability.

• No material is completely impermeable to atmospheric gasses, water vapor, or natural substances contained within the food being packaged or even the packaging material itself.

• High barriers to migration or gas diffusion are undesirable, such as in packages for fresh fruits and vegetables whose shelf life is dependent on access to a continual supply of oxygen for sustained cellular respiration.

• Plastics utilized for carbonated beverage containers, on the other hand, must have high oxygen and carbon dioxide barriers in order to prevent oxidation and decarbonation of the beverage contents .

• In other products, migration of carbon dioxide is far less of an issue than that of either oxygen or water vapor. As a result of these complexities, food products require sophisticated and remarkably different packaging functions, and the demands on the packaging industry will only increase as food is transported over increasingly longer distances between producers and consumers.

Illustration of the ‘‘tortuous pathway’’ created by incorporation of exfoliated clay nanoplatelets into a polymer matrix film. In a film composed only of polymer (a), diffusing gas molecules on average migrate via a pathway that is perpendicular to the film orientation. In a nanocomposite (b), diffusing molecules must navigate around impenetrable particles/platelets and through interfacial zones which have different permeability characteristics than those of the virgin polymer. The tortuous pathway increases the mean gas diffusion length and, thus, the shelf-life of spoilable foods.

Conclusion

• Nanobiotechnology could take the genetic engineering of agriculture to the next level down – atomic engineering

• Further developments such as pore enlargement and multifunctionalization of these NPs may offer new possibilities in target specific delivery of proteins, nucleotides and chemicals.

• Opposition is mounting from civil society, unions and world leading scientists who point to ecological, health and socio-economic risks associated with nanogenetics.