Why nanoparticles are important




















Durethan KU is a packaging film containing nanosilicates to prevent food spoilage developed by Bayer Polymers Pittsburg, USA and is currently available commercially [ 6 ]. Natural bionanopackaging polymers have been prepared from starch and protein molecules with the advantage of better stability for particulate food and ability to deliver functional ingredients. Such biodegradable and innovative nanocomposites have been developed by Plantic Technologies Ltd.

Victoria, Australia using cornstarch. Chitin, a natural polymer found in crustaceans, can be drawn into nanofibers having antimicrobial properties, and such natural nanopackaging materials have great potential to improve food safety, stability, and food quality [ 22 ], [ 23 ]. Active and intelligent packaging systems are used to sense the changes in the food package and signal those changes to consumers while at the same time being capable of releasing active functional ingredients that preserve the food.

Active packaging applications of nanotechnology have the largest share in the market and produced about USD 4. The efficacy of silver-polyamide 6 nanocomposites has been studied against Escherichia coli and has shown persistent and longer antibacterial activity.

Packaging films coated with titanium dioxide TiO 2 have been found active against contamination of food contact surfaces [ 24 ]. Antimicrobial nanoparticles are impregnated on nanolaminates or kept in sachets or dispersed into the package or coated on the surface matrix of packaging material to reduce the microbial growth. Nanoparticles of TiO 2 as oxygen scavengers and enzymes to control off-odors have been successfully developed for processed meat, ready-to-eat food, pasta, and fish products by Sealed Air Corporation Saddle Brook, NJ, USA using the nanotechnology approach [ 2 ], [ 25 ].

Food preservation has a great importance to prevent food spoilage by retarding microbial growth rate. The rapid detection of physical, chemical, and microbial contamination in food is enabled by nanosensors [ 26 ]. Low-cost nanosensors can be introduced in food packages to sense the changes in the quality of food at various stages of storage and transportation. These sensors signal these changes by some visible, optical, or electrical outputs. Nanosensors to detect the presence of insects or pests inside storage systems of grains have been developed in Canada and have the advantage of low power requirement, lightness, and easy installation [ 27 ].

The electronic tongue has been successfully incorporated into packaging materials having the ability to show a visible color change when the package environment changes. Electronic tongue used in smart packaging of food and beverages, developed by Kraft Foods, has a large number of nanoparticles that are sensitive to the changes associated with the staling of fresh food.

Such devices have shown much higher sensitivity to recognize different tastes compared to human tongue [ 28 ], [ 29 ]. Electronic nose with gas sensors is made of nanowires and is able to detect and signal different types of odors in food packages.

An electronic nose has been used to sense the quality change in grain samples in response to fungal contamination [ 30 ], [ 31 ]. Nanofabricated glucose biosensor and liposome nanoparticles have been employed for the detection and quantification of glucose and allergenic proteins in food, respectively [ 32 ], [ 33 ]. A glucose-sensitive enzyme with gold nanoparticles has been reported to successfully quantify the amount of glucose in beverages and the detection of aflatoxin B1 to a limit of 0.

Microfluidic nanosensor, a chip made of silicon, is a rapid device and can detect pathogenic contamination with low sample volumes being used [ 34 ], [ 35 ]. Polychromix Wilmington, MA, USA produced a digital transformer using the nanoelectromechanical system to perform food analysis by estimating trans-fat content in food. These quality-control devices respond through different frequencies using transducers that are capable of detecting biochemical signals produced by any kind of adulteration in food and storage areas.

These devices are portable, low cost, and easy to interpret. A nanocantilever developed by Bio-Finger the European Union funded the project is an innovative silicon biosensor that detects the antigen-antibody and enzyme-substrate reactions and produces electromechanical signals of various frequencies to detect the pathogens, various proteins, chemical toxins, and residual contaminants in food.

One such nanocantilever has been developed to detect pathogenic microorganisms in food and water [ 15 ]. The optical detection of pathogens in a food sample by reflective interferometry using nanoscience works on the principle of measuring light scattered by mitochondria of cells when a known pathogen protein on the silicon nanochip binds to any other similar pathogen protein present in a food sample. Fluorescent dyes to detect pathogens such as Salmonella in food are more rapid than the conventional laboratory methods with less incubation time.

An anti- Salmonella antibody with nanodye particles attached to silver nanorods is a sensor that produces visible color when food is contaminated with Salmonella.

The optical detection of microorganisms such as E. The denser the microbial load present in a food product is, the more the intensity of light produced will be [ 2 ], [ 36 ], [ 37 ]. The detection of pesticides and heavy metal residues is very important in food due to the acute toxicity and adverse effects they pose to human health and the environment.

For instance, the optical properties of quantum dots have been studied to detect pesticide residues in food [ 38 ]. A highly sensitive and accurate optical sensor made of gold nanoparticles has been used to detect the adulteration of pet food and infant food.

The sensor binds to melamine and produces a color change from red to blue based on analyte concentration and thus measures the melamine content of raw milk and infant formula.

The detection of cyanide in drinking water can be efficiently achieved by fluorescent assay of gold nanoparticles used as aggregates and luminescent quantum dots with specific antibodies are able to detect botulinum toxins to picomolar levels to ensure food safety [ 39 ]. The presence of excess moisture and oxygen inside food packages triggers undesirable changes causing food spoilage and the use of nanosensors to detect changes in gas concentration inside package headspace is valuable.

Nanosized particles of TiO 2 and a dye methylene blue have been used to produce a fluorescent indicator ink to detect oxygen concentration inside packages and thus help to control the modified atmosphere package conditions [ 40 ].

Copper nanoparticles coated with carbon are able to detect excess moisture condition inside packages that induce a color change in sensor strips due to the separation and swelling of nanoparticles in the humid environment [ 41 ].

Carbon dioxide detection in modified atmosphere packaging is made possible by fluorescent dyes incorporated in nanobeads [ 42 ]. Pathogen detection methods developed by nanoscience are gaining importance in food analysis as they offer benefits of sensitivity, speed, reproducibility, and high efficiency with less measurement time.

The microbial detection of bacteria, viruses, and toxins becomes convenient due to easily observable optical signals and electrical signals produced by the binding of nanoparticles to antibodies of the target microorganism. Nanotechnology uses magnetic separation assays in combination with antigen-antibody interaction to separate the target pathogen from complex food substrate and then detects it by near or mid-infrared spectroscopy.

For instance, the use of magnetic iron oxide nanoparticles can be used to separate Listeria monocytogenes from contaminated milk. A similar approach detects Brucella antibodies in infected blood serum of cows [ 43 ]. CNTs are hollow tubes made of graphite carbon with an additional atom group attached to their peculiar hexagonal shape, hence becoming low resistance conductors [ 44 ].

The use of nanotubes in food applications is accounted for the unique thermal, chemical, mechanical, optical, and electrical properties of these single-walled or multiwalled nanotubes. The use of these carbon tubes in nanosensors has increased the antimicrobial property of the sensor, which can be attributed to the penetration into microbial cell walls by these tubes leading to irreversible damage and cell death [ 45 ]. For the rapid detection of E. Similarly, an antibody-specific CNT sensor has been used to monitor food quality by identifying Salmonella infections in nutrient solutions.

Multiwalled CNT-containing enzyme cholesterol oxidase on carbon electrode has been designed for cholesterol detection in high-fat food and has shown excellent performance [ 47 ], [ 48 ].

Electrochemical detection using CNTs can be used to detect vitamin content, flavor-producing compounds, and antioxidants in food such as beans and apples as well as the presence of food colorants such as Ponceau 4R and Allura Red in beverages and Sudan-1 in ketchup [ 49 ], [ 50 ].

Various nanosensors are designed using CNTs for the binding of specific antibody and produce a significant change in the conductivity of sensor, which is easily detectable than traditional methods [ 9 ]. The addition of CNTs single walled or multiwalled as fillers to packaging materials resulted in extremely high tensile strength, toughness, and barrier properties in materials such as polypropylene, polyamide, polyvinyl alcohol, and others [ 51 ].

These food-grade nanotubes can serve as carriers of nutrients, supplements, and aroma compounds [ 52 ], [ 53 ]. The CNT gas sensor used in active packaging is able to monitor carbon dioxide and ammonia levels to maintain the requisite gaseous environmental conditions [ 14 ].

Packaging is a coordinated system that ensures the marketing and delivery of goods to consumers in a condition that is safe, acceptable, and without any product modification, typically associated with counterfeiting [ 54 ]. Nanotechnology has helped food business industries to track and trace a food product, to prevent package tampering, and to ensure brand protection.

To avoid the recall of a product from the market, advances in nanotechnology have the potential to improve the traceability and authenticity of the product in the market supply chain [ 55 ]. The use of nanobarcodes on the packages that contain all the necessary product-related information enables the producers to have a look at the product supply chain and to track the product in case of any infringement. Intelligent and disposable label developed by Timestrip is used to measure the time in minutes for which the food product was exposed to abnormal environmental conditions such as higher or lower temperatures than the normal required temperature.

These labels contain nanomembranes that carry the diffused liquid from the food product under different temperature conditions [ 16 ]. Radiofrequency identification RFID chips are nanotag devices that are used to record all the conditions in terms of temperature, humidity, and ambient gas concentration during the transit and storage of product, helping all the players manufacturers, retailers, distributors, and consumers of the supply chain about the freshness, food quality, and food safety.

RFIDs are cheaper and versatile tags that have been successful in detecting whether the product has been distributed timely, especially perishable food products, by providing an accurate report on the quality parameters of these food [ 56 ]. Nanobarcodes developed by Oxonica CA, USA are made from gold, silver, and platinum nanoparticles, each strip coded with biological fingerprint and quality characteristics of the specific food product.

These barcodes, when attached to food products, offer the advantage of brand protection and easy tracking in the supply chain to avoid counterfeiting [ 2 ]. In a similar approach, nanodisks of gold and nickel incorporating chromophores that function by reflecting a light spectrum when hit by a laser beam have been used as biological tags for the detection of DNA and food adulteration [ 57 ].

Information about the soil and climatic conditions can also be encrypted on the product to have a greater security if product recall from the market is due to issues related to the agricultural origin of the product [ 56 ], [ 58 ]. For the issues of food safety, various pathogens such as E. Such products possess enhanced potency, taste, texture, and aesthetical appeal and the technology also helps in maintaining the integrity and stability of these sensitive compounds against degradation during processing and storage.

The growing awareness about the health benefits of natural bioactive compounds has paved an enormous market for functional food and nutraceuticals with a many-fold increase in the efficiency, solubility, bioavailability, and stability of encapsulated active ingredients using nanostructured materials and techniques.

Some examples of nanoencapsulated components in food include lycopene nanoparticles incorporated in tomato juice and jam to increase the antioxidant activity, casein encapsulation as nanomicelles to deliver health-promoting proteins and vitamin D2 in the food substrate, enzyme encapsulation in plant-based nanosilicates with applications in industrial processes and smart delivery systems, and fortification of iron nanoparticles in functional drinks and breakfast cereals [ 27 ], [ 60 ].

Kraft, Unilever, and Nestle are some food industries involved in commercializing novel food fortified with proteins, vitamins, minerals, and fiber as a functional ingredient but reduced calorie and sugar content. Probiotic microorganisms, including Bifidobacteria, have been successfully incorporated in yogurt with a controlled-release mechanism using starch as a nanoencapsulant [ 64 ]. Lipid-based nanoencapsulation has higher bioavailability in the gastrointestinal tract and stability against environmental stress compared to other biomaterials such as proteins, collagen, gelatin, chitosan, and polysaccharides.

Increased activity and target delivery have been studied for antioxidants encapsulated in lipid-based systems [ 65 ]. Nanotechnology-based delivery systems such as nanoemulsions, associated colloids, dispersions, nanocochleates, and micelles have the advantage of delivering the encapsulated ingredients directly onto the site of action, controlling the rate of release under specific environmental triggers such as a change in pH, solubility, and charge.

Such a system also offers protection from physical and chemical degradation and above all is compatible with the organoleptic attributes of food systems. Emulsions formulated using nanoscience are more stable and have novel delivery properties in food systems due to reduced size and increased surface area compared to conventional emulsions [ 70 ]. The nanoencapsulation of various flavor and sensory nanocomponents or microcomponents provides benefits of masking and improving the color, taste, and desirability of various food.

Nanoemulsions are developed with a high-pressure homogenization process to form an adsorbed film of surfactant which is generally protein or phospholipid at the liquid-liquid interface of dispersed and continuous phase. These nanoemulsions have dispersed phase droplets of diameter between 50 and nm and are regarded as true emulsion [ 8 ]. Multiple emulsions are of two types: oil-water-oil and water-oil-water nanoemulsions, which are formed by the electrostatic deposition of layers of polyelectrolyte shell on the surface of lipid droplets core and act as economical carriers of functional ingredients in the food industry.

The rate of release of functional components from the multiple layers of nanoemulsions in food matrix is determined in response to change in pH, electrostatic charge, and porosity of the shell material [ 18 ]. Associated colloids have been used in encapsulating nonpolar ingredients into the hydrophobic core formed from surfactant micelles or vesicles [ 18 ]. Another delivery system of nanocochleates is used to encapsulate hydrophobic, positively and negatively charged compounds into lipid bilayers [ 67 ], [ 71 ].

Micelles 5— nm in diameter are also used to encapsulate bioactive compounds with efficiency in release mechanisms [ 19 ]. Applications of nanoemulsions in food include low-fat ice cream, mayonnaise, spreads, and others developed without any change in the viscosity, mouthfeel, and textural properties [ 63 ], [ 72 ].

Increased bioavailability of curcumin bioactive compound in turmeric has been found when encapsulated as nanoemulsion in processed food [ 73 ]. Antimicrobial nanoemulsion is another application of nanotechnology in food processing and packaging; for instance, antimicrobials such as soyabean oil and tributylphosphate have been found effective as nanoemulsions when they come in contact with contaminated food surfaces based on the electrostatic interaction between the cationic-nanosized ingredient and anionic pathogens [ 69 ].

The application of nanotechnology in the food industry has become prevalent in the last decade or so. However, the use of nanoparticles in food comes with unforeseen harmful effects. We need to analyze the factors that may hamper human health and the environment. Choose any model organism and any nanoparticle and you will find contrasting or slightly different studies about the toxicological effect of the same nanomaterial. After years of research, we have only come to the conclusion that materials at nanoscale show drastically different properties and unexpected behavior.

This unexpected behavior is what leads to our concerns about its toxicity. The interaction between engineered nanoparticles and various living organisms and the environment is still to be explored at large.

There are complaints about the misconceptions [ 75 ] and slow progress in the field [ 76 ]. Nanoparticles have the unique property of increased surface area per unit volume. This renders them to behave completely different from their bulk counterparts. For instance, bulk gold is normally inert, but as soon as we transform this macroscopic gold to nanoparticles, it shows high reactivity and unique properties [ 77 ].

It is due to these unique properties that gold nanoparticles find vast applications from drug delivery to medical imaging. However, nanoparticles are more likely to react with various biological entities such as lipids and proteins or cells as a whole.

Nanoparticles may cross the cell membrane entering various organs and activate inflammatory or other immune responses [ 78 ], [ 79 ]. To foresee the unknown consequences of nanoparticle usage, nanotoxicological studies are performed. A typical toxicity test involves cells or organisms subjected to a specific dose of chemicals nanoparticles, in the case of nanotoxicological studies and measuring the response of the cells over a period of time. The dose-response relationship from these experiments determines the optimum dose and acceptable limits for chemicals.

However, unlike conventional chemicals and their toxicology studies, nanoparticles, as stated earlier have shapes, surface area, and surface electrical charge completely different from bulk counterparts.

These might diffuse, aggregate, sediment, and change the physical and chemical properties of the media they are kept in. The major inference that we draw is that the conventional in vitro assays may misinterpret the results and the dose-response regimes. These conventional assays do not take into account the anomalous behavior of nanoparticles in the environment and their cellular uptake [ 80 ]. Most of the substances considered toxic today are harmless in small quantities and are poisonous only when overly consumed.

The exact quantification of the release of nanoparticles in the environment and occupational exposure is quite a challenge. The half-life and life cycle of nanomaterials based on modeling studies have been reported.

These studies need improvements as data relevant to the industrial production of nanoparticles have not yet been much included in studies, such as the amount that is released at different life cycle stages of these materials and the forms in which these are released into the environment [ 82 ].

Nanomaterials may acquire different chemical and physical forms once released into the environment for they have remarkably different physical and chemical properties with respect to their bulk counterparts.

These novel chemical and physical properties have a huge impact on various ways through which these may interact with biological components, their uptake, accumulation, and clearance through the body, and interaction with the environment at large. There is more than one factor that governs the toxicity of nanoparticles as shown in Figure 1. It is for sure that due to the highly reactive surfaces nanoparticles in the environment cannot exist as bare particles. It has been observed that a corona of protein is acquired by a nanoparticle surface that decides the pathway through which cell uptake, accumulation, and clearance will proceed [ 83 ].

Further, the interaction between the nanoparticle and the biological membrane can be either physical or chemical. Physical interactions mainly result in the disruption of membranes and its activity, protein folding, aggregation, and various transport processes [ 84 ]. In contrast, chemical interactions mainly lead to reactive oxygen species ROS generation and oxidative damage [ 85 ]. The environmental interactions also add complexity to the determination of nanoparticle toxicity [ 86 ].

Human exposure to nanoparticles that are airborne cannot be avoided. The high reactivity of nanoparticles and the multiple entry routes aggravate the problem Figure 2.

These particles can travel large distances facilitated by Brownian motion and are likely to get deposited into our air sacs [ 87 ]. Nanoparticle toxicity has been dealt with approaches similar to conventional toxicity analysis.

Most of the studies have suggested oxidative stress as a major parameter for nanotoxicity analysis. As discussed earlier, nanoparticles may have varied shape, size, charge, solubility, and chemistry as a whole. CNTs, for example, have been extensively studied for its toxicological impact on living beings [ 88 ]. The toxicity potential of these nanotubes has come to light due to its striking similarity to different carcinogens such as asbestos.

However, when considering the toxicity, it is not only the nanoparticle but also the various other factors one should consider. CNTs, for instance, can be single walled or multiwalled, functionalized or nonfunctionalized, may or may not be conjugated with the metal catalyst, or may be hydrophobic or hydrophilic depending on the functional group attached and many more such factors need to be considered [ 89 ].

As it would become cumbersome to test each and every parameter for toxicity, toxicologists have identified key parameters or tests that allow scientists to screen safer nanomaterials. A major step in the direction was taken by Xia et al. The basic idea of the study was to know the mechanism and thus compare the toxicity potential of various nanomaterials. This can be done simply by looking at the generation of reactive species within the cell.

Oxidative stress results from the imbalance between oxidants ROS, peroxide, etc. An increase in the number of oxidants in the cell can have damaging effects on the cell. There is abundant literature on pollution particles such as carbon soot and other nanosized pollutants that lead to the generation of ROS and can lead to oxidative stress Figure 3 [ 91 ]. With the study conducted by Nel et al. The data can be further extrapolated to newer materials [ 89 ]. If carefully thought out, this and other similar studies can serve as an important building block toward a more efficient screening system for nanotoxicology.

Although the study provides insights into the oxidative damage that can be caused by different nanomaterials, a few avenues were left unexplored. First, the experiments should be conducted on more than one cell line; also, primary cell culture such as human macrophages should also be used to make sure that the cell culture model is foolproof.

Second, different dose regimes should be considered and doses used should be comparable to the dose of the nanomaterial being released into the environment. Third, different media formulations need to be tested as most of the studies have been carried out with fetal calf serum FCS.

FCS contains high levels of different antioxidants. These antioxidants may mask the oxidative damage caused by nanomaterials.

Last but not the least, some supplementary assays need to be done to complete the picture. For example, both intracellular and extracellular oxidative stress need to be monitored. The field is in its early days and there is so much to explore. The fact that their particles can distort lipid organization and overall membrane structure [ 92 ] is an evidence in itself that the nanoparticles may affect biology as a whole.

There is an urgent need for information to better understand the nanoparticle-biological interactions and processes. These interactions primarily involve biomolecules such as proteins, but there are studies that show us different routes to monitor the same.

Granick et al. Different modes in which a cell can uptake substances. A similar mechanism is what nanoparticles are expected to follow. Therefore, it would be too early to jump to conclusions or to prefer a single field of study. For now, we can say that understanding the manner in which nanoparticles interact physical or chemical with biological molecules or living matter can open up loads of opportunities to the field of toxicology. The knowledge and mechanism of oxidative stress seem to be the aptest parameter and appeal maximally to discriminate between toxic and nontoxic materials.

The near-future goal of nanotoxicologists seems to develop more studies based on the works of Nel et al. This will help us learn about the mechanism responsible for nanomaterial-induced toxicity and lead us to safe and profitable nanotechnology.

It also emphasizes on learning lessons from alternative methods and their validation. New problems should be dealt with new solutions, and nanotoxicity is one big example. Most of the toxicology tools that are being used for the assessment of toxicity potential of products, mainly nanoparticles, rely on high concentration or dose regime animal studies. These methods have remained unchanged for years. Knowledge in biological sciences doubles really quickly. We now have tons of knowledge and data as we had 60—70 years back.

We cannot fuel our cars with a more advanced fuel if we do not change its engine. Similarly, what we need today are better predictive models and tools to minimize time and costs.

Studying the properties of individual nanoparticles, their exposure route, exposure time, the right dose and the right model system can be time-consuming, tedious and expensive. It is here, where high throughput screening methods and computational approaches slide in to save our day.

These can rapidly screen and prioritize nanoparticles for toxicology assays and thus accelerating the process of establishing a relationship between material and its biological behavior [ 96 ]. Quantitative nanostructure-activity relationship [ 97 ] can help us predict the cytotoxicity of a number of metal nanoparticles [ 98 ].

Another important aspect to be considered for the field to progress is a detailed characterization of the nanomaterial in question, this would help researchers to use that data to design toxicology assays, properly interpret the results obtained and ensure that data can be reproduced and compared by others. Although researchers have initiated the knowhow of material properties, interactions, and toxicity mechanism, the coming years still have a big challenge to understand the physical and chemical properties, interactions and responses.

Most of the modern toxicology studies are animal based in vitro or in silico ; however, there is a need for evidence-based toxicology. With such vast knowledge and advancements, the current toxicological assays need to be revamped and new tools, such as proteomics, functional genomics, high-throughput screening, and metabolomics, to name a few, should be incorporated more and more to these studies.

Incorporation of these advanced tools will lead to the minimization of a number of false positives and accelerate and validate the evaluation of toxicity of nanoparticles.

The onus of nanotechnology and its safe applications is on the shoulders of scientists and the public must be well informed on the benefits and risks associated with the field. The use of nanotechnology in food irrespective of its wide benefits confers the possible adverse environmental, social, and health risks as these particles are believed to enter the ecosystem through the delivery of pesticides in agriculture or through application in processed food such as the packaging sector, thus raising the toxicity concerns about their usage [ 99 ].

The enhanced risk of nanoengineered particles is due to the higher reactivity of these nanoparticles and increased bioavailability of smaller particles to our bodies leading to long-term pathological effects. Nanomaterials can enter the food chain through:. Direct incorporation of nanoparticles in novel food as nanoemulsions, nanocapsules, and nanoantimicrobial films.

By use of nanomaterials in food manufacturing, processing, preservation, and trackings such as the use of nanolaminates, nanosensors, and CNTs. More about Nanoparticle Applications in the Environment. Researchers at Rice University have determined that the shape of aluminum nanoparticles made a significant difference in the reaction rate when the nanoparticles are used as photocatalysts. Researchers at the Imperial College London have modeled the use of nanoparticles to reduce reflective losses in LEDs to improve their performance.

They are proposing a layer of nanoparticles between the LED chip and the transparent casing and are planning to manufacture prototypes to verify the best configurations of the nanoparticles. Researchers at Georgia Tech have determined that oxide-coated antimony nanocrystals used in the anode of a Li-ion battery may prevent mechanical degradation of the anode at high power cycling. Researchers have used nanoparticles called nanotetrapods studded with nanoparticles of carbon to develop low cost electrodes for fuel cells.

This electrode may be able to replace the expensive platinum needed for fuel cell catalysts. Researchers at Georgia Tech, the University of Tokyo and Microsoft Research have developed a method to print prototype circuit boards using standard inkjet printers. Silver nanoparticle ink was used to form the conductive lines needed in circuit boards. This transistor is unusual in that it can function in a way similar to synapses in the nervous system.

A catalyst using platinum-cobalt nanoparticles is being developed for fuel cells that produces twelve times more catalytic activity than pure platinum. In order to achieve this performance, researchers anneal nanoparticles to form them into a crystalline lattice, reducing the spacing between platinum atoms on the surface and increasing their reactivity.

Researchers have demonstrated that sunlight, concentrated on nanoparticles, can produce steam with high energy efficiency. The " solar steam device " is intended to be used in areas of developing countries without electricity for applications such as purifying water or disinfecting dental instruments. A lead free solder reliable enough for space missions and other high stress environments using copper nanoparticles.

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