Science aspires to understand our world to improve life and satisfy our natural curiosity. But that pursuit can sometimes create new problems, which come with its own risks.
Nanoparticles fall into that category.
These tiny particles are between 1 and 100 nanometers in size. Nanoparticles have unique physical and chemical properties because of its high surface to volume ratio. Those differences yield performance improvements in various applications.
Because of that, scientists use nanoparticles in a variety of applications, including medicine, pharmaceuticals, electronics, biomaterials, energy production and consumer products.
For example, nanoparticles may immediately adsorb onto their surface some of the large molecules of living organisms as it enters the tissues and fluids of the body - known as the corona effect. Doctors can deliver a drug directly to a specific cell in the body by designing the surface of a nanoparticle so that it adsorbs specifically onto the surface of the target cell.
Food science is also benefiting from nanoparticle technology. A little background first.
Estimates reveal that by the year 2050, the world’s population will require a 70 percent increase in our food supply. Scientists believe we can’t reach that demand by just growing more. We have to innovate.
One third of food produced is lost or wasted due to flaws in process, economics, energy, behavior, and policy, according to researchers at Ohio State University.
Manufacturers use nanotechnology to improve food production, processing, storage, and quality control. It can also improve the sensory quality of foods by exposing novel texture, color, and appearance. Scientists likewise use nanoparticles as nanosensors for rapidly detecting food spoilage and contamination.
There is a downside, though. Scientists worry about nanoparticle toxicity.
Inhaled nanoparticles can reach the blood and may reach other sites, such as organs. Depending on its size, nanoparticles may even cross cell membranes.
Scientists have theorized that the effects on living organisms are the same as the effects of the underlying chemicals.
Key factors in the spread of nanoparticles in the body include nanoparticle dose and solubility. Some nanoparticles dissolve easily and It may accumulate in biological systems and persist for a long time.
And some unfriendly biological molecules in living systems may adhere to the surface of nanoparticles and piggyback into bodily tissues and fluids.
Prabir Dutta, Ph.D., of Ohio State University
To determine if a particular nanoparticle is toxic, scientists must be able to trace the path and final destination of these substances in our bodies.
Enter Prabir Dutta, Ph.D. Dutta is a Distinguished University Professor Emeritus of Chemistry and Biochemistry at The Ohio State University. He, along with his colleague Professor Jim Waldman and their students developed methodology to study the path of ingested nanoparticles through our bodies.
“We are proposing a technology that can monitor how these particles are going to different parts of the body if you ingest it,” Dutta said.
Dutta uses fluorescence spectroscopy to study where these particles wind up.
Dutta’s studies focused on nanosilica, which is second to carbon as the most commonly produced nanoparticle material in tonnage.
Silica has an anti-caking property. Among other things, it keeps foods like cake mixes from clumping and being lumpy. The powder flows easily.
“There is concern that if you ingest the nanosilica, that it gets incorporated into different organs,” he said. “The focus of our study was to see how the silica moved across the body.”
Nanosilica is not fluorescent. So he used core-silica shell nanoparticles, using fluorescent Rhodamine 6G and Rhodamine 800, or CdSe/CdS/ZnS quantum dots (semiconductor nanoparticles that fluoresce when exposed to light) as the core. Rhodamine 6G and Rhodamine 800 are fluorescent molecules. These nanoparticles have surface characteristics similar to those of commercial silica particles. He used them to model nanosilica particles to examine how tissue internalized it.
“We would attach a fluorescent dye to the nanoparticle,” he said. We made quantum dots and placed them into the silica nanoparticles. And then we would feed them to animals and see if we can find them in different organs.”
What Dutta found was that the nanoparticles were present in many organs in mice, including the stomach, small intestine, colon, kidney, lung, brain, spleen and liver tissues.
Dutta uses a HORIBA Fluorolog 3 Steady State and Lifetime Modular Spectrofluorometer with an accessory performing TCSPC (Time Correlated Single Photon Counting lifetime measurements) to perform lifetime fluorescence measurements.
TCSPC is a common technique to measure fluorescence decays as a function of time. In principle, it detects single photon events. The Fluorolog 3 with TCSPC correlates the time of arrival to the laser pulse, which his highly customized Fluorolog 3 uses for excitation of the sample.
Dutta also uses fluorescence spectroscopy to understand the formation of zeolitic particles.
“In synthesizing these nanoparticles, we didn’t understand the mechanism of how it’s formed,” he said. “And that's where in-situ fluorescence spectroscopy came in handy, and we could monitor the synthetic reactions going on in a flask in a microwave oven in real-time. That helped us define methodology to essentially develop synthesis procedures for these nanoparticles, which are now the basis of a new technology.”
In fact, he launched a start-up business with Bo Wang, Ph.D., to capitalize on that technology.
Engineers use nanomaterials made with zinc or metallics, like silver and copper as antimicrobials. These substances reduce the presence of microbes, such as bacteria and mold. They apply the antimicrobials to food preparation surfaces, including things like cutting boards, so bacteria will not grow on them.
Dutta said the zinc oxide or metallics nanoparticles can also be applied in a spray format to clothing.
“I'm not compromising the properties of the polymer of the textile using these metal-loaded nanozeolites (specific porous crystalline minerals),” he said. “I'm giving the polymers and textiles added anti-microbial protection. That's the advantage of this whole area of nanotechnology. Because things are small, they don't interfere with the macroscopic real product that you're interested in, and yet they still provide interesting and novel properties.”
Dutta based his start-up company, ZeoVation, on these antimicrobial nanoparticles.
He describes the process as smart particle technology that makes products cleaner, safer and more effective by preventing problems and damaging effects before they start.
Dutta developed compounds for a number of industries, including the coatings, healthcare, polymers and plastics, textiles and sun protection markets.
Although research is still scarce, with the decrease in size, there is an increase in the inherent toxicity of nanoparticles. Inhaled particles, like through air pollution, can damage respiratory systems. And materials which by themselves are not very harmful could be toxic if they are inhaled in the form of nanoparticles.
However, information on the behavior of nanoparticles in the body is still minimal and often conflicting.
The U.S. Food and Drug Administration does not consider nanoparticles either totally safe or harmful for human use.
Dutta, through his own research observed that ingested nanosilica particles are not necessarily toxic.
“We have done a lot of other studies, and we find no toxicity in vitro at the levels that people ingest these things,” he said. “Really there is no concern for nanosilica.”
As for other nanoparticles, the jury is still out.
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