Category Archives: News

Dilpreet Singh won the New Investigator Award at the National Nanotechnology Initiative international QEEN conference

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From left: Dr. Michael A. Meador, Director, National Nanotechnology Coordination Office (NNCO), Dilpreet Singh, Award winner, Dr. Treye Thomas, Leader, Chemical Hazards Program, U.S. Consumer Product Safety Commission.

Dilpreet Singh, a second year doctoral student in Prof. Philip Demokritou’s Lab for Environmental Health Nanoscience at the Center for Nanotechnology and Nanotoxicology at the Harvard T.H. Chan School of Public Health, has won the New Investigator Award at the InternationalQEEN (Quantifying Exposure to Engineered Nanomaterials from Manufactured Products) conference sponsored by the Consumer Product Safety Commission (CPSC) in collaboration with the NNI (National Nanotechnology Initiative) at Washington D.C. from July 7-8, 2015.

Dilpreet’s poster presentation entitled “Nano-waste: Environmental health and safety (EHS) implications during thermal degradation/incineration of nano-enabled products at their end-of-life” was the winner in the New Investigators Competition. The two-day conference was attended by 150 experts from academia, federal representatives, and industries and focused primarily on understanding the exposure science related to engineered nanomaterials. Dilpreet’s research is part of an NSF funded research project which focuses on the environmental health and safety implications of Nano-enabled products at their end of life during thermal decomposition and incineration.

Dilpreet Singh explains the concept of his research at the National Nanotechnology Initiative international QEEN conference.

Dilpreet Singh explains the concept of his research to Dr. Chuck Geraci.

“By understanding the science behind potential release and exposure of engineered nanomaterials across the lifecycle of a nano-enabled product, one can move forward in the direction of sustainable nanotechnology development by coming up with novel product designs that would minimize potential exposure, and hence risk,” said Singh in an interview with Dr. Chuck Geraci, Associate Director for Nanotechnology at the National Institute for Occupational Safety and Health (NIOSH).

Nanotechnology to the Rescue: Using Engineered Water Nanostructures (EWNS) to inactivate Foodborne Microorganisms

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The burden of foodborne diseases worldwide is huge, with serious economic and public health consequences. The U.S. Department of Agriculture’s (USDA’s) Economic Research Service reported in 2014 that foodborne illnesses are costing the economy more than $15.6 billion and about 53,245 Americans visit the hospital annually due to foodborne illnesses. The food industry is in search of effective intervention methods that can be applied form “farm to fork” to ensure the safety of the food chain and be consumer and environment friendly at the same time.

Researchers at the Center for Nanotechnology and Nanotoxicology of the Harvard T. Chan School of Public Health are currently exploring the effectiveness of a nanotechnology based, chemical free, intervention method for the inactivation of foodborne and spoilage microorganisms on fresh produce and on food production surfaces. This method utilizes Engineered Water Nanostructures (EWNS) generated by electrospraying of water. EWNS possess unique properties; they are 25 nm in diameter, remain airborne in indoor conditions for hours, contain Reactive Oxygen Species (ROS), have very strong surface charge (on average 10e/structure) and have the ability to interact and inactivate pathogens by destroying their membrane.

In a study funded by the USDA and just published this week in the premier Environmental Science and Technology journal, the efficacy of these tiny water nanodroplets, in inactivating representative foodborne pathogens such as Escherichia coli, Salmonella enterica and Listeria innocua, on stainless steel surfaces and on tomatoes, was assessed showing significant log reductions in inactivation of select food pathogens. These promising results could open up the gateway for further exploration into the dynamics of this method in the battle against foodborne disease. More importantly this novel, chemical-free, cost effective and environmentally friendly intervention method holds great potential for development and application in the food industry, as a ‘green’ alternative to existing inactivation methods.

Dr. Philip Demokritou, Associate professor at Department of Environmental Health and lead author of the study mentioned, “Nanotechnology can bring on the table new useful intervention approaches that can be used in the battle against food borne diseases. Using water in its engineered nanoscale form can be a ‘game changer’, cost effective approach that can be easily deployed at various intervention points across the ‘farm to fork’ line”.

Drs. Georgios Pyrgiotakis and Pallavi Vedantam, post-doctoral research fellows in the Department of Environmental Health who are currently further exploring the prospects of this novel high throughput system believe that this technology could not only significantly decrease the microbial load on the fresh produce but also extend shelf life of produce and reduce the number of cases of foodborne illnesses on consumption. The Center for Disease Control (CDC) has estimated 48 million such cases each year in the United States alone, which include 3,000 deaths. Hence, this method could potentially landscape the preventable public health challenge of foodborne infections and craft best ways forward. Prof. Mitchell and his team at SEAS also collaborated in this study.

EST publication can be accessed here. For more information on nano related research at Harvard T.H. Chan School of Public Health please visit our website at


Printer Emitted Particles: Are they safe?

Engineered nanomaterials (ENMs) incorporated into toner formulations of toner used in every day laser printers. During the print jobs it is likely that the particles can be released in the air.

Recently, our group developed a lab based Printer Exposure Generation System that allows the generation and sampling of airborne PEPs for subsequent physicochemical, morphological and toxicological analyses. This platform was used to evaluate PM emission profiles from 11 laser printers currently on the market. It was shown that the particle number concentration of PEPs varied across different printer models/manufacturers and reached as high as 1.3 million particles/cm3 and with modal diameters <200 nm. The detailed assessment of both toners and PEPs confirmed not only the presence of nanoscale materials in the airborne state but also their complex chemistries, which include elemental and organic carbon and inorganic compounds such as metals and metal oxides. It has been now confirmed that toners are classified as nano-enabled products. Additionally, we have performed in-depth toxicological analysis evaluating the effects of exposure to PEPs using physiologically relevant cell lines in both mono- and co-culture experimental systems. We have shown that PEPs caused significant cytotoxicity, membrane integrity damage, reactive oxygen species (ROS) production, pro-inflammatory cytokine release, angiogenesis, actin remodeling, gap cell junctions and epigenetic changes in cells at doses comparable to those from real world exposure scenarios representative of inhalation exposures in the range of 1-200 hours. We may conclude that laser printer-emitted engineered nanoparticles can be deleterious to lung cells and may cause persistent genetic modifications that could translate to pulmonary disorders.


  1. Pirela SV, Pyrgiotakis G, Bello D, Thomas T, Castranova V, Demokritou P. 2014a. Development and characterization of an exposure platform suitable for physico-chemical, morphological and toxicological characterization of printer-emitted particles (peps). Inhal Toxicol 26:400-408.
  2. Pirela SV, Sotiriou GA, Bello D, Shafer M, Bunker KL, Castranova V, et al. 2014b. Consumer exposures to laser printer-emitted engineered nanoparticles: A case study of life-cycle implications from nano-enabled products. Nanotoxicology:1-9.
  3. Pirela SV, Miousse IR, Lu X, Castranova V, Thomas T, Qian Y, et al. 2015. Laser printer-emitted engineered nanoparticles lead to cytotoxicity, inflammation and changes in dna methylation in human cells. Environmental health perspectives.
  4. Sisler JD, Pirela SV, Friend S, Farcas M, Schwegler-Berry D, Shvedova A, et al. 2014. Small airway epithelial cells exposure to printer-emitted engineered nanoparticles induces cellular effects on human microvascular endothelial cells in an alveolar-capillary co-culture model. Nanotoxicology:1-11.

Nano State

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The NanoCenter researchers , Phil Demokritou, Joseph Brain and Georgios Pyrgiotakis were featured in a four page special story at the Harvard School of Public Health magazine. They discussed the impact of nano in the society and the importance of the center research. Further more they talked about the Engineered Water Nanostructures a novel, chemical free method developed in the Center that is promising for the air inactivation of pathogenes.

You can read the whole story here.

Harvard School of Public Health researchers develop technique to measure the quantity of engineered nanomaterials delivered to cells

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Press Release in pdf

Boston, MA— Thousands of consumer products containing engineered nanoparticles — microscopic particles found in everyday items from cosmetics and clothing to building materials — enter the market every year. Concerns about possible environmental health and safety issues of these nano-enabled products continue to grow with scientists struggling to come up with fast, cheap, and easy-to-use cellular screening systems to determine possible hazards of vast libraries of engineered nanomaterials. However, determining how much exposure to engineered nanoparticles could be unsafe for humans requires precise knowledge of the amount (dose) of nanomaterials interacting with cells and tissues such as lungs and skin.

With chemicals, this is easy to do but when it comes to nanoparticles suspended in physiological media, this is not trivial. Engineered nanoparticles in biological media interact with serum proteins and form larger agglomerates which alter both their so called effective density and active surface area and ultimately define their delivery to cell dose and bio-interactions. This behavior has tremendous implications not only in measuring the exact amount of nanomaterials interacting with cells and tissue but also in defining hazard rankings of various engineered nanomaterials (ENMs). As a result, thousands of published cellular screening assays are difficult to interpret and use for risk assessment purposes.

Scientists at the Center for Nanotechnology and Nanotoxicology at Harvard School of Public Health (HSPH) have discovered a fast, simple, and inexpensive method to measure the effective density of engineered nanoparticles in physiological fluids, thereby making it possible to accurately determine the amount of nanomaterials that come into contact with cells and tissue in culture.

The method, referred to as the Volumetric Centrifugation Method (VCM), will be published in the March 28, 2014 Nature Communications.

The new discovery will have a major impact on the hazard assessment of engineered nanoparticles, enabling risk assessors to perform accurate hazard rankings of nanomaterials using cellular systems. Furthermore, by measuring the composition of nanomaterial agglomerates in physiologic fluids, it will allow scientists to design more effective nano-based drug delivery systems for nanomedicine applications.

“The biggest challenge we have in assessing possible health effects associated with nano exposures is deciding when something is hazardous and when it is not, based on the dose level. At low levels, the risks are probably miniscule,” said senior author Philip Demokritou, associate professor of aerosol physics in the Department of Environmental Health at HSPH. “The question is: At what dose level does nano-exposure become problematic? The same question applies to nano-based drugs when we test their efficiency using cellular systems. How much of the administered nano-drug will come in contact with cells and tissue? This will determine the effective dose needed for a given cellular response,” Demokritou said.

Federal regulatory agencies do not require manufacturers to test engineered nanoparticles, if the original form of the bulk material has already been shown to be safe. However, there is evidence that some of these materials could be more harmful in the nanoscale — a scale at which materials may penetrate cells and bypass biological barriers more easily and exhibit unique physical, chemical, and biological properties compared to larger size particles. Nanotoxicologists are struggling to develop fast and cheap toxicological screening cellular assays to cope with the influx of vast forms of engineered nanomaterials and avoid laborious and expensive animal testing. However, this effort has been held back due to the lack of a simple-to-use, fast, method to measure the dose-response relationships and possible toxicological implications. While biological responses are fairly easy to measure, scientists are struggling to develop a fast method to assess the exact amount or dose of nanomaterials coming in contact with cells in biological media.

“Dosimetric considerations are too complicated to consider in nano-bio assessments, but too important to ignore,” Demokritou said. “Comparisons of biological responses to nano-exposures usually rely on guesstimates based on properties measured in the dry powder form (e.g., mass, surface area, and density), without taking into account particle-particle and particle-fluid interactions in biological media. When suspended in fluids, nanoparticles typically form agglomerates that include large amounts of the suspending fluid, and that therefore have effective densities much lower than that of dry material. This greatly influences the particle delivery to cells, and reduces the surface area available for interactions with cells,” said Glen DeLoid, research associate in the Department of Environmental Health, one of the two lead authors of the study. “The VCM method will help nanobiologists and regulators to resolve conflicting in vitro cellular toxicity data that have been reported in the literature for various nanomaterials. These disparities likely result from lack of or inaccurate dosimetric considerations in nano-bio interactions in a cellular screening system,” said Joel Cohen, doctoral student at HSPH and one of the two lead authors of the study.

Wolfgang Kreyling, a nanotoxicologist at the German Research Center for Environmental Health who was not involved in the study, says this method should help toxicologists to understand the nano-bio interactions and address possible nano hazards for the vast libraries of engineered nanoparticles (ENPs) currently in use.

“The paper by DeLoid et al in Nature Communications is a major achievement which offers a solution to solve the pending issues of the apparent ENM density and an easy way to determine the latter by the application of the volumetric centrifugation method. Hence, this paper provides a versatile concept easy to achieve which allows for a rather precise estimate of ENM dosimetry to in vitro cell cultures which hopefully will improve the power of toxicological studies using in vitro cell cultures when comparing to in vivo studies. In this case this would be a major contribution in aiming to reduce in vivo experimental animal work,” Kreyling said.

Other authors of the study include Georgios Pyrgiotakis, research fellow at HSPH, Liying Rojanasakul, and Raymond Derk from the National Institute for Occupational Safety and Health, and Wendel Wohlleben from BASF, Germany.

This research project was supported by NIEHS grant (ES-000002), NSF grant (ID 1235806) and the Center for Nanotechnology and Nanotoxicology at HSPH. This work was performed in part at the Harvard Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Infrastructure Network (NNIN), which is supported by the National Science Foundation under NSF award number ECS-0335765.

“Estimating the effective density of engineered nanomaterials for in vitro dosimetry,” Glen DeLoid, Joel M. Cohen, Tom Darrah, Raymond Derk, Liying Rojanasakul, Georgios Pyrgiotakis, Wendel Wohlleben, and Philip Demokritou, Nature Communications, online March 28, 2014.

First High Throughput Genotox Assay

Protocol for the high throughput Comet Assay. (A) Assembly of macrowell comet array. Agarose gel with microwells is sandwiched between a glass substrate and a bottomless 96-well plate and sealed with mechanical force. Approximately 300 arrayed microwells comprise the bottom of each macrowell. (B) Preparation of the nanoparticle suspension according to the protocol by Cohen at al. (C) Protocol for exposing the cells to the nanoparticles. (D) Loading of the exposed cell samples in the macrowells and running the microwell assay.

Protocol for the high throughput Comet Assay. (A) Assembly of macrowell comet array. Agarose gel with microwells is sandwiched between a glass substrate and a bottomless 96-well plate and sealed with mechanical force. Approximately 300 arrayed microwells comprise the bottom of each macrowell. (B) Preparation of the nanoparticle suspension according to the protocol by Cohen at al. (C) Protocol for exposing the cells to the nanoparticles. (D) Loading of the exposed cell samples in the macrowells and running the microwell assay.

Nanomaterials are part of daily life. Although there is a wide range of methods to evaluate their potential toxic effects, there is no way to evaluate gene damage.

Scientists at Harvard University in the School of Public Health in collaboration with the research Group of Bevin P. Engelward at MIT, have developed a screening assay to detect the genotoxic potential of nanomaterials. Metal oxide nanoparticles in biological systems can generate reactive oxygen species, which can overwhelm innate antioxidant defenses and cause oxidative stress. Oxidative stress, among other factors, has been associated with DNA damage and mutations, precursors to cancer. As more and more commercial products contain nanomaterials consisting of metal oxides such as titanium dioxide and zinc oxide, screening assays such as these are crucial to reducing potential health hazards. Christa Watson, postdoctoral research fellow at HSPH, suggests that accurate toxicity assessments of nanomaterials before they are incorporated into consumer products can help us prevent similar consequences that we are currently facing from asbestos exposures such as mesothelioma. Current efforts are ongoing to understand the novel toxicities nanomaterials may pose on public safety. This research was recently published in ACS Nano February 14, 2014 DOI: 10.1021/nn404871p

Research at the HSPH NanoCenter revolutionize sunscreens!

ZnO is a widely used material in cosmetics and food applications. The ions however, that are leaching have been linked to potential adverse effects. In our center we developed a safer formulation concept to mitigate toxicity by encapsulating the materials in a thin layer of Silica.

ZnO is a widely used material in cosmetics and food applications. The ions however, that are leaching have been linked to potential adverse effects. In our center we developed a safer formulation concept to mitigate toxicity by encapsulating the materials in a thin layer of Silica.

One of the main constituents of sunscreen is the ZnO particles. ZnO nanoparticles are sought out for UV-filter applications thanks to their inherent optoelectronic properties and are, therefore, broadly used today in cosmetics and polymers. Preliminary toxicological data, however, point out that they can induce significant DNA damage and genotoxicity due to their Zn2+ ion leaching. It has become important for the nanotechnology industry, to devise scalable, safer-by-design approaches to minimize the ZnO nanoparticle dissolution and toxicity without altering their desired optoelectronic properties.

G. Sotiriou the lead author of the paper.

In their work, the researchers demonstrated a safer-by-design approach for ZnO nanorods using a scalable flame aerosol process. This technology allows for controlled synthesis of high-purity ZnO nanorods with highly crystalline core and a nanothin amorphous silica shell that improves their biocompatibility. The as-prepared nanorods exhibit high transparency in the visible range, but strong absorption in the UV rendering them suitable for use in sunscreens and polymers. Furthermore, it is demonstrated that the hermetic silica coating does not alter the desired optoelectronic properties of the core ZnO nanorods while their DNA damage potential has been 3-fold decreased.

You can read more at the Chemistry World news article or, directly the paper.