Environmental Science: Nano Blog

Dr. Xing Xie is an assistant professor and the Carlton S. Wilder Junior Professor in the School of Civil and Environmental Engineering at Georgia Institute of Technology. Prior to joining Georgia Tech, he was a postdoc at California Institute of Technology in 2014-2017. Dr. Xie received his B.S. (2006) and M.S. (2008) degrees in Environmental Science & Engineering from Tsinghua. He received his Ph.D. degree (2014) in Civil & Environmental Engineering and his second M.S. degree (2012) in Materials Science & Engineering from Stanford University. He has been applying environmental biotechnology and materials science to address challenges at the nexus of water and energy, such as developing low-cost water treatment technologies that improve global access to safe drinking water. He has published 50 peer-reviewed articles in leading journals, including PNAS, Energy & Environmental Science, and Nature Communications. His work has been cited over 5000 times with an H-index of 23. Dr. Xie is a recipient of the NSF CAREER award in 2019.

Read Xing Xie ’s Emerging Investigator Series article “Locally Enhanced Electric Field Treatment (LEEFT) with Nanowire Modified Electrodes for Water Disinfection in Pipes” and read more about him in the interview below:

Your recent Emerging Investigator Series paper focuses on Emerging investigator series: Locally Enhanced Electric Field Treatment (LEEFT) with Nanowire Modified Electrodes for Water Disinfection in Pipes. How has your research evolved from your first article to this most recent article?

The LEEFT technology for water disinfection was first demonstrated in the early 2010s at Stanford, although it was not given the name “LEEFT” until recently. As a Ph.D. student, I was involved in the development of the first-generation LEEFT devices. When I started my own lab at Georgia Tech in 2017, I believe the LEEFT technology can be transformative. Potentially, it will change our current water treatment strategies and infrastructure in many places at different scales. While, of course, before the practical application of this technology, there are still many challenges to be addressed. We are interested in all aspects of research on this technology. Currently, we mainly focus on mechanism study, electrode development, and system design. The work described in this most recent article is part of our effort on the system design of the LEEFT technology.

What aspect of your work are you most excited about at the moment?

I am excited about all the aspects of our work on the LEEFT technology.

In your opinion, what are the most important questions to be asked/answered in this field of research?

The existing LEEFT devices are like black boxes: Efficient microbial inactivation has been achieved when water flows through the device, but the detailed mechanism is not fully understood. Irreversible electroporation is believed to be the primary antimicrobial mechanism during the LEEFT. Electroporation is a physical process that should not result in any by-products. However, it is not clear whether irreversible electroporation can be the sole mechanism to achieve high inactivation efficiency. All the previous LEEFT experiments utilized electrodes that would release Ag or Cu ions. Even though the bulk Cu concentration in the effluent has been reduced to less than 5 µg/L, it is possible that such a small amount of Cu still contributes to the microbial inactivation. In addition, some other antimicrobial mechanisms may exist. Therefore, we are studying the mechanisms using a lab-on-a-chip LEEFT platform, which allows the in-situ observation of the microbes under a microscope during the LEEFT.

What do you find most challenging about your research?

One of the biggest challenges for the further development of the LEEFT technology is to obtain durable electrodes through a reliable and scalable fabrication method. When LEEFT devices can operate steadily for a long enough period, researchers around the world will be able to study the LEEFT from different aspects.

In which upcoming conferences or events may our readers meet you?

I plan to attend the Gordon Research Conference on Environmental Sciences: Water and the Sustainable Nanotechnology Organization (SNO) Conference in 2020.

How do you spend your spare time?

I would like to spend my spare time with my family and friends playing board games or traveling to national parks. I have been to more than half of the 61 national parks in the US.

Which profession would you choose if you were not a scientist?

Maybe a chef. I make nanomaterials for environmental applications. Cooking and material synthesis have so many similarities: you need to have the right ingredients, use the right hardware, follow the right procedure, and control the right condition in each step.  While I am not always successful in making the desired nanomaterials, I usually quite enjoy the dishes I cook.

Can you share one piece of career-related advice or wisdom with other early career scientists?

Work on something unique, so you will be a leader rather than a follower.

Dr. Matteo Minghetti is an Assistant Professor in the Department of Integrative Biology at Oklahoma State University (OSU).  Dr. Minghetti received his Ph.D. in Ecotoxicology from the University of Stirling, UK in 2009. His diverse postdoctoral work includes projects on the transcriptional regulation of lipid metabolism in Atlantic Salmon (University of Stirling), the use of primary gill cultures for environmental biomonitoring (Kings College London), and the mechanisms of toxicity of metal nanoparticles in intestinal fish cells (Eawag – The Swiss Federal Institute of Aquatic Science and Technology). Dr. Minghetti is a recipient of a Marie Curie Fellowship (2012) and a National Science Foundation award (2018). His research interests lie at the interface between disciplines integrating analytical chemistry, molecular biology and physiology. The Minghetti Lab at OSU focuses on understanding physiological processes such as essential trace element homeostasis and developing tools for environmental biomonitoring.

Read Matteo Minghetti’s Emerging Investigator Series article “Linking Chemical Transformations of Silver and Silver Nanoparticles in the Extracellular and Intracellular Environment to their Bio-reactivity” and read more about him in the interview below:

Your recent Emerging Investigator Series paper focuses on Linking Chemical Transformations of Silver and Silver Nanoparticles in the Extracellular and Intracellular Environment to their Bio-reactivity. How has your research evolved from your first article to this most recent article?

Mechanisms of cellular metal homeostasis and handling have been the main focus of my research so far. During my PhD, I discovered that fish, similarly to humans, take up and excrete copper using specific copper transport proteins (CBP 2008, 147(4):459-9; Aquat. Toxicol. 2010, 97(1):23-33). After my PhD, I began to consider the environmental factors that affect metal bioavailability such us metal complexation with ligands present in the extracellular medium and competition with other cations.  To examine these concepts, I began to use in vitro models of the gill and intestinal epithelium.   This research revealed that extracellular metal speciation is linked to metal bioavailability and toxicity, but also that intracellular accumulation is not always linked with bio-reactivity (i.e. metallothionein gene expression) (Nanotoxicology 2016, 10(10):1526-1534). It became clear to me, therefore, that establishing the link between extracellular and intracellular metal speciation was necessary to fully understand the environmental conditions that potentially lead to organismal metal bioavailability, bioreactivity and toxicity. Intracellular metal speciation detection requires the use of X-ray spectroscopy, a technique that has been used extensively in physics, chemistry and geology but its use in biology is relatively new. In order to access this technique, I started a collaboration with Professor Jeffrey Catalano (Washington University in St. Louis), a geochemist and expert in synchrotron-based X-ray spectroscopic methods. I believe that studies at the interface between disciplines lead to potentially transformative discoveries.

What aspect of your work are you most excited about at the moment?

I am particularly excited about my recent work with X-ray florescence microscopy, which I use to visualize intracellular endogenous elements in cells. After many years of indirectly measuring the effect of metals and nano-metals in cells through gene and protein expression, I have found it really fascinating to be able to actually visualize clusters of metal ions in the cell with my own eyes.

In your opinion, what are the most important questions to be asked/answered in this field of research?

Once a metal or metal nanoparticle enters a cell, its intracellular fate over time will determine cellular effects. For instance, a particle might remain unaltered and non-bioreactive in the cell or dissolve rapidly and induce a sharp biological response. While important discoveries have been made in the nanotoxicology field with regard to factors influencing nanoparticle uptake (e.g. particle size, coating and corona protein interactions, etc.), our understanding of the factors influencing intracellular fate and transformation of nanoparticles is still poorly understood.

What do you find most challenging about your research?

Although fish cell lines have proven to be a useful tool for toxicological studies, they lack the complexity of the “real” tissue. A new generation of in vitro models is necessary to mimic more closely the responses of the whole organism. Such new systems will need to include multiple cell types in a substrate that mimics the tissue microenvironment. The main challenge is that developing such new in vitro models requires a multi-disciplinary approach involving collaborations between biologists and engineers.

In which upcoming conferences or events may our readers meet you?

I will attend the SETAC North America meeting, which is in Toronto this year. I am excited to co-chair a session on Nanotoxicology at this meeting and I would welcome colleagues to participate in this session and discuss new discoveries in this exciting field.

How do you spend your spare time?

I love spending time outdoors. Since moving to the U.S., my family and I have fallen in love with the National Parks’ system and we try to visit as many as possible every year. I also enjoy cycling with my local cycling club. It is a great way to relax!

Which profession would you choose if you were not a scientist?

I love driving and visiting new and exciting places.  Joking with my wife, I always say I would have been a good ice road trucker!

Can you share one piece of career-related advice or wisdom with other early career scientists?

As I’ve mentioned, I firmly believe that new discoveries lie at the interface between disciplines. So, I would encourage early career scientists to collaborate with researchers from other fields of science. I have always found it very informative and useful to attend seminars and meetings outside of my discipline. Other than that, follow your personal interest and passion and try not to be too influenced by current trends.

Dr. Kyle Doudrick is an Assistant Professor in the Department of Civil & Environmental Engineering & Earth Sciences at the University of Notre Dame (UND). Dr. Doudrick received his Ph.D. (2013) at Arizona State University where he investigated the use of photocatalysts for treating nitrate, a ubiquitous drinking water contaminant. His research group at UND seeks to solve critical problems in environmental engineering using nanotechnology, with a focus on developing physical-chemical technologies for treating water contaminants and understanding the fate and transport of nanoparticles in streams. Dr. Doudrick is a recipient of the National Science Foundation CAREER award and a 2019 Fulbright Scholar. He also has a passion for improving environmental engineering education using virtual reality (VR), including the development of 360 immersive tours. You can view his VR drinking water treatment plant tour on YouTube with or without a headset (https://www.youtube.com/watch?v=zRFBVFBZ1jI).

Read Kyle Doudrick’s Emerging Investigator Series article “protein adsorption and transformation on catalytic and food-grade TiO2 nanoparticles in the presence of dissolved organic carbon” and read more about him in the interview below:

Your recent Emerging Investigator Series paper focuses on Protein Adsorption and Transformation on Catalytic and Food-Grade. How has your research evolved from your first article to this most recent article?

I first started working with food-grade titanium dioxide during my Ph.D., where we characterized the surface chemistry and its effect on cells (Environmental Science & Technology 48 (11), 6391-6400; Cell Biology and Toxicology 30 (3), 169-188; PloS One 11 (10), e0164712). What stood out broadly from these studies was the difference between the titanium dioxide in our food and pharmaceutical products compared to the “chemical” or “catalytic” grade titanium dioxide that is often used in toxicity and transport studies. The food-grade titanium dioxide is present day – we are all ingesting it – but there have been few studies on the adverse effects. This includes studies about the adsorption of proteins to nanoparticles, which we understand to be critical for determining bioactivity. So, naturally, the first question that came to my mind was: does the protein adsorption behavior differ when we use more realistic nanoparticles like the food-grade materials? The work we present here confirms that the protein formation is quite different for the two types. Further, we provide evidence that the protein adsorption behavior changes if the nanoparticle is first exposed to dissolved organic carbon (e.g., from a stream), and this behavior can be quite different depending on the nanoparticle. I think these findings have some broad implications that should make us question whether we are choosing the right nanoparticles/scenarios in our experiments.

What aspect of your work are you most excited about at the moment?

We currently have a project in which we are investigating the transport of nanoparticles in realistic streams. We have a unique site at the University of Notre Dame called the Linked Experimental Ecosystem Facility (ND-LEEF). It has four hydraulically identical streams lined with varying media types, and we are adding nanoparticles to study the transport behavior under different conditions. In collaboration with Prof. Diogo Bolster, we hope to use this data to create a model that will be able to predict the transport better than what is currently available. I think these types of studies are an important step to simplifying the complexity that comes with investigating nanoparticles in real systems. We have already observed some interesting results and the paper should be out soon!

In your opinion, what are the most important questions to be asked/answered in this field of research?

As I eluded to above, I think figuring out how nanoparticles behave in real systems will be a critical and challenging question to answer. The myriad combinations of nanoparticle physical-chemical properties and environmental condition/scenarios presents us with an almost insurmountable challenge of creating theoretical based predictions (e.g., linking surface charge to transport behavior). These approaches may be good for simplified lab experiments, but they don’t scale well to realistic systems. So, when nanoparticles enter the environment after being released from, e.g., a food, do they eventually just become like any other metal oxide/organic carbon coated with organic matter or adsorbed to minerals or do they behave differently?

What do you find most challenging about your research?

One of the biggest challenges in studying nanoparticles in complex, realistic environments is the analytics. If you are interested in something like silver, then you must deal with its dissolution and/or transformation, and if you are working with carbon nanotubes then you are fighting against the high carbonaceous background concentrations. Our studies are only as good as our detection methods, and I think this has become a critical area that is not getting enough attention, especially if we want to move beyond lab-scale experiments. These limitations force us to be creative with experimental design by selecting certain nanoparticles and using model field sites, but that makes it difficult to achieve truly realistic experiments (e.g., tracking nanoparticle movement in Lake Michigan or in a large river).

In which upcoming conferences or events may our readers meet you?

I will be at two upcoming conferences: the American Chemical Society in August and the Sustainable Nanotechnology Organization (SNO) in November, both in San Diego. I highly recommend the SNO conference to this audience as it is a great platform to discuss our research amongst nano-minded people.

How do you spend your spare time?

I have numerous hobbies, but these days I rarely get to partake. When I do find some free time, I enjoy spending it with my family and friends, traveling, playing volleyball, reading, hiking, gardening, photography, and playing musical instruments poorly.

Which profession would you choose if you were not a scientist?

A question many tenure track faculty seem to ask themselves around year five. I do love research and teaching, but I could see myself enjoying many other professions. Imaging what pathways you might have taken is fun and I’ve often thought I could have been a good tour guide or CIA analyst. But, I think most of all, I would like to have a sustainable farm somewhere with lush, rolling hills where I could write fantasy or science fiction stories when I’m not tending to my animals (and bees) and crops. Who knows, maybe one day I will retire and get to say I did both!

Can you share one piece of career-related advice or wisdom with other early career scientists?

How about one big congregated piece of advice? I think many young researchers stress about hitting the ground running so they can carve out their “niche” and work on the next big thing. Instead, I think when starting out you just should focus on a topic that you are passionate about and become good at that. Being a young researcher/professor is challenging and I think if you concentrate on becoming a better scientist/teacher, mentor, and writer, then the rest will fall into place as you gain more experience. And there are many books available that can help you along the way – Boice is a good place to start, and don’t feel guilty about taking some time out of research or writing to read it. Definitely make time for your family and friends and don’t get into a habit of working weekends (easier said than done). Don’t take bad reviews to heart, and in return be respectful and constructive when you write proposal and paper reviews. Most of all, have fun.