How can tiny holes detect DNA and generate electricity?
Nanotechnology is transforming the world around us. At the University of Illinois Urbana-Champaign in the US, Professor Jean-Pierre Leburton is studying how nanopores can detect DNA or proteins and generate electricity, providing benefits for medicine and clean energy.
Talk like a nanoscientist
Base pairs — the molecular building blocks of DNA
Biomolecule — an organic (carbon-containing) molecule produced by an organism
Diffusion — particle movement from a region of high concentration to a region of low concentration
Electrolytic solution — a solution containing dissolved salt (i.e., ions) that can conduct electricity
Methyl complex — a molecular component containing one carbon and three hydrogen atoms (CH3)
Nanopore — a hole with a diameter of a few nanometres
Semiconductor — a material that can have the properties of a conductor or insulator, depending on physical conditions
Solid-state film — a very thin artificially created membrane (only a few atoms thick)
Nanopores are tiny holes. As a nanometre (nm) is a million times smaller than a millimetre (mm), these holes are very small indeed – they exist where a few atoms are missing. In nature, they are present in our cell membranes where they allow substances to pass into and out of our cells. Scientists can also create nanopores in artificial films which can be used for a range of different purposes, from biomolecule (e.g., DNA) detection to electricity generation.
“Nanopores are very small holes (0.6 nm – 6 nm diameter) dug in a very thin membrane (only a few atoms thick),” explains Professor Jean-Pierre Leburton from the Micro and Nanotechnology Laboratory at the University of Illinois Urbana-Champaign. Scientists create artificial nanopores in solid-state films made from silicon or graphene, and Jean-Pierre is using computer simulations to explore the potential of these nanopores for different applications.
Using nanopores to detect biomolecules
Nanopores are so small that only one only one molecule can pass through them at a time. As the molecule moves through the pore, scientists can identify its atomic components. This makes nanopores ideal for detecting biomolecules.
Biomolecules are mixed into an electrolytic solution (water containing dissolved salts) so that the properties of this solution force the biomolecules to pass through the nanopores dug in the solid-state film. “If the molecules are charged, scientists can use electric fields to thread them through a nanopore,” says Jean- Pierre. “Scientists can also use the solid-state nanopore film to separate solutions with different salt concentrations to drag the biomolecules through the nanopores by diffusion.”
The next challenge is identifying the biomolecules as they pass through the nanopores. “The initial detection technique consisted of monitoring the current of ions flowing through the pore,” says Jean-Pierre. “The current drops when the biomolecule is in the pore as it blocks the flow of ions.” More recently, a new detection technique has emerged that uses the electrical properties of the solid-state film itself. An electric current is sent along the solid-state film; as the biomolecules pass through the nanopores in the film, they perturb this current. The measurement of the magnitude of the perturbations can be used to determine the components of the biomolecules.
Jean-Pierre and his team are studying this new electric current sensing method to understand when it might provide benefits over the traditional ionic current blocking method for biomolecule detection.
Using nanopores for DNA sequencing
As the molecule of life, DNA is a prime example of a complex biomolecule that is the focus of many biomedical applications of nanopores. Indeed, nanopore biomolecule detection techniques are sensitive enough to identify the exact sequence of molecular base pairs on DNA strands when the amplitude of the ionic or electric current changes as each base pair passes through the pore. In this scenario, nanopores have huge potential for DNA sequencing as they provide a much quicker and cheaper method compared to traditional biochemical DNA sequencing techniques.
Beyond simply sequencing the order of DNA base pairs, when DNA strands pass through nanopores scientists can also identify molecules attached to the DNA, such as methyl complexes. If an organism’s DNA contains too many or too few methyl complexes, the effects can be devastating. “These methyl modifications can be lethal as they are associated with various types of cancers,” says Jean-Pierre. “We anticipated that nanopores using the new electric current sensing technique can detect these methyl complexes at a higher sensitivity than the typical ionic current sensing technique.” Jean-Pierre uses computer simulations that model the theoretical properties of nanopores and their solid-state films to investigate their abilities to sequence DNA and detect methyl complexes. “Our theoretical investigation of nanopores has led to numerous predictions that have since been confirmed experimentally,” he says.
Using nanopores to generate electricity
Reference
https://doi.org/10.33424/FUTURUM595
Another key application of nanopores is electricity generation, a hot topic given the global challenge of transitioning to clean energy to mitigate the emission of greenhouse gases. If an electrically active solid-state nanopore film, such as a semiconductor material, is placed between solutions with different salt concentrations, then the difference in concentrations will cause ions to flow through the nanopores by diffusion. This flow of ions will generate electricity in the solid-state film. “In this way, the nanopore and its surrounding material can act as an electrical battery which delivers electric power generated by salted water,” explains Jean-Pierre. “This means nanopores can provide a cheap and non-polluting source of energy from seawater, known as ‘blue energy’.”
Harnessing this technique could provide a major contribution to the clean energy revolution. While it remains to be seen whether nanopore blue energy generation can be efficiently scaled up, given the challenges in creating the super-thin solid-state nanopore films involved, it opens new technological possibilities for reliable electricity generation. Studying these methods further – both through computational modelling, like Jean-Pierre does, and experimental research – might help the world become a more sustainable place.
Professor Jean-Pierre Leburton
Micro and Nanotechnology Laboratory, Department of Electrical and Computer Engineering, University of Illinois Urbana- Champaign, USA
Field of research: Computational nanotechnology
Research project: Using nanopores for biomolecule detection and electricity generation
About nanotechnology
Nanotechnology is the field of science and engineering that involves the study and manipulation of matter at the nanoscale. The field has seen a boom over the last few decades due to the development of the sophisticated instruments and methodologies that enable such fine-scale observation and manipulation. “The field of nanotechnology is immense, with many diverse applications across scientific fields with broad societal impacts,” says Jean-Pierre. “It is at the forefront of modern technology, and the field will undoubtedly continue to expand in its applications in the future.”
Applications of nanotechnology are all around us. In electronics, transistors are now as small as a few nanometres in size, making computers ever-more powerful, which has ushered in the digital age. Nanotechnology is responsible for touch screen displays, flexible electronics and new digital memory technologies. In medicine, nanotechnology is enabling more sensitive imaging and diagnostic tools, novel gene sequencing technologies, targeted drug delivery and tissue engineering. In the energy sector, nanotechnology is enabling more efficient solar panels, better batteries and new energy-saving products.
Nanotechnology is highly interdisciplinary, requiring people with expertise in a broad range of fields. “Nanotechnology draws on fields such as material sciences, physics, chemistry, biology, biomedicine, photonics, electrical and mechanical engineering, and more,” says Jean-Pierre. “Its applications are wide-ranging, with impacts across everyday life and industry.” This makes nanotechnology a promising career path, with plenty of opportunities to study at the forefront of scientific discovery and contribute to the improvement of society.
Pathway from school to nanotechnology
At school, Jean-Pierre recommends studying mathematics, physics, biology and chemistry to get a good grounding in the principles relevant to nanotechnology. Developing your computer programming skills will also be useful.
At university, relevant undergraduate courses that can lead to a career in nanotechnology include nanoscience, physics, chemistry, electronics engineering, materials science and computer science. Some further education institutes offer courses in nanotechnology.
Explore careers in nanotechnology
The Micro and Nanotechnology Laboratory at the University of Illinois Urbana-Champaign offers a variety of education and outreach activities, including ‘Engineering Open House’ for high school students to visit the lab and learn about the research taking place: hmntl.illinois.edu/education-and-outreach
TryNano, operated by the Institute of Electrical and Electronics Engineers (IEEE), features a range of educational resources about nanotechnology: trynano.org
Prospects provides information about what a career in nanotechnology could involve: prospects.ac.uk/job-profiles/nanotechnologist
Meet Jean-Pierre
What were your interests as a teenager?
I liked modern physics, specifically quantum mechanics and the theory of relativity.
What inspired you to become a nanotechnology researcher?
When solid-state nanotechnology emerged in the mid-eighties, I was motivated to explore this new scientific area and was excited by its ramifications for applied quantum mechanics. I had done an undergraduate degree in physics and a PhD in theoretical solid-state physics, so in the beginning of my career, the new field of solid-state nanotechnology was a natural way for me to do research at the forefront of science and technology.
What do you most enjoy about your work in nanotechnology?
I very much enjoy exploring new scientific areas, being at the forefront of the field of nanotechnology, and interpreting new nanoscale phenomena.
What are your proudest career achievements?
The first achievement occurred at the beginning of my career in the eighties, when I provided the interpretation for a newly discovered nanoscale phenomenon ahead of other renowned scientists, including two future Nobel prize winners. Around the same time, I also invented the first vertical tunnelling transistor, an important electronic device that became popular 15 years later with a wide range of applications in electronics as well as in cancer detection. With the invention of new nanopore devices, my more recent achievement is the correct interpretation and modelling of the nanoscale properties in a new type of transistor invented by a colleague of mine.
Jean-Pierre’s top tip
Follow your scientific interest and don’t be discouraged by temporary setbacks or failures.
Do you have a question for Jean-Pierre?
Write it in the comments box below and Jean-Pierre will get back to you. (Remember, researchers are very busy people, so you may have to wait a few days.)
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