Researchers Develop Nanoparticle-Based Vaccine for Skin Cancer

Nano-particles developed by scientists at Tel Aviv University have proven effective to prevent and treat melanoma.

 

While scientists have made great strides over the years to treat cancer, a vaccine for the disease—which comes in many forms and with many complexities–has yet to be discovered.

Researchers at Tel Aviv University have made a breakthrough in this endeavor with the development of a nano-vaccine for the most aggressive type of melanoma—skin cancer. The vaccine—based on a novel nanoparticle—already has shown effective in preventing the development of melanoma in mice as well as in treating the initial tumors that result from the disease, researchers said.

Researchers have developed a new nano-vaccine for melanoma, the most aggressive type of skin cancer. The vaccine is the first of its kind for cancer and paves the way for promising new prevention and treatment methods for the disease, researchers said. (Image source: Tel Aviv University)

Melanoma develops in the skin cells that produce melanin or skin pigment, but then can metastasize quickly into the brain and other organs. It currently is treated in a number of ways, including chemotherapy, radiation therapy, and immunotherapy.

All of these methods attack the disease after the fact; so far, no treatment has emerged to prevent or delay its growth in the first place, Professor Ronit Satchi-Fainaro, chair of the Department of Physiology and Pharmacology at Tel Aviv University, said in a press statement.

“The vaccine approach, which has proven so effective against various viral diseases, has not materialized yet against cancer,” said Satchi-Fainaro, who also is head of the Laboratory for Cancer Research and Nanomedicine at the university’s Sackler Faculty of Medicine. “In our study, we have shown for the first time that it is possible to produce an effective nano-vaccine against melanoma and to sensitize the immune system to immunotherapies.”

A New Approach

Nanoparticles about 170 nanometers in size are key to the approach researchers took to developing their novel vaccine. They packed two peptides—or short chains of amino acids—into each particle, which are made of a biodegradable polymer. Peptides are present in melanoma cells.

To test their vaccine, researchers injected the nano-particles into a mouse with melanoma to test its effectiveness. What they found is that the nanoparticles acted similarly to existing vaccines for viruses, which long have proved effective against viral-borne diseases, Satchi-Fainaro said.

“They stimulated the immune system of the mice, and the immune cells learned to identify and attack cells containing the two peptides–that is, the melanoma cells,” she said in the statement. “This meant that, from now on, the immune system of the immunized mice will attack melanoma cells if and when they appear in the body.”

Researchers published a study on their work in the journal Nature Nanotechnology.

Successful Prevention and Treatment

Satchi-Fainaro’s team focused on three different conditions to determine the nano-vaccine’s effectiveness. The first was to see if it would prevent the growth of the disease if melanoma cells were injected into mice, which it did, she said.

Researchers also used the nano-vaccine to treat a primary melanoma tumor in combination with immunotherapy treatments, they said. The treatment delayed the progression of the disease and significantly extended the lives of the mice in this study, researchers said.

Finally, the researchers gauged the nano-vaccine’s effectiveness in treating brain metastases, which are associated with melanoma, using tissue from patients with these metastases. The vaccine showed it could also be a successful treatment in this case, paving the way for “effective treatment of melanoma, even in the most advanced stages of the disease,” Satchi-Fainaro said in the statement.

The team plans to continue its work to develop nano-particles to vaccinate people not only against melanoma, but potentially against other forms of cancer as well, she added.

 

Scientists develop novel nano-vaccine for melanoma

Melanoma in skin biopsy with H&E stain — this case may represent superficial spreading melanoma. Credit: Wikipedia/CC BY-SA 3.0

Researchers at Tel Aviv University have developed a novel nano-vaccine for melanoma, the most aggressive type of skin cancer. Their innovative approach has so far proven effective in preventing the development of melanoma in mouse models and in treating primary tumors and metastases that result from melanoma.

The focus of the research is on a nanoparticle that serves as the basis for the new vaccine. The study was led by Prof. Ronit Satchi-Fainaro, chair of the Department of Physiology and Pharmacology and head of the Laboratory for Cancer Research and Nanomedicine at TAU’s Sackler Faculty of Medicine, and Prof. Helena Florindo of the University of Lisbon while on sabbatical at the Satchi-Fainaro lab at TAU; it was conducted by Dr. Anna Scomparin of Prof. Satchi-Fainaro’s TAU lab, and postdoctoral fellow Dr. João Conniot. The results were published on August 5 in Nature Nanotechnology.

Melanoma develops in the skin cells that produce melanin or skin pigment. “The war against cancer in general, and melanoma in particular, has advanced over the years through a variety of treatment modalities, such as chemotherapy, radiation therapy and immunotherapy; but the vaccine approach, which has proven so effective against various viral diseases, has not materialized yet against cancer,” says Prof. Satchi-Fainaro. “In our study, we have shown for the first time that it is possible to produce an effective nano-vaccine against melanoma and to sensitize the immune system to immunotherapies.”

The researchers harnessed tiny particles, about 170 nanometers in size, made of a biodegradable polymer. Within each particle, they “packed” two peptides—short chains of amino acids, which are expressed in melanoma cells. They then injected the nanoparticles (or “nano-vaccines”) into a mouse model bearing melanoma.

“The nanoparticles acted just like known vaccines for viral-borne diseases,” Prof. Satchi-Fainaro explains. “They stimulated the immune system of the mice, and the immune cells learned to identify and attack cells containing the two peptides—that is, the melanoma cells. This meant that, from now on, the immune system of the immunized mice will attack melanoma cells if and when they appear in the body.”

The researchers then examined the effectiveness of the vaccine under three different conditions.

First, the vaccine proved to have prophylactic effects. The vaccine was injected into healthy mice, and an injection of melanoma cells followed. “The result was that the mice did not get sick, meaning that the vaccine prevented the disease,” says Prof. Satchi-Fainaro.

Second, the nanoparticle was used to treat a primary tumor: A combination of the innovative vaccine and immunotherapy treatments was tested on melanoma model mice. The synergistic treatment significantly delayed the progression of the disease and greatly extended the lives of all treated mice.

Finally, the researchers validated their approach on tissues taken from patients with melanoma brain metastases. This suggested that the nano-vaccine can be used to treat brain metastases as well. Mouse models with late-stage melanoma brain metastases had already been established following excision of the primary melanoma lesion, mimicking the clinical setting. Research on image-guided surgery of primary melanoma using smart probes was published last year by Prof. Satchi-Fainaro’s lab.

“Our research opens the door to a completely new approach—the vaccine approach—for effective treatment of melanoma, even in the most advanced stages of the disease,” concludes Prof. Satchi-Fainaro. “We believe that our platform may also be suitable for other types of cancer and that our work is a solid foundation for the development of other cancer nano-vaccines.”

More information: Immunization with mannosylated nanovaccines and inhibition of the immune-suppressing microenvironment sensitizes melanoma to immune checkpoint modulators, Nature Nanotechnology(2019). DOI: 10.1038/s41565-019-0512-0 , https://nature.com/articles/s41565-019-0512-0

Journal information: Nature Nanotechnology

Provided by Tel Aviv University

Russian Billionaire Makes Big Investment In Nanotechnology – Tel Aviv University receives $30 Million

Russian billionaire Roman Abramovich is known for a number of things. He’s the owner of the Chelsea Football Club. He’s a super yacht aficionado. He dates very beautiful, very young women—usually models. And now he’s a major philanthropist.

In 2015, Tel Aviv University announced a major anonymous donation to the school’s new Center for Nanoscience and Nanotechnology. It turns out that the anonymous benefactor was none other than Abramovich. The oligarch made a $30 million donation to the new center which is scheduled to open in 2020. His identity remained a secret until now.

Tel Aviv University opened its current Center for Nanoscience and Nanotechnology in 2000. At the time, it was the first school of its kind in Israel. Today, the center works with more than 90 research groups across varying discipline. The center also works closely with other nanoscience and nanotechnology groups and institutes across the globe. The rapid growth of the industry created the need for a larger, newer, and better equipped nanotechnology school. Abramovich’s donation made this possible for the university.

Once the new center is finished, it will be one of the leading facilities for nanoscience and nanotechnology in that part of the world. The three story, 75,000 square foot building will have 16 research labs including brand new ones dedicated to the study of quantum effects.

Roman Abramovich has a net worth of $10 billion.

Novel Nanomedicine Inhibits Progression of Pancreatic Cancer in Mice – Tel Aviv University

Survival rates in pancreatic cancer linked to inverse correlation between specific oncogene and tumor suppressant, Tel Aviv University researchers say

A new Tel Aviv University study pinpoints the inverse correlation between a known oncogene — a gene that promotes the development of cancer — and the expression of an oncosuppressor microRNA as the reason for extended pancreatic cancer survival. The study may serve as a basis for the development of an effective cocktail of drugs for this deadly disease and other cancers.

The study, which was published in Nature Communications, was led by Prof. Ronit Satchi-Fainaro, Chair of the Department of Physiology and Pharmacology at TAU’s Sackler Faculty of Medicine, and conducted by Hadas Gibori and Dr. Shay Eliyahu, both of Prof. Satchi-Fainaro’s multidisciplinary laboratory, in collaboration with Prof. Eytan Ruppin of TAU’s Computer Science Department and the University of Maryland and Prof. Iris Barshack and Dr. Talia Golan of Chaim Sheba Medical Center, Tel Hashomer.

Pancreatic cancer is among the most aggressive cancers known today. The overwhelming majority of pancreatic cancer patients die within just a year of diagnosis. “Despite all the treatments afforded by modern medicine, some 75% of all pancreatic cancer patients die within 12 months of diagnosis, including many who die within just a few months,” Prof. Satchi-Fainaro says.

“But around seven percent of those diagnosed will survive more than five years. We sought to examine what distinguishes the survivors from the rest of the patients,” Prof. Satchi-Fainaro continues. “We thought that if we could understand how some people live several years with this most aggressive disease, we might be able to develop a new therapeutic strategy.”

Calling a nano-taxi

The research team examined pancreatic cancer cells and discovered an inverse correlation between the signatures of miR-34a, a tumor suppressant, and PLK1, a known oncogene. The levels of miR-34a were low in pancreatic cancer mouse models, while the levels of the oncogene were high. This correlation made sense for such an aggressive cancer. But the team needed to see if the same was true in humans.

The scientists performed RNA profiling and analysis of samples taken from pancreatic cancer patients. The molecular profiling revealed the same genomic pattern found earlier in mouse models of pancreatic cancer.

The scientists then devised a novel nanoparticle that selectively delivers genetic material to a tumor and prevents side effects in surrounding healthy tissues.

“We designed a nanocarrier to deliver two passengers: (1) miR-34a, which degrades hundreds of oncogenes; and (2) a PLK1 small interfering RNA (siRNA), that silences a single gene,” Prof. Satchi-Fainaro says. “These were delivered directly to the tumor site to change the molecular signature of the cancer cells, rendering the tumor dormant or eradicating it altogether.

“The nanoparticle is like a taxi carrying two important passengers,” Prof. Satchi-Fainaro continues. “Many oncology protocols are cocktails, but the drugs usually do not reach the tumor at the same time. But our ‘taxi’ kept the ‘passengers’ — and the rest of the body — safe the whole way, targeting only the tumor tissue. Once it ‘parked,’ an enzyme present in pancreatic cancer caused the carrier to biodegrade, allowing the therapeutic cargo to be released at the correct address — the tumor cells.”

Improving the odds

To validate their findings, the scientists injected the novel nanoparticles into pancreatic tumor-bearing mice and observed that by balancing these two targets — bringing them to a normal level by increasing their expression or blocking the gene responsible for their expression — they significantly prolonged the survival of the mice.

“This treatment takes into account the entire genomic pattern, and shows that affecting a single gene is not enough for the treatment of pancreatic cancer or any cancer type in general,” according to Prof. Satchi-Fainaro.

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Research for the study was funded by the European Research Council (ERC), Tel Aviv University’s Cancer Biology Research Center (CBRC) and the Israel Science Foundation (ISF).

American Friends of Tel Aviv University (AFTAU) supports Israel’s most influential, comprehensive and sought-after center of higher learning, Tel Aviv University (TAU). TAU is recognized and celebrated internationally for creating an innovative, entrepreneurial culture on campus that generates inventions, startups and economic development in Israel. For three years in a row, TAU ranked 9th in the world, and first in Israel, for alumni going on to become successful entrepreneurs backed by significant venture capital, a ranking that surpassed several Ivy League universities. To date, 2,400 patents have been filed out of the University, making TAU 29th in the world for patents among academic institutions.

Tel Aviv Univeristy: “Vibrating” Nanotubes in Water Create a 300% Improvement in the ‘Rate of Diffusion’: IBM Crowd Computing to Simulate in Demonstration

Nearly 800 million people worldwide don’t have access to safe drinking water, and some 2.5 billion people live in precariously unsanitary conditions, according to the Centers for Disease Control and Prevention. Together, unsafe drinking water and the inadequate supply of water for hygiene purposes contribute to almost 90% of all deaths from diarrheal diseases — and effective water sanitation interventions are still challenging scientists and engineers.

A new study published in Nature Nanotechnology proposes a novel nanotechnology-based strategy to improve water filtration. The research project involves the minute vibrations of carbon nanotubes called “phonons,” which greatly enhance the diffusion of water through sanitation filters. The project was the joint effort of a Tsinghua University-Tel Aviv University research team and was led by Prof. Quanshui Zheng of the Tsinghua Center for Nano and Micro Mechanics and Prof. Michael Urbakh of the TAU School of Chemistry, both of the TAU-Tsinghua XIN Center, in collaboration with Prof. Francois Grey of the University of Geneva.

Shake, rattle, and roll

“We’ve discovered that very small vibrations help materials, whether wet or dry, slide more smoothly past each other,” said Prof. Urbakh. “Through phonon oscillations — vibrations of water-carrying nanotubes — water transport can be enhanced, and sanitation and desalination improved. Water filtration systems require a lot of energy due to friction at the nano-level. With these oscillations, however, we witnessed three times the efficiency of water transport, and, of course, a great deal of energy saved.”

The research team managed to demonstrate how, under the right conditions, such vibrations produce a 300% improvement in the rate of water diffusion by using computers to simulate the flow of water molecules flowing through nanotubes. The results have important implications for desalination processes and energy conservation, e.g. improving the energy efficiency for desalination using reverse osmosis membranes with pores at the nanoscale level, or energy conservation, e.g. membranes with boron nitride nanotubes.

Crowdsourcing the solution

The project, initiated by IBM’s World Community Grid, was an experiment in crowdsourced computing — carried out by over 150,000 volunteers who contributed their own computing power to the research.

“Our project won the privilege of using IBM’s world community grid, an open platform of users from all around the world, to run our program and obtain precise results,” said Prof. Urbakh. “This was the first project of this kind in Israel, and we could never have managed with just four students in the lab. We would have required the equivalent of nearly 40,000 years of processing power on a single computer. Instead we had the benefit of some 150,000 computing volunteers from all around the world, who downloaded and ran the project on their laptops and desktop computers.

“Crowdsourced computing is playing an increasingly major role in scientific breakthroughs,” Prof. Urbakh continued. “As our research shows, the range of questions that can benefit from public participation is growing all the time.”

The computer simulations were designed by Ming Ma, who graduated from Tsinghua University and is doing his postdoctoral research in Prof. Urbakh’s group at TAU. Ming catalyzed the international collaboration. “The students from Tsinghua are remarkable. The project represents the very positive cooperation between the two universities, which is taking place at XIN and because of XIN,” said Prof. Urbakh.

Other partners in this international project include researchers at the London Centre for Nanotechnology of University College London; the University of Geneva; the University of Sydney and Monash University in Australia; and the Xi’an Jiaotong University in China. The researchers are currently in discussions with companies interested in harnessing the oscillation know-how for various commercial projects.

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Story Source:

The above post is reprinted from materials provided by American Friends of Tel Aviv University. Note: Materials may be edited for content and length.

‘Super-Cool’ way to Deliver Drugs

Water, when cooled below 32°F, eventually freezes — it’s science known even to pre-schoolers. But some substances, when they undergo a process called “rapid-freezing” or “supercooling,” remain in liquid form — even at below-freezing temperatures.

The supercooling phenomenon has been studied for its possible applications in a wide spectrum of fields. A new Tel Aviv University study published in Scientific Reports is the first to break down the rules governing the complex process of crystallization through rapid-cooling. According to the research, membranes can be engineered to crystallize at a specific time. In other words, it is indeed possible to control what was once considered a wild and unpredictable process — and it may revolutionize the delivery of drugs in the human body, providing a way to “freeze” the drugs at the exact time and biological location in the body necessary.

The study was led jointly by Dr. Roy Beck of the Department of Physics at TAU’s School of Physics and Astronomy and Prof. Dan Peer of the Department of Cell Research and Immunology at TAU’s Faculty of Life Sciences, and conducted by TAU graduate students Guy Jacoby, Keren Cohen, and Kobi Barkai.

Controlling a metastable process

“We describe a supercooled material as ‘metastable,’ meaning it is very sensitive to any external perturbation that may transform it back to its stable low-temperature state,” Dr. Beck said. “We discovered in our study that it is possible to control the process and harness the advantages of the fluid/not-fluid transition to design a precise and effective nanoscale drug encapsulating system.”

For the purpose of the study, the researchers conducted experiments on nanoscale drug vesicles (fluid-filled sacs that deliver drugs to their targets) to determine the precise dynamics of crystallization. The researchers used a state-of-the-art X-ray scattering system sensitive to nanoscale structures.

“One key challenge in designing new nano-vesicles for drug delivery is their stability,” said Dr. Beck. “On the one hand, you need a stable vesicle that will entrap your drug until it reaches the specific diseased cell. But on the other, if the vesicle is too stable, the payload may not be released upon arrival at its target.”

“Supercooled material is a suitable candidate since the transition between liquid and crystal states is very drastic and the liquid membrane explodes to rearrange as crystals. Therefore this new physical insight can be used to release entrapped drugs at the target and not elsewhere in the body’s microenvironment. This is a novel mechanism for timely drug release.”

All in the timing

The researchers found that the membranes were able to remain stable for tens of hours before collectively crystallizing at a predetermined time.

“What was amazing was our ability to reproduce the results over and over again without any complicated techniques,” said Dr. Beck. “We showed that the delayed crystallization was not sensitive to minor imperfection or external perturbation. Moreover, we found multiple alternative ways to ‘tweak the clock’ and start the crystallization process.”

The researchers are investigating an appropriate new nano-capsule capable of releasing medication at a specific time and place in the body. “The challenge now is to find the right drugs to exploit our insights for the medical benefit of patients,” said Dr. Beck.

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Story Source:

The above story is based on materials provided by American Friends of Tel Aviv University. Note: Materials may be edited for content and length.

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Journal Reference:

1. Guy Jacoby, Keren Cohen, Kobi Barkan, Yeshayahu Talmon, Dan Peer, Roy Beck. Metastability in lipid based particles exhibits temporally deterministic and controllable behavior. Scientific Reports, 2015; 5: 9481 DOI: 10.1038/srep09481

Tel Aviv University: Israeli Scientists Develop The Future Of Flexible Display Screens: Using DNA Nanotechnology

Imagine an electronic screen that looks and feels like paper that could connect to your smartphone. You can shift your longer readings and video viewing to this bendable screen, then roll it up and throw it in your bag when you arrive at your subway stop. This may sound like sci-fi, but Israeli researchers have actually found a way to develop such thin, flexible screens you can use on the go.

A new Tel Aviv University study suggests that a novel DNA nanotechnology could produce a structure that can be used to produce ultra-thin, flexible screens. The research team’s building blocks are three molecules they’ve synthesized, which later self-assembled into ordered structures. Essentially, the team has built the molecular backbone of a super-slim, bendable digital display. In the field of bio-nanotechnology, scientists utilize these molecular building blocks to develop cutting-edge technologies with properties not available for inorganic materials such as plastic and metal.

This could provide a solution to roughly 2 billion smartphone users who may not want the content they view to be confined to a pocket-sized screen. That’s because currently the size of smartphone screens makes it particularly hard to read more than a few hundred words at a time or watch videos without feeling like you’re on the tilt-a-whirl at Six Flags.

The number of people using mobile devices to view media is on the rise. According to Pew Research Center, 68 percent of smartphone owners use their phone occasionally to follow breaking news stories, and 33 percent do it frequently. Moreover, YouTube reports that 50 percent of its 4 billion video views per month are watched on a mobile device.

SEE ALSO: CES 2015: The Best Of Israeli Tech

The structures formed by the researchers were found to emit light in every color, as opposed to other fluorescent materials that shine only in one specific color. Moreover, light emission was observed in response to electric voltage — which makes this technology a perfect candidate for display screens.

The TAU researchers, who recently published their findings in the scientific journal Nature Nanotechnology, are currently building a prototype of the screen and are in talks with major consumer electronics companies regarding the technology, which they’ve patented. “Our material is light, organic and environmentally friendly,” TAU’s Prof. Ehud Gazit said in a statement. “It is flexible, and its single layer emits the same range of light that requires several layers today.” Moreover, fewer layers are better for consumers, he says: “By using only one layer, you can minimize production costs dramatically, which will lead to lower prices.”

Back to the good old newspaper display? 

It’s important to mention that this technology is still in its early stages and a price tag for these screens remains unknown. What is clear, however, is that the desire to consume content on portable, large screens isn’t going away and consumer preferences are trending more and more toward bigger screens.

Ironically, people seem to be drawn back to the old newspaper display – thin, flexible, and capable of being rolled up; now, all of these features are turning digital.

Regardless of flexibility, the tendency to enlarge mobile screens was already evident last year. It is widely believed that sales of Apple and Samsung (500 million smartphone in 2014) were buoyed by their newest smartphone iterations which boast larger screens than past versions. Apple especially took note of this trend, releasing the iPhone 6 (4.7 inch screen) and iPhone 6 Plus (5.5 inches) simultaneously.

Photos and video: LG, U.S. Army RDECOM

Roll-Up Your TV Screen and Store It Away! How is that Possible?!

From smartphones and tablets to computer monitors and interactive TV screens, electronic displays are everywhere. As the demand for instant, constant communication grows, so too does the urgency for more convenient portable devices — especially devices, like computer displays, that can be easily rolled up and put away, rather than requiring a flat surface for storage and transportation.

A new Tel Aviv University study, published in Nature Nanotechnology, suggests that a novel DNA-peptide structure can be used to produce thin, transparent, and flexible screens. The research, conducted by Prof. Ehud Gazit and doctoral student Or Berger of the Department of Molecular Microbiology and Biotechnology at TAU’s George S. Wise Faculty of Life Sciences, in collaboration with Dr. Yuval Ebenstein and Prof. Fernando Patolsky of the School of Chemistry at TAU’s Faculty of Exact Sciences, harnesses bionanotechnology to emit a full range of colors in one pliable pixel layer — as opposed to the several rigid layers that constitute today’s screens.

“Our material is light, organic, and environmentally friendly,” says Prof. Gazit. “It is flexible, and a single layer emits the same range of light that requires several layers today. By using only one layer, you can minimize production costs dramatically, which will lead to lower prices for consumers as well.”

For the purpose of the study, a part of Berger’s Ph.D. thesis, the researchers tested different combinations of peptides: short protein fragments, embedded with DNA elements which facilitate the self-assembly of a unique molecular architecture.

Peptides and DNA are two of the most basic building blocks of life. Each cell of every life form is composed of such building blocks. In the field of bionanotechnology, scientists utilize these building blocks to develop novel technologies with properties not available for inorganic materials such as plastic and metal.

“Our lab has been working on peptide nanotechnology for over a decade, but DNA nanotechnology is a distinct and fascinating field as well. When I started my doctoral studies, I wanted to try and converge the two approaches,” says Berger. “In this study, we focused on PNA — peptide nucleic acid, a synthetic hybrid molecule of peptides and DNA. We designed and synthesized different PNA sequences, and tried to build nano-metric architectures with them.”

Using methods such as electron microscopy and X-ray crystallography, the researchers discovered that three of the molecules they synthesized could self-assemble, in a few minutes, into ordered structures. The structures resembled the natural double-helix form of DNA, but also exhibited peptide characteristics. This resulted in a very unique molecular arrangement that reflects the duality of the new material.

“Once we discovered the DNA-like organization, we tested the ability of the structures to bind to DNA-specific fluorescent dyes,” says Berger. “To our surprise, the control sample, with no added dye, emitted the same fluorescence as the variable. This proved that the organic structure is itself naturally fluorescent.”

The structures were found to emit light in every color, as opposed to other fluorescent materials that shine only in one specific color. Moreover, light emission was observed also in response to electric voltage — which make it a perfect candidate for opto-electronic devices like display screens.

The study was funded by the Momentum Fund of Ramot, TAU’s technology transfer company, which also patented the new technology. The researchers are currently building a prototype of the screen and are in talks with major consumer electronics companies regarding the technology.

Release Date: March 31, 2015
Source: Tel Aviv University

Solar Cell Consisting of a Single Molecule: Individual Protein Complex Generates Electric Current

ScienceDaily (Oct. 2, 2012) — An team of scientists, led by Joachim Reichert, Johannes Barth, and Alexander Holleitner (Technische Universitaet Muenchen, Clusters of Excellence MAP and NIM), and Itai Carmeli (Tel Aviv University) developed a method to measure photocurrents of a single functionalized photosynthetic protein system. The scientists could demonstrate that such a system can be integrated and selectively addressed in artificial photovoltaic device architectures while retaining their biomolecular functional properties.

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The proteins represent light-driven, highly efficient single-molecule electron pumps that can act as current generators in nanoscale electric circuits.

 Photosystem-I (green) is optically excited by an electrode (on top). An electron then is transferred step by step in only 16 nanoseconds. (Credit: Christoph Hohmann (NIM))

The interdisciplinary team publishes the results in Nature Nanotechnologythis week.

The scientist investigated the photosystem-I reaction center which is a chlorophyll protein complex located in membranes of chloroplasts from cyanobacteria. Plants, algae and bacteria use photosynthesis to convert solar energy into chemical energy. The initial stages of this process — where light is absorbed and energy and electrons are transferred — are mediated by photosynthetic proteins composed of chlorophyll and carotenoid complexes. Until now, none of the available methods were sensitive enough to measure photocurrents generated by a single protein. Photosystem-I exhibits outstanding optoelectronic properties found only in photosynthetic systems. The nanoscale dimension further makes the photosystem-I a promising unit for applications in molecular optoelectronics.

The first challenge the physicists had to master was the development of a method to electrically contact single molecules in strong optical fields. The central element of the realized nanodevice are photosynthetic proteins self-assembled and covalently bound to a gold electrode via cysteine mutation groups. The photocurrent was measured by means of a gold-covered glass tip employed in a scanning near-field optical microscopy set-up. The photosynthetic proteins are optically excited by a photon flux guided through the tetrahedral tip that at the same time provides the electrical contact. With this technique, the physicists were able to monitor the photocurrent generated in single protein units.

The research was supported by the German Research Foundation (DFG) via the SPP 1243 (grants HO 3324/2 and RE 2592/2), the Clusters of Excellence Munich-Centre for Advanced Photonics and Nanosystems Initiative Munich, as well as ERC Advanced Grant MolArt (no. 47299).