Cells studied in 3-D may reveal novel cancer targets

Stephanie Fraley

Stephanie Fraley, a doctoral student in chemical and biomolecular engineering, was lead author of the study. Photo by Will Kirk/HomewoodPhoto.jhu.edu

Showing movies in 3-D has produced a box-office bonanza in recent months. Could viewing cell behavior in three dimensions lead to important advances in cancer research? A new study led by Johns Hopkins University engineers indicates it may happen. Looking at cells in 3-D, the team members concluded, yields more accurate information that could help develop drugs to prevent cancer’s spread.

“Finding out how cells move and stick to surfaces is critical to our understanding of cancer and other diseases. But most of what we know about these behaviors has been learned in the 2-D environment of Petri dishes,” said Denis Wirtz, director of the Johns Hopkins Engineering in Oncology Center and principal investigator of the study. “Our study demonstrates for the first time that the way cells move inside a three-dimensional environment, such as the human body, is fundamentally different from the behavior we’ve seen in conventional flat lab dishes. It’s both qualitatively and quantitatively different.”

One implication of this discovery is that the results produced by a common high-speed method of screening drugs to prevent cell migration on flat substrates are, at best, misleading, said Wirtz, who also is the Theophilus H. Smoot Professor of Chemical and Biomolecular Engineering at Johns Hopkins. This is important because cell movement is related to the spread of cancer, Wirtz said. “Our study identified possible targets to dramatically slow down cell invasion in a three-dimensional matrix.”

When cells are grown in two dimensions, Wirtz said, certain proteins help to form long-lived attachments called focal adhesions on surfaces. Under these 2-D conditions, these adhesions can last several seconds to several minutes. The cell also develops a broad, fan-shaped protrusion called a lamella along its leading edges, which helps move it forward. “In 3-D, the shape is completely different,” Wirtz said. “It is more spindlelike with two pointed protrusions at opposite ends. Focal adhesions, if they exist at all, are so tiny and so short-lived they cannot be resolved with microscopy.”

The study’s lead author, Stephanie Fraley, a Johns Hopkins doctoral student in Chemical and Biomolecular Engineering, said that the shape and mode of movement for cells in 2-D are merely an “artifact of their environment,” which could produce misleading results when testing the effect of different drugs. “It is much more difficult to do 3-D cell culture than it is to do 2-D cell culture,” Fraley said. “Typically, any kind of drug study that you do is conducted in 2D cell cultures before it is carried over into animal models. Sometimes, drug study results don’t resemble the outcomes of clinical studies. This may be one of the keys to understanding why things don’t always match up.”

collagen fibers

Reflection confocal micrograph of collagen fibers of a 3D matrix with cancer cells embedded. Image by Stephanie Fraley/Wirtz Lab

Fraley’s faculty supervisor, Wirtz, suggested that part of the reason for the disconnect could be that even in studies that are called 3-D, the top of the cells are still located above the matrix. “Most of the work has been for cells only partially embedded in a matrix, which we call 2.5-D,” he said. “Our paper shows the fundamental difference between 3-D and 2.5-D: Focal adhesions disappear, and the role of focal adhesion proteins in regulating cell motility becomes different.”

Wirtz added that “because loss of adhesion and enhanced cell movement are hallmarks of cancer,” his team’s findings should radically alter the way cells are cultured for drug studies. For example, the team found that in a 3-D environment, cells possessing the protein zyxin would move in a random way, exploring their local environment. But when the gene for zyxin was disabled, the cells traveled in a rapid and persistent, almost one-dimensional pathway far from their place of origin.

Fraley said such cells might even travel back down the same pathways they had already explored. “It turns out that zyxin is misregulated in many cancers,” Fraley said. Therefore, she added, an understanding of the function of proteins like zyxin in a 3-D cell culture is critical to understanding how cancer spreads, or metastasizes. “Of course tumor growth is important, but what kills most cancer patients is metastasis,” she said.

To study cells in 3-D, the team coated a glass slide with layers of collagen-enriched gel several millimeters thick. Collagen, the most abundant protein in the body, forms a network in the gel of cross-linked fibers similar to the natural extracellular matrix scaffold upon which cells grow in the body. The researchers then mixed cells into the gel before it set. Next, they used an inverted confocal microscope to view from below the cells traveling within the gel matrix. The displacement of tiny beads embedded in the gel was used to show movement of the collagen fibers as the cells extended protrusions in both directions and then pulled inward before releasing one fiber and propelling themselves forward.

Fraley compared the movement of the cells to a person trying to maneuver through an obstacle course crisscrossed with bungee cords. “Cells move by extending one protrusion forward and another backward, contracting inward, and then releasing one of the contacts before releasing the other,” she said. Ultimately, the cell moves in the direction of the contact released last.

When a cell moves along on a 2-D surface, the underside of the cell is in constant contact with a surface, where it can form many large and long-lasting focal adhesions. Cells moving in 3-D environments, however, only make brief contacts with the network of collagen fibers surrounding them–contacts too small to see and too short-lived to even measure, the researchers observed.

“We think the same focal adhesion proteins identified in 2-D situations play a role in 3-D motility, but their role in 3-D is completely different and unknown,” Wirtz said. “There is more we need to discover.”

Fraley said her future research will be focused specifically on the role of mechanosensory proteins like zyxin on motility, as well as how factors such as gel matrix pore size and stiffness affect cell migration in 3-D.

Co-investigators on this research from Washington University in St. Louis were Gregory D. Longmore, a professor of medicine, and his postdoctoral fellow Yunfeng Feng, both of whom are affiliated with the university’s BRIGHT Institute. Longmore and Wirtz lead one of three core projects that are the focus of the Johns Hopkins Engineering in Oncology Center, a National Cancer Institute-funded Physical Sciences in Oncology Center. Additional Johns Hopkins authors, all from the Department of Chemical and Biomolecular Engineering, were Alfredo Celedon, a recent doctoral recipient; Ranjini Krishnamurthy, a recent bachelor’s degree recipient; and Dong-Hwee Kim, a current doctoral student.

Funding for the research was provided by the National Cancer Institute.  This study, a collaboration with researchers at Washington University in St. Louis, appeared in the June issue of Nature Cell Biology.

Related links:

Johns Hopkins Engineering in Oncology Center

Department of Chemical and Biomolecular Engineering

Watch a related video on YouTube

Story by Mary Spiro

INBT summer scholars “Extreme Makeover: Home Edition” Airs Sept. 26

 

From left, Matthew Green-Hill, Dwayne Thomas II, Donte Jones, Durrell Igwe. (Photo by Mary Spiro/INBT)

Swirling test tubes and swinging hammers set the stage for four talented Baltimore city high school students whose summer included working in Johns Hopkins University medical research laboratories and helping build a new home for some of their fellow scholars. The young men, all part of Baltimore’s Boys Hope/Girls Hope program, were supported equally by Johns Hopkins Institute for NanoBioTechnology (INBT) and the School of Medicine to gain experience conducting research. But the producers of ABC’s “Extreme Makeover: Home Edition” television show also put the boys (and a bunch of other folks) to work to construct a spacious home for the young women of Girls Hope. (The episode featuring the Boys Hope Girls Hope home build airs this Sunday, Sept 26 at 7 p.m. as the show’s 2-hour season premier. See video in links below.)

According to the organization’s website, Boys Hope/Girls Hope is a “privately funded, non-profit multi-denominational organization that provides at-risk children with a stable home, positive parenting, high quality education, and the support needed to reach their full potential.” In the summer of 2009, INBT hosted two students to work in labs at the Johns Hopkins School of Medicine. This summer INBT hosted four Boys Hope Girls Hope scholars.

Matthew Green-Hill, 18, a junior at Archbishop Curley High School and Donte Jones, 17, a sophomore at Archbishop Curley High School returned this summer and were joined by Dwayne Thomas, 16, a junior at Loyola Blakefield and Durrell Igwe, 16, a sophomore at Archbishop Curley. (Other students participate in Boys Hope Girls Hope, but only four scholars had summer jobs at Johns Hopkins.)

 

Dwayne Thomas II shows off his summer research efforts. (Photo by Christie Johnson/INBT)

Doug Robinson, associate professor of cell biology at the School of Medicine spear-headed the effort to bring Boys Hope Girls Hope scholars to Johns Hopkins through INBT. Each scholar was paired with a graduate student or postdoctoral fellow in their host labs to ensure that they were actively engaged in an aspect of a research. “The goal of this program was to provide our scholars with a summer experience that was challenging, enriching, and personally rewarding,” Robinson said. “Additionally, the students participated in a class three mornings a week where they worked on writing, reading, and mathematics skills.”

The summer experience concluded with a poster session where the scholars showed off what they had done with family, friends, other faculty members and staff. For example, Dwayne Thomas II worked with postdoctoral fellow Alexandra Surcel in Cell Biology in Robinson’s lab to conduct research on cytokinesis in the organism Dictyostelium.

“My summer experience was very important to me on so many levels,” Thomas said. “The quality education I received this summer was outstanding because I learned so much it will help next year in school. I feel like this has really prepared me for college in the near future and also for my dream of becoming a medical doctor. During the summer program, it taught me a lot about professionalism such the importance of arriving at work on time. I know that this experience has made me strive even harder because not many people receive the same type of opportunities I do.”

Donte Jones worked on the problem of malaria in the laboratory of Caren Meyers, assistant professor in the Department of Pharmacology and Molecular Sciences at the School of Medicine. Durrell Igwe spent his summer in the neuroscience laboratory of Howard Hughes Medical Institute investigator Alex Kolodkin in the department of neuroscience. Matthew Green-Hill participated in neurodegenerative disease research in the laboratory of Craig Montell, professor of biological chemistry at the School of Medicine.

A half dozen young women also study through Girls Hope, but unlike their male counterparts, the girls had no home where they could live with their adult mentors, only a parcel of land in the Hamilton section of Baltimore. Boys Hope/Girls Hope is completely voluntary and the organization does not serve as a legal guardian to the students, but participants have the option of living in the group house or at home with their own families. Many choose to live with their classmates in the group house.

The Boys Hope scholars wanted to help the Girls Hope scholars get their home built as soon as possible. So the boys sent a video requesting that the makers of the television Extreme Makeover: Home Edition to construct a house for the girls before the start of the next school year. The plea worked and before long, several city blocks along Fleetwood Ave. were cordoned off and filled with construction equipment and workers. The 11,000 square ft. home was built in nine short days, suffering a brief setback due to severe rainstorms. Look for more photos of the Girls Hope Home on the INBT website after the television reveal.

Related Links

Boys Hope/Girls Hope Baltimore

ABC TV Extreme Makeover: Home Edition

Girls Hope of Baltimore Gets an Amazing Gift from Extreme Makeover

Story by Mary Spiro

INBT’s Nano-Magic appears at first USA Science and Engineering Festival Expo

The first USA Science & Engineering Festival Expo is set for October 23-24 on the National Mall in Washington, D.C., and Johns Hopkins Institute for NanoBioTechnology will be there showcasing some of our research. More than 1,500 interactive exhibits and stage shows are planned.

INBT will present a hands-on exhibit of demonstrations dedicated to self-assembly entitled “Nano-Magic” that will allow visitors of all ages a chance to learn about now atoms, molecules and materials have ways of building structures all by themselves. Graduate students affiliated with INBT training programs will help visitors understand the science. In addition, several of the videos created by INBT’s Animation Studio will be on display on a computer monitor.

Some of the other exhibits include the science behind TRON and other Hollywood movies, baseball, superheroes, Thanksgiving dinner, and NASCAR as well as the mathematics of speed jump roping. There are also 50 stage shows featuring science musicians, comedians, and rock stars. Even the Redskins cheerleaders will be leading a pep rally for science.

Bring the whole family to this free event. Come check out our booth located at Section NM 6, Booth No. 610, along with several other Johns Hopkins affiliated exhibits listed here. Visit the official festival website to view all exhibit and stage shows, download a map of the Expo grounds, and view the entire festival calendar.

Related Link:

INBT Animation Studio

INBT launches Johns Hopkins Center of Cancer Nanotechnology Excellence

Martin Pomper and Peter Searson will co-direct INBT’s new Center of Cancer Nanotechnology Excellence (Photo: Will Kirk/Homewood-JHU)

Faculty members associated with the Johns Hopkins Institute for NanoBioTechnology have received a $13.6 million five-year grant from the National Cancer Institute to establish a Center of Cancer Nanotechnology Excellence. The new Johns Hopkins center brings together a multidisciplinary team of scientists, engineers and physicians to develop nanotechnology-based diagnostic platforms and therapeutic strategies for comprehensive cancer care. Seventeen faculty members will be involved initially, with pilot projects adding more participants later.

The Johns Hopkins Center of Cancer Nanotechnology Excellence, which is part of the university’s Institute for NanoBioTechnology, is one of several NCI-supported centers launched through a funding opportunity started in 2005. According to the NCI, the program was established to create “multi-institutional hubs that integrate nanotechnology across the cancer research continuum to provide new solutions for the diagnosis and treatment of cancer.”

Peter Searson, who is the Joseph R. and Lynn C. Reynolds Professor of Materials Science and Engineering in the Whiting School of Engineering and director of the Institute for NanoBioTechnology, will serve as the center’s director. The co-director will be Martin Pomper, professor of radiology and oncology at the School of Medicine and the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins.

“A unique feature of the center is the integration of research, education, training and outreach, and technology commercialization,” Searson said.

To move these new technologies toward use by physicians, a Cancer Nanomedicine Commercialization Working Group will be established and headed by John Fini, director of intellectual property for the university’s Homewood campus. This group will be responsible for managing and coordinating the translational process.

Another special feature of the center will be its Validation Core, led by Pomper, who is also associate director of the Johns Hopkins In Vivo Cellular and Molecular Imaging Center and director of the Johns Hopkins Small Animal Imaging Resource Program.

“Validation is about assuring that the experimental products and results we generate are on target and able to measure the biological effects for which they’re intended,” he said.

Searson and Pomper said the center will consist of four primary research projects.

One project will seek methods to screen bodily fluids such as blood or urine for indicators of cancer found outside of the genetic code, indicators called epigenetic markers. Led by Tza-Huei “Jeff” Wang, associate professor of mechanical engineering in the Whiting School of Engineering; Stephen Baylin, the Virginia and Daniel K. Ludwig Professor of Cancer Research in the School of Medicine; and James Herman, a professor of cancer biology in the School of Medicine, this project will use semiconductor nanocrystals, also known as quantum dots, and silica superparamagnetic particles to detect DNA methylation. Methylation adds a chemical group to the exterior of the DNA and is a biomarker frequently associated with cancer.

A second project, led by Anirban Maitra, associate professor of pathology and oncology at the School of Medicine and the Johns Hopkins Kimmel Cancer Center, will focus on curcumin, a substance found in the traditional Indian spice turmeric. In preclinical studies, curcumin has demonstrated anti-cancer properties but, because of its physical size, it is not readily taken up into the bloodstream or into tissues. Engineered curcumin nanoparticles, however, can more easily reach tumors arising in abdominal organs such as the pancreas, Maitra said. This team will try to determine whether nanocurcumin, combined with chemotherapeutic agents, could become a treatment for highly lethal cancers, such as pancreatic cancer.

Hyam Levitsky, professor of oncology at the Johns Hopkins Kimmel Cancer Center, will lead a third project, which will seek to use a noninvasive method to monitor the effectiveness of vaccines for cancer and infectious diseases.

A final project will build on the work of Justin Hanes and Craig Peacock, professors in the School of Medicine, to deliver therapies directly to small cell lung cancer tissue via mucus-penetrating nanoparticles.

All research efforts will be supported by a nanoparticle engineering core, led by Searson, which will make and characterize a variety of nanomaterials. Another core, centering on bioinformatics and data sharing, will be led by Rafael Irizarry, professor of biostatistics at the Johns Hopkins Bloomberg School of Public Health.

Johns Hopkins Institute for NanoBioTechnology

Sidney Kimmel Comprehensive Cancer Center

INBT’s international research program sends second team of students to Belgium

Johns Hopkins Institute for NanoBioTechnology supports university students to conduct research in an international setting. Their work, travel and housing expenses are funded through INBT with a National Science Foundation’s International Research Experience for Students (IRES) program and through a partnership with The Inter-University MircroElectronics Centre (IMEC) in Leuven, Belgium.

This summer, two Whiting School of Engineering students, Mike Keung, a master’s student in Chemical and Biomolecular Engineering, and Kayla Culver, a recent bachelor’s graduate in Materials Science and Engineering, spent the summer conducting research at IMEC. Additional Johns Hopkins students will be traveling to Belgium later in the year.

“Students work at IMEC’s world-class microfabrication facility and learn to design, fabricate and test chip-based platforms and integrated microelectronic systems for biomedical applications,” said INBT director Peter Searson, the Joseph R. and Lynn C. Reynolds Professor of Materials Science and Engineering. “The goal of the program is to help students gain a broader, global perspective of science and technology.”

IMEC performs world-leading research in nano-electronics and nano-technology with a staff of more than 1,750 people, including 550 industrial residents and guest researchers. The research is applied to healthcare, electronics, sustainable energy, and transportation.

Keung and Culver maintained blogs about their experiences in Europe and at IMEC. Keung, who also worked at IMEC last year through the IRES program, has written his blog for two years in a row. The blogs, reflect both the rich educational and cultural experience that the IRES program is intended to provide for participants. For example, both students conducted experiments that will enhance their careers and skill sets, as well as support the research goals of their mentors both at Johns Hopkins and at IMEC. But Keung and Culver also had the opportunity to be immersed in a different culture, travel to nearby cities and countries, and practice collaborating with scientists from around the world.

For more information about INBT IRES program click here.

Clikc on the images below to check out Mike’s and Kayla’s blogs!

 

Mike Keung’s IMEC Blog

Kayla Culver’s IMEC Blog

Story by Mary Spiro

Johns Hopkins Researchers Appointed to Governor’s Task Force to Study Nanobiotechnology

Peter Searson

Steve Desiderio

Maryland Gov. Martin O’Malley has appointed Peter Searson and Steve Desiderio, two researchers from The Johns Hopkins University, to serve on a special task force to study the benefits of nanobiotechnology.

According to the governor’s office, the mission of the task force is “to study the benefits of nanobiotechnology including job creation, the development of lifesaving treatments, reductions in health care costs, the development of state-of-the-art electronics, medical equipment, chemical processes and other commercial products.”

Nanotechnology involves the application of materials and devices at the scale of just a few atoms in diameter. Nanobiotechnology attempts to apply these tiny technologies to medicine and basic science.

Searson is the Joseph R. and Lynn C. Reynolds Professor of Engineering in the university’s Whiting School of Engineering. He is a professor in the Department of Materials Science and Engineering, and he directs the Johns Hopkins Institute for NanoBioTechnology. He received his Ph.D. from the University of Manchester in England and was a postdoctoral associate at the Massachusetts Institute of Technology. He lives in Baltimore.

Desiderio is director of the Institute of Basic Biomedical Sciences, director of the Immunobiology Program at the Institute for Cell Engineering and a professor of Molecular Biology and Genetics at the Johns Hopkins University School of Medicine. Desiderio earned his M.D. and a Ph.D. from the Johns Hopkins University School of Medicine and was a postdoctoral fellow at the Massachusetts Institute of Technology. Desiderio also lives in Baltimore.

Both Searson and Desiderio are involved with research related to nanobiotechnology. Searson’s interests include nanoscience, biophysics and bioengineering. He led the launch of the Institute for Nanobiotechnology, which was established in 2006 as a cross-divisional center with research interests in the basic sciences, engineering, medicine and public health.

Desiderio’s research focuses on the immune system: how immune cells are able to recognize a diverse number of pathogens and respond to environmental cues. He studies the molecular and genetic mechanisms underlying the development of the immune system. In 2007, Desiderio was appointed by O’Malley to the Maryland Life Sciences Advisory Board.

The nanobiotechnology task force will be chaired by state Sen. Jennie M. Forehand and Del. Susan C. Lee. In addition to Searson and Desiderio, task force members include Nariman Farvadin, Peter Swaan, Esther H. Chang, Lisbeth Pettengill, Patrick Y. Lu and Lawrence Tamarkin.

Along with examining the scientific and medical benefits of nanobiotechnology, the task force members expect to look at the economic impact that the development of such technologies might have on the state of Maryland, including the creation of jobs.

The governor’s office also stated that the group will study the “generation of revenue for the state and improvements to the quality of life for the state’s citizens and the state’s role in supporting Maryland’s leadership in nanobiotechnology, including: promoting public-private partnerships; assisting companies in technology transfers, including from research to commercial product; promoting research; protecting intellectual property; offering appropriate financial incentives; including tax credits; and capturing and leveraging federal funds for both public and private ventures; and make recommendations regarding actions that the state should take to promote the growth of the nanobiotechnology industries in the state.”

Collaborative poster session for INBT’s REU students set for Aug. 5

Doug Robinson and John Molina discuss summer research. (Photo by Mary Spiro)

Johns Hopkins Institute for NanoBioTechnology hosted 16 undergraduates to conduct research in INBT affiliated laboratories this summer. On Thursday, Aug. 5, from 3-4:30 p.m. those students, plus many others who participated in short-term research projects across all JHU campuses this summer, will present their findings at a collaborative poster session in Turner Concourse at the School of Medicine. All faculty, staff, and students are invited to stop by for this informative and free event. For more information about INBT’s summer research experience for undergraduates, a National Science Foundation supported program, click here.

MedImmune scientist focuses final INBT seminar on ‘soft skills’

 

Ambarish Shah of MedImmune

Ambarish Shah, Senior Manager and Principal Scientist at MedImmune Inc., presented the final Professional Development Seminar talk hosted by the Johns Hopkins Institute for NanoBioTechnology (INBT) on July 28. Shah’s presentation included an overview of the Biopharmaceutical industry and offered an insider’s perspective on how MedImmune manages the process of protein drug development.

Shah stated that “success in your careers will not only depend on how well you master the scientific principles in theory but more so how you apply them innovatively,” impressing upon students the value of applying science to solving practical problems. In addition, he stressed the acquisition of “soft skills” along with science, such as people skills and networking. Shah stressed the importance of protecting one’s intellectual property, as well as the safety and efficacy of a product. Despite the risks and costs, he urged students to always remember the altruistic purpose behind their work, cautioning: “don’t get attached to projects, get attached to science.”

Due to the fact that new research in the field is presented at technical conferences or published in peer reviewed journals, scientists tend to speak in technical terms that are too complex for the general public to understand. Shah stated that the field is missing “the clarity in linking what we do scientifically in our labs to the tangible benefits the general public end user will see, and a good forum to share it in.”

Shah offered students insight in understanding career development, stating that career success comes from a combination of many good personal attributes such as clarity of communication, willingness to a make a persistent effort, teamwork, and of course an analytical problem solving mind (all of these which can be learned through deliberate practice). Most importantly he advised students that “Grades and publications matter, but just to get the first job. After the first job, the only thing that matters is demonstrated results.”

Shah received his PhD in Pharmaceutical Sciences from Mercer University in 1998, a Master of Science from Duquesne University, and a Bachelor of Pharmacy from Bombay University in India. He has been in the field for over twelve years and is currently the Principal Scientist/Group leader for MedImmune’s Dept. of Formulation Sciences in Gaithersburg, Md.

Story by Sarah Gubara, Senior, Psychology, Krieger School of Arts and Sciences

Postdocs share how they manage work-life balance at July 14 INBT seminar

The life of a researcher can be hectic and complex. Add to that the responsibilities of family, friends, and the career and needs of a spouse or partner, even children, and it could spell trouble. Eric Balzer, Zev Binder, Daniele Gilkes and Sam Walcott, all postdoctoral fellows associated with Johns Hopkins Institute for NanoBioTechnology, will conduct a panel discussion highlighting the challenges of balancing work and family on July 14 at 11 a.m. in 234 Ames. The discussion is part of INBT’s professional development seminars. RSVP to Ashanti Edwards, Ashanti@jhu.edu. This talk is free and open to all faculty, staff and students.

For more information visit http://inbt.jhu.edu

Nanowires Deliver Biochemical Payloads to One Cell Among Many

Imagine being able to drop a toothpick on the head of one particular person standing among 100,000 people in a sports stadium. It sounds impossible, yet this degree of precision at the cellular level has been demonstrated by researchers affiliated with The Johns Hopkins University Institute for NanoBioTechnology. Their study was published online in June in Nature Nanotechnology.

Arrow points to nanowire placed on cell surface. (Image: Levchenko/Chien labs)

The team used precise electrical fields as “tweezers” to guide and place gold nanowires, each about one-two hundredth the size of a cell, on predetermined spots, each on a single cell. Molecules coating the surfaces of the nanowires then triggered a biochemical cascade of actions only in the cell where the wire touched, without affecting other cells nearby. The researchers say this technique could lead to better ways of studying individual cells or even cell parts, and eventually could produce novel methods of delivering medication.

Indeed, the techniques not relying on this new nanowire-based technology either are not very precise, leading to stimulation of multiple cells, or require complex biochemical alterations of the cells. With the new technique the researchers can, for instance, target cells that have cancer properties (higher cell division rate or abnormal morphology), while sparing their healthy neighbors.

“One of the biggest challenges in cell biology is the ability to manipulate the cell environment in as precise a way as possible,” said principal investigator Andre Levchenko, an associate professor of biomedical engineering in Johns Hopkins’ Whiting School of Engineering. In previous studies, Levchenko has used lab-on-a-chip or microfluidic devices to manipulate cell behavior. But, he said, lab-on-a-chip methods are not as precise as researchers would like them to be. “In microfluidic chips, if you alter the cell environment, it affects all the cells at the same time,” he said.

Such is not the case with the gold nanowires, which are metallic cylinders a few hundred nanometers or smaller in diameter. Just as the unsuspecting sports spectator would feel only a light touch from a toothpick being dropped on the head, the cell reacts only to the molecules released from the nanowire in one very precise place where the wire touches the cell’s surface.

With contributions from Chia-Ling Chien, a professor of physics and astronomy in the Krieger School of Arts and Sciences, and Robert Cammarata, a professor of materials science and engineering in the Whiting School, the team developed nanowires coated with a molecule called tumor necrosis factor-alpha (TNF?), a substance released by pathogen-gobbling macrophages, commonly called white blood cells. Under certain cellular conditions, the presence of TNF? triggers cells to switch on genes that help fight infection, but TNF? also is capable of blocking tumor growth and halting viral replication.

Exposure to too much TNF?, however, causes an organism to go into a potentially lethal state called septic shock, Levchenko said. Fortunately, TNF? stays put once it is released from the wire to the cell surface, and because the effect of TNF? is localized, the tiny bit delivered by the wire is enough to trigger the desired cellular response. Much the same thing happens when TNF? is excreted by a white blood cell.

Additionally, the coating of TNF? gives the nanowire a negative charge, making the wire easier to maneuver via the two perpendicular electrical fields of the “tweezer” device, a technique developed by Donglei Fan as part of her Johns Hopkins doctoral research in materials science and engineering. “The electric tweezers were initially developed to assemble, transport and rotate nanowires in solution,” Cammarata said. “Donglei then showed how to use the tweezers to produce patterned nanowire arrays as well as construct nanomotors and nano-oscillators. This new work with Dr. Levchenko’s group demonstrates just how extremely versatile a technique it is.”

To test the system, the team cultured cervical cancer cells in a dish. Then, using electrical fields perpendicular to one another, they were able to zap the nanowires into a pre-set spot and plop them down in a precise location. “In this way, we can predetermine the path that the wires will travel and deliver a molecular payload to a single cell among many, and even to a specific part of the cell,” Levchenko said.

During the course of this study, the team also established that the desired effect generated by the nanowire-delivered TNF? was similar to that experienced by a cell in a living organism.

The team members envision many possibilities for this method of subcellular molecule delivery. “For example, there are many other ways to trigger the release of the molecule from the wires: photo release, chemical release, temperature release. Furthermore, one could attach many molecules to the nanowires at the same time,” Levchenko said. He added that the nanowires can be made much smaller, but said that for this study the wires were made large enough to see with optical microscopy.

Ultimately, Levchenko sees the nanowires becoming a useful tool for basic research. “With these wires, we are trying to mimic the way that cells talk to each other,” he said. “They could be a wonderful tool that could be used in fundamental or applied research.” Drug delivery applications could be much further off. However, Levchenko said, “If the wires retain their negative charge, electrical fields could be used to manipulate and maneuver their position in the living tissue.”

The lead authors for this Nature Nanotechnology article were Fan, a former postdoctoral fellow in the departments of materials science and engineering and in physics and astronomy; and Zhizhong Yin, a former postdoctoral fellow in the Department of Biomedical Engineering. The co-authors included Raymond Cheong, a doctoral student in the Department of Biomedical Engineering; and Frank Q. Zhu, a former doctoral student in the Department of Physics and Astronomy.

Regarding the faculty members’ participation, Chien led the group that developed the electric tweezers technique and collaborated with Levchenko on its biological applications.

The research was funded by the National Science Foundation and the National Institutes of Health.

Johns Hopkins Institute for NanoBioTechnology