Coated nanoparticles move easily into brain tissue

Real-time imaging of nanoparticles green) coated with polyethylene-glycol (PEG), a hydrophilic, non-toxic polymer, penetrate within normal rodent brain. Without the PEG coating, negatively charged, hydrophobic particles (red) of a similar size do not penetrate. Image by Elizabeth Nance, Kurt Sailor, Graeme Woodworth.

Johns Hopkins researchers report they are one step closer to having a drug-delivery system flexible enough to overcome some key challenges posed by brain cancer and perhaps other maladies affecting that organ. In a report published online Aug. 29 in Science Translational Medicine, the Johns Hopkins team says its bioengineers have designed nanoparticles that can safely and predictably infiltrate deep into the brain when tested in rodent and human tissue.

“We are pleased to have found a way to prevent drug-embedded particles from sticking to their surroundings so that they can spread once they are in the brain,” said Justin Hanes, Lewis J. Ort Professor of Ophthalmology and project leader in the Johns Hopkins Center of Cancer Nanotechnology Excellence.

Standard protocols following the removal of brain tumors include chemotherapy directly applied to the surgical site to kill any cancer cells left behind. This method, however, is only partially effective because it is hard to administer a dose of chemotherapy high enough to sufficiently penetrate the tissue to be effective and low enough to be safe for the patient and healthy tissue. Furthermore, previous versions of drug-loaded nanoparticles typically adhere to the surgical site and do not penetrate into the tissue.

These newly engineered nanoparticles overcome this challenge. Elizabeth Nance, a graduate student in chemical and biomolecular engineering, and Johns Hopkins neurosurgeon Graeme Woodworth, suspected that drug penetration might be improved if drug-delivery nanoparticles interacted minimally with their surroundings. Nance achieved this by coating nano-scale beads with a dense layer of PEG or poly(ethylene glycol). The team then injected the coated beads, which had been marked with a fluorescent tag,  into slices of rodent and human brain tissue. They found that a dense coating of PEG allowed larger beads to penetrate the tissue, even those beads that were nearly twice the size previously thought to be the maximum possible for penetration within the brain. They then tested these beads in live rodent brains and found the same results.

Elizabeth Nance. Photo by Ming Yang.

The results were similar when biodegradable nanoparticles carrying the chemotherapy drug paclitaxel and coated with PEG were used. “It’s really exciting that we now have particles that can carry five times more drug, release it for three times as long and penetrate farther into the brain than before,” said Nance. “The next step is to see if we can slow tumor growth or recurrence in rodents.”

Woodworth added that the team “also wants to optimize the particles and pair them with drugs to treat other brain diseases, like multiple sclerosis, stroke, traumatic brain injury, Alzheimer’s and Parkinson’s.” Another goal for the team is to be able to administer their nanoparticles intravenously, which is research they have already begun.

Additional authors on the paper include Kurt Sailor, Ting-Yu Shih, Qingguo Xu, Ganesh Swaminathan, Dennis Xiang, and Charles Eberhart, all from The Johns Hopkins University.

Story adapted from an original press release by Cathy Kolf.

 

Additional news coverage of this research can be found at the following links:

Nanotechnology/Bio & Medicine

Death and Taxes Mag

New Scientist Health

Nanotech Web

Portugese news release (in Portugese)

German Public Radio (in German)

Device with tiny ‘speed bumps’ sorts cells

These illustrations show magnetically labeled circulating tumor cells (shown as yellow spheres), together with red, white and platelet cells, attempting to travel over an array of slanted ramps. The ramps act as speed bumps, slowing the tumor cells.. (Illustration by Martin Rietveld)

In life, we sort soiled laundry from clean; ripe fruit from rotten. Two Johns Hopkins engineers say they have found an easy way to use gravity or simple forces to similarly sort microscopic particles and bits of biological matter—including circulating tumor cells.

In the May 25 online issue of Physical Review LettersGerman Drazer, an assistant professor of chemical and biomolecular engineering, and his doctoral student, Jorge A. Bernate, reported that they have developed a lab-on-chip platform, also known as a microfluidic device, that can sort particles, cells or other tiny matter by physical means such as gravity. By moving a liquid over a series of micron-scale high diagonal ramps—similar to speed bumps on a road—the device causes microscopic material to separate into discrete categories, based on weight, size or other factors, the team reported.

As the tumor cells slow, the flow carries them along the length of the ramp, causing lateral displacement. After the tumor cells traverse an array of these ramps, they have sufficiently been displaced and can be continuously isolated from other cells in the sample. (Illustration by Martin Rietveld)

The process described in the journal article could be used to produce a medical diagnostic tool, the Whiting School of Engineering researchers say. “The ultimate goal is to develop a simple device that can be used in routine checkups by health care providers,” said doctoral student Bernate, who is lead author on the paper. “It could be used to detect the handful of circulating tumor cells that have managed to survive among billions of normal blood cells. This could save millions of lives.”

Ideally, these cancer cells in the bloodstream could be detected and targeted for treatment before they’ve had a chance to metastasize, or spread cancer elsewhere. Detection at early stages of cancer is critical for successful treatment.

How does this sorting process occur? Bernate explained that inside the microfluidic device, particles and cells that have been suspended in liquid flow along a “highway” that has speed-bump-like obstacles positioned diagonally, instead of perpendicular to, the path. The speed bumps differ in height, depending on the application.

“As different particles are driven over these diagonal speed bumps, heavier ones have a harder time getting over than the lighter ones,” the doctoral student said. When the particles cannot get over the ramp, they begin to change course and travel diagonally along the length of the obstacle. As the process continues, particles end up fanning out in different directions.

“After the particles cross this section of the ‘highway,’” Bernate said, “they end up in different ‘lanes’ and can take different ‘exits,’ which allows for their continuous separation.”

Gravity is not the only way to slow down and sort particles as they attempt to traverse the speed bumps. “Particles with an electrical charge or that are magnetic may also find it hard to go up over the obstacles in the presence of an electric or magnetic field,” Bernate said. For example, cancer cells could be “weighted down” with magnetic beads and then sorted in a device with a magnetic field.

The ability to sort and separate things at the micro- and nanoscale is important in many industries, ranging from solar power to bio-security. But Bernate said that a medical application is likely to be the most promising immediate use for the device.

He is slated to complete his doctoral studies this summer, but until then, Bernate will continue to collaborate with researchers in the lab of Konstantinos Konstantopoulos, professor and chair of the Department of Chemical and Biomolecular Engineering, and with colleagues at InterUniversity Microelectronics Center, IMEC, in Belgium. In 2011, Bernate spent 10 weeks at IMEC in a program hosted by Johns Hopkins’ Institute for NanoBioTechnology and funded by the National Science Foundation.

His doctoral adviser, Drazer, said, the research described in the new journal article eventually led Jorge down the path at IMEC to develop a device that can easily sort whole blood into its components. A provisional patent has been filed for this device.

The research by Bernate and Drazer was funded in part by the National Science Foundation and the National Institutes of Health.

Story by Mary Spiro.

Related links:

 

 

German Drazer’s Web page: http://microfluidics.jhu.edu/

Department of Chemical and Biomolecular Engineering: http://www.jhu.edu/chembe/

Students talk cancer nanotech at Homewood March 21

Students affiliated with the Center of Cancer Nanotechnology Excellence (CCNE) and the Physical Sciences-Oncology Center (PS-OC) at Johns Hopkins University have organized a spring mini-symposium for March 21, 10 a.m. in the Hackerman Hall Auditorium at the Johns Hopkins University Homewood campus.

The student-run mini-symposiums aim to bring together researchers from across the campus affiliated with the PS-OC and CCNE. Graduate students training in these centers, both administered by Johns Hopkins Institute for NanoBioTechnology, work in various disciplines from physics to engineering to the basic biological sciences but with an emphasis on understanding cancer metastasis and developing methods for cancer diagnosis or therapy.

The invited speaker for the symposium is postdoctoral researcher Megan Ho of Duke University. Ho earned her PhD in mechanical engineering in the Wang lab in 2008. She is currently focused on developing microfluidic devices to investigate and control the fundamental reactions that form nanocomplexes for gene delivery. (10 a.m.)

Student apeakers, who will talk for 15 minutes, include:

  • Jane Chisholm (Justin Hanes lab/Ophthalmology): Cisplatin nanocomplexes for the local treatment of small cell lung cancer (10:20 a.m.)
  • Yunke Song (Jeff Wang Lab/Mechanical Engineering): Single Quantum Dot-Based Multiplexed Point Mutation Detection by Gap Ligase Chain Reaction (10:35 a.m.)
  • Andrew Wong (Peter Searson Lab/Materials Science and Engineering): Intravisation into an artificial blood vessel (10:50 a.m.)
  • Brian Keeley: (Jeff Wang Lab/Mechanical Engineering): Overcoming detection limitations of DNA methylation in plasma and serum of cancer patients through utilization of nanotechnology. (11:05 a.m.)
  • Sebastian Barretto (Sharon Gerecht Lab/Chemical and Biomolecular Engineering): Development of Hydrogel Microfibers to Study Angiogenesis (11:20 a.m.)

View the symposium flyer here. The mini-symposium is free and open to the entire Johns Hopkins University community. No RSVP is required, although seating is limited.

Johns Hopkins Physical Sciences-Oncology Center

Center of Cancer Nanotechnology Excellence

Hopkins to host colloid, surface science symposium

The Johns Hopkins University is hosting the 86th American Chemical Society’s Colloid and Surface Science Symposium in Baltimore, MD on June 10-13, 2012. The meeting includes 13 parallel sessions, a poster session, 28 invited speakers, and 28 session organizers. A new addition to this meeting is the Langmuir Student Awards presentation session with application details given on the conference website.

Abstract submission is now open and the deadline is February 7, 2012. Up-to-date information on the meeting can be found at the website: www.colloids2012.org.

For further details about this meeting please contact the symposium co-organizers Mike Bevan (mabevan@jhu.edu) and Joelle Frechette (jfrechette@jhu.edu). Bevan and Frechette are affiliated faculty members of Johns Hopkins Institute for NanoBioTechnology and members of the Department of Chemical and Biomolecular Engineering.

Download the symposium flyer here.

 

Engineered hydrogel helps grow new, scar-free skin

In early testing, this hydrogel, developed by Johns Hopkins researchers, helped improve healing in third-degree burns. Photo by Will Kirk/HomewoodPhoto.jhu.edu

Johns Hopkins researchers have developed a jelly-like material and wound treatment method that, in early experiments on skin damaged by severe burns, appeared to regenerate healthy, scar-free tissue.

In the Dec. 12-16 online Early Edition of Proceedings of the National Academy of Sciences, the researchers reported their promising results from mouse tissue tests. The new treatment has not yet been tested on human patients. But the researchers say the procedure, which promotes the formation of new blood vessels and skin, including hair follicles, could lead to greatly improved healing for injured soldiers, home fire victims and other people with third-degree burns.

The treatment involved a simple wound dressing that included a specially designed hydrogel—a water-based, three-dimensional framework of polymers. This material was developed by researchers at Johns Hopkins’ Whiting School of Engineering, working with clinicians at the Johns Hopkins Bayview Medical Center Burn Center and the Department of Pathology at the university’s School of Medicine.

Third-degree burns typically destroy the top layers of skin down to the muscle. They require complex medical care and leave behind ugly scarring. But in the journal article, the Johns Hopkins team reported that their hydrogel method yielded better results. “This treatment promoted the development of new blood vessels and the regeneration of complex layers of skin, including hair follicles and the glands that produce skin oil,” said Sharon Gerecht, an assistant professor of chemical and biomolecular engineering who was principal investigator on the study.

Guoming Sun, left, a postdoctoral fellow, and Sharon Gerecht, an assistant professor of chemical and biomolecular engineering, helped develop a hydrogel that improved burn healing in early experiments. Photo by Will Kirk/HomewoodPhoto.jhu.edu

Gerecht said the hydrogel could form the basis of an inexpensive burn wound treatment that works better than currently available clinical therapies, adding that it would be easy to manufacture on a large scale. Gerecht suggested that because the hydrogel contains no drugs or biological components to make it work, the Food and Drug Administration would most likely classify it as a device. Further animal testing is planned before trials on human patients begin. But Gerecht said, “It could be approved for clinical use after just a few years of testing.”

John Harmon, a professor of surgery at the Johns Hopkins School of Medicine and director of surgical research at Bayview, described the mouse study results as “absolutely remarkable. We got complete skin regeneration, which never happens in typical burn wound treatment.”

If the treatment succeeds in human patients, it could address a serious form of injury. Harmon, a coauthor of the PNAS journal article, pointed out that 100,000 third-degree burns are treated in U. S. burn centers like Bayview every year. A burn wound dressing using the new hydrogel could have enormous potential for use in applications beyond common burns, including treatment of diabetic patients with foot ulcers, Harmon said.

Guoming Sun, Gerecht’s Maryland Stem Cell Research Postdoctoral Fellow and lead author on the paper, has been working with these hydrogels for the last three years, developing ways to improve the growth of blood vessels, a process called angiogenesis. “Our goal was to induce the growth of functional new blood vessels within the hydrogel to treat wounds and ischemic disease, which reduces blood flow to organs like the heart,” Sun said. “These tests on burn injuries just proved its potential.”

Gerecht says the hydrogel is constructed in such a way that it allows tissue regeneration and blood vessel formation to occur very quickly. “Inflammatory cells are able to easily penetrate and degrade the hydrogel, enabling blood vessels to fill in and support wound healing and the growth of new tissue,” she said. For burns, the faster this process occurs, Gerecht added, the less there is a chance for scarring.

Originally, her team intended to load the gel with stem cells and infuse it with growth factors to trigger and direct the tissue development. Instead, they tested the gel alone. “We were surprised to see such complete regeneration in the absence of any added biological signals,” Gerecht said.

Sun added, “Complete skin regeneration is desired for various wound injuries. With further fine-tuning of these kinds of biomaterial frameworks, we may restore normal skin structures for other injuries such as skin ulcers.”

Gerecht and Harmon say they don’t fully understand how the hydrogel dressing is working. After it is applied, the tissue progresses through the various stages of wound repair, Gerecht said. After 21 days, the gel has been harmlessly absorbed, and the tissue continues to return to the appearance of normal skin.

The hydrogel is mainly made of water with dissolved dextran—a polysaccharide (sugar molecule chains). “It also could be that the physical structure of the hydrogel guides the repair,” Gerecht said. Harmon speculates that the hydrogel may recruit circulating bone marrow stem cells in the bloodstream. Stem cells are special cells that can grow into practically any sort of tissue if provided with the right chemical cue. “It’s possible the gel is somehow signaling the stem cells to become new skin and blood vessels,” Harmon said.

Additional co-authors of the study included Charles Steenbergen, a professor in the Department of Pathology; Karen Fox-Talbot, a senior research specialist from the Johns Hopkins School of Medicine; and physician researchers Xianjie Zhang, Raul Sebastian and Maura Reinblatt from the Department of Surgery and Hendrix Burn and Wound Lab. From the Whiting School’s Department of Chemical and Biomolecular Engineering, other co-authors were doctoral students Yu-I (Tom) Shen and Laura Dickinson, who is a Johns Hopkins Institute for NanoBioTechnology (INBT) National Science Foundation IGERT fellow. Gerecht is an affiliated faculty member of INBT.

The work was funded in part by the Maryland Stem Cell Research Fund Exploratory Grant and Postdoctoral Fellowship and the National Institutes of Health.

The Johns Hopkins Technology Transfer staff has filed a provisional patent application to protect the intellectual property involved in this project.

Related links:

Sharon Gerecht’s Lab

Johns Hopkins Burn Center

Johns Hopkins Institute for NanoBioTechnology

 

Story by Mary Spiro

Engineers put a new ‘twist’ on lab-on-a-chip

Close-up of a cylindrically-shaped microfluidic device with two fluorescent solutions flowing through. Reproduced with permission from Nature Communications.

A leaf works something like a miniature laboratory. While the pores on the leaf surface allow it to channel nutrients in and waste products away from a plant, part of a leaf’s function also lies in its ability to curl and twist. Engineers use polymers to create their own mini-labs, devices called “labs-on-a-chip,” which have numerous applications in science, engineering and medicine. The typical flat, lab on a chip, or microfluidic device, resembles an etched microscopy cover slip with channels and grooves.

But what if you could get that flat lab-on-a-chip to self-assemble into a curve, mimicking the curl, twist or spiral of a leaf? Mustapha Jamal, a PhD student and IGERT fellow from Johns Hopkins Institute for NanoBioTechnology, has created a way to make that so.

Jamal is the lead author on “Differentially photo-crosslinked polymers enable self-assembling microfluidics,” published November 8, 2011 in Nature Communications. Along with principle investigator David Gracias, associate professor of Chemical and Biomolecular Engineering in the Whiting School of Engineering, and fellow graduate student Aasiyeh Zarafshar, Jamal has developed, for the first time, a method for creating three-dimensional lab-on-a-chip devices that can curl and twist.

The process involves shining ultraviolet (UV) light on a film of a substance called SU-8. Film areas closer to the light source become more heavily crosslinked than layers beneath, which on solvent conditioning creates a stress gradient.

Immersing the film in water causes the film to curl. Immersion in organic solvents like acetone causes the film to flatten. The curling and flattening can be reversed. The result, Jamal said, is the “self-assembly of intricate 3D devices that contain microfluidic channels.” This simple method, he added, can “program 2D polymeric (SU-8) films such that they spontaneously and reversibly curve into intricate 3D geometries including cylinders, cubes and corrugated sheets.”

Members of the Gracias lab have previously created curving and folding polymeric films consisting of two different materials. This new method achieves a stress gradient along the thickness of a single substance. “This provides considerable flexibility in the type and extent of curvature that can be created by varying the intensity and direction of exposure to UV light,” Gracias said.

Gracias explained that the method works with current protocols and materials for fabricating flat microfluidic devices. For example, one can design a 2D film with one type of lab-on-a-chip network, and then use their method to shape it into another geometry, also with microfluidic properties.

Fluorescent image of curved, self-assembled microfluidic device. Reproduced with permission from Nature Communications.

“Since our approach is compatible with planar lithography methods, we can also incorporate optical elements such as split ring resonators that have unique optical features. Alternatively, flexible electronic circuits could be incorporated and channels could be used to transport cooling fluids” Gracias said.

Tissue engineering is among the many important applications for 3D microfluidic devices, Gracias said. “Since many hydrogels can be photopolymerized, we can use the methodology of differential cross-linking to create stress gradients in these materials,” Gracias explained. “We plan to create biodegradable, vascularized tissue scaffolds using this approach.”

Link to the journal article here.

Story by Mary Spiro

 

 

Panel discussion tackles the question: Is undergraduate research for you?

Undergraduates presenting at summer research symposium.

Are you an undergraduate  engineering student who wants to do research but just doesn’t know where to start?

The Johns Hopkins chapter of the Society of Women Engineers  will host a panel discussion Thursday, October 27 at 7 PM in room 132 of Gilman Hall  on the Homewood campus.  The panel discussion is designed to answer your questions about getting started in research at Johns Hopkins University.   Listen to a panel of undergraduate research students in engineering discuss what it’s like to work in an engineering lab.

Undergraduate research experience is extremely important if you want to apply for internships, jobs, scholarships and postgraduate work. Conducting research while you’re an undergraduate also helps put this ideas that you’ve learned in class into action for larger goal. Some undergraduate researchers  even have their work published in peer-reviewed journals.

Johns Hopkins Institute for NanoBiotechnology offers a summer research experience for undergraduates in nano bio.   A criteria for applying to an REU  program is that you have had prior research experience.  Don’t miss your opportunity to learn about this exciting component of your undergraduate academic career.

For more information about the Society of Women Engineers go to http://www.jhu.edu/swe/index.html

For details about  about Johns Hopkins Institute for Nano Biotechnology summer Research Experience for Undergraduates program, go to http://inbt.jhu.edu/education/undergraduate/reu/

Applications for the 2012 summer program will be accepted soon.

Gerecht wins NSF CAREER Award for work in blood vessel formation

Sharon Gerecht (Photo:Will Kirk/JHU)

Sharon Gerecht, assistant professor in Chemical and Biomolecular Engineering at Johns Hopkins University, has been awarded the Faculty Early Career Development (CAREER) Award from the National Science Foundation. The $450,000 prize over five years will help Gerecht in her investigation into how hypoxia, or decreased oxygen, affects the development of blood vessels.

Gerecht’s interdisciplinary research brings together her expertise in stem cell and vascular biology with her background in engineering.  Gerecht said she hopes to discover the mechanisms and pathways involved in the formation of vascular networks, as they relate to embryonic development and diseases such as cancer.

Many medical conditions, such as cancer and heart disease, create areas of decreased oxygen or hypoxia in the spaces between cells. But oxygen is required to maintain normal tissue function by blood vessel networks, which bring nutrients to cells. Likewise, the differentiation of stem cells into more complex organs and structures needs a plentiful supply of oxygen from the vasculature to function.

Gerecht’s study will examine how low oxygen levels impact the growth factors responsible for promoting vascular networks. She also will study the growth of vascular networks in engineered hydrogels that mimic the physical attributes of the extracellular matrix, which is the framework upon which cells divide and grow. Finally, her laboratory will focus on discovering how stem cells differentiate to blood vessel cells and assemble into networks under hypoxic conditions.

She will conduct her research through her role as a project director at the Johns Hopkins Engineering in Oncology Center (EOC), a Physical Science-Oncology Center of the National Cancer Institute. Gerecht is also an associated faculty member of the Johns Hopkins Institute for NanoBioTechnology, which administers the EOC.

Gerecht earned her doctoral degree from Technion – Israel Institute of Technology followed by postdoctoral training at Massachusetts Institute of Technology. She joined the faculty of the Whiting School of Engineering at Johns Hopkins in 2007.

The prestigious CAREER award, given to faculty members at the beginning of their academic careers, is one of NSF’s most competitive awards and emphasizes high-quality research and novel education initiatives. It provides funding so that young investigators have the opportunity to focus more intently on furthering their research careers.

Story by Mary Spiro

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

Drazer wins NSF Career Award

German Drazer

German Drazer (Photo: Will Kirk)

German Drazer, assistant professor in the Department of Chemical and Biomolecular Engineering and affiliated faculty member of Johns Hopkins Institute for NanoBioTechnology was recently named a recipient of the National Science Foundation Faculty Early Career Development (CAREER) awards, given in recognition of a young scientist’s commitment to research and education. Drazer was given the award for “Deterministic and Stochastic Transport of Suspended Particles in Periodic Systems: Fundamentals and Applications in Separation Science.” The grant will support his investigations into the transport phenomena that arise in the motion of suspended particles in spatially periodic systems, and the translation of these phenomena into new principles for the manipulation of suspended particles in fluidic devices.

Read more about the work in the Drazer Lab here.

INBT researchers use LEGO to study what happens inside lab-on-a-chip devices