Picture the petri dish, that stalwart icon of biological discovery, sitting unused on the shelf, a mere relic and nearly-forgotten artifact of a laboratory revolution. Nearby, cell cultures proliferate in long, thin chambers encased in transparent resin blocks. Each block is labeled with the name of a patient being treated for a serious disease, each chamber painstakingly calibrated to receive the perfect stream of nutrient solution and experimental medicine. After a few days, the little chambers reveal their secrets under the microscope, and each excited patient receives the right dose of the right drug.
This revolution is being cultivated at Stevens Institute of Technology, where a multi-disciplinary team of scientists and engineers are at the forefront of a field experiencing exponential research growth.
Microfluidic devices (MFDs) promise an entirely new tissue culture protocol that may one day replace the traditional petri dish in labs worldwide. At Stevens, Drs. Woo Lee, Hongjun Wang and Joung-Hyun "Helen" Lee are coordinating a multi-disciplinary effort to develop and fully explore the potential of novel MFD systems. Utilizing the revolutionary devices to support experimental research on other developing technologies at Stevens, especially tissue engineering and inkjet-printed antibiotics, and applications like fighting infection associated with orthopedic implants, the result has been a domino effect of technology breakthroughs that rely and build upon one another.
"Microfluidic devices are ideal for biological studies," says Dr. Lee, George Meade Bond Professor of Chemical Engineering & Material Science. "We have developed entirely new tissue culture protocols and performed the first demonstration of their effectiveness in bone tissue growth."
To support tissue culture experiments, the team designed and fabricated MFDs for their own lab use. The polydimethylsiloxane housings contained 8 channels with dimensions 800 µm width x 200 µm depth x 6 cm length. After the resin molds were formed, they were autoclaved and then seeded with osteoblasts. What happens next reveals the significance of the technology.
Engineers and scientists at Stevens had tried culturing cells in MFDs before, but until they observed truly three-dimensional tissue cultures forming in the channels, they did not know the full potential of the devices for laboratory use. As opposed to static, 2D Petri dish surfaces, microfluidic channels present a realistic environment for cells to grow and adhere in three dimensions. Dynamic fluid motion through the channels mimics real-world conditions previously unrealizable in a lab setting. This leap above the 2D samples grown in traditional tissue evaluation means more relevant results from studies in the lab and better predictions for the results of human testing.
When combining the advanced testing capabilities of microfluidic device technology with other research carried on at Stevens, such as tissue engineering and inkjet-printed antibiotics, the possibilities expand exponentially. Realistic, bone-like tissues can be grown in three-dimensional channels to study and solve conditions like osteoporosis. The life-like nature of the tissues thus engineered could speed up the time that it takes a new drug to reach the market. By inoculating chambers with the tissues from a specific individual, customized cures can be tested and prescribed without conducting trial-and-error treatment on the living person.
"Tissue activity in these 3D cultures more accurately mimics the responses in the human body," says Dr. Wang, Assistant Professor of Biomedical Engineering. "This promises more relevant lab results for studying uses of new pharmaceuticals and comparing the effects of existing drugs on specific human samples."
Although microfluidic technology research has grown exponentially over the past five years, the team's integrated efforts have led to the first demonstration of MFDs used to grow bone tissue models for a scientific experiment. In collaboration with Dr. Jeffrey Kaplan of the New Jersey Dental School, the resulting research team cultured bone tissues, inoculated them with S. epidermis bacteria, and then treated the infections with antibiotics. The clinically-relevant scenario mimics the invasion of pathogens in the body after an orthopedic implant surgery.
In order to get to this advanced research state, the team had to overcome many hurdles not only in the fabrication of the devices, but also in integrating the established process of tissue culture into a novel environment. Dr. Helen Lee's background in electronics microfabrication had familiarized her with phenomena in microenvironments. Tension is high in the narrow microfluidic chambers, which have volumes of 10µL. The flow of fluid through the chambers must be exactingly calibrated. Once initial cell adhesion is confirmed, a flow rate is established strong enough to flush cell waste and replenish nutrients, but not so rapid that the cells themselves are washed away.
"My role was as an integrator, bringing together the tissue engineering process and microenvironment physics," reports Dr. Helen Lee, Research Associate in Chemical Engineering and Materials Science. "Finding the optimum flow condition for experimentation required us to refer to the physiological range and adapt that to the conditions within the devices."
Developing a working system utilizing multiple revolutionary technologies requires a lot of hours in the laboratory. Undergraduates Rachel Kenion and David Monteiro have become critical members of the microfluidic technology team, contributing to both fabricating MFD housings and creating the experimental medical materials that will be put to the test in the new devices.
Kenion is a senior earning dual degrees in Chemistry and Chemical Engineering through a joint program between Stevens and New York University. Using Dr. Woo Lee's innovative inkjet printer, she deposits silver nanoparticles on films that will be exposed to bacteria in microfluidic chambers. She is also growing bacteria from saliva samples to test the efficacy of infection-resistant silver particle applications for orthodontic implants.
With fundamental chemistry Kenion's primary passion, the intriguing applications of this new technology have helped her transition to new technical material in chemical engineering. "There is inherent excitement about taking hard chemistry and finding potential for its application," she says.
While researchers like Dr. Helen Lee painstakingly tweak the conditions within the microfluidic chambers to achieve the desired results, Kenion must also contend with many factors to determine the effectiveness of her inkjet-printed particles. Growing bacteria biofilms from saliva delivers the optimal dose of polymicrobial action that complicates infection-fighting efforts in orthodontic implants. To fight these complicated pathogenic environments, she experiments with nanoparticles printed at different concentrations to define at what level the application kills pathogens without causing harm to human tissues.
As another integral contributor, Chemical Engineering sophomore David Monteiro is mixing, molding, and baking the elastic and reagent concoction that becomes a cutting-edge microfluidic device after a good night's sleep at 70° C. A relatively young scientist in the lab, Monteiro appreciates that the faculty are willing to push him intellectually while also trusting that he will deliver excellent results. He also considers the research to be a great complement to what he learns in traditional classroom lectures.
"Lab opportunities affect your opinions of the discipline," says Monteiro. "They can broaden your horizons and encourage you towards investigations you otherwise might not have followed."
It can be difficult to balance being a full-time student and having commitments in the lab. For the first four days of one experiment, Monteiro took measurements of the fluid expelled from the MFD channels every six hours. He and Kenion agree the rigorous, hands-on lab environment and participation on a collaborative team involved in procedural study enhance their educational experiences.
"Right now, having good grades and participating in extra-curricular activities is not enough to prepare you for a career and the high expectations of industry," says Monteiro. "You also need real exposure to hands-on research."
"We have all really become a team," says Kenion. "Dr. Helen Lee has been extremely helpful not just on a technical level, but also by imparting her knowledge about life in the lab and continuing as a Ph.D. student."
Next on the Horizon: Inket-Printed Antibiotics
As the microfluidic research team moves forward, they look are looking to capitalize on both their unique fabrication techniques as well as detailed knowledge of the specifications for optimal cell growth conditions. Dr. Woo Lee has already been using the devices to test inkjet-printed antibiotics. As a biomedical engineering researcher, Dr. Wang is excited to have this new tool available in the lab, which promises to largely replace the need for animal testing in the development of life-saving biomaterials and medicines. The commercial potential beyond the Stevens campus is staggering, with a paradigm shift in biomedical research in the works here.
Multiple National Science Foundation (NSF) grants have supported the team's research, including current funding in biomaterials research for which Dr. Woo Lee and Dr. Wang are principal investigators. These grants fund not only the material needs of the research, but also allow for undergraduates as well as doctoral students to participate in the important discoveries. Opportunities like this from the NSF therefore enhance educational opportunities at Stevens while developing resources that will save lives in the future. Their collaboration marks a dynamic intersection of research disciplines with far-reading implications for science and society.
"It is a promising project with powerful concepts for the future of medicine and drug delivery," concludes Monteiro. "And it made for a great summer in the lab.