One of the more interesting tissue engineering stories to emerge this past month was the successful finding of a team at Worcester Polytechnic Institute (WPI), which used the veins in spinach leaves as a scaffold that was then recellularized with stem cells that produce heart muscle cells. After three weeks, the transplanted cells showed the ability to contract like the heart does when it beats.
“Proper vascularization of artificial living tissues has been one of the most critical challenges of tissue engineering for decades. This is particularly problematic when the size of the engineered tissue increases.,” said Dongeun (Dan) Huh, PhD, Wilf Family Term Assistant Professor in the Department of Bioengineering at the University of Pennsylvania “This work takes an unusual yet ingenious approach to solving this long-standing problem.”
Below you can watch a short video of some of the investigators on the study talking about it.
When ABC premiered The Six Million Dollar Man more than 40 years ago, the idea of replacing or augmenting human limbs with fully functional biomechanical/biomechatronic versions probably seemed a distant possibility. In fact, the concept had already been in development for decades, but research in this area is only now coming to fruition. Three years ago, researchers in Chicago reported in the New England Journal of Medicine that they had fitted a 31-year-old amputee with a robotic leg that the patient could control with electromyographic, or EMG, signals from salvaged nerves.
Reflecting these developments, undergraduate students in the Department of Bioengineering (BE) have spent the last few weeks developing their own prosthetic devices, although both the mechanics and the “patient” are a bit cruder. Over the course of five lab sessions, these students are creating an “HCMI” — a human-cockroach machine interface that can translate an individual’s own nerve signals into ones that can control a cockroach leg.
The students performing these experiments are enrolled the first of two lab courses that BE students take as juniors. In the George H. Stephenson Foundation Undergraduate Bioengineering Laboratory, the students spend the first few sessions familiarizing themselves with cockroach anatomy. Each group then attaches an individual cockroach leg to a mechanical motor interface, creating a biomechatronic prosthesis, i.e., one that combines electronic, mechanical, and biological systems.
This part of the experiment was considered successful when the students were able to write the letters “BE” with the cockroach leg, using signals generated by computer. This is a more difficult task than it might seem, both because each cockroach leg responds at slightly different frequency-voltage ranges.
Why a cockroach leg?
“They’re easily attainable and easy to deal with,” says Sevile Mannickarottu, who is director of the Stephenson lab. “They’re also relatively large, which makes accessing their legs easy.”
The cockroach’s nervous system is also much simpler than those of birds or mammals, thus simplifying the process of creating the HCMI.
Once the students can write with the biomechantronic device, the final step of the experiment begins. Using human input, students are required to combine two devices to move the prosthetic. One of the devices is an EMG electrode; the other device is up to the student, and it can be a microphone, a motion sensor, or a range of other devices. Working directly with EMG signals is a challenge according to Mannickarottu, who described it as “incredibly noisy and difficult to interpret into meaningful data.”
After choosing their human input device, students send the signals from the device to a computer, which then converts the signal into an EMG signal, which is sent back out to the prosthetic leg. The students tried several different approaches to get the leg to move, including a musical keyboard, a force sensor, and a flex sensor. One group chose to use a Myo armband, a gesture recognition device produced by Thalmic Labs that is commonly used for video games.
With human prostheses and brain-machine interfaces rapidly advancing, overcoming a bit of entomophobia was a worthwhile endeavor for these undergrads.
Six of the students — Zakary Beach, Nicolette Driscoll, Lindsey Fernandez, Jessica Hsu, Jinsu Kim and Ryan Leaphart — are current doctoral students in Bioengineering who earned undergraduate degrees from other top BE programs. Three of the awardees — Lucy Chai, Jake Hsu and Karren Yang — are BE graduating seniors in the Class of 2017. Lucy will spend next year on a Churchill fellowship at Cambridge before starting her NSF fellowship, while Jake has an internship with Genentech‘s Manufacturing Sciences and Technology department, and Karren will attend MIT.
“We are extremely fortunate to attract the very best graduate students in the country,” says David F. Meaney, Solomon R. Pollack Professor and Chair of BE. “This is an external recognition of the high quality of our students across the board.”
The Graduate Research Fellowship Program of the National Science Foundation recognizes and supports outstanding graduate students in NSF-supported science, technology, engineering, and mathematics disciplines who are pursuing research-based master’s and doctoral degrees at accredited United States institutions. For the 2017 competition, the NSF received more than 13,000 applications.
Professor Brian Chow, PhD, who directs the lab in which Ivan works, speaks glowingly of him. “Ivan’s research in the design of de novo proteins for molecular imaging represents a fundamentally new approach to inventing tools for elucidating the physiology of targeted cells. It is completely unchartered territory for mammalian biology and bioengineering,” Dr. Chow says. “What sets Ivan apart as a young scientist is his rare blend of exceptional skills in experimental biology and deep understanding of its mathematical and physical underpinnings. Few possess that blend at his age.”
Every year, the Soros Fellowships are awarded to 30 American students who are either immigrants or the children of immigrants. The field is highly competitive; this year there were almost 1,800 applicants. Ivan and his 29 colleagues will receive up to $90,000 for funding of their graduate educations.