Researchers at Worcester Polytechnic Institute (WPI) are developing a biosensor that doctors and nurses can use to quickly detect Clostridium difficile (C. diff), a dangerous and sometimes fatal gastrointestinal infection. The sensor is designed to be the heart of a handheld device that can be used onsite in doctor’s offices and nursing homes, providing results in minutes instead of days, avoiding the need to send samples out to commercial labs, and making it possible to start treatment earlier, when it is likelier to be more successful.
Highly contagious, C. diff is the most common infectious cause of diarrhea in hospitalized patients The bacteria also causes nausea, dehydration, weight loss, colitis, kidney failure, and an increased white blood cell count. The longer treatment is delayed, the sicker patients become and the harder the infection is to cure. C. diff infects more than 500,000 people each year in the United States, of whom more than 29,000 die within 30 days of diagnosis, according to the Centers for Disease Control and Prevention. It is responsible for as much as $4.8 billion per year in health care costs. A major complication of antibiotic therapy, C. diff generally occurs in older adults who have received antibiotics in hospitals or long-term care facilities.
“C. diff is a very serious disease, especially for the elderly,” said Hong Susan Zhou, associate professor of chemical engineering at WPI and principal investigator for the biosensor research program, which is funded by a $350,000 award from the National Science Foundation. “When people are in the hospital and receiving antibiotics, they are very easily infected and it’s very dangerous. When people start having symptoms of diarrhea, it’s not easy tell if it’s C. diff or not. If they can be diagnosed in the early stages, then it’s more easily treated.”
C. diff is typically detected by culturing a stool sample, a test that has a high rate of false negatives, requires specialized equipment and expertise, and cannot be done at most points-of-care facilities. At present, no single commercially available test offers strong sensitivity and portability, as well as rapid turnaround time and low cost. Inexpensive point-of-care diagnostics for C. diff are needed to improve detection, therapy, and treatment cost, Zhou said “Right now, it takes 24 to 48 hours to receive a C. diff diagnosis,” she noted. “People can get much sicker in just that short period of time.”
Starting in 2012, Zhou began looking for a better and faster way to detect C. diff. That research resulted in a microwave-size biosensor prototype, which she built and demonstrated in her lab in 2015. With the current grant, she is working with Yuxiang (Shawn) Liu, assistant professor of mechanical engineering at WPI and co-PI on the project, to shrink the device to make it portable, and to use nanostructures and new microfluidics techniques to make it more sensitive.
The miniaturized biosensor Zhou and Liu are developing uses electrochemical detection (ECD), an extremely selective and sensitive diagnostic technique, which will enable a C. diff infection to be
diagnosed much earlier. The biosensor has an electrode with antibodies attached. When C. diff bacteria bind to the antibodies, they trigger an electrical change that signals the presence of an infection. This process takes just a few minutes, as comparedto the one to two days needed for the traditional lab culture.
The 2015 prototype used gold nanoparticles, laid flat, and a traditional microfluidic platform made of PDMS, a silicon-based organic polymer. That prototype would have been difficult to scale up for mass production, Zhou said. The new device will use 3D gold nanostructures, which have more surface area for the antibodies to adhere to, making the biosensor more sensitive and allowing it to be much smaller than the original prototype.
Liu is developing a new microfluidic platform for the sensor that will enable the stool sample to flow more easily toward the electrode. He is replacing the traditional polymer with an acrylic and will use a laser to cut tiny channels into it. The new platform will be easier to fabricate and to integrate with the new electrode, which Liu also will help fabricate. The goal is to create a reusable handheld biosensor that can make a diagnosis with just a drop of stool, much less than is needed for current lab tests.
It will also be designed to be usable without any special training, making it possible for tests to be conducted on site. “For use in point-of-care facilities, it will be important for it to be easier and less expensive to use,” said Liu.
The technology used in the biosensor can be adapted to test for other types of infectious bacteria, including salmonella, bacterial meningitis, and E. coli. It may even be able to check for cancer biomarkers, Zhou said.
The research team also includes three PhD students: Zanzan Zhu and Zhiru Zhou from Zhou’s lab and Yundong Ren from Liu’s lab. Hanping Feng, a professor at the University of Maryland, will supply the antibodies used in the study.