Karlinsey’s Research in Microfluidics Aims to Quicken the Diagnosis Time for Physicians
By: Lisa R. Weidman
A patient walks into the physician’s office, flips through a couple magazines in the waiting room, undergoes routine checks with the nurse, and waits a little longer until he finally gets to talk to the doctor. The patient has the symptoms, the physician has her suspicions, but no one has the results–at least not yet. Next the patient pays a visit to the lab to have blood drawn, and results should be available in a week or two later. There’s got to be a better–or at least faster–way to get these results to the patient.
Dr. James Karlinsey, Assistant Professor of Chemistry and a researcher in microfluidics at Penn State Berks, believes that there is a better and faster way, and he has seen the type of results that microfluidics can provide. Using a microfluidic device to perform different steps in the chemical analysis of a finger-prick volume of blood, a diagnosis could be obtained in a matter of minutes–much shorter than the time spent in the waiting room alone.
The field of microfluidics deals with the manipulation of fluids contained in a device that features a network of channels and chambers patterned on a submillimeter (or micro) scale. Many of the techniques used to pattern the features on the device have been adapted from the microchip industry, but Karlinsey is quick to point out that the devices themselves are not nearly as small.
“A typical microfluidic device is about the size of a conventional microscope slide,” Karlinsey describes. “On that device, a single two centimeter long fluidic channel with a width and depth of 0.1 millimeters has a total volume of 200 nanoliters–over a thousand times smaller than a single drop of blood.”
Because all of the processing is done on such a small scale, a smaller sample size is needed and the amount of time required to perform the analysis is significantly decreased.
“Even though the sample amount is greatly reduced, the results are the same,” Karlinsey states. “Results that once took hours or even days to achieve could only take minutes.”
“As you reduce the scale of the fluidic features, you get stronger surface effects because the ratio of surface area to volume increases,” explains Karlinsey. “All of the interesting stuff is happening on the surface because chemistry happens at the surface.”
For this reason, the choice of device material and the nature of the fluid are extremely important. The example Karlinsey provides is a buffer solution containing positively- and negatively-charged ions in a glass device. The positively-charged ions in the buffer line up along the negatively-charged glass walls of the microchannel. When a voltage is applied over the length of the channel, the ions concentrated at the glass surface mobilize and carry the bulk buffer solution from one end of the channel to the other.
This phenomenon is known as electro-osmotic flow and, although it occurs on the “macro”-scale with little significance, it is the predominant behavior on the microscale and the preferred method to control flow in the device.
When it comes to sample type, Karlinsey explains that the most significant applications have been in DNA analysis. Although DNA strands have traditionally been separated using slab gels–a staple in biological and chemical laboratories alike–the same separations can now be performed in microchannels with results obtained in minutes (and sometimes seconds) instead of hours.
Karlinsey’s experience with DNA separations includes analyzing samples for human identification–which he stresses was not nearly as exciting as the popular television show CSI would have you believe–and developing a fully integrated analysis device to detect the presence of anthrax in blood.
The latter project was a collaborative effort that not only brought researchers together, but also brought multiple processing channels and chambers together in a single device. The work, which has been featured in several journals including Science, integrated the extraction of DNA from a crude blood sample, the selective amplification of anthrax DNA, the separation of DNA strands having different sizes, and the eventual detection of anthrax DNA.
The total analysis on the microfluidic device took less than thirty minutes, compared to a conventional analysis that would have taken several days.
“I was extremely excited about the success of the device,” states Karlinsey. “The overarching goal of microfluidic research, from the initial publication–less than twenty years ago–has been to develop a fully integrated device, and I am fortunate to have worked on one of the first.”
Unfortunately, Karlinsey feels we are still several years away from microfluidic devices appearing in our physicians’ offices. “There needs to be a greater focus on the application. Chemists have the ability to manipulate molecules and surfaces, engineers have fantastic devices and models, and biologists and clinicians have a fundamental understanding of the samples of interest. The incorporation of these devices in the office will require communication across the disciplines.”
Karlinsey currently fabricates his devices in plastic, compared to the more expensive glass devices he has used previously. Plastic is cheaper, easier to pattern, and disposable, all of which make it more attractive when developing an application-based device.
When you enter Karlinsey’s chemistry laboratory, you won’t find state-of-the-art equipment. His instrumentation is home-built and his workhorse is a computer-controlled milling machine that he uses to pattern his devices.
“I enjoy designing and fabricating my own devices,” explains Karlinsey. “It’s my chance to be creative, and the creativity aspect is something I enjoy sharing with my research students. I feel that research should be a blend of knowledge, application, and creativity.”
Karlinsey has been conducting research in microfluidics for the last eight years, two of which have been spent at Penn State Berks, and often involves students in his projects.
“As a sophomore at Penn State Berks, working with Dr. Karlinsey in microfluidics has been a wonderful hands-on learning experience,” comments Binayah Shaparenko, a sophomore majoring in Life Science. “Dr. Karlinsey’s approach makes comprehending new concepts of analytical chemistry both fun and exciting. Through undergraduate research, I have been able to increase my knowledge of the sciences in a laboratory setting.”
Annie Davis, a junior majoring in Biology, adds, “In the fields of chemistry and biology, microfluidics is really in its infancy and it is an incredible feeling to know that I am working on a project that can help improve the efficiency of chemical analysis.”
While he is currently working on devices that feature a combination of electro-osmotic flow and pump-driven flow (using a series of integrated valves), Karlinsey has bigger plans for his microfluidic interests.
“Only after you demonstrate that you can reliably move samples from one reaction chamber to another through a network of channels can you achieve a fully-integrated analysis device.”
Hopefully it won’t take much longer–patients are waiting.