Tiny labs that fit in your hand can quickly identify pathogens using electricity

When you think of electric fields, you probably think of electricity—the stuff that makes modern life possible, powering everything from household appliances to cell phones. Researchers have been studying the principles of electricity since the 17th century. Benjamin Franklin, famous for his kite experiment, showed that lightning was actually electrical.

Electricity has also enabled major advances in biology. A technique called electrophoresis allows scientists to analyze the molecules of life – DNA and proteins – by separating them based on their electrical charge. In addition to being commonly taught in secondary school biology, electrophoresis is a workhorse in many clinical and research laboratories, including mine.

I am a professor of biomedical engineering and work with miniaturized electrophoretic systems. Together with my students, my students are developing portable versions of these devices that quickly detect pathogens and help researchers combat them.

What is electrophoresis?

Researchers discovered electrophoresis in the 19th century by applying an electrical voltage to clay particles and watching them travel through a layer of sand. After further advances in the 20th century, electrophoresis became the standard in laboratories.

To understand how electrophoresis works, we first need to explain electric fields. These are invisible forces that electrically charged particles such as protons and electrons exert on each other. For example, a particle with a positive electrical charge would be attracted to a particle with a negative charge. The law “opposites attract” applies here. Molecules can also have a charge; Whether it is more positive or negative depends on the type of atoms that compose it.

During electrophoresis, an electric field is created between two electrodes connected to a power supply. One electrode is positively charged and the other negatively charged. They are positioned on opposite sides of a container filled with water and some salt, which can conduct electricity.

When charged molecules such as DNA and proteins are present in water, the electrodes between them create a force field that pushes the charged particles toward the oppositely charged electrode. This process is called electrophoretic migration.

Researchers value electrophoresis because it is fast and flexible. Electrophoresis can help analyze different types of particles, from molecules to microbes. Additionally, electrophoresis can be performed using materials such as paper, gels, and thin tubes.

In 1972, physicist Stanislav Dukhin and his colleagues observed a different type of electrophoretic migration, called nonlinear electrophoresis, which could separate particles based not only on their electrical charge but also on their size and shape.

Electric fields and pathogens

Further advances in electrophoresis have made it a useful tool for combating pathogens. In particular, the microfluidics revolution has enabled the emergence of tiny laboratories that allow researchers to quickly detect pathogens.

In 1999, researchers found that these tiny electrophoresis systems could also separate intact pathogens through differences in their electrical charge. They placed a mixture of different types of bacteria in a very thin glass capillary, which was then exposed to an electric field. Some bacteria left the device faster than others due to their different electrical charges, allowing the microbes to be separated by type. Measuring their migration speed allowed the scientists to identify each species of bacteria present in the sample in a process that took less than 20 minutes.

Microfluidics has improved this process even further. Microfluidic devices are small enough to fit in the palm of your hand. Their miniature size allows them to perform analyzes much faster than traditional laboratory equipment because the particles do not have to travel as far through the device for analysis. This means that the molecules or pathogens researchers are looking for are easier to detect and less likely to be lost in analysis.

For example, samples analyzed with traditional electrophoresis systems would need to be transported through capillary tubes approximately 11 to 31 inches (30 to 80 centimeters) long. Processing can take 40 to 50 minutes and is not portable. In comparison, samples analyzed with tiny electrophoresis systems travel through microchannels that are only 1 to 5 centimeters long. This means small, portable devices with analysis times of around two to three minutes.

Nonlinear electrophoresis has enabled more powerful devices by allowing researchers to separate and detect pathogens based on their size and shape. My lab colleagues and I have shown that by combining nonlinear electrophoresis with microfluidics, not only different types of bacterial cells, but also living and dead bacterial cells can be separated.

Tiny electrophoresis systems in medicine

Microfluidic electrophoresis has the potential to be useful across industries. First and foremost, these small systems can replace traditional analytical methods with faster results, greater convenience and lower costs.

For example, when testing the effectiveness of antibiotics, these tiny devices could help researchers quickly see whether pathogens are killed after treatment. It could also help doctors decide which drug is best for a patient by quickly distinguishing between normal bacteria and antibiotic-resistant bacteria.

My lab is also working on developing microelectrophoresis systems to purify bacteriophage viruses that can be used to treat bacterial infections.

As development continues, the power of electric fields and microfluidics can accelerate how researchers can detect and combat pathogens.