Liviu Movileanu, Ph.D., assistant professor in the structural biology, biochemistry, and biophysics program at Syracuse University, talked about his group’s work with nanopores at the meeting. Using a combination of techniques from nanotechnology, biomolecular engineering, and surface chemistry his team is developing a chip platform for analysis of biomolecules. The sample-prep approaches previously discussed all depend on miniaturizing, automating, or simplifying the process. Dr. Movileanu said that sample prep can be effectively bypassed using an extremely sensitive detection method based on nanopores.
Natural ion channels that transport charged molecules through a potentiated membrane inspired the concept behind Dr. Movileanu’s research. Increasing understanding of the mechanisms of ion channels, and the ability to measure the current running through them, have enabled scientists to replicate them in the laboratory by creating nanometer-scale holes in a silicon nitride membrane.
When placed in an electrolyte solution with voltage across the membrane, these holes behave similarly to a natural ion channel. More importantly, the current measured when an analyte passes through a nanopore positively identifies that analyte—a technique called stochastic sensing.
“This is a technique for probing very minute, small quantities of biologic material, in this case, proteins or nucleic acids. It’s called stochastic sensing because each molecule interacting with a single nanpore will cause a current blockade. The nature of that current blockade is stochastic. The technique allows quantification, as well as identification of the analyte,” said Dr. Movileanu.
Applications for stochastic sensing include DNA sequencing and protein detection. For example, it’s possible to modify the nanopores for studying aptamers. Then, when the proteins bind to the aptamers, they create a current blockade that detects the presence of the proteins.
Microscale fabrication plays an important role in this year’s crop of sample-prep innovations. Smooth surfaces, high-tech materials, and precision design make it possible to fit an entire workflow on a chip, cartridge, or handheld device. Innovative approaches to filtration and concentration can bridge the gap between the real world and the microworld on the chip.
Although the end-user applications can be extremely different, sample-prep technologies overlap significantly between environmental, biodefense, and medical research fields. For this reason, biological researchers have benefitted tremendously by investment in sample-prep technologies for biodefense applications.