The nano=scaled tweezers could be used to detect pathogens and early stages of diseases such as Alzheimer's. (Image Credit: Justus Ndukaife, Vanderbilt University)


Today's optical tweezers, which use a highly focused laser beam to trap and move micron-scale objects, can't grip anything smaller than a red blood cell. Engineers at Vanderbilt University have developed opto-thermal-electrohydrodynamic tweezers (OTET) that are capable of manipulating DNA molecules and proteins without causing damage to them. This improvement to the technology could be beneficial in the health field, allowing earlier detection of diseases like Alzheimer's.


Micron-scale optical tweezers exhibit a significant advancement in biological research, but they can only work with objects of a certain size. This is due to the laser beam functioning as the pincer of an optical tweezer. It's capable of focusing laser light to a specific diameter. For instance, red light has a wavelength of 700 nanometers, which allows the tweezers to focus on and manipulate objects that have a diameter of 350 nanometers or larger using low power. However, 350 nanometers are very small, which means that other tiny molecules like viruses (100 nanometers), DNA and proteins (10 nanometers) cannot be picked up by these tweezers.


The team demonstrated a technique with OTET that left several microns between the laser beam and the molecule the tweezers isolated. "We have developed a strategy that enables us to tweeze extremely small objects without exposing them to high-intensity light or heat that can damage a molecule's function," Justus Ndukaife, assistant professor of electrical engineering said. "The ability to trap and manipulate such small objects gives us the ability to understand the way our DNA and other biological molecules behave in great detail, on a singular level."


Before OTET, molecules like extracellular vesicles were trapped by using high-speed centrifuges. However, it was too expensive to use it in a wide range of applications. These new, tiny tweezers could be used by scientists with a smaller budget. OTET is also capable of sorting objects based on size, which is important when looking for specific exosomes, extracellular vesicles hidden by cells that cause cancers to metastasize. It has been challenging to study and sort specific exosomes, which range from 30 to 150 nanometers.


OTET could also be used to detect pathogens by trapping viruses for observation and research proteins that contribute to neurodegenerative diseases like Alzheimer's. These applications could detect disease early since these tweezers are capable of capturing low levels of molecules. This means a disease doesn't have to be full-blown before disease-causing molecules can be researched. OTET can also be combined with spectroscopy and biofluorescence.


"The sky is the limit when it comes to the applications of OTET," said Ndukaife, who collaborated with the Center for Technology Transfer and Commercialization to file a patent on this technology. "I am looking forward to seeing how other researchers harness its capabilities in their work."


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