The mass of nanoparticles as small as 10 nanometers in diameter can be determined with attogram precision by measuring the oscillations of a cantilevered nanobeam supporting the particles, researchers report in the Proceedings of the National Academy of Sciences. Furthermore, the particles can be weighed while in solution as they are pumped through a nanochannel inside of the cantilever. Mass determination for naturally occurring and engineered nanoparticles in solution has been difficult for diameters below fifty nanometers, and the challenge is even greater when solution samples contain nanoparticles of various sizes.
This work by Scott Manalis, professor of biological and mechanical engineering at the Massachusetts Institute of Technology, and his colleagues builds on years of research to develop a characterization method that measures decreasingly sized nanoparticles with increasing precision.
Their initial work created micromechanical measuring devices capable of weighing particles in the femtogram range but this progress improves the device’s mass resolution into the sub-attogram range. The improvement is due to a further miniaturization of the “suspended nanochannel resonator” (SNR), in which the resonant frequency of the cantilevered beam is related to the mass supported by the beam. Increasing the possible frequency of oscillations by use of a smaller beam improves the mass resolution.
“This improvement in precision is the difference between weighing a virus and not weighing it,” says Manalis.
One application is the measurement in blood of exosomes, cell-derived molecule-carrying vesicles present in many biological fluids, Manalis says. Knowing that the concentration of exosomes can increase when there’s a cancerous tumor, Manalis proposes that the ability to weigh exosomes one by one could be used to determine how exosome concentration depends on tumor progression. Manalis and his colleagues are now testing the system in the study of patients with glioblastoma, a type of brain cancer.
Manalis is co-founder of Affinity Biosensors, which develops techniques relevant to his research interests for commercial use.