Cancer cells could be weighed in future

Chinese scientists have come up with a new method of weighing microscopic particles such as single atoms or protons, as well as cancer DNA, which could lead to early diagnoses of the disease. A research team led by Zhu Kadi, a professor with the Shanghai Jiaotong University, proposed the optical mass sensing technique to measure the masses of tiny objects, a method which could be several times more sensitive than previous techniques. An article about the research was published earlier this month in Physics Reports, an authoritative international journal. "The technique is still theoretical. We are looking for partners to carry out experiments," said Zhu. Traditional measurement method can only weigh a bunch of atoms, and then estimate the mass of a single atom. "We propose a system consisting of a nanoscale vibrating bar containing an embedded quantum dot and a metal nanoparticle sphere. When a tiny object, such as an atom or a strand of DNA, is placed onto the bar, the extra mass of the tiny object will change the bar's vibration frequency, which could be measured with lasers," Zhu said. "There is no new physical theory being applied. But nobody has thought about the measurement in this way," according to the professor. In recent years, many researchers have been exploring nanotechnologies to create more sensitive measuring instruments, but they have all relied on electrical circuitry to communicate with the sample. "Those techniques cannot be used to measure uncharged particles. For example, the DNA molecules will be destroyed if they are charged," Zhu said. Besides, he explained, electric wires can soak up energy by heating up, and they don't work well at the highest frequencies, where measurements often have the best sensitivity to small changes. "Using lasers, rather than wires, is the key of the new technique," said Zhu. There are many possible applications of the technology, while its use in the early detection of cancer cells could be the most exciting to ordinary people. "The mass of cancer DNA molecules should be different from that of normal ones. So the technology could be used to find these cells," Zhu predicted.