Sound Idea Could Help Cancer Detection, Diagnosis

The earlier doctors catch cancer, the higher the chance for a cure. 

Researchers at Duke University have heeded that call with a new process of simply running sound waves through blood samples to make diagnosis and treatment quicker and easier.  The system uses sound waves to isolate rare circulating tumor cells (CTCs) from millions of blood cells. This "liquid biopsy" helps in cancer diagnosis, prognosis, and treatment and precision medicine.  

"By studying the CTCs, we can obtain useful information such as the phenotype of tumor cells and, more important, the drug resistance of tumor cells," says Tony Jun Huang, professor of mechanical engineering and materials science at Duke University. MIT and Singapore’s Nanyang Technology University are also participating in the research and development of this system. 

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Biopsies are considered the best way to diagnose cancer, but they can be invasive. This new system developed by researchers could be an easier and quicker alternative, and requires only a blood sample. It could be used to detect the stage and location of cancer, and help doctors choose the course of treatment.  

“Compared with existing techniques, the acoustofluidic CTC separation platform is more gentle with cells and will not change the properties of sorted CTCs,” Huang says.

The system involves running fluid through a tiny channel and passing a sound wave through it. Pressure generated by acoustic waves separates cancer cells, which are larger, from regular blood cells.   

That dynamic occurs because the acoustic wave transports pressure, meaning that when the sound source is vibrating, it pushes the fluid next to it. The pressure generates a force to the cells inside the fluid. Larger cells, or those associated with cancer, are deflected further than smaller ones. The cancer cells are separated by directing them to different outlets using acoustic waves.

This system could be used in breast cancer. An important marker of breast cancer is HER2 (human epidermal growth factor receptor 2), and a pathology biopsy needs to examine HER2 status to tell the doctors whether it is playing a role in the cancer. A typical pathology report identifies the status of HER2, and the treatments between HER2+ and HER2- patients are different. 

"Research has shown that some breast cancers that are HER2+ can become HER2- over time; a HER2- breast cancer can become HER2+ over time. This raises the need to monitor the HER2 status over time through some minimal invasive biopsies, Huang says. “Such situations exist in many types of cancers. That is why we need precision medicine for cancer. This is also why acoustofluidic separation platform can contribute to better cancer diagnosis, prognosis, and treatment.”

The researchers demonstrated the system by using sound waves to separate CTCs from a 7.5-mL vial of blood. The efficiency rate was 86 percent in less than an hour, according to the researchers. Improvements will improve efficiency, and the researchers are working to improve the system’s efficiency and are looking to power it with a low-cost chip to make the test inexpensive.

The system consists of a piezoelectric substrate with metal electrodes and polymer-based microfluidic channels. There is only one FDA-approved commercialized product to isolate alive CTCs, but it is expensive, bulky and needs specialists to operate, Huang says.

"It cannot obtain viable CTCs and is not suitable for many cancer-related applications, such as drug screening tests," Huang sys.

The acoustofluidic CTC separation platform system is still proof-of-concept, but Huang has co-founded a company called Ascent Bio-Nano Technologies to eventually bring the technology to market. 

Agam Shah is the associate editor of Mechanical Engineering magazine.

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