09:21am Sunday 19 November 2017

New TB test promises to be cheap and fast

Gloved fingers holding microfluidic chip

The small gold spots in this microfluidic chip carry DNA that detects gamma interferon to test for latent TB. The signal can be read through electrodes. (Ying Liu/UC Davis photo)

“Our assay is cheaper, reusable, and gives results in real time,” said Ying Liu, a research specialist working with Professor Alexander Revzin in the UC Davis Department of Biomedical Engineering.

The team has already conducted testing of blood samples from patients in China and the United States.

About one-third of the world’s population is infected with the bacteria that cause tuberculosis, a disease that kills an estimated 1.5 million people worldwide every year, according to the U.S. Centers for Disease Control and Prevention.

Most infected people have latent TB, in which the bacteria are kept in check by the immune system. Patients become sick only when the immune system is compromised, enabling the bacteria to become active. People with HIV are at especially high risk.

Current tests for latent TB are based on detecting interferon-gamma, a disease-fighting chemical made by cells of the immune system. Commercially available tests require sending samples to a lab, and can be used just once.

Liu and Revzin used a novel approach: They coated a gold wafer with short pieces of a single-stranded DNA segment known to stick specifically to interferon-gamma. They then mounted the wafer in a chip that has tiny channels for blood samples. If interferon-gamma is present in a blood sample, it sticks to the DNA, triggering an electrical signal that can be read by a clinician.

“If you see that the interferon-gamma level is high, you can diagnose latent TB,” Liu said.

The researchers plan to refine the system so that the microfluidic sensor and electronic readout are integrated on a single chip.

A patent application has been filed for the technology, and the researchers hope the test can be commercialized after FDA approval. The work was supported by the National Science Foundation.

About UC Davis

For more than 100 years, UC Davis has engaged in teaching, research and public service that matter to California and transform the world. Located close to the state capital, UC Davis has more than 32,000 students, more than 2,500 faculty and more than 21,000 staff, an annual research budget that exceeds $684 million, a comprehensive health system and 13 specialized research centers. The university offers interdisciplinary graduate study and more than 100 undergraduate majors in four colleges — Agricultural and Environmental Sciences, Biological Sciences, Engineering, and Letters and Science. It also houses six professional schools — Education, Law, Management, Medicine, Veterinary Medicine and the Betty Irene Moore School of Nursing.

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