Microfluidic Chip Can Diagnose Latent Tuberculosis

A microfluidic chip has been developed that can test for latent tuberculosis infection (LTBI) and maybe faster and more reliable than current testing for the disease.

Current tests for LTB are based on detecting the release of interferon-gamma (IFN-γ), a disease-fighting chemical made by cells of the immune system, which commercially available tests require sending samples to a laboratory, and can be used just once.

Biomedical engineers at University of California, Davis (UCD; CA, USA) developed a novel approach for the assay. They coated a gold wafer with short pieces of a single-stranded DNA segment known to stick specifically to IFN-γ. They then mounted the wafer in a chip that has tiny channels for blood samples. If IFN-γ is present in a blood sample, it sticks to the DNA, triggering an electrical signal that can be read by a clinician.

The scientists plan to refine the system so that the microfluidic sensor and electronic readout are integrated on a single chip. An electrochemical biosensor for simple and sensitive detection of IFN-γ will have future applications in immunology, cancer research, and infectious disease monitoring. The team has already conducted testing of blood samples from patients in China and the USA. 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 US Centers for Disease Control and Prevention (CDC; Atlanta GA, USA).

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 infected with the human immunodeficiency virus (HIV) are at especially high risk. Alexander Revzin, PhD, a professor in the UC Davis Department of Biomedical Engineering and his specialist Ying Liu, PhD, added, "Our assay is cheaper than other interferon-gamma release assays, is reusable, and gives results in real time. If you see that the IFN-γ level is high, you can diagnose latent TB."

Related Links:
University of California at Davis
US Centers for Disease Control and Prevention