A patch with tiny biodegradable needles that can penetrate the skin may offer an easier, more precise way to test for tuberculosis.
Each year, millions of people in the United States get a tuberculosis skin test to see if they have the infection that still affects one-third of the world’s population. But the standard diagnostic test is difficult to give, because a hypodermic needle must be inserted at a precise angle and depth in the arm to successfully check for the disease.
“With a microneedle test there’s little room for user error, because the depth of delivery is determined by the microneedle length rather than the needle-insertion angle,” says senior author Marco Rolandi, assistant professor of materials science and engineering at the University of Washington. “This test is painless and easier to administer than the traditional skin test with a hypodermic needle.”
A tuberculosis test is a common precautionary measure for teachers, health care professionals, and international travelers. The bacterial infection usually attacks the lungs and can live in an inactive state for years in the body. A diagnostic test involves an injection in a person’s arm. Within two or three days, a swollen, firm bump will appear if an infection is present.
Rolandi and colleagues believe this is the first time microneedles made from biomaterials have been used as a diagnostic tool for tuberculosis. They say their test will be easier to use, less painful, and has the potential to be more successful than the standard tuberculosis skin test.
For the study published in Advanced Healthcare Materials, researchers tested the patch on guinea pigs and found that after the microneedles were inserted using the patch, the skin reaction associated with having a tuberculosis infection was the same as when using the standard hypodermic needle test.
A microneedle patch test has potential as a simpler, more reliable option than the traditional tuberculosis test for children who are needle-shy, or in developing countries where medical care is limited, Rolandi says.
“It’s like putting on a bandage. As long as the patch is applied on the skin, the test is always delivered to the same depth underneath the skin.”
With the standard test, if a hypodermic needle is inserted at the wrong angle, the solution to check for tuberculosis is injected too deep or too shallow into the skin, and the test fails.
Microneedles have been used in recent years as a painless alternative to hypodermic needles to deliver drugs to the body.
The tiny needles on a patch can be placed on an arm or leg, which then create small holes in the skin’s outermost layer, allowing the drugs coated on each needle to diffuse into the body.
Microneedles are made from silicon, metals, and synthetic polymers, and most recently of natural, biodegradable materials such as silk and chitin, a material found in hard outer shells of some insects and crustaceans.
The University of Washington team developed microneedles made from chitin that are each 750 micrometers long, or about one-fortieth of an inch. Each needle tip is coated with purified protein derivative, the material used for testing for tuberculosis. The microneedles are strong enough to penetrate the skin and deliver the tuberculosis test.
The researchers will continue developing the microneedle tuberculosis test and plan to test it next on humans. They also hope to develop different diagnostic tests using microneedles, including allergy tests.
Researchers from the Infectious Disease Research Institute contributed to the study, which was funded by the Coulter Foundation, the UW Center for Commercialization, the Washington Research Foundation, and the Infectious Disease Research Institute.
Source: University of Washington