Researchers at the University of Colorado have developed a new rapid test for sickle cell disease. Their tiny device is less than the size of a quarter, and can provide a result in as little as one minute. The technology uses ultrasound to heat a protein sample and then measures how it dissolves over time to identify the protein responsible for sickle cell disease. Relatively inexpensive and requiring only a simple camera (such as those on a smartphone), a power source and a microscope, the technology could be suitable for use in low-resource regions.
“In Africa, sickle cell disease is the cause of death in 5% of children under 5-years-old for lack of early diagnosis,” said Angelo D’Alessandro, a researcher involved in the study. “This common, life-threatening genetic disorder is most prevalent in poor regions of the world where newborn screening and diagnosis are rare.”
The disease is caused by a variant of hemoglobin that causes red blood cells to assume a crescent shape. However, one way to identify the culprit protein is to measure its solubility at specific temperatures, as it will behave differently when heated compared with regular hemoglobin.
“Almost all life activities involve proteins,” said Xiaoyun Ding, another researcher involved in the study. “We thought if we could measure the protein thermal stability change, we could detect these diseases that affect protein stability.”
One way to analyze proteins in a sample disease is to heat a sample and measure protein solubility over time using a technique called a Thermal Shift Assay (TSA). However, the assay can take a whole day to run, and requires cumbersome and expensive equipment.
“The traditional methods for thermal profiling require specialized equipment such as calorimeters, polymerase chain reaction machines and plate readers that require at least some technical expertise to operate,” said Kerri Ball, a third researcher involved in the project. “These instruments are also not very portable, requiring samples to be transported to the instruments for analysis.”
Called an Acousto Thermal Shift Assay (ATSA), the new device uses ultrasound waves to heat a sample, and is smaller, cheaper, faster and more sensitive than conventional TSAs. “Our method is seven to 34 times more sensitive,” said Ding. “The ATSA can distinguish the sickle cell protein from normal protein, while the traditional TSA method cannot.”