Biochip may make diagnosis of leukemia and HIV faster, cheaper

Inexpensive, portable devices that can rapidly screen cells for leukemia or HIV may soon be possible thanks to a chip that can produce three-dimensional focusing of a stream of cells, according to researchers.

An assembled flow cytometry chip with size comparable to a U.S. Quarter. (Credit: Tony Huang)

"HIV is diagnosed based on counting CD4 cells," said Tony Jun Huang, associate professor of engineering science and mechanics at Penn State. "Ninety per cent of the diagnoses are done using flow cytometry."

Huang and his colleagues designed a mass-producible device that can focus particles or cells in a single stream and perform three different optical assessments for each cell.

They believe the device represents a major step toward low-cost flow cytometry chips for clinical diagnosis in hospitals, clinics and in the field.

"The full potential of flow cytometry as a clinical diagnostic tool has yet to be realised and is still in a process of continuous and rapid development," the team said in a recent issue of Biomicrofluidics. "Its current high cost, bulky size, mechanical complexity and need for highly trained personnel have limited the utility of this technique."

Flow cytometry typically looks at cells in three ways using optical sensors. Flow cytometers use a tightly focused laser light to illuminate focused cells and to produce three optical signals from each cell. These signals are fluorescence from antibodies bound to cells, which reveal the biochemical characteristics of cells; forward scattering, which provides the cell size and its refractive index; and side scattering, which provides cellular granularity. Processing these signals allows diagnosticians to identify individual cells in a mixed cell population, identify fluorescent markers and count cells and other analysis to diagnose and track the progression of HIV, cancer and other diseases.