Scientists in the US have taken a step towards faster and more efficient immunoassays for diagnosing HIV and other diseases.

The microfluidic device can monitor interactions between an antigen and its antibody in real time

Richard Zare and colleagues from Stanford University have designed and constructed a new microfluidic device that can monitor immunoreactions - the reaction between an antigen and its antibody - in real time. Using a combination of an immunoassay and surface plasmon resonance imaging (SPR) the device provides a diagnosis in approximately 10 minutes, compared with an hour or more using traditional methods.

Zare's device has several other advantages over other immunoassay methods, including specially designed nanolitre-scale channels that mean a smaller volume of sample is needed. The channels also allow the reagents by the device to be delivered in just one step. The speed comes from the SPR detection method which can monitor antibody-antigen interactions in real-time. SPR measures a refractive change caused by antibodies binding to the antigens on the surface of the array of thin gold spots in the device. Microfluidic devices can potentially be fully automated, meaning samples can be manipulated precisely and efficiently.

Zare believes that, with some further improvements, this combination of immunoassays and SPR in microfluidic devices will have many future applications to real-world problems. 'The results are quite encouraging - so much so that we feel that the prospects for the use of this type of device are quite promising.'

May Copsey