Modern diagnostic methods are sensitive enough to detect infectious agents at miniscule concentrations, but viruses and bacteria can nonetheless elude containment through sheer attrition – the staggering reproductive rates of infective agents help them spread at breakneck speeds, allowing diseases such as jaundice, measles and dengue fever to create epidemics at the drop of a hat. With their ponderous speed and dependence on costly and uncommon equipment, high-sensitivity assays cannot keep up with the pace set by their target diseases, especially in impoverished regions where the necessary analytical tools might be lacking. Methods that are both rapid and accurate are therefore required to prevent epidemics while they are still in the making, and a joint effort by Drs. Aykutlu Dâna and Utkan Demirci now provides a promising lead.
The core of the new diagnostic assay is a microfluidic chip, loaded with antibodies to selectively capture its target pathogen and bearing a gold-coated surface to allow the SPR-based quantification of ensnared viruses or bacteria. A LED light and a CMOS sensor, required for the excitation and detection or surface plasmons, complete the assembly and create a cheap and portable biosensor. Despite its low cost and simple design, however, the device has what it takes to rival contemporary assays: Tests with GFP-expressing Escherichia coli suggest that the microfluidic chip can detect bacteria at concentrations down to a few dozen cells, and specificity experiments demonstrate that non-target bacteria do not muddle the results. In addition, twenty minutes of incubation is enough to acquire the required data – much shorter than competing assay methods.
Although the team focused on the detection of the relatively benign Escherichia and Staphylococcus, the device in principle can be used for other, more ornery pathogens – such as the foodborne pathogen Salmonella, the opportunistic fungus Candida and common viruses such as HIV, influenza and hepatitis, as well as tropical diseases such as malaria, tuberculosis and dengue fever, the efforts to combat which would benefit greatly from a rapid point-of-care diagnostic technique. Attempts to further enhance the availability and ease-of-use of the device are already underway: Dr. Aykutlu Dâna comments that “[His group] is now working on the miniaturization of SPR platforms, and hopes to achieve miniature multichannel SPR-sensing using a mobile phone in the coming years”.
The research in question has been published in the March issue of the journal Scientific Reports and can be accessed at the following address: