Researchers turn regular DVD player into cheap HIV testing machine

ORIGINAL: Extreme Tech

By Graham Templeton

April 12, 2013

In medicine, having a solution is only half the battle. As we saw with the long and still somewhat ongoing battle against polio, even inventing a cure doesn’t mean you’ve cured a disease; all sorts of confounding variables will inevitably muck with the best laid plans of mice and scientists. With polio, it was a combination of geography, superstition, and cost that kept the disease around for so long, and which keeps it around in some places even today. In fact, it wasn’t until we developed groundbreaking new vaccine preparation technologies, ones that still underpin their mass production, that we started making any real progress at all.

Our war on HIV seems to be progressing along a similar course. Western medicine needed only about fifteen years or so to turn HIV from a death sentence into a debilitating chronic disease, and it spent the ten years after that slowly dialing back the debilitating part. Today, headlines trumpet news of the first people “cured” of the retrovirus, and new preventative initiatives adjust their goals from slowing transmission to halting it entirely. That certainly sounds promising — so why are there still millions of AIDS deaths every year? There’s no one reason, but probably the biggest is simply this: we can’t afford to give everyone the best, most modern treatments.

This is true in North America, let alone in Africa. Despite some truly impressive progress in recent years, particularly with respect to mother-child transmission, new infections are still at 2.5 million, annually. Aid organizations do what they can with the resources they have available, but funding can only go so far. If we want to eradicate HIV to, at least, the extent we’ve managed with polio, we need more than just solutions to the AIDS virus; we need solutions to the AIDS problem.

Probably the most frustrating part of that problem is diagnosis, since early detection and intervention is so vital to survivability. This ought to be easy, at least compared to treating the disease, but it has proven difficult on the ultra-large scale. There have not been too many diagnostic tests that could quickly check thousands of people. This month, however, Nature Photonics brought public attention to a report in Lab Chip that claims a regular old DVD player, with a few basic modifications, could provide quick and accurate tests for HIV — and for many other diseases, as well.

The technology requires three major modifications.

• The first is the addition of a new photodiode, one designed to capture the sort of information we require. There aren’t currently any specifics about just what sort of diode is needed, but they aren’t expensive or difficult to install. Some hot glue and a single wire ought to be enough. 
• After that, we need to modify the player further by loading it up with special lab software; that’s another quick, cheap fix, though one that would seem to require slightly more modern DVD players with more robust internal computers. 
• Finally, we require specialized disposable, multilayer, semi-transparent polymer discs. These custom discs are the only glaring problem with DVD-diagnosis, as they would need to be specially made for binding a specific disease marker. For HIV, this would mean binding the CD4+ helper T-cells, and using their abundance as a reference for the presence of HIV.

Once you’ve got your modded DVD player and custom CD4-binding discs, you’re ready to go.

Loading should be as easy since the setup can take untreated blood straight from a patient, and then the process begins. The DVD reader’s laser shines down through the blood and disc to be recorded by our new photodiode, and as the disc spins we create a record two-dimensional picture of the light that makes its way through to the other side. Thanks to the centrifuge-like spinning of the disc, only bound T-cells should remain to block the transmission of the laser. More dots means more T-cells, means the patient is less likely to carry HIV. That’s not a perfect test, of course, and wouldn’t detect HIV in the absolute earliest stages of infection, but it could still notice drops in T-cell counts months before the patient would otherwise begin to notice health effects.

This technique need not be limited to HIV, but that’s where a dramatic price drop would have the most immediate and powerful effect. Of course, every branch of research will benefit from a low-cost solution to a traditionally cloistered experimental process, especially for seat-of-the-pants assays. We might not be publishing too many papers in Science that rely on DVD assays for proof, but the preliminary research that justifies such high-budget experiments could be made far quicker and cheaper with a $200 basement alternative to flow cytometers, which do much the same job and regularly cost $25,000 or more.

It’s unfortunate that the assay discs must be made anew for each desired target cell or molecule, and it’s currently unclear whether the discs will be reusable. Still, with a purported 1 µm resolution, this tech could revolutionize frontier aid work, and empower researchers everywhere with real, low-cost solutions today.

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