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DIY Biochemical Scanner From a Hacked CD Drive
holy_calamity writes "Turns out hacking two extra light sensors into a CD drive can turn it into a lab scanner to read the results of high-accuracy immunoassays used to detect disease markers or pathogens, New Scientist reports. The drive proved able to detect pesticides at concentrations as low as 0.02 micrograms per liter."
Discode was a project to do an "open source" bio hardware device that sounds very similar to this. The project was going on under the guidance of a UCSD professor and got a lot of write up about three years ago but it seemed to slowly disappear over the years.
I'd be willing to give up my last 5.25" bay if I could use it to give me the secret cheeto powder recipe.
More Twoson than Cupertino
You may think that's supposed to be a joke, but CD lasers are really dangerous. They're labeled safe (Class I ?) on the CD drive because they're inside a closed space. If you remove it from its enclosure it suddenly becomes a very unsafe device to use, especially when you expose the laser. CD lasers are IR, which means your eyes will not blink, and save you, from your eye focusing a collimated beam on the back of your retina. You would quickly go blind. And all this would take place in a fraction of a second.
Then the CD laser can be used as a detection mechanism at different locations along the disk. Also you can obviously run multiple experiments at once, since as the disk spins the laser passes from one fluid channel to the next.
It's a rather cool idea to use commodity CD-drives for these high-tech assays. I'm not aware of a good review of these experiments, but here are two papers on this subject:
Siyi Lai, Shengnian Wang, Jun Luo, L. James Lee, Shang-Tian Yang, and Marc J. Madou "Design of a Compact Disk-like Microfluidic Platform for Enzyme-Linked Immunosorbent Assay" Analytical Chemistry, 76 (7), 1832 -1837, 2004. doi 10.1021/ac0348322
Horacio Kido, Miodrag Micic, David Smith, Jim Zoval, Jim Norton and Marc Madou "A novel, compact disk-like centrifugal microfluidics system for cell lysis and sample homogenization" Colloids and Surfaces B: Biointerfaces Volume 58, Issue 1, 1 July 2007, Pages 44-51 doi: doi:10.1016/j.colsurfb.2007.03.015
It isn't meaningless, but it is a context-less number. Let's try this a different way.
Bob the scientist goes and gets samples from the air, soil, water, and fish at a site. His sensor can go down to 0.02 micrograms of pesticide per liter of sample. When he checks the results he finds the sensor found no pesticide in the air, 0.05 micrograms/L of pesticide in the soil, 0.02 ugrams/L in the water, and 0.15 ugrams/L in the fish.
The context provides the useful part of the data. The soil shows significant levels of pesticide, indicating it was the area directly sprayed. The air sample shows no pesticide to the limit of the sensor so the spraying was done more than a few hours ago. The water is somewhat contaminated but also at the limit of the sensor so it probably isn't that bad as long as there is rain to further dilute the compound. However the fish sample is several times higher than the water or soil sample, implying the pesticide has been used repeatedly and that the ecosystem may start suffering damage.
If the sensor was limited to detecting 10 micograms/L then you couldn't detect the pesticide prior to visible symptoms in the wildlife. By having a more sensitive sensor you have greater lead time to finding problems. For forensic-type activities, it also means it is easier to track down the point source of the pollutant.
I've been on slashdot so long I'm starting to get out of touch with the cool stuff if it ain't on slashdot.
0.02ug/L of protein is what I got from reading the article.
The array can have 300,000 spots of different proteins.
Each spot is at a fraction of a uL volume. The sample must be at 0.02ug/L to be detected.
This is a huge step over commercial applications for a variety of reasons.
First array density
For example I do nucleic acid microarrays (even though the example in the article is protein arrays). We can look at ~30000 samples per array, so the people in the article are able to assess an order of magnitude more information than the system I use, and half an order of magnitude more information than the really expensive systems (for nucleic acids).
The second is sensitivity.
Typical protein assays are done in 96 well plates in the average lab, drug discovery labs may use 3800+ well plates and get results. The advantage of these assays is that the total protein amounts will be on average much higher than in the 300,000 sub uL volume spots printed on the CD that have to be 0.02ug/L or better. So the detection apparatus is actually quite good in the case of the CD detection system.
Third is cost.
The high end nucleic acid systems which are half an order of magnitude worse for sample density cost about 250,000$ for initial equipment costs. Plus more for analysis. The cheaper system that I use ends up using the EXACT same software package they used for downstream processing. CD's are cheaper than custom glass slides.
Fourth is procedural.
A little further customization of the system to make it somewhat fluid tolerant would allow for the drive to also act as a dryer which is achieved currently on glass arrays by buying a special centrifuge. The CD player is the centrifuge.