Diagnosis on Earth is a fairly simple procedure, done at any hospital or medical center. In space flight, however, where doctors and even basic medical equipment may be lacking, falling ill is a serious matter for both astronaut and ground control. Using horseshoe crab blood as a reactive agent, the Lab-On-a-Chip Application Development-Portable Test System (LOCAD-PTS) is a handheld device developed by NASA researchers to help identify microorganisms. Ginger N. Flores is the LOCAD project manager.
NASA Tech Briefs: How does LOCAD-PTS work, and why was it developed?
Ginger N. Flores: It is, basically, a portable, handheld device that uses interchangeable cartridges that can detect a variety of biological and, in the future, chemical, molecules. The handheld device itself consists of a spectrophotometer, a heating block, pump, and associated electronics and microprocessors. The cartridges are about half the size of a credit card. They each contain four channels that are linked to four "sample wells" that receive the sample. In each channel a dried reagent or formulation for the detection of a particular molecule. For example, the channels of the cartridges we sent just recently to the ISS contain a formulation called Limulus amebocyte lysate, or LAL. LAL reacts with lipopolysaccarides of bacteria, also known as endotoxins. And we couple the LAL reaction to the generation of a yellow dye, and so the more intensity or the more yellow color that is detected by the device, the more litho-polysaccharide is present. That's how it works in a nutshell. Future cartridges will contain different formulations and be able to detect for different biological or chemical molecules.
As to why it was developed, LOCAD-PTS is very sensitive, and it's a very good, overall test for microbial cleanliness. It is part of the Advanced Environmental Monitoring and Control project (AEMC), and that is funded under the Exploration Technology Development Program (EDTP) by the overall exploration systems mission directorate. LOCAD-PTS has been derived from a commercial, off-the-shelf technology produced by Charles River Laboratories and then modified for space flight by the LOCAD team here at Marshall. The collaboration also includes scientists at the Carnegie Institute of Washington, and they coupled with our principle investigator to test the device in parabolic flight and other extreme environments. They've taken it to the Arctic, and also, they've used it in the Aquarius underwater habitat in the Florida Keys during NASA's NEMO mission.
NTB: How does it use horseshoe crab blood, and why was that substance chosen?
Flores: The horseshoe crab has a very primitive, but very effective, immune system, which protects the crab from microbial infection. The active player in that immune system is the blood cells, which are known as amebocytes. Back in the 1960s, it was found that an extract from those blood cells, which is LAL, could be used for very sensitive detection of the lipopolysaccarides/endotoxins. This is called the LAL assay' it's pretty widespread in molecular biology and also it is important in the medical field for the monitoring of cleanliness, specifically of injectable fluids. But it can be time-consuming; it can take hours or even days, and it can also be hazardous, because you have to use pure endotoxins as controls. So Charles River Laboratories developed the PTS part of LOCAD-PTS to reduce the assay time and also to miniaturize the whole process so that you can take it outside of the lab. The LAL test is proven. This is the reason that the LAL cartridge was the first to be chosen to do the first test that we will be performing on ISS.