NRL developed the Microassay on a Card (MAC), which is a portable, handheld, noninstrumental immunoassay that can test for the presence of a wide variety of substances in the environment.

The MAC assay card

The MAC assay card.

The MAC is a simple device to use. A drop of test solution is placed on one side of the card and within minutes a color is developed on the other side in proportion to the amount of substance in the test solution. The MAC is self-contained and self-timed; no reagents or timing are necessary. The MAC can be configured with multiple wells to provide simultaneous testing for multiple species.

MAC's advantages include:

  • rapid and sensitive response: completed in under five minutes with nanogram- per-milliliter sensitivity;
  • a visible positive result: a color develops, indicating the presence of a substance;
  • designed for field use: the dry chemistry requires only the test solution;
  • no instrumentation required;
  • results remain permanent for up to one year; and
  • no toxic or corrosive reagents are used.

As envisioned, the MAC could be used as an on-site screen for drugs of abuse in urine or saliva. It could also be used for on-the-job drug testing and identifying seized solid materials. Other applications include tests for pregnancy, surveys for environmental contaminants (pesticides), and diagnostics for disease organisms (toxins).