The research described in this proposal details a procedure for detecting and quantifying Illicit Drugs using an immunoassay coupled with surface enhanced Raman scattering (SERS) spectroscopy. The technique has the advantage of high sensitivity due to the use of SERS. In addition, the unique surface sensitive detection of SERS means that the assay can be read without washing away the indicator antigens. This makes it possible to easily automate this method for rapid screening of large numbers of samples in a microwell plate format. The assays will be demonstrated with microwell plates that have been modified with a SERS active colloid. The SERS surface will be treated with anti-illicit drug, dye-tagged drugs, and processed to form a pretreated plate. These will represent part of the commercial product to be developed and will be tested for durability. The analysis will be performed by sample introduction onto the modified microwell plate. Only those drugs that are captured and displace the reporter conjugates on the surface will produce SERS spectra from the microtiter wells. Dye drug conjugates that are not captured are not observed as their spectra are not enhanced by the SERS effect. We will investigate several dye conjugates that have absorptions in the red to enhance the sensitivity of our technique. We will use both a 633 nm HeNe laser system for the analysis. Tests will be made with whole blood, saliva, and perspiration.
Current methods for immunoassay are difficult, time consuming, and require hazardous radioactive reagents. The washing step that we eliminate makes automation difficult in current methods since most samples requires strengent washing to remove the tagged drugs. The technique proposed here will provide a quantitative result without washing and will be very easily automated for large scale rapid analysis. We are proposing to look at illicit drug analysis, however, the methodology can be adapted to all immunoassays.
