Detection of the doping agent formestane using a spectroscopic ellipsometric method with electrodeposited polydopamine-based molecular imprinting

Abstract

Designer steroids are steroids produced in the laboratory by chemically modifying the steroid backbone to replace anabolic steroids. One of these steroids, formestane (4-hydroxyandrost-4-ene-3,17-dione, FMST), has been added to the list of substances prohibited in sports by the World Anti-Doping Agency (WADA) due to its positive effects in reducing the side effects of other doping steroids. A non-sophisticated yet relatively inexpensive method for detecting these steroids in adulterated dietary supplements is currently unavailable. In this study, for the first time, a spectroscopic ellipsometer (SE)-based sensor using polydopamine (pDA) as a molecularly imprinted polymer (MIP) recognition element was developed for the detection of FMST. FMST detection was achieved in the range of 10 pM-100 nM using MIP-pDA formed on a gold-coated silicon chip by the electropolymerization method. The detection limits (with a 3 sigma noise ratio) determined from the change in the ellipsometric angle Delta spectroscopically in the range of 600-700 nm and directly from the Delta value at a single wavelength were 310 and 382 pM, respectively. The sensor response on the non-imprinted polymer surface remained within noise limits. Recovery rates determined by spiking energy drinks and tablet-form vitamins were found to be greater than 95 %. In reusability tests, the signal obtained after 4 cycles was over 90 %. The usability of the developed MIP-pDA sensor for FMST detection was confirmed, and it was shown that it can be adapted to an SE method for the first time.