Plasmonic nanostructures for multiplex sensing of food toxins

There are a variety of small molecule toxins found in crops that can be extremely carcinogenic to humans, posing dangerous hazards in food production and consumption. This work exploits polymers, with commercially available monomers, as capture agents for various toxins such as mycotoxins. Mycotoxins are small molecule toxins produced from fungi, that contaminate various crops. Detecting mycotoxins traditionally uses specific affinity agents; however, those detection methods are expensive and cannot detect a multitude of toxins at once with one affinity agent. For this reason, we propose the use of a less specific affinity agent, like a linear polymer, to detect classes of mycotoxins. The capture agents can be immobilized on plasmonic substrates known as FONs, or film over nanospheres, based on their end group reactivity whilst maintaining an affinity for a target. These nanostructures induce enhanced Raman signals, are robust, have a long shelf-life with and without an affinity agent, and are compatible for biosensing. By attaching short, anchored polymer chains complexed with the target of interest, these plasmonic surfaces can serve as a novel sensing system when paired with surface-enhanced Raman spectroscopy (SERS). SERS is an attractive analytical signal transduction mechanism due to its high enhancement factors and ability to assign specific vibrational modes to certain molecules, even at very low concentrations. By providing fingerprint spectra for various targets, one can easily detect more than one mycotoxin in relevant complex matrices. Pairing experimental SERS with computational modeling helps confirm hypotheses on binding and target/polymer interaction. Modeling mycotoxins and affinity agents with density functional theory (DFT) allows one to attribute changes in vibrational spectra to particular interactions between the target and polymer. This promotes the use of multiplex detection of various targets in the same class of molecules based on the adaptable nature of the polymer affinity agent. In this talk two mycotoxins: deoxynivalenol and ochratoxin A are modeled with DFT to provide predictive Raman spectra of these small molecules. This work demonstrates optimization of SERS sensing to achieve limits of detection comparable to current detection methods with a simpler and more flexible signal transduction mechanism, providing an opportunity for future applications in complex matrices where these toxins are traditionally found.