Competitive binding strategy for reliable signal-off surface enhanced Raman scattering sensing in protecting apples from patulin without external interference

Patulin is a toxin that can be found in damaged or moldy fruits, especially apples. Very high detection sensitivity can be achieved using the SERS (Surface Enhanced Raman Scattering) technique, which provides information about molecular vibrations. However, unexpected desorption of target toxins from the surface of the SERS substrate and interference from other substances pose a major challenge. Here we investigate a competitive binding strategy for reliable SERS analysis of PAT. Core-Raman molecule-shell (CMS) structures and programmable, specific DNA interactions are utilized to regulate Raman signal intensity without affecting the embedded Raman molecules. Specfically, aptamer-functionalized CMS structures are combined with metal-organic scaffold nanoparticles that possess complementary DNA sequences. In the presence of PAT, binding of the aptamer to the toxin leads to degradation of the hybrid nano assembly, which can be measured by a change in the SERS signal. This SERS strategy enables turn-off sensing in apple juice over a wide range (10 pg/mL to 1 μg/mL), with a detection limit as low as 0.02 ng/mL. Analysis of real samples gives results consistent with high-performance liquid chromatography (HPLC) test. The excellent selectivity and sensitivity of the SERS sensor demonstrate its potential for a wide range of SERS sensor applications.