Porous silicon based photoluminescence immunosensor for rapid and highly-sensitive detection of Ochratoxin A

A rapid and low cost photoluminescence (PL) immunosensor for the determination of low concentrations of Ochratoxin A (OTA) has been developed. This immunosensor was based on porous silicon (PSi) and modified by antibodies against OTA (anti-OTA). PSi layer was fabricated by metal-assisted chemical etching (MACE) procedure. Main structural parameters (pore size, layer thickness, morphology and nanograins size) and composition of PSi were investigated by means of X-Ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. PL-spectroscopy of PSi was performed at room temperature and showed a wide emission band centered at 680 ± 20 nm. Protein A was covalently immobilized on the surface of PSi, which in next steps was modified by anti-OTA and BSA in this way a anti-OTA/Protein-A/PSi structure sensitive towards OTA was designed. The anti-OTA/Protein-A/PSi-based immunosensors were tested in a wide range of OTA concentrations from 0.001 upto 100 ng/ml. Interaction of OTA with anti-OTA/Protein-A/PSi surface resulted in the quenching of photoluminescence in comparison to bare PSi. The limit of detection (LOD) and the sensitivity range of anti-OTA/Protein-A/PSi immunosensors were estimated. Association constant and Gibbs free energy for the interaction of anti-OTA/Protein-A/PSi with OTA were calculated and analyzed using the interaction isotherms. Response time of the anti-OTA/Protein-A/PSi-based immunosensor toward OTA was in the range of 500–700 s. These findings are very promising for the development of highly sensitive, and potentially portable immunosensors suitable for fast determination of OTA in food and beverages.