Remote sensing of Salmonella-specific DNA fragment by using nanoporous alumina modified with the single-strand DNA probe

Foodborne Salmonella disease is a major public health concern. Therefore, it is crucial to design a reliable biosensor to the diagnosis of this disease. Herein, we fabricated an interferometric reflectance spectroscopy (IRS) based DNA sensor for the determination of Salmonella-specific DNA fragment concentration. For this purpose, the nanoporous anodic alumina (NAA) was first fabricated. The pore walls of NAA were then functionalized with 3-aminopropyl tri-methoxy silane (NAA-NH2). After that, the amino-terminated single strand DNA(sal) (ssDNA(sal)) probe was immobilized on NAA-NH2 by the use of glutaraldehyde (Glu) as cross-linker. To detect the amount of Salmonella-specific DNA fragment, the different concentrations of Salmonella-specific DNA fragment were pumped to the analytical flow cell. Subsequently, methylene blue (MB) was pumped to the analytical flow cell to intercalate between guanine-cytosine base pairs. The intercalated MB into double-strand DNA absorbed the transferred white light to the DNA sensor and therefore, the intensity of the reflected light from the DNA sensor to the charge-coupled device detector decreased. The decrease in the intensity of the reflected light consequent on the decrease in the peak area of the IRS in the wavelength range of 450-1050 nm (peak area(450-1050 nm)). The decrease in the peak area(450-1050) (nm) had a good linear relationship with the concentration of Salmonella-specific DNA fragment in the range of 0.25-50.0 nM. The limit of detection was found to be 0.01 nM. The fabricated DNA sensor had a good selectivity to Salmonella-specific DNA fragment in the presence of Staphylococcus aureus-specific DNA fragment and Escherichia coli-specific DNA fragment.