Fabrication of an electrochemical DNA-based biosensor for Bacillus cereus detection in milk and infant formula

This paper describes fabrication of a DNA-based Au-nanoparticle modified pencil graphite electrode (PGE) biosensor for detection of Bacillus cereus, causative agent of two types of food-borne disease, i.e., emetic and diarrheal syndrome. The sensing element of the biosensor was comprised of gold nanoparticles (GNPs) self-assembled with single-stranded DNA (ssDNA) of nheA gene immobilized with thiol linker on the GNPs modified PGE. The size, shape and dispersion of the GNPs were characterized by field emission scanning electron microscope (FESEM). Detection of B. cereus was carried out based on an increase in the charge transfer resistance (Rct) of the biosensor due to hybridization of the ss-DNA with target DNA. An Atomic force microscope (AFM) was used to confirm the hybridization. The biosensor sensitivity in pure cultures of B. cereus was found to be 10(0) colony forming units per milliliter (CFU/mL) with a detection limit of 9.4 × 10(-12) mol L(-1). The biosensor could distinguish complementary from mismatch DNA sequence. The proposed biosensor exhibited a rapid detection, low cost, high sensitivity to bacterial contamination and could exclusively and specifically detect the target DNA sequence of B. cereus from other bacteria that can be found in dairy products. Moreover, the DNA biosensor exhibited high reproducibility and stability, thus it may be used as a suitable biosensor to detect B. cereus and to become a portable system for food quality control.