Purpose: The objective of this study was to identify carbohydrate ligands that could be used for efficient cell capture.
Methods: Two carbohydrate ligands, F#1 and F#2, were immobilized individually onto magnetic nanoparticles (MNP) which allowed easy suspension in the food matrix and expedient extraction after microbial capture. Following FDA’s Bacteriological Analytical Methods, 25 ml of milk samples initially added with 5 mg MNP were inoculated with varying dilutions of bacterial stock culture. MNP and bacteria were allowed to interact briefly to form MNP-cell complexes and then separated from the milk matrix by applying a magnet to the side of the milk bottle. After supernatant removal, the complexes were re-suspended in 1 ml of fresh milk and plated per BAM procedures. Capture was carried out in vitamin D, 2% and fat free milk for the two different functional ligands and for three bacteria, Salmonella Enteritidis, E. coli O157:H7, and Bacillus cereus, with at least three replicates for each sample and control. All experiments were repeated over a period of several weeks to account for environmental variations. Total number of experiments (n) included in the analysis is greater than 20.
Results: Capture efficiency (CE) for all combinations of milk, functional ligands and bacteria ranged from 73% to 89%. Long-term exposure of the MNP in milk did not markedly influence CE.
Significance: Results show that F#1 and F#2 have the potential as antibody substitutes for bacterial extraction prior to detection.