Based on molecular beacon recognition and nanoparticles labeling technique, we constructed a sensitive detection method for target DNA of Listeria monocytogenes in homogeneous system. Using FITC-IgG complex as nuclear materials, FITC-IgG@SiO₂ core/shell fluorescence nanoparticles were successfully synthesized. It effectively prevented the disclosure of FITC in traditional preparation process. Then the prepared fluorescence nanoparticles and Au nanoparticles were used to label 5 and 3 end of L. monocytogenes sequence-specific molecular beacon probe, respectively. The molecular beacon-fluorescent nanoparticles probe was successfully constructed. Under the optimized conditions, it was found that the fluorescent intensity is proportional to the concentration of target DNA of L. monocytogenes over the range of 1～200 pmol/L with a detection limit of 0.3 pmol/L (3S/N), and the relative standard deviation is 2.6% (50 pmol/L, n＝11). The proposed method was applied to detect L. monocytogenes in food samples, the results obtained are identical to that of by an official standard method.

Key words: FITC-IgG@SiO₂ fluorescent nanoparticle, gold nanoparticle, molecular beacon, Listeria monocytogenes, DNA hybridization