Figure 1. Generation and characterization of Listeria monocytogenes (Listeria)-³²P.

(A) Incorporation of ³²P into Listeria. Listeria was starved in saline and then cultured in phosphate free medium plus ³²P. (Incorporation of ³²P into Listeria = ³²P in Listeria pellet/³²P in Listeria pellet plus supernatant × 100%). (B) Viability of Listeria-³²P. After incorporation of ³²P into Listeria the viability of Listeria was compared to Listeria untreated (Viability of Listeria-³²P = CFU of Listeria-³²P/CFU of untreated × 100%). (C) Infection rate of tumor cells. Infection of Panc-02 tumor cells with Listeria-³²P was compared to Listeria untreated. The number of CFU per well after 1 hr of infection was determined. The error bars represent SEM. Each dot represents one experiment. Unpaired t test *p = 0.0123 (D) Stability of Listeria-³²P. The stability of Listeria-³²P in serum was analyzed by incubating Listeria-³²P with serum at 37°C. After 0, 1, and 3 h, the Listeria-³²P bacteria were centrifuged, and the supernatant was analyzed for radioactive counts. The dissociation grade (percent) of the Listeria-³²P complex was determined by dividing free radioactivity in the supernatant and baseline radioactivity (total radioactivity incorporated ³²P into the Listeria plus free ³²P in the supernatant). Data shown are the average of one experiment with n = 3 samples per time point. The error bars represent SEM.