Effectiveness of nanoparticle-bound ampicillin in the treatment of Listeria monocytogenes infection in athymic nude mice.

The effectiveness of nanoparticle-bound ampicillin was tested in the treatment of experimental Listeria monocytogenes infection in congenitally athymic nude mice. Nanoparticles of polyisohexylcyanoacrylate (PIHCA) 187 +/- 13 nm in diameter were bound to ampicillin at an ampicillin/PIHCA ratio of 0.2:1. The proportion of ampicillin bound was 90% +/- 3%. After adsorption onto nanoparticles, the therapeutic activity of ampicillin increased dramatically over that in the free state. Thus, 2.4 mg of nanoparticle-bound ampicillin (three doses of 0.8 mg each) had a greater therapeutic effect than 48 mg of free ampicillin (three doses of 16 mg each). These results might provide an incentive for further development of intracellular targeting of antibiotics on biodegradable polymeric carriers.