With the move toward a post-antibiotic world, scientists have pushed to find alternative treatments for infection that don't involve antibiotics. Progress has been made with viruses called bacteriophages, which hijack the bacteria's inner machinery and cause it to burst like a balloon. Other work has been done with bacteria-made toxins (bacteriocins) to kill off infection-causing bacteria. The advances that most closely relate to ninja particles are therapies involving cationic or antimicrobial peptides. These molecules also can selectively target bacteria due to opposite attraction of charges on their surfaces. Their method of killing the bacterial cells is rooted in disruption of communication between cells [source: Borel]. This therapy, however, has been plagued with several issues: toxicity for healthy, nonbacterial cells (for example, mammalian cells may rupture and release their contents); short half-life in vivo (they don't last very long in the body) and high manufacturing costs [source: Nederberg et al].
Ninja particles solve a lot of these problems. They are compatible with blood, having minimal to no toxicity to red blood cells; are stable enough to remain effective in vivo; biodegrade easily and are orders of magnitude cheaper to make. Ninja particles aren't the only bacteria fighting particles out there. Researchers across the world have been making similar strides developing other small molecules with antimicrobial properties or creating nanoparticle-based approaches to drug delivery [sources: Zhu and Gao]. These particles join a growing community of nanoparticle-based therapies. Nanoparticles are used in medicinal applications such as medical imaging (like MRI) and in treatment of a wide range of diseases like cancer and AIDS.