Silica nanoparticles more effectively deliver bacteria killing nitric oxide

Mark Schoenfisch and his lab of analytical chemists at UNC have created nano-scale scaffolds made of silica and loaded with nitric oxide (NO) which can be released in a precisely controlled way. Nitric Oxide can be used to kill bacteria.

Schoenfisch, Hetrick and their colleagues tested their silica scaffolds head-to-head with small molecules against the bacteria Pseudomonas aeruginosa, which is commonly found in burn and other wound infections.

NO delivered by both methods completely killed the bacteria. But the silica nanoparticles delivered the NO right to the bacteria’s doorstep. In contrast, the small molecules released NO indiscriminately, and the concentration of NO is lost as it makes its way toward bacterial cells.

“With the silica particles, more NO actually reached the inside of the cells, enhancing the efficacy of the nanoparticles compared to the small molecule. So, the overall amount of NO needed to kill bacteria is much less with silica nanoparticles,” Schoenfisch said. “And, with small molecules, you’re left with potentially toxic byproducts,” Schoenfisch said. Using mouse cells, they proved that the silica nanoparticles weren’t toxic to healthy cells, but the small molecules were.

Future research will include studying additional bacterial strains, active targeting, preferential uptake and biodistribution studies.

Safer Light-Activated Nanoparticle Cancer Therapy

Oncologists have long suspected that photodynamic therapy could find broader use if only there was some way to limit the accumulation of photosensitizer molecules to tumors, sparing healthy tissue from unintended damage. Now, using modified silica nanoparticles, a team of investigators at the State University of New York, Buffalo, has developed a photosensitizer delivery method that has the potential to target tumor cells specifically.

His group has used porous silica nanoparticles modified in such a way as to form a strong chemical bond between the nanoparticles and the photosensitizer molecules. When exposed to light, the permanently entrapped photosensitizer still produces reactive oxygen molecules that can diffuse out of the nanoparticles through their porous silica shells.

The investigators found, too, that human colon cancer cells readily take up the photosensitizer-loaded nanoparticles. More importantly, shining light on these cells resulted in their death.