Viruses, bacteria, and nanoparticles are used to deliver DNA to cells. But when used in the body, each delivery vehicle has its limitations. Nanoparticles have the advantage of delivering large copy numbers of DNA molecules. But because of their size and limited targeting ability, they cannot access tissues effectively and thus have a poor efficiency.
Bacteria, on the other hand, are inefficient DNA carriers that can hold only one copy of the DNA cargo per cell. However, bacteria are active microorganisms and can penetrate solid tumors—particularly tricky tissue for passive viral or nanoparticle vectors to access, explains Bashir.
Now, Akin et al. have developed a system whereby active bacteria carry nanoparticles as cargo, thus yielding the benefits of both previous systems. The team calls them microbots.
Microbots delivered DNA-covered nanoparticles with high efficiency into a variety of cancer cell lines in culture and into mouse organs in vivo. Microbot-managed gene expression was much stronger that that achieved by either system alone, and the efficiency of transfection in cell lines was found to be twice as high.
The team is now planning to knock out the pathogenic genes of the carrier bacteria they use to make these microbots safe and to limit their infectivity to specific tissue locations, such as tumors.