Microbots deliver the goods

Microbots deliver the goods B y combining two not-so-effi cient DNA delivery systems into one, Demir Akin, Rashid Bashir (Purdue University, Indiana), and colleagues have engineered super effi cient, DNA-delivering “microbots.” 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 effi ciency. Bacteria, on the other hand, are ineffi cient 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 benefi ts of both previous systems. The team calls them microbots. Microbots delivered DNA-covered nanoparticles with high effi ciency 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 effi ciency 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 specifi c tissue locations, such as tumors.