Bacteria as Nanoparticles Carrier for Enhancing Penetration in a Tumoral Matrix Model

One of the major concerns in the application of nanocarriers in oncology is their scarce penetration capacity in tumoral tissues, which drastically compromises the effctivity. Living organisms as cells and bacteria present the capacity to navigate autonomously following chemical gradients being able to penetrate deeply into dense tissues. In the recent years, the possibility to employ these organisms for the transportation of therapeutic agents and nanocarriers attached on their membrane or engulfed in their inner space have received huge attention. Herein, based on this principle, a new approach to deliver drug loaded nanoparticles achieving high penetration in tumoral matrices is presented. In this case, Escherichia coli (E. coli) bacteria wall is decorated with azide groups, whereas alkyne-strained groups are incorporated on the surface of mesoporous silica nanoparticles loaded with a potent cytotoxic compound, doxorubicin. Both functional groups form stable triazole bonds by click-type reaction allowing the covalent grafting of nanoparticles on living bacteria. Thus, the motility and penetration capacity of bacteria, which carried nanoparticles are evaluated in a 3D tumoral matrix model composed by a dense collagen extracellular matrix with HT1080 human fibrosarcome cells embedded. The results confirmed that bacteria are able to transport the nanoparticles crossing a thick collagen layer being able to destroy almost 80% of the tumoral cells located underneath. These findings envision a powerful strategy in nanomedicine applied for cancer treatment by allowing a homogeneous distribution of therapeutic agents in the malignancy.