Bacteria capture with magnetic nanoparticles modified with cationic carbosilane dendritic systems.

Bacteria elimination from water sources is key to obtain drinkable water. Hence, the design of systems with ability to interact with bacteria and remove them from water is an attractive proposal. A diversity of polycationic macromolecules has shown bactericide properties, due to interactions with bacteria membranes. In this work, we have grafted cationic carbosilane (CBS) dendrons and dendrimers on the surface of iron oxide magnetic nanoparticles (MNP), leading to NP (ca. 10 nm) that interact with bacteria by covering bacteria membrane. Application of an external magnetic field removes MNP from solution sweeping bacteria attached to them. The interaction of the MNP with Gram-positive S. aureus bacteria is more sensible to the size of dendritic system covering the MNP, whereas interaction with Gram-negative E. coli bacteria is more sensible to the density of cationic groups. Over 500 ppm of NPM, MNP covered with dendrons captured over 90% of both type of bacteria, whereas MNP covered with dendrimers were only able to capture S. aureus bacteria (over 90%) but not E. coli bacteria. Modified MNP were characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), Z potential and dynamic light scattering (DLS). Interaction with bacteria was analyzed by UV, TEM and scanning electron microscopy (SEM). Moreover, the possibility to recycle cationic dendronized MNP was explored.