Exploring the Antibacterial Properties of Lignin‐coated Magnetic Nanoparticles Synthesized in a One‐pot Process^†

Abstract

Given the current grave problems with antibiotic resistance, the discovery of novel, unconventional antibacterial drugs is not just important but also urgent. In this contribution, we report on the synthesis and testing of several composite nanomaterials that may find applications as therapeutic drugs or surface disinfectants. These materials are based on magnetic nanostructures coated with lignin, for example, lignin@FeCo. The magnetic properties of these nanocomposites facilitate removal or localization, whereas the lignin shell provides biocompatibility. These nanomaterials are mild antibacterials in the absence of light, but when illuminated become powerful antibacterial agents with typically ≥6 log units of bacterial reduction in 1-5 min of irradiation. These materials are strongly absorbing, including in the very useful NIR biological window, which we illustrate using 810 nm LED irradiation. We also show that in the short time required for antibacterial action, thermal changes are very small (≤5°C). Further, biocompatibility tests using fibroblasts show very limited cell damage and no enhanced adverse effect during 810 nm NIR illumination. As a surface coating for the active material, lignin provides a "trojan horse" strategy to facilitate the antibacterial action.

Lignin-Functionalized Fe3O4 Nanoparticles Facilitate the Extraction and Reduction of Metal Ions to Form Binary and Quinary Composite Nanoparticles

“…Functionalized magnetic NPs possess better applicability in comparison to nonmagnetic NPs due to the ease of purification as well as separation from the bulk phase simply by applying the external magnetic field. , This unique property facilitates the extraction of functionalized magnetic NPs in a highly purified state for diverse applications. Lignin functionalized magnetic NPs can be easily synthesized through hydrothermal synthesis at elevated temperature and pressure. − The hydrothermal synthesis allows the crystallization of tiny iron oxide NPs well coated with lignin, which prove to be excellent vehicles for the in situ synthesis of nanocomposites. Remarkably, the lignin coating does not impede the ferromagnetism of iron oxide NPs, thus allowing their simultaneous extraction from the solution under the effect of an external magnetic field.…”