Alternating magnetic field and NIR energy conversion on magneto-plasmonic Fe3O4@APTES-Ag heterostructures with SERS detection capability and antimicrobial activity.

Multipurpose Fe3O4@APTES-Ag heterostructures for mutual heat generation, SERS probing, and antimicrobial activity were fabricated using a three-step process. Silver metallic particles were precipitated on a thin silica shell that served as an interlayer with Fe3O4 nanocubes. The structural properties were studied by means of the powder X-ray diffraction technique, and selected area electron diffraction. Particle size, distribution, and morphology were evaluated using transmission electron microscopy, while element mapping was performed using the STEM-EDS technique. The presence of the silica shell and the effectiveness of the Ag reduction were checked by FTIR-ATR spectroscopy. The heat generation ability was studied by using AMF and NIR contactless external stimulations working separately and simultaneously. We demonstrated that the dual mode stimulation leads to a SAR (specific absorption rate) of 1000 W g-1 with the predominant role of the mechanism associated with the light interaction. The SERS effect was recorded with the use of the R6G standard molecule showing high capability of the heterostructures for Raman signal augmentation. Fe3O4 nanocubes decorated with Ag particles have shown antibacterial activity against P. aeruginosa. The Fe3O4@APTES-Ag presents promising potential as a multipurpose platform for biological applications ranging from photomagnetic therapies, to analytical probes exploiting the SERS effect and antibacterial activity.

Energy Conversion and Biocompatibility of Surface Functionalized Magnetite Nanoparticles with Phosphonic Moieties.

Magnetite nanoparticles (MNPs) were synthesized using two distinctly different approaches, co-precipitation (CP) and thermal decomposition (TD), and further surface functionalized with organophosphonic ligands containing different numbers of phosphonic groups. We have shown that it is possible to fabricate flower-like assemblies of MNPs through TD at lower temperatures, whereas CP MNPs formed agglomerates of particles with broad size distribution and irregular shapes. The effect of the organophosphonic ligands on the heating efficiency of the TD and CP MNPs under dual mode stimulation (simultaneous action of AMF and NIR laser radiation) was studied for the first time. It was found that in the case of the cost-effective CP MNP synthesis surface functionalization with chosen phosphonic ligands leads to higher heating efficiency upon laser stimulation, whereas better performance of TD MNPs was found under the action of AMF due to the significant difference of nanoparticle properties. The biocompatibility of surface functionalized MNPs with organophosphonic ligands was evaluated through thorough studies of the metabolic activity of MNPs in normal human foreskin fibroblasts as well as oxidative stress induction and oxidation stress response which has not been previously reported for most of the organophosphonic moieties used in this study.