Magnetic nanoparticles (MNPs) are of great interest for diverse biomedical applications such as hyperthermia, contrast agent for MRI, magnetic drug delivery, and cell mechanosensitive receptor manipulation to induce cell differentiation and proliferation. They are also potentially useful for cell labeling. However, a field that has not been fully explored is the use of MNPs for cellular based therapies. The therapeutic cells, loaded with MNPs, could be delivered by intravenous injection and be attracted to sites of injury through the application of an external magnetic field.

In this work we have studied the magnetite (Fe₃O₄) nanoparticle uptake capacities by a L929 fibroblast mouse cell line. Using a nanoparticle library encompassing both spherical and rod-shaped MNPs with diameters between 20 nm and 90 nm, respectively, we have investigated the influence of time and MNPs’ concentration on cell internalization and viability.

The MNPs were prepared via a facile way by co- precipitation reaction, then coated at the surface level with 3-aminopropyl trimethoxysilane by a silanization reaction, and finally labeled with fluorescent molecules (Rhodamine B isothiocyanate and Fluorescein -5(6)-isothiocyanate). The successful coating of the MNPs was assessed through ninhydrin assay, and DLS measurements. Cytotoxicity and viability tests were also performed. The internalization efficiency of the MNPs was assessed by measuring the internalized iron content through Inductively Coupled Plasma (ICP).

The findings from this study will have implications in the chemical design of nanostructures for cell based therapies.