Biosynthesis of magnetic nanoparticles by human mesenchymal stem cells following transfection with the magnetotactic bacterial gene mms6

Abstract

The use of stem cells to support tissue repair is facilitated by loading of the therapeutic cells with magnetic nanoparticles (MNPs) enabling magnetic tracking and targeting. Current methods for magnetizing cells use artificial MNPs and have disadvantages of variable uptake, cellular cytotoxicity and loss of nanoparticles on cell division. Here we demonstrate a transgenic approach to magnetize human mesenchymal stem cells (MSCs). MSCs are genetically modified by transfection with the mms6 gene derived from Magnetospirillum magneticum AMB-1, a magnetotactic bacterium that synthesises single-magnetic domain crystals which are incorporated into magnetosomes. Following transfection of MSCs with the mms6 gene there is bio-assimilated synthesis of intracytoplasmic magnetic nanoparticles which can be imaged by MR and which have no deleterious effects on cell proliferation, migration or differentiation. The assimilation of magnetic nanoparticle synthesis into mammalian cells creates a real and compelling, cytocompatible, alternative to exogenous administration of MNPs.

The Potential of Intrinsically Magnetic Mesenchymal Stem Cells for Tissue Engineering

“…To further characterize the magnetic nature of the intracytoplasmic particles, we have used SQUID magnetometry which measures the total magnetic moment of a sample, including all atomic and molecular magnetic contributions. Results of these measurements for MSCs 21 days after transfection confirmed the magnetic nature of the cellular nanoparticles of the nanoparticles synthesized by the mms6 - and mmsF -transfected cells [ 48 ]. The mms6 -transfected MSCs appear to show greater magnetism than mmsF -transfected MSCs with mms6/mmsF co-transfected MSCs showing least magnetism (unpublished results).…”

“…Recent studies by our group have shown the potential of using a transgenic approach to magnetize MSCs by transfection with either or both the mms6 and mmsF genes [ 48 ] derived from Magnetospirillum magneticum AMB-1, a magnetotactic bacterium that synthesizes single-magnetic domain crystals which are incorporated into magnetosomes. These studies involved transfecting human MSCs with modified mms6 or mmsF genes, after which gene expression studies, assessment of nanoparticle production and effects on MSC function were established ( Figure 2 ).…”

“…In vitro phantom studies on mms6 -transfected cells following 21 days in culture in the presence of ferric quinate indicated that cells were identifiable by MRI, confirming previous studies that mms6 could act as a MR reporter gene. Atomic force microscopy/magnetic force microscopy (AFM/MFM) indicated that the synthesized nanoparticles within mms6 -transfected cells were magnetic ( Figure 5 ) in contrast to MSCs incubated with FeCl 3 and untransfected MSCs in which no magnetic structures were identified [ 48 ]. To further characterize the magnetic nature of the intracytoplasmic particles, we have used SQUID magnetometry which measures the total magnetic moment of a sample, including all atomic and molecular magnetic contributions.…”

User-friendly Interface for Electrical Cell-substrate Impedance Spectroscopy System

“…(11,12) Using the impedance sensor, we can observe the cytotoxicity of a variety of toxicants and the status of stem and cancer cells. (13)(14)(15)(16)(17)(18)(19) When cells are added to the electrical cell-substrate impedance sensor array and attached to the electrodes, they act as insulators that increase the impedance. As the cells grow and cover the electrodes, the number, shape, and attachment properties of these cells affect the current flow and change the impedance.…”

“…This can be accomplished using a dedicated ECIS system or a data processing and visualization application. (8,9,17,24,25) For portable devices, a personal computer (PC) may be connected to the impedance measuring device. (21) The control of the graphical user interface (GUI) requires input devices such as a mouse and keyboard as well as a display device such as an LCD monitor.…”