Dual Expression of Magnetosome-Associated Genes mms6 and magA to Enhance Magnetic Resonance Imaging Contrast in Mammalian Cells

Reporter genes are employed to improve visualization of specific tissues by creating a higher contrast in MR imaging. The genes on the magnetosome gene island (MAI) in magnetotactic bacteria have been of interest as contrast agents due to their ability to facilitate the formation of magnetic nanoparticles. In this work, we evaluated the influence of co-expressing mms6 and magA- genes within MAI- in mammalian cells and their effect on transverse relaxation rate when cultured with and without iron supplementation. A transgenic colorectal adenocarcinoma (HT-29) cell line co-expressing mms6 and magA was produced by transgene delivery using Sleeping Beauty. The iron uptake was measured using an iron assay kit and viability of cells was determined by trypan blue and MTT assays. The cells were supplemented with ferric citrate and imaged using a 3T Siemens Prisma. Data from a multiecho sequence was used to calculate R₂ (R₂ = 1/T₂) values by monoexponential fitting. We evaluated the R₂ of the cells co-expressing the two genes with cell lines expressing either gene individually and non-expressing control cells. The result showed dual expression of mms6 and magA lead to a significant increase in R₂ and iron uptake compared to cells expressing either gene individually.