Superparamagnetic iron oxide nanoparticles are used for an increasing range of biomedical applications, from imaging to mechanical actuation of cells and tissue. The aim of this study was to investigate the loading of smooth muscle cells with superparamagnetic iron oxide nanoparticles and to explore what effect this has on the phenotype of the cells. Adherent human smooth muscle cells were loaded with ∼17 pg of unconjugated, negatively charged, 50 nm superparamagnetic iron oxide nanoparticles (SPION). Clusters of the internalized SPION particles were held in discrete cytoplasmic vesicles. Internalized SPION did not cause any change in cell morphology, proliferation, metabolic activity, or staining pattern of actin and calponin, two of the muscle contractile proteins involved in force generation. However, internalized SPION inhibited the increased gene expression of actin and calponin normally observed when cells are incubated under differentiation conditions. The observed change in the control of gene expression of muscle contractile apparatus by SPION has not previously been described. This finding could offer novel approaches for regulating the phenotype of smooth muscle cells and warrants further investigation. This article is protected by copyright. All rights reserved
