SPIO-Alginate Nanoparticles: New Platform for Calcium MR Imaging

Introduction Ca plays a vital role in many biological processes including cell differentiation and apoptosis, cardiac contractility, neurotransmission and brain function. 1 Because of the importance of Ca levels in maintaining proper function and in diseases, there is an increasing need for the development of new robust imaging platforms to perform in vivo detection of changes in Ca levels in wide range of concentrations. Currently, Ca imaging is mostly based on fluorescent methodologies. Recently, some progress has been achieved in the design of specific probes for indirect Ca MR imaging based on T1 or T2 relaxation. Combining the facts that alginates polysaccharides can be cross-linked, selectively, by Ca ions and that SPIO aggregation may change the contrast of T2* and T2 WI, we hypothesized that SPIO-alginate nanoparticles may be used as "smart" MRI probes for Ca detection (as shown schematically in Fig 1). In this study we describe the synthetic procedure of the preparation of stable water-soluble SPIO-alginate nanoparticles and the ability of these MRI probes to specifically detect different Ca concentrations in different media (water, serum and culture cell media) at physiological conditions (pH of 7.2 and 37.0C).