Magnesium alginate as a low-viscosity (intramolecularly cross-linked) system for the sustained and neuroprotective release of magnesium

The administration of Mg ions is advantageous in pathological scenarios such as pre-enclampsia and forms of neuroinflammation (e.g. stroke or injury); yet, few systems exist for their sustained delivery. Here, we present the (static light scattering and diffusing-wave spectroscopy) characterization of magnesium alginate (MgAlg) as a potentially injectable vehicle ifor the delivery of Mg. Differently from other divalent cations, Mg does not readily induce gelation: it acts within MgAlg coils, making them more rigid and less prone to entangle. As a result, below a threshold concentration (notionally below 0.5 % wt.) MgAlg are inherently less viscous than those of sodium alginate (NaAlg), which is a major advantage for injectables; at higher concentrations, however, (stable, Mg-based) aggregation starts occurring. Importantly, Mg can then be released e.g. in artificial cerebrospinal fluid, via a slow (hours) process of ion exchange. Finally, we here show that MgAlg protects rat neural stem cells from the consequence of an oxidative insult (100 μM H2O2), an effect that we can only ascribe to the sustained liberation of Mg ions, since it was not shown by NaAlg, MgSO4 or the NaAlg/MgSO4 combination. Our results therefore indicate that MgAlg is a promising vehicle for Mg delivery under pathological (inflammatory) conditions.