Manganese dioxide-based nano/microreactors for long-term MRI imaging and Reactive Oxygen Species scavenging

In a healthy brain, manganese (Mn²⁺) ions can enter excitable cells and circulate within axons and across synapses. Because these ions can also be used as a contrast agent, Manganese Enhanced Magnetic Imaging (MEMRI) has been used, not only to study Amyotrophic Lateral Sclerosis (ALS), but also to guide intrathecal drug/cell delivery [1]. Mn²⁺ ions allow long-term T1-weigthed imaging, representing an advantage when compared to other ions. In ALS, motor neuron degeneration occurs and it has been correlated with oxidative stress, which can potentially be a therapeutic target [1]. Previous work [2] has demonstrated the ability of manganese dioxide (MnO₂) nanoparticles to scavenge Reactive Oxygen Species (ROS) by breaking down hydrogen peroxide in water, oxygen and Mn²⁺. As MnO₂ nanoparticles present toxicity when administered in high doses, it is our goal to develop MnO₂ nano/microreactors, where MnO₂ nanoparticles will be blended with a methacrylated gellan-gum (GG-MA) matrix. These nano/microreactors will potentially be used, not only to regulate apoptosis and inflammation in tissues, but also to be delivered and guided by MRI. GG-MA was selected due to its affinity to Mn²⁺, biocompatibility, biodegradability, easy functionalization and similarity to the extracellular matrix [3]. GG-MA was synthesized according to a previously described protocol [4] and further characterized via FTIR and ¹H-NMR. A comparison between synthetized and commercially bought MnO₂ nanoparticles will also be performed. Nano/microreactors will be evaluated regarding their rheology, stability, permeability and morphology. Their effect on cell viability and ability to scavenge ROS will also be evaluated.