Bio-organic self-assembled DNA nanostructures and their use in the mitigation of the activation of microglia in neuroinflammation

Neuroinflammation, which is characterized by the activation of microglial cells, is a hallmark of ALS and most other neurodegenerative diseases. In the early phases of chronic neurodegenerative diseases, microglia assume an M2 phenotype, which is neuroprotective, while in advanced phases, they activate to an M1 phenotype which is neurotoxic. The mechanism by which activation spreads among microglial cells is not fully understood yet, but it is known that the exchange of proteins and microRNA is involved and exosomes are play a role in this process1. Studies have shown that activation of microglia stimulates the release of exosomes, altering their composition and function. As some miRNAs are upregulated in neuroinflammation, these could turn up to be transported in higher number and participate to the spreading of neuroinflammation to otherwise resting microglia. After demonstrating that microglia can naturally take up tetrahedron-shaped DNA nanostructures2 even without the need for any transfection agent, we designed and realized several types of modular DNA-based self-assembled nanostructures that can bear functional elements and labelling moieties (such as fluorophores). We engineered these self-assembled nanostructures by incorporating functional components that target and cleave specific miRNAs involved in the activation of microglia (like miR-34a). We observed the uptake of nanostructures by the cells and a reduction of the activation, by quantitating its molecular markers. Mir-34a, otherwise upregulated in activated microglia, was reduced after nanostructure treatment. The self-assembled tetrahedral DNA nanostructures proved a valuable shuttle for delivering specific functional elements to live mammalian cells without being intrinsically toxic. A variety of different organic or biological functional units can be loaded on them for future extensions of their application and the preparation of candidate drugs or theranostics by design. References: [1] F. Massenzio, , E. Peña-Altamira, S. Petralla, M. Virgili, G. Zuccheri, A. Miti, E. Polazzi, I. Mengoni , D. Piffaretti, B. Monti, Biochim Biophys Acta Mol Basis Dis. 2018, 1864, 3771-3785. [2] C. Bergamini, P. Angelini, K. J. Rhoden, A. M. Porcelli, R., G. Zuccheri, Methods, 2014, 67, 185-92