Intracellular Formation of Synthetic Peptide Nanostructures Causes Mitochondrial Disruption and Cell Death in Tumor Spheroids

Supramolecular assemblies found in nature demonstrate the concept of creating functionality through structure formation. In recent years, these complex natural architectures have inspired the development of materials for the formation of synthetic nanostructures within living cells. These intracellular assemblies have the potential to modulate cellular processes, yet their specific effects on cellular metabolism and three-dimensional (3D) cell networks, such as tumor spheroids, still remain underexplored. Herein, we correlate the glutathione-induced formation of synthetic nanostructures inside MDA-MB-231 triple negative breast cancer cells to the metabolic disruption and mitochondrial degradation observed in two-dimensional (2D) cell culture, as well as to cell death and size decrease in a three-dimensional (3D) tumor spheroid model. In 2D cell culture, material-cell interactions were examined through live-cell imaging and by quantifying changes in mitochondrial respiration. By studying the interplay between glutathione-responsive cytosolic peptide assembly and the implications on the integrity of the mitochondrial network, as well as on 3D cell networks, our work advances the understanding of how synthetic intracellular nanofibers impact vital functions of living cells.