Regulation of Stem Cell Signaling by Nanoparticle-Mediated Intracellular Protein Delivery

We demonstrate the intracellular delivery of proteins attached to hydrophobically modified silica nanoparticles for the manipulation of specifically targeted cell signaling proteins. We designed a chimeric protein, GFP-FRATtide to bind and block the active site of glycogen synthase kinase-3β (GSK-3β) - a protein kinase involved in Wnt signaling. Our results suggest the uptake of SiNP-protein conjugates by human embryonic kidney cells and rat neural progenitor stem cells, and delivery to the cell cytosol, presumably via endocytic mechanisms. Moreover, downstream effects in the Wnt signaling cascade, such as the elevation of β-catenin levels due to GSK-3β inhibition, were observed. As a result, accumulated β-catenin led to increased transcription of Wnt target genes such as c-MYC in the cell nucleus. The results presented here indicate that functional proteins can be delivered intracellularly in vitro using nanoparticles. This approach may enable the manipulation of cell function and possibly stem cell fate by influencing cellular signaling pathways.