Functionalized Silica-Coated Metallic Replicas of Intracellular Protein Assemblies

Abstract

To replicate hierarchical biological architectures, biotemplating leverages diverse biological structures as templates for inorganic materials. Among the various inorganic materials explored in biotemplating, silica is an attractive material because of its stability and biocompatibility. However, existing biotemplating methods are largely nonselective, yielding silica replicas of bulk biological specimens. Here, we report an approach for selective materialization of targeted protein-associated architectures from cells and tissue slices, enabling recovery of the resulting silicified structures after enzymatic removal of surrounding non-target biomolecular components. To this end, we (i) immunolabeled target proteins with fluorophore-conjugated antibodies, (ii) embedded specimens in a hydrogel, (iii) removed endogenous proteins via enzymatic digestion, and (iv) converted the retained fluorophore patterns into Au nanoparticle assemblies through fluorophore-directed nanogold labeling and electroless Au growth, followed by silica coating. Using this strategy, we fabricated microtubule-derived silica bioreplicas from a human immune-lineage cell line and tuned their overall size by adjusting the expansion of the surrounding hydrogel matrix. Furthermore, functionalization of the silica surface with magnetic nanoparticles enables controlled motion of the bioreplicas under electromagnetic actuation. Finally, we extended the method to mouse brain slices and produced thermally stable silica bioreplicas of astrocytic and oligodendrocytic structures. Overall, this work expands the structural diversity and selectivity of silica-based biomimetic materials and broadens the palette of biotemplating templates.