Bacteriophages are essentially bionanoparticles with a protein coat, the composition of which can be controlled with atomic precision via genetic engineering, a property that makes them superior to synthetic nanoparticles as building blocks for bottom-up synthesis of multifunctional materials with advanced properties. We report hierarchically structured hydrogels of self-organized M13 bacteriophage bundles, composed of hundreds of M13 nanofilaments, which exhibit both long-range and micron-scale order, are visible in electron micrographs of the cross-linked state, and can adsorb up to 16× their weight in water.

We further demonstrate that these hierarchical hydrogels of M13 exhibit advanced properties at room temperature, namely, self-healing under biological conditions, autofluorescence in three channels, which decays through biodegradation, potentiating non-destructive imaging capability, and bioactivity in the cross-linked state toward the host bacteria. The latter is, in particular, a powerful property, allowing the development of hydrogels with tunable bioactivity when combined with the phage display and/or recombinant DNA technology. Filamentous phage M13 has garnered significant attention in the past decade for the development of functional materials, ranging from tissue engineering scaffolds to batteries.

Our investigation reveals the ability of these nanofilaments to self-organize into hierarchically structured soft matter, highlighting the power of self-organized M13 structures as building blocks for bottom-up synthesis.