Living Therapeutic Materials (LTMs) are composite materials that combine living components, such as bacteria, with non-living scaffolds for emergent functional characteristics[1]. Through their living components, LTMs exhibit functional properties such as responsiveness to environmental stimuli and the ability to synthesize complex biomolecules[2]. In this study, we aim to create LTMs for inflammatory bowel disease (IBD), a group of chronic inflammatory disorders of the colon and small intestine[3]. We aim to develop silica colloidosome-based LTMs containing genetically engineered bacteria that sense key inflammatory markers of IBD and release anti-inflammatory agents in response.

Amphiphilic silica nanoparticles are assembled into micrometer-sized colloidosomes via water-in-oil Pickering emulsions, followed by crosslinking with tetramethyl orthosilicate (TMOS) to form rigid shells. The resulting structures can encapsulate water-soluble compounds, including proteins or entire cells, within their inner aqueous core, which allows for integration of genetically engineered bacteria.

The Pickering emulsion parameters were optimized to control colloidosome size and yield. The silica shell exhibited high mechanical stability and a porous architecture. Scanning electron microscopy (SEM) images confirmed uniform morphology and structural integrity of the colloidosomes (see Figure 1). Selective permeability was demonstrated by the diffusion of model protein through the shell, confirmed by confocal microscopy. To enhance bacterial viability, an internal phase separation strategy based on a poly(ethylene-glycol)-diacrylate (PEGDA) hydrogel crosslinked using lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) under UV irradiation was introduced. The hydrogel significantly improved bacterial viability by forming a hollow internal lumen within the colloidosomes. Escherichia Coli Nissle 1917 genetically engineered to express the fluorescent protein mCherry were successfully encapsulated, confirming confinement, viability, and functional expression within the colloidosomes.

Silica colloidosome-based LTMs feature robust, and selectively permeable shells. A PEGDA hydrogel lumen maintains E. Coli Nissle 1917 viability and functionality. This system will enable programmable gut-targeted therapy, allowing live bacteria to sense inflammatory markers and release therapeutic molecules.