Polymeric Soft Micro-Robots Propelled into a Microfluidic Device for Gut Target Delivery Studies

Soft microrobots have gained great attention in the bioengineering field due to their ability to navigate into biological fluids, overcoming biological barriers. Indeed, thanks to the size and controlled movement they can easily deliver drugs to a specific target.

In this work, we present completely natural and biodegradable propulsion soft micro-robots made of alginate, in the shape of microparticles (MPs). These MPs have been loaded with sodium bicarbonate and are meant to be delivered together with citric acid as a powder-based formulation embedded into a capsule that will open in the gut. Sodium carbonate released from MPs allows a propulsive action due to the citric acid spherical gradient established upon its release, making MPs go radially toward the gut mucosa. In principle, MPs can be loaded with anti-inflammatory drugs or probiotics allowing a slow release of the compound close to the cell layer. The action of such micro-robots was tested inside a microfluidic device that recreated citric acid gradient, with a channel for the introduction of MPs. Here we saw the propulsion activity of MPs towards lower citric acid concentration by taking time-lapse images. Caco-2 cells were cultured in the same microfluidic device allowing the formation of a mucus-like layer to assess the accumulation of the propulsive MPs.