Controllable fabrication of alginate-based floating beads with core-shell architecture

Hydrogel beads have been explored to be normal platform for nutrition encapsulation and delivery. However, hydrogel beads are naturally denser than water, which make hydrogel beads limite in some floating applications such as gastric floating systems. Here, we designed alginate-based floating beads featuring a core-shell structure, which were composed of a vegetable oil core encapsulated within an alginate network shell, utilizing coaxial co-extrusion microfluidic devices. The shell thickness and core size of the core-shell beads (with the size of 2.80–3.40 mm) can be controlled by simply adjusting the inner phase flow rate ( Q in ) and outer phase flow rate ( Q out ). Notably, the fabrication of floating core-shell beads was achievable with Q in ≥ 40  μ L/min and Q out set at 300  μ L/min. The Hen's egg test – chorioallantoic membrane (HET-CAM) test showed the floating core-shell beads were non-irritant, indicating their safety and biocompatibility properties. Given their floating properties and biocompatibility, these floating core-shell beads hold great potential for applications in the fields of gastric-retentive nutrition delivery. Following that, the floating core-shell beads were further encapsuled with pepsin. They displayed possessed satisfactory pepsin activity (90%) even after 15 days, suggesting that floating core-shell beads can protect the enzyme ingredients against damage. Interestingly, the floating core-shell beads exhibited both efficient sustained-release of pepsin and floating ability in simulated gastric solution. This work sheds light on the design and development of controllable floating core-shell hydrogel beads for various floating system applications.