Enhancing the stability of albumin foam-based support baths using pectin for embedded bioprinting

Embedded bioprinting enables the fabrication of complex, cell-laden structures by extruding bioinks into support baths. This technique has advanced the field of tissue engineering by expanding the range of printable bioinks and enabling the creation of intricate geometries; however, limitations such as instability and inadequate oxygen and nutrient delivery in current support materials restrict long print durations and compromise fidelity. Recently, albumin-based foams have been proposed as oxygen- and nutrient-permeable supports, but their rapid degradation restricts practical use. Here, we report the stabilization of albumin foams through the incorporation of pectin, a biocompatible polysaccharide. Three formulations-albumin-only (A8), albumin with 1% pectin (A8P1), and albumin with 2% pectin (A8P2)-were evaluated for foam stability, bubble morphology, rheology, and physicochemical properties. Pectin significantly delayed drainage and bubble coalescence while maintaining essential rheological features such as shear-thinning and recovery. These improvements enabled the embedded printing of chitosan, a low-viscosity and slow-crosslinking hydrogel, into multilayered and freeform structures with high fidelity. Cell viability assays confirmed that pectin did not compromise biocompatibility; A8P1 provided the most favorable microenvironment and outperformed conventional freeform reversible embedding of suspended hydrogels baths during extended incubation, owing to enhanced oxygen diffusion and a more physiological pH. Overall, pectin-stabilized albumin foams offer a simple, biocompatible, and self-removable support system that addresses key limitations of embedded bioprinting and broadens the range of printable bioinks.