Robust macroporous starch hydrogel/eggshell biocomposites as sustainable scaffolds

Mechanically robust biomaterials offer significant promise for bone scaffolds; however, there remains a pressing need for alternatives that are well-characterized, cost-effective, and derived from sustainable sources. In this study, we developed a mechanically reinforced and sustainable macroporous hydrogel biocomposite by integrating starch, a low-cost natural polymer with favorable mechanical characteristics, with waste eggshell particles known for their ability to promote biomineralization. Starch-based matrices containing varying amounts of eggshell particles were fabricated via ice-templating and subsequently subjected to a post-crosslinking step using polyethylene glycol diglycidyl ether (PEGDE), a critical process that confers structural stability to the resulting hydrogel. Starch hydrogel eggshell biocomposites were characterized morphologically, chemically, mechanically, and biologically by SEM, swelling, FTIR, compression, biocompatibility, biomineralization, and biodegradation studies. While FTIR results confirmed successful post-crosslinking of the hydrogels, the mechanical tests revealed that inclusion of particles led to an almost threefold increase in Young's modulus compared to the control sample. SEM images displayed an open macroporous structure with pore sizes in the range of 48-261 µm. SEM-EDX analysis showed no mineral accumulation in the control sample, whereas eggshell-containing samples achieved a calcium content of up to 8.6 ± 0.2%. The MTT assay demonstrated improved cell viability in scaffolds with eggshell particles, and biodegradation tests revealed a reduced degradation rate in these scaffolds. Thus, the incorporation of eggshell particles, combined with post-crosslinking of the starch matrix, led to the formation of a mechanically strong, sustainable, cost-effective hydrogel scaffold with potential applicability in bone tissue engineering.