Valorization of Eggshell Waste into Bioaccessible and Non-toxic Calcium Carbonate Nanoparticles for Nutritional...

Nanoparticles have attracted significant interest due to their potential in various applications, including food fortification. However, their behavior during the digestive process has not yet been studied in depth. This study aimed to evaluate the bioaccessibility of high doses of CaCO3 using in vitro simulated gastrointestinal digestion and to investigate the behavior of this material in relation to in vitro cytotoxicity and in vivo acute toxicity in mice.

Calcium Carbonate Nanoparticles (Ca-NPs) were obtained from eggshells. Bioaccessibility and cytotoxicity were evaluated using concentrations of 6, 12, and 25 mg·mL-1 (≈60-250 mM Ca2+), compared with commercial CaCO3 (Ca-Ccial). An acute oral toxicity study was conducted in mice with 2000 mg/kg of Ca-NPs administered.

During the gastric phase, Ca-NPs exhibited 18% higher calcium bioaccessibility than CaCcial (p < 0.05). However, bioaccessibility decreased in the intestinal phase for both calcium sources due to pH-induced precipitation. Cytotoxicity assays showed that both calcium sources were non-toxic at concentrations up to 250 mM Ca2+ (p > 0.05). Acute toxicity tests in mice with 2000 mg/kg of CaCO3 confirmed the absence of adverse effects (p > 0.05).

Nanoscale surface and porosity of Ca-NPs provoked superior gastric dissolution and bioaccessibility compared to commercial CaCO3. The decline in intestinal solubility reflected pHinduced reprecipitation of Ca species. In vitro and in vivo assays confirmed biocompatibility without cytotoxicity. These findings elucidate the relationship between nanoparticle physicochemistry, solubility dynamics, and short-term biological safety.

These findings support the use of Ca-NPs as safe, bioaccessible, and potentially functional components for foods and pharmaceutical applications.