Physico-chemical characterization-based safety evaluation of nanocalcium

- Nanocalcium is more bioavailable than microcalcium due to the large surface area.
- However, there is no efficient way to evaluate nanocalcium toxicity.
- Our approach contributes to the quantification of the maximum concentration of nanocalcium for further repeated toxicity test.

Nano- and microcalcium provided from the KFDA were compared in terms of physico-chemical properties. Calcium samples were tested using EF-TEM and X-ray diffractometry to check for size/morphology and crystal formation, respectively. Two samples of nano- and microcalcium were selected for further evaluation by FE-SEM, DLS (nano-size, 200-500 nm; agglomerate, >5 μm; micro-size, 1.5-30 μm), and electron spin resonance. Both samples were heterogeneous in size, existed as single crystal and aggregated form, and did not generate reactive oxygen species. The specific surface area of nano- and microcalcium measured by N2 Brunauere Emmette Teller method was 12.90 ± 0.27 m2/g and 1.12 ± 0.19 m2/g, respectively. Inductively coupled plasma optical emission spectrometry analysis revealed the release of 2-3 times more calcium ion from nano- compared to microcalcium at pH 5 and 7. Genotoxicity and acute single-dose and repeated-dose 14-day oral toxicity testing in SD rats performed to evaluate the safety of nanocalcium did not reveal toxicity. However, long-term monitoring will be required for an unequivocal conclusion. A nanocalcium dose of 1 g/kg is recommended as the maximum dose for repeated dose 13-week oral toxicity. Further studies could provide details of toxicity of nanocalcium on the repeated dose 13-week oral toxicity test.