Calcium ionic replacement in sodium trimetaphosphate particles: a novel strategy for bone tissue engineering

Sodium trimetaphosphate (NaTMP) has demonstrated potential in promoting biomineralization and bone tissue regeneration. However, little is known about the effects of substituting sodium ions with calcium, resulting in calcium trimetaphosphate (CaTMP), within bone engineering contexts. This study synthesized and characterized CaTMP, examining its osteogenic properties in comparison to NaTMP. Both compounds were evaluated in vitro for cytocompatibility and osteogenic potential using MG-63 osteoblast-like cells and bone marrow mesenchymal stem cells (BM-MSC). Assays for cell proliferation, metabolic activity, and alkaline phosphatase (ALP) activity were conducted, along with inductively coupled plasma analysis, gene expression analysis of osteogenic markers, and transmission electron microscopy (TEM) for particles uptake. The results revealed that both NaTMP and CaTMP were biocompatible, supporting cell proliferation and maintaining normal cell morphology. However, CaTMP at a concentration of 50 µg/mL significantly enhanced ALP activity in both MG-63 and BM-MSC cultures, suggesting a stronger osteogenic potential. TEM analysis confirmed the uptake of CaTMP by BM-MSCs, with no evidence of cytotoxicity. In osteogenic medium, BM-MSCs treated with CaTMP showed elevated expression levels of key osteogenic markers-BMP-2, ALP, SP7, Col1a1, SPP1, IBSP, BGLAP, and SPARC-compared to those treated with NaTMP. These findings suggest that CaTMP enhances osteoblastic differentiation more effectively than NaTMP, likely due to calcium's influence on bone formation pathways. The substitution of sodium with calcium in TMP presents a promising strategy for bone regeneration. Further research is needed to explore CaTMP's therapeutic potential for bone repair, offering a novel approach to bone tissue engineering.