Human stem cell response to layered zirconium phosphate

This study aims to evaluate the in vitro cytocompatibility of layered zirconium phosphate (ZP) and its derivative material that was organically modified using glycerophosphate (ZGP). The ZP and ZGP particles were prepared via a reflux method in an aqueous solution containing phosphoric acid. The field emission scanning electron microscopy showed the prepared samples were fine particles with 70-100 nm diameter. X-ray diffraction and Raman spectrometry indicated the presence of a layered crystal structure. The interlayer distance of ZP was estimated to be 0.76 nm from the 002 diffraction. Modification of ZP with β-glycerophosphate, lead to expansion of the interlayer distance of 0.85 nm. Grazing incidence X-ray diffraction and Raman spectrometry showed that the crystal structures of ZP and ZGP were maintained even after the samples were coated onto polyethylene (PE) substrates via hot pressing. The water droplet contact angles on the PE substrates coated with the ZP and ZGP particles (ZP/PE and ZGP/PE) were 2 ∼ 6° lesser than that on the uncoated PE substrate. After human adipose-derived stem cells (hASCs) were cultured on the substrates, 2.5-3.5 times higher numbers of adhered cells were observed on the substrates coated with ZP and ZGP than on the uncoated PE substrates and 1.1-1.6 times higher than on the substrate coated with hydroxyapatite particles (HAp/PE). Increasing cell numbers were observed after culturing for 24 h, indicating that the ZP/PE and ZGP/PE showed low cytotoxicity to the hASCs. Furthermore, the ZP/PE showed the highest area of hASC adhesion among all the samples. These results highlight the possibility that layered zirconium phosphate and its organically modified substances can be applied to biomaterials for tissue repair.