Stabilisation of amorphous calcium phosphate in polyethylene glycol hydrogels

Abstract

Acellular polymer-calcium phosphate composites are promising bone graft materials.Hydrogels are suitable for providing a temporary matrix, while calcium phosphate minerals serve as ion depots for calcium and phosphate required for de novo bone formation. Crystalline calcium phosphates are stable under biological conditions and are commonly used in such scaffolds. However, the low solubility of these phases reduces the availability of free ions and potentially obstructs the remodelling necessary for the formation of mineralised tissue. Here, we investigate two different strategies to stabilise amorphous calcium phosphates in a synthetic polyethylene glycol-based hydrogel matrix.In vitro experiments mimicking an injectable application showed that amorphous calcium phosphate (ACP) of variable stability was formed in the hydrogel matrices. In additive-free composites, ACP transformed into brushite within minutes. Citrate or zinc additives were found to stabilise the formed ACP phase to different degrees. In the presence of citrate, ACP was stable for at least 2 h before it transformed into hydroxyapatite within 3-20 days. Partial calcium substitution with zinc (Zn/Ca = 10%) produced zinc-doped ACP of high stability that did not show signs of crystallisation for at least 20 days.The presented methods and findings open new possibilities for the design of novel injectable synthetic bone graft materials. The possibility to produce ACP with tailorable stability promises great potential for creating temporary scaffolds with good osteogenic properties.

Physical Properties and Biofunctionalities of Bioactive Root Canal Sealers In Vitro

“…When the root canal sealer was immersed in DW after setting, there was no marked change on the surface of the material compared with the as-prepared material. When immersed in HBSS, a composition of which is more similar to that of body fluid than DW, the surfaces of the bioactive root canal sealers showed a roughened aspect with an amorphous calcium phosphate-like structure, which was commonly displayed by the other bioactive surface ( Figure 1 A) [ 26 , 27 , 42 , 43 , 44 ]. Considering the Ca/P atomic ratios of WST and NBG after HBSS immersion were different to each other (WST: 1.63 and NBG: 1.03, according to the Figure 1 B), there are also some possibilities that the surfaces of these samples contain several types of calcium phosphate of which Ca/P ratio varying from 0.5 (Monocalcium phosphate monohydrate and monocalcium phosphate anhydrous) to 2.2 (Amorphous calcium phosphate: 1.2–2.2) [ 45 ], which will be further evaluated with high-resolution X-ray diffraction analysis or Fourier-transform infrared spectroscopy.…”

Attachment and spatial organisation of human mesenchymal stem cells on poly(ethylene glycol) hydrogels

“…were able to strike a balance between the two competing reactions of gelation and mineral formation resulting in hydrogels with reliable gelation kinetics and mechanical properties [139]. Additionally, the superior mechanical properties of PEG-M hydrogels could be particularly beneficial when incorporating biofunctional cues into the system.…”

Association between Serum Zinc and Calcification Propensity (T50) in Patients with Type 2 Diabetes Mellitus and In Vitro Effect of Exogenous Zinc on T50

“…However, the mechanisms underlying zinc inhibition of serum calcification propensity remain unclear. Even in polyethylene glycol hydrogels, not in serum, zinc was shown to inhibit the transformation of amorphous calcium phosphate (ACP) into hydroxyapatite [44]. In additive -free composite, ACP transformed into brushite within minutes.…”