Formation and properties of amorphous magnesium-calcium phosphate particles in a simulated intestinal fluid

The endogenous self-assembly of amorphous magnesium-calcium phosphate (AMCP) nanoparticles in human small intestine is an intriguing and newly-discovered process involved in immune-surveillance mechanisms. The study of nano and microparticles formation in complex media mimicking in vivo conditions contributes to unravel the features of endogenous AMCPs and, from a physico-chemical perspective, to shed light on the effect of biorelevant molecules on the precipitation of AMCPs.

Endogenous-like AMCPs have been synthesized in a commercial simulated intestinal fluid (SIF), which contains biorelevant molecules such as lecithin and taurocholate. The properties of these particles were compared to the features of AMCPs synthesized in water. The stability of the amorphous phase as a function of time, as well as AMCPs' morphology, have been investigated. In particular, the effect of the organic molecules present in the SIF was examined in terms of incorporation in the nano and micro particles and on their nanoscale structure.

Taurocholate and lecithin, present in the SIF, enhance stability of amorphous phase against particles crystallization, and lead to the formation of smaller AMCP aggregates with a rougher surface. They are also incorporated in the inorganic phase, and their self-assembled structure leads to the formation of core-shell nanoparticles.