Phosphorus-containing cyclodextrin polymers: metal cations and hydroxyapatite affinities

The aim of this study was to highlight the properties of novel phosphorus-containing β-cyclodextrin polymers (CDP) and mainly their dual complexing abilities toward hydrophobic guests and (bio)minerals. Affinity of CDP toward divalent metal cations, calcium, magnesium and zinc, has been investigated by isothermal titration microcalorimetry (ITC). The complexation constants K were around 1.1–6.2 × 10⁴ L mol^?1 and were in the order Ca²⁺ < Mg²⁺ < Zn²⁺. The K regular increase with the CDP molecular weights could be attributed to a cooperative binding of the cations by the monophosphate groups carried by the CDPs. Regarding their CD and phosphorus functionalities, the dual complexing abilities toward amphiphilic guests and divalent cations can occur independently as evidenced from ITC experiments performed in presence of both species. Finally, strong interactions between CDPs and hydroxyapatite have been highlighted by X-ray photoelectron spectrometry with adsorbed amount in the range of 2 mg/m². CDPs are thus promising materials endowed with dual functionalities which could serve in biomaterials to simultaneously entrap bioactive molecules and capture (bio)minerals.