title: Biologically Analogous Calcium Phosphate Tubes from a Chemical Garden.
abstract: Calcium phosphate (CaPO4) tubes with features comparable to mineralized biological microstructures, such as Haversian canals, were grown from a calcium gel/phosphate solution chemical garden system. A significant difference in gel mass in response to high and low solute phosphate equivalent environments existed within 30 min of solution layering upon gel (p = 0.0067), suggesting that the nature of advective movement between gel and solution is dependent on the solution concentration. The transport of calcium cations (Ca2+) and phosphate anions (PO43-) was quantified and changes in pH were monitored to explain the preferential formation of tubes within a PO43-concentration range of 0.5-1.25 M. Ingress from the anionic solution phase into the gel followed by the liberation of Ca2+ions from the gel was found to be essential for acquiring self-assembled tubular CaPO4structures. Tube analysis by scanning electron microscopy (SEM), X-ray diffraction (XRD), and micro X-ray florescence (μ-XRF) revealed hydroxyapatite (HA, Ca10(PO4)6(OH)2) and dicalcium phosphate dihydrate (DCPD, CaHPO4·2H2O) phases organized in a hierarchical manner. Notably, the tubule diameters ranged from 100 to 150 μm, an ideal size for the permeation of vasculature in biological hard tissue.
authors.affiliation: School of Chemical Engineering, University of Birmingham , Edgbaston B15 2TT, U.K.
authors.forename: Erik A B
authors.identifier: 0000-0003-2850-721X
authors.initials: EA
authors.lastname: Hughes
authors.affiliation: School of Chemical Engineering, University of Birmingham , Edgbaston B15 2TT, U.K.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Williams
authors.affiliation: School of Chemical Engineering, University of Birmingham , Edgbaston B15 2TT, U.K.
authors.forename: Sophie C
authors.initials: SC
authors.lastname: Cox
authors.affiliation: School of Chemical Engineering, University of Birmingham , Edgbaston B15 2TT, U.K.
authors.forename: Liam M
authors.initials: LM
authors.lastname: Grover