Although much effort has been focused on the preparation of stable amorphous calcium phosphate(ACP)nanoparticles in aqueous solution,the redispersibility and long-term stability of ACP nanoparticles in aqueous solution remains an unresolved problem.In this work,stable colloidal ACPs were prepared by using an organic bisphosphonate(BP) as a sterically hindered agent in aqueous solution.The harvested calcium phosphate nanoparticles were characterized by inductively coupled plasma atomic emission spectrometry(ICP-AES),Fourier transform infrared(FTIR),X-ray diffraction(XRD),dynamic light scattering(DLS) and transmission electron microscopy(TEM).ICP-AES,FTIR and XRD results suggested the particles were ACP.DLS and TEM results indicated that the size of the ACP nanoparticles were in the range of 60 nm with a spherical morphology.The resulting calcium phosphate nanoparticles retained its amorphous nature in aqueous solution for at least 6 months at room temperature due to the stabilizing effect of the organic bisphosphonate.Moreover,the surface of the ACP nanoparticles adsorbed with the organic bisphosphate used showed good redispersibility and high colloid stability both in organic and aqueous solutions.
Rong-Hui LaiPing-Jiang DongYong-Li WangJian-Bin Luo
Traditional modifications to hydroxyapatite(HA) nanoparticles usually occurred after HA synthesis and thus are insufficient to avoid particle agglomeration.In this study,a new heterofunctional poly(ethylene glycol)(PEG) with phosphoric acid and carboxyl end groups,i.e.,α-(N-2-phosphoethyl phosphoric acid)-amide,ω-carboxyl-bismethyoxy poly(ethylene glycol)(ADP-PEG-COOH),was synthesized as an in situ surface modifier to HA nanoparticles.The resulting modified HA(ADP-PEG-HA) can disperse in methanol,forming a colloid stabilized by peripheral carboxyl-endcapped PEG chains.The colloidal particles resembled nanospheres which agglomerated to some extent under examination by transmission electron microscope.This highly dispersible HA nanoparticles in organic solvent might find application in preparing new HA nanocomposites.
We synthesised a series of v-aminoalkyl sodium hydrogen phosphates(AAP-n-Na, n=3, 4, 5, 6,purity > 99%), which have potential applications as bioactive cosmetic ingredients and surface modifiers of bone minerals(i.e. hydroxyapatites). Results from Fourier transformed infrared(FTIR), nuclear magnetic resonance(NMR) and high resolution mass spectroscopy, and elemental analysis all matched their chemical structures. The acid dissociation constants(pKa's) of each AAP-n(acid form of AAP-n-Na,n = 2–6) weremeasured by potentiometric titration, showing a general increasing trend with an increase in the chain length of AAP-n. However, the pKa_3 constant, which corresponds to the deprotonation of the ammonium group in AAP-n-Na, displayed an unusual decrease when n = even. This odd–even effect can be explained by the pairwise self-association of AAP-n-Na molecules in water where intermolecular hydrogen bonding in case of n = even is weaker than that in case of n = odd. All AAP-n-Na at concentrations up to 0.1%(w/v) were non-toxic to L929 fibroblasts and MG 63 osteoblast-like cells in terms of cell growth and morphology. These basic data were important for applications of AAP-n and their salts in biomedical engineering.
In this study, nanohydroxyapatite/polyurethane(nHA/PU) composites with various contents of methoxypoly(ethylene glycol) modified nHA(0 wt%, 10 wt%, 20 wt% and 30 wt%) were prepared by solution blending process. The physicochemical properties of the composite membranes were investigated by Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD), Transmission electronic microscopy(TEM), Differential scanning calorimetry(DSC), Thermo gravimetric analysis(TGA) and tensile tests. TEM photos of the nanocomposites showed that the nHA was uniformly dispersed in the polymer matrix. The membrane with 10 wt% nHA showed the highest tensile strength which was about 75% higher than that of the pure PU membrane. However, the tensile strength decreased when high content(above 20 wt%) fillers were added, which was still higher than that of pure PU. TGA measurements suggested that the thermal stability of the membranes was improved owing to nHA fillers. XRD and DSC results illustrated that the crystallinity of PU soft segments decreased with the increasing content of nanoparticles in the composites.
