A Flexible and Degradable Hybrid Mineral as a Plastic Substitute

The development of environmentally friendly plastics is critical to ensure sustainable development. In contrast to polymer plastics derived from petrochemicals, inorganic minerals, which are the most abundant matter in Earth's crust, are environmentally friendly. However, the brittleness of these minerals limits their applications as plastics. Here, because of the advantages of both biomineralization and inorganic ionic polymerization, the calcium phosphate (CaP, a typical geological and biological mineral) oligomers are used for biomimetic mineralization under the regulation of polyvinyl alcohol and sodium alginate, resulting in flexible CaP nanofibers with periodic structural defects. The assembly of CaP nanofibers produces a hierarchically structured bulk hybrid mineral (HM), which overcomes the intrinsic brittleness of minerals and exhibits plasticity characteristics. HM exhibits better hardness and thermostability than classical polymer plastics due to its dominant mineral composition. Notably, HM is environmentally friendly and degradable in nature, as it can potentially participate in geological cycles, indicating that this material is an optimal plastic substitute. The construction of periodic structural defects within flexible minerals expands the current understanding of materials science.

The preparation of hydroxyapatite nanowires and nanorods via aliphatic micelles as soft templates

Hydroxyapatite nanoparticles were tunably synthesized via the use of an aliphatic–ethanol–water three-phase mixture system using micelles as soft templates via an emulsion–hydrothermal synergistic method.

Radiation-Induced Stable Radicals in Calcium Phosphates: Results of Multifrequency EPR, EDNMR, ESEEM, and ENDOR Studies

This article presents the results of a study of radiation-induced defects in various synthetic calcium phosphate (CP) powder materials (hydroxyapatite—HA and octacalcium phosphate—OCP) by electron paramagnetic resonance (EPR) spectroscopy at the X, Q, and W-bands (9, 34, 95 GHz for the microwave frequencies, respectively). Currently, CP materials are widely used in orthopedics and dentistry owing to their high biocompatibility and physico-chemical similarity with human hard tissue. It is shown that in addition to the classical EPR techniques, other experimental approaches such as ELDOR-detected NMR (EDNMR), electron spin echo envelope modulation (ESEEM), and electron-nuclear double resonance (ENDOR) can be used to analyze the electron–nuclear interactions of CP powders. We demonstrated that the value and angular dependence of the quadrupole interaction for 14N nuclei of a nitrate radical can be determined by the EDNMR method at room temperature. The ESEEM technique has allowed for a rapid analysis of the nuclear environment and estimation of the structural positions of radiation-induced centers in various crystal matrices. ENDOR spectra can provide information about the distribution of the nitrate radicals in the OCP structure.

Doping gadolinium versus lanthanum into hydroxyapatite particles for better biocompatibility in bone marrow stem cells

Lanthanide ions (Ln³⁺) doped hydroxyapatite (HAP) particles are well established in biomedical areas. Although Ln elements are closely located in the periodic table and have plenty of similar characteristics, the minor differences in the effective ionic radii could cause alterations in the physicochemical and biological properties of HAP substitutes. The present study synthesized lanthanum-(La-) and gadolinium-(Gd-) doped HAP particles (La-HAP and Gd-HAP). And the effects of two types of particles on bone marrow stem cells (BMSCs) viability were also measured and compared in vitro. The results indicated that the Gd-HAP adsorbed more serum proteins from culture media and inhibited the new layer of apatite formation on its surface when comparing to La-HAP with a similar crystalline structure, particle size, and Zeta potential. These surface modifications can significantly reduce the cell adhesion of Gd-HAP, simultaneously decreasing the Gd-HAP particle uptake efficiency. Moreover, the cell viability of Gd-HAP remained higher than that of La-HAP in culture periods. We concluded that a slight variation in the effective ionic radii between Gd³⁺ and La³⁺ could alter the adsorption of serum proteins on the particles' surface, modulating subsequent cellular responses. The present work provides an interesting view that Gd-HAP is endowed with better cellular biocompatibility than La-HAP.

Facile synthesis of ultralong hydroxyapatite nanowires using wormlike micelles as soft templates

Ultralong hydroxyapatite nanowires were synthesized by formation of an entangled long wormlike micelle structure in a three-phase reaction system.

One-Dimensional Hydroxyapatite Nanostructures with Tunable Length for Efficient Stem Cell Differentiation Regulation

It is well-accepted that most osteogenic differentiation processes do need growth factors assistance to improve efficiency. As a material cue, hydroxyapatite (HAp) can promote osteogenic differentiation of stem cells only in a way. Up to now, rare work related to the relationship between HAp nanostructures and stem cells in osteogenic differentiation process without the assistance of growth factors has been reported. In this study, one-dimensional (1D) HAp nanostructures with tunable length were synthesized by an oleic acid assisted solvothermal method by adjusting the alcohol/water ratio (η). The morphology of 1D HAp nanostructures can be changed from long nanowires into nanorods with the η value change. Different substrates constructed by 1D HAp nanostructures were prepared to investigate the effect of morphology of nanostructured HAp on stem cell fate without any growth factors or differentiation induce media. Human adipose-derived stem cells (hADSCs), a kind of promising stem cell for autologous stem cell tissue engineering, were used as the stem cell model. The experiments prove that HAp morphology can determine the performance of hADSCs cultured on different substrates. Substrate constructed by HAp nanorods (100 nm) is of little benefit to osteogenic differentiations. Substrate constructed on HAp long nanowires (50 μm) causes growth and spread inhibition of hADSCs, which even causes most cells death after 7 days of culture. However, substrate constructed by HAp short nanowires (5 μm) can destine the hADSCs differentiation to osteoblasts efficiently in normal medium (after 3 weeks) without any growth factors. It is surprise that hADSCs have changed to polyhedral morphology and exhibited the tendency to osteogenic differentiation after only 24 h culture. Hydroxyapatite nanostructures mediated stem cell osteogenic differentiation excluding growth factors provides a powerful cue to design biomaterials with special nanostructures, and helps to elucidate the interaction of stem cell and biomaterials nanostructures. The results from this study are promising for application in bone tissue engineering.

Acceleration of bone regeneration by activating Wnt/β-catenin signalling pathway via lithium released from lithium chloride/calcium phosphate cement in osteoporosis

By virtue of its excellent bioactivity and osteoconductivity, calcium phosphate cement (CPC) has been applied extensively in bone engineering. Doping a trace element into CPC can change physical characteristics and enhance osteogenesis. The trace element lithium has been demonstrated to stimulate the proliferation and differentiation of osteoblasts. We investigated the fracture-healing effect of osteoporotic defects with lithium-doped calcium phosphate cement (Li/CPC) and the underlying mechanism. Li/CPC bodies immersed in simulated body fluid converted gradually to hydroxyapatite. Li/CPC extracts stimulated the proliferation and differentiation of osteoblasts upon release of lithium ions (Li+) at 25.35 ± 0.12 to 50.74 ± 0.13 mg/l through activation of the Wnt/β-catenin pathway in vitro. We also examined the effect of locally administered Li+ on defects in rat tibia between CPC and Li/CPC in vivo. Micro-computed tomography and histological staining showed that Li/CPC had better osteogenesis by increasing bone mass and promoting repair in defects compared with CPC (P < 0.05). Li/CPC also showed better osteoconductivity and osseointegration. These findings suggest that local release of Li+ from Li/CPC may accelerate bone regeneration from injury through activation of the Wnt/β-catenin pathway in osteoporosis.

A postsynthetic ion exchange method for tunable doping of hydroxyapatite nanocrystals

Hydroxyapatite nanocrystals were doped with various metal ions with tunable doping level and preserved morphology via a postsynthetic approach.

Fabrication and characterization of polymer–ceramic nanocomposites containing pluronic F127 immobilized on hydroxyapatite nanoparticles

Synthesis and embedding of HA-F127 nanoparticles into a PCL/P123 nanofibrous scaffold plus molecular dynamics simulation of pristine and modified HA/polymer interactions.

Synthesis of iron oxide coated fluoridated HAp/Ln³⁺ (Ln = Eu or Tb) nanocomposites for biological applications

Fluorescent-magnetic iron oxide coated fluoridated HAp/Ln(3+) (Ln = Eu or Tb) nanocomposites were prepared. After transforming hydrophobic fluoridated HAp/Ln(3+) nanorods into hydrophilic ones, iron oxide particles were coated on their surface via thermal decomposition of Fe(acac)3. Fluorescent-magnetic nanocomposites developed in this study demonstrate excellent fluorescent-magnetic properties and prominent biocompatibility.

In situ synthesis and high adsorption performance of MoO2/Mo4O11 and MoO2/MoS2 composite nanorods by reduction of MoO3

MoO₂/Mo₄O₁₁ and MoO₂/MoS₂ composite nanorods with high adsorption performance were successfully synthesized by reducing MoO₃ nanorods.