Self-healing capacity of fiber-reinforced calcium phosphate cements

Abstract

A major problem concerning the mechanical properties of calcium phosphate cements (CPC) is related to their inherent brittleness, which limits their applicability to non-load bearing bone defects. In this work the preparation of a damage tolerant CPC is presented, where the incorporation of functionalized carbon fibers facilitates steady state flat crack propagation with crack openings below 10 µm. A subsequent self-healing process in simulated body fluid, that mimics the in vivo mineralization of bioactive surfaces, closes the cracks and completely restores the mechanical properties. Hereby, two pathways of self-healing are presented: i) intrinsic healing that bases on the inherent bioactive properties of the cement matrix and chemically treated fibers, and ii) capsule based extrinsic healing, where H2PO4- is released as an initiator for the apatite formation. Such damage tolerant CPCs with self-healing capacity are of particular interest to increase the lifetime of implants as well as in the field of load-bearing bioceramics.

The Impact of Full-Scale Substitution of Ca2+ with Ni2+ Ions on Brushite’s Crystal Structure and Phase Composition

“…As can be seen at Point 1 in Figure 2A (pertaining to BNi0 with the Ca/P molar ratio 1.0), the precipitation of pure brushite results in plate-like crystals, as expected for the solution pH used in this work [17,18]. The dimensions of these plate-like crystals are ≈500 nm × 15 μm × 30 μm, which is comparable to those obtained by other authors [10,34]. Moreover, flat-plate morphology is a typical crystal structure for precipitated brushite [35].…”

“…Available evidence indicates that some of the chemically-bound water is released as brushite transforms to monetite (CaHPO 4 ) at ≈220 • C [44] and further to calcium pyrophosphate (Ca 2 P 2 O 7 ) as the temperature increases to ≈440 • C [8]. According to our results, when pure brushite (BNi0) is heated to 750 • C, approximately 21 wt % of its mass is lost [10], which is comparable to the theoretical mass loss of 20.93 wt % [45]. The BNi2−BNi6 samples with progressively greater Ni/Ca ratios lose more mass (27−35%), while a mass loss of 31.5 wt % is obtained for BNi10 containing solely hexaaquanickel(II) hydrogenphosphate monohydrate.…”

“…Presently, CaPs serve as precursors for biocements and bioceramics, to be used in medicine and dentistry, and to obtain other types of advanced materials [4,5]. Available evidence further indicates that CaPs can be adopted for drug delivery or bone tissue engineering [5,6], in fertilizers [7], and in the construction industry [8][9][10].…”

The Use of Calcium Phosphates in Cosmetics, State of the Art and Future Perspectives

“…Pure CaPs are characterized by being fragile, as they have both low impact resistance and low tensile stress (6 to 10 MPa), making them unsuitable for replacing bone (which has a tensile strength of 50 to 150 MPa in the case of cortical bone) [21]. For these reasons, they can be used in the form of powder or cements combined with several elements, such as Fe, Ag, Cu, Mg, Mn, Sr or Zn, or are reinforced with polymers to form bio-hybrid composites [27][28][29][30][31][32]. One of the most successful applications of CaPs is as coatings of metallic or polymeric implants that have poor osteoconductivity to improve their integration with the bone [33][34][35][36][37][38].…”

A conductive rubber with self‐healing ability enabled by metal‐ligand coordination

“…[1][2][3][4] Exogenous self-healing materials usually enclose crosslinking agent, which was released from the cracks to repair the materials. [5][6][7] The intrinsic selfhealing materials based on reversible chemical bonds including covalent and noncovalent bonds have attracted increasing attention. [8][9][10][11] Many researchers [12][13][14] have designed and synthesized elastomer with excellent self-healing effect.…”