Abstract
(1) Background: The preparation and characterization of novel fully injectable enzymatically hardened tetracalcium phosphate/monetite cements (CXI cements) using phytic acid/phytase (PHYT/F3P) hardening liquid with a small addition of polyacrylic acid/carboxymethyl cellulose anionic polyelectrolyte (PAA/CMC) and enhanced bioactivity. (2) Methods: Composite cements were prepared by mixing of calcium phosphate powder mixture with hardening liquid containing anionic polyelectrolyte. Phase and microstructural analysis, compressive strength, release of ions and in vitro testing were used for the evaluation of cement properties. (3) Results: The simple possibility to control the setting time of self-setting CXI cements was shown (7–28 min) by the change in P/L ratio or PHYT/F3P reaction time. The wet compressive strength of cements (up to 15 MPa) was close to cancellous bone. The increase in PAA content to 1 wt% caused refinement and change in the morphology of hydroxyapatite particles. Cement pastes had a high resistance to wash-out in a short time after cement mixing. The noncytotoxic character of CX cement extracts was verified. Moreover, PHYT supported the formation of Ca deposits, and the additional synergistic effect of PAA and CMC on enhanced ALP activity was found, along with the strong up-regulation of osteogenic gene expressions for osteopontin, osteocalcin and IGF1 growth factor evaluated by the RT-qPCR analysis in osteogenic αMEM 50% CXI extracts. (4) Conclusions: The fully injectable composite calcium phosphate bicements with anionic polyelectrolyte addition showed good mechanical and physico-chemical properties and enhanced osteogenic bioactivity which is a promising assumption for their application in bone defect regeneration.
Highlights
Calcium phosphate biocements (CPC) represent biomaterials which are continuously improved in terms of their positive biological properties like biocompatibility, osteoinductivity, osteoconductivity as well as other physico-chemical or mechanical properties
phytic acid (PHYT) supported the formation of Ca deposits, and the additional synergistic effect of PAA and CMC on enhanced ALP activity was found, along with the strong up-regulation of osteogenic gene expressions for osteopontin, osteocalcin and IGF1 growth factor evaluated by the RT-qPCR analysis in osteogenic αMEM 50% CXI extracts
The final products of CPC hardening are the specific forms of nanocrystalline or amorphous calcium deficient hydroxyapatite (HAP), which support the activity of specific bone cells and promote the cell proliferation and growth due to a rise in the concentration of calcium and phosphate ions around the implanted biocement, and the presence of a large proportion of micropores in the microstructure with corresponding large specific surface area
Summary
Calcium phosphate biocements (CPC) represent biomaterials which are continuously improved in terms of their positive biological properties like biocompatibility, osteoinductivity, osteoconductivity as well as other physico-chemical or mechanical properties. These systems were composed of calcium phosphates and a liquid phase ensuring sufficient viscosity, which, in addition, can react with the cement mixture or serve to polymerize with the aim to strengthen the overall composite system Another possible solution is represented by the formation of composite hydrogel systems in combination with solid powdered cement mixtures of calcium phosphates, which affects their mechanical, physico-chemical and biological properties [6,7,8,9] Hydrogels in the systems mimic both the extracellular matrix and biomimetic structure of hard tissues, which support the adsorption of specific growth factors, adherins as well as the interaction of the cells themselves [10]. The calcium phosphate composite cements with polyacrylic acid (PAA) demonstrated adjustable brittle/ductile strength at high PAA contents (up to 50 wt%) after setting [21]
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