| Calcium polyphosphate is a calcium phosphate-based inorganic polymer,which is considered to be an ideal material used for bone defect repair because of its similar chemical structure of natural bones,good biocompatibility,degradability and high mechanical strength.However,calcium polyphosphate implanted in the organism has poor biological activity and low degradation rate.In order to improve the bioactivity of calcium polyphosphate material and accelerate the degradation rate in vivo under the premise of guaranteeing its mechanical strength,people usually modify the surface of calcium polyphosphate material by coating it with special materials.Polydopamine attracts attention due to its advantages of being able to form a strong bond with almost all surfaces,inducing hydroxyapatite(HA)production,having no biological toxicity,and easy to prepare.Although there have been numerous reports on polydopamine surface-modifyed metals,polymers,ceramics and other materials,there are few studies on polydopamine-coated polyphosphates.In this experiment,poly-dopamine film was coated on calcium polyphosphate substrate by impregnation method to improve the bioactivity of calcium polyphosphate biomaterial.The main research content of this paper is to use the characteristics of dopamine oxidation self-polymerization in alkali solution and easy adhesion on the surface of various materials.Polydopamine is coated on the surface of calcium polyphosphate substrate by impregnation method and two different methods(high-temperature stirring method and the low-temperature static soaking method)are explored.The effects of two different methods on surface microstructure,mechanical properties and biological properties of PDA/CPP composites were studied,and the optimal preparation parameters were optimized.Subsequently,under the optimal preparation method,the effect of different dopamine concentration on the structure and biological properties of CPP was explored.In this experiment,X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),and scanning microscopy(SEM)were used to determine the phase composition and morphology of PDA/CPP biomaterials.Compressive strength and film adhesion test results were used to evaluate its mechanical properties,and in vitro degradation(soaking in Tris-HCl solution)and in vitro biological activity(biomimetic deposition of HA in simulated body fluids)to simulate the biological properties of PDA/CPP biomaterials in vivo.The results showed that PDA/CPP is an interconnected porous structure with a pore size of 1-300 μm.As the soaking time increases,the number of spherical or ellipsoidal PDA particles attached to the surface and inside of the CPP crystal increases and some degree of agglomeration occurs.The results of the compressive strength and the binding force of the film shows that the surface situation of samples prepared by stirring soaking at 60 ℃ is more uniform and the mechanical properties are better than that of samples prepared by static soaking at 37 0C.The compressive strength of PDA/CPP increases with the soaking time and then decreases.The maximum compressive strength is 4.20 MPa when stirred at 60℃ for 30 min in 1 g/L dopamine solution,which is 30.9%higher than that of pure CPP substrate.The sample prepared by stirring for 5 min at 60℃ in a 1 g/L dopamine solution has the largest film-binding force of 17.85N.The PDA content surface membrane binding force increased with the concentration of dopamine solution,and there was no more mutation in the friction curve,and the surface membrane binding state was better.PDA/CPP induces HA deposition in both Tris-HCl solution and SBF solution.After 28 days of degradation in Tris-HCl,corrosion cracks and cavities were formed,and the massive block-like CPP crystals were reduced and replaced by papillary,spherical,and irregularly shaped structures.After 28 days of soaking,the degree of degradation of Al-4 was 5.6 times that of CPP;after soaking in SBF solution for 7 days,the weight gain rate of A4-3 was 1.5 times that of CPP,indicating that PDA coating can promote the bone cell adhesion,growth and repair of bone tissue.Samples prepared at a 2 g/L dopamine concentration can have both suitable degradation properties and good biological activity. |
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