Preparation of Calcium Phosphate/Polyurethane Composite Porous Scaffolds for Bone Repair by in situ Self-foaming Method

doi:10.15541/jim20150630

Abstract

Abstract:

One of the main technical problems in preparation of calcium phosphate/polyurethane (CaP/PU) composite scaffold for bone repair is to obtain a porous structure with uniformly distributed pores. The reason for this is due to the heterogeneous dispersion of the added foaming agents within the composite resulting in the increasing viscosity of polymer precursor during the composite fabrication process. To solve this problem, we report a novel method through incorporation of calcium hydrogen phosphate (DCPD) with polymer phase to achieve a composite system in early period of the synthesis process of CaP/PU composite. The uniformly distributed crystal water from DCPD can be released when temperature reaches above 75 ℃ and serve as foaming agents to react with isocyanate group in the PU and generate CO₂ gas. The generation of gas leads to a self-foaming process and consequently induces CaP/PU composite to form a porous scaffold. Scanning electron microscopy (SEM) observations show that CaP/PU composite scaffolds with uniform porous structure, high porosity and interconnectivity were obtained at 90 ℃. The mechanical strength can be doubled by re-curing treatment for the scaffold at 110 ℃ for 24 h. The resulting CaP/PU composite scaffolds with uniformly porous structure, high porosity and interconnectivity have shown potential applications in bone tissue engineering. Moreover, this simple and efficient method may provide new approaches for the preparation of polyurethane- based porous scaffolds.

Key words: calcium hydrogen phosphate, polyurethane, bone repair, scaffold, self-foaming

CLC Number:

TB33

LI Gen, LI Jiong-Jiong, LI Li-Mei, JIANG Jia-Xing, LI Yu-Bao, LI Ji-Dong. Preparation of Calcium Phosphate/Polyurethane Composite Porous Scaffolds for Bone Repair by in situ Self-foaming Method[J]. Journal of Inorganic Materials, 2016, 31(7): 719-725.

Figures/Tables 10

Table 1 Abbreviation and composition of fabricated composite scaffolds

Samples	nHA percentage /wt%	DCPD percentage /wt%	PU percentage /wt%
DCPD/PU	0	30	70
nHA-DCPD/PU-1	15	15	70
nHA-DCPD/PU-2	20	10	70

Fig. 1 Synthetic scheme of polyurethane

Fig. 2 SEM micrographs of DCPD/PU composite porous scaffolds formed at different temperature(a) 80℃; (b) 90℃; (c) 100℃; (d) 110℃

Fig. 3 SEM images (a-c) and pore size distribution (d-f) of CaP/PU porous scaffolds fabricated at 90 ℃ (a, d) DCPD/PU; (b, e) nHA-DCPD/PU-1; (c, f) nHA-DCPD/PU-2

Table 2 Porosity and mechanical properties of DCPD/PU, nHA-DCPD/PU-1 and nHA-DCPD/PU-2 composite scaffolds fabricated at 90 ℃

Composition	Porosity/%	Compressive strength/MPa	Compressive modulus/MPa
DCPD/PU	92.6±1.1	1.1±0.1	31.5±1.9
nHA-DCPD/PU-1	82.2±2.1	1.7±0.2	58.6±4.9
nHA-DCPD/PU-2	80.3±1.2	1.5±0.2	43.5±4.2

Fig. 4 XRD patterns of CaP/PU composite scaffolds fabricated at 90 ℃, nHA and DCPD powders

Table 3 Mechanical properties of DCPD/PU, nHA-DCPD/ PU-1 and nHA-DCPD/PU-2 composite scaffolds fabricated at 90 ℃ re-cured at 110 ℃ for 24 h

Composition	Compressive strength / MPa	Compressive modulus / MPa	Increase of compressive strength after re-curing / %
DCPD/PU	2±0.3	43.8±2.2	77
nHA-DCPD/PU-1	3.8±0.3	74.1±18.6	126
nHA-DCPD/PU-2	3.6±0.4	69.5±10.2	137

Fig. 5 FT-IR spectra of CaP/PU composite scaffolds cured at 90 ℃ (a-c) and re-cured at 110 ℃ (d-f) (a, d) DCPD/PU; (b, e) nHA-DCPD/PU-1; (c, f) nHA-DCPD/PU-2

Fig. 6 TG curve of CaP/PU composite scaffolds cured at 90 ℃ and re-cured at 110 ℃ for 24 h

Table 4 Results of thermal analysis of CaP/PU composite scaffolds

	Onset decompositon temperature for samples cured at 90 ℃/℃	Onset decomposition temperature for samples recured at 110 ℃ for 24 h/℃
DCPD/PU	309.0	316
nHA-DCPD/ PU-1	310.0	321
nHA-DCPD/ PU-2	309.6	316

References 20

[1]	REZWAN K, CHEN Q Z, BLAKER J J, et al.Biodegradable and bioactive porous polymer/inorganic composite scaffolds for bone tissue engineering.Biomaterials, 2006, 27: 3413-3431.
[2]	JANIK H, MARZEC M.A review: fabrication of porous polyurethane scaffolds.Materials Science and Engineering C, 2015, 48(1): 586-591.
[3]	TIENEN T G, HEIJKANTS R, BUMA P, et al.Tissue ingrowth polymers and degradation of two biodegradable porous with different porosities and pore sizes.Biomaterials, 2002, 23: 1731-1738.
[4]	KIRDPONPATTARA S, KHAMKERW A, SANCHAVANAKIT N, et al.Structural modification and characterization of bacterial cellulose-alginate composite scaffolds for tissue engineering.Carbohydrate Polymers, 2015, 132(5): 146-155.
[5]	YOU F, LI Y B, ZOU Q, et al.Fabrication and osteogenesis of a Porous nanohydroxyapatite/polyamide scaffold with an anisotropic architecture.ACS Biomaterials Science & Engineering, 2015, 1: 825-833.
[6]	TAMIMI F, KUMARASAMI B, DOILLON C, et al.Brushite- collagen composites for bone regeneration.Acta Biomater., 2008, 4: 1315-1321.
[7]	MYTHILI J, SUBRAMANIAN M V.Preparation and characterization of two new composites: collagen-brushite and collagen octa-calcium phosphate.Medical Science Monitor: International Medical Journal of Experimental and Clinical Research, 2002, 8(11): 481-487.
[8]	GUELCHER S A.Biodegradable polyurethanes: Synthesis and applications in regenerative medicine.Tissue Engineering Part B: Reviews, 2008, 14(1): 3-17.
[9]	MCBANE J E, SHAIFPOOR S, CAI K, et al.Biodegradation and in vivo biocompatibility of a degradable, polar/hydrophobic/ionic polyurethane for tisse engineering applications.Biomaterials, 2011, 32(26): 6034-6044.
[10]	GIANNITELLI S M, BASOLI F, MOZETIC P, et al.Graded porous polyurethane foam: a potential scaffold for oro-maxillary bone regeneration.Materials Science and Engineering C, 2015, 51: 329-335.
[11]	LIU H H, ZHANG L, ZUO Y, et al.Preparation and characterization of aliphatic polyurethane and hydroxyapatite composite scaffold.Journal of Applied Polymer Science, 2009, 112(5): 2968-2975.
[12]	YANG W, BOTH S K, ZUO Y, et al.Biological evaluation of porous aliphatic polyurethane/hydroxyapatite composite scaffolds for bone tissue engineering.Journal of Biomedical Materials Reserach Part A, 2015, 103(7): 2251-2259.
[13]	APELT D, THEISS F, ELWARRAK A O, et al.In vivo behavior of three different injectable hydraulic calcium phosphate cements.Biomaterials, 2004, 25: 1439-1451.
[14]	LI L M, ZUO Y, DU J J, et al.Structural and mechanical properties of composite scaffolds based on nano-hydroxyapatite and polyurethane of alcoholized castor oil.Journal of Inorganic Materials, 2013, 28(8): 811-817.
[15]	GABRIELA C, OCTAVIAN C. Mixed-matrix membranes based on polyurethane containingnanohydroxyapatite and its potential applications. Journal of Applied Polymer Science, 2015, (132)17: 41813.
[16]	WOODARD J R, HILLDORE A J, LAN S K, et al.The mechanical properties and osteoconductivity of hydroxyapatite bone scaffolds with multi-scale porosity.Biomaterials, 2007, 28: 45-54.
[17]	HULBERT S F, YOUNG F A, MATHEWS R S, et al.Potential of ceramic materials as permanently implantable skeletal prostheses.Journal of Biomedical Materials Research, 1970, 4(3): 433-456.
[18]	TERAMOTO N, SAITOH Y, TAKAHASHI A, et al.Biodegradable polyurethane elastomers prepared from isocyanate-terminated poly(ethylene adipate), castor oil, and glycero.Journal of Applied Polymer Science, 2010, 115(6): 3199-3204.
[19]	MISHRA A K, CHATTOPADHYAY D K, SREEDHAR B.FT-IR and XPS studies of polyurethane-urea-imide coatings.Progress in Organic Coatings, 2006, 55(3): 231-243.
[20]	MOTHE C G, ARAUJO C R.Properties of polyurethane elastomers and composites by thermal analysis.Thermochimicaacta, 2000, 357(1): 321-325.