Dehydrothermally crosslinked collagen/hydroxyapatite composite for enhanced in vivo bone repair

doi:10.1016/j.colsurfb.2018.01.011

Colloids and Surfaces B: Biointerfaces

Volume 163, 1 March 2018, Pages 394-401

https://doi.org/10.1016/j.colsurfb.2018.01.011 Get rights and content

Highlights

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A dehydrothermal method for a highly effective bone repair material is reported.
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The crosslinked porous collagen/hydroxyapatite composite is biocompatible.
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The properties of the composite can be facilely adjusted.
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Animal experiments indicate similar efficacy with autogenous bone repair materials.
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The procedure is economical and is applicable in commercialized production.

Abstract

Bone repair accounts for a large number of surgical operations. However, artificial bone replacement materials do not present the delicate continuing adjustment ability like natural bones and cause obvious side effects. Thus, materials that induce the regeneration of bones would be an optimal choice to repair bone tissues. This study proposes a biocompatible bone repair material prepared from crosslinked porous composite of collagen and hydroxyapatite. The proposed dehydrothermal method to cross-link the composite avoids use of extra chemical reagents for crosslinking and ensures that the materials were prepared using only bio-compatible materials. By adjusting the preparative parameters such as componential ratios or heating period, materials with a large property space could be achieved. Properties including porosity, mechanical strength, and swelling ratios could be facilely adjusted, promising its applications in personalized medical treatment. Cell experiments and animal experiments demonstrate the material presented high biocompatibility and effectively induced osteanagenesis in vivo. We expect the proposed material possesses high commercialization potential and serves as an effective bone repair material in realistic applications.

Graphical abstract

A dehydrothermal method is developed to fabricate collagen-hydroxyapatite composite bone repair materials which function effectively in vivo.

Introduction

Bone repair accounts for a large number of surgical operations to remedy defects caused possibly by trauma, tumor resection, or congenital deformities. When the defect exceeds a critical size (around 10 mm in rabbit or pig), natural chronical wound healing will not regenerate the tissue, and bone repair by clinical surgeries are necessary [[1], [2]]. However, the bone regeneration and absorption process is highly dynamic and delicate in vivo, and artificial structural materials prepared by metals which lack such continuing adjustment ability cause obvious side effects such as strain shielding and corrosion [2]. Because of these inconvenience, artificial scaffold material that fill the bone defect and provide a 3D environment for cells and tissues to grow on and finally induce the regeneration of the bone tissue would be ideal choices. The scaffolds need to be highly porous to allow for cell ingrowth and efficient mass transport of nutrients, oxygen, growth factors, and waste products. They also must be structurally sound to withstand the mechanical stresses during tissue neogenesis [3].

In choice of the artificial scaffold, biocompatibility, biodegradability, and the proper porous structure are the most important criteria. In the light of the fact that the components of natural bone are hydroxyapatite (Ca₁₀(PO₄)₆(OH)_2, HA) and collagen fibrils, the composite material of collagen/HA porouse material would be the ideal material for bone repair [4]. Such composite is not only biodegradable but would also avoid possible biotoxicity or irritation effect during the biodegradation process encountered by other polymer composite such as polyurethane (PU) or poly (L-lactic acid) (PLLA) [2].

In preparation of collagen/HA composite, a variety of methods have been proposed, including coprecipitation [5], porosity induced by sacrificial templating [6], electrospinning followed by deposition in simulated body fluid (SBF) [3], self-assembly followed by HA deposition, and freeze-casting [7], et al. [8]. In these materials, cross-linking of collagen is indispensable in maintaining the strong mechanical properties of collagen/HA composite in both natural bones and artificial bone repair materials [[9], [10]]. Uncross-linked collagen/HA composite would quickly deteriorate in cell culturing environment [1]. Cross-linked collagen has a greater modulus of elasticity (Young’s modulus), greater resistance to proteases and a lower degree of swelling than uncrosslinked collagen. Thus, material cross-linking would be important to adjust the mechanical properties of the composite as well as the degradation period [1]. However, from the practical point of view, a composite should be produced by using a minimum of solvents or chemical agents besides the building component of collagen and HA. In addition, with the emphasize of personalized medicine, a material should be facilely prepared and should present a large adjustable property space in order to meet the varied requirement towards material sizes, mechanical strengths, porosities, and degradation periods demanded by different people or different type of bones that need to be repaired.

Dehydrothermal (heating in vacuum) was proved to be efficient to cross-link single-component collagen material [[11], [12]]. In comparison with other cross-linking methods of collagen materials, including chemical cross-linking by glutaraldehyde (GA), hexamethylene diisocyanate (HMDC) [13], cyanamide, tanic acid [14], or 1-theyl-3-(3-dimethyl aminopropyl) carbondiimide (EDC) [[1], [15]], dehydrothermal does not introduce any additional chemical reagent. Thus it not only simplified preparation operation but also was considered as the most bio-compatible procedure. However in the preparation of collagen/HA composite, despite the intense exploration of the possible material preparation and cross-linking methods, to produce porous composite using dehydrothermal method has not been studied [15].

In this study, we propose a facile and biocompatible method to prepare porous and cross-linked collagen/HA composite by lyophilization followed by dehydrothermal process. By adjusting collagen/HA ratios and dehydrothermal period, materials with a wide variety of porosities, mechanical strengths, and stabilities, were obtained. These materials were biocompatible and supported osteoblast precursor cell growth. Animal experiments on New Zealand White Rabbits (NZWR) indicated that our artificial bone repair material presented similar bone repair effects with autogenous bone repair material, and both were remarkably effective compared with control groups where no repair materials were applied. Compared with other bone-repair composite materials, our material presents the unique merit of using only collagen, HA, and water as the main preparative components, and avoided massive using of any other chemical reagent that are not existent in natural bones. The simplicity of material preparative procedure should significant facilitates standard material production and possesses high potential in commercialized productions.

Section snippets

Experimental section

Materials. Collagen was obtained from Beijing Pashion Biotech Co., Ltd. Hydroxyapatite, phalloidine and Hochest Stain solution were purchased from Sigma-Aldrich Co. (USA). For cell culture, the mouse MC3T3-E1 preosteoblast cell line was obtained from the Chinese Academy of Medical Sciences. Fetal bovine serum (FBS) was obtained from Sangon Biotech Co. (Shanghai). Dulbecco’s modified eagle medium (DMEM), calcium- and magnesium-free phosphate buffered saline (PBS) and trypsin were obtained from

Characterization of bone repair composite

Previous studies revealed that the fraction of HA remarkably influences cell behaviors of various collagen/HA composite [[16], [17]]. Thus a series of composite with varying HA fraction ratios were prepared. The synthesized collagen-HA composite was denoted according to the ratios between collagen and HA during the preparative steps as C19, C37, and C55, for the collagen: HA ratios 1:9, 3:7, and 5:5. The choice of the ratios between collagen and HA were results of two considerations: (1) the

Conclusions

In summary, we propose a dehydrothermal method to prepare crosslinked composite bone repair material consists of collagen and hydroxyapatite. The material properties, including porosities, mechanical strengths, and molecular loadings and releases, could be facilely adjusted within wide property spaces. Compared with other methods to prepare crosslinked composite collagen/HA materials, our method used only biocompatible reagents. The dehydrothermal crosslinking method did not require additional

Acknowlegements

This work was supported by the Fundamental Research Funds for the Central Universities (2652017360, 2652013115), Special Promotion Project for Beijing Small and Medium-sized Scientific and Technological Enterprise (Z16010101427), and the NSFC (21673209).

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¹: These authors contributed equally.

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Dehydrothermally crosslinked collagen/hydroxyapatite composite for enhanced in vivo bone repair

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Experimental section

Characterization of bone repair composite

Conclusions

Acknowlegements

Biomaterials

Biomaterials

J. Biol. Chem.

Int. J. Biol. Macromol.

Mater. Sci. Eng. C Mater. Biol. Appl.

Colloids Surf. B Biointerfaces

Biophys. J.

Collagen-hydroxyapatite composites for hard tissue repair

Eur. Cells Mater.

Biomimetic mineralization of woven bone-like nanocomposites: role of collagen cross-links

Biomacromolecules