Immersion behavior of gelatin-containing calcium phosphate cement

doi:10.1016/j.actbio.2007.10.011

Acta Biomaterialia

Volume 4, Issue 3, May 2008, Pages 646-655

https://doi.org/10.1016/j.actbio.2007.10.011 Get rights and content

Abstract

Calcium phosphate cements (CPCs) have many favorable properties that support their clinical use as bone defect repair. However, it is difficult to deliver to the required site and hard to compact adequately due to inherently low ductility of ceramics. The aim of this study focused on the effect of the gelatin content on properties of CPCs. The diametral tensile strength, morphology, and weight loss of gelatin cements were evaluated after immersion in physiological solution, in addition to setting time. The results indicated that the setting time significantly increased with increasing gelatin amount. The 2 wt.% gelatin could make CPCs attain the maximum strength value of 2.1 MPa at 15-day immersion, while 1.6 MPa for the cement without gelatin. It is concluded that the presence of gelatin improved mechanical properties of CPCs; in particular, 2 wt.% gelatin. CPCs containing 2 wt.% gelatin hardened in an acceptable time recommended for clinical applications.

Introduction

Over the past 40 years, the essential material of bone cement in clinical applications is polymethylmethacrylate (PMMA) [1]. However, this material could release methylmethacrylate monomer to result in necrosis of cells around the repair site [2]. In addition, PMMA cannot directly bond to bone tissue through a chemical bonding [3]. Therefore, a variety of bone cements have been made to aim at displacing PMMA. A self-setting cement composed of only calcium phosphate compounds that are similar with the mineral component of bone tissue was developed in the early 1980s [4] and has gained much popularity. Calcium phosphate cements (CPCs) are good bioactive materials for bone defect repair in orthopedic and dental surgery because of its excellent bioactivity and mechanical properties [5], [6], [7], [8], [9]. Self-setting CPCs can be handled by the surgeon in paste form and injected into bone cavities or defects. They then set to form a mineral matrix at the contact of which healing bone tissue can form. Although CPC has many favorable properties that support its clinical use, it has proved problematic. For example, it is difficult to deliver to the required site and hard to compact adequately due to relatively poor brittleness resistance. Efforts have been made in recent years to overcome the disadvantages. The polymeric materials such as chitosan [7], [10], alginate [11], and gelatin [5], [6] have the potential to improve the handling properties of CPCs. For example, Yokoyama et al. developed a chitosan-containing CPC that could be moulded into any desired shape due to its chewing-gum-like consistency [7]. In a study by Tajima et al., the addition of sodium alginate could enhance anti-washout property of Biopex^® cement [11]. However, addition of sodium alginate into the liquid phase of Biopex^® resulted in a slower transformation to apatitic phase. As a result, diametral tensile strength of set cement specimens decreased when it was hardened in an incubator kept at 37 °C and 100% relative humidity for 7 days.

Gelatin is a natural polymer, which is obtained from the bovine bone by thermal denaturation or physical and chemical degradation of collagen, and had been widely employed as a scaffold material in the tissue engineering. The research combining natural gelatin with bioactive CPC [5], [6], attempting to achieve elastic bone cement, attracts much attention and is little studied. Fujishiro et al. found that addition of gelatin gel to α-tricalcium phosphate cement resulted in the formation of a porous solid with pores of 20–100 μm in diameter whose pore diameter increased with increasing gelatin gel content [5]. The compressive strength after one week soaking in tris(hydroxymethyl)-aminomethane buffer solution (pH 7.4) increased from 9.0 to 14.1 MPa with increasing gelatin content up to 5 wt.% and thereafter decreased.

The aim of this study is to examine the effect of gelatin amount on immersion behavior of calcium phosphate cements. The calcium carbonate (CaCO₃) and monocalcium phosphate monohydrate (Ca(H₂PO₄)₂· H₂O) in a 2:1 molar ratio is selected for the intention to formulate stoichiometric composition of tricalcium phosphate. The major techniques used for characterizing the cement specimens included scanning electron microscopy (SEM) and diametral tensile strength (DTS). Effect of immersion time in the physiological solution on the properties of the various gelatin cements was studied, in addition to setting time.

Section snippets

Preparation of the gelatin cement

Type B gelatin (isoelectric point of 4.7–5.2) from bovine skin (Sigma, St. Louis, MO) was weighed and dissolved in deionized distilled water at 60 °C until a homogeneous 10 wt.% gelatin solution was attained. First, CaCO₃ (Showa, Tokyo, Japan) was added to gelatin solution and dried at 60 °C in an oven. After that, Ca(H₂PO₄)₂· H₂O (Showa, Tokyo, Japan) was added to the mixture using a conditioning mixer (ARE-250, Thinky, Tokyo, Japan). Herein, gelatin-containing calcium phosphates were obtained by

Setting time

The control cement formed from the mixture of MCPM and CaCO₃ set within 8 min when mixed with 1 M Na₂HPO₄. On the contrary, all gelatin-containing cements remarkably took a long time of 13 ± 2, 32 ± 1, and 73 ± 2 min for 2, 5, 10 wt.% gelatin to harden, respectively, demonstrating adverse effect of gelatin on hardening reaction of CPCs. These values are significantly different from each other (p < 0.05).

Strength of aged cements

The added gelatin was in the range 2–10 wt.% such that the effect of the organic additive on the

Discussion

Calcium phosphate cement consists of a powder containing one or more solid compounds of calcium phosphate salts and a liquid phase that can be water or an aqueous solution. If the powder and the liquid are mixed in an appropriate ratio, they form a paste that at room or body temperature hardens by entanglement of the crystals precipitated within the paste [4], [14], [15], [16]. The setting time is one of important factors in clinical requirements. A long setting time could cause problems

Conclusion

The present study sought to investigate the effect of the gelatin amount on the properties of CPCs. In contrast to 8 min for the cement without gelatin, the setting time of gelatin cements significantly increased in the range of 13–73 min, depending on the added gelatin amount. However, the 2 wt.% gelatin can make CPCs attain the highest DTS value of 2.1 MPa at 15-day immersion among all cements, while 1.6 MPa for the cement without gelatin. This is possibly due to a better distribution of the

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Citation Excerpt :
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Immersion behavior of gelatin-containing calcium phosphate cement

Abstract

Introduction

Section snippets

Preparation of the gelatin cement

Setting time

Strength of aged cements

Discussion

Conclusion

Biomaterials

Biomaterials

Biomaterials

Biomaterials

J Biomech

Biomaterials

Biomaterials

Ceram Int

Biomaterials

Total hip replacement with fixation by acrylic cement

J Bone Joint Surg Am

The effect of methylmethacrylate on chemotaxis of polymorphonuclear leukocytes

J Bone Joint Surg

A new calcium phosphate, water-setting cement

Preparation and compressive strength of α-tricalcium phosphate/gelatin gel composite cement

J Biomed Mater Res

Non-decay type fast-setting calcium phosphate cement: hydroxyapatite putty containing an increased amount of sodium alginate

J Biomed Mater Res