Novel high-strength bioabsorbable bone adhesives

Abstract

Event Abstract Back to Event Novel high-strength bioabsorbable bone adhesives Antony Bou-Francis1 and Amyl Ghanem1 1 Dalhousie University, Department of Process Engineering & Applied Science, Canada The idea of being able to glue bone fragments with a suitable bicompatible adhesive remains highly attractive to orthopaedic surgeons[1]. Despite decades of research, no suitable system that fully satisfies all the many requirements for such an adhesive has yet been identified[2]. We propose novel high-strength bioabsorbable bone adhesives based on polycaprolactone (PCL), polyglycolide (PGA) and beta-tricalcium phosphate (β-TCP) blends. Figure 1. The polymer blends tested for adhesive strength and water uptake. All materials used to prepare the blends were medical grade. PCL and PGA were obtained from Purac, The Netherlands. β-TCP was obtained from Berkeley Advanced Biomaterials, USA. Five polymer blends (Figure 1) were prepared and mixed manually in a vial then molded into glue-stick cylinders using injection molding (Arburg Polytronica, Germany). All blends were comparatively tested for adhesive strength and water uptake. Bovine bone samples were obtained from a local abattoir and cut into 50 mm x 15 mm x 10 mm (L x W x D) rectangular sections. A glue gun (Ad Tech, China) was then used to apply the blends and adhere the samples as per the configurations shown in Figure 2. The adhered samples were cured at 37°C for 24 hours then loaded in tension (Instron, USA) at a crosshead control rate of 1.3 mm/min until failure[3]. The maximum shear stress was calculated by dividing the maximum force by the shear area. Experiments were repeated three times and the shear stress was reported as mean ± standard deviation. Water uptake tests were performed according to ASTM D570. The glue sticks of the different polymer blends were cut into circular pieces, dried overnight at 40°C, then immersed in distilled water at room temperature. Water uptake for different swelling times was measured as percent uptake = [(mwet - mdry) / mdry] x 100. Six samples were tested for each blend and the percent water uptake versus immersion time was reported as mean ± standard deviation. Figure 2. The test configurations for assessing the adhesive strength of the polymer blends. A) Lateral view showing the position of the samples based on lap shear strength assessment with a 300 mm2 adhesion area. B) Top view showing the position of the samples based on assessing tissue-adhesive strength under tension with a 150 mm2 adhesion area. The bond strength experiments revealed that, independent of the test configuration, blend 1 and blend 2 exhibited the lowest and highest maximum shear stress, respectively. The measured shear stress for blends 1 to 5 were 1.63 ± 0.39, 3.31 ± 0.36, 2.53 ± 0.42, 1.95 ± 0.35, and 2.37 ± 0.38 MPa, respectively. The water uptake experiments (Figure 3) revealed that, for all the swelling times tested, blend 1 and blend 4 had the lowest and highest water absorption rates, respectively. After 24 hours of immersion in distilled water, the percent water uptake for blends 1 to 5 were 0.34 ± 0.05, 0.48 ± 0.04, 0.58 ± 0.03, 1.17 ± 0.07, and 0.61 ± 0.05 %, respectively. Figure 3. Moisture absorption of different polymer blends for up to 72 hours of immersion in distilled water. This study shows that the incorporation of PGA and TCP with PCL seems to improve the adhesive strength and water absorption properties of the polymer blends. More experiments are needed to elucidate this hypothesis and help determine the suitability of such polymer blends as high-strength bioabsorbable bone adhesives. Mitacs; Dartmouth Medical Research Limited