Abstract

Event Abstract Back to Event Photochemically crosslinked methacrylate / isocyanate-containing bone adhesive with degradable ceramic fillers Laura Wistlich1, Anja Rücker1, Jürgen Groll1 and Uwe Gbureck1 1 University Hospital Würzburg, Department for Functional Materials in Medicine and Dentistry, Germany Introduction: Currently used bone glues often suffer from a low adhesion to bone due to the wet environmental conditions at the application site[1]. This study aimed to develop a bone glue based on a polyethylene-dimethacrylate (PEGDMA) matrix with the addition of six-armed star-shaped prepolymers containing isocyanate groups (NCO-sP(EO-stat-PO)) to improve the adhesiveness to bone. Furthermore, the addition of degradable ceramic fillers based on calcium sulfate or magnesium phosphates is thought to increase porosity following implantation to achieve ingrowth of new bone material[2]. Materials and Methods: The star-shaped prepolymers were added to an organic phase containing PEGDMA, campherquinone as radical initiator and N,N,N´,N´-Tetramethylethylenediamine (TEMED) as activator. After mixing with inorganic mineral fillers such as gypsum, newberyite and struvite, the bone glues were photochemically crosslinked at a wavelength of 385-515 nm. The materials were tested regarding their polymerization reaction, mechanical properties as well as their adhesion to bovine cortical bone before and after storage in PBS for 7 days. Results and Discussion: The 3-point bending strength of the bone glues was in the range of 3.5-5.5 MPa, whereas the addition of (NCO-sP(EO-stat-PO)) only marginally affected strength. Storage in PBS decreased the bending strength to ~1 MPa independent of the ceramic fillers. The adhesion to cortical bone was initially in a range of 0.15-0.2 MPa without additive, which increased to 0.3-0.5 MPa after adding 20-40 wt% (NCO-sP(EO-stat-PO)) to the matrix (Fig. 1). Bone glues without additive lost their adhesiveness to bone after ageing in PBS for 7d, whereas the modified glues maintained a shear strength of approx. 0.18-0.25 MPa demonstrating the efficacy of the approach (Fig. 2). SEM and EDX investigations of the fracture surfaces demonstrated a high amount of residual glue on the bone surface and hence revealed a cohesive failure within the glue. Conclusion: It is well known from technical applications that isocyanate containing glues have an improved adhesiveness under wet conditions[3]. This was transferred in the current study to (NCO-sP(EO-stat-PO)) containing bone glues. These functional additives have a comparable low cytotoxicity due to their high molecular weight and lead to a crosslinking of their isocyanate groups in water building up urea bridges. This significantly increased the bonding ability of photochemically crosslinked PEGDMA matrix to bone even after storage in PBS for up to 7d.

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