A Bone Glue with Sustained Adhesion under Wet Conditions

Abstract

Bone glues often suffer from low adhesion to bone under wet conditions. This study aims to improve wet adhesiveness of a bone glue based on a photocurable poly(ethylene glycol) dimethacrylate matrix through in situ interpenetrating network formation by addition of six-armed isocyanate functional star-shaped prepolymers (NCO-sP(EO-stat-PO)). Biodegradable ceramic fillers are added to adjust the paste workability. The 3-point bending strength of the bone glues is in the range of 3.5-5.5 MPa and not significantly affected by the addition of NCO-sP(EO-stat-PO). Storage in phosphate buffered saline (PBS) decreases the bending strength of all formulations to approximately 1 MPa but the adhesion to cortical bone increases from 0.15-0.2 to 0.3-0.5 MPa after adding 20-40 wt% NCO-sP(EO-stat-PO) to the matrix. Bone glues without the NCO-sP(EO-stat-PO) additive lose their adhesiveness to bone after aging in PBS for 7 days, whereas modified glues maintain a shear strength of 0.18-0.25 MPa demonstrating the efficacy of the approach. Scanning electron microscopy and energy-dispersive X-ray spectroscopy investigations of the fracture surfaces prove a high amount of residual adhesive on the bone surface indicating that adhesion to the bone under wet conditions is stronger than cohesion.

Bone‐Adhesive Materials: Clinical Requirements, Mechanisms of Action, and Future Perspective

“…In 2005, Heiss et al described a bone‐adhesive system based on a low molecular weight alkylene bis(dilactoyl)methacrylate polymer, which polymerizes upon light irradiation to form highly branched, hydrolysable, biodegradable networks. Initially, the biocompatibility and adhesion to bone were reported as favorable, while its degradation did not interfere with physiological fracture healing .…”

“…In 2017, Wistlich et al attempted to improve the adhesion under wet conditions of a bone glue based on a photocurable poly(ethylene glycol) dimethacrylate (PEGDMA) matrix. An interpenetrating network (IPN) was formed in situ by addition of isocyanate (NCO) functional six‐armed star‐shaped prepolymer with ethylene oxide (EO) and propylene oxide (PO) statistically copolymerized in the backbone in a ratio of 4:1 (NCO‐sP(EO‐ stat ‐PO)), as depicted in Figure . To adjust the workability, biodegradable inorganic fillers such as Mg 3 (PO 4 ) 2 and/or MgNH 4 PO 4 ·6H 2 O were added to the glue.…”

“…Schematic representation of the design of a bone glue based on a photocurable PEGDMA matrix, NCO‐sP(EO‐ stat ‐PO) and a ceramic filler. Reproduced with permission . Copyright 2016, Wiley‐VCH Verlag GmbH & Co. KGaA.…”

Current State of Bone Adhesives—Necessities and Hurdles

“…Wistlich et al reported a photochemically curing system consisting of a poly(ethylene glycol) dimethacrylate matrix and a six-armed isocyanate functional starshaped prepolymer that, in situ, undergoes an interpenetrating network enriched with biodegradable ceramic fillers. The use of 20–40 wt% isocyanate (NCO) terminated prepolymer improved the adhesion strength to cortical bone after storage in buffered saline by a factor of 2 (0.15–0.2 to 0.3–0.5 MPa) [81]. The histological and biomechanical evaluation of N-butyl-2-cyanoacrylate as a bone adhesive in an animal study showed that the adhesive is as effective as plates and screws in surgically fabricated osteotomy fixations [82].…”

Magnesium Phosphate Cement as Mineral Bone Adhesive

“…In particular, in the first case, the adhesive material must not impair fracture healing by forming a rigid barrier, which is enabled while applying the bone adhesive only selectively or by using biodegradable materials. Recent approaches to create bone adhesives include cyanoacrylates [3,4], methacrylates [5,6,7], fibrin glue [8], mussel proteins and dopamine hydrogels [9,10,11], or polysaccharides [12,13,14]. Most synthetic materials that have been tested as bone-bonding agents, are either mechanically weak with insufficient adhesion to the bone surface or do not fulfill the requirement of biodegradability, as for example poly(methyl methacrylate) (PMMA), cyanoacrylates and its associated formulations [15].…”