Ternary thiol–ene systems as high-performance bone adhesives for potential clinical use†

Abstract

The vision of using bone adhesives for adjunct surgical treatment of complicated fractures or facile reattachment of bone fragments is highly attractive, as compared to conventional techniques, it is expected to significantly reduce operation times and potentially avoid the need for revision surgeries. Nevertheless, no commercial adhesives, that combine biocompatibility, sufficient bonding strength, and time-efficient, implementable fixation protocols are available yet. Inspired by self-etching dental restoratives, we present the development of novel adhesive molecules, so-called primers, containing adhesion motifs for high binding affinity to bone and implants and co-polymerizable groups for incorporation into the adhesive matrix. By efficient design of this primer molecule with regards to spacer length and type and number of polymerizable groups, we were able to develop the first-known one-step in situ photocurable adhesive system, based on thiol–ene chemistry with a shear bond strength comparable to dental adhesives. Unprecedented shear bond strength on bone was determined with the optimized system, which surpasses the state-of-the-art thiol–ene adhesive reported in literature by more than 70%. Good in vitro biocompatibility of the novel primer was determined, and, remarkably, first ex vivo indentation tests on the calvariae of rats revealed exceptional adhesive performance with failure of the calvariae instead of the adhesive. Due to combining practicability and applicability, this adhesive system might pave the way towards the future of adjunct fracture treatment, with applications such as the fixation of comminuted fractures, small or thin bone fragments, or the additional fixation of implants.