Mechanical and suture-holding properties of a UV-cured atelocollagen membrane with varied crosslinked architecture

The mechanical competence and suturing ability of collagen-based membranes are paramount in guided bone regeneration (GBR) therapy, to ensure damage-free implantation, fixation and space maintenance in vivo. However, contact with the biological medium can induce swelling of collagen molecules, yielding risks of membrane sinking into the bone defect, early loss of barrier function, and irreversibly compromised clinical outcomes. To address these challenges, this study investigates the effect of the crosslinked network architecture on both mechanical and suture-holding properties of a new atelocollagen (AC) membrane. UV-cured networks were obtained via either single functionalisation of AC with 4-vinylbenzyl chloride (4VBC) or sequential functionalisation of AC with both 4VBC and methacrylic anhydride. The wet-state compression modulus (E-c) and swelling ratio (SR) were significantly affected by the UV-cured network architecture, leading up to a three-fold reduction in SR and about two-fold increase in E-c in the sequentially functionalised, compared to the single-functionalised, samples. Electron microscopy, dimensional analysis and compression testing revealed the direct impact of the ethanol series dehydration process on membrane microstructure, yielding densification of the freshly synthesised porous samples and a pore-free microstructure with increased E-c. Nanoindentation tests via spherical bead-probe atomic force microscopy (AFM) confirmed an approximately two-fold increase in median (interquartile range (IQR)) elastic modulus in the sequentially functionalised (E-AFM = 40 (13) kPa), with respect to single-functionalised (E-AFM = 15 (9) kPa), variants. Noteworthy, the single-functionalised, but not the sequentially functionalised, samples displayed higher suture retention strength (SRS = 28 +/- 2-35 +/- 10 Nmm(-1)) in both the dry state and following 1 h in phosphate buffered saline (PBS), compared to Bio-Gide (R) (SRS: 6 +/- 1-14 +/- 2 Nmm(-1)), while a significant decrease was measured after 24 h in PBS (SRS= 1 +/- 1 Nmm(-1)). These structure-property relationships confirm the key role played by the molecular architecture of covalently crosslinked collagen, aimed towards long-lasting resorbable membranes for predictable GBR therapy.