Dual-Functionality Evaluation of a Novel Collagen Crosslinking Resin

Abstract

Current adhesives bond to dentin via a micro-interlocking mechanism within the hybrid layer. Besides such mechanical retention, bonding to dentin would benefit from additional chemical interaction between collagen and resin. This study aims to synthesize a novel light-curable collagen crosslinker methacrylate (MA) functionalized grapeseed extract (GSE) and to assess MAGSE’s ability to crosslink dentin collagen in a clinically relevant setting as well as its role in light-cure as a resin. MA functionalization was accomplished by reacting GSE with methacryloyl chloride to obtain MAGSE, which was characterized by ¹H-NMR and Fourier transformed infrared spectroscopy (FTIR). The 6-µm-thick dentin films were microtomed from dentin slabs of third molars. Following demineralization, they were treated for 30 s by 1% MAGSE. Collagen crosslinking and resistance to digestion of MAGSE were evaluated by FTIR, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF) assay of films, and scanning electron microscopy (SEM)/transmission electron microscopy (TEM) on slabs. Meanwhile, 1% MAGSE or GSE was added to an experimental adhesive formulated with 2-hydroxyethyl methacrylate and a tricomponent photoinitiator system. Polymerization kinetics were monitored continuously in real time for 10 min using FTIR–attenuated total reflection. The results indicated that MAGSE could bind to dentin collagen and protect it from collagenase degradation as strong as GSE. Dentin collagen treated by 1% MAGSE for 30 s was scarcely digested (1.6 ± 1.6%) after 1 h in 0.1% collagenase, while untreated collagen was completely digested (100.9 ± 20.2%). SEM/TEM images indicated MAGSE efficiently crosslinked dentin collagen in 30 s and rendered it almost inert to digestion under clinically relevant settings. Unlike GSE that hindered light-curing of HEMA, MAGSE accelerated the rate of polymerization and exhibited typical traits of a resin monomer with multiple polymerizable units. In conclusion, a novel collagen crosslinking resin MAGSE is synthesized, which inherits collagen crosslinking ability from GSE and polymerization function from MA. Inclusion of this light-curable collagen crosslinker into adhesives might be a revolutionary way to improve durability of dentin bonding in composite restorations.