Proanthocyanidins’ efficacy in stabilizing dentin collagen against enzymatic degradation: MALDI-TOF and FTIR analyses

Abstract Objectives To investigate grape seed extract proanthocyanidins’ (PA) capability in improving dentin collagen's sustainability in an enzymatic environment, given that the size and shape of the collagen samples, and the manner to apply PA are both clinically relevant. Methods Human dentin was sectioned into 6-μm-thick films. After demineralisation in 35 wt% phosphoric acid for 15 s, the films were subject to 30 s of treatment at PA concentrations of 0% (control), 0.5%, 1%, 2%, 3.75%, 7.5% and 15% (w/w), respectively. The films were then digested in 0.1 wt% collagenase for 1 h and 24 h. The amount of degraded collagen in the liquid digests was determined by MALDI-TOF mass spectroscopy. The trend of PA's incorporation into dentin collagen was analysed by ATR-FTIR. Results The control exhibited complete digestion in 1 h. In contrast, collagen treated with 0.5% and 1% PA afforded 13.84 ± 4.69% and an undetectable level of degradation, respectively in the first 1 h of digestion, and additional 17.48 ± 4.38% and 4.50 ± 1.68%, respectively in the following 23 h. Collagen treated with ≥2 wt% PA was not significantly digested regardless of digestion time. FTIR spectroscopy revealed that PA incorporation was saturated at ≥2 wt% PA. Conclusion Thirty seconds of PA treatment at 2 wt% and above could provide optimal protection for dentin collagen against collagenase digestion. Clinical significance This study demonstrated PA's extraordinary efficiency in stabilizing demineralised dentin collagen when it is applied in a clinical relevant manner, and identified the optimal conditions for its utilization.