IADR Abstract Archives
Metal-Organic Frameworks as Smart Carriers of Bioactives in Dentin Adhesives
Objectives: Restorative materials capable of delivering antimicrobial, anti-proteolytic and crosslinking agents offer promise for preventing bacteria-induced secondary caries and hybrid layer degradation. Here, quercetin (QCT) – a flavonoid with therapeutic potentials relevant to the oral environment – was encapsulated within metal-organic frameworks (MOFs) to address a concept of on-demand release of bioactives from restorative materials to the tooth. The main goals were to verify the applicability of a biocompatible MOF (ZIF-8) as pH-sensitive carrier of QCT, as well as evaluate the effect of incorporation of QCT@ZIF-8 microparticles on the polymerization kinetics of an experimental adhesive.
Methods: QCT was encapsulated in the frameworks through a water-based, one-step synthetic process. The resulting QCT@ZIF-8 microparticles were analyzed with respect to chemical composition, crystal structure, thermal behavior, micromorphology and release profile under acidic and physiological conditions. Different amounts of microparticles (10–50 mg/mL) were incorporated into an experimental adhesive consisting of HEMA and BisGMA (mass ratio of 45:55) and a two-component photoinitiator system. The degree of conversion (DC) of methacrylic double bonds was determined by FTIR spectroscopy and attenuated total reflectance. DC data were analyzed with ANOVA and Tukey’s post hoc test (α=0.05).
Results: Crystalline QCT@ZIF-8 particles with attractive loading capacities (up to 10.4%), submicron sizes, high thermal stability and responsiveness to pH change were successfully manufactured. Under acidic condition (pH 5.2), a complete (100%) release of QCT was promptly induced. Essentially, the concentration of QCT@ZIF-8 in the resin was a key factor affecting the conversion plateau and rate of polymerization: with increasing the QCT@ZIF-8 content, both the final extent of conversion and the rate decreased (Fig. 1).
Conclusions: In-situ encapsulation of QCT in pH-sensitive ZIF-8 matrices can be easily achieved. The concentration of QCT@ZIF-8 in the resin is relevant, mainly because premature release of QCT may affect the free radical polymerization due to the flavonoid’s remarkable antioxidant activity.
Methods: QCT was encapsulated in the frameworks through a water-based, one-step synthetic process. The resulting QCT@ZIF-8 microparticles were analyzed with respect to chemical composition, crystal structure, thermal behavior, micromorphology and release profile under acidic and physiological conditions. Different amounts of microparticles (10–50 mg/mL) were incorporated into an experimental adhesive consisting of HEMA and BisGMA (mass ratio of 45:55) and a two-component photoinitiator system. The degree of conversion (DC) of methacrylic double bonds was determined by FTIR spectroscopy and attenuated total reflectance. DC data were analyzed with ANOVA and Tukey’s post hoc test (α=0.05).
Results: Crystalline QCT@ZIF-8 particles with attractive loading capacities (up to 10.4%), submicron sizes, high thermal stability and responsiveness to pH change were successfully manufactured. Under acidic condition (pH 5.2), a complete (100%) release of QCT was promptly induced. Essentially, the concentration of QCT@ZIF-8 in the resin was a key factor affecting the conversion plateau and rate of polymerization: with increasing the QCT@ZIF-8 content, both the final extent of conversion and the rate decreased (Fig. 1).
Conclusions: In-situ encapsulation of QCT in pH-sensitive ZIF-8 matrices can be easily achieved. The concentration of QCT@ZIF-8 in the resin is relevant, mainly because premature release of QCT may affect the free radical polymerization due to the flavonoid’s remarkable antioxidant activity.
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