Quantum Dots with Ionic Liquid as Antibacterial Agent for Adhesives

Objectives: The aim of this study was to synthesize tantalum oxide quantum dots (Ta₂O_5QDs) using an imidazolium ionic liquid and to evaluate its addition in an experimental adhesive resin on the degree of conversion (DC) and antibacterial activity.
Methods: To synthesize the Ta₂O_5QDs, 1-n-decyl-3-methylimidazolium hexachlorotantalate was prepared under argon atmosphere by mixing 1.39 g (3.88 mmol) of tantalum pentachloride (TaCl₅) and 1.00 g (3.88 mmol) of 1-n-decyl-3-methylimidazolium chloride (DMI.Cl). The mixture was kept under stirring during 30 min at 100 °C. After this period, 5 mols of deionized water was added and the system was kept under stirring for 24 h at 120 °C. The resultant powder of Ta₂O_5QDs.DMI.Cl was isolated via centrifugation, washing and drying. Ta₂O_5QDs.DMI.Cl powder was evaluated by transmission electron microscopy (TEM). The adhesive was formulatedwith 66.66 wt.% of bisphenol A glycerolate dimethacrylate (BisGMA), 33.33 wt.% of 2-hydroxyethyl methacrylate (HEMA) with a photoiniciator/co/initiator system. Ta₂O_5QDs.DMI.Cl powder was added in the adhesive at 1 wt.% (G_Ta2O5QDs) and one group remained without Ta₂O_5QDS as control (G_CTRL). The adhesives were evaluated for DC (n=3) by Fourier Transform Infrared. Direct contact inhibition assay (n=3) was used to evaluate the antibacterial activity of the experimental adhesives against biofilm formation and against planktonic bacteria.
Results: Ta₂O_5QDs.DMI.Cl showed 1.52 ± 0.73 nm by TEM.The DC was 50.91 ± 4.94 % for G_CTRL and 55.43 ± 4.58 % for G_Ta2O5QDs (p= 0.310). G_{Ta2O5QDs.DMI.Cl} showed 4.33 ± 0.55 log CFU/mL on its surface and G_CTRL showed 5.76 ± 0.15 log CFU/mL, with statistically significant difference between groups (p= 0.013). There was no statistically significant difference for antibacterial activity against the planktonic bacteria (p= 0.079).

Conclusions: Non-agglomerated Ta₂O_5QDs.DMI.Clwere synthesized with an imidazolium ionic liquid. Ta₂O_5QDs.DMI.Clprovided antibacterial activity for the experimental adhesive resin against biofilm formation of Streptococcus mutans.