Bismuth Quantum Dot (Bi QD)/Polydimethylsiloxane (PDMS) Nanocomposites with Self-Cleaning and Antibacterial Activity for Dental Applications

Abstract

In the oral microenvironment, bacteria colonies are easily aggregated on the tooth-restoration surface, in the manner of a biofilm, which usually consists of heterogeneous structures containing clusters of a variety of bacteria embedded in an extracellular matrix, leading to serious recurrent caries. In this contribution, zero-dimensional (0D) bismuth (Bi) quantum dots (QDs) synthesized by a facile solvothermal method were directly employed to fabricate a Bi QD/polydimethylsiloxane (PDMS)-modified tooth by simple curing treatment. The result demonstrates that the as-fabricated Bi QD/PDMS-modified tooth at 37 °C for 120 min not only showed significantly improved hydrophobic performance with a water contact angle of 103° and 115° on the tooth root and tooth crown, respectively, compared to that (~20° on the tooth root, and ~5° on the tooth crown) of the pristine tooth, but also exhibited excellent antibacterial activity against S. mutans, superior biocompatibility, and biosafety. In addition, due to the highly photothermal effect of Bi QDs, the antibacterial activity of the as-fabricated Bi QD/PDMS-modified tooth could be further enhanced under illumination, even at a very low power density (12 mW cm^-2). Due to the facile fabrication, excellent hydrophobicity, superior antibacterial activity, and biocompatibility and biosafety of the Bi QD/PDMS-modified tooth, it is envisioned that the Bi QD/PDMS-modified tooth with a fascinating self-cleaning and antibacterial performance can pave the way to new designs of versatile multifunctional nanocomposites to prevent secondary caries in the application of dental restoration.

Keywords: antibacterial; bismuth; nanocomposite; quantum dots; self-cleaning.

Figure 1

The schematic diagram of the Bi QD/PDMS-modified tooth with both self-cleaning and antibacterial activity.

Figure 2

Structural characterization. (a) TEM image and (b) HRTEM image of the as-synthesized 0D Bi QDs, (c) AFM image and (d) the corresponding height profile of the 0D Bi QDs, (e) Raman spectra of bulk Bi and 0D Bi QDs, and (f) UV-Vis-NIR spectrum.

Figure 3

The change of θ and morphology after the modification of pristine tooth. The pictures for θ on the tooth root for (a) pristine tooth, (b) PDMS-modified tooth and (c) Bi QD/PDMS-modified tooth; the pictures for θ on the tooth crown for (d) pristine tooth, (e) PDMS-modified tooth and (f) Bi QD/PDMS-modified tooth. (g) The picture for real pristine tooth and modified tooth.

Figure 4

The influence of curing time and temperature on the hydrophobic performance of the as-fabricated Bi QDs/PDMS nanocomposites on the tooth. The θ on the (a) tooth root and (b) tooth crown as a function of curing temperature, and pictures for θ on the (c) tooth root and (d) tooth crown at different curing temperatures for 120 min. The θ on the (e) tooth root and (f) tooth crown as a function of curing time, and pictures for θ on the (g) tooth root and (h) tooth crown at different curing times at the curing temperature of 37 °C.

Figure 5

The influence of the Bi QDs content in the Bi QD/PDMS nanocomposite on the antibacterial performance. Plate photographs of S. mutans after incubated for 24 h under dark: (a) control, (b) 0 ppm Bi QDs, (c) 200 ppm Bi QDs, (d) 400 ppm Bi QDs, and (e) 800 ppm. SEM image of S. mutans under dark: (f) control, (g) 0 ppm Bi QDs, (h) 200 ppm Bi QDs, (i) 400 ppm Bi QDs, and (j) 800 ppm. (k) Data statistics from the SEM image.

Figure 6

The antibacterial performance of the Bi QD/PDMS-modified tooth. Plate photographs of S. mutans for the Bi QD/PDMS-modified tooth incubated for 24 h (a) in the dark and (b) under light with a power density of 12 mW cm⁻². (c) The comparison of the antibacterial performance for the Bi QD/PDMS-modified tooth with 400 ppm Bi QDs in the Bi QD/PDMS nanocomposite.

Figure 7

Cytotoxicity of the Bi QD/PDMS-modified tooth with different concentrations of Bi QDs toward (a) periodontal ligament fibroblasts and (b) periodontal ligament stem cells. The two curves are normalized based on the control groups. (c) Live/dead fluorescence images for the periodontal ligament fibroblast cell viability treated by Bi QD/PDMS-modified tooth with different concentrations of Bi QDs for 24 h in the dark. The periodontal ligament fibroblast cells were stained by Calcein-AM/PI Double Stain kit.