Peptide Mediated Antimicrobial Dental Adhesive System

Abstract

The most common cause for dental composite failures is secondary caries due to invasive bacterial colonization of the adhesive/dentin (a/d) interface. Innate material weakness often lead to an insufficient seal between the adhesive and dentin. Consequently, bacterial by-products invade the porous a/d interface leading to material degradation and dental caries. Current approaches to achieve antibacterial properties in these materials continue to raise concerns regarding hypersensitivity and antibiotic resistance. Herein, we have developed a multi-faceted, bio-functionalized approach to overcome the vulnerability of such interfaces. An antimicrobial adhesive formulation was designed using a combination of antimicrobial peptide and a ε-polylysine resin system. Effector molecules boasting innate immunity are brought together with a biopolymer offering a two-fold biomimetic design approach. The selection of ε-polylysine was inspired due to its non-toxic nature and common use as food preservative. Biomolecular characterization and functional activity of our engineered dental adhesive formulation were assessed and the combinatorial formulation demonstrated significant antimicrobial activity against Streptococcus mutans. Our antimicrobial peptide-hydrophilic adhesive hybrid system design offers advanced, biofunctional properties at the critical a/d interface.

Keywords: adhesive formulation; antimicrobial peptide; dental composites; hybrid interface; polylysine.

Figure 1.

Antibacterial activity of chlorhexidine (CHX), antibacterial peptides and ε-polylysine S. mutans.

Figure 2.

(a) Mean residue ellipticity (MRE) of far-UV CD Spectra for GH12 and GH12-M2 with varying levels of 2,2,2-trifluoroethanol (TFE). (b) Circular dichroism spectra deconvolution through CD Pro analysis. The percentages indicate the amount of TFE in the solution.

Figure 3.

Vibration spectroscopy. (a) The molecular structure of the synthesized peptide was confirmed using FTIR. (b) GH12 to GH12-M2 peptides contained the spectral bands of 1337, 1428, and 1652 cm⁻¹ characteristic of an α-helix conformation, the CH₂CH₃ deformation, and a β-strand conformation, respectively.

Figure 4.

Analysis of secondary structure features predicted through PyRosetta method and quantified through DSSP(Define Seco ndary Structure of Proteins). (a) GH12 flexibility analysis of percentages of secondary structures (rows) occurring in the PyRosetta-generated decoys by residue calculated by DSSP. (b) GH12-M2 flexibility analysis of secondary structure of decoys by residue using PyRosetta and DSSP. (c) GH12 lowest energy score structure decoy generated through PyRosetta method. (d) GH12-M2 lowest energy structure. Green ribbon indicates the GH12 residues, and the purple ribbon indicates the modification for GH12-M2.

Figure 5.

(a) Schematic of adhesive system samples starting with commercial analogue. Experiments included the addition of GH12-M2 antimicrobial peptide onto the discs with ε-polylysine to see bacterial inhibition. As a positive control for antimicrobial activity, chlorhexidine gluconate was added at a multiple of its measured MIC value. 12.5× or greater concentration of CHX was sufficient for bacterial inhibition with or without ε-polylysine. (b) S. mutans UA159 growth/viability based on AlamarBlue assay on dental adhesive discs soaked with either an antimicrobial peptide or a chlorhexidine aqueous solution as a multiple of minimum inhibitory concentration.