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Adhesion of Oral Bacteria to Commercial d-PTFE Membranes: Polymer Microstructure Makes a Difference
Gabrijela Begić1, Mirna Petković Didović2, Sanja Lučić Blagojević3
1Department of Microbiology and Parasitology, Faculty of Medicine, University of Rijeka, 51000 Rijeka, Croatia.
Abstract:
Bacterial contamination of the membranes used during guided bone regeneration directly influences the outcome of this procedure. In this study, we analyzed the early stages of bacterial adhesion on two commercial dense polytetrafluoroethylene (d-PTFE) membranes in order to identify microstructural features that led to different adhesion strengths. The microstructure was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR). The surface properties were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), and surface free energy (SFE) measurements. Bacterial properties were determined using the microbial adhesion to solvents (MATS) assay, and bacterial surface free energy (SFE) was measured spectrophotometrically. The adhesion of four species of oral bacteria (Streptococcus mutans, Streptococcus oralis, Aggregatibacter actinomycetemcomitas, and Veilonella parvula) was studied on surfaces with or without the artificial saliva coating. The results indicated that the degree of crystallinity (78.6% vs. 34.2%, with average crystallite size 50.54 nm vs. 32.86 nm) is the principal feature promoting the adhesion strength, through lower nanoscale roughness and possibly higher surface stiffness. The spherical crystallites ("warts"), observed on the surface of the highly crystalline sample, were also identified as a contributor. All bacterial species adhered better to a highly crystalline membrane (around 1 log10CFU/mL difference), both with and without artificial saliva coating. Our results show that the changes in polymer microstructure result in different antimicrobial properties even for chemically identical PTFE membranes.
Insights
Microstructure, not chemical identity, dictates bacterial adhesion to dense polytetrafluoroethylene (d-PTFE) membranes. Higher crystallinity in d-PTFE membranes significantly increases bacterial adhesion, impacting guided bone regeneration outcomes.
Area of Science:
- Biomaterials Science
- Microbiology
- Polymer Science
Background:
- Bacterial contamination of membranes is a critical factor in guided bone regeneration (GBR) success.
- Understanding bacterial adhesion mechanisms on GBR membranes is essential for improving clinical outcomes.
Purpose of the Study:
- To investigate the relationship between the microstructure of dense polytetrafluoroethylene (d-PTFE) membranes and the strength of early bacterial adhesion.
- To identify specific microstructural features influencing bacterial adhesion on d-PTFE membranes.
Main Methods:
- Characterization of d-PTFE membrane microstructure using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy.
- Surface property analysis via atomic force microscopy (AFM), scanning electron microscopy (SEM), and surface free energy (SFE) measurements.
- Assessment of bacterial adhesion using the microbial adhesion to solvents (MATS) assay and spectrophotometric measurement of bacterial SFE for four oral bacterial species.
Main Results:
- A higher degree of crystallinity (78.6% vs. 34.2%) in d-PTFE membranes correlated with significantly increased bacterial adhesion (approx. 1 log10 CFU/mL difference).
- Lower nanoscale roughness and potentially higher surface stiffness associated with higher crystallinity contributed to enhanced bacterial adhesion.
- Spherical crystallites observed on highly crystalline surfaces also promoted bacterial adhesion.
- All tested bacterial species (Streptococcus mutans, Streptococcus oralis, Aggregatibacter actinomycetemcomitas, Veilonella parvula) adhered more strongly to highly crystalline membranes, irrespective of artificial saliva coating.
Conclusions:
- The microstructure, specifically the degree of crystallinity, is a primary determinant of bacterial adhesion strength on d-PTFE membranes.
- Changes in polymer microstructure can lead to distinct antimicrobial properties even in chemically identical PTFE membranes.
- These findings highlight the importance of considering membrane microstructure in the design of materials for guided bone regeneration to minimize bacterial contamination.
