Chitosan Enhances the Anti-Biofilm Activity of Biodentine against an Interkingdom Biofilm Model

The Effect of Chitosan Incorporation on Physico-Mechanical and Biological Characteristics of a Calcium Silicate Filling Material

OBJECTIVES

A tricalcium silicate-based cement, Biodentine™, has displayed antibiofilm activity when mixed with chitosan powder. This study aimed to assess the effect of chitosan incorporation on the physico-mechanical and biological properties of Biodentine™.

METHODS

In this study, medium molecular weight chitosan powder was incorporated into Biodentine™ in varying proportions (2.5 wt%, 5 wt%, 10 wt%, and 20 wt%). The setting time was determined using a Vicat apparatus, solubility was assessed by calculating weight variation after water immersion, radiopacity was evaluated and expressed in millimeters of aluminum, the compressive strength was evaluated using an Instron testing machine, and the microhardness was measured with a Vickers microhardness tester. In addition, surface topography of specimens was analyzed using scanning electron microscopy, and the effect of chitosan on the viability of human embryonic kidney (HEK 293) cells was measured by a colorimetric MTT assay.

RESULTS

Incorporation of 2.5 wt% and 5 wt% chitosan powder delivered an advantage by speeding up the setting time of Biodentine material. However, the incorporation of chitosan compromised all other material properties and the crystalline structure in a dose-dependent manner. The chitosan-modified material also showed significant decreases in the proliferation of the HEK 293 cells, signifying decreased biocompatibility.

SIGNIFICANCE

Chitosan incorporation into calcium silicate materials adversely affects the physical and biological properties of the material. Despite the increased antimicrobial activity of the modified material, the diminution in these properties is likely to reduce its clinical value.

Specimen Shape and Elution Time Affect the Mineralization and Differentiation Potential of Dental Pulp Stem Cells to Biodentine

The liquid extract method is commonly used to evaluate the cytotoxicity and bioactivity of materials. Although ISO has recommended guidelines for test methods, variations in elution period, and shape of samples can influence the biological outcomes. The aim of this study was to investigate the influence of material form and elution period of Biodentine on dental pulp stem cells (DPSCs)' proliferation and mineralization. Biodentine (0.2 g) discs or powder were immersed in culture media (10 mL) for 1, 3 or 7 days (D1, D3 and D7). The eluents were filtered and used to treat DPSC. The calcium release profile and pH were determined. Cell proliferation was evaluated by MTS for 3 days, and mineralization and differentiation were assessed by alizarin red S staining (Ca2+/ng of DNA) and qRT-PCR (MEPE, DSPP, DMP-1, RUNX2, COL-I and OCN) for 14 days. Statistical analysis was performed with a one or two-way ANOVA and post hoc Tukey's test (pH, calcium release and proliferation) or Mann-Whitney test (α = 0.05). pH and calcium ion release of powdered eluents were significantly higher than disc eluents. Powdered eluent promoted extensive cell death, while the disc form was cytocompatible. All disc eluents significantly increased the gene expression and mineralization after 14 days compared to the untreated control. D7 induced less mineralization and differentiation compared to D1 and D3. Thus, the materials' form and elution time are critical aspects to be considered when evaluating the bioactivity of materials, since this binomial can affect positively and negatively the biological outcomes.

Action of chitosan-based solutions against a model four-species biofilm formed on cobalt-chromium and acrylic resin surfaces

OBJECTIVE

To evaluate the anti-biofilm action of chitosan, nanoparticulate chitosan, and denture cleanser Nitradine™ against biofilms comprising Candida albicans, Candida glabrata, Staphylococcus aureus, and Streptococcus mutans.

BACKGROUND

Biofilm removal from removable partial dentures (RPD) is important for success in prosthetic rehabilitation.

MATERIALS AND METHODS

The anti-biofilm action of the experimental chitosan-based solutions and Nitradine™ was evaluated on acrylic resin and cobalt-chromium alloy through assessing cell viability, cell metabolism, residual aggregated biofilm, and extracellular polymeric substance and biofilm morphology.

RESULTS

Only chitosan reduced the viability of C. albicans on cobalt-chromium alloy surface, by 98% (a 1.7 log10 reduction in cfu). Chitosan-based solutions neither promoted substantial alteration of the metabolic activity of the four-species biofilm nor reduced the amount of the aggregated biofilm. After immersion in chitosan and nanoparticulate chitosan, viable microorganisms and extracellular polymeric substances distributed over the entire specimens' surfaces were observed. Nitradine™ reduced the viability and metabolic activity of biofilm grown on both surfaces, but it did not remove all aggregated biofilm and extracellular polymeric substances. After immersion in Nitradine™, approximately 35% of the specimens' surfaces remained covered by aggregated biofilm, mainly composed of dead cells.

CONCLUSION

Although chitosan and Nitradine™ promoted changes in the viability of microorganisms, neither solution completely removed the four-species biofilm from the Co-Cr and acrylic resin surfaces. Thus, isolated use of hygiene solutions is not indicated for biofilm control on RPDs; this requires complementary mechanical removal.

Investigating the role of Candida albicans as a universal substrate for oral bacteria using a transcriptomic approach: implications for interkingdom biofilm control?

Candida albicans is frequently identified as a colonizer of the oral cavity in health and has recently been termed a "keystone" commensal due to its role on the bacterial communities. However, the role that C. albicans plays in such interactions is not fully understood. Therefore, this study aimed to identify the relationship between C. albicans and bacteria associated with oral symbiosis and dysbiosis. To do this, we evaluated the ability of C. albicans to support the growth of the aerobic commensal Streptococcus gordonii and the anaerobic pathogens Fusobacterium nucleatum and Porphyromonas gingivalis in the biofilm environment. RNA-Sequencing with the Illumina platform was then utilized to identify C. albicans gene expression and functional pathways involved during such interactions in dual-species and a 4-species biofilm model. Results indicated that C. albicans was capable of supporting growth of all three bacteria, with a significant increase in colony counts of each bacteria in the dual-species biofilm (p < 0.05). We identified specific functional enrichment of pathways in our 4-species community as well as transcriptional profiles unique to the F. nucleatum and S. gordonii dual-species biofilms, indicating a species-specific effect on C. albicans. Candida-related hemin acquisition and heat shock protein mediated processes were unique to the organism following co-culture with anaerobic and aerobic bacteria, respectively, suggestive that such pathways may be feasible options for therapeutic targeting to interfere with these fungal-bacterial interactions. Targeted antifungal therapy may be considered as an option for biofilm destabilization and treatment of complex communities. Moving forward, we propose that further studies must continue to investigate the role of this fungal organism in the context of the interkingdom nature of oral diseases.

Molecular mechanisms of the antibacterial activity of polyimide fibers in a skin-wound model with Gram-positive and Gram-negative bacterial infection in vivo

Recently, the need for antibacterial dressings has amplified because of the increase of traumatic injuries. However, there is still a lack of ideal, natural antibacterial dressings that show an efficient antibacterial property with no toxicity. Polyimide (PI) used as an implantable and flexible material has been recently reported as a mixture of particles showing more desirable antibacterial properties. However, we have identified a novel type of natural polyimide (PI) fiber that revealed antibacterial properties by itself for the first time. The PI fiber material is mainly composed of C, N, and O, and contains a small amount of Ca and Cl; the characteristic peaks of polyimide appear at 1774 cm-1, 1713 cm-1, 1370 cm-1, 1087 cm-1, and 722 cm-1. PI fibers displayed significant antibacterial activities against Escherichia coli (as a Gram-negative bacteria model) and methicillin-resistant Staphylococcus aureus (MRSA, as a Gram-positive bacteria model) according to the time-kill kinetics in vitro, and PI fibers damaged both bacterial cell walls directly. PI fibers efficiently ameliorated a local infection in vivo, inhibited the bacterial burden, decreased infiltrating macrophages, and accelerated wound healing in an E. coli- or MRSA-infected wound model. In conclusion, PI fibers used in the present study may act as potent antibacterial dressings protecting from MRSA or E. coli infections and as promising candidates for antimicrobial materials for trauma and surgical applications.