Antibacterial effect of chitosan and its derivative on Enterococcus faecalis associated with endodontic infection

The effect of the enzymes trypsin and DNase I on the antimicrobial efficiency of root canal irrigation solutions

The purpose of this study was to evaluate the antibacterial efficacy of using 2.5% NaOCl, 2% chlorhexidine (CHX), Irritrol, and chitosan-coated silver nanoparticles (AgCNPs) alone or in combination with deoxyribonuclease I (DNase I) and trypsin pre-enzyme applications in dentin samples contaminated with Enterococcus faecalis (E. faecalis) by CLSM. 144 dentin blocks with confirmed E. faecalis biofilm formation were divided randomly according to the irrigation protocol (n = 12): NaOCl, CHX, Irritrol, AgCNPs, trypsin before NaOCl, CHX, Irritrol, AgCNPs, and DNase I before NaOCl, CHX, Irritrol, AgCNPs. Dentin blocks were stained with the Live/Dead BacLight Bacterial Viability Kit and viewed with CLSM after irrigation applications. The percentage of dead and viable bacteria was calculated using ImageJ software on CLSM images. At a significance level of p < 0.05, the obtained data were analyzed using one-way Anova and post-hoc Tukey tests. In comparison with NaOCl, CHX had a higher percentage of dead bacteria, both when no pre-enzyme was applied and when DNase I was applied as a pre-enzyme (p < 0.05). There was no difference in the percentage of dead bacteria between the irrigation solutions when trypsin was applied as a pre-enzyme (p > 0.05). AgCNPs showed a higher percentage of dead bacteria when trypsin was applied as a pre-enzyme compared to other irrigation solutions (p < 0.05), while the pre-enzyme application did not affect the percentage of dead bacteria in NaOCl, CHX, and Irritrol (p > 0.05). No irrigation protocol tested was able to eliminate the E. faecalis biofilm. While the application of trypsin as a pre-enzyme improved the antimicrobial effect of AgCNPs, it did not make any difference over other irrigation solutions.

Assessment of Antimicrobial Activity of Nanocomposites Based on Nano-Hydroxyapatite (HAP), Chitosan, and Vitamin K2

OBJECTIVE

The objective of this study was to evaluate the antimicrobial potential of nanocomposites containing vitamin K2, hydroxyapatite nanoparticles (nHAP), and chitosan (Chito)-coated dental implants against clinically relevant microbial strains.

MATERIALS AND METHODS

Four test compounds were prepared: vitamin K2 + nHAP, K2 + Chito + nHAP, vitamin K2, and vitamin K2 + Chito. Agar well diffusion test was conducted to assess the antimicrobial activity of these compounds against Staphylococcus aureus (S. aureus), Streptococcus mutans (S. mutans), Enterococcus faecalis (E. faecalis), and Candida albicans (C. albicans). Results: The vitamin K2 + nHAP nanocomposite exhibited antimicrobial activity against all tested microorganisms, with E. faecalis showing the highest sensitivity (25 mm zone of inhibition at 100 µL concentration). The K2 + Chito + nHAP nanocomposite demonstrated potent antimicrobial activity with C. albicans displaying the highest sensitivity (28 mm zone of inhibition at 100 µL concentration). Pure vitamin K2 showed limited antimicrobial activity, vitamin K2 combined with chitosan exhibited significant susceptibility to C. albicans, resulting in a substantial inhibition zone of 24 mm diameter at a concentration of 100 µL.

CONCLUSION

The synergistic effects of vitamin K2 with nHAP and chitosan highlight the potential of these nanocomposites for biomedical applications. These findings contribute to the development of effective nanocomposites to address antimicrobial resistance and improve infection control in various biomedical fields.

The Efficacy of Apple Cider Vinegar at Different pH Values as an Antimicrobial Agent: An In Vitro Study

AIMS AND BACKGROUND

This study evaluates the antimicrobial activities of commercially available 5% apple cider vinegar (ACV) against Enterococcus faecalis, Streptococcus mutans, and Lactobacillus casei. Materials and methods: Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were conducted using the broth microdilution method. Sodium hypochlorite (NaOCl) of 5.25% was used as a positive control, and comparisons were also made with acetic acid (AA) as the main ingredient in ACV. The three test bacteria treated with the most effective ACV dilution were visualized under a transmission electron microscope (TEM) for structural changes.

RESULTS

Minimal inhibitory concentration was determined at 0.625% of the concentration of ACV against S. mutans and E. faecalis and 1.25% of the concentration of ACV against L. casei with two-fold serial dilutions. A concentration of 5 × 10-1% with 10-fold serial dilutions was found to be the MIC value for all three bacteria. No significant differences were found when compared with the positive control (NaOCl) (p = 0.182, p = 0.171, and p = 0.234), respectively, for two-fold serial dilutions and (p = 1.000, p = 0.658, and p = 0.110), respectively for 10-fold serial dilutions. MBC was observed to be 5% ACV for both E. faecalis and S. mutans. However, positive microbial growth was observed on the agar plate when cultured with L. casei. An independent sample t-test showed no significant differences (p > 0.05) in the antimicrobial activities between 5% ACV and 5% pure AA. TEM revealed cell wall and cytoplasmic membrane disruptions on all three bacteria at MIC value.

CONCLUSION

Apple cider vinegar has antimicrobial activities against Enterococcus faecalis, Streptococcus mutans, and Lactobacillus casei at their respective MIC values.

CLINICAL SIGNIFICANCE

Apple cider vinegar can be an alternative antimicrobial dental pulp disinfectant to sodium hypochlorite. Apple cider vinegar can be used safely, especially in children's dental pulp therapy and deep caries management, when adequate tooth isolation is not readily achievable. Thus, adverse reactions commonly associated with other frequently used chemical disinfectants can be avoided.

Nanofibers in Respiratory Masks: An Alternative to Prevent Pathogen Transmission

Recent global outbreak of COVID-19 has raised serious awareness about our abilities to protect ourselves from hazardous pathogens and volatile organic compounds. Evidence suggests that personal protection equipment such as respiratory masks can radically decrease rates of transmission and infections due to contagious pathogens. To increase filtration efficiency without compromising breathability, application of nanofibers in production of respiratory masks have been proposed. The emergence of nanofibers in the industry has since introduced a next generation of respiratory masks that promises improved filtration efficiency and breathability via nanometric pores and thin fiber thickness. In addition, the surface of nanofibers can be functionalized and enhanced to capture specific particles. In addition to conventional techniques such as melt-blown, respiratory masks by nanofibers have provided an opportunity to prevent pathogen transmission. As the surge in global demand for respiratory masks increases, herein, we reviewed recent advancement of nanofibers as an alternative technique to be used in respiratory mask production.

Antibiofilm activity of ultrasonic and diode laser activated sodium hypochlorite, chitosan, and chlorhexidine: A confocal laser scanning microscopic in vitro study

Aim

The aim of this study was to assess and compare the effect of ultrasonic and diode laser-activated sodium hypochlorite (NaOCl), chitosan, and chlorhexidine (CHX) on the removal of Enterococcus faecalis biofilm adherent to the root canal using a confocal laser scanning microscope (CLSM).

Materials and Methods

Root canals in 112 single-rooted teeth were instrumented using a rotary Ni-Ti system. Biofilms of E. faecalis were generated based on an established protocol. Samples were randomly divided into three experimental (n = 28) and one control (n = 28) group based on the irrigation protocol employed and the three experimental groups were further subdivided into subgroups based on the activation protocol (subgroup A - ultrasonic activated and subgroup B - diode laser activated). The groups were Group 1 (control), Group 2 (3% NaOCl for 6 min; subgroup A - activated using a diode laser, subgroup B - ultrasonic activation), Group 3 (2% CHX for 6 min; subgroup A - activated using a diode laser, subgroup B - ultrasonic activation), and Group 4 (0.2% chitosan for 6 min; subgroup A - activated using a diode laser, subgroup B - ultrasonic activation. Confocal laser scanning microscopy was used to assess bacterial viability in situ. Data were analyzed by appropriate statistical analyses with P = 0.05.

Results

All experimental irrigation protocols destroyed the biofilm in the root canal lumen. Within the dentinal tubules, all groups had a significantly higher percentage of dead bacteria than the saline control (P < 0.05). There was no significant difference between CHX activated with ultrasonics, CHX activated with a diode laser, chitosan activated with ultrasonics and chitosan activated with diode laser groups (P > 0.05), whereas NaOCl ultra and NaOCl diode groups brought about more bacterial reduction than other groups (P < 0.05). The mean effectiveness and the bacterial kill ability were seen highest for the NaOCl activated with the ultrasonics group. There was no significant difference between diode laser activation and ultrasonic activation in CHX activated with ultrasonics, CHX activated with a diode laser, chitosan activated with ultrasonics and chitosan activated with diode laser groups (P > 0.05), but there was a significant difference between diode laser and ultrasonic activation in NaOCl group. Ultrasonic activation of the NaOCl was more effective than diode activation in reducing E. feacalis biofilms (P < 0.05).

Conclusions

The use of NaOCl with the activation by ultrasonics caused the greatest reduction of E. faecalis. Ultrasonic activation was found superior to diode laser activation in dentinal tubule disinfection.

The effect of biocompatible carriers with vitamin D and platelet-rich plasma (PRP) on bone defects

Introduction

In oral and maxillofacial surgery, hard tissue augmentation is provided by materials that accelerate the healing, act as a template for reconstructing bony defects, and stimulate bone production and growth. This study investigated the effects of biocompatible carriers containing active vitamin D and platelet-rich plasma (PRP) on bone defects created in rat calvaria.

Material and Methods

This experimental animal study utilized fifty-two male Sprague Dawley rats divided into six groups and conducted histopathological, microtomographic, and biochemical comparisons by adding vitamin D, which has an accelerating effect on bone development. We examined the calvarial defects, sacrificing the rats in equal numbers (eight in each group and four to obtain PRP) at the first, second, fourth, and eighth weeks. The newly formed bone was assessed using histopathologic, microtomographic, and macroscopic methods as well as the biochemical analysis performed in the plasma samples. Expression of fibroblast growth factor 23 (FGF23), vitamin D receptor (VDR), and receptor activator of nuclear factor-kappa B (RANK), which determine bone formation, were investigated. The amounts of ossification, bone volume, and mineral densities were significantly higher in the fourth and eighth weeks as the biocompatible material was delivered with calcitriol.

Results

The histological and macroscopic examinations revealed that the defect area shrank and was colonized with new cells in the "calcitriol + chitosan + PRP" group. The expression of RANK, FGF23, and VDR antibodies was more intense in the "calcitriol + chitosan + PRP" group than in other groups of the experiment and controls.

Conclusion

Active vitamin D, PRP, and chitosan formulation positively contributed to the repair of bone defects and induced remarkable clinical improvement. This new delivery approach could be promising for healing bone defects following surgical operations in hard bony tissues. HIPPOKRATIA 2023, 27 (2):48-56.

Efficacy of chitosan paste as intracanal medication against Enterococcus faecalis and Candida albicans biofilm compared with calcium hydroxide in an in vitro root canal infection model

Background

Enterococcus faecalis and Candida albicans are frequently found in persistent endodontic infection and could remain in dentinal tubules despite intracanal medication with calcium hydroxide (Ca(OH)₂), a commonly used medication. Thus, an effective and safe antimicrobial medication against such refractory infection is necessary in endodontic retreatment, so we aimed to test the efficacy of chitosan paste against these microorganisms compared with Ca(OH)₂ in root canals of extracted human teeth.

Methods

Thirty-six sterilized human root samples prepared from extracted premolars and upper maxillary incisors were infected with E. faecalis for 14 days, while 32 were infected with C. albicans for 48 h, for mature biofilm formation. The samples were assigned to 6 groups of intracanal medications: Group 1: no medication (negative control); Group 2: 20% Polyethylene glycol (PEG); Group 3: 20% Propylene glycol (PG); Group 4: Ca(OH)₂; Group 5: Chitosan + PEG; and Group 6: Chitosan + PG. After 7 days, intracanal surface dentin was harvested using Protaper next, resuspended, serially diluted and spread on Brain–Heart-Infusion agar (for E. faecalis) and Yeast Extract-Peptone-Dextrose agar (for C. albicans) for colony count. Antimicrobial efficacy was determined as percentage of remaining colony forming unit (CFUs) relative to negative control and analyzed using One-way ANOVA and post-hoc Games-Howell test. The significance level was set at 0.05.

Results

For E. faecalis, chitosan + PG had significantly higher antibacterial activity than Ca(OH)₂ (P = 0.039). Chitosan + PEG and chitosan + PG medication significantly reduced viable bacteria compared with negative control, PEG and PG (P = 0.001, 0.003, 0.024, respectively for chitosan + PEG; P = 0.002, 0.003, 0.014, respectively for chitosan + PG). For C.albicans, chitosan + PEG and chitosan + PG were not significantly different from Ca(OH)₂. However, Chitosan + PEG and chitosan + PG, but not Ca(OH)₂, showed a significantly lower level of remaining CFUs compared with negative control (P = 0.013 and 0.005, respectively).

Conclusion

Chitosan paste showed better efficacy in reducing viable E. faecalis biofilm when compared to Ca(OH)₂ after 7-day intracanal medication in this in vitro root canal model. It could also significantly reduce viable C. albicans, but was not significantly different from Ca(OH)₂.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02385-x.

Fucoidan-derived carbon dots against Enterococcus faecalis biofilm and infected dentinal tubules for the treatment of persistent endodontic infections

Enterococcus faecalis (E. faecalis) biofilm-associated persistent endodontic infections (PEIs) are one of the most common tooth lesions, causing chronic periapical periodontitis, root resorption, and even tooth loss. Clinical root canal disinfectants have the risk of damaging soft tissues (e.g., mucosa and tongue) and teeth in the oral cavity, unsatisfactory to the therapy of PEIs. Nanomaterials with remarkable antibacterial properties and good biocompatibility have been developed as a promising strategy for removing pathogenic bacteria and related biofilm. Herein, carbon dots (CDs) derived from fucoidan (FD) are prepared through a one-pot hydrothermal method for the treatment of PEIs. The prepared FDCDs (7.15 nm) with sulfate groups and fluorescence property are well dispersed and stable in water. Further, it is found that in vitro FDCDs display excellent inhibiting effects on E. faecalis and its biofilm by inducing the formation of intracellular and extracellular reactive oxygen species and altering bacterial permeability. Importantly, the FDCDs penetrated the root canals and dentinal tubules, removing located E. faecalis biofilm. Moreover, the cellular assays show that the developed FDCDs have satisfactory cytocompatibility and promote macrophage recruitment. Thus, the developed FDCDs hold great potential for the management of PEIs.

Molecular docking reveals Chitosan nanoparticle protection mechanism for dentin against Collagen-binding bacteria

The medical application of chitosan (Cs) has been for about half a century, but the molecular mechanism has not been elucidated yet. This study is to explore the antibacterial mechanism of chitosan nanoparticles (Csnp) in dentin at the atomic resolution level. Extracted tooth specimen was prepared in three groups: A. control group; B. Csnp treatment under ultrasonic agitation (UA); C. Csnp treatment without UA. A scanning electron microscope (SEM) was used to observe the Csnp distribution on the dentin surface. The incubations of Enterococcus faecalis (E. faecalis) were performed. Further, we explored the protection mechanism of chitosan polymers to collagen type I, using molecular docking technique and crystal structure superimposition analysis. We revealed that Csnp under UA was evenly distributed on the dental surface and the Csnp-pretreated dentin had great antibacterial activity for E. faecalis. Our work demonstrated that Csnp occupied the grooves of the triple-helical collagen surface, strengthened by crosslinking, and interfered with the bond of collagen adhesin through steric hindrance effect and interrupting hydrophobic interaction. Csnp protects dentin against E. faecalis by interacting and crosslinking with collagen type I and prevents bacterial collagen adhesin binding through steric hindrance effect and interrupting hydrophobic interaction. Graphical abstract.

Nanomaterials Application in Endodontics

In recent years, nanomaterials have become increasingly present in medicine, especially in dentistry. Their characteristics are proving to be very useful in clinical cases. Due to the intense research in the field of biomaterials and nanotechnology, the efficacy and possibilities of dental procedures have immensely expanded over the years. The nano size of materials allows them to exhibit properties not present in their larger-in-scale counterparts. The medical procedures in endodontics are time-consuming and mostly require several visits to be able to achieve the proper result. In this field of dentistry, there are still major issues about the removal of the mostly bacterial infection from the dental root canals. It has been confirmed that nanoparticles are much more efficient than traditional materials and appear to have superior properties when it comes to surface chemistry and bonding. Their unique antibacterial properties are also promising features in every medical procedure, especially in endodontics. High versatility of use of nanomaterials makes them a powerful tool in dental clinics, in a plethora of endodontic procedures, including pulp regeneration, drug delivery, root repair, disinfection, obturation and canal filling. This study focuses on summing up the current knowledge about the utility of nanomaterials in endodontics, their characteristics, advantages, disadvantages, and provides a number of reasons why research in this field should be continued.

Biomedical Applications of Quaternized Chitosan

The natural polymer chitosan is the second most abundant biopolymer on earth after chitin and has been extensively explored for preparation of versatile drug delivery systems. The presence of two distinct reactive functional groups (an amino group at C2, and a primary and secondary hydroxyl group at C3 and C6) of chitosan are involved in the transformation of expedient derivatives such as acylated, alkylated, carboxylated, quaternized and esterified chitosan. Amongst these, quaternized chitosan is preferred in pharmaceutical industries owing to its prominent features including superior water solubility, augmented antimicrobial actions, modified wound healing, pH-sensitive targeting, biocompatibility, and biodegradability. It has been explored in a large realm of pharmaceuticals, cosmeceuticals, and the biomedical arena. Immense classy drug delivery systems containing quaternized chitosan have been intended for tissue engineering, wound healing, gene, and vaccine delivery. This review article outlines synthetic techniques, basic characteristics, inherent properties, biomedical applications, and ubiquitous challenges associated to quaternized chitosan.

Dual Antibacterial Activities and Biofilm Eradication of a Marine Peptide-N6NH2 and Its Analogs against Multidrug-Resistant Aeromonas veronii

Aeromonas veronii is one of the main pathogens causing various diseases in humans and animals. It is currently difficult to eradicate drug-resistant A. veronii due to the biofilm formation by conventional antibiotic treatments. In this study, a marine peptide-N6NH2 and its analogs were generated by introducing Orn or replacing with D-amino acids, Val and Pro; their enzymic stability and antibacterial/antibiofilm ability against multi-drug resistant (MDR) A. veronii ACCC61732 were detected in vitro and in vivo, respectively. The results showed that DN6NH2 more rapidly killed A. veronii ACCC61732 and had higher stability in trypsin, simulated gastric/intestinal fluid, proteinase K, and mouse serum than the parent peptide-N6NH2. DN6NH2 and other analogs significantly improved the ability of N6NH2 to penetrate the outer membrane of A. veronii ACCC61732. DN6NH2, N6PNH2 and V112N6NH2 protected mice from catheter-associated biofilm infection with MDR A. veronii ACCC61732, superior to N6NH2 and CIP. DN6NH2 had more potent efficacy at a dose of 5 μmol/kg (100% survival) in a mouse peritonitis model than other analogs (50-66.67%) and CIP (83.33%), and it inhibited the bacterial translocation, downregulated pro-inflammatory cytokines, upregulated the anti-inflammatory cytokine, and ameliorated multiple-organ injuries (including the liver, spleen, lung, and kidney). These data suggest that the analogs of N6NH2 may be a candidate for novel antimicrobial and antibiofilm agents against MDR A. veronii infections.