Antibacterial and antibiofilm efficacy of k21-E in root canal disinfection

Unravelling the Programmed Inflammation and Tissue Repair by a Multipotential Antimicrobial K21 Silane

AIMS AND OBJECTIVES

To examine if a novel antimicrobial silane K21 can alter macrophage polarisation and affect fibroblast proliferation by deciphering the molecular pathways for programmed healing using a combined in vitro and in vivo (animal) burn model.

MATERIALS AND METHODS

An injectable silane-based antimicrobial aimed to modulate macrophage polarisation was manufactured. Experimental analysis included colorimetric cell migration assays on gingival fibroblasts, macrophage phagocytosis characterisation, immunofluorescence staining, triacylglycerol accumulation within macrophages by LCMS, cellular metabolic/proliferation assays, macrophage exposure quantification with morphology assessment using FE-SEM, Raman spectral analysis, RNA isolation for relative gene expression and animal study model to morphometrically and microscopically analyse partial thickness burn wound healing under QAS/K21.

RESULTS

M1 and M2 polarisation both appeared exaggerated under QAS/K21 treatment. The wounds treated with K21 had depicted accelerated healing as compared to control (P < .05) in dorsal skin of rabbits. Relative gene expression results demonstrate reduced cytokine and anti-inflammatory response under the influence of K21. While M1 expression, TG accumulation, and associated characterisations demonstrate the programmed inflammatory potential of K21.

CONCLUSION

the antimicrobial and reparative efficacy of K21 silane aids in programmed inflammation for enhanced tissue healing and repair.

Mechano-triggered eradication of dentinal tubule biofilm via in situ generation of nanoscale sonosensitizer by the tailored irrigation formulation

The efficient elimination of bacteria within the dentinal tubules has been hindered by the poor deposition and short residence of disinfecting agents. Meanwhile, the current irrigant (e.g., NaClO, 5.25 %) shows severe adverse effects on the surrounding soft tissues because of its inherent high irritancy. To address this issue, this work reports an in situ generated sonosensitizer to handle the biofilm in dentinal tubules with minimal adverse effects. The production of nanoscale sonosensitizer involves the concurrent delivery of H2O2 (0.01 %), ferrocene derivative (Fc), and indocyanine green (ICG). With ultrasound treatment, the reaction between H2O2 and Fc liberated Fe3+ that was further complexed with ICG to generate the nanoscale sonosensitizer in situ, followed by singlet oxygen production for potent disinfecting action. Because the above cascade reactions occur within the confined dentinal tubules, the generated ICG-Fe3+ nanosensitizer would show prolonged retention therein. The anti-bacterial potency of nanosensitizer was demonstrated in petrodish and ex vivo biofilm models. Meanwhile, the transmission electron microscope imaging of biofilm and cytotoxicity assay in L929 fibroblast cells proved the superiority of nanosensitizer against NaClO regarding adverse effects. The current work opens new avenues of biofilm elimination in dentinal tubules, showing a high translation potential.

A Novel pH-Responsive Nano-Sized Lanthanum-Doped Polyvinyl Alcohol-Carbon Quantum Dot Composite for Root Canal Irrigation

Purpose

The primary goals of endodontic therapy are to eliminate microbes and prevent reinfection. Persistent root canal infections and failure of root canal therapy are primarily attributed to the presence of bacteria, particularly E. faecalis. Chemical irrigants play a crucial role in complementing mechanical instrumentation in ensuring adequate disinfection. However, current techniques and available irrigants are limited in their ability to achieve optimal sterilization of the root canal system. In this study, we developed a novel material called La@PCDs by combining CQD-PVA and lanthanum for root canal irrigation.

Methods

A one-pot hydrothermal method was used to prepare composites of lanthanum and CQD-PVA (La@PCDs). Scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy and the particle size were employed to characterize La@PCDs. ROS generation was evaluated by measuring the fluorescence intensity emitted at 525 nm from 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA). In vitro experiments were conducted to assess the effectiveness of the nanoparticles in combating Enterococcus faecalis and eradicating in situ biofilm eradication in root canal. Furthermore, cytotoxicity assessments were carried out to demonstrate the safety of La@PCDs.

Results

SEM and FTIR results showed that La@PCDs were successfully prepared and exhibiting a homogeneous size distribution and irregular morphology. ROS assessment demonstrated that La@PCDs have a synergistic effect, promoting the production of a large number of ROS. This effect only occurred under acidic PH conditions. The inherent acidity in the biofilm microenvironment can act as internal stimulus. In vitro experiments revealed superior antibacterial efficiency under acidic conditions without causing significant cytotoxicity compared to the commonly used NaClO irrigant. The biosafety of La@PCDs was confirmed.

Conclusion

Compared to existing materials, these nanoparticles exhibit favorable antibacterial and anti-biofilm properties, along with improved biocompatibility. These findings emphasize the potential of the integrated La@PCDs as a promising option for enhancing root canal irrigation and disinfection.

Antibacterial efficacy of silver nanoparticles, sodium hypochlorite, chlorhexidine, and hypochlorous acid on dentinal surfaces infected with Enterococcus faecalis

The purpose of this study was to evaluate the antibacterial effect of silver nanoparticles (AgNPs) against Enterococcus faecalis and compare it with different irrigation solutions. This study was performed using 64 dentin blocks. E. faecalis suspension was dispensed to each sample and incubated under anaerobic conditions at 37°C throughout 21 days. After the inoculation period, the following solutions were added to each group and kept for 5 min: Group 1, 5.25% sodium hypochlorite (NaOCl); Group 2, 2.5% NaOCl; Group 3, 1% NaOCl; Group 4, 2% chlorhexidine (CHX); Group 5, 200 ppm hypochlorous acid (HOCl); and Group 6, AgNPs. The samples of positive control were treated with sterile saline. Biofilm viability assay was performed using the LIVE/DEAD BacLight Bacterial Viability Kit. Samples were examined using confocal laser scanning microscopy, respectively. There was no significant difference between the 5.25% NaOCl, 2.5% NaOCl, and 1%NaOCl groups (p > .05). However, these groups showed statistically higher antibacterial activity than the 2% CHX, 200 ppm HOCl, and AgNP groups. Also, 2% CHX showed greater percentage of dead cells compared with the AgNP and HOCl groups. While AgNPs group showed lower dead cell rate than all NaOCl groups and 2% CHX, it caused higher dead cells than 200 ppm HOCl group. The 200 ppm HOCl group showed the lowest percentage of dead cells (p < .05) Although the antibacterial effect of AgNPs is not as high as NaOCl and CHX, it has considerable bactericidal activity against E. faecalis and can be improved by further studies. RESEARCH HIGHLIGHTS: New antimicrobial approaches for root canal irrigation. Antimicrobial effect of silver nanoparticles against E. faecalis. Elimination of the biofilm layer for the success of endodontic treatment.

Next generation antibacterial strategies for regenerative endodontic procedures: A scoping review

BACKGROUND

The clinical results following regenerative endodontic procedures (REPs) vary according to numerous parameters, including the presence of bacteria. This limitation reduces the indications for REPs and calls for the development of next generation antibacterial strategies (NGAS) providing alternatives to current antibacterial strategies (CAS) such as double or triple antibiotic paste (DAP/TAP) and (Ca(OH)2).

OBJECTIVES

The present scoping review aims to describe the current trends regarding the use of such strategies and highlight future perspectives.

METHODS

Four databases (PUBMed, Cochrane, ClinicalTrials and Science Direct) were searched until 1st May 2023.

RESULTS

A total of 918 records were identified, 133 were screened and assessed for eligibility, and 87 articles were included. The findings show that (1) clinical studies are only available for CAS, (2) although next generation strategies are the most studied approach since 2017, they are all at the pre-clinical stage, (3) most of the next generation strategies use galenic forms which offer cell support and colonization and which simultaneously contain antibacterial molecules as alternatives to CAS and to antibiotics in general, (4) standardization is required for future research, specifically regarding the bacterial strains studied, the use of biofilm studies and the cellular behaviour assessments.

CONCLUSION

Although NGAS are promising strategies to improve REPs in the context of infection, the current evidence is mostly limited to pre-clinical studies. Further methodological improvement is required to allow relevant comparisons between studies and to reduce the time from bench to bedside.

Nanoarchitectonics-Based Materials as a Promising Strategy in the Treatment of Endodontic Infections

Endodontic infections arise from the interactive activities of microbial communities colonizing in the intricate root canal system. The present study aims to update the latest knowledge of nanomaterials, their antimicrobial mechanisms, and their applications in endodontics. A detailed literature review of the current knowledge of nanomaterials used in endodontic applications was performed using the PubMed database. Antimicrobial nanomaterials with a small size, large specific surface area, and high chemical activity are introduced to act as irrigants, photosensitizer delivery systems, and medicaments, or to modify sealers. The application of nanomaterials in the endodontic field could enhance antimicrobial efficiency, increase dentin tubule penetration, and improve treatment outcomes. This study supports the potential of nanomaterials as a promising strategy in treating endodontic infections.

Newly discovered clouting interplay between matrix metalloproteinases structures and novel quaternary Ammonium K21: computational and in-vivo testing

AIMS AND OBJECTIVES

To analyze anti-MMP mode of action of Quaternary Ammonium Silane (QAS, codenamed as k21) by binding onto specific MMP site using computational molecular simulation and Anti-Sortase A (SrtA) mode of action by binding onto specific site using computational molecular simulation.

MATERIALS AND METHODS

In silico Molecular Dynamics (MD) was used to determine the interactions of K21 inside the pocket of the targeted protein (crystal structure of fibroblast collagenase-1 complexed to a diphenyl-ether sulphone based hydroxamic acid; PDB ID: 966C; Crystal structure of MMP-2 active site mutant in complex with APP-derived decapeptide inhibitor. MD simulations were accomplished with the Desmond package in Schrödinger Drug Discovery Suite. Blood samples (~ 0.5 mL) collected into K2EDTA were immediately transferred for further processing using the Litron MicroFlow® PLUS micronucleus analysis kit for mouse blood according to the manufacturer's instructions. Bacterial Reverse Mutation Test of K21 Molecule was performed to evaluate K21 and any possible metabolites for their potential to induce point mutations in amino acid-requiring strains of Escherichia coli (E. coli) (WP2 uvrA (tryptophan-deficient)).

RESULTS

Molecular Simulation depicted that K21 has a specific pocket binding on various MMPs and SrtA surfaces producing a classical clouting effect. K21 did not induce micronuclei, which are the result of chromosomal damage or damage to the mitotic apparatus, in the peripheral blood reticulocytes of male and female CD-1 mice when administered by oral gavage up to the maximum recommended dose of 2000 mg/kg. The test item, K21, was not mutagenic to Salmonella typhimurium (S. typhimurium) strains TA98, TA100, TA1535 and TA1537 and E. coli strain WP2 uvrA in the absence and presence of metabolic activation when tested up to the limit of cytotoxicity or solubility under the conditions of the test.

CONCLUSION

K21 could serve as a potent protease inhibitor maintaining the physical and biochemical properties of dental structures.

Shifting from Ammonium to Phosphonium Salts: A Promising Strategy to Develop Next-Generation Weapons against Biofilms

Since they are difficult and sometimes impossible to treat, infections sustained by multidrug-resistant (MDR) pathogens, emerging especially in nosocomial environments, are an increasing global public health concern, translating into high mortality and healthcare costs. In addition to having acquired intrinsic abilities to resist available antibiotic treatments, MDR bacteria can transmit genetic material encoding for resistance to non-mutated bacteria, thus strongly decreasing the number of available effective antibiotics. Moreover, several pathogens develop resistance by forming biofilms (BFs), a safe and antibiotic-resistant home for microorganisms. BFs are made of well-organized bacterial communities, encased and protected in a self-produced extracellular polymeric matrix, which impedes antibiotics' ability to reach bacteria, thus causing them to lose efficacy. By adhering to living or abiotic surfaces in healthcare settings, especially in intensive care units where immunocompromised older patients with several comorbidities are hospitalized BFs cause the onset of difficult-to-eradicate infections. In this context, recent studies have demonstrated that quaternary ammonium compounds (QACs), acting as membrane disruptors and initially with a low tendency to develop resistance, have demonstrated anti-BF potentialities. However, a paucity of innovation in this space has driven the emergence of QAC resistance. More recently, quaternary phosphonium salts (QPSs), including tri-phenyl alkyl phosphonium derivatives, achievable by easy one-step reactions and well known as intermediates of the Wittig reaction, have shown promising anti-BF effects in vitro. Here, after an overview of pathogen resistance, BFs, and QACs, we have reviewed the QPSs developed and assayed to this end, so far. Finally, the synthetic strategies used to prepare QPSs have also been provided and discussed to spur the synthesis of novel compounds of this class. We think that the extension of the knowledge about these materials by this review could be a successful approach to finding effective weapons for treating chronic infections and device-associated diseases sustained by BF-producing MDR bacteria.

The state of the art and future trends of root canal files from the perspective of patent analysis: a study design

The goal of this review is to present a detailed and comprehensive description of the published work from the past decade regarding methods of improved material, geometric design, and additional functions in root canal files. The main improved methods of files and the most common technologies were further addressed, underlining their advantages and main limitations. Online databases (the Derwent Innovations Index) were consulted on this topic. Published work from 2010 to 2022 was collected and analyzed the relevant papers were chosen for inclusion in this review. The patent map classified the latest phase of the root canal files based on the analysis of the number of patents. The performance of the root canal files, such as materials. Directly affects the quality of the root canal therapy. We provided a thorough review of advances in the field of root canal files. In particular, three categories of improved methods were examined and compared, including material-based methods, geometry-based methods, and those based on additional functions. To understand this state of the art of different improved methods of root canal files, we conducted a literature analysis and a series of comparisons between different methods. The features and limitations of each method of root canal files were further discussed. Finally, we identified promising research directions in advancing the methods for the improved performance of root canal files. There is no perfect technology for all material/geometric design/additional functions, capable alone of fulfilling all the specificity and necessities of every patient. Although it is very promising, the material of the files remains understudied, and further work is required to make material science a pervasive technology in root canal therapy, and contribute to endodontic and periapical diseases by assisting in the subsequent development of root canal files.

Recent Update on Applications of Quaternary Ammonium Silane as an Antibacterial Biomaterial: A Novel Drug Delivery Approach in Dentistry

Quaternary ammonium silane [(QAS), codename – k21] is a novel biomaterial developed by sol-gel process having broad spectrum antimicrobial activities with low cytotoxicity. It has been used in various concentrations with maximum antimicrobial efficacy and biocompatibility. The antimicrobial mechanism is displayed via contact killing, causing conformational changes within the bacterial cell membrane, inhibiting Sortase-A enzyme, and causing cell disturbances due to osmotic changes. The compound can attach to S1' pockets on matrix metalloproteinases (MMPs), leading to massive MMP enzyme inhibition, making it one of the most potent protease inhibitors. Quaternary ammonium silane has been synthesized and used in dentistry to eliminate the biofilm from dental tissues. QAS has been tested for its antibacterial activity as a cavity disinfectant, endodontic irrigant, restorative and root canal medication, and a nanocarrier for drug delivery approaches. The review is first of its kind that aims to discuss applications of QAS as a novel antibacterial biomaterial for dental applications along with discussions on its cytotoxic effects and future prospects in dentistry.

Biochemical changes and macrophage polarization of a silane-based endodontic irrigant in an animal model

Silane-based/fully hydrolyzed, endodontic irrigant exhibiting antimicrobial properties, is prepared, and is hypothesized to control macrophage polarization for tissue repair. Albino wistar rats were injected with 0.1 ml root canal irrigant, and bone marrow cells procured. Cellular mitochondria were stained with MitoTracker green along with Transmission Electron Microscopy (TEM) performed for macrophage extracellular vesicle. Bone marrow stromal cells (BMSCs) were induced for M1 and M2 polarization and Raman spectroscopy with scratch assay performed. Cell counting was used to measure cytotoxicity, and fluorescence microscopy performed for CD163. Scanning Electron Microscopy (SEM) was used to investigate interaction of irrigants with Enterococcus faecalis. K21 specimens exhibited reduction in epithelium thickness and more mitochondrial mass. EVs showed differences between all groups with decrease and increase in IL-6 and IL-10 respectively. 0.5%k21 enhanced wound healing with more fibroblastic growth inside scratch analysis along with increased inflammation-related genes (ICAM-1, CXCL10, CXCL11, VCAM-1, CCL2, and CXCL8; tissue remodelling-related genes, collagen 1, EGFR and TIMP-2 in q-PCR analysis. Sharp bands at 1643 cm^-1 existed in all with variable intensities. 0.5%k21 had a survival rate of BMSCs comparable to control group. Bacteria treated with 0.5%k21/1%k21, displayed damage. Antimicrobial and reparative efficacy of k21 disinfectant is a proof of concept for enhanced killing of bacteria across root dentin acquiring functional type M2 polarization for ethnopharmacological effects.