Cationic Antimicrobial Peptides Are Leading the Way to Combat Oropathogenic Infections

Deciphering the Dilemma of Community Behavior Promotion and Inhibition by Cationic Bactericide-coated Nanoparticles in Gram-Negative Bacteria

Cationic bactericidal-coated gold nanoparticles are known to effectively prevent Gram-negative bacterial initial adhesion and community behavior development by strongly binding to bacterial surfaces and disrupting the cell membranes. However, such nanoparticles have been recently shown to unintentionally promote community behavior in Gram-negative bacteria because of the bacterial stress response. To find whether these contradictory findings are due to emerging stress response or poorly understood nanoparticle interactions of Gram-negative bacteria, in this work, we treated high population curli-producing Gram-negative Escherichia coli with cationic antibiotic/antiseptic-coated gold nanoparticles and followed the consequences in details using a variety of physical methods and controls. Parallelly, we employed standard biological assays commonly used to detect community behavior in bacteria. Biological assays yielded contradictory results some inferring promotion while others inferring inhibition. However, physical methods revealed that promotion and inhibition observations resulted from physical interactions without any bacterial response being involved. Using physical methods, we further demonstrated that macromolecules of cationic antibiotics and antiseptics exhibit similar consequences as nanoparticles, independent of inhibitory concentration. Overall, the results emphasize the need to consider physical interactions, rather than relying solely on standard biological assays, when evaluating the inhibition or promotion of community behavior by cationic antibiotic/antiseptic-coated nanoparticles or free cationic antibiotics/antiseptics against Gram-negative bacteria.

A deformable SIS/HA composite hydrogel coaxial scaffold promotes alveolar bone regeneration after tooth extraction

After tooth extraction, alveolar bone absorbs unevenly, leading to soft tissue collapse, which hinders full regeneration. Bone loss makes it harder to do dental implants and repairs. Inspired by the biological architecture of bone, a deformable SIS/HA (Small intestinal submucosa/Hydroxyapatite) composite hydrogel coaxial scaffold was designed to maintain bone volume in the socket. The SIS/HA scaffold containing GL13K as the outer layer, mimicking compact bone, while SIS hydrogel loaded with bone marrow mesenchymal stem cells-derived exosomes (BMSCs-Exos) was utilized as the inner core of the scaffolds, which are like soft tissue in the skeleton. This coaxial scaffold exhibited a modulus of elasticity of 0.82 MPa, enabling it to adaptively fill extraction sockets and maintain an osteogenic space. Concurrently, the inner layer of this composite scaffold, enriched with BMSCs-Exos, promoted the proliferation and migration of human umbilical vein endothelial cells (HUVECs) and BMSCs into the scaffold interior (≈3-fold to the control), up-regulated the expression of genes related to osteogenesis (BMP2, ALP, RUNX2, and OPN) and angiogenesis (HIF-1α and VEGF). This induced new blood vessels and bone growth within the scaffold, addressing the issue of low bone formation rates at the center of defects. GL13K was released by approximately 40.87 ± 4.37 % within the first three days, exerting a localized antibacterial effect and further promoting vascularization and new bone formation in peripheral regions. This design aims to achieve an all-around and efficient bone restoration effect in the extraction socket using coaxial scaffolds through a dual internal and external mechanism.

Technological dental sealants: in vitro evaluation of material properties and antibiofilm potential

BACKGROUND

Due to the launch of new self-etching and self-adhesive sealing materials combined with the release of bioactive ions in the dental market, this in vitro study aimed to compare physical values of surface roughness (RS), vickers microhardness (VM), compositional energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), microbiological tests (inhibition halo-HI and surface microbial adhesion-MAS) and mechanical microshear bond strength (MBS).

METHODS

The following groups were analyzed: Beautisealant® self-etching sealant (Shofu)(G1), FluroShield® conventional sealant (Dentsply)(G2- Control Group), Flow Constic® self-adhesive/self-etching resin (DMG)(G3) and Beautifil Flow Plus F03® conventional resin (Shofu)(G4). For the physical and compositional tests, specimens were molded and submitted to finishing/polishing in a metallographic polisher. RS and VM were measured through 5 readings. For the HI test, specimens were exposed to S. mutans for 24 h in brain-heart infusion (BHI) agar under microaerophilic conditions, with the diameter of the HI (mm) measured by digital caliper. For the MAS test, a bacterial biofilm of S. mutans was induced for five days in BHI broth + 5% sucrose and measurement of CFU/ml (log10 from serial dilutions). For the MBS test, specimens were made in bovine enamel with the addition of the experimental group FluroShield® (Dentsply) + Single Bond Universal® adhesive (3 M)(G5) and measured in a universal testing machine. Data were submitted to ANOVA and Tukey's post hoc tests (p < 0.05) using the SPSS software.

RESULTS

Different compositions proven in the EDS test were not determinants of the promotion of different RS: G1 = 0,19 (± 0,07), G2 = 0,15 (± 0,053), G3 = 0,13 (± 0,046), G4 = 0,14 (± 0,056); HI: G1 = 17,7 (± 1,36), G2 = 18,7 (± 3,47), G3 = 18,9 (± 4,87), G4 = 17,9 (± 3,61) and MAS: G1 = 5,22 (± 0,12), G2 = 5,15 (± 0,15), G3 = 5,12 (± 0,20), G4 = 5,06 (± 0,24). However, statistically influenced the values of VM: G1 = 16,71 (± 1,93), G2 = 16,28 (± 4,91), G3 = 26,11 (± 3,46), G4 = 37.9 (± 4.87), promoted lesser bacterial adhesion (G4 = 5.06 ± 0.24), and demonstrated fluoride ion only in the G4. Higher MBS was found in the conventional materials G5 = 8.38 (± 2.05) and G2 = 6.28 (± 1.35).

CONCLUSIONS

Bioactive materials and self-adhesive/self-etching for sealing pits and fissures did not demonstrate superior mechanical and antimicrobial properties performance compared to conventional techniques.

Antifungal susceptibility profile of Candida species and uncommon yeasts from drug abusers with oral candidiasis

In Iran, there is limited information regarding the species distribution and antifungal susceptibility profiles of yeast isolates from drug addicts suffering from oral candidiasis (OC). In this study, 104 yeast isolates, including 98 Candida species and 6 uncommon yeasts, were collected from 71 drug abusers with OC. The susceptibility profiles of Candida spp. and uncommon yeasts to amphotericin B (AMB), itraconazole (ITC), nystatin (NYC), fluconazole (FLC), and caspofungin (CAS) were evaluated using the CLSI broth microdilution method. The prevalence of OC in the sampled population was found to be 29%. The susceptibility profile of Candida spp. revealed remarkable sensitivity, with 100% and 99% of isolates susceptible to NYC and AMB, respectively. However, concerning levels of resistance or non-wild-type minimum inhibitory concentrations (MICs) were observed, with 13.2% of Candida isolates showing resistance to FLC, 13.2% to ITC, and 16.3% to CAS. Notably, 35.2% of patients showed mixed yeast species, while 5.1% of Candida isolates exhibited multidrug resistance. The analysis of the uncommon yeast species showed that the overall frequencies of the highest MICs were observed for CAS. Furthermore, within the six non-Candida species identified, Hanseniaspora opuntiae and one isolate of Pichia kluyveri exhibited resistance to FLC and ITC, respectively, while all non-Candida species were susceptible to AMB and NYC. Additionally, one isolate of Pichia kluyveri exhibited simultaneously high MICs to two drugs ITC and CAS. Furthermore, the Hanseniaspora opuntiae isolate showed high MICs to CAS and FLC. The findings from the present study suggest that AMB and NYC can be suitable choices for empiric treatment of both common Candida species and uncommon yeast infections in substance abuse patients.

The antimicrobial peptide Microcin C7 inhibits the growth of Porphyromonas gingivalis and improves the perodontal status in a rat model

AIMS

This study aimed to investigate the antibacterial and anti-inflammatory effects of the antimicrobial peptide Microcin C7 for Porphyromonas gingivalis-associated diseases.

METHODS AND RESULTS

Reverse-phase high-performance liquid chromatography revealed that Microcin C7 could remain 25.5% at 12 h in saliva. At a concentration of <10 mg ml-1, Microcin C7 showed better cytocompatibility, as revealed by a hemolysis test and a subchronic systemic toxicity test. Moreover, the minimum inhibitory concentration and minimum bactericidal concentration of Microcin C7 were analyzed using a broth microdilution method, bacterial growth curve, scanning electron microscopy, and confocal laser microscopy and determined to be 0.16 and 5 mg ml-1, respectively. Finally, in a rat model, 5 mg ml-1 Microcin C7 showed better performance in decreasing the expression of inflammatory factors (IL-1β, IL-6, IL-8, and TNF-α) and alveolar bone resorption than other concentrations.

CONCLUSIONS

Microcin C7 demonstrated favorable biocompatibility, antibacterial activity, and anti-inflammatory effect, and could decrease the alveolar bone resorption in a rat model, indicating the promising potential for clinical translation and application on P. gingivalis-associated diseases.

The effect of antimicrobial peptide-added adhesive resins on shear bond strength and the adhesive remnant index of orthodontic brackets

OBJECTIVES

The aim of this study was to evaluate the effect of in-vivo produced Nisin which is an antimicrobial peptide (AMP) added to adhesive resin on shear bond strength (SBS) and the adhesive remnant index (ARI) of orthodontic brackets.

METHODS

Bacterial AMP was produced by fermentation and the ideal AMP/Bond concentration and antimicrobial efficacy of the mixture were tested. To evaluate the SBS and ARI scores of AMP-added adhesive resins, 80 maxillary premolar teeth extracted for orthodontic purposes were used and randomly assigned into 2 groups (n = 40). Group 1: Control Group (teeth bonded with standard adhesive resin); Group 2: Experimental Group (teeth bonded with AMP-added adhesive resin). Statistical analysis was performed using the SPSS package program and applying the Mann-Whitney U and Fisher's exact tests. P < 0.05 was considered as statistically significant.

RESULTS

Nisin synthesized in-vivo from Lactococcus lactis (L. lactis) (ATCC 7962) bacteria was provided to form a homogenous solution at an ideal concentration To find the minimum AMP/Bond mixture ratio that showed maximum antimicrobial activity, AMP and Bond mixtures were tested at various concentration levels between 1/160 and 1/2 (AMP/Bond). As a result, the optimum ratio was determined as 1/40. The antimicrobial efficacy of Nisin-added adhesive resin was tested against Streptococcus mutans (S. mutans) (ATCC 35,688) and Lactobacillus strains (cariogenic microorganisms). AMP formed a 2.7 cm diameter zone alone, while 1/40 AMP-bond mixture formed a 1.2 cm diameter zone. SBS values of the teeth bonded with Nisin added adhesive (17.49 ± 5.31) were significantly higher than the control group (14.54 ± 4.96) (P = 0.004). According to the four point scale, Nisin added adhesive provided a higher ARI score in favour of the adhesive and tooth compared to the control group (ARI = 3, n = 20).

CONCLUSIONS

Nisin produced from L. lactis (ATCC 7962) had greater antimicrobial effects after mixing with adhesive bond against cariogenic microorganisms S. mutans (ATCC 35,688) and Lactobacillus strains. Nisin added adhesive increased shear bond strength (SBS) of orthodontic brackets and ARI scores in favor of adhesive & teeth.

CLINICAL RELEVANCE

Clinicians should take into account that using Nisin-added adhesive resin in orthodontic treatments can provide prophylaxis against tooth decay, especially in patients with poor oral hygiene.

Application of biofilm dispersion-based nanoparticles in cutting off reinfection

Bacterial biofilms commonly cause chronic and persistent infections in humans. Bacterial biofilms consist of an inner layer of bacteria and an autocrine extracellular polymeric substance (EPS). Biofilm dispersants (abbreviated as dispersants) have proven effective in removing the bacterial physical protection barrier EPS. Dispersants are generally weak or have no bactericidal effect. Bacteria dispersed from within biofilms (abbreviated as dispersed bacteria) may be more invasive, adhesive, and motile than planktonic bacteria, characteristics that increase the probability that dispersed bacteria will recolonize and cause reinfection. The dispersants should be combined with antimicrobials to avoid the risk of severe reinfection. Dispersant-based nanoparticles have the advantage of specific release and intense penetration, providing the prerequisite for further antibacterial agent efficacy and achieving the eradication of biofilms. Dispersant-based nanoparticles delivered antimicrobial agents for the treatment of diseases associated with bacterial biofilm infections are expected to be an effective measure to prevent reinfection caused by dispersed bacteria. KEY POINTS: • Dispersed bacteria harm and the dispersant's dispersion mechanisms are discussed. • The advantages of dispersant-based nanoparticles in bacteria biofilms are discussed. • Dispersant-based nanoparticles for cutting off reinfection in vivo are highlighted.

Optimization of Dendritic Polypeptide Delivery System for Antisense Antibacterial Agents Targeting ftsZ

There is an urgent requirement for a novel treatment strategy for drug-resistant Staphylococcus aureus (S. aureus) infection. Antisense antimicrobials are promising antimicrobials, and efficient drug delivery systems are necessary for the further development of antisense antimicrobials. To develop new antisense drugs and further improve delivery efficiency and safety, we designed and screened new antisense sequences and optimized dendritic polypeptide nanoparticles (DP-AD) discovered in previous studies. The N/P ratio is optimized from 8:1 to 6:1, and the positive charge number of the optimized DP-AD is studied comprehensively. The results show that the N/P ratio and positive charge number have no significant effect on the particle size distribution and transport efficiency of DP-AD. Reducing the N/P ratio can significantly reduce the cytotoxicity of DP-AD, but it does not affect its delivery efficiency and antibacterial activity. However, in drug-resistant strains, the antibacterial activity of DP-AD76:1 with 10 positive charges is higher than that of DP-AD86:1 with 8 positive charges. Our research discovered a novel ASOs targeting ftsZ and concluded that DP-AD76:1 with 10 positive charges was the optimal choice at the current stage, which provided a promising strategy for the treatment of drug-resistant S. aureus.

Efficacy of a mouthwash containing ε-poly-L-lysine, funme peptides and domiphen in reducing halitosis and supragingival plaque: a randomized clinical trial

OBJECTIVE

To evaluate the antibacterial effectiveness of a combination of ε-poly-L-lysine (ε-PL), funme peptide (FP) as well as domiphen against oral pathogens, and assess the efficacy of a BOP® mouthwash supplemented with this combination in reducing halitosis and supragingival plaque in a clinical trial.

MATERIALS AND METHODS

The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the compound against Fusobacterium nucleatum, Porphyromonas gingivalis, Streptococcus mutans, and Aggregatibacter actinomycetemcomitans were determined by the gradient dilution method. Subsequently, the CCK-8 assay was used to detect the toxicity of mouthwash on human gingival fibroblastst, and the effectiveness in reducing halitosis and supragingival plaque of the mouthwash supplemented with the combination was analyzed by a randomized, double-blind, parallel-controlled clinical trial.

RESULTS

The combination exhibited significant inhibitory effects on tested oral pathogens with the MIC < 1.56% (v/v) and the MBC < 3.13% (v/v), and the mouthwash containing this combination did not inhibit the viability of human gingival fibroblasts at the test concentrations. The clinical trial showed that the test group displayed notably lower volatile sulfur compounds (VSCs) at 0, 10, 24 h, and 7 d post-mouthwash (P < 0.05), compared with the baseline. After 7 days, the VSC levels of the and control groups were reduced by 50.27% and 32.12%, respectively, and notably cutting severe halitosis by 57.03% in the test group. Additionally, the Plaque Index (PLI) of the test and control group decreased by 54.55% and 8.38%, respectively, and there was a significant difference in PLI between the two groups after 7 days (P < 0.01).

CONCLUSIONS

The combination of ε-PL, FP and domiphen demonstrated potent inhibitory and bactericidal effects against the tested oral pathogens, and the newly formulated mouthwash added with the combination exhibited anti-dental plaque and anti-halitosis properties in a clinical trial and was safe.

TRIAL REGISTRATION

The randomized controlled clinical trial was registered on Chinese Clinical Trial Registry (No. ChiCTR2300073816, Date: 21/07/2023).

Efficacy of adjunctive photodynamic therapy to conventional mechanical debridement for peri-implant mucositis

OBJECTIVE

This meta-analysis was conducted to assess the effectiveness of photodynamic therapy (PDT) as an adjunct to conventional mechanical debridement (CMD) for the management of peri-implant mucositis (p-iM).

METHODS

We systematically searched four databases (PubMed, Embase, Web of Science, and Cochrane Library) for randomized controlled trials (RCTs) investigating PDT + CMD for p-iM from their inception to March 13, 2023. Meta-analysis was performed using RevMan 5.4 software.

RESULTS

Seven RCTs met the inclusion criteria. The meta-analysis revealed that PDT + CMD treatment was more effective than CMD alone in reducing probing depth (PD) (Mean Difference [MD]: -1.09, 95% Confidence Interval [CI]: -1.99 to -0.2, P = 0.02) and plaque index (PI) (MD: -2.06, 95% CI: -2.81 to -1.31, P < 0.00001). However, there was no statistically significant difference in the improvement of bleeding on probing (BOP) between the PDT + CMD groups and CMD groups (MD: -0.97, 95% CI: -2.81 to 0.88, P = 0.31).

CONCLUSIONS

Based on the current available evidence, this meta-analysis indicates that the addition of PDT to CMD significantly improves PD and PI compared to CMD alone in the treatment of p-iM. However, there is no significant difference in improving BOP.

Machine learning enabled design features of antimicrobial peptides selectively targeting peri-implant disease progression

Peri-implantitis is a complex infectious disease that manifests as progressive loss of alveolar bone around the dental implants and hyper-inflammation associated with microbial dysbiosis. Using antibiotics in treating peri-implantitis is controversial because of antibiotic resistance threats, the non-selective suppression of pathogens and commensals within the microbial community, and potentially serious systemic sequelae. Therefore, conventional treatment for peri-implantitis comprises mechanical debridement by nonsurgical or surgical approaches with adjunct local microbicidal agents. Consequently, current treatment options may not prevent relapses, as the pathogens either remain unaffected or quickly re-emerge after treatment. Successful mitigation of disease progression in peri-implantitis requires a specific mode of treatment capable of targeting keystone pathogens and restoring bacterial community balance toward commensal species. Antimicrobial peptides (AMPs) hold promise as alternative therapeutics through their bacterial specificity and targeted inhibitory activity. However, peptide sequence space exhibits complex relationships such as sparse vector encoding of sequences, including combinatorial and discrete functions describing peptide antimicrobial activity. In this paper, we generated a transparent Machine Learning (ML) model that identifies sequence-function relationships based on rough set theory using simple summaries of the hydropathic features of AMPs. Comparing the hydropathic features of peptides according to their differential activity for different classes of bacteria empowered predictability of antimicrobial targeting. Enriching the sequence diversity by a genetic algorithm, we generated numerous candidate AMPs designed for selectively targeting pathogens and predicted their activity using classifying rough sets. Empirical growth inhibition data is iteratively fed back into our ML training to generate new peptides, resulting in increasingly more rigorous rules for which peptides match targeted inhibition levels for specific bacterial strains. The subsequent top scoring candidates were empirically tested for their inhibition against keystone and accessory peri-implantitis pathogens as well as an oral commensal bacterium. A novel peptide, VL-13, was confirmed to be selectively active against a keystone pathogen. Considering the continually increasing number of oral implants placed each year and the complexity of the disease progression, prevalence of peri-implant diseases continues to rise. Our approach offers transparent ML-enabled paths towards developing antimicrobial peptide-based therapies targeting the changes in the microbial communities that can beneficially impact disease progression.

Beta-defensin index: A functional biomarker for oral cancer detection

There is an unmet clinical need for a non-invasive and cost-effective test for oral squamous cell carcinoma (OSCC) that informs clinicians when a biopsy is warranted. Human beta-defensin 3 (hBD-3), an epithelial cell-derived anti-microbial peptide, is pro-tumorigenic and overexpressed in early-stage OSCC compared to hBD-2. We validate this expression dichotomy in carcinoma in situ and OSCC lesions using immunofluorescence microscopy and flow cytometry. The proportion of hBD-3/hBD-2 levels in non-invasively collected lesional cells compared to contralateral normal cells, obtained by ELISA, generates the beta-defensin index (BDI). Proof-of-principle and blinded discovery studies demonstrate that BDI discriminates OSCC from benign lesions. A multi-center validation study shows sensitivity and specificity values of 98.2% (95% confidence interval [CI] 90.3-99.9) and 82.6% (95% CI 68.6-92.2), respectively. A proof-of-principle study shows that BDI is adaptable to a point-of-care assay using microfluidics. We propose that BDI may fulfill a major unmet need in low-socioeconomic countries where pathology services are lacking.

Addressing Antimicrobial Properties in Guided Tissue/Bone Regeneration Membrane: Enhancing Effectiveness in Periodontitis Treatment

Guided tissue regeneration (GTR) and guided bone regeneration (GBR) are the two surgical techniques generally used for periodontitis disease treatment. These techniques are based on a barrier membrane to direct the growth of new bone and gingival tissue at sites with insufficient volumes or dimensions of bone or gingiva for proper function, esthetics, or prosthetic restoration. Numerous studies have highlighted biocompatibility, space-creation, cell-blocking, bioactivity, and proper handling as essential characteristics of a membrane's performance. Given that bacterial infection is the primary cause of periodontitis, we strongly believe that addressing the antimicrobial properties of these membranes is of utmost importance. Indeed, the absence of effective inhibition of periodontal pathogens has been recognized as a primary factor contributing to the failure of GTR/GBR membranes. Therefore, we suggest considering antimicrobial properties as one of the key factors in the design of GTR/GBR membranes. Antibiotics are potent medications frequently administered systemically to combat microbes and mitigate bacterial infections. Nevertheless, the excessive use of antibiotics has resulted in a surge in bacterial resistance. To overcome this challenge, alternative antibacterial substances have been developed. In this review, we explore the utilization of alternative substances with antimicrobial properties for topical application in membranes. The use of antibacterial nanoparticles, phytochemical compounds, and antimicrobial peptides in this context was investigated. By carefully selecting and integrating antimicrobial agents into GTR/GBR membranes, we can significantly enhance their effectiveness in combating periodontitis. These antibacterial substances not only act as barriers against pathogenic bacteria but also promote the process of periodontal healing.

The anti-fungal effect of miconazole and miconazole-loaded chitosan nanoparticles gels in diabetic patients with Oral candidiasis-randomized control clinical trial and microbiological analysis

BACKGROUND

Oral thrush is the most common occurring fungal infection in the oral cavity in uncontrolled diabetic patients, it is treated by various antifungal drugs according to each case. This study aimed to evaluate the therapeutic effects of topical application of miconazole and miconazole-loaded chitosan nanoparticles in treatment of diabetic patients with oral candidiasis.

METHODS

In this randomized controlled clinical trial. A total of 80 diabetic patients presenting with symptomatic oral candidiasis were randomly assigned into two treatment groups: miconazole and miconazole-loaded chitosan nanoparticles. The patients were treated for 28 days, and clinical assessments were conducted at baseline, 7, 14, 21 and 28 days. Clinical parameters, including signs and symptoms of oral candidiasis were evaluated and microbiological analysis was performed to determine the Candida species and assess their susceptibility to the antifungal agents. Statistical analysis was done to the categorical and numerical data using chi-square test and Kruskal Wallis test.

RESULTS

The antifungal efficacy between the miconazole and miconazole-loaded chitosan nanoparticles (CS-MCZ) groups insignificant difference (P >  0.05) was observed. Both treatment modalities exhibited comparable effectiveness in controlling oral candidiasis symptoms and reducing Candida colonization as miconazole-loaded chitosan nanoparticles group showed a significant difference in the clinical improvement in respect of both signs and symptoms from baseline (70%) until the end of study at 28 days (5%) (P <  0.05) Moreover, miconazole-loaded chitosan nanoparticles, there was a significant reduction in the number of colonies forming units of Candida albicans from baseline until the end of the study at 28-day with P value <  0.000.

CONCLUSIONS

This randomized controlled clinical trial and microbiological analysis demonstrate that both miconazole and miconazole-loaded chitosan nanoparticles are effective in the treatment of oral candidiasis in diabetic patients with no adverse reactions.

TRIAL REGISTRATION

NCT06072716 with first registration first registration in 10/10/2023.

Effects of two novel denture cleansers on multispecies microbial biofilms, stain removal and the denture surface: an in vitro study

BACKGROUND

The continuously increasing demand for removable denture appliances and the importance of adequate denture cleaning have led to the development of various denture cleansing products. The aim of this study was to evaluate the efficacy of two novel denture cleansing agents (GE and TM) and three commonly available cleansers (0.5% sodium hypochlorite; NaClO, 0.12% chlorhexidine gluconate; CHX, and Polident®; POL) on multispecies microbial biofilm formation, stain removal and physical properties of dentures.

METHODS

The antimicrobial activities of denture cleansing agents were determined against major oral opportunistic pathogens including Streptococcus mutans, Staphylococcus aureus, Escherichia coli and Candida albicans, using time-kill assays. Multispecies microbial biofilms grown on acrylic resins for 72 h were generated to determine the antibiofilm effects of cleansing agents by confocal laser scanning microscopy (CLSM). Evaluations of the tea and coffee stain removal properties and the alterations in the physical properties of dentures were also performed. The toxicity of cleanser residues released from denture acrylics to fibroblast cells was investigated using MTT assay.

RESULTS

All denture cleansing agents tested could effectively kill oral bacteria and Candida albicans. Furthermore, after immersion for more than 3 h, the cleansers Polident®, GE and TM could efficiently penetrate and inhibit multispecies denture biofilms with effects similar to 10 min of immersion in 0.5% NaClO. However, immersion in 0.12% CHX for 20 min showed less antibiofilm activity. The NaClO solution had the highest efficacy for removing stains from the artificial teeth. Conversely, the CHX solution enhanced tea and coffee staining, and the teeth immersed in this solution showed clinically unacceptable colour changes (ΔE > 5.5). However, the colour differences of teeth stained and immersed in POL, GE and TM cleansers were in the clinically acceptable range. There was no significant difference among the POL, GE and TM cleansers in terms of stain removal efficacy. The cleansers GE and TM did not alter the surface roughness and colour of the materials, moreover the residues of both cleansers did not exhibit cytotoxicity.

CONCLUSION

Two novel denture cleansing agents containing natural products, GE and TM exhibited effective antimicrobial activity, antibiofilm and stain removal capabilities without toxicity or disturbance of the physical properties of acrylics.

α-Mangostin and lawsone methyl ether in tooth gel synergistically increase its antimicrobial and antibiofilm formation effects in vitro

OBJECTIVES

α-Mangostin (α-MG) and lawsone methyl ether (LME) show antimicrobial and anti-biofilm activities. The objectives of this study were to develop a herbal tooth gel containing α-MG and LME plus fluoride and determine its antimicrobial, anti-biofilm formation, anti-cancer, anti-inflammatory, wound healing, and enamel microhardness effects.

METHODS

Antimicrobial assays against Streptococcus mutans, Porphyromonas gingivalis, and Candida albicans were performed. The microbes' ultrastructural morphology was assessed using Transmission Electron Microscopy. The effect on microbial biofilm formation was tested by a broth microdilution. Cell viability was assessed with MTT assay. The anti-inflammatory effect was investigated by measuring inhibition of nitric oxide production. Enamel microhardness was measured via Vickers microhardness testing. The enamel chemical composition was investigated with Fourier Transform Spectrometer. The enamel surface morphology and fluoride content were examined by Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy.

RESULTS

The results show synergistic effects of α-MG and LME on antimicrobial activity and antibiofilm formation without cytotoxicity at a therapeutic dose. At a higher dose, the tooth gel inhibited proliferation of cancer cell line. Enamel microhardness was increased after brushing with the tooth gel plus fluoride. A large amount of fluoride was detected on the enamel surface.

CONCLUSION

The tooth gel containing α-MG and LME synergized its antimicrobial activity and antibiofilm formation and inhibited oral cancer cell proliferation. Incorporating fluoride into the tooth gel increased enamel microhardness. Thus, the herbal tooth gel containing α-MG and LME plus fluoride may be useful for preventing dental caries and promoting oral health.

Functional liposome loaded curcumin for the treatment of Streptococcus mutans biofilm

Introduction: Plaque biofilms, mainly formed by Streptococcus mutans (S. mutans), play an important role in the occurrence and development of dental caries. Antibiotic treatment is the traditional way to control plaque. However, problems such as poor drug penetration and antibiotic resistance have encouraged the search for alternative strategies. In this paper, we hope to avoid antibiotic resistance through the antibacterial effect of curcumin, a natural plant extract with photodynamic effects, on S. mutans. However, the clinical application of curcumin is limited due to its low water solubility, poor stability, high metabolic rate, fast clearance rate, and limited bioavailability. In recent years, liposomes have become a widely used drug carrier due to their numerous advantages, such as high drug loading efficiency, high stability in the biological environment, controlled release, biocompatibility, non-toxic, and biodegradability. So, we constructed a curcumin-loaded liposome (Cur@LP) to avoid the defect of curcumin.

Methods: Cur@LP functioned with NHS can adhere to the surface of the S. mutans biofilm by condensation reaction. Liposome (LP) and Cur@LP was characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The cytotoxicity of Cur@LP was evaluated by CCK-8 assay and LDH assay. The adhesion of Cur@LP to S. mutans biofilm was observed by confocal laser scanning microscope (CLSM). The antibiofilm efficiency of Cur@LP were evaluated by crystal violet staining, CLSM, and scanning electron microscope (SEM).

Results: The mean diameter of LP and Cur@LP were 206.67 ± 8.38 nm and 312 ± 18.78 nm respectively. The ζ-potential of LP and Cur@LP were ∼−19.3 mV and ∼−20.8 mV respectively. The encapsulation efficiency of Cur@LP was (42.61 ± 2.19) %, and curcumin was rapidly released up to ±21% at 2 h. Cur@LP has negligible cytotoxicity, and can effectively adhered to the S. mutans biofilm and inhibited its growth.

Discussion: Curcumin has been widely studied in many fields such as cancer, which can be attributed to its antioxidant and anti-inflammatory effects. At present, there are few studies on the delivery of curcumin to S. mutans biofilm. In this study, we verified the adhesion and antibiofilm of Cur@LP to S. mutans biofilm. This biofilm removal strategy has the potential to be translated into the clinic.

Important Roles and Potential Uses of Natural and Synthetic Antimicrobial Peptides (AMPs) in Oral Diseases: Cavity, Periodontal Disease, and Thrush

Numerous epithelial cells and sometimes leukocytes release AMPs as their first line of defense. AMPs encompass cationic histatins, defensins, and cathelicidin to encounter oral pathogens with minimal resistance. However, their concentrations are significantly below the effective levels and AMPs are unstable under physiological conditions due to proteolysis, acid hydrolysis, and salt effects. In parallel to a search for more effective AMPs from natural sources, considerable efforts have focused on synthetic stable and low-cytotoxicy AMPs with significant activities against microorganisms. Using natural AMP templates, various attempts have been used to synthesize sAMPs with different charges, hydrophobicity, chain length, amino acid sequence, and amphipathicity. Thus far, sAMPs have been designed to target Streptococcus mutans and other common oral pathogens. Apart from sAMPs with antifungal activities against Candida albicans, future endeavors should focus on sAMPs with capabilities to promote remineralization and antibacterial adhesion. Delivery systems using nanomaterials and biomolecules are promising to stabilize, reduce cytotoxicity, and improve the antimicrobial activities of AMPs against oral pathogens. Nanostructured AMPs will soon become a viable alternative to antibiotics due to their antimicrobial mechanisms, broad-spectrum antimicrobial activity, low drug residue, and ease of synthesis and modification.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The Scientific Investigation Committee of the American Academy of Restorative Dentistry offers this review of the 2021 dental literature in restorative dentistry to inform busy dentists regarding noteworthy scientific and clinical progress over the past year. Each member of the committee brings discipline-specific expertise to coverage of this broad topical area. Specific subject areas addressed, in order of the appearance in this report, include COVID-19 and the dental profession (new); prosthodontics; periodontics, alveolar bone, and peri-implant tissues; implant dentistry; dental materials and therapeutics; occlusion and temporomandibular disorders; sleep-related breathing disorders; oral medicine and oral and maxillofacial surgery; and dental caries and cariology. The authors focused their efforts on reporting information likely to influence daily dental treatment decisions with an emphasis on future trends in dentistry. With the tremendous volume of dentistry and related literature being published daily, this review cannot possibly be comprehensive. Rather, its purpose is to update interested readers and provide important resource material for those interested in pursuing greater details on their own. It remains our intent to assist colleagues in negotiating the extensive volume of important information being published annually. It is our hope that readers find this work useful in successfully managing the patients and dental problems they encounter.

Cathelicidin LL-37 in Health and Diseases of the Oral Cavity

The mechanisms for maintaining oral cavity homeostasis are subject to the constant influence of many environmental factors, including various chemicals and microorganisms. Most of them act directly on the oral mucosa, which is the mechanical and immune barrier of the oral cavity, and such interaction might lead to the development of various oral pathologies and systemic diseases. Two important players in maintaining oral health or developing oral pathology are the oral microbiota and various immune molecules that are involved in controlling its quantitative and qualitative composition. The LL-37 peptide is an important molecule that upon release from human cathelicidin (hCAP-18) can directly perform antimicrobial action after insertion into surface structures of microorganisms and immunomodulatory function as an agonist of different cell membrane receptors. Oral LL-37 expression is an important factor in oral homeostasis that maintains the physiological microbiota but is also involved in the development of oral dysbiosis, infectious diseases (including viral, bacterial, and fungal infections), autoimmune diseases, and oral carcinomas. This peptide has also been proposed as a marker of inflammation severity and treatment outcome.

Targeting Multidrug Resistance With Antimicrobial Peptide-Decorated Nanoparticles and Polymers

As a category of small peptides frequently found in nature, antimicrobial peptides (AMPs) constitute a major part of the innate immune system of various organisms. Antimicrobial peptides feature various inhibitory effects against fungi, bacteria, viruses, and parasites. Due to the increasing concerns of antibiotic resistance among microorganisms, development of antimicrobial peptides is an emerging tool as a favorable applicability prospect in food, medicine, aquaculture, animal husbandry, and agriculture. This review presents the latest research progress made in the field of antimicrobial peptides, such as their mechanism of action, classification, application status, design techniques, and a review on decoration of nanoparticles and polymers with AMPs that are used in treating multidrug resistance. Lastly, we will highlight recent progress in antiviral peptides to treat emerging viral diseases (e.g., anti-coronavirus peptides) and discuss the outlook of AMP applications.

Development of Antibiofilm Therapeutics Strategies to Overcome Antimicrobial Drug Resistance

A biofilm is a community of stable microorganisms encapsulated in an extracellular matrix produced by themselves. Many types of microorganisms that are found on living hosts or in the environment can form biofilms. These include pathogenic bacteria that can serve as a reservoir for persistent infections, and are culpable for leading to a broad spectrum of chronic illnesses and emergence of antibiotic resistance making them difficult to be treated. The absence of biofilm-targeting antibiotics in the drug discovery pipeline indicates an unmet opportunity for designing new biofilm inhibitors as antimicrobial agents using various strategies and targeting distinct stages of biofilm formation. The strategies available to control biofilm formation include targeting the enzymes and proteins specific to the microorganism and those involved in the adhesion pathways leading to formation of resistant biofilms. This review primarily focuses on the recent strategies and advances responsible for identifying a myriad of antibiofilm agents and their mechanism of biofilm inhibition, including extracellular polymeric substance synthesis inhibitors, adhesion inhibitors, quorum sensing inhibitors, efflux pump inhibitors, and cyclic diguanylate inhibitors. Furthermore, we present the structure–activity relationships (SAR) of these agents, including recently discovered biofilm inhibitors, nature-derived bioactive scaffolds, synthetic small molecules, antimicrobial peptides, bioactive compounds isolated from fungi, non-proteinogenic amino acids and antibiotics. We hope to fuel interest and focus research efforts on the development of agents targeting the uniquely complex, physical and chemical heterogeneous biofilms through a multipronged approach and combinatorial therapeutics for a more effective control and management of biofilms across diseases.

A Novel Antibacterial Gold Nanoparticles Layer with Self-Cleaning Ability by the Production of Oxygen Bubbles

Bacterial contamination of medical devices not only constitutes a serious threat to the health of patients, but also promotes the evolution of bacterial drug-resistance. Here, a new strategy to fabricate...