Trans-cinnamaldehyde loaded chitosan based nanocapsules display antibacterial and antibiofilm effects against cavity-causing Streptococcus mutans

Natural compounds: new therapeutic approach for inhibition of Streptococcus mutans and dental caries

Streptococcus mutans is recognized as one of the leading causes of dental caries, and biofilm formation by this bacterium plays a key role in dental plaque development and caries progression. Given the increasing resistance of bacteria to antibiotics and the adverse effects of some synthetic antimicrobials, the search for natural alternatives has received increasing attention. The recently published studies have demonstrated that natural compounds (NCs) such as curcumin, cinnamaldehyde, eugenol, thymol, carvacrol, epigallocatechin gallate, farnesol, catechin, inulin, menthol, apigenin, myricetin, oleanolic acid, and resveratrol, have notable antimicrobial properties and can effectively inhibit the growth of Streptococcus mutans. NCs can disrupt bacterial membrane integrity, leading to cell death, and possess the capability to inhibit acid production, which is a key factor in caries development. NCs can also interfere with bacterial adhesion to surfaces, including teeth. The attachment inhibition is achieved by decreasing the expression of adhesion factors such as gtfs, ftf, fruA, and gbpB. NCs can disrupt bacterial metabolism, inhibit biofilm formation, disperse existing biofilm, and interfere with quorum sensing and two-component signal transduction systems. Moreover, novel drug delivery platforms were used to enhance the bioavailability and stability of NCs. Studies have also indicated that NCs exhibit significant efficacy in combination therapies. Notably, curcumin has shown promising results in photodynamic therapy against S. mutans. The current review article analyzes the mechanisms of action of various NCs against S. mutans and investigates their potential as alternative or complementary therapeutic options for managing this bacterium and dental caries.

The advancement of nanosystems for drug delivery in the prevention and treatment of dental caries

The dental caries remains a globally prevalent disease. Although its incidence has decrease due to enhancements in sanitation policies and public health measures, the treatment and prevention of dental caries still pose significant challenges. Within the oral cavity, traditional drug delivery systems suffer from limitation such as inadequate tissue penetration, short duration of action at target site, and low specificity, which minimally affect the prevention and treatment of dental caries. Consequently, nanosystem for drug delivery, offering enhanced drug stability, solubility, and bio-availability while reducing side effects, garnering attention increasing attention in the fight against dental caries. Therefore, this review examines the role of nanosystems for drug delivery in combating dental caries by inhibiting bacteria survival, biofilm formation, demineralization, and promoting remineralization, and exploring their potential to become the mainstream means of prevention and treatment of dental caries in future.

Drug delivery systems loaded with plant-derived natural products for dental caries prevention and treatment

Dental caries, driven by dysbiosis in oral flora and acid accumulation, pose a significant threat to oral health. Traditional methods of managing dental biofilms using broad-spectrum antimicrobials and fluoride face limitations such as microbial resistance. Natural products, with their antimicrobial properties, present a promising solution for managing dental caries, yet their clinical application faces significant challenges, including low bioavailability, variable efficacy, and patient resistance due to sensory properties. Advanced drug delivery systems (DDSs) are emerging to address these limitations by enhancing the delivery and effectiveness of natural products. These systems, such as nanoparticles and micelles, aim to enhance drug solubility, stability, and targeted release, leading to increased therapeutic efficacy and decreased side effects. Furthermore, innovative approaches like pH-responsive nanoparticles offer controlled release triggered by the acidic environment of carious lesions. Despite these technological advancements, further validation is necessary for the clinical application of these DDSs.

Trans-Cinnamaldehyde Inhibition of Pyruvate Dehydrogenase: Effects on Streptococcus mutans Carbohydrate Metabolism

Dental caries is a chronic oral infectious disease, and Streptococcus mutans (S. mutans) plays an important role in the formation of dental caries. Trans-cinnamaldehyde (CA) exhibits broad-spectrum antibacterial activity; however, its target and mechanism of action of CA on S. mutans needs to be further explored. In this study, it was verified that CA could inhibit the growth and biofilm formation of S. mutans. Further proteomic analysis identified 33, 55, and 78 differentially expressed proteins (DEPs) in S. mutans treated with CA for 1, 2, and 4 h, respectively. Bioinformatics analysis showed that CA interfered with carbohydrate metabolism, glycolysis, pyruvate metabolism, and the TCA cycle, as well as amino acid metabolism of S. mutans. Protein interactions suggested that pyruvate dehydrogenase (PDH) plays an important role in the antibacterial effect of CA. Moreover, the upstream and downstream pathways related to PDH were verified by various assays, and the results proved that CA not only suppressed the glucose and sucrose consumption and inhibited glucosyltransferase (GTF) and lactate dehydrogenase (LDH) activities but also decreased the ATP production. Interestingly, the protein interaction, qRT-PCR, and molecular docking analysis showed that PDH might be the target of CA to fight S. mutans. In summary, the study shows that CA interferes with the carbohydrate metabolism of bacteria by inhibiting glycolysis and the tricarboxylic acid (TCA) cycle via binding to PDH, which verifies that PDH is a potential target for the development of new drugs against S. mutans.

Biological fate, functional properties, and design strategies for oral delivery systems for cinnamaldehyde

Cinnamaldehyde (CA) is the main bioactive component extracted from the internal bark of cinnamon trees with many health benefits. In this paper, the bioavailability and biological activities of cinnamaldehyde, and the underlying molecular mechanism are reviewed and discussed, including antioxidant, cardioprotective, anti-inflammatory, anti-obesity, anticancer, and antibacterial properties. Common delivery systems that could improve the stability and bioavailability of CA are also summarized and evaluated, such as micelles, microcapsules, liposomes, nanoparticles, and nanoemulsions. This work provides a comprehensive understanding of the beneficial functions and delivery strategies of CA, which is useful for the future application of CA in the functional food industry.

Multimodal evaluation of drug antibacterial activity reveals cinnamaldehyde analog anti-biofilm effects against Haemophilus influenzae

Biofilm formation by the pathobiont Haemophilus influenzae is associated with human nasopharynx colonization, otitis media in children, and chronic respiratory infections in adults suffering from chronic respiratory diseases such as chronic obstructive pulmonary disease (COPD). β-lactam and quinolone antibiotics are commonly used to treat these infections. However, considering the resistance of biofilm-resident bacteria to antibiotic-mediated killing, the use of antibiotics may be insufficient and require being replaced or complemented with novel strategies. Moreover, unlike the standard minimal inhibitory concentration assay used to assess antibacterial activity against planktonic cells, standardization of methods to evaluate anti-biofilm drug activity is limited. In this work, we detail a panel of protocols for systematic analysis of drug antimicrobial effect on bacterial biofilms, customized to evaluate drug effects against H. influenzae biofilms. Testing of two cinnamaldehyde analogs, (E)-trans-2-nonenal and (E)-3-decen-2-one, demonstrated their effectiveness in both H. influenzae inhibition of biofilm formation and eradication or preformed biofilms. Assay complementarity allowed quantifying the dynamics and extent of the inhibitory effects, also observed for ampicillin resistant clinical strains forming biofilms refractory to this antibiotic. Moreover, cinnamaldehyde analog encapsulation into poly(lactic-co-glycolic acid) (PLGA) polymeric nanoparticles allowed drug vehiculization while maintaining efficacy. Overall, we demonstrate the usefulness of cinnamaldehyde analogs against H. influenzae biofilms, present a test panel that can be easily adapted to a wide range of pathogens and drugs, and highlight the benefits of drug nanoencapsulation towards safe controlled release.

Inhibitory and preventive effects of Arnebia euchroma (Royle) Johnst. root extract on Streptococcus mutans and dental caries in rats

BACKGROUND

Dental caries is one of the prevalent conditions that threaten oral health. Arnebia euchroma (Royle) Johnst. root (AR) extracts exhibit anti-inflammatory, anti-cancer, and antibacterial properties. This study was designed to investigate the antibacterial impact of AR extract on Streptococcus mutans (S. mutans) UA159 and the anti-caries effect on rats.

METHODS

The antibacterial activity of AR extract against S. mutans and its biofilm was determined using the bacterial sensitivity test, the biofilm sensitivity test, and the live-dead staining technique. By fluorescently tagging bacteria, the influence of bacterial adhesion rate was determined. Using a rat caries model, the anti-caries efficacy and safety of AR extract were exhaustively investigated in vivo.

RESULTS

AR extract inhibit not only the growth of S. mutans, but also the generation of S. mutans biofilm, hence destroying and eliminating the biofilm. Moreover, AR extract were able to inhibit S. mutans' adherence to saliva-encapsulated hydroxyapatite (HAP). Further, in a rat model of caries, the AR extract is able to greatly reduce the incidence and severity of caries lesions on the smooth surface and pit and fissure of rat molars, while exhibiting excellent biosafety.

CONCLUSIONS

AR extract exhibit strong antibacterial activity against S. mutans and can lower the incidence and severity of dental cavities in rats. These findings suggest that Arnebia euchroma (Royle) Johnst. could be utilized for the prevention and treatment of dental caries.

pH-responsive polymeric nanomaterials for the treatment of oral biofilm infections

Bacterial and fungal pathogens forming oral biofilms present significant public health challenges due to the failure of antimicrobial drugs. The ability of biofilms to lower pH levels results in dental plaque, leading to gingivitis and cavities. Nanoparticles (NPs) have attracted considerable interest for drug delivery and, thus, as a solution to biofilm-related microbial infections. A novel strategy in this regard involves using pH-responsive polymeric NPs within the acidic microenvironment of oral biofilms. The acidity of the oral biofilm microenvironment is governed by carbohydrate metabolism, accumulation of lactic acid, and extracellular DNA of extracellular polymeric substances by oral biofilm-forming microbial pathogens. This acidity also provides an opportunity to enhance antibacterial activity against biofilm cells using pH-responsive drug delivery approaches. Thus, various polymeric NPs loaded with poorly soluble drugs and responsive to the acidic pH of oral biofilms have been developed. This review focuses on various forms of such polymeric NPs loaded with drugs. The fundamental mechanisms of action of pH-responsive polymeric NPs, their cytological toxicity, and in vivo efficacy testing are thoroughly discussed.

Trans-Cinnamaldehyde-Fighting Streptococcus mutans Using Nature

Streptococcus mutans (S. mutans) is the main cariogenic bacterium with acidophilic properties, in part due to its acid-producing and -resistant properties. As a result of this activity, hard tooth structures may demineralize and form caries. Trans-cinnamaldehyde (TC) is a phytochemical from the cinnamon plant that has established antibacterial properties for Gram-positive and -negative bacteria. This research sought to assess the antibacterial and antibiofilm effects of trans-cinnamaldehyde on S. mutans. TC was diluted to a concentration range of 156.25-5000 μg/mL in dimethyl sulfoxide (DMSO) 0.03-1%, an organic solvent. Antibacterial activity was monitored by testing the range of TC concentrations on 24 h planktonic growth compared with untreated S. mutans. The subminimal bactericidal concentrations (MBCs) were used to evaluate the bacterial distribution and morphology in the biofilms. Our in vitro data established a TC MBC of 2500 μg/mL against planktonic S. mutans using a microplate spectrophotometer. Furthermore, the DMSO-only controls showed no antibacterial effect against planktonic S. mutans. Next, the sub-MBC doses exhibited antibiofilm action at TC doses of ≥625 μg/mL on hydroxyapatite discs, as demonstrated through biofilm analysis using spinning-disk confocal microscopy (SDCM) and high-resolution scanning electron microscopy (HR-SEM). Our findings show that TC possesses potent antibacterial and antibiofilm properties against S. mutans. Our data insinuate that the most effective sub-MBC of TC to bestow these activities is 625 μg/mL.