Akkermansia muciniphila inhibited the periodontitis caused by Fusobacterium nucleatum.

Periodontitis is the most important cause of tooth loss in adults and is closely related to various systemic diseases. Its etiologic factor is plaque biofilm, and the primary treatment modality is plaque control. Studies have confirmed that Fusobacterium nucleatum can cause periodontitis through its virulence factors and copolymerizing effects with other periodontal pathogens, such as the red complex. Inhibiting F. nucleatum is an essential target for preventing periodontitis. The time-consuming and costly traditional periodontal treatment, periodontal scaling, and root planing are a significant burden on individual and public health. Antibiotic use may lead to oral microbial resistance and microbiome imbalance, while probiotics regulate microbial balance. Akkermansia muciniphila is a critical probiotic isolated from the human intestine. It can protect the integrity of the epithelial barrier, regulate and maintain flora homeostasis, improve metabolism, and colonize the oral cavity. Its abundance is inversely correlated with various diseases. We hypothesized that A. muciniphila could inhibit the effects of F. nucleatum and alleviate periodontitis. Bacterial co-culture experiments showed that A. muciniphila could inhibit the expression of the virulence gene of F. nucleatum. After treating gingival epithelial cells (GECs) with F. nucleatum and A. muciniphila, transcriptome sequencing and ELISA experiments on medium supernatant showed that A. muciniphila inhibited the inflammatory effect of F. nucleatum on GECs by inhibiting TLR/MyD88/NF-κB pathway modulation and secretion of inflammatory factors. Finally, animal experiments demonstrated that A. muciniphila could inhibit F. nucleatum-induced periodontitis in BALB/c mice.

pH-responsive DMAEM Monomer for dental caries inhibition.

Previous research indicated that there is an aggregate of microorganism in oral cavity which takes part in promoting the occurrence of dental caries, but few studies on anticaries materials for these 'core microbiome' were developed. And We've found that DMAEM monomer has an obvious inhibitory effect on the growth of Streptococcus mutans and saliva biofilm, but the effect of that on the "core microbiome" of caries need further research. Thus, the objectives of this study were to explore the effect of DMAEM monomer on the core microbiota of dental caries, and to further study its anticaries effect. The changes of microbial structure and metabolic activity of the core microbiota biofilm were detected through measuring lactic acid yield, viable bacteria counts and demineralization depth, et al., and the anticaries potential in vivo of DMAEM monomer was evaluated by rat caries model. Meanwhile, high-throughput sequencing was used to analyze the microbial diversity change of saliva samples of rats. The results showed that DMAEM monomer could inhibit the growth of the core microbiota biofilm, decrease the metabolic activity and the acid production, as well as reduce the ability of demineralization under acidic conditions. Moreover, the degree of caries in the DMAEM group was significantly reduced, and the diversity and the evenness of oral microecology in the rats were statistically higher. In summary, DMAEM monomer could respond to acidic environment, significantly inhibit the cariogenic ability of the 'core microbiome' of caries, and help to maintain the microecological balance of oral cavity.

Biochar colloids facilitate transport and transformation of Cr(VI) in soil: Active site competition coupling with reduction reaction.

Biochar has been demonstrated as an efficient amendment for immobilizing contaminants. However, a certain number of micro/nano-scale particles are inevitably present in the fresh or aged biochar, which may facilitate the downward transport of contaminants along the soil profile, posing a detrimental impact on the groundwater. Herein, the effects of biochar colloids derived from wood chip and wheat straw at two temperatures (350 °C and 500 °C) on the transport and transformation of Cr(VI) in soil were investigated. All biochar colloids facilitated the transport of Cr(VI) in a loam clay Ultisol, which was attributed to the competition between biochar colloids and Cr(VI) for the available sorption sites on the soil surface. Wheat straw biochar colloids caused more transport of Cr(VI) than wood chip ones due to the more negative charge and higher polarity, which resulted in stronger electrostatic repulsion and competition with Cr(VI). It is soluble Cr(VI) that dominated the transport of Cr in the effluent solution, however, the particulate Cr(VI) could be reduced into Cr(III) before being carried by biochar colloids for co-transport. The 350 °C biochar colloids had higher electron donating capacities than 500 °C ones, resulting in more reduction of Cr(VI) and more co-transport as biochar colloids-associated Cr(III) in the effluent. Moreover, the more negatively charged 350 °C biochar colloids could also attach more soil Fe oxides, further facilitating the cotransport of Cr via the formation of a binary or ternary complex. Modeling showed the experimental-consistently results that biochar colloids caused 0.5-7.0 times faster transport of Cr(VI) than no biochar colloids in the long-term period. Our findings demonstrate that biochar colloids can enhance transport and transformation of Cr(VI) in soils, which arouse migration risk concern about in-situ remediation of Cr(VI)-contaminated soils by biochar.

Biochar nanoparticles with different pyrolysis temperatures mediate cadmium transport in water-saturated soils: Effects of ionic strength and humic acid.

Biochar is advocated as an environment-friendly and cost-effective material for removing both heavy metals and organic contaminants in soil remediation. However, our understandings on the cotransport potential of contaminants with the nanoscale biochar downward along soil profiles (e.g., potential environmental risks towards groundwater) remain largely unknown. This study investigated the effects of wheat straw-derived biochar nanoparticles pyrolyzed at 350 °C and 500 °C (BNP350 and BNP500) on the transport of cadmium (Cd(II)) in water-saturated soil packed columns. Different ionic strengths (ISs) without/with humic acid (HA) were tested to mimic the scenarios during soil remediation. BNPs could act as a vehicle mediating Cd(II) transport in soils. At a low IS (1.0 mM KCl), compared to the limited transport of individual Cd(II), BNP500 enhanced (69 times) Cd(II) transport (Cd(II) mass recovery (M) = 7.59%) in soils, which was greater than that by BNP350 (54 times, M = 5.92%), likely due to the higher adsorption of Cd(II) onto BNP500. HA further increased the Cd(II) transport by BNPs (M = 8.40% for BNP350 and M = 11.95% for BNP500), which was mainly due to the increased mobility of BNPs carrying more absorbed Cd(II). In contrast, at a high IS (10 mM KCl), BNP500 dramatically inhibited the transport of Cd(II) (M = 12.9%), decreasing by about 61.6%, compared to the BNPs absence (M = 33.6%). This is because a large amount of BNP500-Cd(II) was retained in soils at a high IS. This inhibition effect of Cd(II) transport by BNPs was reinforced with the presence of HA. Our findings suggest that the pyrolysis temperature of biochar should be carefully considered when applying biochar for in-situ remediation of soils contaminated by heavy metals such as Cd(II) under various organic matter and IS conditions.

Comparison of Red-Complex Bacteria Between Saliva and Subgingival Plaque of Periodontitis Patients: A Systematic Review and Meta-Analysis.

The development of periodontitis is associated with an imbalanced subgingival microbial community enriched with species such as the traditionally classified red-complex bacteria (Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola). Saliva has been suggested as an alternative to subgingival plaque for the microbial analysis due to its easy and non-invasive collection. This systematic review aims to determine whether the levels of red-complex bacteria assessed using saliva reflect those in subgingival plaque from periodontitis patients. The MEDLINE, EMBASE, and Cochrane Library databases were searched up to April 30, 2021. Studies were considered eligible if microbial data of at least one of the red-complex species were reported in both saliva and subgingival plaque from periodontitis patients, based on DNA-based methods. Of the 17 included studies, 4 studies used 16S rRNA gene sequencing techniques, and the rest used PCR-based approaches. The detection frequency of each red-complex species in periodontitis patients was reported to be > 60% in most studies, irrespective of samples types. Meta-analyses revealed that both detection frequencies and relative abundances of red-complex bacteria in saliva were significantly lower than those in subgingival plaque. Moreover, the relative abundances of all 3 bacterial species in saliva showed significantly positive correlation with those in subgingival plaque. In conclusion, current evidence suggests that one-time saliva sampling cannot replace subgingival plaque for microbial analysis of the red-complex bacteria in periodontitis patients. Given the positive microbial associations between saliva and subgingival plaque, a thorough review of longitudinal clinical studies is needed to further assess the role of saliva.

Dental Restorative Materials for Elderly Populations.

The incidence of dental caries, especially root caries, has risen in elderly populations in recent years. Specialized restorative materials are needed due to the specific site of root caries and the age-related changes in general and oral health in the elderly. Unfortunately, the restorative materials commonly used clinically cannot fully meet the requirements in this population. Specifically, the antibacterial, adhesive, remineralization, mechanical, and anti-aging properties of the materials need to be significantly improved for dental caries in the elderly. This review mainly discusses the strengths and weaknesses of currently available materials, including amalgam, glass ionomer cement, and light-cured composite resin, for root caries. It also reviews the studies on novel anti-caries materials divided into three groups, antimicrobial, remineralization, and self-healing materials, and explores their potential in the clinical use for caries in the elderly. Therefore, specific restorative materials for caries in the elderly, especially for root caries, need to be further developed and applied in clinical practice.

Soil colloids affect the aggregation and stability of biochar colloids.

The stability of biochar colloids plays an important role in the transport and fate of contaminants and nutrients in soil. This study aimed to investigate the effects of main soil components, kaolin (Kao), goethite (Goe), and humic acid (HA) colloids on the aggregation kinetics of biochar colloids derived from dairy manure (DM), sewage sludge (SS), and wheat straw (WS). The WS biochar colloid had the highest critical coagulation concentration (CCC) (624 mM) than that of SS (200 mM) and DM (75 mM) due to its richest hydroxyl and carboxyl groups, showing the highest stability. Kao markedly improved the stability of DM and SS biochar colloids with 171% and 52.5% increase of CCC, respectively, by increasing the electrostatic repulsion of the system. However, the WS biochar colloid became more aggregated in the presence of Kao since the hydroxyl and carboxyl functional groups in WS biochar colloid could complex with Kao, generating electrostatic shielding. Goe could rapidly combine with biochar colloids via electrostatic attraction, resulting in the aggregation of SS and WS, while the aggregation rate of DM/Goe mixed colloids was inhibited. The HA increased the electrostatic repulsion of all biochar colloids through adsorbed on the surface of biochar colloids, resulting in the increased steric hindrance and stability of biochar colloids, with the CCC increased from 75 to 624 mM to 827-1012 mM. Our findings reveal that soil kaolin, goethite, and humic acid colloids have remarkable effects on the stability and aggregation of biochar colloid, which will advance understanding of the potential environmental fate and behaviors of biochar colloids.

Physicochemical property and colloidal stability of micron- and nano-particle biochar derived from a variety of feedstock sources.

The ever-increasing land application of biochar may raise the environmental issue of micronparticle (MP) and nanoparticle (NP) biochars for their high mobility or as a carrier to facilitate transport of contaminants in soil. In this study, a variety of biochars were produced from pyrolysis of nine biomass sources and then subjected to the extraction of MP and NP biochars. The diverse physicochemical properties and electrokinetic stability of MP and NP biochars were further investigated. MP and NP biochars accounted for 1.43-20.5% and 0.99-15.3% of bulk biochar and had colloidal particle diameters mainly smaller than 1 µm and 100 nm, respectively. The MP and NP biochars contained more O-containing functional groups and mineral components but less aromatic clusters than bulk biochar. The yield of MP/NP biochars derived from plant sources such as woods, herbs, and agricultural waste was positively linear to the ash content of their bulk biochars but this relationship wasn't applied to the municipal sourced biochar such as manure and sewage sludge. More condensed aromatic rings and functional groups were found in MP/NP biochar from plant biomass than municipal sourced biochar. However, the latter was rich with minerals like carbonates, phosphates, and silicates. Higher functional groups in the plant sourced MP/NP wheat straw biochar accounted for the extremely high stability to resist the whole range of ionic strength studied, while the municipal sourced MP/NP dairy manure biochar with less functional groups and more minerals were readily destabilized, with the Critical Coagulation Concentration (CCC) values of 75 mM and 100 mM, respectively. Overall, this study revealed the size-dependent characteristics of composition and structure as well as high colloidal stability of MPs and NPs which are helpful for prediction of their environmental fate and risk.