Copper@ZIF-8 Core-Shell Nanowires for Reusable Antimicrobial Face Masks.

SARS-CoV-2 and other respiratory viruses spread via aerosols generated by infected people. Face masks can limit transmission. However, widespread use of disposable masks consumes tremendous resources and generates waste. Here, a novel material for treating blown polypropylene filtration media used in medical-grade masks to impart antimicrobial activity is reported. To produce thin copper@ZIF-8 core-shell nanowires (Cu@ZIF-8 NWs), Cu NWs are stabilized using a pluronic F-127 block copolymer, followed by growth of ZIF-8 to obtain uniform core-shell structures. The Cu@ZIF-8 NWs are applied to filtration media by dip coating. Aerosol filtration efficiency decreases upon exposure to ethanol (solvent for dip-coating), but increases with addition of Cu@ZIF-8 NWs. Cu@ZIF-8 NWs shows enhanced antibacterial activity, compared to Cu NWs or ZIF-8 alone, against Streptococcus mutans and Escherichia coli. Antiviral activity against SARS-CoV-2 is assayed using virus-infected Vero E6 cells, demonstrating 55% inhibition of virus replication after 48 h by 1 µg of Cu@ZIF-8 NWs per well. Cu@ZIF-8 NWs' cytotoxicity is tested against four cell lines, and their effect on inflammatory response in A549 cells is examined, demonstrating good biocompatibility. This low-cost, scalable synthesis and straightforward deposition of Cu@ZIF-8 NWs onto filter media has great potential to reduce disease transmission, resource consumption, and environmental impact of waste.

The Msp Protein of Treponema denticola Interrupts Activity of Phosphoinositide Processing in Neutrophils.

Periodontal disease is a significant health burden, causing tooth loss and poor oral and overall systemic health. Dysbiosis of the oral biofilm and a dysfunctional immune response drive chronic inflammation, causing destruction of soft tissue and alveolar bone supporting the teeth. Treponema denticola, a spirochete abundant in the plaque biofilm of patients with severe periodontal disease, perturbs neutrophil function by modulating appropriate phosphoinositide (PIP) signaling. Through a series of immunoblotting and quantitative PCR (qPCR) experiments, we show that Msp does not alter the gene transcription or protein content of key enzymes responsible for PIP3 signaling: 3' phosphatase and tensin homolog (PTEN), phosphatidylinositol 3-kinase (PI3K), or 5' Src homology 2 domain-containing inositol phosphatase 1 (SHIP1). Instead, using immunoblotting and enzyme-linked immunosorbent assays (ELISAs), we found that Msp activates PTEN through dephosphorylation specifically at the S380 site. Msp in intact organisms or outer membrane vesicles also restricts PIP signaling. SHIP1 phosphatase release was assessed using chemical inhibition and immunoprecipitation to show that Msp moderately decreases SHIP1 activity. Msp also prevents secondary activation of the PTEN/PI3K response. We speculate that this result is due to the redirection of the PIP3 substrate away from SHIP1 to PTEN. Immunofluorescence microscopy revealed a redistribution of PTEN from the cytoplasm to the plasma membrane following exposure to Msp, which may contribute to PTEN activation. Mechanisms of how T. denticola modulates and evades the host immune response are still poorly described, and here we provide further mechanistic evidence of how spirochetes modify PIP signaling to dampen neutrophil function. Understanding how oral bacteria evade the immune response to perpetuate the cycle of inflammation and infection is critical for combating periodontal disease to improve overall health outcomes.

Strontium Effects on Human Gingival Fibroblasts.

Strontium is a naturally occurring alkaline earth metal that has been shown to be useful not only in the treatment and prevention of osteoporosis but also in the treatment of dentinal hypersensitivity in the oral cavity; strontium is also an effective cariostatic, antiplaque, antigingivitis agent. Relatively little is known, however, about the effects of strontium on gingival fibroblasts. The purpose of the present investigation was to conduct in vitro studies on the potential for strontium to positively affect the activity of these cells such that it might be effective in the enhancement of gingival attachment to surfaces, such as healing abutments in implants in the oral cavity. The results indicate that strontium added as strontium citrate (0.5-1.0 mM), both in the absence and presence of a healing abutment, increases human gingival cell activity and decreases apoptosis in these cells. Scanning electron microscopy studies also reveal that the addition of strontium increases attachment of gingival fibroblasts to the surfaces of healing abutments. These studies provide the basis for further investigations on the use of strontium in the prevention and treatment of peri-implantitis by maximizing the formation of a peri-implant soft-tissue barrier.

Strontium-loaded hydrogel scaffolds to promote gingival fibroblast function.

Dental implant clinical success is dependent on effective peri-implant tissue attachment to the trans-mucosal portion following placement. Modification of transmucosal implant surfaces can improve cellular adhesion and function leading to formation of an effective soft-tissue seal during healing, of which gingival fibroblasts are prominent cells to migrate to repair wounds and crucial for the development of a collagen rich connective tissue. Biocompatible loaded scaffold materials have been developed to allow local release of molecules with effective biological activity. Our previous studies indicate that strontium can promote gingival fibroblast metabolism, decrease apoptosis and support adhesion to titanium healing abutments. In this study, we developed a strontium-loaded alginate hydrogel scaffold which can be easily personalized to fit over any size and shape of implant transmucosal collar or healing abutment. Results indicate that biologically active strontium ions are effectively released from loaded alginate hydrogel material to promote fibroblast viability and migration to repair in vitro wounds similar to that of strontium citrate solution. Overall, this novel strontium-loaded alginate scaffold device displays good biocompatibility and functionality, demonstrating high potential as a system to provide local delivery of strontium to improve peri-implant mucosal healing following implant placement and clinical success.

Synthesis and antibacterial activity of polymer-antibiotic conjugates incorporated into a resin-based dental adhesive.

This work reports on polymer-antibiotic conjugates (PACs) as additives to resin-based restorative dental materials as a new strategy to convey sustained antibacterial character to these materials. Such antibacterial performance is expected to improve their longevity in the oral cavity. Using the previously reported ciprofloxacin (Cip)-based PAC as a control, a penicillin V (PV)-based PAC was investigated. The monomer-antibiotic conjugate (MAC) containing a methacrylate monomer group and a PV moiety was prepared via nucleophilic substitution between 2-chloroethyl methacrylate (CEMA) and penicillin V potassium (PVK). The PV-based PAC was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of the MAC with hydroxyethyl methacrylate (HEMA), and further characterized by 1H NMR and gel permeation chromatography (GPC) analysis. Antibiotic resistance was investigated by passaging bacteria in low concentrations of the antibiotic for 19 days, followed by a 48 h challenge at higher concentrations. Our results suggest that the development of antibiotic resistance is unlikely. Zone of inhibition (ZOI) assays revealed no clearing zones around PV-containing resins indicating minimal antibiotic leakage from the material. Similarly, MTT assay demonstrated that the antibiotic-containing specimens did not release cytotoxic byproducts that may inhibit human gingival fibroblast growth. Counting of colony-forming units in an S. mutans biofilm model was used to assess bacterial survival at baseline and after subjecting the antibiotic-containing resin specimens to an enzymatic challenge for 30 days. Significantly reduced bacterial counts were observed as the biofilm aged from 24 to 72 h, and salivary enzymatic exposure did not reduce the antibacterial efficacy of the discs, suggesting that PV-resin will be effective in reducing the re-incidence of dental caries.

Treponema denticola stimulates Oncostatin M cytokine release and de novo synthesis in neutrophils and macrophages.

Oncostatin M (OSM) is a pleiotropic cytokine elevated in a number of inflammatory conditions including periodontal disease. OSM is produced by a variety of immune cells and has diverse functionality such as regulation of metabolic processes, cell differentiation, and the inflammatory response to bacterial pathogens. The oral cavity is under constant immune surveillance including complementary neutrophil and macrophage populations, due to a persistent symbiotic bacterial presence. Periodontal disease is characterized by a dysbiotic bacterial community, with an abundance of Treponema denticola. Despite strong associations with severe periodontal disease, the source and mechanism of the release of OSM have not been defined in the oral cavity. We show that OSM protein is elevated in the gingival epithelium and immune cell infiltrate during periodontal disease. Furthermore, salivary and oral neutrophil OSM is elevated in correlation with the presence of T. denticola. In an air pouch infection model, T. denticola stimulated higher levels of OSM than the oral pathogen Porphorymonas gingivalis, despite differential recruitment of innate immune cells suggesting T. denticola has distinct properties to elevate OSM levels. OSM release and transcription were increased in isolated human blood, oral neutrophils, or macrophages exposed to T. denticola in vitro as measured by ELISA, qPCR, and microscopy. Using transcription, translation, and actin polymerization inhibition, we found that T. denticola stimulates both OSM release through degranulation and de novo synthesis in neutrophils and also OSM release and synthesis in macrophages. Differential induction of OSM by T. denticola may promote clinical periodontal disease.