Adhesion of human gingival fibroblasts/Streptococcus mitis co-culture on the nanocomposite system Chitlac-nAg

Selective Inhibitors of the Inducible Nitric Oxide Synthase as Modulators of Cell Responses in LPS-Stimulated Human Monocytes

Inducible nitric oxide synthase (iNOS) is a crucial enzyme involved in monocyte cell response towards inflammation, and it is responsible for the production of sustained amounts of nitric oxide. This free radical molecule is involved in the defense against pathogens; nevertheless, its continuous and dysregulated production contributes to the development of several pathological conditions, including inflammatory and autoimmune diseases. In the present study, we investigated the effects of two new iNOS inhibitors, i.e., 4-(ethanimidoylamino)-N-(4-fluorophenyl)benzamide hydrobromide (FAB1020) and N-{3-[(ethanimidoylamino)methyl]benzyl}-l-prolinamidedihydrochloride (CM554), on human LPS-stimulated monocytes, using the 1400 W compound as a comparison. Our results show that CM544 and FAB1020 are selective and decrease cytotoxicity, IL-6 secretion and LPS-stimulated monocyte migration. Furthermore, the modulation of iNOS, nitrotyrosine and Nrf2 were analyzed at the protein level. Based on the collected preliminary results, the promising therapeutic value of the investigated compounds emerges, as they appear able to modulate the pro-inflammatory LPS-stimulated response in the low micromolar range in human monocytes.

Applications of Silver Nanoparticles in Dentistry: Advances and Technological Innovation

Silver nanoparticles (AgNPs) have been successfully applied in several areas due to their significant antimicrobial activity against several microorganisms. In dentistry, AgNP can be applied in disinfection, prophylaxis, and prevention of infections in the oral cavity. In this work, the use of silver nanoparticles in dentistry and associated technological innovations was analyzed. The scientific literature was searched using PubMed and Scopus databases with descriptors related to the use of silver nanoparticles in dentistry, resulting in 90 open-access articles. The search for patents was restricted to the A61K code (International Patent Classification), using the same descriptors, resulting in 206 patents. The results found were ordered by dental specialties and demonstrated the incorporation of AgNPs in different areas of dentistry. In this context, the search for patents reaffirmed the growth of this technology and the dominance of the USA pharmaceutical industry over AgNPs product development. It could be concluded that nanotechnology is a promising area in dentistry with several applications.

Material characterization and Streptococcus oralis adhesion on Polyetheretherketone (PEEK) and titanium surfaces used in implantology

The aim of this study was to evaluate the interaction between Streptococcus oralis and Polyetheretherketone (PEEK), a novel material recently introduced in implantology. The topographical characterization and the Streptococcus oralis adhesion on this material were compared with other titanium surfaces, currently used for the production of dental implants: machined and double etched (DAE). The superficial micro-roughness of the PEEK discs was analyzed by scanning electron microscopy (SEM) and, the Energy Dispersive Spectrometer (EDS) analyzed their chemical composition. Atomic Force Microscopy (AFM) was used to characterize the micro-topography and the sessile method to evaluate the wettability of the samples. Microbiological analysis measured the colony forming units (CFUs), the biomass (OD₅₇₀ detection) and the cell viability after 24 and 48 h after Streptococcus oralis cultivation on the different discs, that were previously incubated with saliva. Results showed that PEEK was characterized by a micro-roughness that was similar to machined titanium but at nano-level the nano-roughness was significantly higher in respect to the other samples. The EDS showed that PEEK superficial composition was characterized mainly by Carbonium and Oxygen. The hydrophilicity and wetting properties of PEEK were similar to machined titanium; on the contrary, double etched discs (DAE) samples were characterized by significantly higher levels (p < 0.05). PEEK was characterized by significant lower CFUs, biomass and viable cells in respect to the titanium surfaces. No differences were found between machined and DAE. The anti-adhesive and antibacterial properties showed by PEEK at 24 and 48 h against a pioneer such as S. oralis, could have an important role in the prevention of all pathologies connected with biofilm formation, like peri-implantitis in dentistry or prosthetic failures in orthopedics.

Redox Control of IL-6-Mediated Dental Pulp Stem-Cell Differentiation on Alginate/Hydroxyapatite Biocomposites for Bone Ingrowth

Composites and porous scaffolds produced with biodegradable natural polymers are very promising constructs which show high biocompatibility and suitable mechanical properties, with the possibility to be functionalized with growth factors involved in bone formation. For this purpose, alginate/hydroxyapatite (Alg/HAp) composite scaffolds using a novel production design were successfully developed and tested for their biocompatibility and osteoconductive properties in vitro. Redox homeostasis is crucial for dental pulp stem cell (DPSC) differentiation and mineralized matrix deposition, and interleukin-6 (IL-6) was found to be involved not only in immunomodulation but also in cell proliferation and differentiation. In the present study, we evaluated molecular pathways underlying the intracellular balance between redox homeostasis and extracellular matrix mineralization of DPSCs in the presence of composite scaffolds made of alginate and nano-hydroxyapatite (Alg/HAp). Prostaglandin-2 (PGE2) and IL-6 secretion was monitored by ELISA assays, and protein expression levels were quantified by Western blotting. This work aims to demonstrate a relationship between DPSC capacity to secrete a mineralized matrix in the presence of Alg/HAp scaffolds and their immunomodulatory properties. The variation of the molecular axis Nrf2 (nuclear factor erythroid 2-related factor 2)/PGE2/IL-6 suggests a tight intracellular balance between oxidative stress responses and DPSC differentiation in the presence of Alg/HAp scaffolds.

Chitlac-coated Thermosets Enhance Osteogenesis and Angiogenesis in a Co-culture of Dental Pulp Stem Cells and Endothelial Cells

Dental pulp stem cells (DPSCs) represent a population of stem cells which could be useful in oral and maxillofacial reconstruction. They are part of the periendothelial niche, where their crosstalk with endothelial cells is crucial in the cellular response to biomaterials used for dental restorations. DPSCs and the endothelial cell line EA.hy926 were co-cultured in the presence of Chitlac-coated thermosets in culture conditions inducing, in turn, osteogenic or angiogenic differentiation. Cell proliferation was evaluated by 3-[4,5-dimethyl-thiazol-2-yl-]-2,5-diphenyl tetrazolium bromide (MTT) assay. DPSC differentiation was assessed by measuring Alkaline Phosphtase (ALP) activity and Alizarin Red S staining, while the formation of new vessels was monitored by optical microscopy. The IL-6 and PGE2 production was evaluated as well. When cultured together, the proliferation is increased, as is the DPSC osteogenic differentiation and EA.hy926 vessel formation. The presence of thermosets appears either not to disturb the system balance or even to improve the osteogenic and angiogenic differentiation. Chitlac-coated thermosets confirm their biocompatibility in the present co-culture model, being capable of improving the differentiation of both cell types. Furthermore, the assessed co-culture appears to be a useful tool to investigate cell response toward newly synthesized or commercially available biomaterials, as well as to evaluate their engraftment potential in restorative dentistry.

Real-Time Imaging of Bacteria/Osteoblast Dynamic Coculture on Bone Implant Material in an in Vitro Postoperative Contamination Model

Biomedical implants are an important part of evolving modern medicine but have a potential drawback in the form of postoperative pathogenic infection. Accordingly, the "race for surface" combat between invasive bacteria and host cells determines the fate of implants. Hence, proper in vitro systems are required to assess effective strategies to avoid infection. In this study, we developed a real time observation model, mimicking postoperative contamination, designed to follow E. coli proliferation on a titanium surface occupied by human osteoblastic progenitor cells (STRO). This model allowed us to monitor E. coli invasion of human cells on titanium surfaces coated and uncoated with fibronectin. We showed that the surface colonization of bacteria is significantly enhanced on fibronectin coated surfaces irrespective of whether areas were uncovered or covered with human cells. We further revealed that bacterial colonization of the titanium surfaces is enhanced in coculture with STRO cells. Finally, this coculture system provides a comprehensive system to describe in vitro and in situ bacterial and human cells and their localization but also to target biological mechanisms involved in adhesion as well as in interactions with surfaces, thanks to fluorescent labeling. This system is thus an efficient method for studies related to the design and function of new biomaterials.

Improvements on biological and antimicrobial properties of titanium modified by AgNPs-loaded chitosan-heparin polyelectrolyte multilayers

Microbial infection around dental implants is a major cause for the loss of devices, including soft tissue infection in early period, post-operation peri-implantitis, and osseointegration failure. Silver nanoparticles (AgNPs) with wide antimicrobial spectrum, strong antimicrobial effect and hypotoxicity, as well as low incidence of antibiotic resistance, are widely involved in biomedical applications. Herein, firmly anchoring AgNPs onto the surface of implants through physical-chemical reaction is likely to relieve the above issues. In this study, AgNPs were biosynthesized by a simple and "green" method with chitosan (CS) as stabilizing and reducing agents. Then, AgNPs-loaded CS-heparin polyelectrolyte multilayers (PEMs) were constructed on alkali-heat treated titanium (Ti) substrates via layer-by-layer (LbL) self-assembly technique. The successful surface modification could be confirmed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), and the constructed system could provide the continuous release of Ag⁺ over 28 days till mucosa healing. In short, this work revealed that the construction of multilayer coatings containing AgNPs on Ti substrates promoted adhesion and proliferation of human gingival fibroblasts (HGFs) and also enhanced the antimicrobial properties. This manifests the LbL technique is a viable and promising method for forming continuous antimicrobial coatings, to reduce microbial infection and improve the quality of peri-implant soft tissue seal. The preparation process of AgNPs-loaded CS-heparin PEMs on Ti substrate.

Application of Antimicrobial Nanoparticles in Dentistry

Oral cavity incessantly encounters a plethora of microorganisms. Plaque biofilm-a major cause of caries, periodontitis and other dental diseases-is a complex community of bacteria or fungi that causes infection by protecting pathogenic microorganisms from external drug agents and escaping the host defense mechanisms. Antimicrobial nanoparticles are promising because of several advantages such as ultra-small sizes, large surface-area-to-mass ratio and special physical and chemical properties. To better summarize explorations of antimicrobial nanoparticles and provide directions for future studies, we present the following critical review. The keywords "nanoparticle," "anti-infective or antibacterial or antimicrobial" and "dentistry" were retrieved from Pubmed, Scopus, Embase and Web of Science databases in the last five years. A total of 172 articles met the requirements were included and discussed in this review. The results show that superior antibacterial properties of nanoparticle biomaterials bring broad prospects in the oral field. This review presents the development, applications and underneath mechanisms of antibacterial nanoparticles in dentistry including restorative dentistry, endodontics, implantology, orthodontics, dental prostheses and periodontal field.

Preparation and biological characterization of the mixture of poly(lactic-co-glycolic acid)/chitosan/Ag nanoparticles for periodontal tissue engineering

Objective

This study aims to produce nanoparticles of chitosan (CS), poly(lactic-co-glycolic acid) (PLGA), and silver and investigate the optimal composite ratio of these three materials for periodontal tissue regeneration.

Methods

PLGA nanoparticles (nPLGA), CS nanoparticles (nCS), and silver nanoparticles (nAg) were prepared. The antibacterial properties of single nanoparticles and their effects on the proliferation and mineralization of periodontal membrane cells were investigated. Different ratios of nPLGA and nCS were combined, the proliferation and mineralization of periodontal membrane cells were investigated, and based on the results, the optimal ratio was determined. Finally, nPLGA and nCS in optimal ratio were combined with nAg, and the effects of the complex of these three materials on the proliferation and mineralization of periodontal membrane cells were investigated and tested in animals.

Results

The single nanoparticles were found to have no cytotoxicity and were able to promote cell mineralization. nCS and nAg in low concentrations showed antibacterial activity; however, nAg inhibited cell proliferation. The nPLGA and nCS complex in 3:7 ratio contributed to cell mineralization and had no cytotoxicity. nPLGA/nCS/nAg complex, which had the optimal proportion of the three materials, showed no cytotoxicity and contributed to cell mineralization.

Conclusion

nPLGA/nCS/nAg complex had no cytotoxicity and contributed to cell mineralization. The 3:7 ratio of nPLGA/nCS and 50 µg/mL nAg were found as the optimal proportion of the three materials.

An overview of application of silver nanoparticles for biomaterials in dentistry

Oral cavity is a gateway to the entire body and protection of this gateway is a major goal in dentistry. Plaque biofilm is a major cause of majority of dental diseases and although various biomaterials have been applied for their cure, limitations pertaining to the material properties prevent achievement of desired outcomes. Nanoparticle applications have become useful tools for various dental applications in endodontics, periodontics, restorative dentistry, orthodontics and oral cancers. Off these, silver nanoparticles (AgNPs) have been used in medicine and dentistry due to its antimicrobial properties. AgNPs have been incorporated into biomaterials in order to prevent or reduce biofilm formation. Due to greater surface to volume ratio and small particle size, they possess excellent antimicrobial action without affecting the mechanical properties of the material. This unique property of AgNPs makes these materials as fillers of choice in different biomaterials whereby they play a vital role in improving the properties. This review aims to discuss the influence of addition of AgNPs to various biomaterials used in different dental applications.

Molecular mechanisms driving Streptococcus mitis entry into human gingival fibroblasts in presence of chitlac-nAg and saliva

The molecular mechanisms leading to Streptococcus mitis capability of entering oral cells were investigated in a co-culture of S. mitis and Human Gingival Fibroblasts (HGFs) in the presence of saliva. An innovative colloidal solution based on silver nanoparticles (Chitlac-nAg), a promising device for daily oral care, was added to the experimental system in order to study the effects of silver on the bacterial overgrowth and ability to enter non-phagocytic eukaryotic cells. The entry of bacteria into the eukaryotic cells is mediated by a signalling pathway involving FAK, integrin β1, and the two cytoskeleton proteins vinculin and F-actin, and down-regulated by the presence of saliva both at 3 and 48 h of culture, whereas Chitlac-n Ag exposure seems to influence, by incrementing it, the number of bacteria entering the fibroblasts only at 48 h. The formation of fibrillary extrusion from HGFs and the co-localization of bacteria and silver nanoparticles within the fibroblast vacuoles were also recorded. After longer experimental times (72 and 96 h), the number of S. mitis chains inside gingival cells is reduced, mainly in presence of saliva. The results suggest an escape of bacteria from fibroblasts to restore the microbial balance of the oral cavity.