Molecular mechanisms driving <Emphasis Type="Italic">Streptococcus mitis</Emphasis> 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.

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RGD修饰纯钛表面对人牙龈成纤维细胞生物学行为的影响

用羰基二咪唑(1,1′-carbonyldiimidazole,CDI),将含RGD的短肽共价连接到纯钛的表面,将HGFs分别接种到涂层和未涂层材料表面并培养一定时间后,定量对比接枝和未接枝材料表面的细胞纤粘连蛋白(fibronectin,FN)和粘着斑的形成情况,研究接枝后的纯钛表面对原代培养的人牙龈成纤维细胞(Human Gingival Fibroblasts,HGF)生物学行为的影响.结果表明,RGD修饰的纯钛表面粘着斑的形成比钛表面早.RGD接枝钛表面有利于人牙龈成纤维细胞的粘附,改善了纯钛的生物相容性.     

RGD修饰钛表面对人牙龈成纤维细胞初期黏附和铺展的影响

用羰基二咪唑(1,1'-carbonyldiimidazole,CDI)将含RGD的短肽共价连接到纯钛表面,研究接枝后的钛表面对原代培养的人牙龈成纤维细胞(human gingival fibroblasts,HGF)初期黏附和铺展的影响.结果表明,RGD修饰的纯钛表面粘附的细胞数比未修饰钛表面多,细胞铺展面积比钛表面的大,应力纤维的形成比钛表面早.RGD接枝钛表面更有利于人牙龈成纤维细胞的粘附,改善了纯钛的生物相容性.     

Adhesion of human gingival fibroblasts/<Emphasis Type="Italic">Streptococcus mitis</Emphasis> co-culture on the nanocomposite system Chitlac-nAg

Composite materials are increasingly used as dental restoration. In the field of biomaterials, infections remain the main reason of dental devices failure. Silver, in the form of nanoparticles (AgNPs), ions and salt, well known for its antimicrobial properties, is used in several medical applications in order to avoid bacterial infection. To reduce both bacterial adhesion to dental devices and cytotoxicity against eukaryotic cells, we coated BisGMA/TEGDMA methacrylic thermosets with a new material, Chitlac-nAg, formed by stabilized AgNPs with a polyelectrolyte solution containing Chitlac. Here we analyzed the proliferative and adhesive ability of human gingival fibroblasts (HGFs) on BisGMA/TEGDMA thermosets uncoated and coated with AgNPs in a coculture model system with Streptococcus mitis. After 48 h, HGFs well adhered onto both surfaces, while S. mitis cytotoxic response was higher in the presence of AgNPs coated thermosets. After 24 h thermosets coated with Chitlac as well as those coated with Chitlac-nAg exerted a minimal cytotoxic effect on HGFs, while after 48 h LDH release raised up to 20 %. Moreover the presence of S. mitis reduced this release mainly when HGFs adhered to Chitlac-nAg coated thermosets. The reduced secretion of collagen type I was significant in the presence of both surfaces with the co-culture system even more when saliva is added. Integrin β1 localized closely to cell membranes onto Chitlac-nAg thermosets and PKCα translocated into nuclei. These data confirm that Chitlac-nAg have a promising utilization in the field of restorative dentistry exerting their antimicrobial activity due to AgNPs without cytotoxicity for eukaryotic cells.     

Ultrastructural study of the effects of coral skeleton on cultured human gingival fibroblasts in three-dimensional collagen lattices

Natural coral skeleton has recently been introduced as a bone graft substitute which enhances bone formation in man and animals. The effects of NCS on cultured human cells has not previously been investigated. In the present study we report these effects as studied by light microscopy, transmission and scanning electron microscopy in three-dimensional culture. The results showed that natural coral skeleton does not inhibit the normal function of fibroblasts in contracting collagen lattices. After 8 weeks, the cells maintained a healthy ultrastructural morphology. At the collagen/coral interface, the cells were well-spread and attached to the surface by numerous adhesion plaques. Evidence for biosynthetic activity was also observed; the cells showed numerous ribosomes, mitochondria and prominent rough endoplasmic reticulum. Extracellularly, a perigranular dense matrix, appearing as nodules in the SEM, was deposited on the coral surface. This matrix was made of highly organized fibrils lacking periodicity, and a ground substance. The present study shows that coral was well-tolerated by human gingival fibroblasts, and that it provided a surface for cell spreading, attachment and deposition of the special extracellular matrix.     

Protective effect of maghemite nanoparticles on ultraviolet-induced photo-damage in human skin fibroblasts

This study examined the optical properties of an oxidized form of maghemite (γ-Fe(2)O(3)) nanoparticles and their protective effects against the photoaging of human skin fibroblasts irradiated with ultraviolet (UV) light. Nanoparticles with diameters ranging from 8.7 to 12?nm were prepared using a chemical co-precipitation method. The nanoparticles were coated with two surfactants to obtain a water-based product. The onset of the absorption of the γ-Fe(2)O(3) nanoparticles in the UV-visible absorption spectra increased with increasing particle size. The γ-Fe(2)O(3) nanoparticles significantly inhibited the production of matrix metalloproteinase-1 in human skin fibroblast HS 68 cells by 60% compared with the UV-irradiated control. These results suggest that γ-Fe(2)O(3) nanoparticles have photoprotective properties, and have potential use as an agent against photoaging.     

Influence of Aging and 2-hydroxyethyl-methacrylate Content on the Color Stability of Experimental 2-hydroxyethyl-methacrylate-added Dental Glass Ionomers

Color stability of dental resin modified glass ionomer (RMGI) has been a challenge to dentistry; therefore, systematic changes in 2-hydroxyethyl methacrylate (HEMA) content were performed experimentally to find an idea to enhance the color stability. Changes in color (△E*ab) and color coordinates (△L*, △a* and △b*) of experimental 10-50 wt pct HEMA-added dental glass ionomers (HAGIs) and corresponding RMGIs were determined after 5000 cycles of thermocycling. Color changes of HAGIs were not influenced by the HEMA content while △L*, △a* and △b* values were influenced by the HEMA content. Color stability of 30% or 40% HEMA-added HAGIs was not different from those of the commercial RMGIs. Since the influence of HEMA itself on the color stability of HAGIs was limited, compositional modification to increase the color stability of these materials should be developed.     

Study of the polyelectrolyte multilayer thin films' properties and correlation with the behavior of the human gingival fibroblasts

The relation between fibroblast cell behavior and wettability parameters of different polyelectrolyte multilayers (PEM) was investigated. To this end, three types of film ending with polycations or polyanions were selected: poly(l-lysine)/poly(l-glutamic acid) (PGA/PLL)₅ and (PGA/PLL)₅–PGA, hyaluronan/PLL (HA/PLL)₅ and (HA/PLL)₅–HA, and poly(styrene sulfonate)/poly(allylamine hydrochloride) (PSS/PAH)₁₀ and (PSS/PAH)₁₀–PSS. The film roughness and thickness were measured by AFM and optical waveguide lightmode spectroscopy (OWLS). Surface free energy (SFE), polar (acid, basic and acid–basic) and dispersive components of SFE were determined using the Van Oss approach by dynamic contact angle (DCA) measurements. Cell adhesion was quantified by fluorescent labeling using an image analysis system. Cell morphology was analyzed by scanning electron microscopy (SEM) and phase contrast microscopy. Cell proliferation was followed over a seven day period. Fibroblast adhesion and proliferation were strongly dependent on film type. SEM observations of cells on the different films agreed with the proliferation and adhesion tests.     

Effects of LP-MOCVD prepared TiO2 thin films on the in vitro behavior of gingival fibroblasts

We report on the in vitro response of human gingival fibroblasts (HGF-1 cell line) to various thin films of titanium dioxide (TiO₂) deposited on titanium (Ti) substrates by low pressure metal-organic chemical vapor deposition (LP-MOCVD). The aim was to study the influence of film structural parameters on the cell behavior comparatively with a native-oxide covered titanium specimen, this objective being topical and interesting for materials applications in implantology. HGF-1 cells were cultured on three LP-MOCVD prepared thin films of TiO₂ differentiated by their thickness, roughness, transversal morphology, allotropic composition and wettability, and on a native-oxide covered Ti substrate. Besides traditional tests of cell viability and morphology, the biocompatibility of these materials was evaluated by fibronectin immunostaining, assessment of cell proliferation status and the zymographic evaluation of gelatinolytic activities specific to matrix metalloproteinases secreted by cells grown in contact with studied specimens. The analyzed surfaces proved to influence fibronectin fibril assembly, cell proliferation and capacity to degrade extracellular matrix without considerably affecting cell viability and morphology. The MOCVD of TiO₂ proved effective in positively modifying titanium surface for medical applications. Surface properties playing a crucial role for cell behavior were the wettability and, secondarily, the roughness, HGF-1 cells preferring a moderately rough and wettable TiO₂ coating.     

Studies on cytotoxic effect of nickel ions on three cultured fibroblasts

Cytotoxicity of Ni ions on three fibroblasts such as L929, Balb/3T3 clone A31 and MC3T3–E1 were examined by cell count (CC) and Neutral Red assay (NR). Three cells were incubated for 6 days in 1 ml DME medium containing Ni ions which ranged from 0 to 2 mM/l. The results clarified that Ni ions had dose-dependent cytotoxicity. L929 possessed the largest TC₅₀ values (the amount of Ni ion that caused 50% cell death or 50% cell viability) of 0.12 mM/l (CC) and 0.32 mM/l (NR), and Balb/3T3 clone A31 had the least values of 0.05 mM/l (CC) and 0.09 mM/l (NR), whilst MC3T3–E1 had the intermediate values of 0.08 mM/l (CC) and 0.15 mM/l (NR). The dissolution of Ni ions from Ni-containing metallic restorations must be lower than these concentration levels so that body tissues might not be severely damaged. © 2001 Kluwer Academic Publishers     

Adverse effects of citrate/gold nanoparticles on human dermal fibroblasts

Nanoscale engineering is one of the most dynamically growing areas at the interface between electronics, physics, biology, and medicine. As there are no safety regulations yet, concerns about future health problems are rising. We investigated the effects of citrate/gold nanoparticles at different concentrations and exposure times on human dermal fibroblasts. We found that, as a result of intracellular nanoparticle presence, actin stress fibers disappeared, thereby inducing major adverse effects on cell viability. Thus, properties such as cell spreading and adhesion, cell growth, and protein synthesis to form the extracellular matrix were altered dramatically. These results suggest that the internal cell activities have been damaged.     

The effect of antibacterial agents on the behaviour of cultured mammalian fibroblasts

Wound infections retard healing rates and can lengthen the time a patient is required to spend in hospital. Obviously it is desirable to minimize or remove pathogenic organisms to allow wound healing to progress optimally. At present there are a large range of topical applications available in the form of antibiotics or antiseptics, but the toxic effects of these agents may outweight the benefits. In this study two conventional antiseptic agents were examined together with a range of phosphate-based glasses which were designed to release metal ions into an aqueous environment. As a control a series of standard metal ion solutions were prepared and examined in the same test system. The metal ions examined are considered important in the wound healing environment either for their potential bacteriostatic effects or indeed their potential for increasing cellular activity. This part of the study examined the effects of these agents on mammalian cells in vitro, using a standard MTT assay to assess the cytotoxicity or activity of cultured mouse fibroblasts. It was found that chlorhexidene, a commonly used antiseptic agent, was toxic at low levels. The controlled release glasses, in most cases, increased the rate of cell activity before reaching toxic levels. This effect was also found with the standard metal solutions.     

An investigation of the growth of human dermal fibroblasts on poly-L-lactic acid in vitro

A tissue engineered implant involving cells seeded on bioreserbable materials is an attractive proposition for the repair of soft tissue because in the long term the material is resorbed leading to a natural repair. The aim of this study was to assess the effect of poly-L-lactic acid (PLA) on the growth of human dermal fibroblasts in vitro. The results have been compared to other resorbable materials, polyhydroxybutyrate (PHB), polycaprolactone (PCL) and polyglycolic acid (PGA). Thermanox (Tmx) and tissue culture plastic (Tcp) were used as positive controls. PLA compared favourably with the other bioresorbable materials, as a substrate for fibroblast attachment and proliferation. No evidence of cytotoxicity was observed for cells cultured in polymer extracts. Colonies of adhered fibroblasts were observed on PLA which exhibited normal bipolar morphology when viewed using phase contrast microscopy and cryo-SEM. Cellular proliferation was measured by tritiated thymidine incorporation with total DNA as a baseline. Concerns associated with the use of PLA as the bioresorbable material utilized in tissue regeneration are primarily related to the effect of degradation products on the cellular component. No effect on the growth of dermal fibroblasts was observed in the presence of degradation products or lactic acid standards (0–1000 g/ml/48 h). This study has demonstrated that human dermal fibroblasts proliferated and formed a confluent monolayer on PLA, which may prove to be a suitable scaffold for soft tissue repair systems, providing biomechanical and biodegradation requirements can be fulfilled.This paper was accepted for publication after the 1995 Conference of the European Society of Biomaterials, Oporto, Portugal, 10–13 September.     

DNA fragments induction in human fibroblasts by radiations of different qualities

Experimental data on DNA double strand break (DSB) induction in human fibroblasts (AG1522), following irradiation with several radiation qualities, namely gamma rays, 0.84 MeV protons, 58.9 MeV u(-1) carbon ions, iron ions of 115 MeV u(-1), 414 MeV u(-1), 1 GeV u(-1), and 5 GeV u(-1), are presented. DSB yields were measured by calibrated Pulsed Field Gel Electrophoresis in the DNA fragment size range 0.023-5.7 Mbp. The DSB yields show little LET dependence, in spite of the large variation of the latter among the beams, and are slightly higher than that obtained using gamma rays. The highest yield was found for the 5 GeV u(-1) iron beam, that gave a value 30% higher than the 1 GeV u(-1) iron beam. A phenomenological method is used to parametrise deviation from randomness in fragment size spectra.     

Modeling of the neighborhood topological effect on grain growth in presence of particles pinning

A model for grain growth with the particles effect is suggested. This model, which presents an extension of the von Neumann-Mullins law in presence of pinning particles, predicts two-grain critical numbers. Greater than the minimal critical number or less than the maximal critical number the grain boundary can be moving. Between the two limiting numbers no grain growth takes place. These limiting numbers permit us to introduce the preferential influence of particles on grain boundaries in the simulation procedure. Currently, it is very difficult to include this preferential interaction directly in the classical simulation models. A computer simulation by a modified Monte-Carlo potts technique is used to test our proposed model.     

The influence of elastin-coated 520-nm- and 20-nm-diameter nanoparticles on human fibroblasts in vitro

Magnetic nanoparticles have been used for biomedical purposes for several years. In recent years, nanotechnology has developed to a stage that makes it possible to engineer particles to provide opportunities for the site-specific delivery of drugs. To this end, a variety of iron oxide particles have been synthesized. The size and surface of the particles are crucial factors in the application of the particles. Therefore, this study involves the use of two types of magnetic nanoparticles derivatized with elastin and synthesized with differing diameters, compared with identical underivatized plain particles. This influence in vitro was assessed using human dermal fibroblasts and various techniques to observe cell-particle interaction, including light and fluorescence microscopy and scanning electron microscopy. The results indicate that derivatized particles induce alterations in cell behavior and morphology distinct from the plain particles, suggesting that cell response can be directed via specifically engineered particle surfaces. However, little difference was observed between the different diameters.     

纯钛离子氮化层在人工唾液中的耐蚀性

用浸泡法和电化学法研究了纯钛(TA2)基体材料及其离子氮化层在人工唾液中的腐蚀行为.浸泡法研究表明,试样随着浸泡时间的延长而增重,而离子氮化层增重明显减缓,其腐蚀速率远小于TA2基材;电化学法研究表明,离子氮化层的自腐蚀电位较TA2基材提高,而腐蚀电流密度和腐蚀速度减小.由失重法和电化学法得出一致结论,离子氮化处理提高了TA2在人工唾液中的耐蚀性.     

A method for the evaluation of protective properties of coatings in corrosive media in the presence of propagating cracks

We studied the influence of the state of the specimen surface on the electrochemical conditions at the tip of a corrosion fatigue crack and cyclic corrosion crack-growth resistance of 20 steel in distilled water. It was discovered that aluminum-zinc and zinc coatings protect the specimen surface against local anodic dissolution at the tip of the corrosion-fatigue crack and, hence, significantly increase the cyclic corrosion crack-growth resistance of the specimens as compared to the value typical of the specimens without coatings, although the intensity of hydrogen depolarization and, consequently, the probability of hydrogen embrittlement increase in this case. We propose a procedure and electrochemical parameters for the evaluation of the efficiency of protection of the tip of a propagating corrosion-fatigue crack by metallic coatings.Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 31, No. 3, pp. 14–22, May–June, 1995.     

The effect of hydrogen concentration on fracture of pipeline steels in presence of a notch

The comparative assessment of local fracture initiation at notches in API grade pipeline steels: X52, X70 and X100 have been done for conditions of electrochemical hydrogenating. The factor of hydrogen concentration in metal was taken into account. The relationship between hydrogen concentration in metal and work for initiation of the local fracture emanating from the notch has been derived. The existence of some critical hydrogen concentration, which causes the significant loss of local fracture resistance of material, was also shown and discussed.