Leticia Esteban-Tejeda

A New Biocompatible and Antibacterial Phosphate Free Glass-Ceramic for Medical Applications

In the attempt to find valid alternatives to classic antibiotics and in view of current limitations in the efficacy of antimicrobial-coated or loaded biomaterials, this work is focused on the development of a new glass-ceramic with antibacterial performance together with safe biocompatibility. This bactericidal glass-ceramic composed of combeite and nepheline crystals in a residual glassy matrix has been obtained using an antimicrobial soda-lime glass as a precursor. Its inhibitory effects on bacterial growth and biofilm formation were proved against five biofilm-producing reference strains. The biocompatibility tests by using mesenchymal stem cells derived from human bone indicate an excellent biocompatibility.

Silver-hydroxyapatite nanocomposites as bactericidal and fungicidal materials

Abstract Silver-hydroxyapatite nanocomposites containing 1 wt.% of metallic silver have been obtained by a colloidal chemical route and subsequent chemical reduction process. The silver nanoparticles are supported on the hydroxyapatite surface without a high degree of agglomeration. The bactericidal effect against common Gram-positive and Gram-negative bacteria, as well as antifungal activity against yeast have been investigated. The results indicated a high antimicrobial activity for E. coli, M. Luteus and I. Orientalis, so this material can be a promising antimicrobial biomaterial for implant and reconstructive surgery, among other applications.

Inhibitory Effect on In Vitro Streptococcus oralis Biofilm of a Soda-Lime Glass Containing Silver Nanoparticles Coating on Titanium Alloy

This paper reports the effect of soda-lime-glass-nAg coating on the viability of an in vitro biofilm of Streptococcus oralis. Three strains (ATCC 35037 and two clinical isolates from periodontitis patients) were grown on coated with glass, glass containing silver nanoparticles, and uncoated titanium alloy disks. Two different methods were used to quantify biofilm formation abilities: crystal violet staining and determination of viable counts. The influence of the surface morphology on the cell attachment was studied. The surface morphology was characterized by scanning electron microscopy (SEM) and using a profilometer. SEM was also used to study the formation and the development of biofilm on the coated and uncoated disks. At least a >99.7% inocula reduction of biofilm respect to titanium disks and also to glass coated disks was observed in the glass-nAg coated disks for all the studied strains. A quantitative evaluation of the release of silver was conducted in vitro to test whether and to what extend the biocidal agent (silver) could leach from the coating. These findings suggest that the biofilm formation of S. oralis strains is highly inhibited by the glass-nAg and may be useful for materials which require durable antibacterial effect on their surfaces, as it is the case of dental implants.

Evaluation in a Dog Model of Three Antimicrobial Glassy Coatings: Prevention of Bone Loss around Implants and Microbial Assessments

Objectives The aim of the present study is to evaluate, in a ligature-induced peri-implantitis model, the efficacy of three antimicrobial glassy coatings in the prevention of biofilm formation, intrasulcular bacterial growth and the resulting peri-implant bone loss. Methods Mandibular premolars were bilaterally extracted from five beagle dogs. Four dental implants were inserted on each hemiarch. Eight weeks after, one control zirconia abutment and three with different bactericidal coatings (G1n-Ag, ZnO35, G3) were connected. After a plaque control period, bacterial accumulation was allowed and biofilm formation on abutments was observed by Scanning Electron Microscopy (SEM). Peri-implantitis was induced by cotton ligatures. Microbial samples and peri-implant crestal bone levels of all implant sites were obtained before, during and after the breakdown period. Results During experimental induce peri-implantitis: colony forming units counts from intrasulcular microbial samples at implants with G1n-Ag coated abutment remained close to the basal inoculum; G3 and ZnO35 coatings showed similar low counts; and anaerobic bacterias counts at control abutments exhibited a logarithmic increase by more than 2. Bone loss during passive breakdown period was no statistically significant. Additional bone loss occurred during ligature-induce breakdown: 0.71 (SD 0.48) at G3 coating, 0.57 (SD 0.36) at ZnO35 coating, 0.74 (SD 0.47) at G1n-Ag coating, and 1.29 (SD 0.45) at control abutments; and statistically significant differences (p<0.001) were found. The lowest bone loss at the end of the experiment was exhibited by implants dressing G3 coated abutments (mean 2.1; SD 0.42). Significance Antimicrobial glassy coatings could be a useful tool to ward off, diminish or delay peri-implantitis progression.

Histological response of soda-lime glass-ceramic bactericidal rods implanted in the jaws of beagle dogs

Bacterial and fungal infections remain a major clinical challenge. Implant infections very often require complicated revision procedures that are troublesome to patients and costly to the healthcare system. Innovative approaches to tackle infections are urgently needed. We investigated the histological response of novel free P2O5 glass-ceramic rods implanted in the jaws of beagle dogs. Due to the particular percolated morphology of this glass-ceramic, the dissolution of the rods in the animal body environment and the immature bone formation during the fourth months of implantation maintained the integrity of the glass-ceramic rod. No clinical signs of inflammation took place in any of the beagle dogs during the four months of implantation. This new glass-ceramic biomaterial with inherent bactericidal and fungicidal properties can be considered as an appealing candidate for bone tissue engineering.

Antimicrobial activity of submicron glass fibres incorporated as a filler to a dental sealer.

Two types of antimicrobial glass fibers containing ZnO and CaO, with diameters ranging from tens of nanometers to 1 µm, were successfully fabricated by a laser spinning technique. The antimicrobial performance was corroborated according to ISO 20743:2013, by using gram-negative (Escherichia coli) and gram-positive (Streptococcus oralis, Streptococcus mutans and Staphylococcus aureus) bacteria, and yeast (Candida krusei) (more than 3 logs of reduction). The metabolic activity and endosomal system of eukaryotic cells were not altered by using eluents of CaO glass submicrometric fibers and ZnO fibers at 1u2009:u200910 dilution as cellular media (viability rates over 70%). A dental material was functionalized by embedding ZnO nanofibers above the percolation threshold (20% wt), creating a three-dimensional (3D) fiber network that added an antimicrobial profile. This new ZnO glass fiber composite is proved non-cytotoxic and preserved the antimicrobial effect after immersion in human saliva. This is the first time that a fiber-reinforced liner with strong antimicrobial-activity has been created to prevent secondary caries. The potential of developing new fiber-reinforced composites (FRCs) with antimicrobial properties opens up an extensive field of dental applications where most important diseases have an infectious origin.

Effect of the Medium Composition on the Zn2+ Lixiviation and the Antifouling Properties of a Glass with a High ZnO Content

The dissolution of an antimicrobial ZnO-glass in the form of powder and in the form of sintered pellets were studied in water, artificial seawater, biological complex media such as common bacterial/yeast growth media (Luria Bertani (LB), yeast extract, tryptone), and human serum. It has been established that the media containing amino acids and proteins produce a high lixiviation of Zn2+ from the glass due to the ability of zinc and zinc oxide to react with amino acids and proteins to form complex organic compounds. The process of Zn2+ lixiviation from the glass network has been studied by X-ray photoelectron spectroscopy (XPS). From these results we can state that the process of lixiviation of Zn2+ from the glass network is similar to the one observed in sodalime glasses, where Na+ is lixiviated to the media first and the fraction of Zn that acts as modifiers (~2/3) is lixiviated in second place. After the subsequent collapse of the outer surface glass layer (about 200–300 nm thick layer) the dissolution process starts again. Antifouling properties against different bacteria (S. epidermidis, S. aureus, P. aeruginosa, E. coli, and M. lutea) have also been established for the glass pellets.

Influence of dissolution products of a novel Ca-enriched silicate bioactive glass-ceramic on VEGF release from bone marrow stromal cells

Abstract This study evaluated the influence of ionic dissolution products of a novel Ca-enriched silicate bioactive glass compared to commercial available hydroxyapaptite samples (Endobonr) on cell activity and vascular endothelial growth factor (VEGF) release in vitro. Bone marrow stromal cells (ST-2) were cultivated with the supernatant of granules of different sizes and at different concentrations (0-1 wt/vol % of granules) for 48 h. In addition to in vitro studies, Ca-ion release from all as cell morphology observation revealed no cytotoxic effect of the released products from all tested materials. It was found that supernatants from granules in concentrations of 1 wt/vol %enhanced the VEGF release from ST2 cells, which is important as a marker of the vascularisation ability of the glass during the bone healing process.