Facundo Ruiz

The antimicrobial sensitivity of Streptococcus mutans to nanoparticles of silver, zinc oxide, and gold.

Dental caries is a worldwide public health problem for which Streptococcus mutans has been identified as the possible infectious etiology. In recent years nanotechnology has permitted the development of new properties of materials. The objective of this study was to compare the bactericidal and bacteriostatic effects of nanoparticles of silver, zinc oxide, and gold on S. mutans. We used the liquid dilution method to find the minimum inhibitory concentrations (MICs) and with subcultures obtained the minimum bactericidal concentrations (MBCs). For silver the results showed an average MIC of 4.86 +/- 2.71 microg/mL and MBC of 6.25 microg/mL; for zinc the MIC was 500 +/- 306.18 muicrog/mL and MBC of 500 microg/mL; the gold nanoparticles demonstrated an effect only at an initial concentration of 197 mug/mL. We established a higher antimicrobial effect against S. mutans of silver nanoparticles at lower concentrations than gold or zinc, which would allow achieving important clinical effects with a reduced toxicity.

Synthesis, characterization, and evaluation of antimicrobial and cytotoxic effect of silver and titanium nanoparticles

UNLABELLED Microbial resistance represents a challenge for the scientific community to develop new bioactive compounds. Nosocomial infections represent an enormous emerging problem, especially in patients with ambulatory treatment, which requires that they wear medical devices for an extended period of time. In this work, an evaluation of the antimicrobial activity of both silver and titanium nanoparticles was carried out against a panel of selected pathogenic and opportunistic microorganisms, some of them commonly associated with device-associated infections. Cytotoxicity assays monitoring DNA damage and cell viability were evaluated using human-derived monocyte cell lines. We show that silver-coated nanoparticles having a size of 20-25 nm were the most effective among all the nanoparticles assayed against the tested microorganisms. In addition, these nanoparticles showed no significant cytotoxicity, suggesting their use as antimicrobial additives in the process of fabrication of ambulatory and nonambulatory medical devices. FROM THE CLINICAL EDITOR In this study, antimicrobial activity of silver and titanium nanoparticles was evaluated against a panel of selected pathogenic and opportunistic microorganisms. Silver-coated nanoparticles of 20-25 nm size were the most effective among all the nanoparticles without significant cytotoxicity, suggesting their use as antimicrobial additives in the process of fabrication of ambulatory and nonambulatory medical devices.

Antibacterial activity, inflammatory response, coagulation and cytotoxicity effects of silver nanoparticles

The incorporation of nanoparticles (NPs) in industrial and biomedical applications has increased significantly in recent years, yet their hazardous and toxic effects have not been studied extensively. Here, we studied the effects of 24 nm silver NPs (AgNPs) on a panel of bacteria isolated from medical devices used in a hospital intensive care unit. The cytotoxic effects were evaluated in macrophages and the expression of the inflammatory cytokines IL-6, IL-10 and TNF-α were quantified. The effects of NPs on coagulation were tested in vitro in plasma-based assays. We demonstrated that 24 nm AgNPs were effective in suppressing the growth of clinically relevant bacteria with moderate to high levels of antibiotic resistance. The NPs had a moderate inhibitory effect when coagulation was initiated through the intrinsic pathway. However, these NPs are cytotoxic to macrophages and are able to elicit an inflammatory response. Thus, beneficial and potential harmful effects of 24 nm AgNPs on biomedical devices must be weighed in further studies in vivo. From the Clinical Editor: The authors of this study demonstrate that gallic acid reduced 24 nm Ag NPs are effective in suppressing growth of clinically relevant antibiotic resistant bacteria. However, these NPs also exhibit cytotoxic properties to macrophages and may trigger an inflammatory response. Thus, the balance of beneficial and potential harmful effects must be weighed carefully in further studies.

Anti-biofilm activity of silver nanoparticles against different microorganisms

Biofilms confer protection from adverse environmental conditions and can be reservoirs for pathogenic organisms and sources of disease outbreaks, especially in medical devices. The goal of this research was to evaluate the anti-biofilm activities of silver nanoparticles (AgNPs) against several microorganisms of clinical interest. The antimicrobial activity of AgNPs was tested within biofilms generated under static conditions and also under high fluid shears conditions using a bioreactor. A 4-log reduction in the number of colony-forming units of Pseudomonas aeruginosa was recorded under turbulent fluid conditions in the CDC reactor on exposure to 100 mg ml−1 of AgNPs. The antibacterial activity of AgNPs on various microbial strains grown on polycarbonate membranes is reported. In conclusion, AgNPs effectively prevent the formation of biofilms and kill bacteria in established biofilms, which suggests that AgNPs could be used for prevention and treatment of biofilm-related infections. Further research and development are necessary to translate this technology into therapeutic and preventive strategies.

Structure of heat-treated sol-gel SiO 2 glasses containing silver

The crystallization of bulk amorphous SiO 2 samples, prepared by the sol-gel method, was obtained by heat treatments in air at temperatures as low as 500 °C. This occurs when silver is added to the precursor solutions in an amount such that it forms aggregates embedded in the glass. Another requirement to observe the low-temperature glass crystallization is that the bulk samples must be prepared from precursor solutions with specific compositions. These compositions, have a high H 2 O/TEOS ratio, which produces an amorphous SiO 2 structure with some structural similarities to cristobalite, the phase in which the SiO 2 glass crystallizes.

Atomic force microscopy observation of the enamel roughness and depth profile after phosphoric acid etching

The aim was to compare the enamel surface roughness (ESR) and absolute depth profile (ADP) (mean peak-to-valley height) by atomic force microscopy (AFM) before and after using four different phosphoric acids. A total of 160 enamel samples from 40 upper premolars were prepared. The inclusion criterion was that the teeth have healthy enamel. Exclusion criteria included any of the following conditions: facial restorations, caries lesions, enamel hypoplasia and dental fluorosis. Evaluations of the ESR and ADP were carried out by AFM. The Mann-Whitney U-test was used to compare continuous variables and the Wilcoxon test was used to analyze the differences between before and after etching. There were statistically significant differences (P <or= 0.05) among mean surface roughness and absolute depth before and after using four different phosphoric acids in healthy enamel; Etch-37 and Scotchbond Etching Gel showed higher profiles after etching (P <or= 0.05). There were statistically significant differences (P <or= 0.05) among roughness and ADP before and after using four different phosphoric acids in healthy enamel. However, consistently Etch-37 and Scotchbond Etching Gel showed the highest increase regarding the ESR and ADP after etching healthy enamel. AFM was a useful tool to study site-specific structural topography changes in enamel after phosphoric acid etching.

Preparation of (Ni–B)/SiO2, Ni/SiO2 and NiO/SiO2 nanocomposites

Abstract In this work we report composites of nickel–boron (Ni–B)/SiO 2 , Ni 3 B/SiO 2 , Ni/SiO 2 and NiO/SiO 2 . As precursor of the nickel compounds, we used nanometric amorphous Ni–B alloy particles. The nanometric Ni–B particles were prepared by aqueous chemical reduction and studied by transmission electron microscopy (TEM), differential thermal analysis (DTA) and X-ray diffraction (XRD) before their incorporation into the SiO 2 xerogel. The composite samples were prepared by the sol–gel method. The produced samples were ground to form powders, heat treated at different temperatures under atmospheric conditions and characterized by TEM, XRD and DTA techniques. A specific composite (Ni 3 B/SiO 2 , NiO/SiO 2 , Ni/SiO 2 , (Ni–B)/SiO 2 ) can be produced depending on the temperature used for reaction. Composites were stable at room temperature and there were no significant phase transformations under aging.

Antimicrobial activity, cytotoxicity and inflammatory response of novel plastics embedded with silver nanoparticles

AIM Infections associated with medical devices are an important cause of morbidity and mortality. Microorganisms are responsible for catheter infections that may then result in the local or systemic dissemination of the microorganism into the bloodstream. The aim of this study was to evaluate the antimicrobial activity of silver nanoparticles (AgNPs) embedded in polyurethane plastics, commonly used for catheter fabrication. MATERIALS & METHODS AgNPs in the range of 25-30 nm were synthesized and embedded in polyurethane plastics at different concentrations. The antimicrobial activities of these plastics were tested against the three pathogenic microorganisms, Escherichia coli, Staphylococcus epidermidis and Candida albicans, frequently associated with catheter infections. The cytotoxicity of the plastics was evaluated on human-derived macrophages using propidium iodide and the secretion of the pro- and anti-inflammatory cytokines IL-6, IL-10 and TNF-a was measured using ELISA. RESULTS A significant reduction of 6- to 7-log in the number of bacteria was measured, while a reduction of 90% was measured in the case of C. albicans. Neither cytotoxic effect on macrophages nor immunological response was observed. CONCLUSION Plastics embedded with AgNPs have great potential to limit microbial colonization of implanted medical devices.

Antimicrobial Properties of Biofunctionalized Silver Nanoparticles on Clinical Isolates of Streptococcus mutans and Its Serotypes

(1) Background: Streptococcus mutans (S. mutans) is the principal pathogen involved in the formation of dental caries. Other systemic diseases have also been associated with specific S. mutans serotypes (c, e, f, and k). Silver nanoparticles (SNP) have been demonstrated to have good antibacterial effects against S. mutans; therefore, limited studies have evaluated the antimicrobial activity of biofunctionalized SNP on S. mutans serotypes. The purpose of this work was to prepare and characterize coated SNP using two different organic components and to evaluate the antimicrobial activity of SNP in clinical isolates of S. mutans strains and serotypes; (2) Methods: SNP with bovine serum albumin (BSA) or chitosan (CS) coatings were prepared and the physical, chemical and microbiological properties of SNP were evaluated; (3) Results: Both types of coated SNP showed antimicrobial activity against S. mutans bacteria and serotypes. Better inhibition was associated with smaller particles and BSA coatings; however, no significant differences were found between the different serotypes, indicating a similar sensitivity to the coated SNP; (4) Conclusion: This study concludes that BSA and CS coated SNP had good antimicrobial activity against S. mutans strains and the four serotypes, and this study suggest the widespread use of SNP as an antimicrobial agent for the inhibition of S. mutans bacteria.

The effect of ball milling dispersion on the optical properties of organic dyes trapped in silica films by the sol–gel method

Abstract Silicon dioxide coatings containing different types of dyes were prepared using the sol–gel method. It is found that the optical density of the coatings depends on both the dye concentration and on the degree of dye agglomeration. Coatings in which the dye forms aggregates show lower optical density than those in which the dye is better dispersed in the glass matrix. Dispersion of the dye in the starting material is achieved by a ball milling process. A simple model is used to explain the dependence of the optical density on the size of the dye aggregates.