Antibiofilm activity of an EDTA-containing nanoemulsion on multidrug-resistant Acinetobacter baumannii.

Acinetobacter baumannii have evolved as an exceedingly troublesome pathogenic microorganisms and prevention and controlling this pathogen is considered to be a public health problem. Nanoemulsions (NE) are a distinctive type of decontaminator produced by integration of immiscible oil phase with aqueous phase under extreme shear forces. The effectiveness of NEs and their components was determined against four stains of A. baumannii by MBC, adherence assay, biofilm assay and SEM studies. NE dilutions ranging from 125 to 225 reduced adhesion by from 61.8 to 99.9% in NE-treated groups (p<.05) as determined by MBC. Four-day-old A. baumannii biofilms were treated with NE; LIVE/DEAD staining showed dead cell intensity of 56.2-92.0% in NE-treated groups. After NE treatment and observation by SEM, cell surfaces appeared to be remarkably disintegrated. Irregular boundaries were observed and margins of cell walls were unclear. The anti-adherence, anti-biofilm and morphological disruption effects of NE suggest that this material could be useful for the development of promising antimicrobial agents.

Antimicrobial activity of nanoemulsion on cariogenic planktonic and biofilm organisms.

INTRODUCTION: Nanoemulsions (NE) are a unique class of disinfectants produced by mixing a water immiscible liquid phase into an aqueous phase under high shear forces. NE have antimicrobial properties and are also effective anti-biofilm agents. MATERIALS AND METHODS: The effectiveness of nanoemulsion and its components was determined against Streptococcus mutans and Lactobacillus casei by live/dead staining. In vitro antimicrobial effectiveness of nanoemulsion against planktonic S. mutans, L. casei, Actinomyces viscosus, Candida albicans and mixed culture was determined by a serial dilution technique to obtain minimum inhibitory concentration and minimum bactericidal concentration (MIC/MBC). In addition, efficacy was investigated by kinetics of killing, adherence and biofilm assays. RESULTS: Compared to its components, nanoemulsion showed notable antimicrobial activity against biofilm organisms, up to 83.0% kill within 1min. NE dilutions ranging from 243 to 19683 were effective against planktonic S. mutans, L. casei, A. viscosus, C. albicans and mixed culture of these four strains as shown through MIC/MBC assays. NE showed antimicrobial activity against planktonic cells at high dilutions, confirmed by time kill studies. The level of adhesion on glass surface was reduced by 94.2-99.5% in nanoemulsion treated groups (p<0.001). 4-Day-old S. mutans, L. casei, A. viscosus, C. albicans and mixed cultures biofilms treated with NE showed reductions of bacterial counts with decreasing dilutions (p<0.001). CONCLUSION: These results suggest that nanoemulsion has effective anti-cariogenic activity against cariogenic microorganisms and may be a useful medication in the prevention of caries.

Antimicrobial activity of nanoemulsion on cariogenic Streptococcus mutans.

OBJECTIVE: To assess antimicrobial activities of nanoemulsion (NE) to control the adhesion and biofilm formation by Streptococcus mutans by in vitro. DESIGN: In vitro antimicrobial susceptibility of nanoemulsion was determined as per National Committee for Clinical Laboratory Standards guidelines and agar diffusion, serial dilution technique for the determination of minimum inhibitory concentration and minimum bactericidal concentration (MIC/MBC). Efficacy was tested by kinetics of killing, biofilm assay and scanning electron microscopy. RESULTS: : NE concentrations ranging from 1:100 to 1:10,000 dilutions were effective against S. mutans as shown through MIC/MBC assays. NE showed antimicrobial activity against planktonic cells at high dilutions, confirmed by time kill studies. 4-day-old S. mutans biofilms were treated with NE; subsequent reductions of bacterial cell counts were noticed with decreasing dilutions. Staining of NE-treated biofilms with LIVE/DEAD BacLight resulted in dead cell areas of up to 48% in 1 min, 84% at 1h and significant (<0.05) increases in dead cell counts at all time points. Damage to cell membranes and cell walls of S. mutans by NE was demonstrated using scanning electron microscopy (SEM). CONCLUSION: These results suggest that nanoemulsion has effective antibacterial activity against S. mutans and may be a useful medication in the prevention of dental caries.

Anti-cariogenic effect of a cetylpyridinium chloride-containing nanoemulsion.

OBJECTIVES: The aim of this pilot study was to investigate the anticaries activity of a nanoemulsion composed of soybean oil, water, Triton X-100 and cetylpyridinium chloride. METHODS: Tooth blocks (3 mm length x 3 mm width x 2 mm thickness) were cut from smooth surfaces of selected molar teeth using a water-cooled diamond wire saw. The blocks were randomly assigned to three experimental groups: (A) nanoemulsion, (B) 0.12% chlorhexidine gluconate, and (C) no treatment. The formation of dental caries in human tooth enamel was tested using a continuous flow dual-organism (Streptococcus mutans and Lactobacillus casei), biofilm model, which acts as an artificial mouth and simulates the biological and physiological activities observed within the oral environment. Experimental groups A and B were treated with their respective solutions once daily for 30 s on each occasion, while group C received no treatment. 10% sucrose was supplied every 6 h for 6 min to simulate meals and pH cycling. The experiment lasted for 5 days, and the tooth blocks were harvested and processed for demineralization assessment using transverse microradiography (TMR). RESULTS: For both lesion depth and mineral loss, statistical analysis indicated that Emulsion was significantly lower than Control and Chlorhexidine, and Chlorhexidine was significantly lower than Control. CONCLUSIONS: We conclude that cetylpyridinium-containing nanoemulsions appear to present a feasible means of preventing the occurrence of early caries.

Rubber-toughening of dimethacrylate dental composite resin.

UNLABELLED: Dimethacrylate dental composite resins exhibit inherently low toughness. Toughening of these materials may reduce the incidence of marginal and bulk fracture of composite restorations. OBJECTIVE: To determine if dimethacrylate dental restorative materials can be rubber-toughened, and if so, to identify a possible mechanism. METHODS: A filler composed of aggregates of polybutadiene/silica as well as irregularly-shaped silica slabs was produced by mixing silica with polybutadiene in dichloromethane. The dried filler was subsequently ground and sieved to < 25 microm. Polybutadiene/silica ratios were varied from 0:1 (control) to 0.5:1. EDAX analysis verified the composition of the complex filler. Filler was added to a bis-GMA/bis-EMA/TEGDMA resin system and fractured in three-point bend test mode at a crosshead speed of 1 mm/min. In addition, 1 bar was fractured at a crosshead speed of 0.001 mm/min to identify a possible mechanism for toughening. RESULTS: In specimens fractured at 1 mm/min, flexural modulus is increased or maintained and flexural strength and energy to break increase as the amount of polybutadiene in the aggregates increases. Cavitation of high-rubber-containing aggregates is demonstrated. In the one specimen fractured at 0.001 mm/min, a marked increase in size of high-rubber-containing aggregates along with severe shear damage in the surrounding matrix is shown, suggesting that cavitation with subsequent absorption of energy during shear yielding is the likely mechanism behind the increase in energy to break in bars fractured at 1 mm/min. SIGNIFICANCE: These results indicate that dimethacrylate dental composite materials can be rubber toughened, which may potentially reduce marginal and bulk fractures of composite restorations, and consequently extend their service lifetime.

Cochlear implants and ex vivo BDNF gene therapy protect spiral ganglion neurons.

Spiral ganglion neurons often degenerate in the deaf ear, compromising the function of cochlear implants. Cochlear implant function can be improved by good preservation of the spiral ganglion neurons, which are the target of electrical stimulation by the implant. Brain derived neurotrophic factor (BDNF) has previously been shown to enhance spiral ganglion survival in experimentally deafened ears. Providing enhanced levels of BDNF in human ears may be accomplished by one of several different methods. The goal of these experiments was to test a modified design of the cochlear implant electrode that includes a coating of fibroblast cells transduced by a viral vector with a BDNF gene insert. To accomplish this type of ex vivo gene transfer, we transduced guinea pig fibroblasts with an adenovirus with a BDNF gene cassette insert, and determined that these cells secreted BDNF. We then attached BDNF-secreting cells to the cochlear implant electrode via an agarose gel, and implanted the electrode in the scala tympani. We determined that the BDNF expressing electrodes were able to preserve significantly more spiral ganglion neurons in the basal turns of the cochlea after 48 days of implantation when compared to control electrodes. This protective effect decreased in the higher cochlear turns. The data demonstrate the feasibility of combining cochlear implant therapy with ex vivo gene transfer for enhancing spiral ganglion neuron survival.

Microcalorimetry of the adsorption of lysozyme onto polymeric substrates.

The conformation of blood proteins adsorbed on biomaterial surfaces probably plays a significant role in the biocompatibility of blood-contacting implants. This paper reports heats of adsorption of a globular protein, lysozyme, onto three uncharged polymeric substrates. Variations in heats among substrates reflect differences in the lysozyme/substrate interaction as well as the possibility of substrate-dependent conformations. In each case, a series of plateaus appeared in the adsorption isotherm with increasing concentration. In the cases of two substrates, polystyrene and poly(styrene-co-butyl methacrylate), endothermic discontinuities appeared at rises between plateaus. It is proposed that the step pattern in each isotherm reflects distinct conformational states of lysozyme on the substrate surfaces. Endothermic discontinuities may be latent heats associated with change to a more stable conformation after initial adsorption. The absence of discontinuities in the case of poly(styrene-co-allyl alcohol) suggests structural transitions occur to a smaller extent on this material and results in conformations different from those which occur when lysozyme is adsorbed by polystyrene or by poly(styrene-co-butyl methacrylate).