Re-evaluation of erythritol (E 968) as a food additive.

This opinion addresses the re-evaluation of erythritol (E 968) as food additive and an application for its exemption from the laxative warning label requirement as established under Regulation (EU) No 1169/2011. Erythritol is a polyol obtained by fermentation with Moniliella pollinis BC or Moniliella megachiliensis KW3-6, followed by purifications and drying. Erythritol is readily and dose-dependently absorbed in humans and can be metabolised to erythronate to a small extent. Erythritol is then excreted unchanged in the urine. It does not raise concerns regarding genotoxicity. The dataset evaluated consisted of human interventional studies. The Panel considered that erythritol has the potential to cause diarrhoea in humans, which was considered adverse because its potential association with electrolyte and water imbalance. The lower bound of the range of no observed adverse effect levels (NOAELs) for diarrhoea of 0.5 g/kg body weight (bw) was identified as reference point. The Panel considered appropriate to set a numerical acceptable daily intake (ADI) at the level of the reference point. An ADI of 0.5 g/kg bw per day was considered by the Panel to be protective for the immediate laxative effect as well as potential chronic effects, secondary to diarrhoea. The highest mean and 95th percentile chronic exposure was in children (742 mg/kg bw per day) and adolescents (1532 mg/kg bw per day). Acute exposure was maximally 3531 mg/kg bw per meal for children at the 99th percentile. Overall, the Panel considered both dietary exposure assessments an overestimation. The Panel concluded that the exposure estimates for both acute and chronic dietary exposure to erythritol (E 968) were above the ADI, indicating that individuals with high intake may be at risk of experiencing adverse effects after single and repeated exposure. Concerning the new application, the Panel concluded that the available data do not support the proposal for exemption.

Deterioration of direct restorative materials under erosive conditions with impact of abrasion and attrition in vitro.

Objective: To compare the cumulative impact of sequential wear on mechanical properties and appearance of a composite resin (CR), Filtek Z250®, a glass ionomer GI, Fuji IX GP®, and a glass hybrid (GH), Equia Forte®. Material and Methods: Six equally sized specimens of each material were subjected to wear tests, i.e., simulation of brushing, chewing and acidic liquid exposure, mimicking at least 6 months of clinical exposure. Surface roughness, hardness, substance loss and degree of shade lightness were determined. Results: Following wear tests, significant increase in surface roughness and decrease in hardness values were observed for all materials (p < .05). Significantly larger substance loss was found in Equia Forte® specimens compared to Filtek Z250® (p < .05), while that of Fuji IX® exceeded the measurement capacity of the instrument. Opposite to the two other materials, the shade of Filtek Z250® became darker. Conclusions: Sequential wear exposure mimicking abrasion, erosion and attrition to products representing CR, GI and GH, caused weakening and change in appearance of the materials. The composite resin was the most mechanically resistant to the sequential wear.

Re-evaluation of neohesperidine dihydrochalcone (E 959) as a food additive.

The present opinion deals with the re-evaluation of neohesperidine dihydrochalcone (E 959) when used as a food additive. It is obtained by catalytic hydrogenation of a flavanone - neohesperidine - which is naturally occurring and thus isolated by alcohol extraction in bitter oranges (Citrus aurantium). Based on in vivo data in rat, neohesperidine dihydrochalcone is likely to be absorbed, also in humans, and to become systemically available. It does not raise a concern regarding genotoxicity. The toxicity data set consisted of studies on subchronic and prenatal developmental toxicity. No human studies were available. The data set was considered sufficient to derive a new acceptable daily intake (ADI). Based on the weight of evidence (WoE) analysis, the Panel considered unlikely that neohesperidine dihydrochalcone would lead to adverse effects on health in animals in the dose ranges tested. The Panel also considered that a carcinogenicity study was not warranted and that the lack of human data did not affect the overall confidence in the body of evidence. The Panel derived an ADI of 20 mg/kg bodyweight (bw) per day based on a no observed adverse effect level (NOAEL) of 4,000 mg/kg bw per day from a 13-week study in rat, applying the standard default factors of 100 for inter- and intraspecies differences and of 2 for extrapolation from subchronic to chronic exposure. For the refined brand-loyal exposure assessment scenario, considered to be the most appropriate for the risk assessment, the exposure estimates at the mean ranged from < 0.01 to 0.09 mg/kg bw per day and at the 95th percentile (P95) from 0.01 to 0.24 mg/kg bw per day. Considering the derived ADI of 20 mg/kg bw per day, the exposure estimates were below the reference value in all age groups. Therefore, the Panel concluded that dietary exposure to the food additive neohesperidine dihydrochalcone (E 959) at the reported uses and use levels would not raise a safety concern.

Photoactive Zr-aromatic hybrid thin films made by molecular layer deposition.

The principle of antimicrobial photodynamic therapy (PDT) is appealing because it can be controlled by an external light source and possibly the use of durable materials. However, to utilise such surfaces requires a process for their production that allows for coating on even complex geometries. We have therefore explored the ability of the emerging molecular layer deposition (MLD) technique to produce and tune PDT active materials. This study demonstrates how the type of aromatic ligand influences the optical and antimicrobial properties of photoactive Zr-organic hybrid thin films made by MLD. The three aromatic dicarboxylic acids: 2,5-dihydroxy-1,4-benzenedicarboxylic acid, 2-amino-1,4-benzenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid have been combined with ZrCl4 to produce hybrid coatings. The first system has not been previously described by MLD and is therefore more thoroughly investigated using in situ quartz crystal microbalance (QCM), Fourier transform infrared (FTIR) and UV-Vis spectroscopy. The antibacterial phototoxic effects of Zr-organic hybrids have been explored in the Staphylococcus aureus bacteria model using a UVA/blue light source. Films based on the 2,6-naphthalenedicarboxylic acid linker significantly reduced the number of viable bacteria by 99.9%, while no apparent activity was observed for the two other photoactive systems. Our work thus provides evidence that the MLD technique is a suitable tool to produce high-quality novel materials for possible applications in antimicrobial PDT, however it requires a careful selection of aromatic ligands used to construct photoactive materials.

Re-evaluation of thaumatin (E 957) as food additive.

The present opinion deals with the re-evaluation of thaumatin (E 957) when used as a food additive. Thaumatin is a natural plant protein, consisting of thaumatin I and thaumatin II proteins together with minor amounts of plant constituents, obtained by acidic aqueous extraction of the arils of the fruit of Thaumatococcus daniellii plant. The Panel followed the conceptual framework for the risk assessment of certain food additives and considered that thaumatin is a digestible protein; adequate exposure estimates were available; there was no concern with respect to the genotoxicity; no conclusion on oral allergenicity could be drawn from the available human data; no adverse effects were observed in sub-chronic toxicity studies in rats and dogs at the highest dose tested of up 5,200 and 1,476 mg/kg bodyweight (bw) per day, respectively, and in a prenatal developmental toxicity study up to 2,000 mg/kg bw per day; moderate confidence in the body of evidence supported the absence of association between exposure to thaumatin and adverse health outcomes. Therefore, the Panel concluded that there is no need for a numerical acceptable daily intake (ADI) for thaumatin (E 957) and, based on a margin of safety (MOS) of 5,417, considered to be an underestimate and derived using the highest 95th percentile (P95) exposure of 0.48 mg/kg bw per day in consumers only, there is no safety concern for thaumatin (E 957) at the regulatory maximum level exposure assessment scenario, which was considered the most appropriate. The Panel recommended that European Commission considers introducing in the EU specifications for thaumatin (E 957) a new specification limit for the minimum combined content of thaumatin I and II proteins in E 957, a specification limit for yeast, mould counts and Salmonella spp and lowering the existing maximum limit for arsenic along with the inclusion of maximum limits for mercury and cadmium.

Violet-blue light exposure of the skin: is there need for protection?

Advocates of skin protection against blue light express concern about exposure to indoor lighting and electronic screens as well as natural outdoor exposure. However, the nature of adverse effects in skin is unclear and the doses to induce effects are unknown. We aimed to reveal whether there is a scientific basis for promoting skin protection against violet-blue light (400-500 nm, VBL). Based on published literature, we determined the time to reach a threshold dose that induced a biological response in human skin. In the absence of an action spectrum for effects on skin, we used a hand held probe with a defined spectral response and measurements of the unweighted exposure between 400 and 500 nm to estimate the exposure by a selection of artificial light sources and solar light. For comparison, an outdoor threshold erythemally weighted UV dose was set to 1 SED (standard erythema dose). Outdoor, weighted irradiances were obtained using a radiative transfer model. Induction of pigmentation in human skin tissue was the only consistently reported endpoint after VBL exposure of about 65 Jcm-2. This threshold dose was reached in 0.5 to 20 months of exposure to indoor lighting sources. In comparison, specialised medical sources reached this dose in 0.5 min to 45 h. The time outdoors to reach 1 SED was shorter than the time to reach a VBL threshold dose throughout all seasons. Skin protection against VBL is superfluous for exposures to domestic lighting sources or screens and for solar radiation; however, it may be advantageous for patients suffering from photosensitive diseases or taking photosensitising medication.

In vitro abrasivity and chemical properties of charcoal-containing dentifrices.

OBJECTIVE: Charcoal-containing dentifrices are gaining popularity, but scientific information on their effect on oral health is scarce. This study investigated properties of dentifrices that may affect dentine abrasivity, as well as their ability to adsorb fluoride, their pH and the presence of harmful substances. MATERIALS AND METHODS: The dentifrices NAO and COCO were subjected to the following analyses: abrasivity, expressed as mean abraded depth and relative dentin abrasivity (RDA), and surface roughness of extracted human molars (n = 30) after simulated brushing; fluoride adsorption measured as concentration change; pH measurements; detection of polycyclic aromatic hydrocarbons by gas chromatography-mass spectrometry. The products were compared to a reference dentifrice (Colgate® MaxWhite), positive controls (ISO dentifrice slurry, activated charcoal for laboratory use) and a negative control (distilled water). RESULTS: The mean abraded depths of NAO and COCO were not different (p > .05), but higher than the reference dentifrice and the negative control (p < .05). The RDA values of NAO, COCO and the ISO dentifrice slurry were higher than the reference dentifrice value (p < .05) by up to 10 times. The dentine surface roughness was higher after brushing with NAO, COCO and ISO dentifrice slurry compared to distilled water (p < .05). No change in mean adsorbed fluoride concentration was observed after 24 h (p > .05). Both NAO and COCO were alkaline (pH > 7). Analysis of NAO revealed the presence of naphthalene (112.8 ± 2.0 ng/mL). CONCLUSION: The charcoal-containing dentifrices were abrasive within acceptable limits set by ISO and did not adsorb fluoride. The presence of naphthalene in one product is a cause for concern.

Bacterial biofilm elimination using gold nanorod localised surface plasmon resonance generated heat.

Antimicrobial resistance is an increasing global health concern and the world is facing a major challenge to develop novel ways of replacing antibiotics. Gold nanorods exhibit localised surface plasmon resonance upon optical irradiation. During relaxation, absorbed energy is dissipated as heat, which has been utilized to kill bacteria. In this study, 10×45nm gold nanorods were attached to glass surfaces using silanisation. Then biofilms were cultured on the surfaces and studied using microscopy. On average, 71% of the early biofilm bacteria were eliminated after 5min of near infrared radiation (LED emission peak at 850nm) of the gold nanorod coated surfaces, showing the potential of this novel antibiofilm technique. Most notably, the best individual result showed 97% biofilm elimination. This study demonstrates that nanoplasmonic generated heat offers a novel way of eliminating bacterial biofilms. In future applications, this method may be used to eliminate bacterial contamination during implant surgery.

Investigation of the antimicrobial effect of natural deep eutectic solvents (NADES) as solvents in antimicrobial photodynamic therapy.

Natural deep eutectic solvents (NADES) are a third class of liquids, separate from water and lipids. Some NADES, especially those containing organic acids, have been suggested to possess antimicrobial properties. Such properties may be advantageous when NADES are used as solvents in e.g. antimicrobial photodynamic therapy. However, to control the toxicity of acid-containing NADES, they must retain their specific qualities upon dilution. Hence, the aims of this study were to investigate the effect of dilution on the acid-containing NADES network, their antimicrobial activity on different planktonic microorganisms, and their influence on phototoxicity when used as solvents for a photosensitiser. Four bacteria and one fungus were exposed to the NADES, CS (citric acid:sucrose) and MFG (malic acid:fructose:glucose) (molar ratios 1:1 and 1:1:1, respectively), at ≤1:200 dilution. Additionally, the antimicrobial properties of the NADES were studied in Escherichia coli in terms of pH and chelating effects. In investigations of phototoxicity, the microorganisms were exposed to the photosensitiser meso-tetra(p-hydroxyphenyl)porphine (THPP; 1nM) dissolved in diluted NADES combined with blue light (27J/cm2). The eutectic network appeared to remain upon dilution ≤1:200. CS (1:200) was less toxic than an equal concentration of citric acid in the Gram-negative bacteria Klebsiella pneumoniae and E. coli (p<0.05). A higher degree of phototoxicity was induced in E. coli (~1% survival) when THPP was dissolved in CS or MFG than in phosphate buffer (~61% survival; p<0.05). No conclusion could be drawn as to whether the observed toxicity in E. coli exposed to NADES was due to the pH of the solutions or chelation of outer membrane-bound cations.

Physicochemical characterisation and antimicrobial phototoxicity of an anionic porphyrin in natural deep eutectic solvents.

Natural deep eutectic solvents (NADES) are a newly discovered group of eutectics which has shown promise as a solvent in antimicrobial photodynamic therapy (aPDT). The purpose of this study was to investigate preparations of an anionic porphyrin, meso-tetra-(4-carboxyphenyl)-porphine (TCPP), solubilised in NADES, with regard to their physicochemical and antibacterial properties. The NADES CS (pH∼0), ChX (pH∼4) and MFG (pH∼1) solubilised TCPP with absorption maximum ∼443nm and emission maximum ∼678nm, indicating formation of the TCPP dication. Dilution of TCPP-NADES>1:1 (water) reduced the physical stability of the preparations. The photostability half-lives of TCPP in methanol, MFG, and CS were ∼9h, 6.9h and 3.2h, respectively. Nanomolar concentrations of TCPP solubilised in diluted MFG combined with ⩽27J/cm(2) blue light increased Gram-positive and Gram-negative bacterial phototoxicity, >99.98% and 96% bacterial reduction, respectively, compared to TCPP in PBS/ethanol under equivalent treatment conditions. TCPP solubilised in diluted CS was toxic to bacteria both in the absence (36-72% reduction) and presence of light. TCPP in CS, and in the CS component citric acid, induced a TCPP-concentration dependent increase in Gram-negative phototoxicity relative to controls, which was most pronounced for TCPP-CS. The mechanism behind the increased toxicity is unknown.

The dental curing light: A potential health risk.

Powerful blue-light emitting dental curing lights are used in dental offices to photocure resins in the mouth. In addition, many dental personnel use magnification loupes. This study measured the effect of magnification loupes on the "blue light hazard" when the light from a dental curing light was reflected off a human tooth. Loupes with 3.5x magnification (Design for Vision, Carl Zeiss, and Quality Aspirator) and 2.5x magnification (Design for Vision and Quality Aspirator) were placed at the entrance of an integrating sphere connected to a spectrometer (USB 4000, Ocean Optics). A model with human teeth was placed 40 cm away and in line with this sphere. The light guide tip of a broad-spectrum Sapphire Plus (Den-Mat) curing light was positioned at a 45° angle from the facial surface of the central incisor. The spectral radiant power reflected from the teeth was recorded five times with the loupes over the entrance into the sphere. The maximum permissible cumulative exposure times in an 8-hr day were calculated using guidelines set by the ACGIH. It was concluded that at a 40 cm distance, the maximum permissible cumulative daily exposure time to light reflected from the tooth was approximately 11 min without loupes. The weighted blue irradiance values were significantly different for each brand of loupe (Fisher's PLSD p < 0.05) and were up to eight times greater at the pupil than when loupes were not used. However, since the linear dimensions of the resulting images would be 2.5 to 3.5x larger on the retina, the image area was increased by the square of the magnification and the effective blue light hazard was reduced compared to without the loupes. Thus, although using magnification loupes increased the irradiance received at the pupil, the maximum cumulative daily exposure time to reflected light was increased up to 28 min. Further studies are required to determine the ocular hazards of a focused stare when using magnification loupes and the effects of other curing lights used in the dental office.

Characterization and antimicrobial phototoxicity of curcumin dissolved in natural deep eutectic solvents.

Natural deep eutectic solvents (NADES) are a novel class of eutectics which show a unique potential as solubilizer of water insoluble compounds. The purpose of the current study was to evaluate the potential of NADES as a solvent for the hydrophobic photosensitizer curcumin for use in antimicrobial photodynamic therapy (aPDT). Two of the seventeen NADES initially prepared (i.e., NADES GS and MC3) solubilized >0.05mg/ml curcumin and were further characterized. The hydrolytic stability (i.e., t1/2) of curcumin in NADES was comparable to or up to 2-10 times higher than previously reported results in cyclodextrins and up to >1300 times higher than results reported in buffer at pH8. The photolytic stability increased by a factor 5.6-10 in GS compared to the most photostable cyclodextrin and surfactant preparations reported previously. This NADES seemed to lock curcumin in its colorless diketo conformer, resulting in higher photostability than in ethanol and in the NADES MC3. The curcumin-NADES preparations dissolved rapidly in aqueous media and formed supersaturated solutions of curcumin. Precipitation of curcumin was observed after ≤1h depending on the dilution factor (pH<8). The NADES MC3 containing curcumin photoinactivated Escherichia coli at a lower curcumin concentration (1.25µM) than in any previously investigated preparations of curcumin. The ability of NADES to lock curcumin within one specific molecular conformation and also to potentiate the phototoxic effect of this photosensitizer emphasizes the unique properties of the NADES as a solvent.

Improved antibacterial phototoxicity of a neutral porphyrin in natural deep eutectic solvents.

Neutral porphyrins for antibacterial photodynamic therapy (aPDT) have received little attention due to their tendency to aggregate in aqueous media and reports of low phototoxic effect. These compounds may be less toxic to cells than positively and negatively charged photosensitisers. The preparation of highly bacterial phototoxic formulations of neutral porphyrins remains an open field of research with great potential if achievable. The purpose of this study was to develop novel hydrophilic formulations of the neutral porphyrin 5,10,15,20-tetrakis(4-hydroxyphenyl)-porphyrin (THPP) by use of natural deep eutectic solvents (NADES) prepared by the solvent evaporation method. Physical and photochemical stability and in vitro photoinactivation of Enterococcus faecalis and Escherichia coli were investigated. Two of the 15 NADES investigated demonstrated superior solubilising properties of THPP. The photostability of THPP was higher in NADES than in methanol. A 100-fold dilution of the preparations with buffer to a final concentration of 0.5-5 nM THPP resulted in complete photoinactivation of E. faecalis and E. coli both in their exponential and stationary phase. THPP demonstrated significantly higher phototoxicity when formulated in NADES than in other aqueous preparations like phosphate buffered saline. NADES as a formulation concept for photosensitisers shows a great potential in aPDT.

Formulation and characterization of lyophilized curcumin solid dispersions for antimicrobial photodynamic therapy (aPDT): studies on curcumin and curcuminoids LII.

CONTEXT: Bacterial resistance to antibiotics is increasing and alternative antibacterial treatments like antimicrobial photodynamic therapy (aPDT) are needed. Curcumin is under investigation as a potential photosensitizer in aPDT. OBJECTIVE: The purpose of this study was to develop rapidly dissolving formulations of curcumin that could photoinactivate both Gram-positive and Gram-negative bacteria. MATERIALS AND METHODS: Curcumin solid dispersions with methyl-ß-cyclodextrin and hyaluronic acid (HA), hydroxypropyl methylcellulose (HPMC) or both HA and HPMC were prepared through lyophilization. The lyophilizates were characterized by curcumin drug load [% (w/w)], differential scanning calorimetry, photostability, thermal stability, their ability to form supersaturated solutions and by in vitro photoinactivation of Enterococcus faecalis and Escherichia coli. RESULTS AND DISCUSSION: The lyophilizates were amorphous solid dispersions with a curcumin drug load in the range of 1.4-5.5% (w/w) depending on the included polymer and the ratio between curcumin and the cyclodextrin. The lyophilizates were photolabile, but thermally stable and dissolved rapidly in contact with water to form supersaturated solutions. Selected lyophilizates demonstrated >log 6 reduction of colony forming units/ml of both E. faecalis and E. coli after exposure to low curcumin concentrations (0.5-10 µM) and blue light dose (11-16 J/cm(2)). The high drug load of the lyophilizates, rapid dissolution, ability to form relatively stable supersaturated solutions and the very high phototoxicity towards both E. faecalis and E. coli make these lyophilizates suitable for in vivo aPDT. CONCLUSIONS: This treatment with optimized curcumin formulations should be explored as an alternative to topical antibiotics in the treatment of wound infections.

Antibacterial phototoxic effects of synthetic asymmetric and glycosylated curcuminoids in aqueous formulations: studies on curcumin and curcuminoids. LIV.

The aim of this study was to evaluate the in vitro phototoxic potential of synthetic asymmetric and glycosylated curcuminoids on planktonic model bacteria by counting the colony forming units. The Gram-positive Enterococcus faecalis and the Gram-negative Escherichia coli were exposed to aqueous solutions of the curcuminoids (⩽2.5 µM) in the presence or absence of selected pharmaceutical excipients (Pluronic F127, PEG 400 and HPγCD) in combination with a low irradiation dose (5 J/cm(2); λmax: 450 nm) of constant irradiance and time. All the asymmetric curcuminoids, but only one of the glycosylated curcuminoids demonstrated substantial phototoxic effect on E.faecalis (⩾4.7 log reduction). Only two of the asymmetric curcuminoids showed a moderate to low phototoxic effect on the more persistent E.coli. This study emphasized that aromatic hydroxyl substituents in the para-position are important to maintain the phototoxic potential of curcuminoids independent of molecular symmetry. Glycosylation of the aromatic substituents resulted in a substantial loss in phototoxicity towards planktonic bacteria, an apparent change in the non-radiative S1-decay process and a weaker interaction with Pluronic F127 compared to the non-glycosylated curcuminoids. The selected excipients Pluronic F127, PEG 400 and HPγCD strongly influenced the phototoxic potential of the unsymmetrical, non-glycosylated compounds.

Biofilm formation on nanostructured hydroxyapatite-coated titanium.

Biofilm formation on medical devices is a common cause of implant failure, especially regarding implants that breach the epithelial tissue, so-called transcutaneous implants. Nanotechnology and the development of new nanomaterials have given the opportunity to design nanotextured implant surfaces. Such surfaces have been studied using various in vitro methods showing that nanosized features strongly benefit bone cell growth. However, little is known on how nanostructured features affect biofilm formation. The aim of this study was therefore to examine the shape- and chemical-dependent effect of a nanostructured hydroxyapatite (HA) coating on the degree of Staphylococcus epidermidis biofilm formation. Three different types of nanosized HA particles having different shapes and calcium to phosphate ratios were compared to uncoated turned titanium using safranin stain in a biofilm assay and confocal laser scanning microscopy (CLSM) for assessment of biofilm biomass and bacterial volume, respectively. No difference in biofilm biomass was detected for the various surfaces after 6 h incubation with S. epidermidis. Additionally, image analysis of CLSM Z-stacks confirmed the biofilm assay and showed similar results. In conclusion, the difference in nanomorphology and chemical composition of the surface coatings did not influence the adhesion and biofilm formation of S. epidermidis.

Detection of leachables and cytotoxicity after exposure to methacrylate- and epoxy-based root canal sealers in vitro.

Root canal sealing materials may have toxic potential in vitro depending on the cell line, cytotoxicity assay, material chemistry, and degree of polymer curing. The aims of the present study were to detect leaching components from epoxy- or methacrylate-based root canal sealers and to investigate the degree of cytotoxicity after exposure to extracts from these materials. Qualitative determination of substances released from the materials was performed by gas- and liquid chromatography/mass spectrometry. Submandibular salivary gland acinar cell death (apoptosis/necrosis) was determined using a fluorescence staining/microscopy technique. The major leachable monomer from the epoxy-based material was bisphenol-A diglycidyl ether (BADGE), whereas leachables from the methacrylate-based materials were mainly triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), hydroxyethyl methacrylate (HEMA), and polyethyleneglycol dimethacrylate (PEGDMA). Exposure to diluted extracts of cured methacrylate-based materials caused a postexposure time-dependent increase in cell death. This effect was not demonstrated as a result of exposure to undiluted extract of cured epoxy-based material. Extracts of all fresh materials induced apoptosis significantly, but at lower dilutions of the epoxy- than the methacrylate-based materials. The degree of leaching, determined from the relative chromatogram peak heights of eluates from the methacrylate-based sealer materials, corresponded with the degree of cell death induced by extracts of these materials.

Impact of curcumin supersaturation in antibacterial photodynamic therapy--effect of cyclodextrin type and amount: studies on curcumin and curcuminoides XLV.

Curcumin has been investigated as a potential photosensitizer (PS) in antimicrobial photodynamic therapy (aPDT). The phototoxic effect of curcumin is dependent on proper formulations of the compound because of the lipophilic nature of the molecule and the extremely low water solubility at physiological conditions. In the present study, the combination of curcumin with either a methylated ß-cyclodextrin (CD) or polyethylene glycol-based ß-CD or γ-CD polymers was investigated in aPDT using Escherichia coli (E. coli) and Enterococcus faecalis as model bacteria. Solutions with various supersaturation ratios of curcumin were prepared with the selected CD or CD polymers. The concept of supersaturation was then investigated as a mean to enhance the phototoxic effect of curcumin, especially toward the gram-negative bacteria E. coli. A high supersaturation ratio corresponded with high phototoxicity of E. coli. Depending on the curcumin preparation, the bacterial survival ranged from 0.01% to no significant effect after irradiation with blue light (29 J/cm(2) ). Temporal stabilization of the supersaturated state is necessary in order to retain high and predictable photoreactivity of the PS. Further studies will be needed in order to formulate curcumin preparations with acceptable hydrolytic and photolytic stability and a temporal stabilization of a supersaturated state.