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The in vitro percutaneous absorption of the essential oil of lemon myrtle (Backhousia citriodora) has been studied in freshly excised human full-thickness abdominal skin obtained from patients undergoing elective surgery. Absorption of lemon myrtle oil in human skin discs (4.9 cm2) was evaluated using a Franz cell diffusion system following topical application of neat lemon myrtle oil (100 μl or 18.29 mg/cm2) to the epidermal surface at exposure durations of 1 to 12 h. Gas chromatography mass spectrometry (GCMS) was used as an analytical technique to determine the absorption of lemon myrtle oil components in full-thickness skin. Citral; (consisting of isomers, geranial and neral) was the only component of lemon myrtle oil found to be absorbing into skin at all exposure periods. At the maximum exposure duration of 12 h, the total absorption of citral in the full-thickness skin disc was 0.29±0.07 mg/cm2 (mean±S.D., n=4) of the applied dose. Although the absorption of lemon myrtle oil components was limited, haematoxylin and eosin (H&E) staining showed significant losses in the cellular functioning of skin including; losses of integrity and solubilisation of the stratum corneum, cellular necrosis (to 15%) and cellular vacuolation (to 25%) on comparison to control skin. When a formulated product containing 1% lemon myrtle oil (0.18 mg/cm2) was applied to human skin discs (4.9 cm2) at 8 h exposure the total absorption of citral in the full-thickness skin disc was 5.12±0.60×10−4 mg/cm2 (mean±S.D., n=4) of the applied dose. No other components were detected. The histopathological assessment indicated limited damage to epidermal cells. The combination of the above methodologies enabled the generation of data that could be used for a comprehensive evaluation of the toxicity effects of lemon myrtle oil for topical application. [Copyright &y& Elsevier]

The antimicrobial and toxicological properties of the Australian essential oil, lemon myrtle, (Backhousia citriodora) were investigated. Lemon myrtle oil was shown to possess significant antimicrobial activity against the organisms Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, methicillin-resistant S. aureus (MRSA), Aspergillus niger, Klebsiella pneumoniae and Propionibacterium acnes comparable to its major component-citral. An in vitro toxicological study based on the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) cytotoxicity assay was performed. In vitro cytotoxicity testing indicated that both lemon myrtle oil and citral had a very toxic effect against human cell lines: HepG2 (a hepatocarcinoma-derived cell line); F1-73 (a fibroblast cell line derived from normal skin) and primary cell cultures of human skin fibroblasts. Cytotoxicity IC50 (50% inhibitory concentration) values ranged from 0.008 to 0.014% (w/v) at 4 h to 0.003–0.012% (w/v) at 24 h of exposure. The no-observed-adverse-effect level (NOAEL) for lemon myrtle oil was calculated as 0.5 mg/l at 24 h exposure and the RfD (reference dose) was determined as 0.01 mg/l. A product containing 1% lemon myrtle oil was found to be low in toxicity and could potentially be used in the formulation of topical antimicrobial products. [ABSTRACT FROM AUTHOR]

Abstract: The influence of low loadings of MnO x on the catalytic activity for n-hexene and CO oxidation over highly dispersed Pt on alumina catalysts has been investigated. The applied deposition–precipitation method allows Mn to be deposited on the Pt containing egg-shell volume. The catalyst samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and selective CO chemisorption. Platinum influences the dispersion of deposited MnO x . The dispersion of the MnO x phase is higher on Pt containing samples than on Al2O3. The Pt decoration by Mn is reflected by a low CO uptake and the Pt oxidation state (Pt2+). The addition of Mn lowers the catalytic activity for CO oxidation. This is attributed to a change of the Pt sites such that adsorption of CO is less favorable. The activity of the catalysts in the oxidation of n-hexane showed a significant improvement with addition of MnO x . A light-off shift by about 40°C was observed. This improvement is attributed to the formation of Mn–Pt oxide like species that primarily weakens the Pt–O bond. [Copyright &y& Elsevier]

Titanium is known for its biocompatibility and is widely used in dental and orthopedic reconstructive surgery. There are reports that osteointegration of these implants is not optimal. The objective of this study was to modify titanium dioxide particles and examine the resultant effects on protein adsorption to these altered surfaces using a model cell binding protein, human plasma fibronectin (HPF). HPF is an important matrix glycoprotein that plays a major role in cell and protein attachment. Titanium dioxide surfaces were modified by heating the titanium dioxide powder at 800°C for 1 h or treating with an oxidizing agent: peroxide in ammonium hydroxide followed by peroxide in hydrochloric acid. Oxidized and control samples were further treated with 9:1 butanol:water for 30 min. Brunauer–Emmett–Teller showed no change in particle surface area as a result of thermal or chemical treatment. Hydrophobicity increased with butanol treatment of titanium dioxide. Diffuse reflectance Fourier transform infrared spectroscopy showed the presence of &z.sbnd;CH2 and &z.sbnd;CH3 vibrations in the region of 2850–3000 cm−1 for both the heated/butanol and peroxide/butanol-treated samples. The absence of increased C&z.sbnd;O and O&z.sbnd;C&z.dbnd6;O features as determined by electron spectroscopy for chemical analysis indicates that butanol adsorption is not occurring via an esterification mechanism. The interaction between butanol and pre-heated or peroxide-treated titanium dioxide may be one of association (weak electrostatic and/or Van der Waals forces) rather than direct ionic bonding. Maximum HPF adsorption on modified or unmodified titanium dioxide occurred within 30 min, with greater protein adsorption occurring on butanol-treated samples. Desorption was minimal with all modifications. Zeta potential measurements showed that HPF adsorption caused an increase in the negative zeta potential with the greatest change noted for the butanol-treated samples. These findings suggest that wettability and surface charge both play an important role in protein adsorption to titanium dioxide. Thus, by modifying the physico-chemical properties of titanium dioxide surfaces, it may be possible to alter protein adsorption and hence optimize cell attachment. [Copyright &y& Elsevier]

Abstract: Fire combustion products contain a broad range of chemicals, which have a multitude of possible toxic interactions in humans. The aim of this study was to evaluate the cytotoxicity of selected substances commonly produced during fire combustion. A range of human cell lines and cultures including: skin fibroblasts, HepG2 (liver derived), and A549 (lung derived cells) were used to represent different human target organs. The colorimetric MTS assay (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) was used to detect the cytotoxic effects of selected substances including: acetic acid, ammonia, formaldehyde, hydrobromic acid, hydrochloric acid, hydrofluoric acid, potassium cyanide, sodium fluoride, sodium nitrite, sodium sulphide, and sulphurous acid. In this study, the NOAEC (No Observable Adverse Effect Concentration), IC10 (10% inhibitory concentration), IC50 (50% inhibitory concentration), and TLC (Total Lethal Concentration) values were determined. The ratio between in vitro IC50 to in vivo human toxicity data (Lowest Lethal Dose-LDLo and Lowest Lethal Concentration––LCLo) was also established. Results indicated a strong relationship between IC50 values on the cell types used: fibroblast and A549 (R 2: 0.92), A549 and HepG2 (R 2: 0.72), fibroblast and HepG2 (R 2: 0.69). Good correlation was obtained between the IC50 against LDLo and LCLo when an appropriate adjustment factor was implemented. Results of this study indicated that in vitro methods could be a potential technique for assessing the toxicity of fire combustion products. [Copyright &y& Elsevier]

The use of biodegradable bone substitutes is advantageous for alveolar ridge augmentation, since it avoids second-site surgery for autograft harvesting. This study examines the effect of novel, rapidly resorbable calcium phosphates on the expression of bone-related genes and proteins by human bone-derived cells (HBDC) and compares this behavior to that of tricalciumphosphate (TCP). Test materials were α-TCP, and four materials which were created from β-Rhenanite and its derivatives: R1-β-Rhenanite (CaNaPO4); R1/M2 composed of CaNaPO4 and MgNaPO4; R1+SiO2 composed of CaNaPO4 and 9% SiO2 (wt%); and R17-Ca2KNa(PO4)2. HBDC were grown on the substrata for 3, 5, 7, 14 and 21 days, counted and probed for various mRNAs and proteins (Type I collagen, osteocalcin, osteopontin, osteonectin, alkaline phosphatase and bone sialoprotein). All substrata supported continuous cellular growth for 21 days. At day 21, surfaces of R1+SiO2 and R17 had the highest number of HBDC. At 14 and 21 days, cells on R1 and on R1+SiO2 displayed significantly enhanced expression of all osteogenic proteins. Since all novel calcium phosphates supported cellular proliferation together with expression of bone-related proteins at least as much as TCP, these ceramics can be regarded as potential bone substitutes. R1 and R1+SiO2 had the most effect on osteoblastic differentiation, thus suggesting that these materials may possess a higher potency to enhance osteogenesis than TCP. [Copyright &y& Elsevier]

Loss of bone near joint prostheses is thought to be caused by activation of recruited osteoclasts by osteolytic mediators induced by wear particles. It is proposed that particles inhibit osteogenesis during bone remodelling causing a reduction in the levels of peri-implant bone. This study explores whether prosthetic particles modulate bone formation by affecting osteoblastic bone-related mRNAs (alkaline phosphatase, pro-collagen Iα1, osteopontin, osteonectin, osteocalcin, bone sialoprotein and thrombospondin) or their translated proteins using titanium alloy, commercially pure titanium, and cobalt–chrome particles. The direct effect of the particles revealed no change to the expression of the bone-related mRNAs in human bone-derived cells (HBDC) at the time points investigated; although non-collagenous translated proteins expressed by these HBDC were significantly effected (p<0.05). Different patterns of expression for bone-related proteins were induced by the different particles both directly and indirectly. Inflammatory mediators (interleukin-1β, tumor necrosis factor α, interleukin-6, and prostaglandin E2) had similar effects on HBDC to the media obtained from monocytes incubated with particles. This study shows that prosthetic wear particles can significantly modify the expression of bone-related proteins by osteogenic cells in vitro. These alterations in osteogenic activity at the interface of the implant and bone may be an important factor in the failure of many orthopaedic implants. [Copyright &y& Elsevier]