Artificial feeding of Ornithodoros rostratus using a silicone membrane system.

The in vitro feeding of ticks facilitates the conduction of studies involving the intrinsic vector-pathogen relationship, susceptibility tests, and resistance to acaricides, in addition to mimicking the use of experimental hosts. The objective of this study was to establish an in vitro feeding system using silicone membranes to supply various diets to the species Ornithodoros rostratus. Each experimental group included 130 first-instar O. rostratus nymphs. The groups were divided according to the diet provided: citrated rabbit blood, citrated bovine blood, bovine blood with antibiotics, and defibrinated bovine blood. The control group was fed directly on rabbits. Ticks were weighed before and after the feeding and monitored individually according to their biological parameters. The results of the experiment demonstrated that the proposed system was efficient in terms of fixation stimulus and satisfactory in terms of tick engorgement, which would allow the maintenance of O. rostratus colonies by using artificial feeding through silicone membranes. All diets provided were efficient for the maintenance of colonies, but the ticks that received citrated rabbit blood displayed similar biological parameters to those observed under in vivo feeding conditions.

In vitro feeding of Hyalomma excavatum and Hyalomma marginatum tick species.

The rearing of ticks is an important technique for studies aiming to elucidate the course and pathogenesis of tick-borne diseases (TBDs). TBDs caused by protozoans (Theileria, Babesia) and bacteria (Anaplasma/Ehrlichia) impose a serious constraint upon livestock health and production in tropical and sub-tropical regions where the distributions of host, pathogen, and vector overlap. This study focuses on Hyalomma marginatum, one of the most important Hyalomma species in the Mediterranean region, being a vector of the virus that causes Crimean-Congo haemorrhagic fever in humans, together with H. excavatum, a vector of Theileria annulata, an important protozoan of cattle. The adaptation of ticks to feeding on artificial membranes allows the creation of model systems that can be put to use examining the underlying mechanisms of pathogen transmission by ticks. Silicone membranes, in particular, offer researchers the flexibility to adjust membrane thickness and content during artificial feeding. The aim of the present study was to develop an artificial feeding technique using silicone-based membranes for all developmental stages of H. excavatum and H. marginatum ticks. Attachment rates after feeding on silicone membranes for females H. marginatum and H. excavatum were 8.33% (8/96) and 7.95% (7/88), respectively. The use of cow hair as a stimulant increased the attachment rate of H. marginatum adults in comparison to other stimulants. The engorgement of H. marginatum and H. excavatum females took 20.5 and 23 days with average weights of 307.85 and 260.64 mg, respectively. Although both tick species could complete egg-laying, and this was followed by hatching of larvae; their larvae and nymphs could not be fed artificially. Taken together, the results of the present study clearly indicate that silicone membranes are suitable for feeding of H. excavatum and H. marginatum adult ticks, supporting engorgement, laying of eggs, and hatching of the larvae. They thus represent a versatile tool for studying transmission mechanisms of tick-borne pathogens. Further studies are warranted to examine attachment and feeding behaviours in order to increase the success of artificial feeding of larvae and nymphal stages.

Effects of Physicochemical Properties of Constituent Ions of Ionic Liquid on Its Permeation through a Silicone Membrane.

Ionic liquids (ILs), defined as liquid salts composed of anions and cations, have the advantage of allowing constituent ions to be stably absorbed through biological membranes, such as skin. However, limited information is currently available on the effects of the physicochemical properties of constituent ions on the membrane permeation of ILs. Therefore, we herein investigated the effects of the polarity of constituent cations on the membrane permeation of each constituent ion from IL. Various ILs were prepared by selecting lidocaine (LID) as a cation and a series of p-alkylbenzoic acids with different n-octanol/water partition coefficients (Ko/w) as anions. These ILs were applied to a skin model, a silicone membrane, and membrane permeability was investigated. The membrane permeabilities of p-alkylbenzoic acids from their single aqueous suspensions were also measured for comparison. The membrane permeability of p-alkylbenzoic acid from the aqueous suspension increased at higher Ko/w. However, the membrane permeability of ILs was similar regardless of the Ko/w of the constituent p-alkylbenzoic acid. Furthermore, the membrane permeability of the counterion LID remained unchanged regardless of the constituent p-alkylbenzoic acid. These results suggest that even when the Ko/w of IL constituents markedly differs, the resulting IL does not affect membrane permeability.

Sulfide-oxidizing bacteria establishment in an innovative microaerobic reactor with an internal silicone membrane for sulfur recovery from wastewater.

A novel bioreactor, employing a silicone membrane for microaeration, was studied for partial sulfide oxidation to elemental sulfur. The objective of this study was to assess the feasibility of using an internal silicone membrane reactor (ISMR) to treat dissolved sulfide and to characterize its microbial community. The ISMR is an effective system to eliminate sulfide produced in anaerobic reactors. Sulfide removal efficiencies reached 96 % in a combined anaerobic/microaerobic reactor and significant sulfate production did not occur. The oxygen transfer was strongly influenced by air pressure and flow. Pyrosequencing analysis indicated various sulfide-oxidizing bacteria (SOB) affiliated to the species Acidithiobacillus thiooxidans, Sulfuricurvum kujiense and Pseudomonas stutzeri attached to the membrane and also indicated similarity between the biomass deposited on the membrane wall and the biomass drawn from the material support, supported the establishment of SOB in an anaerobic sludge under microaerobic conditions. Furthermore, these results showed that the reactor configuration can develop SOB under microaerobic conditions and can improve and reestablish the sulfide conversion to elemental sulfur.

Enhancing shelf life of minimally processed multiplier onion using silicone membrane.

The aim of storage of minimal processed product is to increase the shelf life and thereby extend the period of availability of minimally processed produce. The silicone membrane makes use of the ability of polymer to permit selective passage of gases at different rates according to their physical and chemical properties. Here, the product stored maintains its own atmosphere by the combined effects of respiration process of the commodity and the diffusion rate through the membrane. A study was undertaken to enhance the shelf life of minimally processed multiplier onion with silicone membrane. The respiration activity was recorded at a temperature of 30 ± 2 °C (RH = 60 %) and 5 ± 1 °C (RH = 90 %). The respiration was found to be 23.4, 15.6, 10 mg CO2kg(-1)h(-1) at 5 ± 1 °C and 140, 110, 60 mg CO2kg(-1) h(-1) at 30 ± 2° for the peeled, sliced and diced multiplier onion, respectively. The respiration rate for the fresh multiplier onion was recorded to be 5, 10 mg CO2kg(-1) h(-1) at 5 ± 1 °C and 30 ± 1 ° C, respectively. Based on the shelf life studies and on the sensory evaluation, it was found that only the peeled multiplier onion could be stored. The sliced and diced multiplier onion did not have the required shelf life. The shelf life of the multiplier onion in the peel form could be increased from 4-5 days to 14 days by using the combined effect of silicone membrane (6 cm(2)/kg) and low temperature (5 ± 1 °C).

Antimicrobial Properties of a Copper/Silicone Composite Membrane Prepared Using a Two-Step Immersion Process in Iodine and Copper Sulfate Solutions.

Silicone (polydimethylsiloxane) materials are widely used in various applications. Due to microbe adherence and biofilm formation at the surface of silicone materials, silicone materials must possess antibacterial properties. To achieve this, we prepared copper (Cu)−silicone composite membranes using a simple two-step process of immersion in iodine and copper sulfate solutions. Subsequent scanning electron microscopy revealed Cu nanoparticles (CuNPs) of 10 to 200 nanometers in diameter on the silicone membrane surface, which were identified as copper iodide using energy-dispersive X-ray spectroscopy. The mechanical strength of the material did not change significantly as a result of the two-step immersion treatment and the Cu/silicone membrane showed excellent antibacterial efficacy against Escherichia coli and Staphylococcus aureus, maintaining R > 2 even after a physical impact such as stomacher treatment. Additionally, the Cu ions eluted from the Cu/silicone membrane remained at very low concentrations, suggesting firm immobilization of CuNPs on the silicone membrane. This proposed antimicrobial treatment method does not require special equipment, can be performed at room temperature, and has the potential for use on silicone materials other than membranes.

The Influence of Oily Vehicle Composition and Vehicle-Membrane Interactions on the Diffusion of Model Permeants across Barrier Membranes.

In many instances, one or more components of a pharmaceutical or cosmetic formulation is an oil. The aims of this study were two-fold. First, to examine the potential of preferential uptake of one oily vehicle component over another into a model barrier membrane (silicone) from blended vehicles (comprising two from the common excipients isohexadecane (IHD), hexadecane (HD), isopropyl myristate (IPM), oleic acid (OA) and liquid paraffin). Second, to study the effect of membrane-vehicle interactions on the diffusion of model permeants (caffeine (CF), methyl paraben (MP) and butyl paraben (BP)) from blended vehicles. Selective sorption and partition of some oils (especially IHD and IPM) at the expense of other oils (such as OA) was demonstrated to take place. For example, the membrane composition of IHD was enriched compared to a donor solution of IHD-OA: 41%, 63% and 82% IHD, compared to donor solution composition of 25%, 50% and 75% IHD, respectively. Pre-soaking the membrane in IHD, HD or LP, rather than phosphate buffer, enhanced the flux of MP through the membrane by 2.6, 1.7 and 1.3 times, respectively. The preferential sorption of individual oil components from mixtures altered the barrier properties of silicone membrane, and enhanced the permeation of CF, MP and BP, which are typically co-formulated in topical products.

Introduction of a novel guided bone regeneration memory shape based device.

Bone regeneration by periosteal distraction has been reported in numerous animal studies; however, the main disadvantages of this technique are poor bone quality and soft tissue invasion in the distracted space. The purpose of this study was to evaluate a novel shape memory-based device to promote bone regeneration in a large, secluded growth space in a rabbit model. Twenty rabbits were divided into two groups. In the first group (n = 10), a device composed of silicone sheets and nitinol strips was inserted subperiosteally in the calvarial area. In the second group (n = 10), only silicone sheets were inserted in the calvarial area. Each group was further divided in half: five animals were sacrificed at 8 weeks postoperatively, and the other five were sacrificed at 16 weeks postoperatively. In the study group, the new device vertically expanded the overlying soft tissue 4 mm above the original bone and created a secluded space; the newly generated bone maximum height median ranged between 2.7 mm in 8 weeks group and 2.6 mm in 16 weeks group. In the control group, a very thin rim of bone was generated below the flat silicone sheets on top of the original bone. Maximum bone heights median ranged from 0.37 mm in 8 weeks group to 0.32 mm in 16 weeks group. The device was proven to be effective at vertically augmenting bone by applying the guided bone regeneration and soft tissue expansion procedures simultaneously. This device may pave the way for a new generation of smart guided bone regeneration membranes that can remember the original dimensions of resorbed bone areas.

Silicone-covered biodegradable magnesium stent for treating benign esophageal stricture in a rabbit model.

BACKGROUND: Stent insertion can effective alleviate the symptoms of benign esophageal strictures (BES). Magnesium alloy stents are a good candidate because of biological safety, but show a poor corrosion resistance and a quick loss of mechanical support in vivo. AIM: To test the therapeutic and adverse effects of a silicone-covered magnesium alloy biodegradable esophageal stent. METHODS: Fifteen rabbits underwent silicone-covered biodegradable magnesium stent insertion into the benign esophageal stricture under fluoroscopic guidance (stent group). The wall reconstruction and tissue reaction of stenotic esophagus in the stent group were compared with those of six esophageal stricture models (control group). Esophagography was performed at 1, 2, and 3 weeks. Four, six, and five rabbits in the stent group and two rabbits in the control groups were euthanized, respectively, at each time point for histological examination. RESULTS: All stent insertions were well tolerated. The esophageal diameters at immediately, 1, 2 and 3 wk were 9.8 ± 0.3 mm, 9.7 ± 0.7 mm, 9.4 ± 0.8 mm, and 9.2 ± 0.5 mm, respectively (vs 4.9 ± 0.3 mm before stent insertion; P < 0.05). Magnesium stents migrated in eight rabbits [one at 1 wk (1/15), three at 2 wk (3/11), and four at 3 wk (4/5)]. Esophageal wall remodeling (thinner epithelial and smooth muscle layers) was found significantly thinner in the stent group than in the control group (P < 0.05). Esophageal injury and collagen deposition following stent insertion were similar and did not differ compared to rabbits with esophageal stricture and normal rabbits (P > 0.05). CONCLUSION: Esophageal silicone-covered biodegradable magnesium stent insertion is feasible for BES without causing severe injury or tissue reaction. Our study suggests that insertion of silicone-covered magnesium esophageal stent is a promising approach for treating BES.

Performance of polydimethylsiloxane membrane contactor process for selective hydrogen sulfide removal from biogas.

H2S in biogas affects the co-generation performance adversely by corroding some critical components within the engine and it has to be removed in order to improve the biogas quality. This work presents the use of polydimethylsiloxane (PDMS) membrane contactor for selective removal of H2S from the biogas. Experiments were carried out to evaluate the effects of different pH of absorption liquid, biogas flowrate and temperature on the absorption performances. The results revealed that at the lowest loading rate (91mg H2S/m2·h) more than 98% H2S and 59% CO2 absorption efficiencies were achieved. The CH4 content in the treated gas increased from 60 to 80% with nearly 5% CH4 loss. Increasing the pH (7-10) and loading rate (91-355mg H2S/m2·h) enhanced the H2S absorption capacity, and the maximum H2S/CO2 and H2S/CH4 selectivity factors were 2.5 and 58, respectively. Temperature played a key role in the process and lower temperature was beneficial for intensifying H2S absorption performance. The highest H2S fluxes at pH 10 and 7 were 3.4g/m2·d and 1.8g/m2·d with overall mass transfer coefficients of 6.91×10-6 and 4.99×10-6m/s, respectively. The results showed that moderately high H2S fluxes with low CH4 loss may be achieved by using a robust and cost-effective membrane based absorption process for desulfurization of biogas. A tubular PDMS membrane contactor was tested for the first time to remove H2S from biogas under slightly alkaline conditions and the suggested process could be a promising for real scale applications.

In vitro permeation and disposition of niacinamide in silicone and porcine skin of skin barrier-mimetic formulations.

Niacinamide (NIA) is an amide form of vitamin B3 which is used in cosmetic formulations to improve various skin conditions and it has also been shown to increase stratum corneum thickness following repeated application. In this study, three doses (5, 20 and 50µL per cm2) of two NIA containing oil-in-water skin barrier-mimetic formulations were evaluated in silicone membrane and porcine ear skin and compared with a commercial control formulation. Permeation studies were conducted over 24h in Franz cells and at the end of the experiment membranes were washed and niacinamide was extracted. For the three doses, retention or deposition of NIA was generally higher in porcine skin compared with silicone membrane, consistent with the hydrophilic nature of the active. Despite the control containing a higher amount of active, comparable amounts of NIA were deposited in skin for all formulations for all doses; total skin absorption values (permeation and retention) of NIA were also comparable across all formulations. For infinite (50µL) and finite (5µL) doses the absolute permeation of NIA from the control formulation was significantly higher in porcine skin compared with both test formulations. This likely reflects differences in formulation components and/or presence of skin penetration enhancers in the formulations. Higher permeation for the 50 and 20µL dose was also evident in porcine skin compared with silicone membrane but the opposite is the case for the finite dose. The findings point to the critical importance of dose and occlusion when evaluating topical formulations in vitro and also the likelihood of exaggerated effects of excipients on permeation at infinite and pseudo-finite dose applications.