Effect of different concentrations of titanium and silver nanoparticles on maxillofacial silicone MDX4-4210 on cell viability, tear bond strength, and shore strength: An in vitro study.

Aim: The aim was to evaluate and compare the cell viability, tear bond strength, and shore hardness of MDX4-4210 silicone reinforced with titanium dioxide and silver nanoparticles in 1%, 2%, and 3%. Settings and Design: The study design involves in vitro comparative study. Materials and Methods: MDX4-4210 silicone incorporated with 1%, 2%, and 3% by weight of silver and titanium dioxide nanoparticles. A total of 112 specimens were prepared and grouped into 7, with 16 specimens in each group. Group 1 - control, Groups 2, 3, and 4 were 1%, 2%, and 3% silver, respectively. Groups 5, 6, and 7 were 1%, 2%, and 3% titanium dioxide nanoparticles, respectively. Cell viability was tested by MTT ASSAY on MG63 cell lines, tear bond strength was tested by peeling force in universal testing machine, and Shore A hardness was tested in durometer. Statistical Analysis Used: The cell viability values were statistically analysed using one-way analysis of variance, and Tukey honestly significant difference test, tear bond strength and shore hardness values were analysed using Mann-Whitney test. Results: Based on the MTT ASSAY test, 1% silver nanoparticles incorporated MDX4-4210 silicone showed maximum cell viability of 42.10%, whereas minimum cell viability was 18.06% for 3% of titanium dioxide-reinforced silicone. The mean value of tear bond strength of 1% silver and 1% titanium dioxide nanoparticles reinforced room temperature vulcanized maxillofacial silicone were 62.81 ± 3.637 N/m and 59.69 ± 5.313 N/m and the mean value of shore hardness of room temperature vulcanized of 1% silver and 1% titanium dioxide nanoparticles reinforced room temperature vulcanized maxillofacial silicone were 38.06 ± 1.237 and 36.75 ± 1.291. Conclusion: Cell viability of 1% silver nanoparticles reinforced MDX4-4210 silicone was higher in comparison to the other groups, and tear bond strength and shore hardness were significantly higher in 1% silver nanoparticles reinforced silicone compared to 1% titanium nanoparticles reinforced MDX4-4210 silicone.

Progress in research on the safety of silicone rubber products in food processing.

Silicone rubber (SR) is widely used in the food processing industry due to its excellent physical and chemical properties. However, due to the differences in SR product production formulas and processes, the quality of commercially available SR products varies greatly, with chemical and biological hazard potentials. Residual chemicals in SR, such as siloxane oligomers and 2,4-dichlorobenzoic acid, are non-intentionally added substances, which may migrate into food during processing so the safe use of SR must be guaranteed. Simultaneously, SR in contact with food is susceptible to pathogenic bacteria growing and biofilm formation, like Cronobacter sakazakii, Staphylococcus aureus, Salmonella enteritidis, and Listeria monocytogenes, posing a food safety risk. Under severe usage scenarios such as high-temperature, high-pressure, microwave, and freezing environments with long-term use, SR products are more prone to aging, and their degradation products may pose potential food safety hazards. Based on the goal of ensuring food quality and safety to the greatest extent possible, this review suggests that enterprises need to prepare high-quality food-contact SR products by optimizing the manufacturing formula and production process, and developing products with antibacterial and antiaging properties. The government departments should establish quality standards for food-contact SR products and conduct effective supervision. Besides, the reusable SR products should be cleaned by consumers immediately after use, and the deteriorated products should be replaced as soon as possible.

Significantly improved antifouling capability of silicone rubber surfaces by covalently bonded acrylated agarose towards biomedical applications.

Bacteria have the extraordinary ability to adhere to biomaterial surfaces and form multicellular structures known as biofilms, which have a detrimental impact on the performance of medical devices. Herein, an investigation highlighted the effective inhibition of bacteria adhesion and overgrowth on silicone rubber surface by grafting polysaccharide, agarose (AG), to construct hydrophilic and negatively charged surfaces. Because of the strong hydration capacity of agarose, the water contact angle of the modified silicone rubber surfaces was significantly reduced from 107.6 ± 2.7° to 19.3 ± 2.6°, which successfully limited bacterial adherence. Most importantly, the durability and stability of coating were observed after 10 days of simulated dynamic microenvironment in vivo, exhibiting a long service life. This modification method did not compromise biocompatibility of silicone rubber, opening a door to new applications for silicone rubber in the field of biomedical materials.

Nitric Oxide-Releasing Silicone Oil with Tunable Payload for Antibacterial Applications.

Bacterial infections are a hurdle to the application of medical devices, and in the United States alone, more than one million infection cases are reported annually from indwelling medical devices. Infections not only affect the function of medical devices but also risk the lives and health of patients. Nitric oxide (NO) has been used as an antibacterial therapy that kills bacteria without causing resistance and provides many therapeutic effects such as anti-inflammation, antithrombosis, and angiogenesis. Silicone oils have been widely utilized in manufacturing consumer goods, healthcare products, and medical products. Specifically, liquid silicone oils are used as a medical lubricant that creates lubricated interfaces between medical devices and the exterior physiological environment to improve the performance of medical devices. Herein, we report the first primary S-nitrosothiol-based NO-releasing silicone oil (RSNO-Si) that exhibits proactive antibacterial effects. S-nitrosothiol silicone oils (RSNO-Si) were synthesized and the NO payloads ranged from 34.0 to 603.9 µM. The increased NO payload induced higher-viscosity RSNO-Si oils, as RSNO0.1-Si, RSNO0.5-Si, and RSNO1-Si had viscosities of 12.8 ± 0.1 cP, 32.0 ± 0.2 cP, and 35.1 ± 0.3 cP, respectively. RSNO-Si-SR interfaces were fabricated by infusing silicone rubber (SR) in RSNO-Si oil, and the resulting RSNO-Si-SR disks demonstrated NO release without NO donor leaching. RSNO0.1-Si-SR, RSNO0.5-Si-SR, and RSNO1-Si-SR exhibited maximum NO flux at 0.8, 6.5, and 21.5 × 10 -10 mol cm-2 min-1 in 24 h, respectively. RSNO-Si-SR disks also demonstrated 97.45, 95.40, and 96.08% of inhibition against S. aureus in a 4 h bacterial adhesion assay. Considering the easy synthesis, simple fabrication of non-leaching NO-releasing interfaces, tunable payloads, NO flux levels, and antimicrobial effects, RSNO-Si oils exhibited their potential use as platform chemicals for creating antimicrobial medical device surfaces and other antibacterial materials.

In vitro Inhibition of Biofilm Formation on Silicon Rubber Voice Prosthesis: Α Systematic Review and Meta-Analysis.

INTRODUCTION: Biofilm formation on voice prostheses is the primary reason for their premature implant dysfunction. Multiple strategies have been proposed over the last decades to achieve inhibition of biofilm formation on these devices. The purpose of this study was to assess the results of the available in vitro biofilm inhibition modalities on silicone rubber voice prostheses. METHODS: We conducted a systematic search in PubMed, Embase, and the Cochrane Central Register of Controlled Trials databases up to February 29, 2020. A total of 33 in vitro laboratory studies investigating the efficacy of different coating methods against Candida, Staphylococcus, Streptococcus, Lactobacilli, and Rothia biofilm growth on silicone rubber medical devices were included. Subgroup analysis linked to the type of prevention modality was carried out, and quality assessment was performed with the use of the modified CONSORT tool. RESULTS: Data from 33 studies were included in qualitative analysis, of which 12 qualified for quantitative analysis. For yeast biofilm formation assessment, there was a statistically significant difference in favor of the intervention group (standardized mean difference [SMD] = -1.20; 95% confidence interval [CI] [-1.73, -0.66]; p < 0.0001). Subgroup analysis showed that combined methods (active and passive surface modification) are the most effective for biofilm inhibition in yeast (SMD = -2.53; 95% CI [-4.02, -1.03]; p = 0.00001). No statistically significant differences between intervention and control groups were shown for bacterial biofilm inhibition (SMD = -0.09; 95% CI [-0.68, 0.46]; p = 0.65), and the results from the subgroup analysis found no notable differences between the surface modification methods. After analyzing data on polymicrobial biofilms, a statistically significant difference in favor of prevention methods in comparison with the control group was detected (SMD = -2.59; 95% CI [-7.48, 2.31]; p = 0.30). CONCLUSIONS: The meta-analysis on biofilm inhibition demonstrated significant differences in favor of yeast biofilm inhibition compared to bacteria. A stronger inhibition with the application of passive or combined active and passive surface modification techniques was reported.

Endothelialized silicone aneurysm models for in vitro evaluation of flow diverters.

OBJECTIVE: The goal of this work was to endothelialize silicone aneurysm tubes for use as in vitro models for evaluating endothelial cell interactions with neurovascular devices. The first objective was to establish consistent and confluent endothelial cell linings and to evaluate the silicone vessels over time. The second objective was to use these silicone vessels for flow diverter implantation and assessment. METHODS: Silicone aneurysm tubes were coated with fibronectin and placed into individual bioreactor systems. Human umbilical vein endothelial cells were deposited within tubes to create silicone vessels, then cultivated on a peristaltic pump and harvested at 2, 5, 7, or 10 days to evaluate the endothelial cell lining. A subset of silicone aneurysm vessels was used for flow diverter implantation, and evaluated for cell coverage over device struts at 3 or 7 days after deployment. RESULTS: Silicone vessels maintained confluent, PECAM-1 (platelet endothelial cell adhesion molecule 1) positive endothelial cell linings over time. These vessels facilitated and withstood flow diverter implantation, with robust cell linings disclosed after device deployment. Additionally, the endothelial cells responded to implanted devices through coverage of the flow diverter struts with increased cell coverage over the aneurysm seen at 7 days after deployment as compared with 3 days. CONCLUSIONS: Silicone aneurysm models can be endothelialized and successfully maintained in vitro over time. Furthermore, these silicone vessels can be used for flow diverter implantation and assessment.

Medical-Grade Silicone Coated with Rhamnolipid R89 Is Effective against Staphylococcus spp. Biofilms.

Staphylococcus aureus and Staphylococcus epidermidis are considered two of the most important pathogens, and their biofilms frequently cause device-associated infections. Microbial biosurfactants recently emerged as a new generation of anti-adhesive and anti-biofilm agents for coating implantable devices to preserve biocompatibility. In this study, R89 biosurfactant (R89BS) was evaluated as an anti-biofilm coating on medical-grade silicone. R89BS is composed of homologues of the mono- (75%) and di-rhamnolipid (25%) families, as evidenced by mass spectrometry analysis. The antimicrobial activity against Staphylococcus spp. planktonic and sessile cells was evaluated by microdilution and metabolic activity assays. R89BS inhibited S. aureus and S. epidermidis growth with minimal inhibitory concentrations (MIC99) of 0.06 and 0.12 mg/mL, respectively and dispersed their pre-formed biofilms up to 93%. Silicone elastomeric discs (SEDs) coated by R89BS simple adsorption significantly counteracted Staphylococcus spp. biofilm formation, in terms of both built-up biomass (up to 60% inhibition at 72 h) and cell metabolic activity (up to 68% inhibition at 72 h). SEM analysis revealed significant inhibition of the amount of biofilm-covered surface. No cytotoxic effect on eukaryotic cells was detected at concentrations up to 0.2 mg/mL. R89BS-coated SEDs satisfy biocompatibility requirements for leaching products. Results indicate that rhamnolipid coatings are effective anti-biofilm treatments and represent a promising strategy for the prevention of infection associated with implantable devices.

Antifertility effectiveness of a novel polymer matrix composite and its influence on the endometrium in rhesus macaques (Macaca mulatta).

OBJECTIVE(S): To explored the antifertility effectiveness and influence on the endometrium of a micro-copper/low-density polyethylene/methyl vinyl silicone rubber (Cu/LDPE/MVQ) composite in rhesus macaques. STUDY DESIGN: Healthy reproductive aged female rhesus macaques underwent abdominal hysterotomy for surgical placement of either the experimental Cu/LDPE/MVQ composite (Cu/LDPE/MVQ, n=5), bare copper wire (Cu, n=5), or hysterotomy only sham-operation group [(SOI, n=4), (SOII, n=6)]. Females in the Cu/LPDE/MVQ, Cu, and SOI groups were housed with fertile males for approximately three menstrual cycles. We assessed pregnancy by hysterectomy. Females in the Cu/LDPE/MVQ, Cu, and SOII groups underwent hysterectomy at about 4 months post-insertion for histologic assessment of morphologic changes of the endometrium, evaluation of materials using scanning electron microscopy (SEM), and evaluation of the inflammatory markers, including substance P receptor (SPR), associated with endometrial bleeding using enzyme linked immunosorbent assay, quantitative RT-PCR, and Western blot analyses. RESULTS: All of the SOI group females became pregnant (4/4, 100%). In contrast, no pregnancies occurred in either the Cu/LDPE/MVQ (0/5, 0%) or Cu (0/5, 0%) groups. We observed histologic features consistent with chronic endometrial inflammation in all females of the Cu group, but none of the SOII or Cu/LDPE/MVQ animals. Levels of inflammatory markers were significantly increased in the Cu group, compared with SOII or Cu/LDPE/MVQ groups (p<.05). SEM showed evidence of corrosion in the Cu wire not seen in the Cu/LDPE/MVQ group. CONCLUSION(S): Cu/LDPE/MVQ material provided a contraceptive effect similar to Cu in macaques, with a lower impact on inflammation and inflammatory markers of the endometrium. IMPLICATIONS: This study demonstrates the possibility of a Cu/LDPE/MVQ composite as an alternative to conventional copper device materials.

Two-Dimensional X-Ray Angiography to Examine Fine Vascular Structure Using a Silicone Rubber Injection Compound.

Angiography is an essential tool for the study of vascular structures in various research fields. The aim of this study is to introduce a simple angiographic method for examining the fine vascular structure of unfixed, fresh tissue using a silicone rubber injection compound and soft tissue X-ray system. This study is especially focused on flap territories used in reconstructive surgery. This study employs angiography with a silicone rubber injection compound in various experimental conditions using Sprague-Dawley rats. First, 15 mL of MV compound and 15 mL of diluent is mixed. Then, 1.5 mL of the curing agent is prepared, and a 24G catheter is cannulated in the common carotid artery of the rat. A three-way stopcock is then connected to a catheter, and the radiopaque agent, after being mixed with the prepared curing agent, is injected immediately without spillage. Finally, as the agent solidifies, the specimen is harvested, and an angiographic image is obtained using a soft tissue X-ray system. This method indicates that high-quality angiography showing fine vascular structures can be easily and simply obtained within in a short period of time.

Modification of silicone elastomers with Bioglass 45S5® increases in ovo tissue biointegration.

Silicone is an important material family used for various medical implants. It is biocompatible, but its bioinertness prevents cell attachment, and thus tissue biointegration of silicone implants. This often results in constrictive fibrosis and implant failure. Bioglass 45S5® (BG) could be a suitable material to alter the properties of silicone, render it bioactive and improve tissue integration. Therefore, BG micro- or nanoparticles were blended into medical-grade silicone and 2D as well as 3D structures of the resulting composites were analyzed in ovo by a chick chorioallantoic membrane (CAM) assay. The biomechanical properties of the composites were measured and the bioactivity of the composites was verified in simulated body fluid. The bioactivity of BG-containing composites was confirmed visually by the formation of hydroxyapatite through scanning electron microscopy as well as by infrared spectroscopy. BG stiffens as prepared non-porous composites by 13% and 36% for micro- and nanocomposites respectively. In particular, after implantation for 7 days, the Young's modulus had increased significantly from 1.20 ± 0.01 to 1.57 ± 0.03 MPa for microcomposites and 1.44 ± 0.03 to 1.69 ± 0.29 MPa to for nanocpmosites. Still, the materials remain highly elastic and are comparably soft. The incorporation of BG into silicone overcame the bioinertness of the pure polymer. Although the overall tissue integration was weak, it was significantly improved for BG-containing porous silicones (+72% for microcomposites) and even further enhanced for composites containing nanoparticles (+94%). These findings make BG a suitable material to improve silicone implant properties. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1180-1188, 2019.

Antifertility effectiveness of a novel copper-containing intrauterine device material and its influence on the endometrial environment in rats.

This study was designed to investigate the antifertility effectiveness of a novel copper-containing intrauterine device material containing a composite of micro-copper (Cu), low-density polyethylene (LDPE), and methyl vinyl silicone rubber (MVQ) and its effects on the endometrial environment in rats. The contraceptive effectiveness was examined 12 days after pregnancy. The pathological changes; factors associated with bleeding, pain, and inflammation in the endometrium; and the surface condition of the implants were investigated after insertion for 90 days. Furthermore, the release rate of copper ions in simulated uterine solution (SUS) was investigated for 270 days. The contraceptive effectiveness was 100% in both the bulk Cu and micro-Cu/LDPE/MVQ groups, and that in the LDPE/MVQ group was 30%. On day 90 after insertion, histopathological observation and the ultrastructural changes in the endometrium showed that the damage caused by bulk Cu was much more severe than that caused by the Cu/LDPE/MVQ microcomposite and that the surface of the latter was much smoother than that of the former. Furthermore, compared with the sham-operated control group, the concentrations of tissue plasminogen activator and prostaglandin E2 were significantly increased 90 days after insertion in all of the experimental groups except for the LDPE/MVQ group (P < 0.05), and the parameters in the Cu/LDPE/MVQ group were significantly lower than those in the Cu group (P < 0.05). In addition, the expression levels of matrix metalloproteinase 9, metalloproteinase 1 tissue inhibitor, plasminogen inhibitor 1, CD34, vascular endothelial growth factor, substance P, and substance P receptor in the endometrium in all of the experimental groups were significantly lower than those in the Cu group 90 days after insertion (P < 0.05). The results of this study indicate that micro-Cu/LDPE/MVQ exhibits satisfactory contraceptive efficacy and causes fewer side effects than Cu.

Novel Proteomic Assay of Breast Implants Reveals Proteins With Significant Binding Differences: Implications for Surface Coating and Biocompatibility.

BACKGROUND: Silicone elastomer, a ubiquitous biomaterial and main constituent of breast implants, has been used for breast augmentation and reconstruction for over 50 years. Breast implants have direct local and purported systemic effects on normal tissue homeostasis dictated by the chemical and physical presence of the implant. OBJECTIVES: Protein adsorption has been demonstrated to be a key driver of local reactions to silicone. We sought to develop an assay and identify the proteins that coat implants during breast implantation. METHODS: Wound fluid was salvaged from women who had undergone breast reduction and incubated in contact with the surface of 13 commercially available implant surfaces. An in situ digestion technique was optimized to elute bound proteins. Samples were analyzed on an Orbitrap elite analyser, proteins identified in Mascot Demon and analyzed in Progenesis. RESULTS: A total of 822 proteins were identified, bound to the surfaces of the implants. Extracellular proteins were the most abundant ontology, followed by intracellular proteins. Fibrinogen, a proinflammatory protein and Albumin, an anti-inflammatory protein had significant (P < 0.0001) binding differences between the surfaces studied. Complement C3, C5, and factor H were also shown to have significantly different binding affinities for the implants included in the study (P < 0.05). CONCLUSIONS: We have developed a novel assay of breast implant protein binding and demonstrated significant binding affinities for relevant proteins derived from breast tissue wound fluid.

Injectable silicone rubber for ocular implantation after evisceration.

OBJECTIVE: To investigate the usefulness of addition type liquid silicone rubber (ATLSR) as injectable implant after evisceration to maintain the eyeball volume in an animal experiment. METHODS: Twelve adult New Zealand white rabbits were included. One eye of each rabbit was randomly selected for evisceration with the fellow eye as control. ATLSR was injected to fill the eyeball socket after evisceration. In vivo observation and photographs were performed up to 24 weeks post-op. Two rabbits were sacrificed respectively at post-operative week 1, 2, 4, 8, 12 and 24. After enucleation, the vertical, horizontal and sagittal diameters of the experimental eyeballs were measured and compared with the control eyes. Histopathological studies were performed to evaluate signs of inflammation. RESULTS: Cornea remained clear throughout the observation period despite mild epithelial edema and neovascularization. Compared to the control eyes, the experimental eyes were significantly smaller in vertical diameter (17.00±1.17 vs. 17.54±1.11 mm, P<0.001), but larger in sagittal diameter (16.85±1.48 vs. 16.40±1.38 mm, P = 0.008), and had no significant difference in horizontal diameter (17.49±1.53 vs. 17.64±1.21 mm, P = 0.34). Postoperative inflammation was observed at one week after surgery, which peaked at 2-3 weeks, then regressed gradually. At week 12 and week 24, most of the inflammatory cells disappeared with some residual plasma cells and eosinophils. CONCLUSION: Injectable addition type silicon rubber may be a good choice for ocular implantation after evisceration, maintaining eyeball volume and cosmetically satisfactory when compared to the fellow eye. Spontaneous regression of inflammation implied good biocompatibility for at least 24 weeks.

Comparison of in vitro biocompatibility of silicone and polymethyl methacrylate during the curing phase of polymerization.

Adverse events have been reported with acrylic bone cements. However, current test standards for acrylic materials fail to characterize the potentially harmful monomers released during the curing stage. In clinical applications, materials are implanted into the human body during this phase. Silicone may be a safer alternative to acrylic cements. Silicone is used in medical applications for its biocompatibility and stability characteristics. Previously, no study has been completed which compares silicone to acrylic cements. In this study, both materials were injected into the cell medium during the curing process which more accurately reflects clinical use of material. Initially, cell cultures followed ASTM standard F813-07 which fails to capture the effects of monomer released during curing. Subsequently, a modified cell culture method was employed which evaluated cytotoxicity while the materials cured. The objective of this study was to capture toxicity data during curing phase. Thus, the test method employed measured and excluded the impact of the exothermic reaction temperature of polymethyl methacrylate (PMMA) on cell growth. The concentration of PMMA monomer was measured at 1 and 24 h after injecting PMMA into culture plates in a manner consistent with established cell growth methodologies. Our results indicate current in vitro cytotoxicity assays recommended by ASTM standards are unable to reveal the real cytotoxic effect caused by methyl methacrylate monomers during polymerization. Our modified experiment can more accurately illustrate the true nature of the toxicity of materials and improve assay results. In these tests, silicone based elastomeric polymers showed excellent cytocompatibility. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2693-2699, 2018.

Silicone rubber membrane with specific pore size enhances wound regeneration.

A porous structure is critically important for wound dressing or tissue engineering scaffolds. However, the influence of the pore sizes on cell proliferation, tissue regeneration and the underlying mechanism remains unclear. In this study, silicone rubber membranes with different pore sizes were prepared using certain constituents of liquid silicone rubber precursor/liquid paraffin/hexane based on our previous studies. It was found that pore size had a significant impact on cell proliferation and wound healing. The CCK8 analysis revealed that the membrane with a certain pore size (110.47 µm, middle pore membrane, MPM) was suitable for cell proliferation compared with the membranes with other pore sizes (218.03 µm, large pore membrane, LPM; 5.27 µm, small pore membrane, SPM; non-porous membrane, NPM). Further studies demonstrated that the MPM promoted cell proliferation via activating the Wnt/ß-catenin signalling pathway. More importantly, wound healing experiments showed that 7 days post-wounding, the rate of wound healing was 89.25% with the MPM, which was significantly higher than with LPM, SPM or NPM. The in vivo data indicated that wound healing was accelerated by treatment with a silicone rubber membrane with a pore size of 110.47 µm. Our results strongly suggest that different pore structures might affect cell proliferation and wound healing and that a silicone rubber membrane with a specific pore size could potentially be used as a promising wound dressing. Copyright © 2017 John Wiley & Sons, Ltd.

Liquid-infused nitric oxide-releasing (LINORel) silicone for decreased fouling, thrombosis, and infection of medical devices.

Recent reports on liquid-infused materials have shown promise in creating ultra-low fouling surfaces, but are limited in their ability to prevent bacterial proliferation and prevent platelet activation in blood-contacting applications. In this work, a liquid-infused nitric oxide-releasing (LINORel) material is created by incorporating the nitric oxide (NO) donor S-nitroso-acetylpenicillamine (SNAP) and silicone oil in commercial medical grade silicone rubber tubing through a solvent swelling process. This combination provides several key advantages over previous NO-releasing materials, including decreased leaching of NO donor, controlled release of NO, and maintenance of ultra-low fouling property of liquid-infused materials. The LINORel tubing reduces protein adhesion as observed using fluorescence imaging, and platelet adhesion (81.7 ± 2.5%) in vitro over a 2 h period. The LINORel combination greatly reduces bacterial adhesion and biofilm formation of two most common pathogens responsible for hospital acquired infections: gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa (99.3 ± 1.9% and 88.5 ± 3.3% respectively) over a 7-day period in a CDC bioreactor environment. Overall, the LINORel approach provides a synergistic combination of active and passive non-fouling approaches to increase biocompatibility and reduce infection associated with medical devices.

Effect of manufacturing and experimental conditions on the mechanical and surface properties of silicone elastomer scaffolds used in endothelial mechanobiological studies.

BACKGROUND: Mechanobiological studies allow the characterization of cell response to mechanical stresses. Cells need to be supported by a material with properties similar to the physiological environment. Silicone elastomers have been used to produce various in vitro scaffolds of different geometries for endothelial cell studies given its relevant mechanical, optical and surface properties. However, obtaining defined and repeatable properties is a challenge as depending on the different manufacturing and processing steps, mechanical and surface properties may vary significantly between research groups. METHODS: The impact of different manufacturing and processing methods on the mechanical and surface properties was assessed by measuring the Young's modulus and the contact angle. Silicone samples were produced using different curing temperatures and processed with different sterilization techniques and hydrophilization conditions. RESULTS: Different curing temperatures were used to obtain materials of different stiffness with a chosen silicone elastomer, i.e. Sylgard 184®. Sterilization by boiling had a tendency to stiffen samples cured at lower temperatures whereas UV and ethanol did not alter the material properties. Hydrophilization using sulphuric acid allowed to decrease surface hydrophobicity, however this effect was lost over time as hydrophobic recovery occurred. Extended contact with water maintained decreased hydrophobicity up to 7 days. Mechanobiological studies require complete cell coverage of the scaffolds used prior to mechanical stresses exposure. Different concentrations of fibronectin and collagen were used to coat the scaffolds and cell seeding density was varied to optimize cell coverage. CONCLUSION: This study highlights the potential bias introduced by manufacturing and processing conditions needed in the preparation of scaffolds used in mechanobiological studies involving endothelial cells. As manufacturing, processing and cell culture conditions are known to influence cell adhesion and function, they should be more thoroughly assessed by research groups that perform such mechanobiological studies using silicone.

Technical feasibility and tissue reaction after silicone-covered biodegradable magnesium stent insertion in the oesophagus: a primary study in vitro and in vivo.

OBJECTIVES: Determine the feasibility of and tissue response to biodegradable magnesium-silicone stent insertion into the oesophagus of rabbits. METHODS: Mechanical compression-recovery and degradation behaviours of the stents were investigated in vitro. Thirty rabbits were randomly divided into a magnesium-silicone stent group (n = 15) that received stent insertion into the lower 1/3 of the oesophagus under fluoroscopic guidance and a control group (n = 15). Oesophagography was performed at 1, 2 and 4 weeks. Five rabbits in each group were euthanized at each time point for histological examination. RESULTS: Magnesium-silicone stents showed good flexibility and elasticity, and degraded more slowly than bare stents at pH 4.0 and 7.4. All stent insertions were well tolerated. The oesophageal diameters at 1, 2 and 4 weeks were 9.7 ± 0.7, 9.6 ± 0.8 and 9.6 ± 0.5 mm, respectively (vs. 9.2 ± 0.8 mm before intervention; P > 0.05). Stent migration occurred in six rabbits (one at 1 week, one at 2 and four at 4). Microscopy demonstrated dilation of the oesophageal wall within 1 week of insertion. Oesophageal injury and collagen deposition following stent insertion were similar to control (P > 0.05). CONCLUSIONS: Oesophageal magnesium-silicone stent insertion was feasible and provided reliable support for 2 weeks without causing oesophageal injury or collagen deposition. KEY POINTS: • Mg stent provided apparently adequate radial force and silicone membrane reduced magnesium biodegradation • Stent insertion provided good support for at least 2 weeks before biodegradation • Stenting effectively resulted in oesophageal wall remodelling, without demonstrable injury.

Preventing Facial Pressure Ulcers in Acute Respiratory Distress Syndrome (ARDS).

BACKGROUND: In patients with acute lung injury and/or severe acute respiratory distress syndrome (ARDS), prone positioning is a therapeutic intervention to improve oxygenation. Positioning a patient in a prone position increases the risk of medical device-related pressure ulcers in the facial area. CASE STUDIES: This article summarizes experience with 4 patients with ARDS. Two did not receive pressure ulcer preventive measures and subsequently developed multiple necrotic facial pressure ulcers related to prone positioning for treatment of ARDS. The other 2 patients were managed on a thin silicone foam dressing; neither of these patients developed facial pressure ulcers during pronation therapy. CONCLUSION: The use of thin soft silicone foam dressings may prevent the development of facial deep tissue injuries in patients receiving prolonged pronation therapy.