Siliconization: Blood - Surface Interaction

Biomaterials, 2004

Medical-grade polydimethylsiloxane elastomer was subjected to low-powered plasma treatment in the presence of four different gases: O 2 , Ar, N 2 and NH 3. Changes to the surface chemistry immediately after processing and the stability of the treatments following ageing in phosphate buffered saline or air for up to 1 month were investigated using X-ray photoelectron spectroscopy and dynamic contact angle analysis. Changes in surface morphology were assessed using optical microscopy and atomic force microscopy. All treatments resulted in an increase in wettability, attributed to major changes in chemistry combined with modest etching. Furthermore, the primary site of attack of the plasma species appeared to be dependent upon the feed gas implemented. The two main chemical changes observed after ageing were due to reactions with the storage media and relaxation processes resulting in further changes in wettability. The influence of the surface modifications on the blood compatibility of the materials was investigated by assessing contact phase activation using a partial thromboplastin time assay. It was demonstrated that the O 2 and Ar plasma treatments reduced the performance of the silicone but the N 2 and NH 3 treatments had a significantly beneficial effect on the activation of the coagulation cascade.

Journal of Pharmaceutical Sciences, 2014

Prefilled syringes (PFSs) offer improvements in the delivery of drugs to patients compared with traditional vial presentations and are becoming necessities in an increasingly competitive biologics market. However, the development of a product in a PFS must take into account potential incompatibilities between the drug and the components of the syringe. One such component is silicone oil, which has previously been suggested to promote protein aggregation, loss of soluble protein, and an increase in the particulate content of injectable formulations. This study evaluated the particulate content in a model buffer system (polysorbate 80/phosphate-buffered saline) after agitation in glass syringes with a novel cross-linked silicone coating. We also evaluated the compatibility of two monoclonal antibodies with these syringes. We report that syringes with this novel coating, compared with standard siliconized syringes, exhibited reduced particle content and enhanced integrity of the lubricant layer as determined by reflectometry, optical microscopy, and time-of-flight secondary ion mass spectrometry measurements, while maintaining the desired functional properties of the syringe and the antibodies' stability profiles as determined by high-performance size-exclusion chromatography. Enhanced integrity of the lubricant coating led to significantly fewer subvisible particles in the liquid formulations, particularly after agitation stresses introduced by shipping of the syringes.

Biomaterials, 2006

Porous silicon is a promising biomaterial that is non-toxic and biodegradable. Surface modification can offer control over the degradation rate and can also impart properties that promote cell adhesion. In this study, we modified the surface of porous silicon surface by ozone oxidation, silanisation or coating with collagen or serum. For each surface, topography was characterised using atomic force microscopy, wettability by water contact angle measurements, degradation in aqueous buffer by interferometric reflectance spectroscopy and surface chemistry by Fourier-transform infrared spectroscopy. The adhesion of rat pheochromocytoma (PC12) and human lens epithelial cells to these surfaces was investigated. Cells were incubated on the surfaces for 4 and 24 h, and adhesion characteristics were determined by using a fluorescent vital stain and cell counts. Collagen coated and amino silanised porous silicon promoted cell attachment for both cell lines whereas cells attached poorly to ozone oxidised and polyethylene glycol silanised surfaces. We showed that the two cell lines had different adhesion characteristics on the various surfaces at different time points. The use of the vitality assays Alamar Blue (redox based assay) and neutral red (active cellular uptake assay) with porous silicon was also investigated. We reveal incompatibilities between certain resazurin (Alamar Blue), lysosomal incorporation assays (neutral red) and porous silicon. r

International Journal of Biomaterials, 2012

Colloids and Surfaces B: Biointerfaces, 2006

Shunt infections are one of the most serious complications in shunt implant surgery. Previous studies have suggested that cerebrospinal fluid (CSF) proteins could affect bacterial adhesion and subsequent shunt infection. A systematic study using immobilized protein on the surface of silane-modified silicone was conducted to determine how these modifications influenced Staphylococcus epidermidis adhesion and colonization. A comparison was also made with silicone having physically adsorbed protein. A colony-counting adhesion assay and scanning electron microscopy (SEM) were used to provide quantitative analysis of bacterial adhesion and semi-quantitative analysis of bacterial colonization, respectively. In order to determine the appropriate silanization process for effective protein immobilization, the effect of bovine serum albumin (BSA) immobilized on n-3-(trimethoxysilyl)propyl-ethylenediamine (AEAPS)/silicone, aminopropyltriethoxysilane (APTMS)/silicone, 3-(glycidyloxypropyl)trimethoxysilane (GPTMS)/silicone, and octadecyltrichlorosilane (OTS)/silicone on bacterial adhesion was investigated. Upon identifying that OTS is the most effective silane, different types of proteins, including: BSA, human serum albumin (HSA), ␥-globulin, and fibrinogen were immobilized on OTS/silicone by a photo-immobilization method. Immobilized protein on modified silicone surfaces was found to be stable in saline for 30 days, while physically adsorbed protein showed instability within hours as determined by contact angle measurements and X-ray photoelectron spectroscopy (XPS). For HSA/OTS/silicone, BSA/OTS/silicone, ␥-globulin/OTS/silicone, fibrinogen/OTS/silicon, and physically absorbed BSA on silicone, the contact angles were 78.5 • , 80.7 • , 78.9 • , 81.3 • , and 96.5 • ; and the amount of nitrogen content was found to be 4.6%, 5.0%, 5.6%, 7.2%, and 3.2%, respectively. All protein immobilized on OTS/silicone surfaces significantly reduced bacterial adhesion by around 75% compared to untreated silicone, while physically adsorbed BSA on silicone reduced by only 29.4%, as determined by colonycounting adhesion assay. However, there was no significant difference on bacterial adhesion among the different types of proteins immobilized on OTS/silicone. Minimizing bacterial adhesion and colonization can be attributed to the increased concentration of -NH 2 group, and stability and more hydrophilic nature of the protein/OTS/silicone surfaces.

Frontiers in Public Health

Synthetic amorphous silica (SAS) is industrially relevant material whose bioactivity in vitro is strongly diminished, for example, by protein binding to the particle surface. Here, we investigated the in vitro bioactivity of fourteen SAS (pyrogenic, precipitated, or colloidal), nine of which were surface-treated with organosilanes, using alveolar macrophages as a highly sensitive test system. Dispersion of the hydrophobic SAS required pre-wetting with ethanol and extensive ultrasonic treatment in the presence of 0.05% BSA (Protocol 1). Hydrophilic SAS was suspended by moderate ultrasonic treatment (Protocol 2) and also by Protocol 1. The suspensions were administered to NR8383 alveolar macrophages under serum-free conditions for 16 h, and the release of LDH, GLU, H2O2, and TNFα was measured in cell culture supernatants. While seven surface-treated hydrophobic SAS exhibited virtually no bioactivity, two materials (AEROSIL® R 504 and AEROSIL® R 816) had minimal effects on NR8383 cells...

Frontiers in Pharmacology

Siloxanes are commonly known as silicones. They belong to the organosilicon compounds and are exclusively obtained by synthesis. Their chemical structure determines a range of physicochemical properties which were recognized as unique. Due to the susceptibility to chemical modifications, ability to create short, long or complex polymer particles, siloxanes found an application in many areas of human life. Siloxanes differ in particle size, molecular weight, shape and chemical groups. As a result, this determines the different physico-chemical properties, that directly affect the safety or the risk of their use. The areas that can be a source of danger to human health will be commented in this paper.

Journal of Biomedical Materials Research Part A, 2008

Silicon wafers modified by silanisation with different functional groups are used to study the bioactivity of surfaces with varying physicochemical properties. Oxidation of the wafers created very hydrophilic surfaces, and moderately wettable surfaces were produced by coating with poly(ethylene glycol) (PEG). Immobilization of hydrocarbon chains to the wafers produced hydrophobic surfaces, and hydrophobicity was further increased by fluorocarbon coatings. The oxidized and the hydrocarbon-modified surfaces supported the adhesion of human MG-63 osteoblasts and 3T3 mouse fibroblasts as well as Staphylococcus aureus 8325-4. Adhesion of osteoblasts and fibroblasts, however, was decreased on highly hydrophobic fluorocarbon surfaces, whereas adhesion of S. aureus was supported. Coating of the fluorocarbon surface with fibronectin increased the number of attached eukaryotic cells, but the accumulation of bacteria remained unchanged. In contrast, surface coatings with PEG-groups inhibited the binding of S. aureus; however, the adhesion of the eukaryotic cells was high. The number of S. aureus on PEG-modified surfaces covered with fibronectin increased about twofold, yet it was still decreased to 25-30% related to the number of bacteria on other surfaces. These findings provide evidence that the PEG-modified surfaces showed selective bioactivity, preventing the attachment of a microbial pathogen but supporting the adhesion of eukaryotic cells.

The Journal of Prosthetic and Implant Dentistry

Introduction: This study aims to evaluate the surface wettability of addition silicone impression materials, which were treated with two different disinfecting agents for two different time intervals. Methods: Twenty-five rectangle-shaped specimens from each of two different addition silicone impression materials (Express GT and Flexceed) were prepared. Five samples from each impression material were kept as the control without any disinfection. The rest of the specimens were divided into two groups according to the disinfecting agents, (2% Glutaraldehyde and 0.5% sodium hypochlorite) and disinfected for two time periods (10 minutes, and 60 minutes). Later, surface wettability was tested and recorded. Data were analyzed with analysis of variance (ANOVA). Results: The mean contact angle values of both impression materials at 10 minutes of disinfection were reduced when compared to the control group (without disinfection). As the disinfection time increases there was a tendency of dec...

Biomaterials, 1999

Self-assembled monolayers of alkylsiloxanes supported on poly(dimethylsiloxane) (PDMS) rubber were used as model systems to study the relation between blood compatibility and surface composition. The inner lumen of PDMS tubes were "rst treated with an oxygen plasma. The resultant oxidized surfaces were post-derivatized by reaction with alkyltrichlorosilanes to form the monolayer "lms. The alkyl chain lengths used were slightly longer than in a previous study, and this may alter the phase-state of the monolayer from liquid-like to crystalline. The chemical properties of the monolayer were controlled by varying the chemical composition of the alkyltrichlorosilanes used. Terminal functionalities included }CH , }CF , }COOH, }SO H and }(CH CH O) OH. Surface derivatization was veri"ed with static contact angle measurements and X-ray photoelectron spectroscopy. Blood compatibility was evaluated using a canine ex vivo arterio-venous series shunt model. Surfaces grafted with hydrophobic head groups such as }CH and }CF were signi"cantly less thrombogenic than the surfaces composed of ionic head groups such as }COOH and }SO H. Surfaces enriched in }(CH CH O) OH had an intermediate thrombogenicity. Silastic pump grade tubing and polyethylene tubing, used as controls, were found to be the least thrombogenic of all the surfaces tested.