Surgical Models of Stroke Induced by Intraluminal Filament Implantation
Yanlin Wang-Fischer in Manual of Stroke Models in Rats, 2008
Silicone elastomers have been employed for many years in the manufacture of medical devices, including device components and tubing. These elastomers are commercially available in two types: millable high-consistency silicone rubber and pumpable liquid silicone rubber. Low-viscosity silicone liquid is 100% polydimethylsiloxanes. It makes liquid silicone rubbers suitable for molding applications. (Silicone rubber can be purchased as Provil-L®, Bayer Dental D-5090, from Leverkusen, Germany, or Dow Corning, Midland, Michigan, or GE Sealant and Adhesives, Huntersville, North Carolina). Monofilament nylon sutures can be purchased from Ethicon, Somerville, New Jersey, or other companies. Here, we describe the method of Koizumi et al.1 and Takano et al. (1997).13
A Novel Approach for Finishing Various Implants
S Santhosh Kumar, Somashekhar S. Hiremath in Role of Surface Modification on Bacterial Adhesion of Bio-Implant Materials, 2020
A viscoelastic polymer commonly used in the development of abrasive media acts as a carrier medium and carries abrasive particles. It has viscous and elastic properties that help in distributing the axial and radial force on the abrasive particles with the help of applied extrusion pressure. Some of the commonly used polymer carriers are polyborosiloxane, silicone rubber, silly putty, natural rubber, styrene butadiene rubber, butyl rubber, etc. In the present investigation, silicone rubber is selected as a viscoelastic polymer media (carrier media) because of its unique properties like wide temperature range (–101°C to 316°C), less cost compared to other synthetic rubbers (Aggarwal, 1987), good thermal conductivity, abrasion resistance, chemical stability (Shit and Shah, 2013), high tear strength and elongation, good processability and not sticky to surfaces, which are the basic requirements for abrasive media. Also, it is one of the most widely used in manufacturing components of aerospace, aviation, medical, semiconductor, and automotive industries. The literature shows that silicone rubber is the best suitable abrasive media, and it has compatibility with a wide range of abrasive particles and is also mechanically stable. The selected type of silicone rubber is Bluesil HCR 1940 LA2, and its physical properties are listed in Table 4.8.
Silicones in Cosmetics
E. Desmond Goddard, James V. Gruber in Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
ties with either temperature or polymer molecular weight as previously stated. This results in the low modulus and glass transition temperatures (low brittle points) exhibited by dimethicone fluids. Also characteristic of polydimethylsiloxanes is a low surface tension at and high spreadability and diffusivity coefficients. Therefore, the unmodified silicone polymers will spread into thin uniform films and are highly permeable to gases such as oxygen, carbon dioxide, and water vapor. This is illustrated in Table 5, where the gas permeability of silicone elastomers is compared to that of several other organic compounds. Replacement of one or more of the methyl groups in polydimethyl-siloxanes by larger aliphatic or aromatic hydrocarbon substituents, however, markedly decreases both the spreading capacity of the fluids and the permeability of the resulting polymers (3).
The development of a silicone vaginal ring with a prostaglandin analogue for potential use in the treatment of canine reproductive disorders
Published in Pharmaceutical Development and Technology, 2019
Veronika Nováková Tkadlečková, Jakub Vysloužil, Kateřina Kubová, Jan Elbl, Darja Bučková, Jan Muselík, David Vetchý, Robert Novotný, Pavel Proks, Josef Jančář, Petr Poláček
To investigate in vitro release behaviour of sparingly soluble model drug CA (Agyemang-Yeboah and Oppong 2013) from the matrix-type VR in the presence of various channel-forming substances for achieving the 72-h in vitro dissolution profile, silicone flat discs containing 100 mg of CA (particle size of 125–250 µm) were prepared from model silicone Sylgard® 164 (two-part silicone elastomer, mixed 1:1). The base of the silicone elastomer was mixed with CA or the mixture of CA and channel-forming excipient. After the addition of the catalyst, the mixture was poured into the cylindrical plastic mould prepared on the Rebel II 3 D printer (diameter 30 mm, height 2.3 mm, approx. weight of discs 2300 mg) and the discs were cured for 15 min at room temperature (the curing time was recommended by the producer). The composition of the flat discs (the set SYL) is shown in Table 1. Each composition was tested for weight uniformity according to Ph. Eur. 9 (the deviation ± 5% was chosen as acceptable and in accordance with the deviation used for vaginal pessaries, which have a comparable weight).
Lipid depletion enables permeation of Staphylococcus aureus bacteria through human stratum corneum
Published in Tissue Barriers, 2020
Zachary W. Lipsky, Cláudia N. H. Marques, Guy K. German
Polydimethylsiloxane (PDMS) silicone elastomer (Sylgard 184, Dow Corning, Midland, MI) was prepared by mixing a 10:1 ratio of base to curing agent by weight. After mixing and degassing, the mixture was spin coated (WS-400B-6NNP/LITE, Laurell Technologies Corporation, North Wales, PA) on to a glass coverslip sequentially at 500, 1000, 1500, 3000, 5000, and 6000 rpm, each for 15 s. This produced a uniform silicone elastomer film 14 μm in thickness. Control and lipid depleted SC samples were alternately embedded in the uncured elastomer along the centerline of the coverslip, leaving only their outermost face exposed. This embedding process occludes the sides and underside of the SC sample, preventing bacterial growth in these regions. Substrates were then placed under vacuum in a vacuum desiccator (5310–0250, Nalgene®, ThermoFisher Scientific, Waltham, MA) with an attached vacuum pump (ME4 NT Vacuubrand, BrandTech, Essex, CT) for 4 hr to eliminate microbubbles between the SC and PDMS. The elastomer was then cured at room temperature and humidity for 48 hr. For each substrate tested, the order of the conditioned SC samples deposited was randomized.
Implantable medical devices for tendon and ligament repair: a review of patents and commercial products
Published in Expert Review of Medical Devices, 2022
Marco Civera, Ester Devietti Goggia, Matteo De Ros, Vito Burgio, Federica Bergamin, Mariana Rodriguez Reinoso, Cecilia Surace
Another key component is silicone. Silicones are highly versatile materials, suitable for various industries and applications, due to their high elasticity, biocompatibility, easy processability and chemical inertness [64]. They are synthetic polymers, commonly obtained in the form of a linear chain made of polydimethylsiloxane (PDMS). Highly crosslinked silicones or gel-like silicones are nowadays used in medical implants. Silicone elastomers are considered as a material of choice for orthopaedic prostheses and finger joints [64]. Nevertheless, they are insufficiently exploited for use inside the human body, especially for long-term implantation of prostheses, valves etc. The risk of rupture of a silicone implant is associated with degradation processes, as a consequence of multiple causes: autoimmune response due to the microorganisms present in the implantpenetration of lipids into the polymer networkmechanical loading during daily activities
Related Knowledge Centers
- Catalysis
- Elastomer
- Oxygen
- Polymer
- Vulcanization
- Silicone
- Silicon
- Carbon
- Hydrogen
- Curing