Topical and Transdermal Formulation Development
Marc B. Brown, Adrian C. Williams in The Art and Science of Dermal Formulation Development, 2019
For chronic dermatological disorders such as eczema, psoriasis, and dermatitis, occlusive formulations such as ointments or anhydrous systems are often preferred since these preparations have protective properties. However, such anhydrous mixtures are also usually very tacky and greasy and have poor aesthetic properties. Although such formulation types are extremely useful as emollients due to their occlusive properties, their value as topical products is limited by the poor solubility of many drug substances in them. In such cases, drug solubility can only be enhanced by formulating them with hydrocarbon miscible solvents, such as isopropyl myristate or propylene glycol. Anhydrous systems may also comprise pure polyethylene glycol (PEG) systems or triglyceride derivatives in addition to the traditional hydrocarbon systems containing white soft paraffin and petrolatum. Alternatively, silicone-based formulations may also be used, however, the regulatory status of silicones for topical use is currently limited, even though an extensive positive safety profile is emerging.
Lipid peroxidation and its measurement
Roger L. McMullen in Antioxidants and the Skin, 2018
Some of the most common lipid ingredients used in cosmetic formulations are petrolatum, beeswax, lanolin, jojoba oil, esters, natural glycerides, silicones, and ceramides.21 Many of these ingredients are complex mixtures of many different lipids. For example, beeswax is composed of wax esters, free fatty acids, fatty alcohols, and hydrocarbons. Not all lipid ingredients used in cosmetics undergo lipid oxidation. Saturated ceramides, which do not contain double bonds along the aliphatic chains, are not likely to oxidize. Likewise, many of the saturated hydrocarbon ingredients, such as those found in petrolatum, will not readily oxidize under normal environmental conditions. Silicones are also very stable and do not require antioxidant preservation. On the other hand, triglycerides, jojoba oil (which contains omega fatty acids), certain esters, lecithin, and many natural oils from plant sources are susceptible to oxidation. As the use of natural ingredients becomes more prevalent in cosmetic formulations, it will become imperative to prevent oxidation in these samples, since naturals tend to contain more unsaturated lipids than synthetic compositions.22,23
Organic Chemicals
William J. Rea, Kalpana D. Patel in Reversibility of Chronic Disease and Hypersensitivity, Volume 4, 2017
Silicone rubber is a macromolecule with an inorganic base. The outstanding properties of silicone rubbers are their heat and weathering stability. Pure silicone rubber is acceptable for sealants in the houses of the chemically sensitive if it is used sparingly. Also, there appears to be less triggering of the clotting mechanism and vessel wall irritation in catheters made of pure silicone rubber. Arthritic and myalgic symptoms have occurred in chemically sensitive patients with silicone implants. Silicone breast implants and other silicone implants have been shown to be toxic to many individuals. They have been shown to create and exacerbate chemical sensitivity and chronic degenerative disease.41 However, some patients have been shown to tolerate cataract eye implants (Figure 5.21).41
Marine biofouling and the role of biocidal coatings in balancing environmental impacts
Published in Biofouling, 2023
For the next generation of FR coatings, advances from the medical industry, such as zwitterionic molecules and quaternary ammonium compounds, may be utilized (Liu et al. 2013; Yeh et al. 2014; Martinelli et al. 2018). However, an issue with mobile hydrophilic components is the potential depletion into the aqueous environment (Camós Noguer et al. 2017a). So far, released silicone oils are not considered as detrimental to the environment due to their inert properties. With extended use and chemical variation, their potential toxic effect at elevated concentrations in closed marinas should be kept in mind (Lagerström et al. 2022). However, this can be prevented through direct functionalisation of the backbone of the silicone matrix, changing the molecular weight of oils, or increasing the density of the silicone matrix (Mazan et al. 1995; Camós Noguer et al. 2017b).
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
Drug eluting implants in pharmaceutical development and clinical practice
Published in Expert Opinion on Drug Delivery, 2021
Ashley R. Johnson, Seth P. Forster, David White, Graciela Terife, Michael Lowinger, Ryan S. Teller, Stephanie E. Barrett
Finally, silicones are a family of polymers defined by a long chain of alternating silicon and oxygen atoms [117,118]. The most commonly used silicone in medical devices is poly(dimethylsiloxane) (PDMS), which contains methyl groups as side chains. This polymer has been used in pacemaker leads, mammary prostheses, drainage implants for glaucoma, contact lenses, cochlear implant coatings, transdermal patch adhesives and denture liners. Silicones have found use in these applications due to their beneficial properties, including their biological and chemical inertness, resistance to oxidation, low modulus, low surface adhesion, high oxygen permeability and ability to be formulated in the absence of stabilizers. Unlike the previously described polymers, poly(dimethylsiloxane) is not a thermoplastic. Instead, silicones are extruded at low temperatures and then cured under heat or UV light [119].
Related Knowledge Centers
- Elastomer
- Polydimethylsiloxane
- Polymer
- Silicone Rubber
- Organosilicon Chemistry
- Polymer Chemistry
- Repeat Unit
- Organyl Group
- Polymer Backbone
- Cross-Link