Silicones are a general category of synthetic polymers whose backbone is made of repeating silicon to oxygen bonds. They are typically heat-resistant and either liquid or rubber-like, and are used in sealants, adhesives, lubricants, cooking utensils, and thermal and electrical insulation. Some common forms include:
- silicone oil
- silicone grease
- silicone rubber
- silicone resin
- silicone caulk
Find medical grade plastics
Did you know that Prospector® has listings for thousands of medical grade plastic materials? You can quickly search, compare, and find alternatives with Prospector.
Create your FREE account now!
Medical applications of silicones
Useful properties specific to medical applications include biocompatibility and biodurability, which can be expressed in terms of other material properties such as hydrophobicity, low surface tension, and chemical and thermal stability. For example, their hydrophobic (water-repellent) character caused silicones to be considered for blood coagulation prevention as long ago as the mid-1940s.
A particular challenge in medical applications is that many components may have to be tough enough to withstand challenges like heat, pressure, and chemical exposure while, at the same time, being comfortable enough for physical contact with a patient. Not many materials can meet such seemingly conflicting demands, but liquid silicone rubber (LSR) can. LSR is a flexible thermosetting plastic that is available in a range of hardnesses and compositions, allowing the material’s properties to be matched to the application.
LSR is approved for medical applications with skin contact. Its stability and hydrophobic nature protects the cured material from being affected by skin. At the same time, and unlike materials like latex, LSR is nonallergenic, so skin is not affected by the plastic. It is hygienic, resisting the growth of bacteria and fungi, and the softness and flexibility of the material helps ensure patient comfort while its water-repellent nature prevents it from sticking to wounds.
Silicone resin is well known for its applications in aesthetic implants: implants are widely used in the breast, scrotum, chin, nose, cheek, calf, and buttocks. Some of these devices may also employ a softer-feeling substance known as silicone gel. The gel is a lightly cross-linked silicone elastomer, without silica or other reinforcing filler, that is swollen with polydimethylsiloxane fluid. The gel is contained within an elastomer shell in breast, testicular, and chin implants.
But the range of applications is much wider. By the end of the 1960s, silicone materials were being employed or evaluated in numerous health-care applications:
- orthopaedics
- catheters
- drains and shunts of numerous descriptions
- components in kidney dialysis, blood oxygenation, heart bypass machines and heart valves
The most significant orthopaedic applications of silicone are the hand and foot joint implants.
Introducing functional molecules into living cells
Giant vesicle (GV), a liposome consisting of a phospholipid membrane, has a structure similar to live cells and is several micrometers in size. For this reason, it has been used for various biochemical experiments such as the introduction of functional molecules into living cells, and also made into a vessel of artificial cells and molecular robotic research.
Recently, Tohoku University reported a technique for simple, mass production of giant vesicles using a porous silicone material1. The technique involves adsorbing a lipid into a silicone porous material resembling a “marshmallow-like gel” and then squeezing it out like a sponge by impregnating a buffer solution.
This simple method is expected to be applied not only as a tool for cell research requiring giant vesicles but also for medical and cosmetic purposes.
Per Tohoku University2, many methods have been proposed for the preparation of GV dispersions, but in the lab, the method of producing large quantities of several hundred millilitres at one time has been limited. In 2011, Dr. Shinichiro Nomura discovered that GVs were generated by adsorbing lipid into porous polydimethylsiloxane (PDMS) and squeezing it in a buffer solution.
The practical development of the GV generation method and improvement of its efficiency is achieved by using a pore-controlled silicone composition flexible macro-porous material, which can be described as a “marshmallow-like gel” (Figs 1 and 2).
Self-assembling silicone-based polymers
Also in Japan, scientists at Tokyo Institute of Technology, RIKEN and Tohoku University have developed a silicone polymer chain that can self-assemble into a 3D periodic structure3. They achieved this by using their recently reported self-assembling triptycene molecules to modify the ends of the polymer chains (Fig 3).
The development of novel soft materials for various optical, mechanical, heat/charge transportation and nanotechnological applications would greatly benefit from techniques to create polymer assemblies in periodically ordered structures. Such ordered structures are created using molecular scaffolds or by modifying certain parts of the polymers used so that they self-assemble into the desired shape.
The team designed polydimethylsiloxane (PDMS) chains with the ends replaced by a triptycene molecule. They hoped that these modified silicone chains would also exhibit self-assembling behaviour. The team’s findings are promising and they will carry on investigating the self-organization of polymers, intending that the results will lead to the development of novel materials and synthesis techniques.
Hand-picked articles for you:
- K Show Recap: Medical Polymers in the Spotlight
- Plastics Under the UV Spotlight
- Spin to Win: Polymers in Regenerative Medicine
References:
- Gen Hayase, Shin-ichiro M. Nomura. Large-Scale Preparation of Giant Vesicles by Squeezing a Lipid-Coated Marshmallow-like Silicone Gel in a Buffer. Langmuir, 2018; 34 (37): 11021 DOI: 1021/acs.langmuir.8b01801
- Tohoku University: Simple, mass production of giant vesicles using a porous silicone material
- Tokyo Institute of Technology: No Assembly Required: Self-assembling Silicone-based Polymers
The views, opinions and technical analyses presented here are those of the author or advertiser, and are not necessarily those of ULProspector.com or UL Solutions. The appearance of this content in the UL Prospector Knowledge Center does not constitute an endorsement by UL Solutions or its affiliates.
All content is subject to copyright and may not be reproduced without prior authorization from UL Solutions or the content author.
The content has been made available for informational and educational purposes only. While the editors of this site may verify the accuracy of its content from time to time, we assume no responsibility for errors made by the author, editorial staff or any other contributor.
UL Solutions does not make any representations or warranties with respect to the accuracy, applicability, fitness or completeness of the content. UL Solutions does not warrant the performance, effectiveness or applicability of sites listed or linked to in any content.
Leave a Reply or Comment