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Silicone stands out in medical applications, owing to its suitable properties, including biocompatibility to human tissue , resistance to bacteria and corrosion, sterilisability, and being odourless , tasteless and non- reactive t o other materials, says Angelica Buan in this report.
The global demand for silicone, projected to be worth US$21 billion by 2021, is supported by advancing medical technologies. R&D for new product development and increasing demand from emerging economies are expected to drive market growth for silicone in the coming years, Zion Research notes in a market report.
A major player in silicones, Michigan-headquartered Dow Corning has launched a range of silicone pressure sensitive adhesives (PSA) for medical devices.
The MG-2XXX Series of four PSAs provides strong (shear force of 21 kg), conformable adherence of medical devices over extended wear periods without irritating or sensitising the skin, says the firm. The new PSAs are suitable for use in medical device applications requiring secure adhesion to the skin, such as ostomy appliances, monitoring devices, surgical dressings and drapes, hairpieces and external prosthetic devices. All four grades have successfully passed biocompatibility testing for cytotoxicity, skin irritation and skin sensitisation according to US Food and Drug Administration (FDA) regulations for non-clinical lab studies (21CFR58).
Additionally, it introduced three new bio-medical grade liquid silicone rubbers (LSRs). Available in Shore A hardnesses of 40, 50 and 70, these LSRs comprise the new Silastic Q7-78XX series and C6-7XX LSR series for short term or non-implant applications with three initial products.
Meanwhile, another notable offering from Dow Corning for the medical device market is its Topical Ingredients portfolio, which it unveiled late last year at the American Association of Pharmaceutical Scientists’ (AAPS) meeting in Colorado. The new ingredients have been designed to help customers drive innovations in topical over-thecounter (OTC) and medical device products that treat scars, stretch marks, acne and other skin conditions, and support their needs for compliance with increasing regulatory requirements.
An alternative to glass
In a related development, Düsseldorf-headquartered glass and plastic products specialist Gerresheimer has utilised Dow Corning’s 360 MD colourless and odourless polydimethysiloxane fluid for its new siliconised Cyclo- Olefin-Polymer (COP) syringes.
COP is an interesting plastic alternative to glass syringes due to the growing demands of novel agents on their primary packaging. Medications for cancer therapy, for example, can be extremely aggressive to the point where the break resistance of a syringe is a decisive criterion for selection. Innovative biotech medications, on the other hand, are often effective in the smallest of doses and are frequently very expensive. Syringes made of this material are biocompatible, break-resistant, and transparent as well as do not interact with the packaged medications. Its geometry also reduces dead volume, leaving behind less of the expensive medication in the syringe.
The first German-made product of this line is a 1 ml long Gx RTF (ready-to-fill) ClearJect COP syringes with a 27-gauge, 12.7 mm, and thinwall stainless-steel cannula with three bevels, suitable for demanding, sensitive medications and high-viscosity agents.
Gerresheimer currently offers a range of prefillable COP syringes produced by long-time company partner Japanbased Taisei Medical Co. Gerresheimer is assuming the sales and technical consulting roles for ClearJect syringes for customers in Europe and the US. The company is now expanding its product portfolio of COP syringes and is combining RTF concept of glass syringes with ClearJect to create the new Gx RTF ClearJect.
Wound care application
Bluestar Silicones, which has 20,996 sq m implant-grade silicone facility in South Carolina, offers its Silbione Biomedical LSR line for long-term implant applications and its Silbione skin adhesives for wound care and wearable devices.
Available in ShA 01 through 70 hardnesses, Silbione Biomedical LSRs are said to offer lot-to-lot consistency, optimising product design in an easy-to-process formulation, improving cycle time and part quality, says the company.
Silbione soft silicone adhesives for wound, scar, transdermal and wearable device applications are said to feature comparatively the highest tack level available for enhanced, yet gentle adhesion to the skin. High tack Silbione RT Gel 4642 enables coaters to achieve improved adhesion levels to the skin at lower coat weights than other materials currently available on the market.
In addition, the company also offers a range of flexible silicone technologies ideal for wearable devices, including LSR, heat cured rubber (HCR), room temperature vulcanised (RTV) silicones and silicone foam.
The company’s low-durometer LSRs, Silbione LSR 4301 and Silbione 4305 (01 and 05 ShA), deliver high tear strength and elongation for soft cushioning and vibration dampening applications. Its patented silicone foam, Silbione RT Foam 4241, offers low density open cell silicone foam for flexible, breathable applications.
Meanwhile, Cinogy with its head office in Duderstadt in South Lower Saxony enables nursing staff to treat chronic wounds and skin diseases with a procedure that promotes wound healing and fights multi-resistant pathogens. The sterile sensor pad, through which the spacer comes into contact with the human skin, is manufactured using TPE of the Thermolast M series from German firm Kraiburg TPE.
Cinogy developed the first portable device to generate non-thermal, or “cold” plasma directly on the skin at atmospheric pressure. In the patented PlasmaDerm process the spacer is placed on the skin. By activating high-voltage impulses, electrical fields transform the air between the spacer and skin into non-thermal plasma. The patient may feel a slight tingling of the skin, but no pain whatsoever. As opposed to existing spot treatments, the electrode in the Cinogy process is mechanically flexible and has a large area to ensure an even distance from the skin.
Improving MR procedures
Germany-headquartered cardio and endovascular medical technology company, Biotronik, has launched Solia S ProMRI, featuring a 5.6 French lead body, available in three size configurations of 45, 53 and 60 cm lengths.
The product, the smallest MR (magnetic resonance) conditional pacing lead available in the US, has been recently approved by the FDA. It features a polyurethane coating over silicone designed to reduce friction, facilitate introduction through small vessels and complex anatomy, while the soft distal segment helps reduce stress and minimise myocardial trauma.
With the limitations in the variety of leads available, Solia S ProMRI is said to offer more versatility and therefore improved procedures.
Biotronik says its ProMRI technology enables patients with a pacemaker, implantable defibrillator, cardiac monitor, or cardiac resynchronisation therapy defibrillator (CRT-D) to undergo an MRI (Magnetic Resonance Imaging) scan.
Implant to enable movement
Researchers at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, have developed a device that is meant to mimic the mechanical properties of soft tissues in the brain and can simultaneously deliver electric impulses and pharmacological substances. The device can be applied directly onto the spinal cord without causing damage and inflammation, because its elasticity and its potential for deformation are almost identical to the living tissue surrounding the spinal cord. This is a key improvement, compared to traditional implants that are more rigid and therefore would have caused significant nerve tissue damage when implanted for a period of time. Thus, risks of rejection and/or damage to the spinal cord have been drastically reduced.
The implantable device called e-Dura, named after the dura mater, the protective tissue that covers the brain and the spinal cord, features a long, clear, ribbon-like structure made of silicone rubber covered with cracked gold electric conducting tracks that can be pulled and stretched. The electrodes are coated with a platinum-silicone composite.
A fluidic microchannel enables the delivery of pharmacological substances, in this case, neurotransmitters that will reanimate the nerve cells beneath the injured tissue. The implant can also be used to monitor electrical impulses from the brain in real time.
Scientists have tested the device prototype by applying a combination of electrical and chemical stimulation to paralysed rats. The implant proved its biocompatibility and effectiveness to stimulate movement, allowing the rats to regain the ability to walk on their own again after a few weeks of training.
With the positive results, the e-Dura implant shows potential application in patients suffering from neurological trauma or disorders, particularly individuals who have become paralysed following spinal cord injury. The next step for the scientists is to perform clinical trials in humans, and to develop a prototype for commercialisation