SURFACE TREATMENT
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The I-vation from SurModics features a coating that enables sustained drug delivery into the posterior chamber of the eye.
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A number of modifications to medical devices fall under the umbrella of surface treatment, from the simple cleaning of a substrate to altering its chemical structure. Surface treatment technology is undergoing changes, which, in turn, are changing the sorts of medical devices thought to be possible. In addition to developments in material properties, advances in surface-treatment equipment are enabling greater automation. And the use of wet chemicals to clean surfaces is beginning to give ground to greener options.
Drug-delivery coatings may advance treatment of retinal disease
The application of coatings with drug-delivery properties on implantable devices is a rapidly developing technology. The treatment of retinal disease is one area that stands to benefit from this convergence of drugs and devices.
Diseases of the retina, such as age-related macular degeneration (AMD) and diabetic macular edema (DME), are among the leading causes of blindness in the Western world. Until recently, little could be done to stop the progress of these conditions. Drugs recently approved for the treatment of AMD, however, have demonstrated that it may be possible to halt the progress of the disease and possibly even reverse the damage.
A drawback of these new drugs is that they require an injection directly into the eye, as often as once a month for several months, even up to two years. The injection regimen carries a risk for tissue damage and infection, along with the possibility of poor patient compliance. As a result, an alternative drug-delivery method requiring less frequent intervention could be beneficial for patients.
“There is a lot of interest in getting a sustained-release drug delivery system for retinal disease to the market,” says Aron Anderson, chief scientific officer at SurModics (Eden Prairie, MN, USA). Specialising in site-specific drug-delivery methods for other medical applications, SurModics has developed an implant designed exclusively for the sustained delivery of therapeutic agents to the eye.
Currently in human trials, the I-vation sustained drug-delivery system is an implantable helical coil that uses the company’s polymer coatings to release therapeutics into the posterior chamber of the eye. Compatible with the delivery of protein or steroid molecules, the system delivers drugs for up to two years. The platform is implanted through a minimally invasive pars plana needlestick less than 0.5 mm in diameter. The helical shape is designed to maximize the surface area available for drug delivery, while keeping device size to a minimum.
Pending US FDA approval, the company is currently seeking medical device and pharmaceutical companies interested in commercializing the technology.
Moving towards automation
Coating medical devices remains an often slow and challenging process. Bioengineered materials and novel formulations can be expensive and have to be applied frugally. This presents an obstacle to automation. Making midstream adjustments on a line to avoid overspray or misdirection can mean shutting down production for periods of time; frequent stoppages can reduce or negate the advantage gained by automation.
Low-volume/low-pressure spray valve systems from EFD (Dunstable, Beds, UK) can address a variety of requirements for surface-treatment and other applications, according to the firm. “Low-volume/low-pressure technology is a specialised, highly efficient transfer system to apply fluids onto a substrate,” Waldorf says. “We take low- to medium-viscosity fluids and give the user adjustable control over the atomizing force, which starts as a drop of fluid. Using this technique, we avoid misdirection and overspray.”
The ValveMate 8040 is one of the company’s automated valve systems that incorporates low-volume/low-pressure air. It enables adjustment of the spray valve’s open time in increments as small as 0.001 second. The system incorporates a microprocessor that regulates the amount of fluid sprayed as air is applied to the nozzle. The result, according to the company, is exceptional spray pattern definition without time-consuming programming or mechanical adjustments that would require shutting down the production line.
Typical applications for the valve include lubricating the interior of syringes with silicone, coating stents, applying protein solutions on membranes for test strips, and dispensing saline solutions in the ocular market.
One small step for the planet
The cause of automation is also advanced by a new plasma treatment system from March Plasma (Concord, CA, USA), according to Erik Lenski, life sciences market manager. Some plasma systems can require manual batch processing, which is incompatible with a portion of today’s in-line manufacturing operations. The company’s FlexTrak in-line machine, however, is an automated batch-processing system that can treat 480 substrates or carriers per hour, according to the company.
Lenski also draws attention to the system’s environmental credentials. “Plasma replaces the chemicals required in wet chemistry cleaning systems that have to be treated and discarded, making this an environmentally friendly process.”
Plasma is partially ionized gas consisting of ions, electrons, free radicals, and neutral species. This ionized gas mixture is conductive and highly reactive, which provides the basis for the plasma process. During treatment, the surface plane is suspended between electrodes. The chamber is evacuated, process gas is introduced, and the electrodes are energized with radio frequency energy, all of which combines to initiate the plasma.
Plasma treatment has a number of surface treatment functions beyond cleaning. As a result, plasma systems have the potential to be versatile machines. The FlexTrak system, for example, can be used for etching as well as cleaning. Other plasma treatment systems can be used for deposition, adding surface functionality, and cross-linking.
