April 13, 2011

3 Min Read
Opinion: Silver-Alternative Antimicrobial Technologies Lack Versatility, Efficacy

Jeff Trogolo, CTO, Sciessent

The recent MPMN cover story, "Antimicrobials: Beyond Silver," discusses next-generation antimicrobial technologies that are diverging from the silver trend. To some, research in these areas may imply an underlying notion that silver-based technologies have run their course or have certain limitations. However, there is ample evidence pointing to the strength of silver as it continues to dominate the market for antimicrobial devices with multiple new silver-based devices receiving FDA approval within the past six months. And while some of these technologies have new chemistry--which demonstrates the adaptability of silver--the general principles have been around for decades. Medical device manufacturers using the correct silver-based antimicrobial technology for a specific application have found that silver is quite versatile and tunable for most clinical uses. The same cannot be said for all rival, silver-alternative technologies, however.

One specific example is a category of nonsilver antimicrobial technologies that are referred to as 'contact-kill' technologies. They generally consist of long-chain molecules with cationic ends. The cationic end pierces components of the bacterial cell wall causing it to rupture and die. Advantages claimed by manufacturers of these technologies are that they are nonleaching and do not lead to the development of resistance in microorganisms. These claims sound impressive on the surface, but if you dig a little deeper into the technology and how it works, it becomes clear that these contact-kill technologies cannot be effective for any meaningful duration in a clinical environment. These long-chain compounds need to have direct contact with the microorganisms in order to penetrate their cell walls. It is well known that artificial surfaces introduced into the body immediately (within minutes) become covered in a conditioning layer of adsorbed proteins. This conditioning layer masks these long chains and effectively neutralizes the functional ends of the molecules, rendering the surface identical to a nonantimicrobial standard device and allowing microorganisms to adhere to this layer of adsorbed proteins.

In contrast to these long-chain molecules that are bound to the surface, silver-based technologies elute silver ions. The short-range mobility of ionic species circumvents the fouling characteristics of protein buildup. Therefore, provided the device is sufficiently loaded to overcome the effect of adsorbed proteins, an effective concentration of silver ions will be present at the surface to prevent bacterial colonization. Silver-based devices on the market today have shown efficacy in this challenging protein environment for up to 30 days.

One reason that medical device manufacturers increasingly choose silver as their embedded antimicrobial of choice is its ability to overcome the harsh environment of the body while maintaining biocompatibility. A naturally occurring element whose antimicrobial properties have been recognized for hundreds of years, silver has proven to be an outstanding fit for the medical device market, providing an effective piece in the infection control tool kit and an ideal differentiator for manufacturers.

Read the cover story, "Antimicrobials: Beyond Silver," to learn more about the silver-alternative technologies that Trogolo references. Plus, check out MPMN's gallery highlighting five novel antimicrobial technologies in development.

The opinions expressed in this article solely represent the views of the author and do not necessarily represent the opinions of MPMN, Qmed, or their parent company UBM.

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