Smart Antimicrobial Coatings and Surfaces

The current market for antimicrobial coatings and surfaces is driven by the need to selectively combat new threats from bacteria, viruses and fungi.  These new challenges include:

•    Microbes that have become resistant to traditional antimicrobials.
•    The growing issue of hospital-acquired infections (HAIs),
•    An inadequate pipeline of antimicrobials from traditional suppliers

In addition, the opportunities for antimicrobial surfaces extend well beyond healthcare facilities and include medical implants, surgical equipment, kitchen surfaces, appliances, walls and floors, consumer products, health club equipment, furniture, clothing/textiles.

As n-tech sees it, all this represents a significant opportunity for smart materials in the form of smart antimicrobials that take completely new paths towards the destruction of microbes.  However, n-tech also believes that smart antimicrobials will face serious competition from:

•    Existing antimicrobials that have somehow been made more powerful and effective. Versioning existing antimicrobials has important commercial advantages.  OEMs are likely to be biased towards higher-performance versions of materials they already know, so there is a hurdle over which the new smarter antimicrobials must fly.

•    Entirely new materials that in no way can be said to be smart. Thus there is considerable and growing interest in copper and copper alloys being for antimicrobials even though these copper materials are in no sense smart

In spite of this competition n-tech sees significant revenue generation opportunities emerging for smart antimicrobials, some of which utilize the nanotechnology developments of the past decade.  These opportunities will manifest themselves in at least three different types of products (1) new kinds of smart coatings, (2) novel additives for coatings, and (3) specially nano-patterned surfaces.

What this smart antimicrobials can bring to the table are mechanisms for microbe killing that are (at least potentially) hugely more effective than what has gone before.  n-tech analysis suggests that smart antimicrobials fall into five (somewhat overlapping) categories.

The Selective Killing of Microbes:  A Role for Smart Materials 

Our analysis suggests that the earliest opportunities for smart antimicrobials will be for those that are smart enough to kill harmful microbes while leaving the beneficial ones untouched.  Here smart antimicrobials directly address strain resistance and compete head on with most conventional antimicrobials.

In the past, gold nanoparticles have been used for this kind of smart selective antimicrobial.  Most of the development work at the present time, however, appears to involve peptides, which are less susceptible to development of microbial resistance than other antibiotics.

Because of the market pressure to develop selective antimicrobials, we expect other materials of this type to quickly make it out of the labs.  In particular, we see a big commercial future for antimicrobial polymers, which are potentially cost competitive with regular disinfectants but can be fabricated so that they kill selected microbe without releasing polluting biocides into the environment.

Smart Polymers and Smart Antimicrobials

Selective antimicrobials are not the only way that n-tech believes the polymer industry will be able to compete in the smart antimicrobial industry.

Highly functionalized polymers can be deployed in a manner that is antimicrobial in nature, but they are not necessarily smart. For example, quaternary ammonium ion-containing polymers (PQA) have been proven to effectively kill cells and spores through their interactions will cell membranes.  Some polymers can also have their antimicrobial functionality enhanced by doping them with copper or silver.

Where we do see polymers being deployed in a smart antimicrobial role is as an extension of self-healing polymers, which for now, is the commonest type of self-healing material.

Specifically, in the a few years, n-tech envisions that a class of multi-functional polymer antimicrobials that combines antimicrobial and self-healing functionality; self-healing cracks in surfaces is also a way of reducing microbial threats and mixing this with chemical-based destruction of microbes appears to be an important direction for new antimicrobials.

Self-Cleaning Antimicrobials

In fact, n-tech expects multi-functionality to be a key theme in the commercial evolution of smart anti-microbials, with the combination of antimicrobial and self-cleaning being a key feature.

Self-cleaning materials, it should be noted, is a key area of development for smart materials firms and a material that provides “automated” surface cleaning is clearly an attractive business opportunity. Keeping surfaces microbe free is a matter of cleanliness, not just killing bugs. More specifically in these combo products the self-coating flakes off over time and the flakes carry the microbes along with them, leaving a clean surface behind.  This functionality is in addition to any specifically antimicrobial function.

Although self-cleaning antimicrobials might be fabricated in a variety of ways, today the technology appears likely to involve some kind of hybridization of antimicrobials with photocatalytic materials – typically titania. And the literature suggests that such smart hybrids might not only purify surfaces, but also air and water.

Antimicrobials and Super-hydrophobic Materials

As we see it, another area where antimicrobials can draw from important R&D programs within the context of the entire smart materials sector is in the utilization of super-hydrophobic materials.  Super-hydrophobic textiles already explicitly claim antimicrobial effects and this claim might be extended to super-hydrophobic coatings and surfaces more generally.

Super-hydrophrophic materials represent a major area of research within the smart materials community.  Today, its major focus is creating self-cleaning surfaces and the technology itself is directed towards imparting a rough surface at the micro- or nano-level.  This can be achieved through a using one of number of well-developed processes such as lithography, LbL deposition, hydrothermal synthesis, etc.

While, antimicrobial activity is probably not the focus of the super-hydrophobic research, superhydrophobic surfaces do represent an efficient means of imparting antimicrobial functionality. A passive antibacterial effect results from the poor ability of microbes to adhere a super-hydrophobic surface.

Nanotechnology and Antimicrobials:  Advanced Functionality, Smartness and Competition

The role of nanotechnology also cannot be ignored when considering the commercial potential of smart antimicrobials.  The original focus of nanotechnology was on devices that were smart at the molecular level. This stopped being true a decade ago.  Nonetheless, nanotechnology remains highly relevant to the development of smart antimicrobials:

•    The very high reactivity of nanomaterial-based antimicrobials might be thought of as their ability to respond quickly to external stimuli; a type of intelligence.

•    In addition, the markets for antiantimicrobials based on nanomaterials (smart or otherwise) are driven by exactly the same forces as those driving the markets for more classically smart materials.

•    Finally, surface modification is an important part of providing advanced antimicrobial action.  This is because the physical topology of a surface determines how viable the surface environment is for bacteria. Patterning using nanomanufacturing techniques would seem likely to play a major role here.

Silver nanoparticles as a smart antimicrobial:   Silver nanoparticles have been shown to have significant antibacterial properties and silver compounds of various kinds are used for anti-bacterial processes.

Silver nanostructures if used for antimicrobial products may make a strong claim to being smart, since they may be fabricated in way that makes them self-assembling.  In addition, silver antimicrobials inherently contain a mechanism for the slow release of silver; which is surely a smart feature.

Nanosilver is already extensively used as an antibacterial – for example nanosilver coatings are widely used on surgical instruments for this purpose.  However, there are also limitations.

Nobody yet really understands the chemistry of nanosilver antimicrobial action and consequently it is still quite hard to pin down, just how effective its antimicrobial action really is.  In addition, in some geographies, the use of nanosilver is limited because it is seen as a biocidal pollutant.

Nanomaterials as competition for smart antimicrobials: n-tech also sees nanomaterial-based antimicrobials as providing potential significant competition to smart antimicrobials. Some important examples of nanocoatings that we believe will compete directly with smart coatings of the kind that we are primarily concerned with here include:

•    Organosilane nanocoatings:  These are highly abrasive to virus, bacteria, and fungi. The appeal of organosilanes is enhanced by the fact the killing mechanism is physical so even otherwise strain-resistant microbes get killed.  However, no one is yet certain of just how effective these materials can be

•    Chitosans:  Chitosans are a polymer made from the chitin nanoparticles. They have been used for their antibacterial properties for a while, Chitosan is more effective against fungi and viruses than bacteria.

•    Black silicon: This is a synthetic material studded with needle-shaped nanostructures that is used primarily for sensor applications, but which can serve as a potent antibacterial agent

The Bottom Line:  A Roadmap for Smart Antimicrobials

Smart antimicrobials are already in use to some extent – especially if one takes nanosilver as part of this story.  Also the extensive work that is currently being undertaken on peptides suggests that smart antimicrobials that are selective in their ability to kill microbes are approaching full-scale commercialization.

Positive market signs for smart antimicrobials: Nonetheless, this is the kind of early stage technology that under other circumstances, n-tech would not see as an extensive opportunity.  Often such early-stage technology doesn’t generate significant revenue for a decade.  However, in this case, the development of new antimicrobials that combat a range of emerging microbial threats is quite literally a matter of life and death.

The bottom line therefore is that we expect truly smart materials to become a major part of antimicrobial technology within a few years.  These will include a growing range of truly smart antimicrobials that are multifunctional, perhaps including self-cleaning and/or self-healing capabilities as well as microbe killing functionality.

Also positive for this sector the smart materials market is that – unlike smart antimicrobial drugs – no extensive regulatory barriers exist for antimicrobial coatings surfaces.  Makers of smart antimicrobials therefore face – relatively speaking – few barriers to entry.  In addition, a growing awareness of new diseases should help propel smart antimicrobials out of the surgical tool/medical surface markets on which antimicrobials currently rely.

Negatives: This is not to say that the smart antimicrobial market is guaranteed to be a money machine.  For one thing, members of the antimicrobial research community have complained that not enough investment is going into this sector, although we expect this to change.

Also important is the fact that smart antimicrobials face quite serious competition from a number of directions.  As we mentioned at the beginning of this chapter, as the result of improved R&D conventional antimicrobials may see improvements that will enable them better to address the current challenges for these types of coatings surfaces.  However, even with higher-performance conventional antimicrobials, it may be just a matter of time before these products may become inadequate.

We also expect competition to come from other materials – mostly copper, but also nanomaterials of various kinds.  For the most part these appear to be ahead of smart antimicrobials in terms of their evolution.  We also anticipate that these materials are going to continue to see growing revenues in the next decade.

Nonetheless, there are some dimensions along which n-tech believes that smart antimicrobials will be able to compete very effectively with these new kinds of antimicrobials including nanocoatings and nanostructures.  Most importantly, as we have seen, the capabilities that smartness provides cannot be copied by non-smart materials, even if they are nanomaterials.

In addition, it seems that the antimicrobial effects associated with certain nanomaterials are not well understood and this raises questions about their efficacy as antimicrobials.