Antimicrobial Surfaces For Pandemic Prevention?

Conrad K.

The next big research agenda in biosecurity? Or a flawed technology dead on arrival? Spoiler: it’s somewhere in between.

Summary

I spent ~15-20 hours conducting research, holding expert interviews, and thinking through whether we should be excited about antimicrobial surfaces for pandemic prevention and, if so, what the next steps for this technology should be. Overall, I’m reasonably confident (~75%-80%) about the following but note it is highly oversimplified:

Antimicrobial surfaces inhibit the growth and spread of microorganisms. They can be categorised based on functional mechanism (antifouling, biocidal, hybrid), mode of action (chemically-functionalised, physical, biologically-functionalised, or composite), spectrum of effectiveness (targeted or broad-spectrum), and application (antimicrobial materials, pre-coating, or applied).
Research shows that antimicrobial surfaces can effectively kill microbes in the right conditions, but many unknowns remain regarding their efficacy outside lab settings, interactions between pathogens/surfaces/fomites, and use for mitigating pandemics.
Evidence is limited on antimicrobial surfaces preventing infections. Studies often have design issues and knowledge gaps remain regarding transmission mechanisms.
Little is established about the effectiveness of antimicrobial surfaces for mitigating pandemics. More research is needed on pathogen transmission routes, surface use cases, and cost-effectiveness.
Downsides include surface degradation over time, potential toxicity, inducing antimicrobial resistance, regulatory barriers, and high costs for novel technologies.
Antimicrobial surfaces are beginning to see more real-world use, with potential applications beyond infection control. The market for antimicrobial surfaces is growing.
Key open questions remain about the fundamentals of fomite transmission, interactions between pathogens and surfaces, surface degradation, accessibility, supply chain considerations, and ideal use cases.
Some reasons to be excited include reducing fomite transmission, continual action without reapplication, and multipurpose benefits. However, high costs, regulatory hurdles, concerns about antimicrobial resistance, and many research uncertainties are reasons for caution.
Overall, I lean towards it being worthwhile to resolve foundational questions about antimicrobial surfaces through (i) further testing and modelling; (ii) producing an ontology of surfaces, and (iii) conducting a detailed scoping of potential use cases for pandemic prevention.
Oxford Biosecurity Group will soon be running a project exploring producing an ontology of antimicrobial surfaces, and we’re looking for a co-lead for this project. Reach out to us at contact@oxfordbiosecuritygroup.com if you’re interested.

What Are Antimicrobial Surfaces?

Antimicrobial surfaces are surfaces that are designed to inhibit the growth and spread of microorganisms, including bacteria, viruses, fungi, and algae. One way they can be categorised is as follows:

Functional Mechanism
1. Antifouling: surfaces that prevent microbial attachment and growth.
  1. E.g. superwettable surfaces such as superhydrophobic modified aluminium or mussel-inspired superhydrophilic surfaces that work by either preventing microbial adhesion (hydrophobic) or creating a water barrier between microbes and the surfaces (hydrophilic).
2. Biocidal: surfaces that actively kill or inhibit microbes.
  1. E.g. metals such as copper which release ions that kill microbes.
3. Hybrid: surfaces combining both antifouling and biocidal properties.
  1. E.g. honeycomb-like patterned surfaces which trap bacteria, both preventing further growth and killing them.
Mode of Action
1. Chemically-functionalised: utilising chemicals that have antimicrobial properties.
  1. E.g. ph-activated antibacterial coatings using polycations, given bacteria form biofilms (in part) by being negatively charged. This attraction disrupts biofilms.
2. Physical: relying on the physical structure or properties (like texture or light-activated catalysis) to inhibit microbes.
  1. E.g. shark skin mimetic surfaces with microscale patterns that physically prevent bacterial colonisation.
3. Biologically-functionalised: using biological agents (such as enzymes)
  1. E.g. phage-functionalized model surfaces that use bacteriophages in their coating.
4. Composite: integrating multiple modes (chemical, physical, biological) in one approach.
  1. E.g. using chemical ‘wet-etching’ to create nanostructured surfaces.
Spectrum of Effectiveness
1. Targeted: the scope of antimicrobial surfaces can be constrained in different ways:
  1. Pathogen-specific: effective against particular types of pathogens.
    1. E.g. nanopatterns, such as those on the surface of the Clanger cicada, only kill gram-negative bacteria but not gram-positive given the latter is more rigid due to having several peptidoglycan layers as opposed to one.
  2. Condition-dependent: effective in particular environmental conditions.
    1. E.g. Photocatalytic surfaces that require light exposure.
2. Broad-spectrum: effective against a wide range of pathogens.
  1. E.g. polycation coatings have been used to disrupt biofilm formation given most biofilms formed by bacteria, viruses, and fungi are negatively charged.
Application
1. Antimicrobial materials: surfaces that are themselves materials formed into fomites (inanimate objects).
  1. E.g. metals such as silver which release ions that kill microbes.
2. Pre-coating surfaces: surfaces that are layered on top of other materials or fomites as part of the production process.
  1. E.g. polymeric coatings that are applied onto pre-existing materials or fomites during their production.
3. Applied surfaces: surfaces that are applied to fomites after the manufacturing process.
  1. E.g. sprayable porous cellulose thin films with antimicrobial properties due to their hydrophilicity.

I note that this is my own categorisation that simplifies the sheer complexity of antimicrobial surfaces. Variation is also driven by differences in materials used, specific functional and physical mechanisms (e.g. thermoresponsive or pH-responsive mechanisms), or even whether the surface is ‘smart’ and can do things like switch between bacteria-killing and bacteria-releasing to prevent the build-up of death microbes.

What Do We Know About Antimicrobial Surfaces?

In summary, it seems like we know quite a lot about antimicrobial surfaces. However, there are also a very large number of unknowns and many knowledge gaps. I think three particularly salient knowledge gaps are (i) the deployment of antimicrobial surfaces outside lab conditions; (ii) exploring the full range of pathogen, surface, and fomite interactions, and (iii) exploring conditions specifically relevant to mitigating pandemics rather than just reducing the likelihood of transmission.

Effectiveness at Killing Microbes?

Most papers on this topic (i) explore a narrow set of antimicrobial surface types, (ii) pathogen types, and (iii) do not explore the broader robustness of their findings. They are often either in lab conditions, or natural experiments in hospital conditions. However, even then, the reality seems to be large amounts of variance. The effectiveness of antimicrobial surfaces at killing microbes depends on:

The surface itself affects the nature of pathogen interactions:
1. Some of this is endogenous: different surfaces have different inactivation rates. For example, more porous surfaces have been shown to lead to higher inactivation rates for influenza (e.g. due to desiccation from absorbing moisture).
2. Some of this is exogenous, particularly the different contact rates of different fomites and environmental degradation. Door handles, particularly in toilets and bathrooms, are notable examples of fomites that are breeding grounds for bacteria due to lots of contact.
The fomite might also affect interactions with applied surface coatings. For example, water-soluble polymers have a tendency to degrade in the presence of oxygen, high temperature, or sunlight illumination. All of these properties vary with the fomite in question.
The inactivation mechanism results in variance. Repellant mechanisms (e.g. superhydrophobic surfaces) will have a deactivation time, whilst other methods might be more instantaneous depending on the pathogen.
The pathogen in question introduces a great deal of variance. E.g. as mentioned above, gram-positive bacteria are often more resistant to physical modes of action than gram-negative bacteria due to having several peptidoglycan layers as opposed to one. Enveloped viruses (wrapped around by a lipid bilayer) tend to be more well-protected, but non-enveloped viruses tend to be more environmentally stable and resistant to detergents and heat due to not relying on this protective layer and being better adapted to their particular environment.

As a consequence, this leads to high variance in results for reasons including but not limited to:

There is high variance within surfaces across pathogens, for example, where for some pathogens (particularly fungi) killing time was a matter of hours to even days.
There is high variance across surfaces even with similar pathogens, for example, even the specific surface topography can affect which types of pathogens can be killed at all.
There is high variance across environments too. E.g. photocatalytic surfaces require lighting.
There is high variance from the testing protocol used.

However, putting variance aside, plenty of papers^[1] show that, in the right conditions, antimicrobial surfaces can kill microbes. By ‘work’, the industry threshold is something like a 2 or 3-log reduction in viable cells within minutes (seems to vary from 2-30 minutes) from contact with an antimicrobial surface (i.e. 99% to 99.9% kill rate). Highly effective surfaces (example) were in the >4 range, i.e. a kill rate of 99.99+%.

All else equal, on average, antimicrobial surfaces seemingly can kill microbes above the efficiency required to have an effect on infection after a few minutes^[2]. However, I note many of the results I could find were below the standard required by the FDA for high-level disinfection (which is a 6-log reduction) or the EU’s EN 1276 certification for an antibacterial cleaning product (which is a 5-log reduction).

However, research on all of the above is also lacking. There seems to be quite a lot of modelling of contamination levels on fomites (one example here), but less research on the effect of contamination levels on the rate of infection; speed of transfer, and how interactions between fomites and individuals or fomites and the environment - particularly for a wide range of pathogens. There is a lack of research testing these outside lab settings. The experts I spoke to concluded that many lab results have been promising and they have started to see some usage, but more research needs to be done to demonstrate their promise.

Effectiveness at Preventing Infections?

Being good at killing microbes does not necessarily correspond to being good at preventing infection, and my impression is that there is not yet academic consensus on the general utility of antimicrobial surfaces for preventing illness. One key variable here is the load required for transmission and the load required to make you ill. One academic I spoke to noted that COVID-19 required quite a low viral load to make you ill - noting I did struggle to find data here. Another key set of variables is due to the characteristics of the pathogen, such as how long it persists on fomites; its shedding characteristics; its resilience, and its replication rate.

A final important set of variables is the complexity of human-to-human transmission which can involve multiple routes, such as direct contact, respiratory droplets, and aerosols. The relative importance of these transmission routes can vary depending on the specific pathogen, the environmental conditions, and the interactions between pathogens and the human body, such as the pathogen's ability to penetrate mucus barriers, attach to host cells, and evade the immune system. On top of factors such as individual differences in susceptibility and immunity, these can further influence the likelihood and severity of infection. How these interplay with human behaviour is an additional source of complexity.

My impression is that the evidence is less certain due to the lack of well-designed studies. Many studies focus on copper, where the consensus seems to be that the evidence leans in favour of copper in preventing (particularly healthcare-associated) infections but that the quality of evidence is very low for this (for example). At least three systematic reviews and one literature review have come to this conclusion (Chyderiotis et al., 2018; Muller et al., 2016; Cochrane, 2017; National Services Scotland).

Some reasons why the quality of evidence seems to be so low seem to be (~60-70% confidence):

Data is sparse.
There is often quite a large variation in study design given the reliance on natural experiments (e.g. not controlling for variation in the placement of surfaces in hospitals).
Studies were frequently funded or supported by organisations that may have a financial interest in the promotion of antimicrobial copper surfaces (e.g. Cupron).
Many reports look into only a few types of microbes, species, and surface types.
There remain quite a few knowledge gaps about the mechanism for the antimicrobial properties of some surfaces^[3].

Actual cost-effectiveness analyses were difficult to come across, but for example, this study on antimicrobial catheters found they are cost-effective with significant uncertainty. Outside copper, efficacy evaluations and cost-effectiveness analyses are sparse. One expert I spoke to specifically pointed out that there was a lack of academic consensus on this question.

Effectiveness at Mitigating Pandemics?

Given the uncertainties around the efficacy of many surfaces in killing microbes and the lack of consensus on their efficacy in preventing infections, it is safe to say that very little is established about how useful antimicrobial surfaces would be for mitigating or preventing a pandemic. I want to flag a few reasons why the effectiveness of mitigating a pandemic is an additional complexity even if we were to establish the effectiveness of surfaces in preventing infections:

Pathogens differ in how reliant they are on fomite transmission (e.g., as opposed to respiratory transmission), and this is not established for many pathogens. In the early stages of COVID-19, there was a lack of clarity on the importance of fomite transmission for its spread, and it ultimately took a few months to confirm that fomite transmission of COVID-19 was indeed likely.
Naturally, the effect of antimicrobial surfaces will be sensitive to a pathogen's broader transmissibility, incubation period, and case fatality ratio.
The "win state" for antimicrobial surfaces doesn't need to be widespread transmission suppression, however. It could also be used to protect a handful of facilities or on PPE. Exploring more of these “win states” could be useful.
1. For example, if antimicrobial surfaces did play a key role in preventing a pandemic, it could be through mechanisms like next-gen PAPRs having antimicrobial surfaces or their widespread use on very high-transmission routes (e.g., aeroplanes).
2. They could also be particularly useful on surfaces likely to have particularly high concentrations of pathogens, such as hospitals, door handles, or metros. In these cases, the appropriate paradigm may be combining antimicrobial surfaces with a disinfection routine, where the advantage of this is both cost-saving and mitigating the damage of over-disinfection (e.g. contributing towards antimicrobial resistance; corroding substances, and reducing risks from the toxicity of substances like bleach).
3. These use cases mean their value may be in ensuring civilisational resilience. For example, facilities used to produce vaccines or therapeutics could be coated with antimicrobial surfaces to decrease the chance of infection in these sites.

There are probably countless further considerations. These include, but are not limited to, how their effectiveness differs by the type of built space; geographical heterogeneities, and various other factors about pathogens, their resulting diseases, and how they emerged.

Downsides?

An important downside is that antimicrobial surfaces will degrade over time. This rate of degradation is sensitive to the contact frequency of the fomite in question; properties of the surface in question, and many other contingencies (such as how much disinfection is also occurring). However, it seems that degradation is a problem for essentially all types of surfaces:

Bioiocidal surfaces will accumulate microbial debris that affects their functionality, and antifouling surfaces will lose their adhesiveness over time.
Patterned surfaces will also very likely degrade over time, and it is both an open question and dependent on the surface whether this is over days, weeks, months, or years.
The rate of degradation is sensitive to the material design, but they all have a half-life and must be reinstalled.
Materials like copper remain antimicrobial so long as microbes are exposed to their surface, and it does seem that tarnishing via oxidation seemingly does not affect copper’s antimicrobial properties. Though noting copper is biocidal so will accumulate debris unless regularly cleaned and disinfected.
However, environmental wear and tear will affect all surfaces.

However, many different types of surfaces will have a number of additional downsides:

Toxicity to humans and the environment is a risk: many biocidal agents are toxic. Copper, for example, demonstrates toxicity at high levels.
They may induce antimicrobial resistance, but this seems highly unexplored.
- According to one expert I spoke to, “microorganisms become tolerant or frankly resistant to [antimicrobial surfaces]; there have been lots of anecdotal reports”.
- The expert also pointed out that Staphylococcus aureus can carry plasmids coding for heavy metal resistance. I found evidence of this also.
Regulatory barriers might be quite high. This is not something I’ve necessarily been informed of directly, but I note quite stringent regulatory requirements for new products claiming disinfection efficacy, which also seems to line up with my understanding of regulations for disinfectants, which are generally quite thorough (e.g. this example of detailed EU regulation on biocidal products).

Cost?

The sheer breadth of antimicrobial surface types means there is obviously no single answer to how expensive are these. However, I wanted to highlight a few facts about their cost:

According to one academic I spoke to, the more novel technologies are extremely expensive to develop, and we are decades away from them being more mass-market.
For one comparison, we can compare copper to stainless steel (the standard in hospitals).
- According to these scrap metal prices, updated 18 September 2023, copper is anywhere from about 3 -7x more expensive than stainless steel. Roughly commensurate with these scrap metal prices. Its current price per pound is $3.85.
We can also consider the cost of titanium dioxide, which exhibits photocatalytic antimicrobial properties in the presence of UV and is widely used for paint. I roughly get figures of $3000 per metric ton^[4].
- Assuming the average house is about 2,300 sq. ft. and it takes roughly 15 gallons of paint to paint a house that size, the marginal cost of painting one house with titanium dioxide for its antimicrobial properties is (15/264*3000), or roughly $170.
- I caveat that it is not clear that painting buildings with titanium dioxide is uniquely cost-effective, given that titanium dioxide (TiO2) is typically photocatalytic under UV light. However, there is research attempting to produce TiO2-doped surfaces that have their antimicrobial properties activated with visible light.
Both copper and titanium oxide, being widely available metals, are very likely on the cheaper end of antimicrobial surfaces. Given other forms require complex technology or specialised materials to create, they are likely much more expensive.
- For example, antimicrobial paint on the market (so likely still cheaper than novel technologies) is much more expensive (~$250 for 2.25l of this product). Applying the same maths with a litres-to-gallon conversion (15/(2.25/4.55)*$250 = $7600 to paint a house.
These costs do not account for logistical costs or the economies of scale of implementation.

How Are They Being Used?

The consensus seemed to be that antimicrobial surfaces are beginning to see more usage. I spent a short amount of time investigating this and found some examples:

The Copper Development Associated provides an information site with examples at Atlanta Airport, LA Kings Training Center, and Pullman Regional Hospital.
Several trial applications of concrete blocks with photocatalytic surfaces (titanium dioxide) have been used in Belgium.
At a border control point in Santiago Airport, Chile, a copper surface is used to help prevent infections being spread among the many passengers passing through.
Some gyms have been known to use antimicrobial copper. Anecdotally, my local gym uses antimicrobial copper in their water dispensers.

However, outside of trial applications, it was surprisingly difficult to gather more information on spaces that are regularly used outside of trial applications. I note I did not spend much time investigating this. It is plausible they are being used much more regularly here.

How Else Could They Be Used?

Even though it is unclear how extensively they are being used, one reason to be excited about antimicrobial surfaces is that they may have a number of use cases in addition to pandemic prevention. I think what is most exciting about this is that it may mean the market is well-placed to do much of the work in promoting these, or it may mean that market-shaping mechanisms like an advance market commitment might be appropriate for their further development.

This is especially true for surfaces that also have repellant properties, such as superhydrophilic substances, where being able to repel bacteria but also other contaminants is desirable in a number of contexts. Some other use cases that were mentioned to me include:

Anti-icing.
Use for materials transfer.
Use in food containers.
Anti-thrombotic medical devices to prevent clotting and complications.
Use in space travel.

Other use cases I collected via Google search and LLMs could be:

Medical devices and implants.
Textiles and clothing: antimicrobial fabrics can be used to prevent odour and the growth of harmful bacteria.
Water treatment and purification.
Agricultural equipment and facilities.
Packaging materials: antimicrobial packaging can extend the shelf life of perishable goods and prevent contamination during storage and transport.
Automotive industry: antimicrobial surfaces in vehicle interiors can help maintain cleanliness and reduce odours.
Construction materials.

One expert I spoke to suggested that the market would probably need some assistance for these to be used widely for pandemic prevention. However, there are a number of antimicrobial surface startups^[5], suggesting that at least some number of people feel there could be a market here.

Another expert suggested, however, that many of these use cases require highly unique considerations in practice. This seems right to me: the degree of multipurposeness of these surfaces — both in their use and research methods — seems very unclear and potentially quite contingent right now.

What is the Current State of Research?

With increased concern over antimicrobial resistance and recent developments in nanotechnology, research into novel antimicrobial research is very much ongoing. This includes resolving key knowledge gaps (such as research into non-silver nanoparticles) and future directions for surfaces, such as smart surfaces, surface coatings containing various nanoparticles, nitric-oxide-releasing surfaces, and enabling titanium oxide to be used more readily with visible light.

I note that not all state-of-the-art research uses nanotechnology. One option I looked into in a bit more detail that seemed potentially promising was a sprayable coating derived from cellulose recently produced at the University of Birmingham. A key focus for this product — and many other novel products — is producing sustainable products that do not further damage the environment. One academic additionally mentioned the possibility of using the naturally occurring enzyme bromelain — found in pineapples — as part of an antimicrobial surface coating due to its antibacterial properties.

Various market reports I looked at suggested the antimicrobial surfaces market is a multibillion-dollar industry with quite a high expected compound annual growth rate (CAGR)^[6], noting that I tend to have quite low confidence in these market estimates. Additionally, as mentioned previously, there is a seemingly growing startup scene in this space. These findings reflected the views of two of the experts I spoke to; their impression was that interest in antimicrobial surfaces is still somewhat in the early stages but and rapidly growing. One expert described the field as ‘saturated’, though I do remain less clear on the ways in which this is the case given many research gaps.

What Are the Most Important Open Questions?

A very important theme is a number of questions on the actual mechanisms involved that there seem not to be great studies on. There are quite a few foundational questions we’d want to resolve to be able to assess the feasibility of antimicrobial surfaces for pandemic prevention. These include:

Questions on fomite transmission itself:
1. What is the relationship between contamination level and rate of transmission? How is this affected by pathogen, surface type, and fomite type?
For specific pathogens:
1. What is the rate of transmission on different fomites?
2. What is the minimum viable load required for transmission, illness, and infectiousness?
3. How do various types of pathogens interact with antimicrobial surfaces? According to one academic I spoke to, most work focuses on a selection of priority pathogens, but there is a lot more work to be done on other pathogens. I suspect this is especially true for considering the pathogen profile of a likely GCBR.
Questions on specific surface types:
1. There is still a fair bit to figure out about the actual mechanisms involved, especially in the context of pandemic prevention.
2. Over how long do different surface types degrade?
3. How does degradation affect log reductions? Given most fomite transmission is through droplets, how is this affected by different types of droplets?

All of this with respect to how effective they are at killing microbes is indeed removed from how effective they would be at preventing a pandemic. Plenty of open questions are relevant here, with a couple just being:

How do antimicrobial surfaces interact with built spaces in practice? Higher levels of wear and tear? Would they only make sense in environments where disinfection is widespread already?
How accessible are different types? Are they affordable? What will need to be replaced? What will need to be built from scratch to facilitate use during pandemics?
What is the ideal rate of cleaning? How long will a surface need to last before replacement? What is the maintenance cost? What is feasible during a pandemic?
Supply chain and market considerations:
1. Which surfaces have broader use cases and may be suitable for a market intervention?
2. Which surfaces can be made using local materials?
3. What will be the logistical complexities of producing different surface types?
According to one academic I spoke to, in their view, additional open questions include:
1. What are the manufacturing barriers? Could they be scaled up at a reasonable price?
2. What are the potential safety concerns? How reasonable is it for people to have to be around antimicrobial surfaces?
3. How much of a problem could these be towards contributing towards antimicrobial resistance?
How can we ensure development of surfaces will be sustainable and environmentally friendly?
What are additional ways in which antimicrobial surfaces could be used?

It is unclear whether we want to rely on using antimicrobial surfaces to mitigate pathogen transmission through prolonged, broad-spectrum antimicrobial effectiveness for high-contact surfaces or relegate their use to particular, high-leverage contexts. In either case, it is unclear exactly which surfaces we would use and where. My impression from my interviews is that there is not sufficient understanding of the fundamentals. Ultimately, the upshot of resolving these questions is allowing us to conclude which surfaces would be cost-effective to use in which contexts.

Should We Be Excited About Antimicrobial Surfaces?

All things considered, I quite strongly suspect it is too early stages to be sure either way. These seem to be some of the most salient reasons for and against:

Reasons for:

They have the potential to significantly reduce pathogen transmission via fomites, especially in high-traffic areas.
They could provide continual action without the need for frequent reapplication like disinfectants.
The key counterfactual, relying on disinfection, currently contributes towards health risks, antimicrobial resistance, and may be costlier in the long run.
Many additional benefits beyond infection control (anti-icing, anti-fouling, etc.).
The additional benefits mean there could be lots of market demand for these which would lower the cost of deploying these to mitigate pandemics.
They may be much more flexible than other transmission suppression mechanisms (such as far-UVC), where they could plausibly be used on clothing, medical apparatus, desktops, etc.

Reasons against:

In a hospital (and other contexts, they may be useful), they do not obviate the need for basic removal of soil. Disinfection is likely to occur anyway, and it is unclear to what degree less.
The current high cost and complexity of many novel antimicrobial technologies.
Concerns about inducing antimicrobial resistance with widespread use.
Potential toxicity to humans and the environment from some substances used.
Uncertainty about long-term durability and maintenance requirements.
Many open research questions remain about the real-world effectiveness of pandemic prevention.
Regulatory hurdles and the need to prove safety and efficacy.

My overall conclusion is that research addressing some of the more foundational questions is probably worthwhile. However, I think even this could be debated given that much of this research would have to be expensive, in-field experimentation. I note that even within the handful of individuals I spoke to, there was quite a wide range in the excitement about antimicrobial surfaces, from very negative to very positive.

Antimicrobial surfaces are a kaleidoscopically complicated topic that I have only skimmed the surface of. However, I think the sheer complexity could mask the possibility of low-hanging fruit here. Given the potential multipurpose nature of many of these surfaces, technological advancements driven by the market could lead to tractable interventions down the line. With current technology, I suspect there could be deployment opportunities with outsized impact relative to their cost. Therefore, it seems valuable to continue to investigate the antimicrobial surface space.

Next Steps?

All things considered, my impression is that three robustly good next steps for advancing research on antimicrobial surfaces seem to be:

Resolving the foundational questions for antimicrobial surfaces: the absence of in-field experiments, further lab testing, and further modelling seems to be the primary bottleneck for further investment into antimicrobial surfaces. There has been especially little data gathered on how useful they may be for pandemic prevention.
Producing a complete ontology of antimicrobial surfaces: a full conceptualisation of the different mechanisms, types, modes of action, application, and other properties seems tractable and useful for strategising where to invest efforts. For example, by establishing criteria such as favouring broad-spectrum, low-cost, sustainable approaches, we may only need to focus our attention on a subset of antimicrobial surface types.
More detailed scoping of possible “win states” and use cases for antimicrobial surfaces for pandemic prevention: I think this is an exercise that may also facilitate useful prioritisation about particular surface types, built spaces, and fomites we should be especially interested in.

Oxford Biosecurity Group will be running an 8-week project researching antimicrobial surfaces, focusing on #2, so stay tuned for the announcement of the next cycle. We’re also recruiting for a project co-lead for this project, alongside Kirke Joamets, so please reach out to us at contact@oxfordbiosecuritygroup.com if you’re interested.

Acknowledgements

Acknowledgements to Zhenyu J. Zhang, Sara M. Imani, Tom Ough, Stephanie Dancer, and Andrew Snyder-Beattie for assistance during this project. This project was completed as part of contract work with Open Philanthropy, but the views and work expressed here do not represent those of Open Philanthropy. All thoughts are my own.

Footnotes

^{^}
E.g. Kurt et al., 2007; Widmer et al., 2021; Grass et al., 2011; Kim & Hwang, 2015; Jo et al., 2021; Champagne et al., 2019; Gaw et al., 2017; Rigo et al., 2018; Santos et al., 2022; Fukert et al., 2011.
^{^}
E.g. Wilson et al., 2018, which predicts significant effects on virus infection risk with a 94.1% viral reduction (about a 1.2-log reduction). Or Björkroth, 2018 which reports a 2-log reduction on fomites could reduce infection risk from a single fomite contact to less than 1/1,000,000 for viruses.
^{^}
E.g. Mahanta et al., 2021; Maillard and Hartemann, 2012, and Sheridan et al., 2022 report known unknowns (such as the antimicrobrial efficacy of silver) or novel findings that require further research, such as whether smart hydrogels can be used to provide antimicrobrial benefits without conferring antimicrobrial resistance.
^{^}
See, for example, this source, this source, this source, and this source.
^{^}
E.g. See this search on Venture Radar. Good examples are NoBACZ Healthcare, FendX Technologies, BioFence, LipoCoat, Tractivus, Theradep, and Spartha Medical.
^{^}
For example, GMI, Markets and Markets, Precedence Research, and Grand View Research.

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