One recent market research project, Clevis Research has been tasked with, considered the sector of antibacterial coating and photodynamic disinfection. Its focus was on the economic complexity of market entry and product implementation. We aimed to find the most promising fields of application for photocatalytic additives in antibacterial coatings and to formulate a market entry strategy for our client TriOptoTec GmbH, a German specialist in developing photocatalytic solutions for self-sanitizing surfaces under the name Dyphox. Based on expert interviews and secondary research, we have analyzed customer pain points, existing substitutes and stakeholders in the value chain to evaluate the market attractiveness for a wide range of potential use cases. We combined those results with the market size and penetration to estimate the market potential of each field of application.
Besides the established use cases in the healthcare industry, awareness for antibacterial retro-coating as a service increases throughout multiple sectors. Covid-19 has a clear impact on that. Photocatalytic self-sanitizing surfaces will be interesting as a complementary strategy to reduce the risk for infections, especially in areas that cannot be cleaned regularly by alcoholic disinfectants. Examples are public transport, schools or even system gastronomy.
PUBLIC HEALTH IN TIMES OF COVID-19
Closing gastronomy facilities, restricting public transport and prohibiting gatherings with friends have been only some of the introduced measures against the spread of Covid-19. In the last months, it has become clear that nearly all of our everyday habits represent in some way a risk for us and others in times of a pandemic. And as Covid-19 has spread, so did our fear of contaminated surfaces. The disease-causing virus SARS-CoV-2 survives up to three days on nonporous surfaces like stainless steel and plastic without proper disinfection.
Given this situation, we ought to think about preventive measures to avoid confinement during the next pandemic. Surely, respiratory viruses like SARS-CoV-2 are mainly spread by coughing and spreading the droplets in the environment: onto other people, clothes, surfaces, and in the air. While the spread of a virus is thus directly linked to each human behaving responsibly, permanent antimicrobial coatings for surfaces can be one more piece in the puzzle of public health security.
ANTIMICROBIAL COATINGS WITH DIFFERENT AGENTS
So-called antimicrobial coatings contain an agent that permanently decrease the number of infectious germs on its surface. Those coatings can either be part of a production process or can be applied as a retro-fit application. Antimicrobial surfaces are already widely used in various settings including clinics, industry, public institutions such as schools, and even within our homes.
Common antimicrobial agents are metal ions, such as copper, silver, and zinc ions. They can be used against a broad range of microbes and are usable in a variety of materials such as in paints, varnishes, plastics. Application fields are water treatment, medical applications, and sanitary facilities.
Though, their natural antimicrobial effect can only be activated in humid environments, as liquids enable the transport of the ions towards the germs. This is why metal ions are effective antimicrobial agents for applications such as wound dressing or urinary catheters. Metal ions are less applicable for antimicrobial coating of surfaces as they tend to be dry. The use of strong disinfectants for surface cleaning can also compromise the antimicrobial effect. Furthermore, bacterial growth only decreases when a threshold concentration has been exceeded. Some strains of bacteria have also been shown to develop resistance to metal-based antimicrobial systems.
It is interesting to know that ancient civilizations, such as the Egyptians, Aztecs, and Greeks, exploited the antimicrobial properties of copper long before the concept of microbes became understood in the nineteenth century. It was observed that water contained in copper vessels was of better quality, i.e. no or little visible slime or biofouling formation, than water contained or transported in other materials.
Biocides, such as benzalkonium chloride, triclosan, isothiazolinone, or chlorhexidine, are poisonous to germs and can thus act as a very effective antimicrobial agent. They are widely used as disinfectants and antiseptics in health care. But, it is important to note that an accumulation of those toxic substances can be harmful to the ecosystem of the human body. Thus, biocides should not be used permanently for the disinfection of surfaces. They also are less effective on dry surfaces.
Ultraviolet germicidal irradiation method
With the ultraviolet germicidal irradiation method, high-energy short-wavelength ultraviolet (ultraviolet C or UVC) light kills or deactivates microorganisms by disrupting their nucleic acid chains and thus their genetic information (DNA). The germs are left unable to perform vital cellular functions. As a chemical-free method, UVC light can be used for the disinfection of water systems. But, exposure to the radiation can cause damage to the eyes and skin. As an antimicrobial agent for surfaces, UVC light can therefore only be applied under specific security conditions.
In addition to the traditional disinfecting agents such as metal ions and biocides, photocatalytic surfaces are being developed and tested for usage in the context of self-disinfecting materials. Photocatalytic materials work by transferring the energy of light, such as sunlight or artificial light, to the surrounding oxygen. Reactive oxygen species (ROS) are generated and kill more than 99% of the microbes on the surface. Currently, there are several photocatalytic additives in use, such as titanium dioxide (TiO2) or zinc oxide (ZnO). Other bio-photocatalysts, such as specific pigments, are being explored and are on their way to market entry as an environmentally friendly, non-metallic, non-chemical and non-toxic disinfection alternative.
One of the big advantages of photocatalytic coatings is the broad range of possible applications and – in comparison to the metal based systems – the good activity under dry conditions. They can be found in all kinds of paints, plastics, ceramics, electronic components along with food and cosmetics. The disinfecting effect of photocatalytic surfaces against well-known bacteria such as the intestinal E.coli and viruses such as influenza have already been scientifically proven. Photocatalysis reacts unspecifically. These are positive news regarding the effectiveness against a broad range of microorganisms and viruses but might become a disadvantage when considering potential reactions with the binding material in the coating or the surface material. That is why detailed testing has to be conducted for every single field of application before commercialization, as toxic intermediates can be formed by reactions with additional chemicals present in the environment such as the air, the surface or binding material. The higher reactivity of the oxygen species can also affect plastic surfaces in the long term. Finally, as photocatalytic additives need sunlight or artificial light to be effective against microorganisms, the human body is also exposed to the UV light. UVA rays enter the tissue of skin and eyes and can cause high damage.
LIMITING FACTORS OF ANTIMICROBIAL COATINGS
Due to drawbacks such as the relatively slow – but permanent – antimicrobial activity and possible leaching of chemicals from the antimicrobial surfaces, there is ongoing research to optimize these systems. Another limiting factor is the expected lifetime of a given coating. While factory-applications have a longer product life than retroactively applied coatings, heavy use or even damage of the surface can shorten both. That’s why it is important to underline that proper cleaning and handwashing remain the best ways to prevent infections. Nevertheless, an antibacterial coating can close hygiene gaps between disinfection cycles. It can be seen as a complementary hygiene measure to reduce the spread of germs. This is especially interesting for surfaces that are frequently touched by a lot of people or exposed to an increased microbial load due to its environment, e.g. in hospitals and medical practices.
by Meike Winkler
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