Antimicrobial Coatings: What They Are & How They Work

Antimicrobial coatings are a specialized surface modification intended to inhibit the growth of various types of microorganisms, including bacteria, viruses, and fungi. These coatings are now becoming an integral part of products in industries ranging from health care to manufacturing. They are used to promote hygiene, safety, durability, and greater functionality. Antimicrobial surface coatings are applied as antimicrobial protection layers for stopping the growth of harmful microorganisms. They can be applied to all types of surfaces, thereby improving a product’s resistance to contamination and microbial damage. This article will provide insight into the different types, applications, benefits of these coatings. We also look at new innovations in antimicrobial coatings and their transformative effects on various industries.

Types of Antimicrobial Coatings

These coatings can be grouped into two main categories, permanent (surface-bonded) coatings and leaching coatings. We discuss each of these in more detail below.

1. Permanent or Surface-Bonded Non-Leaching Antimicrobial Coating

Surface-bonded, non-leaching antimicrobial surface coatings are becoming increasingly popular. This is because of their ability to provide long-lasting protection against microbial contamination. This type of antimicrobial coating is notably different from leaching versions that become ineffective over time. Surface-bonded versions are non-leaching. In other words, they do not release (leach) active agents into the environment. Instead, they are permanent coatings that chemically bond to a surface by forming covalent bonds.¹ They work by permanently inhibiting bacterial adhesion to the surface of the product. 

These coatings are designed to kill or inhibit the growth of microorganisms upon contact. They do this by piercing the cell wall and impairing the life cycle of the microorganisms. As a result they help prevent the formation of biofilm and with it the possibility of infection. This type of antimicrobial coating is especially useful in health-oriented and industrial applications,² such as medical devices. This is because of the coating’s durability, effectiveness, and environmental friendliness. 

2. Leaching Antimicrobial Coating

Leaching antimicrobial coatings release active antimicrobial agents from their surfaces into the surrounding environment. Common anti-bacterial agents used in these coatings include silver ions and iodine. The surface coatings gradually release the agents over time. 

These coatings are used in applications such as medical devices, food packaging, and various surfaces that are regularly exposed to microbial contamination. And the coatings require leaching on a continuous basis.³ 

Silver and copper antimicrobial coatings often fall under this category. Silver ions damage microbial cell walls, making silver coatings quite effective in medical and industrial settings.^4,5 

However, this category of antimicrobial coatings does pose some issues. First, the use of this type of coating raises environmental concerns associated with leaching antimicrobial agents and the potential development for antimicrobial resistance. Second, they have issues with long-term effectiveness. This is because the leaching antimicrobial agent is eventually exhausted. And this, of course, leaves the surface coating ineffective.

Antimicrobial Clear Coat

Antimicrobial agents incorporated into clear coatings prevent microbial growth and biofilm formation and reduce the likelihood of infections and contamination. Antimicrobial clear coatings are formulated by formulation of acrylic polymers and metallic nanoparticles, such as silver.⁶ 

Clear coatings are transparent and versatile coatings that will not take away from the aesthetics of surfaces. At the same time they will add antimicrobial protection. This helps particularly in places where hygiene is of utmost importance, such as health care facilities, food processing areas, and other public spaces. It can also be important when coating products, such as medical devices where the appearance cannot be altered. 

Application Methods

Antimicrobial coatings can be applied using various methods. The specific application method depends on the substrate, the intended use, and other factors.  Regardless of the application method used, the coating needs to be properly prepared and cured for it to be effective. 

Some of the most popular application methods are discussed below. 

1. Antimicrobial Spray Coating

This method provides uniform coverage and is recommended for surfaces requiring relatively frequent or large-scale application. Variation in spray coating method includes traditional aerosol sprays to the extreme cold spray, to thermal spraying.

The cold spray in particular has garnered great interest because antimicrobial coatings can be deposited at lower temperatures without altering the effectiveness or requirements of the antimicrobial agents.^7,8

2. Antimicrobial Powder Coatings

These coatings are electrostatically applied and heat cured to form a durable antimicrobial surface treatment. Application of antimicrobial powder coatings is performed with various techniques like electrostatic spray deposition and thermosetting processes. Such techniques create a uniform and durable coating sufficiently bonding with various substrates.^8,9

3. Other Application Methods for Antimicrobial Coatings

There are other application methods in addition to spraying and powder coatings as well. These include:

• dipping
• brushing
• chemical vapor deposition

Common Uses of Antimicrobial Coatings

Industrial Applications^10-14

These coatings are used in a wide range of industrial applications. Some of the many industrial applications for antimicrobial coatings are discussed below. 

1. Antimicrobial Floor Coating
   • Antimicrobial floor coatings are common in food processing facilities, hospitals, clean rooms, certain manufacturing facilities, etc. These coatings ensure hygienic surfaces and minimize contamination risks.
2. Antimicrobial Duct Coating
   • Antimicrobial duct coatings are used in HVAC systems tp prevent microbial growth, improve air quality, and reducing maintenance costs.
3. Stainless Steel Equipment
   • Antimicrobial coatings are widely used in kitchen equipment, medical instruments, and industrial machinery to enhance durability and cleanliness.
4. Paper and Textile Industry
   • Antimicrobial paper coatings are also used in packaging and printing. They help extend the shelf life of products and maintain hygiene.
   • Antimicrobial coatings also control the microbial infestation and protect textiles.
5. Plastic Industry
   • Plastics treated with antimicrobial coatings are used in various industries where health and safety is critical, such as healthcare, automotive, and consumer electronics.

Medical Applications^15-19

Antimicrobial coatings are critical in medical and health applications. Medical coatings with this function help to combat bacterial growth, protecting against diseases and contamination. 

1. Antimicrobial Coatings for Medical Devices
   • These coatings minimize the risk of infections associated with implanted or external medical devices. They do this by preventing the growth/colonization of bacterial microbes on the surfaces of the devices.
2. Antimicrobial Dressings
   • Antimicrobial coatings are effective in wound care, promoting healing and preventing infections.
3. Antimicrobial Catheter Coatings
   • These coatings reduce the incidence of catheter-associated urinary tract infections.
4. Antimicrobial Coating for Plastic in Healthcare
   • Plastics used in medical equipment are often surface treated with such coatings to maintain sterility and prevent the spread of diseases.

Hydromer™ Provides an Edge in Performance and Versatility

Hydromer, Inc. is a well-established medical coating manufacturer specializing in innovative antimicrobial coating solutions. Our company focuses on developing advanced, hydrophilic coatings that serve multiple industries, offering distinct advantages in both performance and durability. 

Core Features of Hydromer Bonded Antimicrobial Coatings

Hydromer formulates surface-bonded, non-leaching antimicrobial coatings designed to inhibit microbial colonization. Our permanent antimicrobial coatings adhere chemically to the surface, meaning they do not leach antimicrobial agents out to their surrounding environment. 

Instead they offer long-lasting protection. Unlike leaching coatings that eventually become ineffective, our surface-bonded coatings physically disrupt the bacterial cell wall. This results in distorting cellular mechanisms and life cycle of the cell. The result is a stable, wall piercing coating that reduces the potential for bacterial colonization. 

Our coatings are custom formulated. As a result, they can also be designed to be lubricious, and/or allow for drug elution. 

Competitive Advantages of Hydromer Bonded Antimicrobial Coatings

Hydromer’s surface-bonded, non-leaching antimicrobial coating have been tried and tested against various competitive products and technologies. Following are some of the key advantages that Hydromer antimicrobial surface coatings offer.

1. Longer Efficacy than Conventional Antibiotic Coatings

Conventional antibiotic coatings leach the active ingredients. While effective at first the leaching agents are eventually depleted. This results in the coatings becoming ineffective. 

Our Hydromer Antimicrobial Coating will not be absorbed or consumed by micro-organisms. This allows the effectiveness of our coating to remain for the life of the coating itself. 

2. Non-Leaching Antimicrobial Action Protects Medical Devices and Patients

Hydromer Bonded Antimicrobial Coatings are bonded to the surface, without any side effects and/or secondary toxicity. They work without leaching any ingredients. In comparison conventional coatings that leach antibiotics which depletes the active ingredients.

3. Extended Inhibition of Bacterial Colonization:

Hydromer’s bonded antimicrobial coatings have demonstrated superior antimicrobial activity in bacterial colonization tests. Competitive coatings often rely on agents like silver ions or antibiotics. While initially effective the agents become depleted over time and become ineffective. 

Bacterial Colonization Testing and Results

Samples of polyurethane substrate were coated with Hydromer antimicrobial coating. Samples of non-coated polyurethane were tested as well. The samples were placed in phosphate buffer solution and evaluated for 56 days. 

The study included pathogens such as Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermidis.

Hydromer’s antimicrobial coating provided durability and remained effective even after prolonged exposure. No bacterial growth was observed for 56 days. In comparison, the non-coated samples showed significant bacterial overgrowth.

Even under exposure to organic materials (e.g., proteins from egg white), Hydromer coatings maintained their efficacy, showcasing robust resistance to biofouling.

Activity Testing and Results

Samples of polyurethane substrate were coated with Hydromer antimicrobial coating. As a comparison samples were coated with competitive antimicrobial coatings. 

The study tested the coatings against Staphylococcus aureus. The samples were submerged for four weeks. The results are shown in the figure below.

4. Non-Cytotoxicity

During testing, human fibroblast cells exposed to Hydromer’s coatings exhibited no adverse effects, further validating their biocompatibility for medical applications. 

The cytotoxicity text was performed using murine fibroblast cells. Samples coated with Hydromer Bonded Antimicrobial Coating does not show any leaching and the cells survive. In other words, our coating showed the ability to inhibit bacterial growth while causing no harm to the cells in contact with our coating. 

The competitor’s coating was a conventional, leaching coating, not surface-bonded like ours.These coatings have cytotoxicity due to the leaching of antimicrobial agents, causing systemic toxicity. The use of these leaching coatings resulted in 100% cell death, highlighting its cytotoxicity for the surrounding environment. 

Hydromer Goes Above and Beyond Custom Antimicrobial Coatings

Our antimicrobial coatings are custom formulated. Our experts work with your team to develop a coating that will meet your specific goals and requirements. In addition to custom formulation, we offer a wide range of services. These include technical and regulatory consulting, technical support, R&D services, technology transfer, contract coating services, and analytical testing. 

Here are some of the key benefits of working with Hydromer to develop your antimicrobial coating:

• Hydromer provides tailored antimicrobial coating solutions for various substrates, including glass, metals, and a wide range of polymers.
• We can custom formulate coatings for medical devices (e.g., catheters, stents, surgical tools, implants), industrial surfaces, and high-touch consumer products.
• Coatings can be client-specific and designed with added functionalities, such as lubricity, protein resistance, or integrated drug delivery.
• Hydromer’s antimicrobial testing services ensure that your coatings meet strict performance, safety and regulatory criteria, providing customers with reliable, validated solutions.
• Once the coating is formulated we can help you transfer the technology to your facility. Alternatively, we offer contract coating services. 

Antimicrobial Coating: An Innovative Approach to Hygiene and Durability

Antimicrobial coatings are not merely a technological innovation; they represent a paradigm shift in how industries approach hygiene, safety, and durability. From hospitals and health care to manufacturing plants, these coatings are transforming surfaces into active barriers against microbial threats. In turn, they are helping to reduce risks of contamination and the spread of infection. Coatings manufacturers, such as Hydromer, are investing in research and development to advance these coatings and stay at the forefront of innovation. 

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