As the world is facing health and economic consequences brought on by a global pandemic, the emergence of new infectious agents has become a significant concern. Here, Christian Dianne Oro, mechanical engineer and freelance content writer at materials search engine Matmatch, explains what kind of antibacterial and antimicrobial materials to use to minimise the spread of any viruses. 
The global antimicrobial coatings industry anticipates a sharp increase of demand, as reported by Global Market Insights. The antibacterial materials and coatings market was valued at more than $3 billion in 2017 and it is expected to register a compound annual growth rate of around 12.5 per cent over 2018-2024, reaching $7 billion by the end of 2024.
The development and use of antimicrobial materials are expected to rise due to the stringent measures in place to control the spread of COVID-19 and prevent future outbreaks. Like most of the diseases, infectious agents are spread through airborne droplets produced from sneezing or coughing. These body fluids can settle on surfaces and be transmitted person-to-person if an individual touches these respiratory droplets.
A study conducted by Neely and Maley shows that pathogens like Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococcus can survive on materials used in hospitals for a day, but there are some microbes that can survive for more than 90 days. Viruses generally remain active longer on stainless steel, plastic and similar hard surfaces than on fabric and other soft surfaces.
Antibacterial materials contain antimicrobial agents that are capable of inhibiting or killing microbes on their surface or within their surroundings. They can be antimicrobial polymers, antibacterial plastics, antimicrobial nanomaterials, or antimicrobial ceramics. Irrespective of the material type, they share some specific features: they’re safe to use, cheap and easy to produce, non-toxic and not susceptible to decay, stable for extended periods and offer a broad range of antimicrobial activity.
Antimicrobial polymers
The versatile macromolecular properties of a polymer make it a favourable option against microbial contamination, particularly in the biomedical field. Also known as polymeric biocides, antimicrobial polymers can inhibit the growth of disease-causing microorganisms.
Materials that exhibit antimicrobial action without any refinements and have inherent self-sanitizing properties are called intrinsic antimicrobial materials. Natural polymers as well as polymers with guanidine groups, quaternary nitrogen atoms, halogens and polymers that mimic natural peptides are some of the materials with intrinsic antimicrobial activity.
Some natural polymers include chitosan, heparin and e-polylysine. Chitosan-based materials show promise to be great antibacterial materials due to their biodegradability, non-toxicity, biocompatibility and antimicrobial activity.
Antimicrobial plastics
Alongside natural polymers, engineers could use antimicrobial plastics, which are synthetic polymer materials that contain antimicrobial additives to make them effective against microbial growth. Antimicrobial plastics in commercial use, such as high-chairs, water filters and food storage containers, are more durable than plastics without any antimicrobial active ingredients. The additives blended into thermoplastic and thermoset polymers work to minimise the presence of microorganisms that can make the plastic degrade quicker, further extending the functional lifetime of the material.
Some compatible plastic materials include polypropylene (PP), polycarbonate (PC), polystyrene (PS) and polyethylene (PE/LDPE).
Antimicrobial ceramics
Another antibacterial material is the antimicrobial ceramic, a non-metallic solid material incorporated with an additive within its glaze that makes it resistant to bacterial growth. A study conducted by Drelich et al. shows that a copper-infused ceramic can be ideal for antibacterial products for water disinfection.
Copper compounds have claimed to kill a variety of microorganisms, including bacteria (gram positive and negative), fungi, viruses (enveloped and non-enveloped), yeast and spores. This material can kill 99.9 per cent of harmful bacteria within two hours and keep killing over 99 per cent of bacteria regardless of repeated exposure to the copper surface, according to the Copper Development Association (CDA). Populations of both Klebsiella pneumoniae and Staphylococcus aureus in contaminated water, when exposed to the porous copper-infused antimicrobial ceramic stone, were reduced by >99.9 per cent in 3 hours.
Antimicrobial nanomaterials
Other materials like organic nanoparticles can also eliminate microbes as they can release antimicrobial agents or function as contact-killing cationic surfaces. In an experiment conducted by Jones et al., Poly-epsilon- caprolactone (PCL) was blended with poly(N-Vinylpyrrolidone)-iodine, imparting antibacterial properties to the biomaterials, without changing its mechanical or rheological properties. PCL degradation also promoted anti-adherence of Escherichia coli.
Inorganic nanoparticles are also used as antimicrobial materials, since they are more stable at higher temperatures than their organic counterparts, allowing them to withstand harsh processing conditions.
Metal oxide nanoparticles can also be considered antimicrobial materials because of a physical reaction called electrostatic interaction. Proton leakage induces reactive oxygen species generation which damages organic biomolecules such as lipids, carbohydrates, nucleic acids and proteins, thereby causing microbial death.
One of the most vital applications of the metal nanoparticles, especially silver nanoparticles, is in the biomedical field. Silver nanoparticles have excellent antibacterial properties compared to other metals. The strong bond of silver ions with thiolate groups of proteins and cellular enzymes makes them ideal to produce face masks, private curtains, bandages, wound dressings, bed sheets and other textiles related to healthcare. In 2015, the use of silver in antimicrobial powder coatings accounted for 50 per cent of the industry’s total revenue and is expected to generate $2 billion by 2024.
Today, due to COVID-19, it’s only a matter of time until antibacterial materials, particularly in the surface coatings market, gain more traction as a primary raw material. Moreover, its application in many industries like construction, food packaging, textiles, mould remediation, furniture, kitchenware and automotive will further strengthen its hold in the global market.
If you want to know more about antibacterial and antimicrobial materials, head to Matmatch’s website for more information.
