The COVID-19 pandemic has highlighted just how easily pathogens can be transmitted from surfaces and has made it necessary to use chemical agents for continuous, thorough disinfection. Besides the use of many different products, this practise also depends on operator performance and quality. The need to develop surfaces capable of killing or repelling pathogens is therefore a key part of infection control, especially for plastics.
In terms of promoting products that can form part of the circular economy, one approach involves using carbon-based nanomaterials and bio-based antimicrobial products, whereas considerable interest has also been shown in different application sectors in the shift away from common additives such as metal ions and oxides of silver, copper and titanium, which are under scrutiny due to their possible toxicity and disposal issues.
Carbon-based nanomaterials are known for having several properties, including electrical conductivity, mechanical strength and thermal conductivity. Recently, however, they have been found to possess strong bactericidal properties. Their antibacterial mechanism is complex and depends on factors such as composition and surface concentration, but they appear to be able to act on cell membranes and destroy them and/or cause oxidative stress, as in the case of silver-based nanomaterials. Because these materials can act on contact without releasing substances, they are suitable for medical applications such as prostheses and implants in constant contact with the body.
Natural antibacterial agents derived from extracts of animals, plants and microorganisms are generally considered safe, healthy and environmentally friendly. Natural antimicrobial peptides such as nisin, natamycin, leucocin, enterocin and pediocin are recognized biopreservatives that are used to inhibit and kill pathogens and bacteria that can cause food spoilage. Because they are composed of proteins, they are sensitive to high temperatures, making them difficult to use in thermoplastic compounds. However, they can be encapsulated in porous inorganic or heterostructure (inorganic/organic hybrid) matrices to make them more resistant to high-temperature processes.
Chitosan is one of the most intensively researched and used biopolymers for food coating and packaging and has excellent antimicrobial properties. It is the most abundant polysaccharide in the world and is also biodegradable and biocompatible. Chitosan is becoming increasingly important as an antimicrobial additive in plastic applications and its derivatives are widely used as natural alternatives to antibacterial and antioxidant agents, especially in food contact applications.
Antimicrobial compounds have applications in a wide range of technology industries, such as protection of crops from pest infestations in agriculture and the search for solutions in healthcare.
In the agricultural sector, there is great interest in developing bio-based antimicrobial technologies and finding new applications for them, given that inappropriate application and storage of their synthetic counterparts often lead to contamination of plant tissues, as well as contamination of the air, water and soil. Moreover, the presence of pesticides can increase the development of tolerance, resistance, persistence of the microbiomes of these environments and even their ability to degrade these pesticides. It has been observed that it is difficult for biobased materials to develop antimicrobial resistance (AMR), so their activity is assured over time.
AMR is and will be a very important issue for hospitals and the healthcare sector, as indicated by the WHO when it included AMR as one of the 10 global public health threats that humanity will have to face in the coming decades. Developing new antimicrobial materials that do not allow bacteria and other microbes to generate resistance is a key area for future development in the medical sector.