The combination of multiple antimicrobial compounds, such as metallic ions with polymers, is emerging as including preference for surface coatings, food packaging and hand washes. Frost & Sullivan believes opportunities for antimicrobial technologies in the consumer health industry will depend on finding the ideal combination of multiple microbicidal platforms. Read about the latest developments.
While metallic ions continue to be among the most potent antimicrobial technology platforms, several new innovations across antimicrobial polymers, peptides and naturally sourced agents will lead the global consumer health landscape.
Apart from conventional consumer healthcare application areas such as medical device and implant coatings, antimicrobial technologies are likely to be used more for novel applications including textiles and cosmetic preservatives.
Chelates are potent antimicrobial agents. Typical metallic ions used include silver, copper, zinc, gold, palladium, titanium and selenium. Two chemical company favorites are silver and copper, which are frequently used for antimicrobial applications. Silver functions by interacting with thiol groups in microbial proteins and enzymes. The interaction releases potassium ions, damaging the bacterial cell membrane and leading to bacterial death. Copper ions are known to damage bacterial membrane proteins and induce hydroxyl radical formation, which eventually leads to membrane damage, oxidative stress and cell death.
These chelates easily dissociate to release bioactive metal ions, but tend to be more toxic and less stable than their organic counterparts: sulfonamides containing ferrocene. Growing microbial resistance mechanisms inhibit the antimicrobial functions. The frequent use of silver has caused Salmonella species to develop a resistance. However, organic metal salts and metallic polymers do not dissociate easily in microbial environments, and may be less effective than inorganic salts.
Effective against a broad spectrum of microorganisms such as bacteria, fungi and viruses, chelates are used in catheters, implants, endoscopes and other touch surfaces. Uses in other industries include food-grade metal coatings, HVAC systems, metal cladding and paints.
The most frequently used polymeric coatings for antimicrobial applications include polycarbonate, polyurethane, polyvinylpyrrolidone, polyphosphoester, polyether ether ketone and polymethyl methacrylate, which may be combined with an active antimicrobial component such as quaternary ammonium salt and/or quaternary phosphonium salt to enhance microbicidal properties.
Because most bacteria are negatively charged, bacterial cells readily absorb cationic polymers. This disruption of cell membrane causes the bacterial DNA to leak, causing cell death. Antimicrobial polymers with longer alkyl chains have greater microbicidal functions.
These polymers can be found in surgical tools, needles and pacemakers. Other industries also use them, including military and aerospace—but that’s classified.
Amphipathic Nature of Antimicrobial Peptides
Antimicrobial peptides (AMPs) constitute a significant component of the natural defense systems in plants and animals to inhibit pathogenic invasion. Peptidomimetic systems with antimicrobial functions offer a biodegradable alternative for antimicrobial applications. AMPs are not only emerging as preferred pharmaceutical ingredients, but are also becoming more important as coating materials for a wide range of non-pharmaceutical applications.
AMPs function by disrupting microbial cell membranes and are always microbicidal. Their amphipathic structures facilitate interaction with microbials—a property that researchers are studying at the University of British Columbia in Canada, the University of Coimbra in Portugal, and the University of Minnesota.
Antimicrobial Quaternary Ammonium Compounds
Antimicrobial quaternary ammonium compounds (QACs) generally include benzethonium chloride, benzalkonium chloride (no relation), cetylpyridinium chloride and tetraethylammonium bromide. These completely easy-to-pronounce QACs are usually derived by the alkylation of tertiary amines with halocarbons. Such compounds are highly stable and resistant to oxidation.
QACs with long alkyl chains are known to exhibit antimicrobial functions by enabling cell membrane disruption, lysis and apoptosis in microbial cells. They are most effective against amoeba, bacteria, fungi and enveloped viruses. Because of QACs’ broad spectrum, U.S. companies such as Viachem Limited, SACHEM Inc. and Ecolab are using them in applications ranging from hospital disinfectants to asphalt emulsification.
Biguanides and Amidines
Frequently used biguanide and amidine disinfectants include chlorhexidine, hexamidine, dibrompropamidine, propamidine and polihexamethylene biguanide (PHMB). These compounds and their various combinations offer enhanced antimicrobial functions because of the presence of a polymer in the compound.
Biguanide and amidine compounds function primarily through cell membrane disruption. They bind to microbial cell membranes, leading to subsequent cell lysis and apoptosis of microbial cells. PHMB is known to be effective against gram-negative bacteria including Enterobacteriaceae, Staphylococcus aureus, Pseudomonas Aeruginosa and E.coli. Biguanides and amidines are also effective against a wide variety of amoeba, fungi and yeasts. Industrial applications include surgical instrument sterilization, wound dressings, underarm deodorant, vascular catheters and water sanitization.
Phenolic Compounds and Aromatic Alcohols
Phenolics typically consist of hydroxyl derivatives of benzene rings and are often used for antimicrobial and disinfectant applications. Phenolic compounds and their derivatives usually include compounds such as triclosan, phenol, hexachlorophene, policresulen, biphenylol and chloroxylenol—all aromatic alcohols.
Phenols are effective against gram-positive bacteria through protein denaturation and cell membrane disruption. The outer membrane of gram-negative bacteria functions as a protective barrier against hydrophobic phenols. However, certain studies have highlighted a mutagenic function of phenols after noticing that mutant bacterial strains were unable to repair their DNA, making them highly sensitive to phenolic disinfectants.
Active manuka honey is used for its bactericidal properties against antibiotic-resistant bacteria in infected wounds. Curcumin or turmeric nanoparticles are effective for burn wound infection and other cutaneous injuries. Other natural antimicrobial compounds include garlic, basil, acidophilin, chitosan, defensin and colicin.
Curcumin induces cellular damage of methicillin-resistant Staphylococcus aureus. Plant members of the Allium family, such as garlic and onion, generate a potent antimicrobial called allicin when they become physically damaged or stressed. Natural antimicrobials are an effective alternative for consumers wanting a natural skin disinfectant or other product.
The Road Ahead
Nitrofurans, acridines and hydrogen peroxide have been used for disinfectant applications. However, the combination of multiple antimicrobial compounds, such as metallic ions with polymers, is emerging as including preference for surface coatings, food packaging and hand washes.
Frost & Sullivan believes opportunities for antimicrobial technologies in the consumer health industry will depend on finding the ideal combination of multiple microbicidal platforms. Innovations are likely to be in the use of antimicrobial peptides as used in dental implants and food packaging, as well as natural biocides.
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