The biofilm challenge and the search for new solutions

Bacterial biofilm formation is a major obstacle to effective infection management, particularly in non-healing chronic wounds. Biofilms are estimated to be present in approximately 80% of human infections, and bacteria within them can exhibit resistance levels up to 1000 times higher than planktonic cells. With the global rise of antimicrobial resistance, conventional therapies are increasingly ineffective, prompting the search for fundamentally new treatment strategies. A comprehensive review published in Current Research in Pharmacology and Drug Discovery (2026) addresses the current state of this field [1], and its key points are summarized in this editorial note.

Biofilm development occurs in stages: attachment, microcolony formation, maturation, and dispersion. After adhesion, bacteria begin producing an extracellular polymeric substance (EPS) matrix that provides structural stability and protects microorganisms from external factors. In chronic wounds, biofilms are often polymicrobial, and interactions between species further enhance their resilience.

Biofilm-associated resistance arises from multiple mechanisms [2]:

• limited penetration of antimicrobials through the matrix;
• metabolic heterogeneity with the formation of persister cells;
• horizontal gene transfer—the exchange of genetic material between bacteria, accelerating the spread of resistance genes within the community;
• efflux pump activity—specialized protein systems that actively expel antimicrobial agents from bacterial cells, preventing them from reaching their targets;
• enzymatic inactivation of drugs.

In addition, quorum sensing plays a key role in coordinating bacterial community behavior. Together, these factors sustain chronic inflammation and delay wound healing.

Membrane-active antimicrobials: mechanisms of action

As an alternative to conventional antibiotics, membrane-active antimicrobials (MAAs) are being explored—compounds that kill bacteria regardless of their metabolic activity. This is particularly relevant for targeting biofilm-embedded cells in a low-metabolism state.

MAAs include antimicrobial peptides (AMPs), peptidomimetics, and other compounds that disrupt bacterial membrane integrity. Their cationic charge enables binding to teichoic acids in Gram-positive bacteria and lipopolysaccharides (LPS) in Gram-negative bacteria, while hydrophobic domains facilitate membrane insertion and destabilization.

Several models of action have been described:

• Barrel-stave model — MAAs insert into the lipid bilayer and assemble into structured transmembrane channels. The inner surface of these pores is lined with antimicrobial molecules, leading to ion and cellular content leakage.
• Toroidal pore model — MAAs induce curvature of the lipid bilayer, forming pores composed of both antimicrobial molecules and lipid head groups. This disrupts membrane integrity, allowing uncontrolled molecular transport.
• Carpet (detergent-like) model — MAAs accumulate on the membrane surface and, upon reaching a threshold concentration, destabilize it in a detergent-like manner, resulting in membrane disintegration into micelle-like structures and cell death.

All of these mechanisms increase membrane permeability and lead to bacterial death. Importantly, MAAs also interfere with adhesion, disrupt the biofilm matrix, inhibit quorum sensing, alter bacterial motility, regulate biofilm-related gene expression, and act against persister cells.

Chemical diversity and representative compounds

MAAs encompass a wide range of natural and synthetic compounds. Natural sources include polyphenols, flavonoids, essential oils, and molecules produced by bacteria, fungi, and marine organisms. Synthetic MAAs include small molecules, antiseptics, and engineered peptides.

Quercetin has been shown to reduce biofilm biomass, disrupt biofilm structure, suppress EPS production, and downregulate virulence genes in Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA) [3]. Cannabigerol has demonstrated the ability to inhibit biofilm formation, eradicate mature biofilms, and eliminate persister cells in MRSA [4].

Compounds targeting virulence rather than viability are also of interest. For example, dihydropyrrol-2-one derivatives inhibited quorum-sensing pathways by more than 70%, thereby reducing virulence factor production [5].

Antimicrobial peptides and their analogs show strong anti-biofilm activity. The peptide A24 reduced early biofilm formation in Staphylococcus aureus by up to 92% and affected persister cells by disrupting membranes, causing ion leakage, and inducing metabolic changes. Other peptides similarly inhibit biofilm formation and impair bacterial motility, limiting colonization.

Pharmaceutical innovations and delivery systems

Despite their promise, clinical application of MAAs is limited by instability, degradation, and low bioavailability. Therefore, advanced delivery systems are being developed to enhance their performance.

These include:

• Nanostructured delivery systems — nanoparticles and nanocomplexes that protect active compounds, enable controlled release, and improve penetration into biofilms due to their small size and high surface area.
• Chitosan-based hydrogels — polymer matrices that retain active agents at the application site, prolong contact with tissues and microbial surfaces, and may create unfavorable conditions for bacterial growth.
• Liposomes — lipid-based vesicles that encapsulate active molecules, improve stability, enhance interaction with bacterial membranes, and facilitate tissue and biofilm penetration.
• Microneedle systems — minimally invasive platforms that deliver active compounds directly into tissue and biofilms, bypassing surface barriers and enabling localized action.

For example, a zeolitic imidazolate framework-based system loaded with curcumin demonstrated antibacterial activity and reduced biofilm formation by disrupting membranes. Chitosan nanoparticles loaded with LL37 inhibited biofilm formation by approximately 68% and downregulated biofilm-related genes. Microneedle systems have shown effective biofilm disruption in skin models.

Applications in medicine and cosmetology

Although many membrane-active antimicrobials are still under investigation, several compounds with similar mechanisms are already widely used in clinical practice and skincare.

In surgery and dermatology, chlorhexidine is one of the most established examples. This antiseptic disrupts bacterial membranes and is widely used for wound care, surgical site preparation, and infection prevention. Its efficacy can be enhanced by advanced delivery systems, such as liposomes and hydrogels, thereby improving biofilm penetration and prolonging activity. Other membrane-active agents include polymyxins and gramicidin C, commonly used in topical formulations for infected wounds and burns.

In cosmetology, interest in these compounds is driven by their ability to modulate the skin microbiome and manage biofilm-associated conditions such as acne and inflammatory dermatoses. Polyphenols, particularly quercetin, can disrupt biofilm structure and suppress microbial virulence, complementing their antioxidant and anti-inflammatory effects. Essential oils (e.g., tea tree, thyme) contain lipophilic components that interact with bacterial membranes and are widely used in products for acne-prone skin.

Excipients such as chitosan also play an important role as delivery platforms, enhancing retention of active ingredients on the skin, prolonging their action, and potentially contributing to antimicrobial effects through interactions with microbial surfaces.

Overall, existing medical and cosmetic applications demonstrate the practical relevance of membrane-targeting strategies. At the same time, advances in delivery systems continue to expand the therapeutic potential of both established and emerging agents.

References

1. Hemmingsen L.M., Skalko-Basnet N. Breaking biofilm barriers in skin wounds: membrane-active antimicrobials in an era of resistance. Curr Res Pharmacol Drug Discov 2026; 10: 100249. https://doi.org/10.1016/j.crphar.2025.100249
2. Cotten K.L., Davis K.M. Bacterial heterogeneity and antibiotic persistence: bacterial mechanisms utilized in the host environment. Microbiol Mol Biol Rev 2023; 87(4): e00174-22.
3. Vijayakumar K., Ganesan V., Kannan S. Antibacterial and antibiofilm efficacy of quercetin against Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus associated with ICU infections. Biofouling 2025; 41(2): 211–224.
4. Farha M.A., El-Halfawy O.M., Gale R.T. et al. Uncovering the hidden antibiotic potential of cannabis. ACS Infect Dis 2020; 6 (3): 338–346.
5. Suresh D., Yu T.T., Kuppusamy R. et al. Novel cationic dihydropyrrol-2-one compounds as antimicrobial agents and quorum-sensing inhibitors. Bioorg Med Chem 2025; 122: 118137.