Nanoemulsions: Synergy Between Intrinsic Antibacterial Activity and Antimicrobial Drug Delivery- A Review

Background: Antimicrobial resistance (AMR) represents one of the most critical global developmental and public health problems of the modern era. One of the major contributors to multidrug-resistant bacteria (MDR) is biofilm formation, which is the leading cause of chronic infections. Nanoemulsions (NEs)—defined as kinetically stable colloidal dispersions with droplet sizes typically ranging from 20 to 200 nm—have emerged as one of the most versatile platforms for the delivery of antimicrobial drugs over the past two decades.   Aim: This review critically evaluates the antibacterial mechanisms of both drug-free and drug-loaded NEs, highlighting their dual roles as intrinsic antimicrobial agents and advanced delivery systems that enhance antibiotic efficacy. It further emphasizes the importance of their physicochemical characteristics and underlying mechanisms of action, with particular focus on their potential to address the challenges associated with MDR pathogens. Methods: To achieve this aim, a comprehensive search was conducted across the ScienceDirect, Springer, PubMed, ResearchGate, National Institute of Health (NIH), CrossRef, and Google Scholar for studies published from 1999 to 2026. The final search was performed on April 3, 2026. Results: Evidence indicates that drug-free NEs exert intrinsic antibacterial effects via membrane disruption and biofilm penetration. While drug-loaded NEs serve as advanced delivery platforms that optimize solubility and stability, yielding synergistic therapeutic outcomes. Conclusion: NEs represent a significant advancement in antimicrobial therapy due to their dual functionality. They combine inherent antibacterial properties with a high capacity for delivering multiple agents. This ability to load several antibiotics or bioactive substances at once enables powerful synergistic effects that can overcome traditional resistance mechanisms. With their ease of preparation and versatility for co-delivering multiple drugs in various dosage forms, NEs are valuable nanostructured platforms that hold great promise in addressing the global challenge posed by MDR pathogens.