Evaluation of Antibacterial and Anti-biofilm Properties of Niosome-Loaded Silybum marianum Extract Against Clinical Pseudomonas aeruginosa Strains

Abstract

Introduction: The rising prevalence of multidrug-resistant Pseudomonas aeruginosa and its ability to form robust biofilms has critically narrowed therapeutic options in healthcare settings. Biofilm-associated infections resist conventional antibiotics due to the protective exopolysaccharide matrix and metabolic dormancy of embedded cells. Plant-derived bioactive compounds have emerged as promising alternatives; however, poor aqueous solubility, limited stability, and low bioavailability hinder their clinical use. Niosomes—non-ionic surfactant-based vesicles—enhance pharmacokinetic profiles and enable targeted delivery of phytochemicals. Building on 2023–2025 evidence highlighting the antibiofilm potential of flavonoid-rich plant extracts, this study evaluated niosomal encapsulation of Silybum marianum extract against clinical P. aeruginosa isolates.

Method: S. marianum extract was encapsulated using the thin-film hydration technique at an optimal lipid-to-drug ratio of 20. Physicochemical parameters—particle size, polydispersity index (PDI), and encapsulation efficiency (EE%)—were monitored at 4 ± 1 °C and 25 ± 1 °C to assess stability. Antibacterial efficacy was determined by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays; anti-biofilm activity against preformed biofilms was quantified by crystal violet staining.

Results: The niosomal formulation showed a biphasic, controlled release profile. Storage at 4 ± 1 °C preserved vesicle integrity with minimal changes in particle size, PDI, and EE% compared to 25 ± 1 °C. The encapsulated extract achieved a 2- to 16-fold reduction in MIC and significantly lower MBC values relative to the free extract. The niosomal formulation also eradicated preformed biofilms more effectively than the non-encapsulated extract.

Conclusion: Niosomal encapsulation substantially enhances the antibacterial and anti-biofilm potency of S. marianum extract against clinical P. aeruginosa strains, presenting a viable nanomedicine-based strategy to revitalize the therapeutic efficacy of herbal antimicrobials against biofilm-forming pathogens.

Keywords: P. aeruginosa, S. marianum, Niosome, Biofilm

Competing interests

The authors declare no conflict of interest.