Encapsulation nanoarchitectonics of glabridin with sophorolipid micelles for addressing biofilm hazards via extracellular polymeric substance permeation and srtA gene suppression

Background: Biofilm, a common drug-resistant phenotype of Staphylococcus aureus (S. aureus), demonstrates significant drug resistance and recurrence due to its extracellular polymeric substance (EPS) barrier and subsequent bacterial migration. Hence, there is an urgent need for effective solutions to mitigate the hazards posed by biofilms. Result: This study developed a stable, low-toxicity multifunctional nanomicelle, GLA@SOL/EYL, by encapsulating glabridin (GLA) using sophorolipid (SOL) and egg yolk lecithin (EYL). Optimizations were performed for the hydration medium, the ratio of carrier materials to GLA, and EYL additions. GLA@SOL/EYL exhibited a particle size of 122.1 ± 0.8 nm and a surface potential of −66.4 ± 1.7 mV, endowing it with the ability to permeate biofilms EPS effectively. GLA@SOL/EYL encapsulated 98.3 ± 1.2 % of GLA and demonstrated a slow-release effect, significantly enhancing the bioavailability of GLA. The addition of EYL reduced the hemolytic toxicity of GLA@SOL/EYL and improved its encapsulation rate and stability. GLA@SOL/EYL reduced the minimum inhibitory concentration of GLA to 8 μg/mL and extended its inhibitory effect at low concentrations by rapidly disrupting the structural integrity of S. aureus. GLA@SOL/EYL may penetrate biofilms to disperse EPS and remove twice as much biofilm as GLA alone, thereby eliminating 99.99 % of S. aureus within biofilms, compared to 99 % bactericidal efficacy of GLA. Additionally, GLA@SOL/EYL inhibited 63.8 ± 1.8 % of biofilm formation by affecting the expression of the srtA gene, thereby reducing the expression of cell wall-anchoring protein genes. In contrast, the biofilm inhibition rates of GLA and blank micelles were less than 10 %. Conclusion: GLA@SOL/EYL utilizes the nanoparticle effect to penetrate biofilms and deliver antimicrobial GLA. The SOL disperses the biofilm matrix while GLA is released to kill S. aureus, preventing bacterial dissemination and colonization. Thus, GLA@SOL/EYL presents an innovative strategy for effectively eradicating S. aureus biofilms and preventing new hazards in a one-step approach.