Functionalized carbon nanoparticles for plumbagin delivery: Physicochemical characterization, antibacterial activity, and molecular docking

Bacterial biofilms play a critical role in chronic wound infections by significantly delaying wound healing. Staphylococcus aureus, one of the most prevalent biofilm-forming pathogens, secretes extracellular polymeric substances that effectively protect it from host immune defenses and antibiotic treatments. To address this challenge, nanoscale antibacterial strategies have attracted increasing attention in recent years. By encapsulating antibacterial agents within nanocarriers, drug penetration into biofilms can be enhanced, thereby improving bioavailability. In this study, we synthesized bovine serum albumin-functionalized carbon nanoparticles (CB) via the functionalization method. The antibacterial agent plumbagin (PLB) was subsequently loaded onto them to form nanocomposites (CB-PLB). We comprehensively characterized their physicochemical properties, including particle size, polydispersity index, morphology, drug-loading efficiency, thermal behavior (differential scanning calorimetry, DSC), crystallinity (X-ray diffraction, XRD), spectroscopic features, solubility, and in vitro drug-release profiles. Specifically, we examined the impact of CB-PLB on both biofilm formation and established mature biofilms of Staphylococcus aureus. In comparison to PLB, CB-PLB showed better antibacterial and anti-biofilm activity against formed and matured biofilm using crystal violet staining and XTT assay. High-content screening imaging analyses confirmed that CB-PLB exerted potent disruptive effects, including reduction of biomass, mean thickness, and alteration of biofilm roughness. Furthermore, molecular docking analysis confirmed specific interactions among carbon nanoparticles (CNP), PLB, and bovine serum albumin (BSA). These findings highlight the synergistic interaction between CB and PLB, suggesting that CB is a promising nanocarrier for hydrophobic antibacterial agents.