Antibacterial and Biofilm-Targeting Performance of Cefuroxime Axetil-Loaded Eudragit® Nanoparticles

Background/Objectives: Cefuroxime axetil (CA) is a poorly water-soluble second-generation cephalosporin. This study aimed to develop CA-loaded Eudragit® RS100/RL100 nanoparticles (NPs) and investigate the influence of polymer composition and drug-to-polymer ratio on their physicochemical, antibacterial, and antibiofilm properties. Methods: Six CA-loaded NPs (NP-1–NP-6) were prepared using nano spray drying with Eudragit® RS100, RL100, or their 1:1 mixture at drug-to-polymer ratios of 1:1 and 1:2. Particle characteristics, drug content, and structural properties were evaluated. Antibacterial activity was assessed using agar well diffusion, broth microdilution, and time-kill assays, while antibiofilm activity against pre-established Staphylococcus aureus and Escherichia coli biofilms was determined using crystal violet staining. Additional analyses included drug-content-normalized MIC, MIC-normalized time-kill exposure, and concentration–response area under the curve (AUC). Results: All drug-loaded NPs retained antibacterial activity and reduced established biofilm biomass, whereas blank NPs showed no detectable activity. FT-IR and 1H-NMR analyses indicated no evidence of new covalent interactions. Free CA exhibited greater planktonic antibacterial potency, including after drug-content normalization. Among the NPs, NP-1 showed the most favorable MIC profile, while MIC-normalized time-kill analysis revealed NP-dependent exposure differences without consistent bactericidal activity. At 500 µg/mL, all CA-loaded NPs reduced biofilm biomass by more than 95% against both bacterial species. NP-6 exhibited the highest numerical antibiofilm AUC values against S. aureus (133.37) and E. coli (128.85), although these differences were descriptive and did not establish statistical superiority. Conclusions: CA-loaded Eudragit® NPs demonstrated formulation-dependent antibacterial and antibiofilm responses, with NP-1 performing favorably in planktonic inhibition and NP-6 in integrated biofilm biomass reduction. These findings support further investigation of Eudragit®-based antibiotic delivery systems, although superiority over free CA and therapeutic advantages remain unverified.