Gadolinium-Doped Cerium Oxide Nanoparticles Embedded in a 3D-Printed System for Antimicrobial Applications

Gadolinium-doped cerium oxide (GDC) nanoparticles were synthesized, citrate-functionalized, and incorporated into 3D-printed poly-(vinyl alcohol) (PVA) systems for antimicrobial applications. Citrate functionalization reduced the hydrodynamic diameter from ∼600 nm to ∼250 nm and increased the zeta potential magnitude from -15 mV to -35 mV, indicating significantly improved colloidal stability over 30 days. Antimicrobial assays against Escherichia coli, Staphylococcus aureus, and Candida albicans revealed that citrate-coated nanoparticles in suspension achieved comparable inhibition at concentrations up to 2-fold lower than uncoated counterparts. Importantly, after incorporation into 3D-printed PVA matrices, the systems retained ≥80% of the antimicrobial efficacy observed in suspension, with maximum log reductions of 5.3 (≈99.9995% killing) against S. aureus at low nanoparticle loadings (0.83 mg/mL). Cytotoxicity assays on HaCaT keratinocytes demonstrated a clear dose-dependent response for citrate-coated nanoparticles (IC₅₀ = 3.5 mg/mL, R² = 0.986), whereas uncoated nanoparticles showed irregular behavior. Furthermore, zebrafish embryo toxicity tests further confirmed that citrate coating significantly reduced acute toxicity, with 0% mortality at 100 mg/L for GDC-cit versus 80% for uncoated GDC. These results demonstrate that 3D-printed PVA systems incorporating citrate-functionalized GDC nanoparticles constitute a promising, scalable, and safer-by-design antimicrobial platform. The preservation of antimicrobial activity across distinct physicochemical environments highlights the potential of these systems to bridge the gap between nanomaterial development and practical biomedical applications.