New Fe3O4-Based Coatings with Enhanced Anti-Biofilm Activity for Medical Devices

Abstract

With the increasing use of invasive, interventional, indwelling, and implanted medical devices, healthcare-associated infections caused by pathogenic biofilms have become a major cause of morbidity and mortality. Herein, we present the fabrication, characterization, and in vitro evaluation of biocompatibility and anti-biofilm properties of new coatings based on Fe₃O₄ nanoparticles (NPs) loaded with usnic acid (UA) and ceftriaxone (CEF). Sodium lauryl sulfate (SLS) was employed as a stabilizer and modulator of the polarity, dispersibility, shape, and anti-biofilm properties of the magnetite nanoparticles. The resulting Fe₃O₄ functionalized NPs, namely Fe₃O₄@SLS, Fe₃O₄@SLS/UA, and Fe₃O₄@SLS/CEF, respectively, were prepared by co-precipitation method and fully characterized by XRD, TEM, SAED, SEM, FTIR, and TGA. They were further used to produce nanostructured coatings by matrix-assisted pulsed laser evaporation (MAPLE) technique. The biocompatibility of the coatings was assessed by measuring the cell viability, lactate dehydrogenase release, and nitric oxide level in the culture medium and by evaluating the actin cytoskeleton morphology of murine pre-osteoblasts. All prepared nanostructured coatings exhibited good biocompatibility. Biofilm growth inhibition ability was tested at 24 h and 48 h against Staphylococcus aureus and Pseudomonas aeruginosa as representative models for Gram-positive and Gram-negative bacteria. The coatings demonstrated good biocompatibility, promoting osteoblast adhesion, migration, and growth without significant impact on cell viability or morphology, highlighting their potential for developing safe and effective antibacterial surfaces.

Keywords: biofilm inhibition; ceftriaxone; coatings; hydrophobic nanoparticles; nosocomial infections; sodium lauryl sulfate; usnic acid.

Figure 1

Chemical structures of the antimicrobial agents.

Figure 2

XRD diffractogram of Fe₃O₄@SLS.

Figure 3

TEM (a,b) micrographs, SAED pattern (c), and size distribution (d) of Fe₃O₄@SLS NPs.

Figure 4

Combined TGA-DSC thermogram of pristine Fe₃O₄ NPs.

Figure 5

Combined TGA-DSC thermogram of core/shell Fe₃O₄@SLS NPs.

Figure 6

FT-IR spectra of (a₁–a₄) Fe₃O₄@SLS, (b₁–b₄) Fe₃O₄@SLS/UA, and (c₁–c₄) Fe₃O₄@SLS/CEF at (a₂,b₂,c₂) F = 200 mJ/cm², (a₃,b₃,c₃) F = 300 mJ/cm², and (a₄,b₄,c₄) F = 400 mJ/cm² laser fluences and (a₁,b₁,c₁) dropcast.

Figure 7

IR maps of Fe₃O₄@SLS created based on –CH₂– and S–O groups at surface intensity distributions of (a₁–a₄) 2916 cm⁻¹ and (b₁–b₄) 1107 cm⁻¹ for (a₁,b₁) dropcast and coatings deposited at (a₂,b₂) 200 mJ/cm², (a₃,b₃) 300 mJ/cm², and (a₄,b₄) 400 mJ/cm² laser fluences.

Figure 8

IR maps of Fe₃O₄@SLS/UA created based on C=O and S–O groups at surface intensity distributions of (a₁–a₄) 1697 cm⁻¹ and (b₁–b₄) is 1107 cm⁻¹ for (a₁,b₁) dropcast and coatings deposited at (a₂,b₂) 200 mJ/cm², (a₃,b₃) 300 mJ/cm², and (a₄,b₄) 400 mJ/cm² laser fluences.

Figure 9

IR maps of Fe₃O₄@SLS/CEF created based on C=O and S–O groups at surface intensity distributions of (a₁–a₄) 1658 cm⁻¹ and (b₁–b₄) 1107 cm⁻¹ for (a₁,b₁) dropcast and coatings deposited at (a₂,b₂) 200 mJ/cm², (a₃,b₃) 300 mJ/cm², and (a₄,b₄) 400 mJ/cm² laser fluences.

Figure 10

SEM micrographs of Fe₃O₄@SLS (a1,b1,c1,d1), Fe₃O₄@SLS/UA (a2,b2,c2,d2), and Fe₃O₄@SLS/CEF (a3,b3,c3,d3) plan-view (a1–a3,b1–b3,c1–c3) and cross-sections (d1–d3) recorded at various magnifications.

Figure 11

Biocompatibility of Fe₃O₄@SLS, Fe₃O₄@SLS/CEF, and Fe₃O₄@SLS/UA coatings, as shown by cell viability (MTT assay), NO level, and LDH release after 24 h of exposure on MC3T3-E1 murine cells. All results were calculated as mean ± standard deviations of three different replicates and expressed relative to control.

Figure 12

Biocompatibility of Fe₃O₄@SLS, Fe₃O₄@SLS/CEF, and Fe₃O₄@SLS/UA coatings, as shown by cell viability (MTT assay), NO level, and LDH release after 72 h of exposure on MC3T3-E1 murine cells. All results were calculated as mean ± standard deviations of three different replicates and expressed relative to control.

Figure 13

Actin cytoskeleton organization of MC3T3-E1 murine cells after 24 and 72 h of incubation with Fe₃O₄@SLS, Fe₃O₄@SLS/CEF, and Fe₃O₄@SLS/UA coatings. F-actin (green) was labeled with phalloidin-fluorescein isothiocyanate (FITC), and nuclei (blue) were counterstained with 4′,6-diamidino-2-phenylindole dihydrochloride (DAPI). Magnification (20× objective).

Figure 14

Evaluation of S. aureus biofilm growth after 24/48 h of incubation with Fe₃O₄@SLS, Fe₃O₄@SLS/CEF, and Fe₃O₄@SLS/UA coatings vs. control (one-way ANOVA, when comparing samples vs. control * p < 0.05; ** p < 0.001).

Figure 15

Evaluation of P. aeruginosa biofilm growth after 24/48 h of incubation with Fe₃O₄@SLS, Fe₃O₄@SLS/CEF, and Fe₃O₄@SLS/UA coatings vs. control (one-way ANOVA, when comparing samples vs. control * p < 0.05; ** p < 0.001).