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Background <p>Multidrug-resistant (MDR) <i>Acinetobacter baumannii</i> (<i>A. baumannii</i>) poses clinical challenges due to its antibiotic resistance and biofilm formation. Identifying compounds with antibacterial and antibiofilm effects in this species is essential. Various studies have shown that coumarin exhibits antimicrobial activity. In this study, we functionalized Fe₃O₄ nanoparticles with coumarin (Fe₃O₄@Coumarin NPs) to investigate their antibacterial and antibiofilm effects in MDR <i>A. baumannii</i>.</p> Methods <p>Four MDR clinical isolates of <i>A. baumannii</i> and the ATCC reference strain were tested. Fe₃O₄ nanoparticles were functionalized with coumarin using a glucose-mediated ligand-exchange method. Techniques such as FTIR, SEM, XRD, VSM, EDS, and zeta potential analysis were employed to characterize the synthesized nanoparticles. Antibacterial activity (MIC and MBC) was assessed via the broth microdilution method. Biofilm inhibition (MBIC) and eradication (MBEC) were evaluated using crystal violet staining. The expression levels of genes involved in biofilm formation, including <i>abaI</i>, <i>abaR</i>, and <i>bap</i>, were quantified using quantitative real-time PCR.</p> Results <p>FTIR and XRD confirmed the successful synthesis of Fe₃O₄@Coumarin NPs while preserving the crystalline structure and functional groups. SEM, EDS, and zeta potential measurements indicated a nanoscale size (~ 50–100&#xa0;nm), appropriate elemental composition, and colloidal stability. VSM indicated superparamagnetic behavior and high saturation magnetization, supporting their biomedical potential. Fe₃O₄@Coumarin NPs showed enhanced antibacterial and antibiofilm activity compared with free coumarin, with MIC and MBC values of 160 and 320&#xa0;µg/mL versus 640 and 1280&#xa0;µg/mL for coumarin, respectively, and MBIC/MBEC values of 160/320 µg/mL versus 1280/1280 µg/mL. Gene expression analysis showed that Fe₃O₄@Coumarin NPs reduced <i>abaI</i> and <i>abaR</i> expression to below 50% of control levels (whereas coumarin alone reduced their expression by approximately 30%) and decreased <i>bap</i> expression by more than 70%.</p> Conclusion <p>Our results showed that Fe₃O₄@Coumarin NPs could be more effective in combating MDR <i>A. baumannii</i> compared to coumarin alone.</p>

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Enhanced antibacterial and anti-quorum-sensing activity of coumarin via functionalization with Fe₃O₄ nanoparticles against multidrug-resistant Acinetobacter baumannii

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月27日

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  • Fateme Bazazzadeh,
  • Mohammad Hadi Masuomi,
  • Soroush Khazaie,
  • Atefeh Zamani,
  • Mohammad Mahdevar

摘要

Background

Multidrug-resistant (MDR) Acinetobacter baumannii (A. baumannii) poses clinical challenges due to its antibiotic resistance and biofilm formation. Identifying compounds with antibacterial and antibiofilm effects in this species is essential. Various studies have shown that coumarin exhibits antimicrobial activity. In this study, we functionalized Fe₃O₄ nanoparticles with coumarin (Fe₃O₄@Coumarin NPs) to investigate their antibacterial and antibiofilm effects in MDR A. baumannii.

Methods

Four MDR clinical isolates of A. baumannii and the ATCC reference strain were tested. Fe₃O₄ nanoparticles were functionalized with coumarin using a glucose-mediated ligand-exchange method. Techniques such as FTIR, SEM, XRD, VSM, EDS, and zeta potential analysis were employed to characterize the synthesized nanoparticles. Antibacterial activity (MIC and MBC) was assessed via the broth microdilution method. Biofilm inhibition (MBIC) and eradication (MBEC) were evaluated using crystal violet staining. The expression levels of genes involved in biofilm formation, including abaI, abaR, and bap, were quantified using quantitative real-time PCR.

Results

FTIR and XRD confirmed the successful synthesis of Fe₃O₄@Coumarin NPs while preserving the crystalline structure and functional groups. SEM, EDS, and zeta potential measurements indicated a nanoscale size (~ 50–100 nm), appropriate elemental composition, and colloidal stability. VSM indicated superparamagnetic behavior and high saturation magnetization, supporting their biomedical potential. Fe₃O₄@Coumarin NPs showed enhanced antibacterial and antibiofilm activity compared with free coumarin, with MIC and MBC values of 160 and 320 µg/mL versus 640 and 1280 µg/mL for coumarin, respectively, and MBIC/MBEC values of 160/320 µg/mL versus 1280/1280 µg/mL. Gene expression analysis showed that Fe₃O₄@Coumarin NPs reduced abaI and abaR expression to below 50% of control levels (whereas coumarin alone reduced their expression by approximately 30%) and decreased bap expression by more than 70%.

Conclusion

Our results showed that Fe₃O₄@Coumarin NPs could be more effective in combating MDR A. baumannii compared to coumarin alone.