Abstract
New approaches to deal with the growing concern associated with antibiotic-resistant bacteria are emerging daily. Essential oils (EOs) are natural antimicrobial substances with great potential to mitigate this situation. However, their volatile nature, in their liquid-free form, has restricted their generalized application in biomedicine. Here, we propose the use of cellulose acetate (CA)/polycaprolactone (PCL) wet-spun fibers as potential delivery platforms of selected EOs to fight infections caused by Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Twenty EOs were selected and screened for their minimal inhibitory concentration (MIC), using the antibiotic ampicillin as positive control. The cinnamon leaf oil (CLO), cajeput oil (CJO), and the clove oil (CO) were the most effective EOs, against the Gram-positive (MIC < 22.38 mg/mL) and the Gram-negative (MIC < 11.19 mg/mL) bacteria. Uniform microfibers were successfully wet-spun from CA/PCL with an averaged diameter of 53.9 ± 4.5 µm, and then modified by immersion with CLO, CJO and CO at 2 × MIC value. EOs incorporation was confirmed by UV-visible spectroscopy, Fourier-transformed infrared spectroscopy, and thermal gravimetric analysis. However, while microfibers contained ampicillin at MIC (control) after the 72 h modification, the CLO, CO and CJO-loaded fibers registered ≈ 14%, 66%, and 76% of their MIC value, respectively. Data showed that even at small amounts the EO-modified microfibers were effective against the tested bacteria, both by killing bacteria more quickly or by disrupting more easily their cytoplasmic membrane than ampicillin. Considering the amount immobilized, CLO-modified fibers were deemed the most effective from the EOs group. These results indicate that CA/PCL microfibers loaded with EOs can be easily produced with increased antibacterial action, envisioning their use as scaffolding materials for the treatment of infections.
Highlights
For many years, biomolecules have been used in biomedical applications to fight infections and/or instigate specific cell/tissue responses
Essential oils (EOs) were initially screened for their antibacterial activity against the Gram-positive bacteria S. aureus and the Gram-negative bacteria E. coli via the agar-well diffusion test
Still, when looking at both the S. aureus and E. coli data, it is possible to highlight the cajeput oil (CJO), TTO, SO, cinnamon leaf oil (CLO), NO, and clove oil (CO) as the most probable to present a superior antimicrobial action as their Zones of inhibition (ZoI) falls within the moderate activity range for both cases
Summary
Biomolecules have been used in biomedical applications to fight infections and/or instigate specific cell/tissue responses. Natural products derived from plants with antimicrobial, anti-inflammatory, antioxidant, and chemo-preventive properties have been used for many generations in traditional medicine [4] Nowadays, they are gaining new status as an alternative to antibiotics, by preventing and treating infectious diseases with little impact in the environment [5]. Essential oils (EOs) are mixtures of aromatic, volatile, lipophilic biomolecules, extracted from regions of plants (e.g., flowers, leaves, twigs, bark, wood, fruits, etc.) in which they work as secondary metabolites, defending the host from microbial invasion [1,5] They are formed of complex mixtures of hydrophobic molecules, including thymol, carvacrol, and eugenol (among others), which exhibit a broad spectrum of antimicrobial activity against bacteria, fungi, and viruses. Fibers and fibrous constructs have emerged as optional platforms for their targeted and therapeutic delivery, this way promoting their application in the combat against drug-resistant bacteria [7,8]
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