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Controlled Release of Cinnamon Leaf Oil from Chitosan Microcapsules Embedded within a Sodium Alginate/Gelatin Hydrogel-Like Film for Pseudomonas aeruginosa Elimination
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1  Centre for Textile Science and Technology (2C2T), University of Minho


The multidrug-resistant Pseudomonas aeruginosa is considered a public threat. With antibiotics increasing bacteria resistance, alternative natural origin biomolecules are being examined for their potential against this bacterium. Essential oils (EOs) have demonstrated significant effects against several microorganisms, revealing as well strong anti-inflammatory, antiseptic, analgesic and antioxidative properties. However, due to their volatile nature they cannot be delivered to the infected site in their free-state. As such, biodegradable polymeric delivery platforms are being engineered. Chitosan has been commonly used as a protective barrier for many biomolecules, preserving their activity until reaching their destination. It is also highly effective against Gram-negative bacteria. Here, hydrogel-like films were produced from an optimized combination of sodium alginate (SA) and gelatin (GN) to serve as delivery platforms for the controlled release of cinnamon leaf oil (CLO) entrapped within chitosan microcapsules. The minimum inhibitory concentration (MIC) of CLO was established at 39.3 mg/mL against P. aeruginosa. Chitosan microcapsules were prepared via ionotropic gelation with tripolyphosphate, containing at the core the CLO at MIC. Successful production was confirmed by fluorescent microscopy using Nile red as detection agent. The encapsulation efficiency and controlled release of the oil were monitored in basic (infected wounds) and physiological pH for a period of 24 h. Microcapsules were then embedded within a biodegradable SA/GN polymeric matrix processed via a solvent casting/phase inversion methodology with SA/GN at 70/30 polymer ratio and 2 wt% SA concentration in distilled water. The coagulation bath was composed of a 2 wt% CaCl2 aqueous solution. The CLO-containing chitosan microcapsules homogeneous distribution was guaranteed by successive vortex and blending processes applied prior to casting. Flexible, highly hydrated films were obtained, with the presence of loaded chitosan capsules being confirmed by FTIR. Qualitative and quantitative antimicrobial examinations validated the modified film potential to fight infections caused by P. aeruginosa bacteria.

Keywords: Bio-based polymers; drug delivery platform; natural extracts; trigger-based release; bactericidal effects