Spray-by-spray in situ cross-linking alginate hydrogels delivering a tea tree oil microemulsion

In this paper we propose an in situ forming ionically cross-linked alginate (Alg) hydrogel delivering a Tea Tree Oil microemulsion (Me-TTO) and potentially useful as an advanced dressing for infected wounds. Alg hydrogels were prepared by a spray-by-spray deposition method with the aim to minimize the discomforts during application. From pseudoternary phase diagrams, it was found that proper combination of TTO, water, polysorbate 80 and ethanol gave stable spherical Me-TTO with good antimicrobial activity. On this basis, Me-TTO at 20% TTO was selected for further inclusion in an Alg hydrogel prepared by alternating sprays of Alg/Me-TTO and calcium chloride solutions. Homogeneous dispersion of Me-TTO inside cross-linked Alg was assessed by different macroscopic and microscopic methods demonstrating the superior propensity of Me-TTO to be integrated in the water-based hydrogel as compared to TTO. Antimicrobial effect of Alg/Me-TTO hydrogels on Escherichia Coli strains was remarkable, highlighting the potential of the system as bioactive wound dressing. (C) 2014 Elsevier B.V. All rights reserved.