Facile preparation of organic-inorganic hydrogels containing silver or essential oil with antimicrobial effects

Hydrogels (HGs) based on Poly-(vinyl)alcohol (PVA), sodium alginate (SA) and borax were appropriately modified with both poly(ethylene)oxide (PEO) and ZnAl layered double hydroxide (LDH) to create a network in which active molecules can be loaded and confined. PEO acts as a porogen agent in the PVA matrix, reducing the crosslinking degree of the polymer and favouring the retention of organic apolar species. LDH, in nitrate or chloride form, organically modified with SA (LDH/N@SA and LDH/C@SA), reinforces the polymeric network, improving its mechanical properties. Moreover, LDH/N@SA and LDH/C@SA were used to grow and anchor nanoparticles of Ag and Ag/AgCl, becoming fillers of HGs containing active species. An additional sample was prepared by incorporating thyme essential oil (EO) in a HG prepared with LDH/C@SA. These systems provided a sustained release of silver ions and EO and a very efficient swelling in water. The HGs subjected to antimicrobial tests, exhibited good antimicrobial activity against both Gram-positive (Staphylococcus epidermidis and S. aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria and yeast (Candida albicans). These characteristics make the HGs suitable to be proposed as patches for wound healing.