Synergistic performance of cyclodextrin–agar hydrogels for ciprofloxacin delivery and antimicrobial effect

Combination of cyclodextrins (CDs) and agar may render hydrogels that interact with drugs by forming inclusion complexes and/or ionic bonds. Hydroxypropyl-β-cyclodextrin and methyl-β-cyclodextrin (20%) in alkaline solutions containing or not agar (up to 1.5%) were cross-linked with ethyleneglycol diglycidylether at 50 °C. Agar increases hardness, compressibility and modulus of deformability, but does not interfere in the loading and release of a probe (3-methyl benzoic acid) with high affinity for CD. Agar notably promoted the loading of the zwitterion ciprofloxacin and endowed the hydrogels with ability to retain the drug in water medium. The release can be triggered by ions or changes in pH, leading to a 12-h sustained delivery. Loading and release profiles were compared to those of maltodextrin-based hydrogels, and the contribution of CDs and agar elucidated. Microbiological tests with Gram-negative and Gram-positive bacteria confirmed the suitability of the “green” CD–agar hydrogels for the development of drug delivery systems with tunable physical and drug loading/release properties.