different contents of chitosan and bioactive glass may explainthis phenomenon. The scaffolds doped with 1% gentamicin sul-fate have a stable release from 1 h of immersion while for scaffoldsdoped with 3% gentamicin sulfate; stabilization is observed from 2 hof immersion in PBS. Moreover, the introduction of a high concen-tration of drug causes a later stabilization and also more importantrelease of drug. The hydrophilic character of chitosan and genta-micin sulfate may explain the high release of gentamicin sulfateduring the first minutes. The rapid release of gentamicin sulfatefor both concentrations can be explained by the chemical bondscreated between chitosan and gentamicin sulfate. The literaturedoes not mention the possible connections but we can formulate ahypothesis. The most plausible hypothesis is that hydrogen bondsare formed between the OH groups of chitosan (Fig. 1) and genta-micin sulfate (Fig. 2) creating a “zipper effect”. Indeed, hydrogenbonds involve a hydrogen atom and an electronegative atom (suchas oxygen). Hydrogen bonds have a low intensity (20 times weakerthan the covalent bonds). This hypothesis could therefore justifyand explain the rapid release of gentamicin sulfate from the firstminutes of immersion of the scaffolds in PBS.