Free to go: A pH-labile immobilization of the melittin peptide with acetal linkers in the pore system of a SBA-15 host allows release of the peptide upon decrease of the pH value from 7.4 to 5.5. Such a release is shown by melittin-induced lysis of mouse erythrocytes. The method could be used to prepare new silica-based peptide delivery systems for targeted cancer therapy.