The present invention concerns an in-vitro method for purification of blood samples, in particular blood donations and a purification system for blood samples. The method comprises the steps of: - coupling of an amphipathic ±-helical cathelicidin protein or a biologically active fragment thereof to a hydrophilic solid carrier - incubating the hydrophilic solid carrier coupled to the immobilized ±-helical cathelicidin protein or a biologically active fragment thereof with a blood sample - isolating the treated blood sample. Furthermore, the invention concerns a pharmaceutical composition, comprising an immobilized amphipathic ±-helical cathelicidin protein or a biologically active fragment thereof coupled to nanoparticles. The compositions of the invention are suitable for use in an antimicrobial treatment and/or prevention of a bacterial, fungal or viral infection or disease.
