An antioxidative liposome catalysis that mimics both superoxide dismutase (SOD) and peroxidase (POD) activities has been developed by using the liposomes modified with lipophilic Mn-(5,10,15,20-tetrakis[1-hexadecylpyridium-4-yl]-21H,23H-porphyrin) (Mn-HPyP). The SOD- and POD-like activities of the Mn-HPyP-modified liposome were first investigated by varying the type of phospholipid, such as 1,2-distearyl-sn-glycero-3-phosphocholine (DSPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC). Higher SOD-like activity was obtained in the case of DLPC and DMPC liposomes, in which the ligands were well-dispersed on the membrane in the liquid crystalline phase. The POD-like activity was maximal in the case of DMPC liposome, in which the Mn-HPyP complex was appropriately clustered on the membrane in the gel phase. On the basis of the above results, the co-induction of the SOD and POD activities to eliminate the superoxide and also hydrogen peroxide as a one-pot reaction was finally performed by using the Mn-HPyP-modified DMPC liposome, resulting in an increase in the efficiency of the elimination of both superoxide and hydrogen peroxide.

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The liposome modified with simple ligand and metal ions shows the superoxide dismutase-like activity. The membrane fluidity of various liposomes modified with the functional ligand (Dodecanoyl-His; Dodec-His) and the clustering of the ligand on the liposome surface were first characterized, showing that the clustering of Dodec-His could be induced on the liposome surface at gel-phase. The capacity of adsorption of Cu and Zn was found to be increased dependently on the type of liposome, resulting in the maximal adsorption in liposome prepared by 1,2-dipalmitoyl-snglycero-3-phosphocholine (DPPC) at gel state and with higher ligand clustering state. As a result on the SOD-like activity of the metal/ligand-modified liposome, the SOD-like activity was found to be induced by using the above liposomes although its activity level is not so high.

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