Inclusion of these peptides leads to superior intracellular drug accumulation and resulting in higher cytotoxicity than liposomes devoid of endosomolysis properties. As a new approach, Kullberg et al. attached the pore-forming protein listeriolysin O to HER2-targeted bleomycin-loaded liposomes, resulting in a higher toxicity in vitro over targeted bleomycin-loaded liposomes without listeriolysin O [342]. 6.4. Mitochondrial Targeting Effective treatment of cancer faces problems due to limited drug penetration and drug resistance [343–345]. Since resistance to antineoplastic agents induced

cell death is frequently associated with altered mitochondrial function and/or altered expression of Inhibitors,research,lifescience,medical mitochondrial regulators of apoptosis [300, 343], subcellular accumulation of anticancer drugs in mitochondria can give a therapeutic advantage and has been exploited [300, 346] (Figure 4). Mitochondria targeting of epirubicin-loaded liposomes by inclusion of the positively SCR7 solubility dmso charged electrolyte dequalinium increased their Inhibitors,research,lifescience,medical cytotoxicity in vitro and antitumor activity in vivo over untargeted liposomes [347]. Hatakeyama and coworkers developed a Mito-Porter multifunctional Inhibitors,research,lifescience,medical envelope-type nanodevice (MEND) nanocarrier with sequential activation of essential functions necessary for mitochondria delivery [292, 346, 348].

These formulations have a “programmed packaging”; their surface is functionalized with a targeting moiety (transferrin or antibody), a PEG-lipid conjugate for long blood circulation; and a PEG-lipid bond that is cleaved in the tumor environment by matrix metalloproteinases leading to exposure Inhibitors,research,lifescience,medical of a CPP (octaarginine, tetraarginine) for tumor-selective endocytosis. Once inside the cell, a fusogenic peptide (KALA or GALA) allows endosomal escape of positively charged liposomes by membrane fusion, the positive charge favoring their interaction with the largely negative outer mitochondrial membrane, and finally the fusogenic lipid DOPE allows internalization of

the cargo by the mitochondria [346]. Although Inhibitors,research,lifescience,medical complex, such nanocarriers are produced in GMP conditions warranting their clinical evaluation [348]. Instead of using one moiety for each step of intracellular targeting, Zhang and coworkers designed a smart, pH-responsive lipid (1,5-dioctadecyl-L-glutamyl-2-histidyl-hexahydroxybenzoic acid, HHG2C18) [349]. The liposomes generated are negatively charged at physiological pH and have a sharp charge inversion at acidic pH (from −22.9mV at pH 7.4 to +6.3mV at pH 6.5) Rolziracetam for tumor-selective uptake. After uptake, hexahydrobenzoic acid is released by cleavage of the β-carboxylic acid linker in the endosomes leading to exposure of histidine and the endosomal escape of positively charged liposomes electrostatically targeted to the outer mitochondrial membrane. Liposomes containing the HHG2C18 lipid and encapsulating the anticancer drug Temsirorimus showed higher renal cancer tumor growth inhibition than free drug or nonresponsive liposomes.