Stimuli-responsive
liposomes are promising
drug carriers for
cancer treatment because they enable controlled drug release and the maintenance of desired
drug concentrations in
tumor tissue. In particular, near-IR (NIR) light is a useful stimulus for triggering drug release from
liposomes based on its advantages such as deep tissue penetration and safety. Previously, we found that a
silicon phthalocyanine derivative, IR700, conjugated to
antibodies, can induce the
rupture of the cell membrane following irradiation by NIR light. Based on this finding, we constructed IR700-modified
liposomes (IR700
liposomes) and evaluated their drug release properties triggered by NIR light. IR700
liposomes released substantial amounts of encapsulated
calcein following irradiation by NIR light. Drug release was substantially suppressed by the addition of
sodium azide, suggesting that liposomal membrane permeabilization was mediated by
singlet oxygen generated from IR700. Moreover,
calcein release from IR700
liposomes triggered by NIR light was promoted under conditions of deoxygenation and the presence of electron donors. Thus, membrane disruption should be induced by the physical change of IR700 from highly hydrophilic to hydrophobic as we previously described, although
singlet oxygen can cause a certain level of membrane disruption under normoxia. We also observed that
doxorubicin-encapsulated IR700
liposomes exhibited significant cytotoxic effects against CT-26 murine colon
carcinoma cells following NIR light exposure. These results indicate that IR700
liposomes can efficiently release anti-
cancer drugs following NIR light irradiation even under hypoxic conditions and, therefore, they would be useful for
cancer treatment.