The molecular mechanism of photochemical internalization of cell penetrating peptide-cargo-photosensitizer conjugates

Abstract

In many drug delivery strategies, an inefficient transfer of macromolecules such as proteins and nucleic acids to the cytosol often occurs because of their endosomal entrapment. One of the methods to overcome this problem is photochemical internalization, which is achieved using a photosensitizer and light to facilitate the endosomal escape of the macromolecule. In this study, we examined the molecular mechanism of photochemical internalization of cell penetrating peptide-cargo (macromolecule)-photosensitizer conjugates. We measured the photophysical properties of eight dyes (photosensitizer candidates) and determined the respective endosomal escape efficiencies using these dyes. Correlation plots between these factors indicated that the photogenerated 1O2 molecules from photosensitizers were highly related to the endosomal escape efficiencies. The contribution of 1O2 was confirmed using 1O2 quenchers. In addition, time-lapse fluorescence imaging showed that the photoinduced endosomal escape occurred at a few seconds to a few minutes after irradiation (much longer than 1O2 lifetime), and that the pH increased in the endosome prior to the endosomal escape of the macromolecule.

Flexible synthesis of cationic peptide–porphyrin derivatives for light-triggered drug delivery and photodynamic therapy

“…25 The aim of this study was to investigate the potential of a number of bioconjugation reactions for the efficient modular preparation of CPP–porphyrin conjugates, as a general strategy to convert classical PDT agents into amphiphilic conjugates suitable for targeted PDT and PCI.…”

Relation of Photochemical Internalization to Heat, pH and Ca2+ Ions

“…We indicated that endosomal escape efficiencies are mainly related to photogenerated 1 O 2 , not heat, from photosensitizers. In addition, we discovered an endosomal pH increase before the photoinduced endosomal escape . However, our previous report lacks detailed explanations of how these factors are directly related to endosomal escape.…”

“…In our previous study, endosomal pH increase was observed after light irradiation and 60–80 s before the endosomal escape of the TatU1A‐photosensitizer/RNA complex . The photoinduced pH increase may be due to (1) 1 O 2 ‐induced inactivation of the endosomal V‐ATPase proton pump responsible for the pH decrease, or (2) leakage of endosomal protons into the cytoplasm caused by 1 O 2 ‐induced destabilization of the endosomal membrane.…”

“…In this study, we fill in gaps in our previous understanding of endosomal escape of the CPP‐cargo‐photosensitizer conjugate (TatU1A‐PS/shRNA) by focusing on the roles of heat, pH and Ca 2+ . A study recently concluded that photogenerated heat from photosensitizers is not significantly correlated with endosomal escape by focusing on photophysical parameters of photosensitizers . In this study, we investigated the involvement of heat in endosomal escape of TatU1A‐PS/shRNA by changing the temperature of the cell just before photoirradiation.…”

Photo-Enhanced Delivery of Genetic Material Using Curcumin Loaded Composite Nanocarriers

“…The known mechanism of action of photochemical internalisation is the energy level transition during which generation of singlet oxygen occurs. This singlet oxygen is responsible for the oxidising different cellular organelles [30]. Due to its short lifetime and short range of action, only cellular targets close to the photosensitiser are oxidised by the generation of singlet oxygen [31].…”