Photochemical internalization (PCI) is a drug and gene therapy delivery method that is designed to improve the release of macromolecules and hydrophilic chemotherapeutic agents from endosomes and lysosomes to the cytosol of targeted cancer cells . PCI is based on the use of endosomal and lysosomal Localizing amphiphilic photosensitizers qui, after-activation by light , Induce photochemical reactions resulting and in destruction of endocytic membrane mediated by reactive oxygen species (ROS). Teaphotochemical destabilization of the membrane of the endocytic vesicle result in an endosomal escape of the entrapped drugs.  The technology was invented by Professor Kristian Berg at the Norwegian Radium Hospital.
- Jump up^ Selbo PK, Weyergang A, Høgset A, Norum OJ, Berstad MB, Vikdal M, Berg K (2010) Photochemical internalization provides time- and space-controlled endolysosomal escape of therapeutic molecules. J Control Release,148(1): 2-12. doi: 10.1016 / j.jconrel.2010.06.008