Studies of photochemical internalisation : mechanisms and strategies in cancer therapeutics

• Main Author: Wang, T.-W.
• Published: University College London (University of London) 2010
• Subjects: 610
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.564885

Photochemical internalisation (PCI) is a technique which enhances targeted drug delivery using light in combination with a photosensitiser. It is a modification of photodynamic therapy (PDT) which involves sub-lethal photodynamic treatment to modify the intracellular distribution of co-administered drugs and other agents which are sequestered in lyso/endosomes. In this study, PDT and PCI using a sulfonated chlorin, AmphinexTM (TPCS2a), in combination with two anti-cancer drugs, saporin or bleomycin, have been investigated both in vitro and in vivo. In vitro experiments initially examined the cell uptake, photostability and cellular localisation of Amphinex using A431 human epidermoid carcinoma cells and HN5 human head and neck squamous cells. The cell killing effect after PDT and PCI in the presence of saporin and bleomycin were assessed. The bioavailability and therapeutic efficacy were also compared with another two PCI photosensitisers, TPPS2a and AlPcS2a. The results indicate that PCI is able to induce the relocalisation of bleomycin and saporin inside cells and thereby enhance cell death. A new porphyrin-peptide bioconjugate of a cell penetrating peptide (CPP) and tetraphenylporphine was investigated for PDT and PCI. It was found that CPP peptide conjugation renders efficient cellular delivery of the tetraphenylporphine for use as a PDT and PCI sensitiser. The pharmacokinetics of Amphinex in normal and tumour-bearing rats was studied using quantitative fluorescence microscopy and chemical extraction. In vivo Amphinex PCI effects and the comparison with PDT were investigated in normal rat liver, colon and a syngeneic rat fibrosarcoma tumour models. Amphinex PCI showed a significant enhancement in inducing damage to normal tissues and tumour. The involvement of apoptosis was also established using the TUNEL assay. This thesis has demonstrated that Amphinex has favourable properties for PDT and PCI. The consistent results from both in vitro and in vivo experiments indicate that Amphinex has the potential for further clinical utilization.