B197
Novel quantum dot-photosensitizer nanocomposites and their potential in photodynamic therapy of cancer
Elnaz Yaghini1, Martin Austwick1, Alexander M Seifalian2, Alexander J MacRobert1
1National Medical Laser Centre (NMLC) Devision of Surgery, University College London, London, UK, 2Biomaterial and Tissue Engineering Centre, Devision of Surgical and Interventional Science, University College London, London, UK
Background
Applicability of quantum dot nanoparticles (QDs) in photodynamic therapy (PDT) was evaluated by studying interaction between CdSe/ZnS QDs with water soluble phthalocyanine photosensitizer (PS). We assessed ability of QDs to function as energy donors in fluorescence resonance energy transfer (FRET), in conjunction with photosensitizer acting as an energy acceptor, to develop QD-PS nanocomposites for cancer therapy.
Method
QDs were bound to phthalocyanine via electrostatic interactions, forming QD-PS conjugates. QD-PSs nanocomposites excited at 488 nm where only weak PS absorption occurs. Fluorescence lifetime measurements performed to confirm FRET occurrence. Efficiency of these complexes to generate cytotoxic Singlet Oxygen (1O2) was investigated, using anthracene dipropionic acid as 1O2 scavenger.
Conclusion
Following excitation at 488 nm substantial reduction in QD fluorescence was observed with concomitant enhancement in PS fluorescence, indicating FRET occurrence between them. Our data further was confirmed with detecting shortening of QD donor lifetime in presence of PS. We found FRET efficiency was dependent on QD/PS ratio, where increasing PSs concentration resulted in progressive quenching of QD fluorescence. Furthermore, we showed these nanocomposites photoproduce 1O2 via FRET with a quantum yield (QY) of approximately 10%. This study revealed QDs can be used to sensitize PDT agents through FRET resulting in generation of cytotoxic 1O2. Advantages of this approach are that firstly it harnesses intense, broad absorption properties of quantum dots from UV to IR, and secondly possibility of cellular targeting of QD-photosensitiser composites. Fluorescence microscopy has confirmed uptake of these nanoparticles and further studies of light-induced cytotoxicity are in progress.
