Light-Triggered Polymeric Nanobombs for Targeted Cell Death

A recent approach in the treatment of diseased cells/tissues is the use of smart, stimuli-responsive nanomaterials. Well-known examples include photosensitizer agents that after light irradiation at a specific wavelength generate singlet oxygen species (strongly cytotoxic) or self-assembled supramolecular structures, which blow up cancer cells by releasing their payload upon an external stimulus, thus making cancer cells swell and burst (so-called "nanobombs"). In this work we synthesized and characterized a polymeric star-like pentaporphyrin system (5P) that, depending on the photoexcitation wavelength selected, can act either as a photosensitizer or as a nanobomb. The 5P compound was characterized by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, nuclear magnetic resonance, UV-vis, and fluorescence spectroscopy techniques. The hydrodynamic size of the 5P compound in physiological buffer solution, as determined by dynamic light spectroscopy, pointed to the formation of aggregates. The toxicity and the blow-up capability of 5P were tested on human neuroblastoma (SH-SY5Y cell line). Results demonstrated that the 5P system can work as a light-triggered nanobomb for targeted cell death. In fact, while the cell's treatment with the compound in the darkness did not induce cell toxicity, the 5P irradiation with laser light at wavelengths of 458 or 405 nm resulted in the generation of singlet oxygen species or a true explosion in a cellular environment, respectively.