Biomimetic Porphyrin Aggregation for Developing Novel Phase Change Photonic Materials

Porphyrins are aromatic, organic, light-absorbing molecules that occur abundantly in nature, especially in the form of molecular self-assemblies. Mimicking such highly efficient self-assembled systems has a vast potential in a variety of applications, from sensing, photomedicine to nanomedicine. Our recent discovery of porphysome provides a glimpse of this potential as the self-assembly of porphyrin-lipid building blocks enables intrinsic multimodal properties including photothermal/photoacoustic (intact state), photodynamic/fluorescent (disrupted state), and PET and MRI (metal chelating of porphyrin building blocks). To broaden its utility, we are looking for ways to create phase change porphysomes that could be developed into photonic molecular sensors that are capable of detecting environmental stimuli through alterations of optical absorption. Photosynthetic organisms have evolved ingenious strategies to optimize light absorption through nanoscale ordered dye aggregation. Learning from these nature’s self-assembly principles, we have recently succeeded in making the first phase change porphyrin nanoparticle, a tuneable, reversible and stimuli-responsive photoacoustic nanoswitch based on the change in aggregation-induced large absorption shift. Using this new photonic material, we non-invasively determined a localized temperature change in vivo, relevant for monitoring thermal therapies of solid tumors. Similar strategies may be applied alongside photoacoustic imaging, to detect other stimuli such as pH and enzymatic activity.