Self-assembled, covalently linked, hollow phthalocyanine nanospheres

A rational design and synthesis of covalently linked Pc nanospheres with a very thin shell and hollow interior, composed of approximately 12 000 Pc units on average, was demonstrated through thiol-ene click chemistry without using any templates or emulsifiers. The ZnPc nanospheres allow post-synthetic modification to improve their dispersibility in aqueous solution without altering the morphology of the nanospheres or the properties of ZnPc cores. More importantly, the ZnPc nanospheres showed higher singlet oxygen generation efficiency and in vitro phototoxicity than monomeric Pc molecules, suggesting that ZnPc nanospheres are potentially useful as a PS for PDT. We anticipate that the ZnPc nanospheres would allow other post-synthetic modifications such as the introduction of targeting ligands to deliver the nanospheres to specific target sites and perform a dual chemo-and photodynamic therapy by the encapsulation of therapeutic agents. The easy synthesis of a hollow spherical framework with a high Pc content, coupled with facile post-synthetic modification may allow Pc nanospheres to be a versatile platform for a diverse range of medical and non-medical applications.