Host–guest interaction based supramolecular photodynamic therapy systems: a promising candidate in the battle against cancer

Owing to its spatiotemporal selectivity and noninvasive nature, photodynamic therapy (PDT) has become a promising approach for the treatment of cancer. However, the non-targeting capability and the accompanying side effects of PDT as well as the low solubility/stability of photosensitizers (PSs) seriously limit its further development. In recent years, host-guest interaction based supramolecular chemistry has attracted more and more attention benefiting from its distinctive properties to introduce macrocyclic hosts including cyclodextrins (CDs), calix[n]arenes (CAs), cucurbit[n]urils (CBs), pillar[n]arenes (PAs), crown ethers, etc. into supramolecular systems, without multiple synthesis steps and complicated purification processes. In particular, supramolecular PDT systems constructed based on macrocylic hosts and PSs through host-guest interactions provide ideal platforms to overcome the limitations of PDT effectively. In this review, recent achievements made in supramolecular PDT systems based on host-guest interactions are comprehensively overviewed, which are categorized into four sections according to the types of macrocyclic hosts. Furthermore, supramolecular PDT combined with other treatments for synergistic therapy is well elucidated. In addition, challenges and perspectives of new supramolecular PDT systems and their potential clinical application are also discussed at the end of the review.