Tumor‐pH‐Responsive Dissociable Albumin–Tamoxifen Nanocomplexes Enabling Efficient Tumor Penetration and Hypoxia Relief for Enhanced Cancer Photodynamic Therapy

Abstract Despite the promises of applying nano‐photosensitizers (nano‐PSs) for photodynamic therapy (PDT) against cancer, severe tumor hypoxia and limited tumor penetration of nano‐PSs would lead to nonoptimized therapeutic outcomes of PDT. Therefore, herein a biocompatible nano‐PS is prepared by using tamoxifen (TAM), an anti‐estrogen compound, to induce self‐assembly of chlorin e6 (Ce6) modified human serum albumin (HSA). The formed HSA–Ce6/TAM nanocomplexes, which are stable under neutral pH with a diameter of ≈130 nm, would be dissociated into individual HSA–Ce6 and TAM molecules under the acidic tumor microenvironment, owing to the pH responsive transition of TAM from hydrophobic to hydrophilic. Upon systemic administration, such HSA–Ce6/TAM nanoparticles exhibit prolonged blood circulation and high accumulation in the tumor, where it would undergo rapid pH responsive dissociation to enable obviously enhanced intratumoral penetration of HSA–Ce6. Furthermore, utilizing the ability of TAM in reducing the oxygen consumption of cancer cells, it is found that HSA–Ce6/TAM after systemic administration could efficiently attenuate the tumor hypoxia status. Those effects acting together lead to remarkably enhanced PDT treatment. This work presents a rather simple approach to fabricate smart nano‐PSs with multiple functions integrated into a single system via self‐assembly of all‐biocompatible components, promising for the next generation cancer PDT.