Exploring and leveraging aggregation effects on reactive oxygen species generation in photodynamic therapy

Abstract Aggregate‐level photodynamic therapy (PDT) has attracted significant interest and driven substantial advances in multifunction phototheranostic platforms. As exemplified by two typical instances of aggregation‐caused quenching of reactive oxygen species (ROS) and aggregation‐induced generation of ROS, the aggregation effect plays a significant role on the ROS generation of photosensitizers (PSs), which is worthy of in‐depth exploration and full utilization. However, in contrast to the well‐developed researches on the aggregation effect on luminescence, the studies concerning the aggregation effect on ROS generation are currently in a relatively nascent and disjointed stage, lacking guidance from a firmly established research paradigm. To advance this regard, this review aims at providing a consolidated overview of the fundamental principles and research status of aggregation effects on the ROS generation. Here, the research status can be organized into two main facets. One involves the comparison between isolated state and aggregated state, which is mainly conducted by two methods of changing solvent environments and adding adjuvants into a given solvent. The other underscores the distinctions between different aggregate states, consisting of three parts, namely comparison within the same or between different categories based on the classification of single‐component and multicomponent aggregates. In this endeavor, we will present our views on current research methodologies that explore how aggregation affects ROS generation and highlight the design strategies to leverage the aggregation effect to optimize PS regiments. We aspire this review to propel the advancement of phototheranostic platforms and accelerate the clinical implementation of precision medicine, and inspire more contributions to aggregate‐level photophysics and photochemistry, pushing the aggregate science and materials forward.