LAUSR

Abstract It is essential to overcome many biological barriers and deliver theranostic agents to tumor sites. As a basic property of nanoagents, particle size plays an important role in the whole delivery process. However, at different delivery stages, the optimal particle sizes are different. Therefore, it is difficult for nanoagents with fixed size to achieve satisfactory outcomes in every process. To overcome the dilemma caused by size paradox, a size-changeable strategy has been proposed for designing theranostic nanoagents. In general, the size-changeable theranostic agents have an initial size favorable for efficient tumor accumulation. Under certain stimulus, their size can alter on demand to enhance the efficacies of tumor imaging and therapy. In this review, the latest progresses and biomedical applications of size-changeable theranostic nanoagents are systematically summarized. The perspectives and challenges of size-changeable strategy for cancer theranostics are also discussed.