Engineered platelets: Advocates for tumor immunotherapy

Platelets are crucial components in the blood circulation mainly responsible for hemostasis, and they are also widely involved in dynamic physiological activities including inflammation regulation, pathogen interactions and tissue regeneration. Inspired by their unique features and functions, platelets have been leveraged as drug delivery carriers for immunotherapeutics or enhancers for tumor immunotherapy. Specifically, with convergence of chemical and biomedical engineering techniques, platelets could be engineered to accumulate selectively and spatial-temporally release immunotherapeutics in the format of micro/nano vesicles (100–1000 nm) at tumor sites, to facilitate to recruitment of other effective immune cells through cytokine production, and synergize with other treatment modalities (e.g., CAR-T cell therapy) to potentiate the efficacy of tumor immunotherapy. Engineered platelets with bioresponsive and immune modulatory functionalities could bring new opportunities for development of nanomedicines and pave a new avenue for enhanced tumor immunotherapy.