TF and cancer: The researchers used cancer cell-specific ligands as targets to make the delivery system have active targeting to improve the limitations of EPR effect, for example, folic acid (Scaranti et al., 2020), hyaluronic acid (Xiong et al., 2020), peptide (Cooper et al., 2021), transferrin (Yu et al., 2020), etc. They can easily enter cancer cells through receptor-mediated endocytosis, rather than relying solely on the EPR effect.