Supramolecular Amino Acids‐Encoded Nanodots (SEND) with pH‐ and Ion‐Responsive Phase Separation for Serum‐Tolerant Cytosolic Protein Delivery

To broaden the scope of potential intracellular targets for protein drugs, artificial carriers are employed to achieve efficient cytosolic delivery. However, the majority of delivery vectors are hindered by restricted serum tolerance. Here, the screening of supramolecular amino acids-encoded nanodots (SEND) for efficient serum-tolerant cytosolic protein delivery is reported. A library of 60 nanodots is constructed by surface conjugation of different amino acids or dipeptides on cyanine five-cored polylysine dendrimers. The FR (Phe-Arg) and RW (Arg-Trp) modified SEND achieved efficient intracellular protein delivery in both serum-free and serum-containing conditions, and preserved high protein bioactivity. These two SEND can recruit a wide range of proteins and induce liquid-solid phase separation, thereby preventing the premature leakage of loaded proteins. The phase separation behavior of SEND-FR and -RW is responsive to ionic strength and pH. Moreover, SEND-FR is sensitive to bicarbonate, which promotes the hardening of SEND-FR coacervates through enhanced hydrogen bonding. Lowering the pH triggers reversion to a homogeneous phase, enabling controlled protein release. The SEND-FR is capable of sending toxic protein Saporin to the lung via systemic administration, effectively inhibiting the progression of lung metastasis. This study provides a promising strategy to construct functional nanocarriers for efficient serum-tolerant cytosolic protein delivery.