Increased glutamine uptake toward the elevated glutaminolysis is one of the hallmarks of tumour cells. This aberrant glutamine metabolism has recently attracted considerable attention as a diagnostic and therapeutic target. Herein, we developed glutamine-functionalized polymer to achieve a selective high affinity to tumour cells overexpressing glutaminolysis-related transporter ASCT2. In in vitro study, our developed polymer exhibited faster and higher cellular uptake in tumour cells than that in normal cells. Uptake inhibition study revealed the dominant contribution of ASCT2 to the polymer-cell interaction. Furthermore, the binding affinity of the polymer to tumour cells was estimated to be comparable to that of the potent ligand molecules reported in the literature. In in vivo study, the polymer showed prolonged retention at tumour site after intratumoral injection. This study offers a novel approach for designing tumour cell-binding synthetic polymers through the recognition of dense transporters related to tumour-associated metabolism.

Tannic acid (TA) can form stable complexes with proteins, attracting significant attention as protein delivery systems. However, its systemic application has been limited due to nonspecific interaction. Here, we report a simple technique to prepare systemically applicable protein delivery systems using sequential self-assembly of a protein, TA, and phenylboronic acid-conjugated PEG-poly(amino acid) block copolymers in aqueous solution. Mixing the protein and TA in aqueous solution led to covering of the protein with TA, and subsequent addition of the copolymer resulted in the formation of boronate esters between TA and copolymers, constructing the core−shell-type ternary complex. The ternary complex covered with PEG exhibited a small hydrodynamic diameter of ∼10−20 nm and prevented an unfavorable interaction with serum components, thereby accomplishing significantly prolonged blood circulation and enhanced tumor accumulation in a subcutaneous tumor model. The technique utilizing supramolecular self-assembly may serve as a novel approach for designing protein delivery systems.

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