Entry into cells is necessary for many nanomaterial applications, and a common solution is to functionalize nanoparticles (NPs) with cell-penetrating ligands. Despite intensive studies on these functionalized NPs, little is known about their effect on cellular activities to engulf other cargo from the nearby environment. Here, we use NPs functionalized with TAT (transactivator of transcription) peptide (T-NPs) as an example to investigate their impact on cellular uptake of bystander cargo. We find that T-NP internalization enables cellular uptake of bystander NPs, but not common fluid markers, through a receptor-dependent macropinocytosis pathway. Moreover, the activity of this bystander uptake is stimulated by cysteine presence in the surrounding solution. The cargo selectivity and cysteine regulation are further demonstrated ex vivo and in vivo. These findings reveal another mechanism for NP entry into cells and open up an avenue of studying the interplay among endocytosis, amino acids, and nanomaterial delivery.
Bibliographical noteFunding Information:
Research reported in this publication was supported by grants from the National Cancer Institute (R01CA214550), the National Institutes of Biomedical Imaging and Bioengineering (R21EB022652), and the Beijing Institute of Collaborative Innovation (CSRA 17-11). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
© 2019, The Author(s).
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