We report calcium phosphate (CaP) nanocapsule–crowned multiwalled carbon nanotubes (CNT–GSH–G4–CaP) as a novel platform for the intracellular delivery of an anticancer drug. As a proof of concept, the CNT–GSH–G4–CaP system demonstrates the release of the anticancer drug doxorubicin hydrochloride (DOX) within intracellular lysosomes from the interior cavity of the CNT through pH-triggered CaP dissolution.

Importantly, we found that CNTs capped with a CaP nanolid can efficiently prevent premature drug release at physiological pH, while promoting DOX release in more acidic environments, such as those found in subcellular compartments like lysosomes (pH ≈ 5.0).

This “zero premature release” characteristic is of significant clinical importance for delivering cytotoxic drugs, as it helps reduce systemic toxicity and enhances the effectiveness of anticancer treatment.

We envision that this pH-triggered CaP-crowned CNT nanosystem could lead to a new generation of self-regulated platforms for the intracellular delivery of a wide range of anticancer drugs.