Fine-tuning of liposome integrity for differentiated transcytosis and enhanced antitumor efficacy.

Transcytosis-inducing nanomedicines have been developed to improve tumor extravasation. However, the fate during transcytosis across multicell layers and the structural integrity of the nanomedicines before reaching tumor cells could impact antitumor therapy. Here, a BAY 87-2243 (a hypoxia-inducible factor-1 inhibitor)-loaded liposomal system (HA-P-LBAY) modified by low molecular weight protamine (LMWP) and crosslinked by hyaluronic acid (HA) was constructed. This system could accomplish differentiate cellular transport in endothelial and tumor cells by fine-tuning its structural integrity, i.e. transcytosis across the endothelial cells while preserving structural integrity, facilitating subsequent retention and drug release within tumor cells via degradation-induced aggregation. In vitro cellular uptake and transwell studies demonstrated that HA-P-LBAY were internalized by endothelial cells (bEnd.3) via an active, caveolin and heparin sulfate proteoglycan (HSPG)-mediated endocytosis, and subsequently achieved transcytosis mainly through the ER/Golgi pathway. Moreover, the fluorescence resonance energy transfer (FRET) study showed that HA-crosslinking maintained higher integrity of HA-P-LBAY after transcytosis, more efficiently than electrostatic coating of HA (HA/P-LBAY). In addition, more HA-P-LBAY was retained in tumor cells (4T1) compared to HA/P-LBAY corresponding to its enhanced in vitro cytotoxicity. This may be attributed to better integrity of HA-P-LBAY post endothelial transcytosis and more degradation of HA in tumor cells, leading to more liposome aggregation and inhibition of their transcytosis, which was inferred by both TEM images and the HAase responsiveness assay proved by FRET. In vivo, HA-P-LBAY exhibited more potency in tumor suppression than the other formulations in both low and high permeability tumor models. This highlighted that fine-tuning of structural integrity of nanocarriers played a key role no matter whether the transcytosis of nanocarriers contributed to cellular transport. Collectively, this study provides a promising strategy for antitumor therapies by fine-tuning liposome integrity to achieve active trans-endothelial transport with structural integrity and selective aggregation for prolonged tumor retention.