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Abstract Breast cancer therapy has significantly advanced by targeting the programmed cell death-ligand 1/programmed cell death-1 (PD-L1/PD-1) pathway. BMS-202 (a smallmolecule PD-L1 inhibitor) induces PD-L1 dimerization to block PD-1/PD-L1 interactions, allowing the T-cell-mediated immune response to kill tumor cells. However, immunotherapy alone has limited effects. Clinically approved photodynamic therapy (PDT) activates immunity and selectively targets malignant cells. However, PDT aggravates hypoxia, which may compromise its therapeutic efficacy and promote tumor metastasis. We designed a tumor-specific delivery nanoplatform of liposomes that encapsulate the hypoxia-sensitive antitumor drug tirapazamine (TPZ) and the small-molecule immunosuppressant BMS. New indocyanine green (IR820)-loaded polyethylenimine-folic acid (PEI-FA) was complexed with TPZ and BMS-loaded liposomes via electrostatic interactions to form lipid nanocomposites. This nanoplatform can be triggered by near-infrared irradiation to induce PDT, resulting in a hypoxic tumor environment and activation of the prodrug TPZ to achieve efficient chemotherapy. The in vitro and in vivo studies demonstrated excellent combined PDT, chemotherapy, and immunotherapy effects on the regression of distant tumors and lung metastases, providing a reference method for the preparation of targeted agents for treating breast cancer. Graphical abstract

Abstract Background Oral chemotherapy is preferred for patients with cancer owing to its multiple advantages, including convenience, better patient compliance, and improved safety. Nevertheless, various physical barriers exist in this route that hamper the development of oral chemotherapeutic formulations, including destruction of drugs in the gastrointestinal tract (GIT), low permeability in enterocytes, and short residence time in the intestine. To overcome these limitations, it is necessary to design an efficient oral drug delivery system with high efficacy and improved safety. Results Herein, we designed novel glycocholic acid (GCA)-functionalized double layer nanoparticles (GCA-NPs), which can act via an endogenous pathway and in a temporally controlled manner in the intestine, to enhance the oral bioavailability of hydrophobic chemotherapeutic drugs such as paclitaxel (PTX). GCA-NPs were composed of quercetin (Qu)-modified liposomes (QL) coated with GCA-chitosan oligosaccharide conjugate (GCOS). The GCA-NPs thus prepared showed prolonged intestinal retention time and good GIT stability due to the presence of chitosan oligosaccharide (COS) and enhanced active transportation via intestinal apical sodium-dependent bile acid transporter (ASBT) due to the presence of GCA. GCA-NPs also efficiently inhibited intestinal P-gp induced by Qu. PTX-loaded GCA-NPs (PTX@GCA-NPs) had a particle size of 84 nm and an entrapment efficiency of 98% with good stability. As a result, the oral bioavailability of PTX was increased 19-fold compared to that of oral Taxol® at the same dose. Oral PTX@GCA-NPs displayed superior antitumor efficacy and better safety than Taxol® when administered intravenously. Conclusions Our novel drug delivery system showed remarkable efficacy in overcoming multiple limitations and is a promising carrier for oral delivery of multiple drugs, which addresses several challenges in oral delivery in the clinical context. Graphical Abstract