Recombinant Trichosanthin-Loaded Nanoparticles with Tumor-Targeting and Cell-Penetrating Capabilities for Activatable Antitumor Therapy

Trichosanthin (TCS), a type I ribosome-inactivating protein, exerts its cytotoxic effects by inhibiting protein synthesis through depurination of 28S rRNA, resulting in apoptosis and cancer cell death. However, insufficient tumor specificity and limited cell-penetrating capabilities have restricted its applications. Herein, we engineered a recombinant TCS by inserting low-molecular-weight protamine (LMWP) and matrix metalloproteinase-selective peptide (MSP), thereby constructing a recombinant fusion protein (rTCS-LMWP-MSP, namely, rTLM) with enhanced tumor-targeting and cell-penetrating capabilities. Subsequently, manganese-doped calcium phosphate (MnCaP) nanoparticles were fabricated by bovine serum albumin (BSA)-templated mineralization to serve as a pH-responsive delivery system, which not only improves the biocompatibility of rTLM but also enables payload release activated by the acidic tumor microenvironment. Upon accumulation of BSA-MnCaP-rTLM in tumor tissues, the extracellular matrix metalloproteinase 2 (MMP2) could recognize and cleave MSP. This process not only enables tumor-targeting capability but also exposes the inserted LMWP to enhance cell-penetrating capability. When internalized by tumor cells, BSA-MnCaP could be degraded, leading to the release of rTCS-LMWP, which induces cell apoptosis. Simultaneously, the released Mn²⁺ ions catalyze the conversion of endogenous H₂O₂ into harmful hydroxyl radicals via a Fenton-like reaction, thus promoting the oxidative stress in tumor cells. Both in vitro and in vivo experiments confirmed the synergistic antitumor effects of BSA-MnCaP-rTLM. Our findings indicate that BSA-MnCaP-rTLM holds significant potential for effective cancer treatment.