Bromelain-facilitated GNPs: A strategic innate anticancer delivery system for methotrexate into osteosarcoma cells

Osteosarcoma is the most common malignant bone tumor in children and adolescents during rapid bone growth. Traditional chemotherapy has markedly improved patient outcomes but suffers from nonspecific side effects due to nonspecific drug distribution, highlighting the need for targeted therapies. Methotrexate, although effective, poses toxicity concerns and prompts exploration into advanced drug delivery systems like nanoparticles. Here, we developed a novel method of synthesizing gold nanoparticles using bromelain (G-BNPs) as a reducing and capping agent, and we conjugated G-BNPs with methotrexate (G-B-MNPs) via 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide (EDC/NHS) as crosslinker. Our meticulous characterization, which included UV–visible spectroscopy, Transmission electron microscopy (TEM), Dynamic light scattering (DLS), Zeta potential, and Fourier-transform infrared spectroscopy (FTIR) analyses confirmed the successful fabrication and drug conjugation of the G-BNPs. We then evaluated the cytotoxicity of the G-BNPs (sized ∼ 21 nm) and G-B-MNPs (sized ∼ 24 nm) on the osteosarcoma cell lines, Saos-2 and MG-63, as well as the non-cancerous primary osteoblast cells. Our findings revealed that G-B-MNPs significantly increased the cytotoxic impact on osteosarcoma cells compared to methotrexate alone while showing minimal toxicity toward primary osteoblast cells. Importantly, using 4`,6-diamidino-2-phenylindole(DAPI), we demonstrated that G-B-MNPs were delivered directly into the nucleus of the cells without encountering lysosomes. G-B-MNPs can be considered a potential drug delivery method for osteosarcoma treatment by improving effectiveness and reducing adverse effects, thereby enhancing patient prognosis.