Papain grafted into the silica coated iron-based magnetic nanoparticles 'IONPs@SiO₂-PPN' as a new delivery vehicle to the HeLa cells

The present study aims at engineering, fabrication, characterization, and qualifications of papain (PPN) conjugated SiO₂-coated iron oxide nanoparticles 'IONPs@SiO₂-PPN'. Initially fabricated iron oxide nanoparticles (IONPs) were coated with silica (SiO₂) using sol-gel method to hinder the aggregation and to enhance biocompatibility. Next, PPN was loaded as an anticancer agent into the silica coated IONPs (IONPs@SiO₂) for the delivery of papain to the HeLa cancer cells. This fabricated silica-coated based magnetic nanoparticle is introduced as a new physiologically-compatible and stable drug delivery vehicle for delivering of PPN to the HeLa cancer cell line. The IONPs@SiO₂-PPN were characterized using FT-IR, AAS, FESEM, XRD, DLS, and VSM equipment. Silica was amended on the surface of iron oxide nanoparticles (IONPs, γ-Fe₂O₃) to modify its biocompatibility and stability. The solvent evaporation method was used to activate PPN vectorization. The following tests were performed to highlight the compatibility of our proposed delivery vehicle: in vitro toxicity assay, in vivo acute systemic toxicity test, and the histology examination. The results demonstrated that IONPs@SiO₂-PPN successfully reduced the IC₅₀ values compared with the native PPN. Also, the structural alternations of HeLa cells exposed to IONPs@SiO₂-PPN exhibited higher typical hallmarks of apoptosis compared to the cells treated with the native PPN. The in vivo acute toxicity test indicated no clinical signs of distress/discomfort or weight loss in Balb/C mice a week after the intravenous injection of IONPs@SiO₂ (10 mg kg^-1). Besides, the tissues architectures were not affected and the pathological inflammatory alternations detection failed. In conclusion, IONPs@SiO₂-PPN can be chosen as a potent candidate for further medical applications in the future, for instance as a drug delivery vehicle or hyperthermia agent.