• Three-dimensional spheroids as in vitro models for testing iron oxide nanoparticle-based drug delivery system: a review
  • Akram Ahvaraki,1 Zeinab Bagheri,2,*
    1. Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran
    2. Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran


  • Introduction: Cancer is the second leading cause of death worldwide and one of the diseases whose detection and treatment methods will soon undergo significant changes with the application of nanomedicine. Chemotherapy, along with surgery and radiation therapy, is one of the most common cancer treatments. For this reason, physicians and researchers have made significant efforts to optimize the drug's action and minimize side effects. The development of appropriate drug delivery systems represents a significant problem in cancer-targeted therapy. Various nanocarriers with exciting features have been demonstrated as the most effective carriers in this field. magnetic nanoparticles including Fe3O4 and γFe2O3 have outstanding biocompatibility and low toxicity. Thus, these two nano-oxides are extensively utilized in the targeted drug delivery, bioseparation, magnetic fluid hyperthermia, and magnetic resonance imaging. Recently, the three-dimensional spheroid tumor models have been recognized as an intermediate step between in vitro and in vivo models, increasing their biological relevance in research fields such as tumor biology and drug screening. Spheroids display a three-layered organization that containing proliferative, quiescent, and necrotic cells. The spheroid outer layer is made of highly proliferative cells with unrestricted access to oxygen and nutrients, and quiescent cells are found in the spheroid's middle layer, while necrotic cells are present in spheroids inner layer, being excluded of oxygen and nutrients. Due to spheroids' structural similarities with the in vivo solid tumors can be used to predict nanomedicines' tumoral penetration capacity and their optimal physicochemical properties.
  • Methods: The magnetic attributes of iron oxide nanoparticles (IONPs) depend on their composition and morphology. Thus, the synthetic method needs to be carefully selected, ensuring control over the particles' shape, size distribution, and crystallinity. IONPs can be produced in three different ways, encompassing chemical, physical, and biosynthetic methods. Chemical approaches are employed in the vast majority of cases. Physical methods, which include powder ball milling, electron beam lithography, aerosol, and gas-phase deposition, suffer from the lack of ability to control the size of particles in the nanometer size range. Biological methods rely on reduction-oxidation reactions, in which microbial enzymes or plant phytochemicals are responsible for reducing salts into IONPs. However, the yield of such methods is low, and the size distribution is broad. For example, Hernández et.al. synthesized excellent IONPs for drug delivery application. They mixed iron (III) chloride hexahydrate with ammonia solution to produce a strong alkaline suspension. The size and shape of the nanoparticles can be controlled by modifying parameters such as temperature, pressure, and reaction time achieving sizes of 10–200 nm. Shen et al. developed a microemulsion method for synthesizing larger particles of IONPs that is a very critical feature in drug delivery application.
  • Results: Perez et al reported a method to reduce the maturation time required for cohesive spheroid formation.In this work, iron oxide nanoparticles conjugated with doxorubicin, average diameter 8 nm, were produced by an iron salt coprecipitation. The relationship between spheroid size and spheroid maturation was measured to demonstrate the application of these spheroids in drug screening and toxicity assessments. In other research, Don N. Ho et al, reported a 3D platform was designed to study the penetration of nanoparticles into tumors that tested with a model NP, tumstatin-Fe3O4 NPs. Their results showed that tumstatin-Fe3O4 NPs could specifically target the endothelial cells in a complex 3D microtissue environment. To determine the effects of free and SPION-bound paclitaxel (Ptx) in 3D cell culture, Luget et al, reported 2D and 3D cell culture experiments suggested that SPIONLA-HSA-Ptx is a potential system for magnetically based targeted drug delivery to different breast cancer tumors.
  • Conclusion: Fe3O4 NPs are one of the most widely used NPs that are clinically safe and able to act as therapeutics in cancer therapy. also, tumor spheroids that mimic the solid tumor properties, are considered to be a significant platform to evaluate the delivery of anticancer drugs.
  • Keywords: magnetic nanoparticles,nanomedicine,drug delivery,spheroid,cancer