Cellular uptake of anisotropic microparticles in 2D and 3D culture systems

Three-dimensional (3D) cell culture models offer a more physiologically relevant alternative to traditional two-dimensional (2D) cultures by better replicating in vivo microenvironments, including extracellular matrix interactions, cell-cell contacts, and nutrient gradients. While nanoparticle uptake in 3D cultures has been extensively characterized, microparticle internalization remains less explored. Here we evaluate cellular uptake of monodisperse anisotropic hematite microparticles of varying geometry (cubic, ellipsoidal, and rod-shaped), synthesized via a sol-gel method, in both 2D and 3D cultured normal and cancer cell lines. Using a combination of microscopy and spectroscopy, we reveal shape-dependent uptake patterns, with rod-shaped microparticles exhibiting significantly enhanced internalization, particularly within 3D cancer spheroids. Confocal Z-stack imaging further demonstrated deeper penetration of rod-shaped particles into spheroid cores compared to other shapes, underscoring the influence of particle aspect ratio and cellular microenvironment on uptake efficiency. Cytotoxicity assays highlight differential responses in 2D versus 3D cultures, emphasizing the importance of 3D models for evaluating therapeutic platforms. These findings advance the understanding of microparticle behavior in complex tissue-like environments, supporting their potential for improved drug delivery, tissue engineering, and regenerative medicine applications.