Biomaterials for Three-Dimensional Cell Culture: From Applications in Oncology to Nanotechnology

Abstract

Three-dimensional cell culture has revolutionized cellular biology research and opened the door to novel discoveries in terms of cellular behavior and response to microenvironment stimuli. Different types of 3D culture exist today, including hydrogel scaffold-based models, which possess a complex structure mimicking the extracellular matrix. These hydrogels can be made of polymers (natural or synthetic) or low-molecular weight gelators that, via the supramolecular assembly of molecules, allow the production of a reproducible hydrogel with tunable mechanical properties. When cancer cells are grown in this type of hydrogel, they develop into multicellular tumor spheroids (MCTS). Three-dimensional (3D) cancer culture combined with a complex microenvironment that consists of a platform to study tumor development and also to assess the toxicity of physico-chemical entities such as ions, molecules or particles. With the emergence of nanoparticles of different origins and natures, implementing a reproducible in vitro model that consists of a bio-indicator for nano-toxicity assays is inevitable. However, the maneuver process of such a bio-indicator requires the implementation of a repeatable system that undergoes an exhaustive follow-up. Hence, the biggest challenge in this matter is the reproducibility of the MCTS and the associated full-scale characterization of this system's components.

Keywords: 3D cell culture; nano-toxicity; nanoparticles; oncology.

Figure 1

2D vs. 3D cell culture: (A) Cell behavior in 2D conventional cell culture. Cells cultured in a 2D manner tend to have a flat shape that does not represent the real physiological cell morphology. (B) Cell behavior in 3D cell culture. Cells cultured in a 3D system are present in a microenvironment similar to that in vivo, therefore they have a more representative morphology and behavior

Figure 2

Types of 3D systems. 3D systems fall into two categories either scaffold-free or scaffold-based systems. Scaffold-free systems depend greatly on the plate where the cells are culture whether it is (A) ultra-low attachment plate for the production of cell aggregates as spheroids or (B) Extracellular matrix (ECM) coated plates for cell differentiation into organoids. Scaffold-based systems are manmade microenvironments that can host cells whether they are (C) solid scaffolds that offer a rigid matrix and allow spheroid formation or (D) soft scaffolds like hydrogels that contain an ECM-like complex architecture in which multicellular tumor spheroids (MCTS) are produced similar to solid in vivo tumors.

Figure 3

Examples of low-molecular-weight gelators (LMWG) structures. LMWG are either carbohydrate-based, such as (a) N-heptylgalactonamide or (b) N-acetyl glucosamine, or they can be peptide-based, such as (c) FmocFF or (d) FEFEFKFK peptide. Alternatively, they can be nucleic acid-based such as (e) N-acyl cytidine derivative or (f) Nucleotide lipid (diC16dC).

Figure 4

Initial state t0 vs. final state tf of the MCTS. In order to assess the effectiveness of the bio-indicator, a comparison between t0 and tf is inevitable for the understanding of the impact of NPs on the living in vitro 3D model.