From: Three-dimensional in vitro culture models in oncology research
Method of production | Description of the mechanism | Advantages (+)/Disadvantages (−) | References |
---|---|---|---|
Lyophilisation/freeze-drying | Polymers are solubilized in solvent, before being subjected to gelation sublimation of solid polymers (gel or foam) followed by freeze drying under vacuum |  + High porosity and pore interconnectivity – Small pore size − Irregular porosity − Time consuming process (days) − Residual solvent that may be harmful to cells − High energy-consuming | |
SCPL | Insoluble salt particles are added to a solution of polymers solubilized in solvent. After solvent evaporation, a composite of polymers embedded with salt particles is obtained. Repeated washing of the composite with water allows the salt elimination and then the formation of a porous scaffold |  + Simple  + Reproducible  + No specific instrument required − Limited interconnectivity − Time consuming process (days) − Residual solvents that may induce cell damages | [144] |
Gas foaming | Can be done chemically by: i) producing hydrophobic gas bubbles in liquid solution of polymers; ii) physically by subjecting a solid polymer to a high pressure gas that can dissolve into it and expands when the pressure is reduced, thus producing cavities when the bubbles collapse. It can be associated with SCPL |  + High porosity  + Controlled pore size  + Solvent-free − Limited interconnectivity | |
TIPS | Relies on the change in thermal energy to transform a homogeneous mixture of polymer and solvent into a multiple-phase system, composed of a polymer-rich phase (solvent-poor phase) and a polymer-poor phase (solvent rich phase). The solution is quenched below the freezing point of the solvent, and the solvent is removed by freeze-drying |  + Easily implementable  + High interconnectivity  + Easy modulation of pore size and structure − Time consuming process (days) − Residual solvents may induce cell damages − High energy-consuming | |
Electrospinning | A charged liquid with a voltage high enough to counteract surface tension will stretch and erupt into a jet. It will solidify into a fibre when projected on a collector | + High porosity  + High interconnectivity + Low cost  + Most soluble polymers can be used  + Mimic the fibrillar structure of ECM − Complex generation of 3D structure − Residual solvents that may induce cell damages − Small pores that lead to poor cell infiltration and distribution − Low mechanical strength | |
Self-assembly | Spontaneous assembling of monomers into supramolecular nanostructures after exposure to pH or temperature modifications or enzymatic treatment |  + Different types of structure can be generated depending on the synthesis conditions  + Easy to functionalize with various molecules  + Less toxic because does not require cross-linker reagents + Low cost and rapid syntehesis − Difficult to control size of the self-assembled nanostructure − May be unstable under liquid conditions | |
Rapid prototyping | Describes a group of manufacturing processes (e.g. stereolitography, 3D printing, selective laser sintering) that enables fabrication of scaffold layer by layer with precise spatial organization from a computer aided design (CAD) | + High control on pore size, porosity, and interconnectivity + Good resolution  + Good reproducibility − Expensive − Time-consuming (creation of the design) − Potential wasting of polymers − Potential cytotoxicity of the polymers used | [154] |