Cell encapsulation in biomaterial microcompartments is a useful tool to deliver protected cell cargo into defective tissues. However, the processing of micrometric structures is often dependent on the use of typical emulsion agents, including oils and organic solvents. Those are often related with poor cell viability, or require complicated washing procedures to retrieve oil-free cell-laden materials. All-aqueous processing methodologies arose as promising strategies to process biomaterials with high cytocompatibility. Aqueous two-phase systems have been used as surrogates of classical water/oil-based emulsions to enable phase separation to enable the formation of, for example, microparticles. Experimental approaches similar to the ones widely explored for classical emulsion systems for biomaterial fabrication – including their adaptation into electrospraying or microfluidics-based techniques - have led to the formation of mostly spherical structures, which mostly comprise either continuous biomaterial beads, or hollow capsules obtained upon interfacial reactions. Concerning the latter, the interfacial complexation of polyelectrolytes at the interface of millimetric and micrometric droplets has enabled the cytocompatible encapsulation of mesenchymal stem cells along with adhesive microparticles . However, unlike the preparation of thermodynamically stable spherical objects at the interface of emulsions, the preparation of soft compartments with other shapes has proven challenging. Although previous attempts have been made to fix the shape of objects at the interface of aqueous emulsions, structures capable of being handled outside of the emulsion interface could not be obtained. We here report an advance on the all-aqueous fabrication of continuous, non-leaky self-standing biomaterial tubes, capable of withstanding cell adhesion on their walls. Another versatile aspect of materials prepared using all-aqueous emulsions is related to the formation of multicompartment complex hollow structures assembled upon the establishment of specific processing parameters. Those were useful in spontaneously separating micrometric objects in different compartments enabling, for example, the encapsulation of viable cells in specific locations of multiwalled structures. The versatility achieved with the use of all-aqueous emulsions may be used to enable the fabrication of advanced biomaterials that may combine tailored release profiles of bioactive molecules with the exact positioning and protection of cells.
 Vilabril, S., Nadine, S., Neves, C. M. S. S., Correia, C. R., Freire, M. G., Coutinho, J. A. P., Oliveira, M. B., Mano, J. F., One-Step All-Aqueous Interfacial Assembly of Robust Membranes for Long-Term Encapsulation and Culture of Adherent Stem/Stromal Cells. Adv. Healthcare Mater. 2021, 10, 2100266.
This work was financially supported by the European Research Council grant agreement ERC-2014-ADG-669858 (project ATLAS), by the Programa Operacional Competitividade e Internacionalizacã̧o, in the component FEDER, and by national funds (OE) through FCT/MCTES, in the scope of the projects ‘TranSphera’ (PTDC/BTM-ORG/30770/2017) and “CellFi” (PTDC/BTM-ORG/3215/2020), and developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MEC (PIDDAC).