Layer-by-layer (LbL) is a self-assembly-driven surface modification strategy that allows the construction of nanostructured films. Although LbL has been mostly limited to the modification of planar surfaces, its potential lies in the capability to be extrapolated to 3D structures and coat increasingly complex geometries.
During the last year, we were able to extrapolate LbL to the third dimension and conceive spherical devices entirely delimited by multilayer polymeric coatings. Namely, we produced millimetric liquefied viscous alginate droplets coated entirely with LbL films. Confined within this viscous medium, multifunctional elements of smaller scales – nano and microscales – could be suspended, providing hierarchical organization and customized properties. Inspired by the compartmentalized nature of a cell, we demonstrated that this kind of LbL-delimited liquefied environments can be customized to contain and exhibit functionalities that are not found coupled in nature.
Thus we demonstrated that a three-dimensional LbL functionalization permits the confinement of several components – such as biological components, active agents and inorganic nanoparticles – within a controlled environment. These elements can exhibit properties that are desirable in biomedical applications, such as the provision of anchorage points for encapsulated cells (ensuring their survival), smart responsiveness to external stimuli (to tune the permeability of LbL-delimited compartments) and spatial arrangement (to ensure their maximum efficacy) [1-3]. We plan to continue to take advantage of a system of this nature which will be useful in the long-term for the production of micro-tissues, targeted implantable and drug release properties for local tissue regeneration, and drug-screening purposes for disease models.
 C.R. Correia, R.L. Reis, J.F. Mano, Biomacromolecules 14, 743 (2013)
 C.R. Correia, P. Sher, R.L. Reis, J.F. Mano, Soft Matter 9, 2125 (2013)
 R.R. Costa, E. Castro-Otero, F.J. Arias, J.C. Rodríguez-Cabello, J.F. Mano, Biomacromolecules, in press (2013)