Cell encapsulation is an alternative to the use of immunosuppressant drugs after cell transplantation. It shields cells from the host immune system, allowing the diffusion of nutrients and oxygen¹. The alginate - poly-L-lysine – alginate system is the most well-studied method², but biocompatibility issues were reported³. This work aims to use methacrylated gellan gum (GG-MA), an anionic heteropolysaccharide, to engineer the microenvironment provided in cell encapsulation strategies. Capsules were formed by gravitational dripping, extruding GG-MA into a Poly-L-Lysine (PLL) bath⁴. Due to the interaction between the carboxylic groups of the GG-MA and the charged PLL amines, a capsule is formed. Morphology was assessed using scanning electron microscopy and micrographs, revealing a diameter of 2.3 ± 0.145 mm. Drug release capacity was quantified using albumin–fluorescein isothiocyanate conjugate (BSA-FITC, 66 kDa) as a model of large glomerular molecules; methylene Blue (MB, 319.85 Da) as a small molecule model; and Dextran-FITC with 4, 20 and 70kDa. While small molecules (MB and 4kDa Dextran-FITC) were rapidly released, the larger molecules had a hampered flow. In vitro tests, using hASC, have shown that cells remain viable after 7 days of culture. In vivo results, using CD1 mice, have shown that GG/PLL complexes do not elicit fibroblast deposition and can tune the microenvironment, from bioactive to biotolerable. Briefly, the results herein presented show the potential of GG-MA/PLL capsules for cell encapsulation as they are: (i) easy to produce, using one-step only; (ii) have selective permeability; (iii) hASC maintained their viability after encapsulation; and (iv) biocompatible.

References:

1 - L. Gasperini, J. F. Mano and R. L. Reis, J. R. Soc. Interface, 2014, 11, 20140817–20140817.

2 - S. V. Bhujbal, B. de Haan, S. P. Niclou and P. de Vos, Sci. Rep., 2014, 4, 6856.

3 - I. Ortega-Oller, M. Padial-Molina, P. Galindo-Moreno, et al., Biomed Res. Int., 2015, 1–18.

4 - S. Vieira, J. Silva-Correia, J.M Oliveira, R.L. Reis, PCT/IB2016/057077.

Acknowledgments:

Sílvia Vieira was awarded a FCT PhD scholarship (SFRH/BD/102710/2014). The FCT distinction attributed to J. Miguel Oliveira under the Investigator FCT program (IF/00423/2012 and IF/01285/2015) is also greatly acknowledged. Alain da Silva Morais acknowledges ERC-2012-ADG 20120216–321266 (ComplexiTE) for his Postdoc scholarship.