The continuous demand for tissue engineering strategies with improved/enhanced performance often challenges the balance between biomaterials characteristics and techniques specificities. The outcome often results in cell-compromising processing conditions (e.g., prolonged experimental procedures where cells are maintained at extreme temperatures and/or non-physiological environments). One important factor often disregarded is the osmotic pressure to which cells are exposed to. We addressed this stress condition using an in-house microfluidic system. Addition of an osmotic regulator to our cell encapsulation system significantly benefits the generation of viable cell-laden hydrogels under harsh processing conditions. Human adipose-derived stem cells (hASCs) were resuspended in alginate and Gellan Gum (GG) solutions containing different concentrations (0.12M, 0.25M and 1.5M) of sucrose as osmotic regulator. GG (in water) and alginate (in water or PBS) solutions were used to vary the conditions under which cells were kept prior processing. Independently of the polymer, addition of sucrose did not affect the processing conditions or the viscosity of the solutions, except at 1.5M as expected. Cell viability was assessed up to 2h of processing time. The obtained results clearly demonstrate that inclusion of 0.25M sucrose during processing of the cell-laden hydrogels allowed to keep cell viability around 80%, in opposition to the 20% observed in its absence, both for GG and alginate-derived hydrogels prepared in water. Impressively, the level of cell viability observed with the inclusion of 0.25M sucrose, 76% for GG and 86% for alginate, was similar to the one obtained with the standard alginate solution prepared in PBS (82%). Improvement in cell viability due to the presence of sucrose was observed within the first 5 minutes of processing and was maintained for prolonged experimental setups with viability values above 50%, even after a 2h time-frame and independently of the material.
The authors would like to acknowledge the Portuguese Foundation for Science and Technology (FCT) for personal grant SFRH/BPD/109595/2015 (AFC). This work was supported by the European Research Council Advanced Grant No. ERC-2012-AdG_20120216-321266 for project ComplexiTE.