Poly(acrylamide) Spheroids with Tunable Elasticity for Scalable Cell Culture Applications

Many biological tissues resemble hydrogels and display Young's moduli below 50 kPa, corresponding to most cell types for the natural environmental conditions to grow. Contrastingly, conventional cell culture usually involves rigid substrates resulting in stiff priming effects, which are of increasing concern when it comes to scalable culturing of adhesive cells for regenerative purposes. As a solution to this problem, the employment of synthetic poly(acryl amide) (PAAm)-based hydrogel beads with tissue-matched mechanical properties are proposed as soft matrix for culture modes suitable for tidal bioreactor culture. Here, technology is described to generate spherical, mm-scaled PAAm hydrogel beads with adjustable, soft elastic properties that are produced by a continuous microfluidic approach. A simple and robust method is demonstrated to functionalize the spheroids with protein ligands, and the suitability of the matrix for cell cultivation is successfully demonstrated with three different cell types (murine mesenchymal stem cells, renal carcinoma cells, and human induced pluripotent stem cells) in model experiments and in a tidal bioreactor system. This versatile approach will pave the way toward novel cell culture systems based on bioreactors that allow scalable, soft carrier-based expansion of cells on matrices with tissue-matched elasticity.