Optimization of 3D cancer cell culture conditions by application of chemical engineering principles

Abstract

Cancer cell immobilization in polymer hydrogels serving as extracellular matrices and cultivation in perfusion bioreactors that provide appropriate chemical signals, efficient mass transfer and hydrodynamic shear stresses is a promising strategy for development of physiologically relevant tumor models. In this work, perfusion cultures of 2 cancer cell types (C6 rat glioma and embryonal carcinoma NT2/D1 cells) immobilized in alginate microgels were established, while static cultures served as controls. Continuous perfusion had different effects on the cultured cells inducing enhanced proliferation of the glioma cells immobilized in microfibers (8x10^6 cell/ml), while reducing the viability of the NT2/D1 cells immobilized in microbeads (1x10^6 cell/ml). In order to elucidate the observed effects, chemical engineering principles were applied to assess mass transfer and hydrodynamic conditions. The second Fick’s law was solved analytically while the diffusionadvection-reaction equation was solved numerically to model mass transport in the static and bioreactor cultures, respectively. Moreover, Reynolds numbers, pressure drops and shear stresses in bioreactor cultures were calculated for assessment of flow regime and hydrodynamic conditions. The modeling results have indicated that oxygen transport is diffusion-controlled through the alginate hydrogel, while medium perfusion improves mass transfer of larger compounds having smaller diffusion coefficients (∼10^(-13) m^2/s), which possibly stimulated glioma cell proliferation. On the other hand, the obtained shear stress (~50 mPa) in the perfused packed bed of microbeads was above physiological levels, which provided the explanation of the poor NT2/D1 cell survival. This study stresses the importance of multidisciplinary approach in addressing such multifactorial diseases as cancer.