Self-supporting nanoporous alumina membranes as substrates for hepatic cell cultures

Membranes made from nanoporous alumina exhibit interesting properties for their use in biomedical research. They show high porosity and the pore diameters can be easily adjusted in a reproducible manner. Nanoporous alumina membranes are thus ideal substrates for the cultivation of polar cells (e.g., hepatocytes) or the establishment of indirect co-cultures. The porous nature of the material allows supply of nutrients to both sides of adherent cells and the exchange of molecules across the membrane. However, it is well-known that surface features in the nanometer range affect cellular behavior. In this study, the response of HepG2 cells to nanoporous alumina membranes with three different pore diameters, ranging from 50 to 250 nm, has been evaluated. The cellular interactions with the nanoporous materials were assessed by investigating cell adhesion, morphology, and proliferation. Cell functionality was measured by means of albumin production. The membranes supported good cell adhesion and spreading. Compared to tissue culture plastic, the cells on the porous substrates developed distinct focal adhesion sites and actin stress fibers. Additionally, electron microscopical investigations revealed the penetration of cellular extensions into pores with diameters bigger than 200 nm. Furthermore, cell proliferation significantly increased with an increase in pore diameter, whereas the albumin production followed a reverse trend. Thus, it seems to be possible to direct cellular behavior of HepG2 cells growing on nanoporous alumina by changing the pore diameter of the material. Hence, nanoporous alumina membranes can be useful culture substrates to develop new approaches in the field of liver tissue engineering.