Biomimetic microcavities based on poly(dimethylsiloxane) elastomers

Abstract

We report on a new technology for preparing biomimetic cell culture carriers based on poly(dimethylsiloxane) (PDMS) to provide precisely defined microcavities combined with an option for covalent attachment of functional biomolecules. PDMS molds with a microcavity size of 10–80 µm in diameter and a depth of 10 µm were modified by a covalently attached poly(ethene-alt-maleic anhydride) layer to allow covalent or physisorptive attachment of biomolecules ranging from extracellular matrix proteins through growth factors to glycosaminoglycans. The poly(ethene-alt-maleic anhydride) layer furthermore provided an effective shielding for the possible diffusion of small silicone components out of the PDMS bulk substrate. We employ the immobilization technology to the extracellular matrix components fibronectin, laminin, heparin, and hyaluronic acid in defined surface amounts with 1.4 × 10¹² fibronectin ligands per cm², 5.2 × 10¹¹laminin ligands per cm², 5.6 × 10¹⁴heparin disaccharide units per cm², and 6 × 10¹⁴hyaluronic acid disaccharide units per cm². The functional utilization of the biomimetic microcavities as versatile and robust scaffolds for controlling and investigating cell fate decisions was demonstrated for hematopoietic stem cells (HSC). The effect of microcavity size shows up in decreased proliferative activity of the cells on heparin-coated microcavities of 15 µm diameter in comparison to 40 µm ones. This behavior is superimposed by an additional decrease in proliferation of HSC on fibronectin versusheparin coatings. A stable HSC surface marker expression (CD34 and CD133) on proliferation suppressing small microcavities and the high viability of the cells suggested a more quiescent state due to an enhanced contact of HSC with the presented extracellular matrix.