The protein system auto-assembles from aqueous solution into “membranes” that are both stable and sterilizable, with a dense protein monolayer where every protein molecule is in the correct orientation. Chosen concentrations of peptide motifs are achieved by using “filler” molecules for dilution and to fill any remaining membrane gaps. The filler molecules can be hydrophobic, hydrophilic, or functionalized to enable the patterning or printing of surfaces. For example, the use of a PEG filler will inhibit cell adhesion, enabling scientists to examine cell adhesion and mobility characteristics.
As a result, scientists can present cells with peptide motifs in any concentration, mixture, or ratio—on surfaces and media that are animal-free and fully characterized and with proteins presented to cells in the correct orientation as well as in a naturalistic protein loop manner.
These next-generation products overcome variability issues. Their innate reproducibility enables scientists to investigate the ideal growth conditions for a chosen cell line—and then to apply meaningful assay parameters to understand cell behavior.
To date, these systems have been used with a wide range of mammalian cells (including neural, hepatocyte, chondrocyte, and other cell lines) and also human embryonic stem cells. The applications range from studies of cell adhesion, mobility, differentiation, and fate to the development of assay conditions allowing metabolic investigation and screening. A good example of this kind of behavior has been shown in recent adhesion studies done on neural cells (Figure 3).
It is already becoming clear that extracellular matrix proteins contain numerous domains and motifs, each of which can be a target for receptors expressed on the surface of cells. Even within a single protein, these motifs can be synergistic or antagonistic in effect. Sometimes the effect of using multiple motifs is predictable; in other cases a combination of motifs results in a totally different cell effect to that which might have been predicted from the study of individual motifs.
Nature is complex, and there is still a lot to be learned about cells. Nevertheless, the availability of well-characterized and affordable products facilitates the study of mammalian cell characteristics and helps to assemble the knowledge required to move toward research, development, and clinical solutions.