Biomaterials Tutorial

Microcontact Printing

Derek Mortisen
University of Washington Engineered Biomaterials

The function of many mammalian cell types depends on their specific spatial orientation.  For example, cardiac muscle cells must be oriented end to end, such that they form specialized junctions that allow both electrical conductivity and mechanical force transduction.  This allows cells to contract in unison, and the concerted effort of millions of cells creates the force necessary to pump blood throughout the body.  Without this spatial orientation, cells would simply beat randomly and independently, and the heart would be nothing more than a twitching blob rather than what it is: an efficient pump. 

The purpose of microcontact printing is to provide this specific spatial orientation to cells cultured in vitro, or outside the body.  This allows scientists to study cells outside the body that behave more like cells in their native environment. 

The majority of mammalian cells are anchorage-dependent, and therefore, must adhere to a surface in order to survive.  Cells of this nature attach to a surface through integrins, which are specialized transmembrane proteins that respond to the extracellular environment.  There are several types of integrins, and each responds uniquely to a ligand, which is a protein present in the extracellular matrix.  The nature, number, and orientation of a specific cell’s integrins (and the ligands that it binds to) can profoundly influence the function and survival of that cell. 

Because different cell types have different integrins, it is often necessary to coat the surface of a culture dish with a specific ligand in order to promote cell attachment.  For example, cardiac muscle cells (cardiomyocytes) will not adhere to an uncoated culture dish.  The dish must first be coated with a specific ligand to promote cell attachment, in this case a protein called laminin.  We can take advantage of anchorage dependence to manipulate the orientation of cells in vitro by using microcontact printing to control where ligands are attached to the culture dish.

Microcontact printing uses essentially the same concept as a rubber stamp and an ink pad, only at a much smaller scale.  Patterns are made in a rubbery material to create the stamp. This stamp is “inked” with the desired ligand, and then, the patterned is stamped onto a culture dish [1].  The desired pattern will transfer onto the culture dish, as seen in Figure 1, and cells will adhere to those ligands in the desired pattern.

Figure 1:  In step 1, the stamp is “inked” with the desired ligand suspended in an aqueous buffer solution.  In step 2, the adsorbed proteins are transferred to the desired substrate, leaving a protein pattern as seen in step 3. 

References:

1.      Blawas AS, Reichert WM. Protein patterning. Biomaterials 1998; 19(7-9): 595-609.

2.      McDevitt TC, Angello JC, Whitney ML, Reinecke H, Hauschka SD, Murry CE, Stayton PS. In vitro generation of differentiated cardiac myofibers on micropatterned laminin surfaces. J Biomed Mater Res 2002; 60(3): 472-9.