Micropatterned dynamically adhesive substrates for cell migration

Quantitative photochemical immobilization of biomolecules on planar and corrugated substrates: a versatile strategy for creating functional biointerfaces

Methods for the generation of substratespresenting biomolecules in a spatially controlled manner are enabling tools for applications in biosensor systems, microarray technologies, fundamental biological studies and biointerface science. We have implemented a method to create biomolecular patterns by using light to control the direct covalent immobilization of biomolecules onto benzophenone-modified glass substrates. We have generated substrates presenting up to three different biomolecules patterned in sequence, and demonstrate biomolecular photopatterning on corrugated substrates. The chemistry of the underlying monolayer was optimized to incorporate poly(ethylene glycol) to enable adhesive cell adhesion onto patterned extracellular matrix proteins. Substrates were characterized with contact angle goniometry, AFM, and immunofluorescence microscopy. Importantly, radioimmunoassays were performed to quantify the site density of immobilized biomolecules on photopatterned substrates. Retained function of photopatterned proteins was demonstrated both by native ligand recognition and cell adhesion to photopatterned substrates, revealing that substrates generated with this method are suitable for probing specific cell receptor-ligand interactions. This molecularly general photochemical patterning method is an enabling tool for the creation of substrates presenting both biochemical and topographical variation, which is an important feature of many native biointerfaces.

Subcellular spatial segregation of integrin subtypes by patterned multicomponent surfaces

While it is well known that individual integrins are critical mediators of cell behavior, recent work has shown that when multiple types of integrins simultaneously engage the ECM, cell functions are enhanced. However, it is not known how integrins spatially coordinate to regulate cell adhesion because no reliable method exists to segregate integrins on the cell membrane. Here, we use a microcontact printing-based strategy to pattern multiple ECMs that bind distinct integrins in order to study how integrins might interact. In our technique, proteins are first adsorbed uniformly to a poly(dimethyl siloxane) stamp, and then selectively "de-inked." Our strategy overcomes several inherent limitations of conventional microcontact printing, including stamp collapse and limited functionality of the surface patterns. We show that integrins spatially segregate on surfaces patterned with multiple ECMs, as expected. Interestingly, despite spatial segregation of distinct integrins, cells could form adhesions and migrate across multicomponent surfaces as well as they do on single component surfaces. Together, our data indicate that although cells can segregate individual integrins on the cell surface to mediate ECM-specific binding, integrins function cooperatively to guide cell adhesion and migration.

Micropatterning as a tool to decipher cell morphogenesis and functions

In situ, cells are highly sensitive to geometrical and mechanical constraints from their microenvironment. These parameters are, however, uncontrolled under classic culture conditions, which are thus highly artefactual. Micro-engineering techniques provide tools to modify the chemical properties of cell culture substrates at sub-cellular scales. These can be used to restrict the location and shape of the substrate regions, in which cells can attach, so-called micropatterns. Recent progress in micropatterning techniques has enabled the control of most of the crucial parameters of the cell microenvironment. Engineered micropatterns can provide a micrometer-scale, soft, 3-dimensional, complex and dynamic microenvironment for individual cells or for multi-cellular arrangements. Although artificial, micropatterned substrates allow the reconstitution of physiological in situ conditions for controlled in vitro cell culture and have been used to reveal fundamental cell morphogenetic processes as highlighted in this review. By manipulating micropattern shapes, cells were shown to precisely adapt their cytoskeleton architecture to the geometry of their microenvironment. Remodelling of actin and microtubule networks participates in the adaptation of the entire cell polarity with respect to external constraints. These modifications further impact cell migration, growth and differentiation.