Event Abstract Back to Event Nano-contact printing on ultra-soft substrates to investigate the impact of substrate stiffness on haptotaxis Donald Macnearney1, Bernard Mak2 and David Juncker1 1 McGill University, Biomedical Engineering, Canada 2 McGill university, Mechanical Engineering, Canada Introduction: Cell navigation, migration, and motility are vital requirements for life, whether it be during the developmental stages of an organism, or throughout the life cycle - for example during tissue maintenance and wound healing. This process is regulated by complex and continuous integration of extracellular cues. For example, surface bound chemical gradients are integral in guiding extending axons during development - a process known as haptotaxis - yet it is also known that the mechanical stiffness of an in vitro substrate can impact the rate of neurite extension[1]. This interplay between chemical and mechanical cues is also evident in other cell types, such as fibroblasts[2]. Here, we present a technique to investigate cell migration via surface bound gradients patterned on ultra-soft substrates. We propose this method as a way to further our knowledge of the interplay between chemical and mechanical cues during haptotatic cellular migration and guidance. Materials and Methods: This work presents a new technique for applying our previously shown technique of nano-contact printing[3] to an ultra-soft substrate. The soft substrate used is Sylgard 527, a form of polydimethylsiloxane (PDMS). This material was selected because its modulus - around 1 kPa - is similar to that of brain tissue. The gradients patterned are digital nano-dot gradients of various known guidance proteins, consisting of tens of thousands of 200 nm squares with varying pitch to create a repeatable and measurable concentration gradient of surface bound cues. We use both C2C12 myoblast cultures and primary cortical rat neurons to investigate the validity of our technique. A reference surface of 75% polyethylene glycol and 25% poly-D-lysine was used to optimize cellular responses[4]. Results: Our printing technique was able to generate gradients of surface bound cues accurately and repeatably, albeit with some slight skewing of the pattern due to the softness of the substrate (Figure 1a). We are currently using this technique to investigate the migration of C2C12 myoblasts on patterned gradients of Netrin-1 (not shown), building on our previous work[3], as well as to study axon turning when presented with Netrin-1 gradients on soft substrates (Figure 1b). Discussion: The technique for patterning digital nano-gradients of guidance proteins on soft substrates has been demonstrated, and preliminary results suggest that there is a difference in the cellular responses on soft substrates vs. on hard substrates (i.e. glass). C2C12 myoblasts adopt a distinctly rounded phenotype on the soft substrate, and motility and adhesion both appear to be different on the soft substrate as well, corroborating what has previously been found[5]. Conclusion: We developed a novel printing technique which allowed us to adapt our previously shown digital nano-gradient patterns to ultra-soft substrates. This allows us to approach the question of celluar guidance in the context of different mechanical environments. We are currently using this technique to investigate migration of C2C12 myoblasts and axon turning of primary rat neurons on ultra-soft substrates. NSERC; Integrated Sensor Systems, NSERC-CREATE, McGill University; Neuroengineering Program, NSERC-CREATE, McGill University