Engineering cell culture environments that mimic both the 3D structure and the dynamic nature of tissues is a major challenge in tissue engineering. Self-folding materials allow the generation of cell-friendly structures with 3D complexity across a range of length scales that are difficult to achieve with printing and lithography. Folding is induced by differential stresses generated within a flexible or elastic material. Polymeric materials, and hydrogels in particular, are well-suited for self-folding applications because they undergo pronounced volume and modulus changes in response to cell-friendly stimuli such as water, pH or temperature, to generate differential stresses within. While self-folding hydrogels have been reported, heterogeneities that lead to differential swelling must be pre-patterned into the material, and thus the shape change occurs as soon as the material is placed in a physiologically relevant environment (lacks temporal control). Furthermore, only a few examples utilizing these materials with live cells have been reported. We have designed photodegradable hydrogels incorporating <i>ortho</i>-nitrobenzyl moieties that permit encapsulation or cell seeding on swollen planar films. Thin sheets are programmed to undergo a 2D to 3D shape change in response to light which induces irreversible folding of the hydrogel sheet due to differential swelling of the degraded and non-degraded regions. This bottom-up approach enables the use of simple 2D precursors to create biologically relevant 3D structures such as tubes and folded containers for cell encapsulation. Unlike other shape-changing polymer systems, the <i>o</i>-NB hydrogel system requires no laminated bilayers, pH change or elevated temperatures to induce shape-change. Furthermore, photodegradation based shape-change enables external temporal control of folding that can be induced at time points of choice during cell culture.

Shape-changing photodegradable hydrogels as dynamic 3D cell culture environments

254th National Meeting (2017)

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