Surface wrinkling of materials offers a simple yet elegant approach to fabricating cell culture substrates with highly ordered topographies for investigating cell mechanobiology. In this study we present a tunable shape memory polymer (SMP) bilayer system that is programmed to form, under cell compatible conditions, wrinkles with feature sizes on the micron and sub-micron length scale. We found that with increasing deformation fixed into the SMP substrate, wrinkled topographies with increasing amplitudes, decreasing wavelengths, and increasing degree of wrinkle orientation were achieved.Analysis of the cellular response to previously wrinkled (static) substrates revealed that cell nuclear alignment increased as SMP deformation increased. Analysis of the cellular response to an actively wrinkling substrate demonstrated that cell alignment can be controlled by triggering wrinkle formation. These findings demonstrate that the amount of deformation fixed (and later recovered) in an SMP bilayer system can be used to control the resulting wrinkle characteristics and cell mechanobiological response. The tailored and dynamic substrate functionality provided by this approach is expected to enable new investigation and understanding of cell mechanobiology.

Surface topography of medical implants provides an important biophysical cue on guiding cellular functions at the cell-implant interface. However, few techniques are available to produce polymeric coatings with controlled microtopographies onto surgical implants, especially onto implant devices of small dimension and with complex structures such as drug-eluting stents. Therefore, the main objective of this study was to develop a new strategy to fabricate polymeric coatings using an electrospraying technique based on the uniqueness of this technique in that it can be used to produce a mist of charged droplets with a precise control of their shape and dimension. We hypothesized that this technique would allow facile manipulation of coating morphology by controlling the shape and dimension of electrosprayed droplets. More specifically, we employed the electrospraying technique to coat a layer of biodegradable polyurethane with tailored microtopographies onto commercial coronary stents. The topography of such stent coatings was modulated by controlling the ratio of round to stretched droplets or the ratio of round to crumped droplets under high electric field before deposition. The shape of electrosprayed droplets was governed by the stability of these charged droplets right after ejection or during their flight in the air. Using the electrospraying technique, we achieved conformal polymeric coatings with tailored microtopographies onto conductive surgical implants. The approach offers potential for controlling the surface topography of surgical implant devices to modulate their integration with surrounding tissues.

Hydrogels have found wide application in tissue engineering and cell mechanobiology research due to their tunable, and often biomimetic, biochemical and biomechanical properties. Although it has been known for more than a decade that hydrogels can be designed to exhibit shape memory functionality—the ability to change from one defined shape to another when triggered by a defined stimulus—shape memory hydrogels have not previously been exploited in tissue engineering or mechanobiology research. Here we report the development of a biodegradable and biocompatible hydrogel with tailored shape memory as well as desirable mechanical property for soft‐tissue applications. A shape memory hydrogel was synthesized by photopolymerization of PCL3k diacry‐lates together with acrylate‐PEG2k‐GRGDS in the presence of a crosslinker, tetrathiol, and photoinitiator, DMPA, through thiol‐ene chemistry. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were carried out to examine the thermal, mechanical and shape memory properties of the hydrogel in dry and wet states. Cell culture studies were performed to characterize material cytocompatibility. We found that the PCL phase was crystalline in the hydrogel, providing an excellent, reproducible shape memory effect. The transition temperature (shape memory “trigger”) was tuned to fall between room and body temperature. Both cell attachment and proliferation studies revealed that the presentation of GRGDS molecules in the hydrogel facilitated fibroblasts adhesion and spreading on the hydrogel surface. This hydrogel, tailored to exhibit shape memory behavior in the cell culture compatible temperature range, should provide new opportunities for “smart” shape‐changing scaffolds and substrates for application in tissue engineering and investigation of cell mechanobiology.

Ordered wrinkles have been used for a variety of applications and have found much interest in the field of mechanobiology, as topography has been shown to influence cell behavior. In this study we aimed to synthesize a biocompatible material that could be triggered to form wrinkles under physiological conditions. To achieve this aim, we used a shape memory polymer (SMP) substrate to induce surface buckling of a thin gold film resting atop the SMP. The SMP composition was tuned to allow for surface buckling to occur under cell culture compatible conditions. The SMP was strained to different values prior to buckling and the resulting wavelength and amplitude for each strain was characterized. Increasing the strain allowed for smaller wavelengths and larger wrinkle amplitudes. Preliminary cell culture experiments showed high cell viability and cell alignment atop the wrinkled topography.

No abstract