WEB Polycaprolactone fiber reinforced hydrogels - a new platform technology in biofabrication
Biofabrication for tissue regeneration often applies 3D-bioprinting to spatially organize materials and cells in a biomimetic manner. On the one hand high printing resolutions are required to produce well-organized constructs, which should display sufficient mechanical stability that meets the requirements of native tissue. On the other hand, high cell viability is a crucial prerequisite for the subsequent formation of functional tissue during the maturation process. This work applies fiber-reinforced hydrogels as a composite system to overcome previous limitations resulting from the use of highly concentrated hydrogels to improve printing quality, which, as a result of increased shear forces, tends to go on the expense of cell viability.
Here, a procedure based on electrospinning was developed to generate short poly-ε-caprolactone (PCL) fibers with a controllable aspect ratio. These fragments could be homogenously dispersed in established hydrogel systems and rheological studies were performed to evaluate the impact of fiber concentration and length distribution in the gel matrix. It was demonstrated that fragmented fibers in the size of nano- to micrometers could be printed within hydrogels without increased risk of clogging. Simultaneously, shear-induced alignment of these novel filler materials upon printing significantly increased the overall mechanical stability of the composite system, allowing the reduction of hydrogel concentrations. It is expected, that reduced shear forces, increased hydrogel porosity and thus nutrient diffusion as well as fibrous structures can significantly contribute not only to cell viability, but also mechanically and structurally promote the subsequent maturing process. To quantify rheological effects and systematically describe the resulting material characteristics, viscoelastic models were applied to fit the measured data and work towards advanced material understanding allowing predictability in the design of new bioinks with this transferable composite system.
Our work includes the production of short PCL fibers and SEM analysis thereof, surface modification of PCL fillers by plasma treatment and oscillatory rheology to determine the effects of size, concentration and surface modification on the mechanical properties of the resulting composite hydrogels.