Two-Photon polymerization for microfabrication of three-dimensional scaffolds for tissue engineering application

In natural tissues cells are embedded in a three-dimensional fibrous network of biopolymers like collagen, hyaluronic acid etc. This extracellular matrix (ECM) influences the cell fate, the differentiation status, metabolic processes and provides structural integrity. For a three-dimensional or physiological cell cultivation that are required in biomedical applications (e.g. tissue engineering, BioMEMS) scaffolds are needed. These scaffolds mimic the ECM according to their biocompatibility which comprises aspects of surface compatibility and importantly for tissue engineering applications aspects of structural compatibility. We have evaluated scaffold design parameters for the three-dimensional cultivation of chondrocytes for the tissue engineering of artificial cartilage. Two-photon polymerization is a powerful technique for fabrication of polymeric three-dimensional micro- and submicro-structures. The photoinitiation system for two-photon polymerization is excited by simultaneous absorption of two photons leading to chemical polymerization reactions. Due to a tight confinement of the excitation Volume around the focal point, this method can produce micrometer sized objects maintaining a high spatial resolution down to 100 nm. Two-photon processes require very high photon densities which are provided by pulsed femtosecond lasers. The potential of this approach for microfabrication of scaffolds for tissue engineering is demonstrated by investigation of the cell response to microstructures with complex three-dimensional geometry and feature sizes in the range of few micrometers.