Enabling precise spatial and temporal control of human tissue morphology and microenvironments within engineered cell culture systems

Author / Creator

McNulty, Jason D., dissertant

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Online

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Summary

Increased understanding of human developmental biology gives researchers more opportunities for experimentally modeling diseases and testing new regenerative therapies. Depending on the application...

Increased understanding of human developmental biology gives researchers more opportunities for experimentally modeling diseases and testing new regenerative therapies. Depending on the application, disease models can often be simplified into two dimensional arrays using processes such as microcontact printing ([mu]CP). While a promising technique for producing spatially organized microenvironments, the lack of standardized, precision equipment for performing the deposition results in frequently oversimplified substrates with limited complexity or biological relevance. The first aim of the research presented in this thesis is to develop an automated system which allows for free-form, high-precision, and uniform [mu]CP onto a variety of substrates with sequential deposition capabilities. This robotic microcontact printing (R-[mu]CP) technology will enable researchers to overcome major challenges with tissue engineering by providing chemically defined and scalable means to precisely engineer tissue morphology and microenvironments over multiple length scales in a spatial and temporal manner. As the results show, the prototype system not only possesses the ability to align multiple polydimethylsiloxane (PDMS) stampings, but it has the capability to do so even after the substrates have been removed, and replaced back onto the system with <10 [mu]m precision and accuracy In many cases, two dimensional disease models are not sufficient for gaining complete understanding of microscale biological interactions. Therefore, researchers have attempted to produce three dimensional tissue scaffolds for addressing these limitations. The second aim of this research is to develop processes for the fabrication of highly-complex engineered hydrogel scaffolds with internal and external microscale architecture using sacrificial synthetic thermoplastic polymers, with high-throughput and scalable manufacturing techniques such as micro-injection molding. With this technique, exemplary biocompatible scaffolds were produced with poly(vinyl alcohol)-calcium salt templates (PVOH-Ca) and fabricated by micro-injection molding, to cast internal geometries within both bulk and ionically curing hydrogels. Computed tomography (CT) analysis demonstrated that this process enabled casting of microscale features with 6.4 ± 7.2% average error. Additionally, by assembling multiple modular PVOH-Ca templates, full 3D channel networks with multiple length scales were produced within alginate hydrogels to demonstrate the flexibility of the technology. Thus, micro-injection molding of sacrificial PVOH-Ca templates should be capable of implementation in diverse tissue engineering applications.

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