Biomaterials for MEMS

58 R. Tran et al.

to cells deeply embedded in the substrate has proven to be a formidable task.

100

The development of an established vasculature system to provide oxygen, nutri-

ents, and waste removal is critical in the survival of tissue engineered organs.

107

From this limitation, current engineered tissue is limited to 150–200 micron thick-

nesses due to oxygen diffusion limitations.

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Fidkowski et al. have used BioMEMS to build capillary networks onto syn-

thetic substrates. Using standard soft photolithography techniques, the research

group patterned intricate capillary networks 10 microns in size onto PGS using

silicon wafers as molds. Human umbilical vein endothelial cells (HUVECs) were

seeded onto the PGS substrates and perfused under flow conditions to create

confluent endothelialized two–dimensional cell layers. The HUVECs could be

lifted from the PGS substrate and incorporated into other devices. Thus, this study

showed the potential for using PGS in combination with BioMEMS techniques to

create microvasculature in vitro towards the fabrication of vascularized organs.

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3.6 OUTLOOK

Many of the tissues in the body are soft and elastic. Much attention has been paid

in using biodegradable soft and elastic scaffolds for tissue engineering soft tissues

such as skin, blood vessel, tendon, ligament, cartilage, bladder etc. The roles of

biodegradable elastomeric materials in tissue engineering have been increasingly

emphasized as the evolving progress in understanding the cell/materials/host

interactions. Soft and elastic scaffolds made of biodegradable elastomeric scaffolds

not only provide a substrate for cells to adhere and proliferation, but also minimize

the compliance mismatch with surround tissues and provide cues and signals to

promote tissue development and functional integration with the host.

The design and synthesis of biodegradable elastomers will continuously

evolve owing to the more stringent material requirements in personalized tissue

regeneration. Despite the recognized importance of the mechanical properties of

tissue engineering scaffolds on the tissue development, there has been a dearth

on fundamental understanding on how the soft and elastic scaffolds affect the

inflammatory response of the host and the tissue/graft integration.

The application of BioMEMS in tissue engineering has resulted in more un-

derstanding on how cells respond to micro/nano structure created by BioMEMS.

Constructing vasculature with the aid of BioMEMS on biodegradable elastomeric

scaffolds for tissue engineering is still in its infancy. The current studies lie on fab-

ricating channels on two-dimensional films, and then stacking them into 3D chan-

nels on elastomers, mostly on PDMS. More studies should be focused on using

biodegradable elastomeric substrates. More importantly, the vasculature should

be built up within 3D porous scaffolds instead of just in between two-dimensional

solid films. Our recent studies have resulted in 3D scaffolds with vasculature-like

channels built using our recently developed CUPE polymers via the scaffold-sheet

tissue engineering strategy combined with BioMEMS technology.

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