Bio Roll-Up: Self-Assembly of Hydrogel Photoresists

This paper describes the development of a technology called “Bio Roll-Up” which utilizes two-layer stacks of rectangular hydrogel photoresists to create a self-assembled tubular structure in physiologically relevant, pH 7 buffer. These rectangles are approximately 2 × 3 mm with a top layer with higher crosslinking and a bottom layer with lower crosslinking. Upon submersion in buffer, differential swelling stresses act to initiate self-assembly. Multiple stages of advancement in this technology are described that explore variation in composition of hydrogels and self-assembly media. In addition, several approaches are presented for controlling the timing of self-assembly. While the earliest example of self-assembly occurred in pH 4 HCl, we have shown that through optimization of the polymer structure, self-assembly now occurs in phosphate-buffered saline (PBS) that has a neutral pH and is isotonic and compatible with mammalian cells.