A class of gels whose composition and mechanics can be externally regulated using a living, visible light photoredox catalyzed polymerization reaction can be used for 3D printing, tissue adhesion, scaffolding, and engineering, as well as for cell culture.
To date, the only reports of living light-induced growth in polymer gels have required the use of ultraviolet (UV) light to induce changes in gel microstructure via polymerization. However, because the gel networks can absorb a high amount of UV light, it is difficult for UV to penetrate inner layers of the gel. In addition, side reactions in the course of polymerization can lead to undesirable products within the gel microstructure, and loss of living behavior. In addition, UV light may harm biological systems embedded within or growing on the gel. A method that uses visible-light could overcome all of these deficiencies.
This invention involves an organic photocatalyst, 10-phenylphenothiazine (PTH), which can catalyze vinyl polymerization reactions from monomers already embedded within a gel matrix. Only a small amount of photocatalyst is needed, and a simple household compact fluorescent light bulb or blue LED is sufficient to trigger these reactions. The polymerization has been shown to proceed with excellent control to produce polymers with low dispersity indices. Different monomers and crosslinkers can be embedded into the parent gel at different ratios, influencing the average chain length resulting from polymerization. This in turn effects the material mechanics and composition only in irradiated areas. The process can be repeated many time in patterned regions to produce complex objects. This reaction can give gels the ability to photo-heal and photo-weld, and can also increase or decrease their shear strength and ability to swell or deswell upon aqueous immersion. In addition to these qualities, tuning the reaction creates daughter gels with a variety of mechanical properties and chemical compositions, hydrophilicity, and temperature responsiveness.
Enables the preparation
of diversified daughter gels with tunable mechanical properties and various
chemical compositions from a parent gel
Use of a fluorescent or
LED light source instead of UV to catalyze reaction
New platform to design
and synthesize polymer networks with photo-healing, photo-welding, or
site-specific responsiveness properties
polymerization reaction with low dispersity and excellent control