Join the ChBE Department for a lecture by University of Illinois – Urbana and Reid T. Milner Professor Deborah Leckband on Wednesday, February 20 at 3:15 pm in the Perlstein Hall Auditorium. Refreshments will be served.

“Design Rules for Thermally Tunable Adhesive Coatings for Tissue Engineering”
Environmentally responsive polymer coatings are extensively used in biotechnology in a applications ranging from self-cleaning surfaces to tissue engineering. Several high profile examples demonstrate the utility of thermally reversible coatings for tissue engineering. Poly(N-isopropyl acrylamide) (PNIPAM) is often used, because it undergoes a solubility transition (LCST) near 32°C, which is close to physiological temperature. However, the inability to consistently achieve efficient, thermally reversible cell adhesion/release from PNIPAM films hinders their widespread use. This variability stems from a lack of knowledge of the mechanisms controlling reversible cell adhesion and the underlying polymer characteristics. A common assumption is that, above the LCST, PNIPAM brushes collapse to form a “sticky” film that adsorbs proteins and cells. Upon reducing the temperature, chain re-swelling is assumed to desorb adhering cells and proteins. Here I describe investigations of protein and cell interactions with PNIPAM brushes. Our data challenge this commonly assumed model and support an alternative, in which protein insertion into the polymer brush is key to efficient cell adhesion and rapid release. We further show that the chain collapse behavior differs from a widely assumed model, and depends on the chain molecular weight and grafting density. These findings suggest an alternative mechanism of thermally reversible bioadhesion on PNIPAM, and identify polymer parameters for tuning the behavior.