(497f) Quantitative Analysis of Cell Adhesion Studies On Grafted Pnipaam Thermoresponsive Surfaces Synthesized Using ATRP

Environmentally
responsive (or ?smart?) polymers represent a new approach for controlling biofouling
release. Poly (N-isopropyl acrylamide) (PNIPAAm) is a thermoresponsive polymer
and acts as a biofouling resistant coating when grafted on to surfaces, as it
exhibits a change in its relative hydrophobicity above and below its lower
critical solution temperature (LCST ~ 32⁰C). We report grafted
PNIPAAm brushes, synthesized using a relatively simple high throughput method
which allows atom transfer radical polymerization (ATRP) in presence of air.
The grafted surfaces have been characterized using FTIR, XPS, ToF-SIMS, ellipsometry
and contact angle measurements. We also quantitatively studied, the adhesion of
marine bacteria on these surfaces, both above and below the LCST using a
spinning disc apparatus which device applies a linear range of shear forces to
cells attached at the interface of a single sample. We have previously
demonstrated that our test bacterium, Cobetia marina attaches more
readily to PNIPAAm above the LCST (i.e. when the surface is relatively hydrophobic)
and is released upon transition to temperatures below the LCST. In this work, C.
marina was attached to PNIPAAm grafted surfaces at 37⁰C and
subjected to varied detachment forces at 37⁰C, 22⁰C and 4⁰C
in artificial sea water. The number of adherent cells decreased non-linearly with
applied force and as expected the cell detachment at the interface required
lesser shear force at lower temperatures evaluated. The ability to directly
correlate a measurable force to bacterial attachment and release represents a
step forward in understanding of interactions between PNIPAAm and bacterial
cells. These experiments demonstrate the potential of PNIPAAm and similar polymers
as possible fouling-release agents, and suggest that grafted PNIPAAm (or
similar polymers) may be useful as regenerable fouling-release surfaces.