Attachment and detachment of bacteria on surfaces with tunable and switchable wettability.

Controlling accumulations of unwanted biofilms requires an understanding of the mechanisms that organisms use to interact with submerged substrata. While the substratum properties influencing biofilm formation are well studied, those that may lead to cellular or biofilm detachment are not. Surface-grafted stimuli-responsive polymers, such as poly (N-isopropylacrylamide) (PNIPAAm) release attached cells upon induction of environmentally-triggered phase changes. Altering the physicochemical characteristics of such polymeric systems for systematically studying release, however, can alter the phase transition. The physico-chemical changes of thin films of PNIPAAm grafted from initiator-modified self-assembled monolayers (SAMs) of omega-substituted alkanethiolates on gold can be altered by changing the composition of the underlying SAM, without affecting the overlying polymer. This work demonstrates that the ability to tune such changes in substratum physico-chemistry allows systematic study of attachment and release of bacteria over a large range of water contact angles. Such surfaces show great promise for studying a variety of interactions at the biointerface. Understanding of the source of this tunability will require further studies into the heterogeneity of such films and further investigation of interactions beyond those of water wettability.