Biofilm colonization on biomedically-relevant surfaces is one of the major causes leading to reinfection, including in dental restorations. Every time a dental filling is replaced, more tooth structure is lost, complicating prognosis and increasing the chance for more serious systemic infections. The existing antifouling and/or antimicrobial materials are efficient in either preventing attachment or killing the bacteria, but much more effective protection could be achieved if both properties were combined. Thus, our goal was to take advantage of natural pH variations in the oral cavity to design a reversible molecule (carboxy betaine - CB), alternatingly existing in two chemical states: an antibacterial quaternary ammonium cation (through acid-catalyzed ring closure, CB-Ring), and an antifouling linear zwitterion, CB-OH.