Antimicrobial polysiloxane polymers and coatings containing pendant levofloxacin

A broad-spectrum antimicrobial drug, levofloxacin, was successfully incorporated into a siloxane coating by covalent attachment. First, an epoxy-functional poly(dimethylsiloxane) (Ep-PDMS) was synthesized by platinum-catalyzed hydrosilylation using poly(methylhydro-co-dimethyl)siloxane and allyl glycidyl ether. Next, levofloxacin was reacted with Ep-PDMS using a stoichiometric excess of epoxy groups relative to levofloxacin to produce a siloxane copolymer containing both pendant levofloxacin and epoxy moieties (levo-Ep-PDMS). Since attachment (i.e. tethering) of levofloxacin occurred via ring-opening of epoxy groups by the carboxylic acid group of levofloxacin, the tether produced was an ester-functional tether. Crosslinked surface coatings were produced by solution blending the polymer with diethylenetriamine as a crosslinker. Compared to a control coating produced by simply blending levofloxacin into a polysiloxane, the coating containing tethered levofloxacin moieties displayed a uniform distribution of levofloxacin, higher initial kill, and sustained antimicrobial surface activity.