Selective potentiometric detection of reactive oxygen species (ROS) in biologically relevant concentrations by a modified metalized polyporphyrine sensing layer coated with nonbiofouling poly(2-alkyl-2oxazoline)s

We built a robust selective potentiometric sensor of reactive oxygen species (ROS) as a thin layer applied on the surface of smart implants, which enables the detection and localization of inflammation at an early stage. The sensor consists of a conductive polymer layer based on polythiophene with an incorporated porphyrin-metal complex that potentiometrically detects the presence of ROS. This sensor is covalently coated with a nonbiofouling layer of poly(2-methyl-2-oxazoline), which works as a biocompatibilizer but mainly prevents the sorption of proteins and other biomacromolecules naturally occurring in organisms, which could interfere with the ROS signal. We have shown that our potentiometric sensor shows a rapid response to hydrogen peroxide, does not experience interference with bovine serum albumin as a model serum protein when sensing ROS, is able to fully reversibly detect ROS with a linear response within a very wide range of biologically relevant concentrations and, most importantly, is able to distinguish between hydrogen peroxide and hypochlorite. We also performed a head-to-head comparison of two positional isomers of thienylated porphyrine for sensor applications (2TTP and 3TTP, with 3TTP shown to be more appropriate) and four different coordinated metals (Cu, Fe, Co and Mn, with Cu and especially Fe shown to be the most appropriate).