Abstract
Hydrogen peroxide (H(2)O(2)) quantification in biomedicine is valuable as inflammation biomarker but also in assays employing enzymes that generate or consume H(2)O(2) linked to a specific biomarker. Optical H(2)O(2) detection is typically performed through peroxidase-coupled reactions utilizing organic dyes that suffer, however, from poor stability/reproducibility and also cannot be employed in situ in dynamic complex cell cultures to monitor H(2)O(2) levels in real-time. Here, we utilize enzyme-mimetic CeO(2) nanocrystals that are sensitive to H(2)O(2) and study the effect of H(2)O(2) presence on their electronic and luminescent properties. We produce and dope with Eu(3+) these particles in a single-step by flame synthesis and directly deposit them on Si and glass substrates to fabricate nanoparticle layers to monitor in real-time and in situ the H(2)O(2) concentrations generated by Streptococcus pneumoniae clinical isolates. Furthermore, the small CeO(2):Eu(3+) nanocrystals are combined in a single-step with larger, non-responsive Y(2)O(3):Tb(3+) nanoparticles during their double-nozzle flame synthesis to engineer hybrid luminescent nanoaggregates as ratiometric robust biosensors. We demonstrate the functionality of these biosensors by monitoring their response in the presence of a broad range of H(2)O(2) concentrations in vitro from S. pneumoniae, highlighting their potential for facile real-time H(2)O(2) detection in vitro in cell cultures.