Nanoparticle-based enzymatic sensors – accessing enhanced activity

J.C. Breger, M.G. Ancona, S.A. Walper, C.W. Brown III, E. Oh, K. Susumu, J.N. Vranish, I.L. Medintz
U.S. Naval Research Laboratory,
United States

Keywords: nanoparticle, enzyme, biosensing, catalysis, substrate, pesticide


Due to their innate and exquisite specificity, enzymes are of significant interest for various biosensing based applications. We, and many other research groups, have demonstrated that immobilization of enzymes on nanoparticles (NPs) often results in enhanced enzymatic activity relative to the enzyme when freely diffusing in solution.1,2 A full understanding of the mechanisms that underpin this phenomenon could provide a predictive capacity and allow for the design of a new generation of nanoscale sensing material with enhanced activity, however, this is still critically lacking. To address this deficiency we have been assembling different NP-enzyme constructs and analyzing their activity in-depth. We exploit previously developed NP-bioconjugation chemistries to allow us assemble the NP-enzyme conjugates in a carefully controlled and ordered manner to create homogeneous systems with parametric access. Several different NP-enzyme systems have been studied to date including those assembled with alkaline phosphatase,3 beta-galactosidase,4 glucose oxidase and several recombinant variants of phosphotriesterase5,6 which is capable of hydrolyzing organophosphate compounds including paraoxon and several other related pesticides. Along with different assay formats, in-depth kinetic analysis is often applied to help elucidate the underlying processes. A detailed description of the phosphotriesterase system will be provided as it is one of the more revealing and has provided the most insight, see Figure 1. Some discussion will be provided on how such systems can contribute to improved biosensing and other diverse biocatalytic-based applications.7,8