Studies on PVP hydrogel-supported luminol chemiluminescence: 1. Kinetic and mechanistic aspects using multivariate factorial analysis

Efficient chemiluminescence of luminol in the presence of hemin without added hydrogen peroxide†

The results reported herein demonstrate for the first time that typical reducing agents in an alkaline medium initiate chemiluminescence of luminol in the presence of hemin, and the efficiency of their action is comparable to that of hydrogen peroxide and exceeds it in the case of the superoxide anion. The pertinent implications of these findings refer to new possibilities for developing chemiluminescence assays and biosensors and to precautions for determining hydrogen peroxide using luminol and hemin in samples of unknown composition, most prominently, of biological origin.

Antiradical capacity assay for hydrophobic substances using hemin-catalyzed luminol chemiluminescence in cationic micelles

Antioxidant substances which can diminish the steady-state concentration of free radicals in vivo are important in the human dietary to diminish the deleterious effects of oxidative stress. As the potential of certain substances as antioxidants is difficult to be verified in vivo, simple chemical in vitro assays which test the potential of substances as antioxidants are of great importance for the screening of new antioxidants. These assays measure the capacity of a substance to suppress free radicals. We describe here an antiradical capacity assay, based on luminol chemiluminescence, in cationic micellar medium, allowing the capacity determination of hydrophobic compounds. The antiradical capacity of antioxidants is determined using the Trolox standard by the measurement of the light emission inhibition area caused by the addition of different antiradical concentrations. The obtained results are compared to the values determined using the scavenging of stable free radicals be the substances and shown to be similar for compounds like uric acid, rutin, and quercetin. However, for vitamin E, the luminol assay results in a considerably higher antiradical capacity than the assay with a stable free radical, which is rationalized by the higher reactivity of the radical generated in the luminol assay and a specific localization of vitamin E in the micellar medium.

Enhanced Efficiency of an Enzyme Cascade on DNA-Activated Silica Surfaces

In nature, compartmentalized and spatially organized enzyme cascades are utilized to increase the efficiency of enzymatic reactions. From a technologically relevant perspective, synthetic enzyme systems have to be optimized with emphasis on enzyme activity, productivity, scalability, and ease of use. But the underlying principles and relevant parameters that lead to an enhancement of the activity of enzyme cascades through spatial organization are still under debate. Here, we report on the 10-fold activity enhancement of the GOx-HRP enzyme cascade for the oxidation of luminol, when the enzymes are colocalized on micron-scaled solid scaffolds. Both enzymes were initially assembled and concentrated on DNA origami rectangles and finally further concentrated on the surface of silica particles. We show that each particular component of the designed system contributes to the activity enhancement. Furthermore, we measured an influence of the silica particle length scale on the total productivity by a factor of 5-10, but to a lesser extent on the maximum enzyme activity. Our findings demonstrate that micrometer-sized scaffolds can be used to enhance the efficiency of enzyme-cascades by at least a magnitude and that solid-phase scaffolds enable scalability for technological applications.