Detection of Oxidative Stress Biomarkers Using Novel Nanostructured Biosensors

Abstract

The oxidative stress is associated with the diminished capacity of a biological system to counteract an overproduction or invasion of reactive oxygen species and other radicals. Since oxidative stress is the leading cause of DNA damage, genetic disorders, cancer, and many environmental pollution related diseases, there is an urging need for oxidative stress screening and its prevention. There is growing evidence that oxidative stress may cause autism in children. The oxidative stress has also been implicated in the development of diabetes. Several biomarkers of oxidative stress have been identified, including glutathione (GSH), 3-nitrotyrosine (NT), homocysteine (Hcys), and cysteine (Cys). The tripeptide glutathione and its oxidized form, glutathione disulphide (GSSG), form a redox potential maintenance system in all eukaryotic cells. Since glutathione efficiently protects the DNA, proteins and lipid membranes from radical attacks, its diminished level is signaling an oxidative stress and the increased vulnerability of a biological entity to the environmental influences. An increased level of 3-nitrotyrosine, which is formed under oxidative stress in the presence of nitric oxide, has been found in diabetic patients. Homocysteine is a biomarker and an active agent leading to cardiovascular deterioration. While these biomarkers can be accurately determined using advanced instrumental assays, a wide screening would require the development of small, inexpensive, rapid, and simple in operation platforms for biomarker analysis. In this Chapter, the detection methods for the oxidative stress biomarkers based on their interactions with monolayer-protected gold nanoparticles (AuNP) are described. The nanoparticle utilization in a solution-phase analysis as well as in a multifunctional sensory film preparation is presented. The interactions of AuNP with glutathione and homocysteine have been investigated using resonance elastic light scattering (RELS) and plasmonic UV-Vis spectroscopy. The high sensitivity of the RELS measurements enables monitoring of ligand exchanges and the biomarker-induced AuNP assembly. The viability of designing simple and rapid assays for the detection of glutathione and homocysteine is discussed. The surface plasmon band broadening and bathochromic shift are consistent with the biomarker-induced AuNP assembly and corroborate the RELS measurements and HR-TEM imaging. The results of molecular dynamics and quantum mechanical calculations support the mechanism of the formation of GSHand Hcys-linkages in the interparticle interactions and show that multiple H-bonding can occur. In contrast to homocysteine and glutathione that induce gold nanoparticle assembly in specific pH ranges, no aggregation of nanoparticles has been