Nanoencapsulation of Luminol-Hematin-H2O2 Chemiluminescence in Calcium Phosphate Nanoshells

Oxidants are substances with the ability to oxidize (remove electrons from) other substances. Oxidants are usually chemical substances with elements at high oxidation number (e.g., H2O2) or highly electronegative atoms that can gain one or two extra electrons by oxidizing a substance (e.g. O, F, and Cl). Detecting oxidants is important because oxidants have been implicated in the pathogenesis of many major diseases such as heart disease, Alzheimer's, immune deficiency, etc. Their detection is also helpful because these species play important regulatory roles as signaling units and in the everyday function of tissues and cells. The specific objectives of this research were to develop and characterize a chemiluminescence reaction system encapsulated in an aqueous-cored, calcium phosphate based nanoshell to detect oxidants. Chemiluminescence, the emission of light as a result of a chemical reaction, has been used for decades to detect oxidative chemical processes involving trace metals and organic contaminants with high sensitivity, wide linear range and simple instrumentation. Great sensitivity also means that most of these reactions require carefully controlled conditions in solution. Nanoencapsulation can expand the usefulness of chemiluminescence detection of oxidants because it 1) makes them as sensitive or more sensitive to oxidants than the corresponding system in dilute solution, 2) is not affected by other molecules outside the capsule, and 3) has reasonable reaction kinetics (of the order of several minutes or less and reproducible). Nanoencapsulation can create a protective environment for chemical events, allowing quantitative analysis and detection of a system irrespective of the presence of interfering substances. This technology would also be useful in a wide variety of applications such as biosensors and online sensing, drug delivery, and medical diagnostics. The scientific and engineering challenges in this area involve synthesis as well as understanding the basic chemical processes inside nanocapsules. Luminol-hematin-H2O2 chemiluminescence was chosen for nanoshell encapsulation because 1) mechanisms for luminol chemiluminescence are well known, and 2) oxidation by H2O2 in aqueous alkaline solution leads to strong chemiluminescence when catalyzed by hematin, a biofriendly catalyst (CHAPTER 2). The effects of viscous additives and fluorophore sensitizers on luminol reactions in solution and inside nanoshells will be examined in CHAPTER 3. The basic aspects of chemiluminescent nanoshell material synthesis will be characterized in CHAPTER 4 and its performance with and without additives evaluated in CHAPTER 5.