Document Type

Dissertation - Open Access

Award Date

2023

Degree Name

Doctor of Philosophy (PhD)

Department / School

Chemistry and Biochemistry

First Advisor

Brian A. Logue

Keywords

Chlorine exposure, Chloro-tyrosine adduct, Fluorescent probe, Method development and validation, Pharmacokinetic study, Toxic inhaled substance

Abstract

Toxic inhalation agents (TIAs) (i.e., chlorine (Cl2), cyanide (HCN), etc.) are highly poisonous. However, they have a variety of industrial uses, such as health, agro-food, building, textiles, transport, leisure activities, cosmetics, etc. In addition, TIAs can be used as chemical agents in terrorist events or conventional warfare. The ability to detect TIAs in biological and environmental samples is important for preparing use, determining individual exposure, limiting hazardous exposure, etc. Therefore, developing simple and sensitive analytical methods for TIAs, TIA metabolites, and antidotes for those toxic agents is very important. The focus of this study was chlorine and cyanide. Chlorine is a poisonous and corrosive industrial chemical that causes irritation and damages the respiratory tract, eyes, and skin. Chlorine is known to form a stable adduct with tyrosine-protein adducts (e.g., 3-chlorotyrosine (Cl-Tyr) and 3,5-dichloro tyrosine (Cl2-Tyr)). These adducts are used as biomarkers to confirm chlorine exposure. However, those methods required time-consuming and tedious sample preparation. Therefore, we developed a novel base hydrolysis technique for chloro-tyrosine protein adducts to produce 2,6-dichlorophenol (2,6-DCP). The 2,6-DCP was extracted from the hydrolysate and analyzed via UHPLC-MS/MS analysis of this marker. The method produced excellent sensitivity for 2,6-DCP with the detection limit of 7.8 g/kg (corresponding to 7.2 nM in the final solution) and calibration curve linearity extending from 0.054 - 54 mg/kg (R2 0.9997 and overall %RA 94). The accuracy and precision (100 14%, and 15% relative standard deviation, respectively) of the method were good. The validated method successfully detected elevated levels of 2,6-DCP from plasma protein isolated from chlorine-exposed rats. Another method for the analysis of chlorine was developed for aqueous samples. As chlorine is a water-soluble compound, this toxic irritant gas forms hypochlorous acid and hydrochloric acid in an aqueous environment upon exposure. Here, we study hypochlorite anion (ClO-) in an aqueous solution with the fluorescent probe, as this technique has been known for its high sensitivity, better selectivity, fast response, and ease of use. In this study, we synthesized a probe called fluorescein thioacid (FSH) for rapid and sensitive ClO- detection in an aqueous solution. The probe FSH has shown the selectivity toward ClO- for the strong oxidative property, producing fluorescein. Probe FSH could detect in the range of 5-200 M with a detection limit of 1.72 M. The probe FSH is very easy to synthesize with excellent properties, including high selectivity, excellent sensitivity, good water solubility, and fast response. This probe would be beneficial to the analytical researchers for monitoring the ClO- levels in aqueous solutions. Cyanide is a TIA, as with chlorine, but inhibits mitochondrial cytochrome oxidase upon exposure by blocking electron transport and decreasing oxidative metabolism. Because each of the current antidotes, approved by the U.S. Food and Drug Administration (FDA) (i.e., hydroxocobalamin), has significant disadvantages, especially for mass casualty situations, dimethyl trisulfide (DMTS) has recently been developed as a next-generation cyanide antidote. DMTS converts cyanide to a less toxic substance called thiocyanate, which is more effective than thiosulfate and can be administered intramuscularly (IM). Hence, the pharmacokinetic behavior of intranasal (IN) and intramuscular (IM)-administration of DMTS was evaluated. A total of 47 rats and 35 swine were studied for IN and IM administration of DMTS. Generally, the PK characteristics of DMTS were well-suited for the rapid treatment of cyanide poisoning. These results should be helpful in elaborating guidelines for administering DMTS as a cyanide antidote.

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