Method development for detecting the novel cyanide antidote dimethyl trisulfide from blood and brain, and its interaction with blood.

The antidotal potency of dimethyl trisulfide (DMTS) against cyanide poisoning was discovered and investigated in our previous studies. Based on our results it has better efficacy than the Cyanokit and the Nithiodote therapies that are presently used against cyanide intoxication in the US. Because of their absence in the literature, the goal of this work was to develop analytical methods for determining DMTS from blood and brain that could be employed in future pharmacokinetic studies. An HPLC-UV method for detection of DMTS from blood, a GC-MS method for detection of DMTS from brain, and associated validation experiments are described here. These analytical methods were developed using in vitro spiking of brain and blood, and are suitable for determining the in vivo DMTS concentrations in blood and brain in future pharmacokinetic and distribution studies. An important phenomenon was observed in the process of developing these methods. Specifically, recoveries from fresh blood spiked with DMTS were found to be significantly lower than recoveries from aged blood spiked in the same manner with DMTS. This decreased DMTS recovery from fresh blood is important, both because of the role it may play in the antidotal action of DMTS in the presence of cyanide, and because it adds the requirement of sample stabilization to the method development process. Mitigation procedures for stabilizing DMTS samples in blood are reported.

Intravascular Residence Time Determination for the Cyanide Antidote Dimethyl Trisulfide in Rat by Using Liquid-Liquid Extraction Coupled with High Performance Liquid Chromatography.

These studies represent the first report on the intravascular residence time determinations for the cyanide antidote dimethyl trisulfide (DMTS) in a rat model by using high performance liquid chromatography coupled with ultraviolet absorption spectroscopy (HPLC-UV). The newly developed sample preparation included liquid-liquid extraction by cyclohexanone. The calibration curves showed a linear response for DMTS concentrations between 0.010 and 0.30 mg/mL with R2 = 0.9994. The limit of detection for DMTS via this extraction method was 0.010 mg/mL, and the limit of quantitation was 0.034 mg/mL. Thus this calibration curve provided a tool for determining DMTS in the range between 0.04 and 0.30 mg/mL. Rats were given 20 mg/kg DMTS dose (in 15% Polysorbate 80) intravenously, and blood samples were taken 15, 60, 90, 120, and 240 min after DMTS injections. The data points were plotted as DMTS concentration in RBCs versus time, and the intravascular residence time was determined graphically. The results indicated a half-life of 36 min in a rat model, suggesting that the circulation time is long enough to provide a reasonable time interval for cyanide antagonism.

Microsphere lithography on hydrophobic surfaces for generating gold films that exhibit infrared localized surface plasmon resonances.

Evaporation induced self-assembly is an established method for producing close-packed two-dimensional sphere masks on hydrophilic surfaces such as glass. In sphere lithography, gold or silver is deposited over sphere masks to generate a film-over-nanospheres or a nanoprism array that can be used as a sensing surface in localized surface plasmon extinction and surface enhanced Raman spectroscopy experiments. Sphere lithography is less commonly used to prepare sphere masks on hydrophobic surfaces associated with infrared window materials, in part because it is challenging to find solvents with wetting and evaporation characteristics that are appropriate for such surfaces. This wetting challenge can be overcome with appropriate surfactants. However, surfactant residues are then left behind on the sensing surface. We report methods for depositing monolayer crystalline sphere masks onto CaF2 windows that minimize surfactant residue by either using ethanol as a volatile cosolvent that enhances wetting, or by increasing the concentration of colloid to compensate for the reduced attractions between spheres and surface. The rate of evaporation of solvents from the colloid drop is controlled by fixing the headspace partial pressure of ethanol and/or water.