Christopher W. Shade, PhD: Defining Cannabinoids

No Abstract Available.

Liposomes as Advanced Delivery Systems for Nutraceuticals

Liposomes are delivery vehicles for transporting substances into the body effectively via facilitating absorption directly in the mouth or by preventing breakdown by stomach acid. Since the 1970s, liposomes have been investigated as potential drug delivery systems because of their biocompatibility and ability to incorporate both hydrophilic and hydrophobic therapeutic agents. Despite early promise, it was decades later, in the late 1990s to the present, that liposome technologies could create successful commercial products. Oral deliveries are recently emerging as availability of quality phospholipids and reliable homogenization and sizing equipment have become routinely available. Nutritional industry use of liposomes will grow rapidly in the next 5-10 y. High-quality products with more complex mixtures of pure compounds and complex botanical mixtures will offer clinicians less-invasive options for dosing and delivery of these actives.

Automated simultaneous analysis of monomethyl and mercuric Hg in biotic samples by Hg-thiourea complex liquid chromatography following acidic thiourea leaching

A simple leaching procedure has been validated for quantitative isolation of both monomethyl (CH3Hg+) and inorganic (Hg(II)) mercuryfrom fresh or dried biotic tissue for simultaneous analysis via separation and quantification with Hg-thiourea complex liquid chromatography cold vapor atomic fluorescence spectrometry (HgTU/LC-CVAFS). The leaching solution comprises thiourea, hydrochloric acid, and glacial acetic acid and works by protonating thiol binding sites and forming water-soluble cationic CH3HgS=C(NH2)2+ and Hg[S=C(NH2)2]2(2+) complexes, which are easily separated from the solid matrix. The isolated complexes are preconcentrated online by either thiol resin trapping or a new iodide-complex polydivinylbenzene resin trapping (I-PDVB). The I-PDVB trapping involves only one reagent addition, requires no pH adjustments, and is quantitative over a large range of volumes and flow rates. The chromatography system can use either ion chromatography or a new ion-pairing reversed phase separation coupled to cold vapor generation and atomic fluorescence detection. The system allows quantitative sample introduction and yields absolute detection limits of 0.4 pg and 0.7 pg, for CH3Hg+ and Hg(II) respectively, enabling relative detection limits as low as 4 and 7 pg g(-1) with 100 mg samples, and yields % CV routinely less than 5% with well homogenized samples. Accuracy for both forms of mercury has been validated with multiple biotic reference materials and by comparison of the sum of CH3Hg+ and Hg(II) with total Hg on a variety of different biotic sample types (n = 49). The system can be calibrated with either aqueous standards or leached reference materials.

Characterization of methyl mercury in dental wastewater and correlation with sulfate-reducing bacterial DNA

Dental wastewater (DWW) was collected over two months from a 12-chair clinic and a single-chair office to identify conditions that may affect Hg methylation. DWW was settled for 24 h and samples were collected from the top and bottom of the supernatant to simulate a range of particles that may escape in-line traps. Total Hg spanned 5 orders of magnitude (0.02-5000 microM), following a log-normal distribution with p10, p50, and p90 concentration values of 0.24, 31 and 4000 microM, respectively; typically well in excess of free aqueous Hg solubility. Methyl Hg was present in high levels (2-270 nM), also following a log-normal distribution with p10, p50, and p90 concentration values of 2.8, 17, and 100 nM, respectively. There were no statistically significant differences (90% CI) in p50 methyl Hg or total Hg between the clinic and office. Methyl Hg was predicted from total Hg data by (+/- 95% CI): Log (Me-Hg) = 0.33 (+/- 0.06) x Log (T-Hg) - 2.27 (+/- 0.13). Total methyl Hg from DWW to U.S. wastewater collection systems is estimated to be 2-5 kg yr(-1). Equilibrium speciation modeling predicted that DWW Hg was primarily in sulfide-Hg complexes, except at high total Hg levels where organo-Hg complexes become significant. DNA extracts amplified by quantitative polymerase chain reaction with primers for total eubacteria and sulfate-reducing bacteria (SRB) indicated that the total eubacterial DNA was composed primarily of SRB, and highly significant correlations were found between methyl Hg and both amplified Desulfobacteraceae (p < 0.0001) and Desulfovibrionacaea DNA (p < 0.00001). Both are known Hg methylators. In marked contrast, there was no significant correlation between methyl Hg and amplified Desulfobulbus DNA, a genus generally not known to methylate Hg at high rates. These results strongly suggest that SRB are implicated in DWW Hg methylation.

Determination of MeHg in environmental sample matrices using Hg-thiourea complex ion chromatography with on-line cold vapor generation and atomic fluorescence spectrometric detection

A novel system for mercury speciation analysis using high-pressure ion chromatography (IC) has been developed and validated. Its chemistry permits separation of the two most abundant forms of Hg in natural waters, soils, sediments, and biota-monomethyl Hg (CH3Hg+) and mercuric Hg (Hg2+)-on the basis of the difference in charge of their respective thiourea (S=C(NH2)20) complexes. Once separated, both species are converted to Hg0 on-line and quantified by cold-vapor atomic fluorescence spectrometry (CVAFS). A column containing thiol-functionalized silica resin installed in the sample loop of the IC system traps Hg2+ and CH3Hg+ from prepared sample solutions without retaining interfering sample matrix components. The resulting matrix-independent chemistry permits external calibration of the system and a high sample throughput ( approximately 6 samples per hour). The system's accuracy has been validated with environmentally relevant reference materials. Figures of merit for the system, an average precision of approximately 2.5% and an absolute detection limit of <1 pg, are comparable to state-of-the-art gas chromatography approaches for Hg speciation analysis (ethylation/GC-CVAFS) and meet or exceed those of all extant LC systems. Low relative detection limits are attainable through preconcentration onto the thiol resin.