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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of Solute Diffusion in a Polymer Using ATR-FTIR Spectroscopy and Bulk Transport Techniques (1994)
    s.l. : American Chemical Society
    Macromolecules 27 (1994), S. 5220-5222 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00096a055
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  • 2
    Electronic Resource
    Electronic Resource
    Secondary structural analysis of two recombinant murine proteins, interleukins 1.alpha. and 1.beta.: Is infrared spectroscopy sufficient to assign structure? (1992)
    s.l. : American Chemical Society
    Biochemistry 31 (1992), S. 27-31 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00116a006
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  • 3
    Electronic Resource
    Electronic Resource
    Solubility of neutral nickel in silicate melts and implications for the Earth's siderophile element budget (1992)
    [s.l.] : Nature Publishing Group
    Nature 357 (1992), S. 65-68 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] I equilibrated silicate melt (composition SiO2 54.4 wt%, A12O3 19.3%, CaO 9.0%, MgO 15.9%) with nickel or nickel-metal alloys in a Deltech gas-mixing furnace at selected values of oxygen fugacity (/o2 between 10~10 and 10~16) and temperatures (1,400, 1,500 and 1,560 °C) for times ranging ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/357065a0
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  • 4
    Electronic Resource
    Electronic Resource
    Validation of Reflectance Infrared Spectroscopy as a Quantitative Method to Measure Percutaneous Absorption In Vivo (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 1500-1506 
    Details
    ISSN: 1573-904X
    Keywords: skin penetration ; penetration enhancement ; oleic acid ; 4-cyanophenol ; infrared spectroscopy ; transdermal delivery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Attenuated total-reflectance infrared (ATR-IR) spectroscopy has been used to follow the penetration of a model compound (4-cyanophenol; CP) across human stratum corneum (SC) in vivo, in man. CP was administered for periods of 1, 2, or 3 hr, either (a) as a 10% (w/v) solution in propylene glycol or (b) in an identical vehicle which also contained 5% (v/v) oleic (cis-9-octadecenoic) acid. At the end of the treatment periods, SC at the application site was progressively removed by adhesive tape-stripping. Prior to the removal of the first tape-strip, and after each subsequent tape-strip, an ATR-IR spectrum of the treated site was recorded. The presence of CP, as a function of position in the SC, was monitored spectroscopically via the intense C≡N stretching absorbance at 2230 cm−1. The absolute amount of CP, as a function of SC depth, was determined by "spiking” the applied solutions with 14C-labeled compound and subsequent liquid scintillation counting of the removed tape-strips. The presence of oleic acid in the applied formulation significantly increased the rate and extent of CP delivery as evaluated by either spectroscopy or radiochemical analysis. Furthermore, the ATR-IR and direct 14C analysis of CP as a function of SC position were highly correlated. These data strongly support, therefore, the validation of ATR-IR as a quantitative tool to assess percutaneous penetration in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018987612155
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  • 5
    Electronic Resource
    Electronic Resource
    Letters to the Editor (1993)
    Springer
    Pharmaceutical research 10 (1993), S. 635-637 
    Details
    ISSN: 1573-904X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018982910454
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  • 6
    Electronic Resource
    Electronic Resource
    Does Hydration Affect Intercellular Lipid Organization in the Stratum Corneum? (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 1064-1065 
    Details
    ISSN: 1573-904X
    Keywords: stratum corneum ; skin hydration ; infrared spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015873511692
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  • 7
    Electronic Resource
    Electronic Resource
    Local Enhanced Topical Delivery (LETD) of Drugs: Does It Truly Exist? (1992)
    Springer
    Pharmaceutical research 9 (1992), S. 1422-1427 
    Details
    ISSN: 1573-904X
    Keywords: local enhanced topical delivery ; piroxicam ; rat in vivo model ; selective topical drug delivery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract There is considerable uncertainty over whether and to what extent topically applied drugs can be delivered directly to anatomical sites beneath the skin, without prior entry into the systemic blood circulation. The in vivo studies reported in this work were designed to assess whether local enhanced topical delivery (LETD) can be achieved with piroxicam, a nonsteroidal antiinflammatory drug. Equivalent doses of tritium-labeled drug were administered by the i.v. or topical routes to male rats. The topical plasma profile reveals a maximum concentration (Cpmax) at 12 hr, compared to a typical, multiexponential decline in plasma concentration after i.v. dosing. All four muscles from the topically dosed shoulder exhibit two distinct peaks, the first at 4 hr and a later one at 12 hr (which coincides with the topical Cpmax). The contralateral muscles from the non-dosed shoulder, in contrast, produce only a single peak at 12 hr after topical dosing. After the i.v. administration of piroxicam, the concentration-time profiles for each muscle closely parallel that seen for the i.v. plasma. Tissue-to-plasma ratios (T/P) show that the topical nondosed and the i.v. muscles are nearly constant over the entire time course of this study, indicating a pseudo-equilibrium between the plasma and those muscles. However, the early T/P ratios for the topically dosed muscles are markedly elevated and gradually decline to a constant value only after 12 hr, indicating that a similar pseudo-equilibrium is not established in this case. Thus, these results strongly imply that the topical administration of a drug can lead to LETD for tissues subjacent to the skin. Further, based on the elevated T/P ratios, these local enhanced drug levels cannot be solely attributed to entry from the systemic blood and suggest summarily that the cutaneous microvasculature is simply not an “infinite sink” for removal of all topically applied drugs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015854728278
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  • 8
    Electronic Resource
    Electronic Resource
    Percutaneous Penetration Enhancement in Vivo Measured by Attenuated Total Reflectance Infrared Spectroscopy (1990)
    Springer
    Pharmaceutical research 7 (1990), S. 835-841 
    Details
    ISSN: 1573-904X
    Keywords: skin penetration ; transdermal enhancement ; oleic acid ; 4-cyanophenol ; infrared spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A novel application of attenuated total reflectance IR Spectroscopy (ATR-IR) was used to monitor the outer several microns of the stratum corneum (SC) and, thereby, demonstrate enhanced percutaneous absorption in vivo in man. 4-Cyanophenol (CP) as a model permeant yielded a unique IR signal, distinct from those of the stratum corneum and the vehicle components. CP was administered for 1, 2, or 3 hr as a 10% (w/v) solution either in propylene glycol or in propylene glycol containing 5% (v/v) oleic acid. The absorbance at 2230 cm−1, which corresponded to C≡N bond stretching, diminished significantly faster when CP was codelivered with oleic acid. An IR absorbance due primarily to propylene glycol at 1040 cm−1 (C–O stretching) also disappeared more quickly following application of the enhancer-containing solution. In addition, only the formulations with oleic acid induced a higher wavenumber shift in the frequency of the asymmetric C–H bond stretching absorbance. This change indicates increased lipid-chain disorder, the mechanism by which oleic acid is believed to cause enhanced drug transport across the stratum corneum. Therefore, ATR-IR permits one to examine noninvasively the kinetics, extent, and mechanism of percutaneous penetration enhancement in vivo in human subjects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015960815578
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  • 9
    Electronic Resource
    Electronic Resource
    Oleic Acid: Its Effects on Stratum Corneum in Relation to (Trans)Dermal Drug Delivery (1990)
    Springer
    Pharmaceutical research 7 (1990), S. 621-627 
    Details
    ISSN: 1573-904X
    Keywords: enhanced topical delivery ; oleic acid ; hydrophilic permeants ; formulation optimization ; lipid phase-separation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Calorimetric studies with porcine stratum corneum (SC) have shown that the lipid phase transitions associated with the intercellular bilayers are markedly affected by treatment with oleic acid. Specifically, the transition temperatures (T m) and cooperativity are reduced, whereas no effect was observed on the endotherm associated with keratin denaturation, suggesting that oleic acid primarily affects the SC lipids. The decrease in the lipid-associated T m's was further correlated with the amount of oleic acid taken up by the SC. Parallel experiments with silastic implied that the uptake is dependent on the thermodynamic activity of oleic acid in the vehicle itself. The in vitro transport of Piroxicam across human and hairless mouse skin (HMS) was significantly enhanced by oleic acid, as a function of the extent of oleic acid uptake, with an attendant change in T m. These results emphasize the role of SC lipids in percutaneous absorption. Transport also depended on the donor concentration of ionized drug suggesting that the enhanced transport mechanism cannot be accounted for solely on the principles of the classical pH-partition hypothesis. Accordingly, a model of skin permeability enhancement involving solid-fluid phase separation within the SC lipids is proposed for oleic acid, consistent with the existing phospholipid literature. In conjunction with the use of oleic acid as an enhancer, very soluble hydrophilic salts were recognized as key factors in attaining maximum delivery. Oleic acid uptake, lipid ΔT m, and enhanced drug flux were all found to correlate, exhibiting a bell-shaped curve as a function of the ethanol vehicle concentration. Therefore, uptake and/or DSC experiments are useful for formulating enhanced topical delivery systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015822312426
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  • 10
    Electronic Resource
    Electronic Resource
    Evidence that Oleic Acid Exists in a Separate Phase Within Stratum Corneum Lipids (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 350-354 
    Details
    ISSN: 1573-904X
    Keywords: oleic acid ; penetration enhancer ; Fourier Transform Infrared Spectroscopy (FT-IR) ; lipid phase-separation transport mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Oleic acid is known to be a penetration enhancer for polar to moderately polar molecules. A mechanism related to lipid phase separation has been previously proposed by this laboratory to explain the increases in skin transport. In the studies presented here, Fourier transform infrared spectroscopy (FT-IR) was utilized to investigate whether or not oleic acid exists in a separate phase within stratum corneum (SC) lipids. Per-deuterated oleic acid was employed allowing the conformational phase behavior of the exogenously added fatty acid and the endogenous SC lipids to be monitored independently of each other. The results indicated that oleic acid exerts a significant effect on the SC lipids, lowering the lipid transition temperature (T m) in addition to increasing the conformational freedom or flexibility of the endogenous lipid alkyl chains above their T m. At temperatures lower than T m, however, oleic acid did not significantly change the chain disorder of the SC lipids. Similar results were obtained with lipids isolated from the SC by chloroform:methanol extraction. Oleic acid, itself, was almost fully disordered at temperatures both above and below the endogenous lipid T m in the intact SC and extracted lipid samples. This finding suggested that oleic acid does exist as a liquid within the SC lipids. The coexistence of fluid oleic acid and ordered SC lipids, at physiological temperatures, is consistent with the previously proposed phase-separation transport mechanism for enhanced diffusion. In this mechanism, the enhanced transport of polar molecules across the SC can be explained by the formation of permeable interfacial defects within the SC lipid bilayers which effectively decrease either the diffusional path length or the resistance, without necessarily invoking the formation of frank pores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015845632280
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