John H. O'Haver

Nail morphology studies as assessments for onychomycosis treatment modalities

The purpose of this investigation was to study the morphology of the human nail treated with chemical penetration enhancers (CPE), bioadhesives and surface modifiers for assessment of topical treatment modalities for onychomycosis. CPEs, including dimethyl sulfoxide (DMSO) and urea were applied to human nail samples. Additional samples were treated with surface modifiers, tartaric acid (TTA) and phosphoric acid gel (PA). Other nail specimens were subjected to the bioadhesive polymers Carbopol 971P and Klucel MF. Atomic force microscopy (AFM), scanning electron microscopy (SEM) and polarized light microscopy (PLM) were utilized to visualize nail morphology and topographical changes of the human nail samples subjected to the various chemical agents. AFM, SEM and PLM micrographs revealed changes in topography to the dorsal layer when CPEs and surface modifiers were applied. Roughness scores as determined by NANOSCOPE IIIA software indicated a 2-fold increase when the dorsal nail layer was subjected to PA versus the control (147.8 vs. 85.0 nm, respectively). In contrast, when carbomer 971P was applied to the dorsal surface, roughness scores decreased significantly (44.6 vs. 85.0 nm, respectively). AFM, SEM and PLM studies of the human nail subjected to various chemical agents may be useful in the design and formulation of novel drug delivery systems for the topical treatment of onychomycosis. The AFM studies offer both a qualitative and quantitative assessment for nail treatment opportunities.

Comparison of rubber reinforcement using various surface-modified precipitated silicas

The reinforcement of a natural rubber compound by various surface-modified precipitated silicas was compared. Compound physical properties were determined for two silicas differing in surface area and were used as controls to evaluate these silicas after surface modification by using either a bifunctional organosilane coupling agent (γ-mercaptopropyl–trimethoxysilane) or a new surface modification process. This new process is based on the in situ polymerization of organic monomers solubilized inside surfactant bilayers that are adsorbed onto the silica surface to afford silicas modified with styrene–butadiene and styrene–isoprene copolymers. Both surface modification processes afford materials that dramatically increase the compound cure rate, thereby significantly reducing T90 cure times, while also improving tensile properties, tear strength, abrasion resistance, and compression set of the cured compound. The silane-modified silica gives a higher flex-cracking resistance than do the silicas modified by the in situ polymerization of organic monomers, whereas these latter silicas significantly increase rebound resilience and offer greater overall improvements in rubber compound performance. The rubber compound physical properties obtained using the modified, higher surface area Hi-Sil® 255 silica are generally improved relative to those obtained using the modified Hi-Sil® 233 silica.

Polar copolymer–surface-modified precipitated silica

To improve the performance of rubber compounds using precipitated silica as a reinforcing filler, the silica surface was directly modified by (1) adsorption of a surfactant onto the surface, (2) adsolubilization of an organic monomer, (3) in situ polymerization of the monomer in the surfactant bilayer, and (4) partial surfactant removal. Silica was thus modified using copolymers of isoprene or 1,3-butadiene with vinyl acetate, acrylonitrile, 4-methoxystyrene, 4-chlorostyrene, and methyl methacrylate on the silica surface. 4-Methoxystyrene/butadiene modification afforded the most promising candidate based on evaluation in a silica-filled, natural/styrene-butadiene rubber shoe sole compound that also has been used as a model tire compound. Physical testing showed that cure times were decreased, and break strength, tear energy, elongation to break, and cut growth resistance were increased. Thus, surface modification of silica by the in situ polymerization of organic monomers has been shown to be a flexible process capable of producing unique materials useful in improving rubber cure properties and the cured compound physical properties.

Effect of pH on adsolubilization of toluene and acetophenone into adsorbed surfactant on precipitated silica

The effect of pH on the adsorption of cetyltrimethylammonium bromide on precipitated silica and the adsolubilization of toluene and acetophenone in CTAB admicelles has been examined. Both single and mixed-solute systems were investigated at pH values 5 and 8. Adsorption results show, as expected, that adsorption increased with increasing pH. In the single solute systems, the adsolubilization of both solutes increased with increasing equilibrium concentration of the solute in the aqueous phase. For toluene, pH had little effect on the adsolubilization. In contrast, the pH effect on acetophenone was much more pronounced, with the adsolubilization increasing significantly when the pH was increased from 5 to 8. Thus, the properties of the electrical double layer in the admicelle affect the levels of adsolubilization for polar solutes. In mixed solute systems, the presence of acetophenone had an mildly synergistic effect on toluene adsolubilization whereas the presence of toluene had a strongly synergistic effect on acetophenone adsolubilization. The synergism was approximately the same at both pH values, indicating that the synergism is not a strong function of solution pH.

A platform for predicting and enhancing model drug delivery across the human nail plate

Purpose: The objective of the present study was to assess the effect of pretreatment using chemical etchants on the delivery of terbinafine hydrochloride (TH) and 5-fluorouracil (5-FU) into and across the human nail plate. Methods: The TranScreen-N method was used to screen five potential etchants. Based on these results, the dorsal surface of nails was pretreated with chemical etchants, 1% or 10% (w/w) phosphoric acid (PA) or 10% (w/w) lactic acid (LA) gels, for a period of 60 seconds. The nail pretreated with a plain gel formulation (no PA or LA incorporated) was used as the control. Results: Despite the differences in physicochemical properties between TH (log P = 3.3) and 5-FU (log P = −0.83), the in vitro permeation as well as drug load of these drugs in the nail plate was enhanced because of pretreatment with the PA gels, whereas LA pretreatment failed to enhance the drug load and permeation. Optical microscopic and atomic force microscopy studies revealed that the PA enhanced the trans-ungual drug delivery by decreasing the keratin density of the dorsal layer of the nail plate and by microstructural alterations. Conclusions: This study demonstrated that pretreatment of the nail plate with PA (1% or 10%, w/w) for a short duration could be a potential method of improving the efficiency of topical monotherapy treatment for nail diseases.

Removal of Trace Cd2+ Using Continuous Multistage Ion Foam Fractionation: Part II—The Effects of Operational Parameters

A multistage ion foam fractionation column with bubble-cap trays was employed to study the removal of cadmium ions from simulated wastewater having low Cd concentrations (10–30 mg/L), examining the effects of foam height, air flow rate, feed flow rate, and feed Cd concentration. Sodium dodecyl sulfate (SDS) was used to generate foam in this study. An increase in foam height, which reduces liquid hold-up in the generated foam, resulted in the enhancement of the enrichment ratios of both SDS and Cd while the removal and residual factor of Cd showed insignificant change. An increase in air flow rate increased the foam generation rate, foamate volumetric ratio, and the removal efficiency of Cd but decreased the enrichment ratios of both Cd and SDS. The separation factors of both Cd and SDS decreased with increasing feed flow rate, which is mainly attributable to both the effects of the enhancement of foamate volumetric ratio and the increases in both SDS and Cd input rates. An increase in feed Cd concentration was found to increase Cd effluent concentration and SDS removal but to decrease the enrichment ratios of both Cd and SDS because of the increasing liquid entrainment in the produced foam.

Effect of Water Content on Clay Pore Size using an Atomic Force Microscope

Clays and its composites have been widely used in the past as a secondary containment wall for underground storage tanks and landfills. The underground storage tanks are used commonly to store gasoline and other organic chemicals, both in the industry and the commercial market. Recent studies have shown that these secondary containment walls are failing. Gasoline and many other organic contaminants pass through clay liners without much effort. This study attempts to evaluate the changes occurring in the interactions between water molecules and clay particles at a microscopic level, using an atomic force microscope, for varying levels of water content. The pore size changes occurring in the clay particle lattice have a profound effect on the permeability of clay. The results show that the clay pore diameters reduce exponentially as the water content increases. This change of pore size can be attributed to the reduction in the size of the diffuse double layer and more extensive hydrogen bonds between clay particles and bipolar water molecules. Due to sample preparation difficulties, however, the pore diameters were obtained when the clay was dry, while interest for underground storage tank containment layer is for wet conditions.