Monitoring of biomarkers, like urea, prostate-specific antigen (PSA), and osteopontin, is very important because they are related to kidney disease, prostate cancer, and ovarian cancer, respectively. It is well known that reverse iontophoresis can enhance transdermal extraction of small molecules, and even large molecules if reverse iontophoresis is used together with electroporation. Electroporation is the use of a high-voltage electrical pulse to create nanochannels within the stratum corneum, temporarily and reversibly. Reverse iontophoresis is the use of a small current to facilitate both charged and uncharged molecule transportation across the skin. The objectives of this in vitro study were to determine whether PSA and osteopontin are extractable transdermally and noninvasively and whether urea, PSA, and osteopontin can be extracted simultaneously by electroporation and reverse iontophoresis.
All in vitro experiments were conducted using a diffusion cell assembled with the stratum corneum of porcine skin. Three different symmetrical biphasic direct currents (SBdc), five various electroporations, and a combination of the two techniques were applied to the diffusion cell via Ag/AgCl electrodes. The three different SBdc had the same current density of 0.3 mA/cm2, but different phase durations of 0 (ie, no current, control group), 30, and 180 seconds. The five different electroporations had the same pulse width of 1 msec and number of pulses per second of 10, but different electric field strengths of 0 (ie, no voltage, control group), 74, 148, 296, and 592 V/cm. Before and after each extraction experiment, skin impedance was measured at 20 Hz.
It was found that urea could be extracted transdermally using reverse iontophoresis alone, and further enhancement of extraction could be achieved by combined use of electroporation and reverse iontophoresis. Conversely, PSA and osteopontin were found to be extracted transdermally only by use of reverse iontophoresis and electroporation with a high electrical field strength (>296 V/cm). After application of reverse iontophoresis, electroporation, or a combination of the two techniques, a reduction in skin impedance was observed.
Simultaneous transdermal extraction of urea, PSA, and osteopontin is possible only for the condition of applying reverse iontophoresis in conjunction with high electroporation.
electroporation; reverse iontophoresis; nanochannels; noninvasive; urea; prostate-specific antigen; osteopontin
The standard method used to determine the potency of antihistaminesis to assess the degree of suppression of skin response to histamine challenge.
The aims of this study were to compare the efficacy of 3 antihistaminesusing a histamine challenge test and the usefulness of on-site evaluation with that of photographic evaluation of skin-test reactions.
In this prospective, double-blind, crossover study, healthy volunteerswere given cetirizine 5 mg (CTZ-5) and 10 mg (CTZ-10), loratadine 10 mg (LOR), fexofenadine 60 mg BID (FEX), and placebo (PLC), in a randomly assigned order, with an interval of at least 1 week between treatments. Before and 0.5 to 24 hours after administration, the areas of flare and wheal induced by histamine iontophoresis were measured directly (on site) by 1 evaluator and by another evaluator using photographic images on a computer monitor.
Ten healthy volunteers (6 men, 4 women; mean age, 28.2 years[range, 20–39 years]; mean weight, 60.7 kg [range, 41–81 kg]) were enrolled. The data from 9 subjects were analyzed; the data from 1 subject were omitted because the subject used an over-the-counter cold medication containing diphenhydramine several times during the study. By both methods, all antihistamines were shown to suppress flare significantly from 4 to 24 hours after administration. CTZ was most potent in suppressing both flare and wheal. For flare, the areas as measured using on-site evaluation were larger overall than those measured using photographic evaluation, but the shapes of the time-course graphs were similar for both. Overall, the flare area measurements started to decrease significantly from baseline values 4 hours after drug administration, reached a nadir at 10.5 hours, and remained significantly lower compared with baseline values at 24 hours. Comparisons between antihistamines showed significant differences in mean flare areas between the 2 doses of CTZ and LOR from 8 to 12 hours after administration in both evaluation methods. The wheal areas were significantly reduced from baseline values by most of the antihistamines 4 to 12 hours after drug administration, reached their lowest values at 10.5 hours, and returned to near-baseline values at 24 hours. Comparisons with PLC values at each time point, however, showed significant differences only for CTZ-5 and CTZ-10 from 4 to 12 hours after administration. Comparison between antihistamines showed significant differences in mean flare areas between the 2 doses of CTZ and LOR from 8 to 12 hours after administration in both evaluation methods. Although the flare areas measured by both methods correlated linearly (r = 0.90; P < 0.001), the correlation for wheal areas was weaker (r = 0.76; P < 0.001).
In this study in healthy volunteers, single doses of CTZ 5 mg and CTZ 10 mg were more potent compared with single-dose LOR 10 mg and FEX 60 mg BID in suppressing skin response. Although linear correlations were found between skin-response areas, as measured by on-site and photographic evaluation, it was difficult to differentiate between wheal and flare by photographic evaluation, especially when a typical wheal was suppressed to slightly edematous erythema by antihistamines.
antihistamine; histamine iontophoresis; histamine challenge test; ImageJ; fexofenadine; loratadine; cetirizine; wheal; flare
Iontophoresis is used frequently in physical medicine and rehabilitation, but many research techniques do not adequately measure it for depth of medicine delivery.
To determine if iontophoresis delivers lidocaine 5 mm under the surface of human skin.
Descriptive laboratory study.
Therapeutic modalities research laboratory.
Patients or Other Participants:
Eight men and 5 women volunteers (age range = 21 ± 2.3 years) who had less than 5 mm of adipose tissue in the area we measured participated in the study.
We inserted a microdialysis probe 5 mm under the skin of both legs and into the triceps surae muscle groups of 10 participants. Microdialysis was performed for 60 minutes to allow a recovery period for local skin blood flow to return to baseline. We then delivered 2 mL of 1% lidocaine to the treatment leg via iontophoresis at 40 mA/min. Next, microdialysis was performed continuously in both legs during the treatment and for 30 minutes posttreatment to collect the lidocaine samples. After we had gathered the samples, several saline solutions with various amounts of lidocaine (0.005%, 0.025%, 0.05%, and 0.1%) were prepared in vitro and analyzed. Although we did not intend to do so as a part of the original study, we also performed an identical follow-up study at 3 mm in 3 participants.
Main Outcome Measure(s):
Both in vitro and in vivo samples were analyzed via reverse-phase high-performance liquid chromatography (RP-HPLC). A protocol for detection and quantification of lidocaine using RP-HPLC was followed.
We did not detect any measurable levels or concentrations of lidocaine in the 10 control samples. According to the RP-HPLC analysis, the 10 treatment samples also were negative for the presence of lidocaine. However, when we performed the study at 3 mm, microdialysis detected lidocaine in the 3 participants at this depth in the treatment leg only.
Measurable levels of lidocaine were not detected at 5 mm but were found at 3 mm. More studies are needed to determine the efficacy of microdialysis in measuring iontophoresis-delivered compounds.
drug delivery; electricity
1.25 per cent gelatin solutions containing enough NaOH to bring them to pH 7.367 (or KOH to pH 7.203) were made up with various concentrations of NaCl, KCl and MgCl2, alone and in mixtures, up to molar ionic strength. The effects of these salts on the pH were observed. MgCl2 and NaCl alone lower the pH of the Na gelatinate or the K gelatinate, in all amounts of these salts. KCl first lowers the pH (up to 0.01 M K+), then raises the pH. Mixtures of NaCl and KCl (up to 0.09 M of the salt whose concentration is varied) raise the pH; then (up to 0.125 M Na+ or K+) lower the pH; and finally (above 0.125 M) behave like KCl alone. Mixtures of MgCl2 and NaCl raise the pH up to 0.10 M Na+, and lower it up to 0.15 M Na+ regardless of the amount of MgCl2. Higher concentrations of NaCl have little effect, but the pH in this range of NaCl concentration is lowered with increase of MgCl2. Mixtures of MgCl2 and KCl behave as above described (for MgCl2 and NaCl) and the addition of NaCl plus KCl to gelatin containing MgCl2 produces essentially the same effect as the addition of either alone, except that the first two breaks in this curve come at 0.07 M and 0.08 M [Na+ + K+] and there is a third break at 0.12 M. In this pH range the free groups of the dicarboxylic acids and of lysine are essentially all ionized and the prearginine and histidine groups are essentially all non-ionized. The arginine group is about 84 per cent ionized. Hence we are studying a solution with two ionic species in equilibrium, one with the arginine group ionized, and one with it non-ionized. It is shown that the effect of each salt alone depends upon the effect of the cation on the activity of these two species due to combination. The anomalous effects of cation mixtures may be qualitatively accounted for if one or both of these species fail to combine with the cations in a mixture in proportion to the relative combination in solutions of each cation alone. Special precautions were taken to ensure accuracy in the pH measurements. The mother solutions gave identical readings to 0.001 pH and the readings with salts were discarded when not reproducible to 0.003 pH. All doubtful data were discarded.
The pH of a 0.01 molar solution of glycine, half neutralized with NaOH, is 9.685. Addition of only one of the salts NaCl, KCl, MgCl2, or CaCl2 will lower the pH of the solution (at least up to 1 µ). If a given amount of KCl is added to a glycine solution, the subsequent addition of increasing amounts of NaCl will first raise the pH (up to 0.007 M NaCl). Further addition of NaCl (up to 0.035 M NaCl) will lower the pH, and further additions slightly raise the pH. The same type of curve is obtained by adding NaCl to glycine solution containing MgCl2 or CaCl2 except that the first and second breaks occur at 0.015 M and 0.085 M NaCl, respectively. Addition of CaCl2 to a glycine solution containing MgCl2 gives the same phenomena with breaks at 0.005 M and 0.025 M CaCl; or at ionic strengths of 0.015 µCaCl2 and 0.075 µCaCl2. This indicates that the effect is a function of the ionic strength of the added salt. These effects are sharp and unmistakable. They are almost identical with the effects produced by the same salt mixtures on the pH of gelatin solutions. They are very suggestive of physiological antagonisms, and at the same time cannot be attributed to colloidal phenomena.
Previous studies have demonstrated the ability of AC iontophoresis to control skin resistance in different transdermal iontophoresis applications. The objectives of the present study were to (a) identify the alternating current (AC) frequency for the optimization of AC pore induction of human epidermal membrane (HEM) and (b) determine the effects of chemical permeation enhancers upon the extent of pore induction under AC conditions. Experiments with a synthetic membrane system were first conducted as the control. In these synthetic membrane experiments, the electrical resistance of the membrane remained essentially constant, suggesting constant electromobility of the background electrolyte ions under the AC conditions studied. In the HEM experiments, the electrical resistance data showed that higher applied voltages were required to induce the same extent of pore induction in HEM at AC frequency of 1 kHz compared with those at 30 Hz. Even higher voltages were needed at AC frequencies of 10 kHz and higher. AC frequency also influenced the recovery of HEM electrical resistance after AC iontophoresis application. An optimal AC frequency region for effective pore induction and least sensation was proposed. Permeation enhancers were shown to enhance pore induction in HEM during AC iontophoresis. The enhancers reversibly reduced the AC voltage required to sustain a constant state of pore induction in HEM during AC iontophoresis, consistent with the mechanism of lipid lamellae electroporation in the stratum corneum.
Constant skin resistance AC iontophoresis; AC; human epidermal membrane; skin electrical resistance; permeation enhancer
Fleming, H. P. (University of Illinois, Urbana), and Z. John Ordal. Responses of Bacillus subtilis spores to ionic environments during sporulation and germination. J. Bacteriol. 88:1529–1537. 1964.—The ionic environments of germination and sporulation menstrua had a prominent influence on characteristics of Bacillus subtilis spores. There was a synergistic effect for l-alanine and inorganic ions on spore germination. The maximal rate of germination in solutions of l-alanine was dependent on ionic concentration and species. Germination was negligible in l-alanine at low ionic strength but increased as the ionic strength was increased up to about 10−1m with a variety of salts. Phosphate was the most active ion tested, and divalent cations were the least active in supporting germination in l-alanine. Germination progressed slowly at 45 C in sodium chloride or sodium phosphate alone but not in CaCl2 alone. Germination rates in l-alanine were retarded at high ionic strengths (μ in the range of 0.1 to 1.0). Inhibitory effects of high concentrations of certain divalent cations on germination were related to the binding abilities of these metals. High concentrations of NaCl (10−1 to 1.0 m) in the sporulation medium resulted in lowered heat resistance and germination rate of the resulting spores. The addition of calcium (5 × 10−2m CaCl2) to the sporulation medium relieved the repression of NaCl on germination and caused the spores to have a greater heat resistance. Calcium and dipicolinic acid (DPA) contents of the spores were unaffected by NaCl in the sporulation medium. The calcium, but not the DPA, content of spores increased as a result of supplementing the sporulation medium with calcium. Possible roles of ions in the germination of spores are discussed.
1. When pure water is separated by a collodion membrane from a watery solution of an electrolyte the rate of diffusion of water is influenced not only by the forces of gas pressure but also by electrical forces. 2. Water is in this case attracted by the solute as if the molecules of water were charged electrically, the sign of the charge of the water particles as well as the strength of the attractive force finding expression in the following two rules, (a) Solutions of neutral salts possessing a univalent or bivalent cation influence the rate of diffusion of water through a collodion membrane, as if the water particles were charged positively and were attracted by the anion and repelled by the cation of the electrolyte; the attractive and repulsive action increasing with the number of charges of the ion and diminishing inversely with a quantity which we will designate arbitrarily as the "radius" of the ion. The same rule applies to solutions of alkalies. (b) Solutions of neutral or acid salts possessing a trivalent or tetravalent cation influence the rate of diffusion of water through a collodion membrane as if the particles of water were charged negatively and were attracted by the cation and repelled by the anion of the electrolyte. Solutions of acids obey the same rule, the high electrostatic effect of the hydrogen ion being probably due to its small "ionic radius." 3. The correctness of the assumption made in these rules concerning the sign of the charge of the water particles is proved by experiments on electrical osmose. 4. A method is given by which the strength of the attractive electric force of electrolytes on the molecules of water can be roughly estimated and the results of these measurements are in agreement with the two rules. 5. The electric attraction of water caused by the electrolyte increases with an increase in the concentration of the electrolyte, but at low concentrations more rapidly than at high concentrations. A tentative explanation for this phenomenon is offered. 6. The rate of diffusion of an electrolyte from a solution to pure solvent through a collodion membrane seems to obey largely the kinetic theory inasmuch as the number of molecules of solute diffusing through the unit of area of the membrane in unit time is (as long as the concentration is not too low) approximately proportional to the concentration of the electrolyte and is the same for the same concentrations of LiCl, NaCl, MgCl2, and CaCl2.
The objective was to relate the efficiency of a charged drug to carry current across the skin during iontophoresis to its structural and/or physicochemical properties. The corollary was the establishment of a predictive relationship useful to predict the feasibility of iontophoretic drug delivery, and for the selection and optimization of drug candidates for this route of administration. A dataset of 16 cations, for which iontophoretic fluxes have been measured under identical conditions, with no competition from exogenous co-ions, was compiled. Maximum transport numbers correlated with ion mobilities and decreased with ionic size, the dependence indicating that the electromigration mechanism of iontophoresis would become negligible for drugs of hydrodynamic radius greater than about 8Å. Validation of the model was demonstrated by successfully predicting the transport numbers of three structurally distinct dipeptides, the iontophoretic data for which had been determined under distinctly different experimental conditions. Finally, for the “training” set of cations, a strong linear dependence between their transport numbers in skin and those in aqueous solution was demonstrated; the former were larger by approximately a factor of 1.4 consistent with skin’s cation permselectivity. In conclusion, this research offers a practical contribution to the development of a predictive structure-transport model of iontophoresis.
iontophoresis; skin; transport number; conductivity; structure-transport relationship
The objectives of this study were to investigate the effects of hydration and solution ion concentration on the electrical properties of human nail in vivo and compare these in vivo results with those in vitro. In vivo electrical resistance measurements on the nail were conducted with a three-electrode system in phosphate buffered saline of 0.01–0.6 M. The effect of electric current on nail resistance and possible adverse effects were studied under 1.5- and 9-V iontophoresis in vivo. The electrical resistance of the nail plate was measured in vitro in side-by-side diffusion cells under the same conditions and compared with those in vivo. The in vivo electrical resistance decreased significantly upon 2-h nail hydration and then slowly decreased to a constant value, showing the same pattern as that in vitro. No significant effect of the applied voltage upon the nail electrical resistance was observed. Higher current densities caused moderate sensation and slight changes in nail appearance after iontophoresis. The observed decrease in nail resistance demonstrates the significance of nail hydration in transungual iontophoresis. The in vitro and in vivo correlation suggests that the in vitro nail plate can be a model in the research and development of transungual iontophoretic delivery.
iontophoresis; human nail plate; constant voltage; hydration; electrical property
The maximal calcium-activated isometric tension produced by a skinned frog single muscle fiber falls off as the ionic strength of the solution bathing this fiber is elevated declining to zero near 0.5 M as the ionic strength is varied using KCl. When other neutral salts are used, the tension always declines at high ionic strength, but there is some difference between the various neutral salts used. The anions and cations can be ordered in terms of their ability to inhibit the maximal calcium-activated tension. The order of increasing inhibition of tension (decreasing tension) at high ionic strength for anions is propionate- ≃ SO4-- < Cl- < Br-. The order of increasing inhibition of calcium-activated tension for cations is K+ ≃ Na+ ≃ TMA+ < TEA+ < TPrA+ < TBuA+. The decline of maximal calcium-activated isometric tension with elevated salt concentration (ionic strength) can quantitatively explain the decline of isometric tetanic tension of a frog muscle fiber bathed in a hypertonic solution if one assumes that the internal ionic strength of a muscle fiber in normal Ringer's solution is 0.14–0.17 M. There is an increase in the base-line tension of a skinned muscle fiber bathed in a relaxing solution (no added calcium and 3 mM EGTA) of low ionic strength. This tension, which has no correlate in the intact fiber in hypotonic solutions, appears to be a noncalcium-activated tension and correlates more with a declining ionic strength than with small changes in [MgATP], [Mg], pH buffer, or [EGTA]. It is dependent upon the specific neutral salts used with cations being ordered in increasing inhibition of this noncalcium-activated tension (decreasing tension) as TPrA+ < TMA+ < K+ ≃ Na+. Measurements of potentials inside these skinned muscle fibers bathed in relaxing solutions produced occasional small positive values (<6 mV) which were not significantly different from zero.
By means of micro-dissection and injection Amœba proteus was treated with the chlorides of Na, K, Ca, and Mg alone, in combination, and with variations of pH. I. The Plasmalemma. 1. NaCl weakens and disrupts the surface membrane of the ameba. Tearing the membrane accelerates the disruption which spreads rapidly from the site of the tear. KCl has no disruptive effect on the membrane but renders it adhesive. 2. MgCl2 and CaCl2 have no appreciable effect on the integrity of the surface membrane of the ameba when applied on the outside. No spread of disruption occurs when the membrane is torn in these salts. When these salts are introduced into the ameba they render the pellicle of the involved region rigid. II. The Internal Protoplasm. 3. Injected water either diffuses through the protoplasm or becomes localized in a hyaline blister. Large amounts when rapidly injected produce a "rushing effect". 4. HCl at pH 1.8 solidifies the internal protoplasm and at pH 2.2 causes solidification only after several successive injections. The effect of the subsequent injections may be due to the neutralization of the cell-buffers by the first injection. 5. NaCl and KCl increase the fluidity of the internal protoplasm and induce quiescence. 6. CaCl2 and MgCl2 to a lesser extent solidify the internal protoplasm. With CaCl2 the solidification tends to be localized. With MgCl2 it tends to spread. The injection of CaCl2 accelerates movement in the regions not solidified whereas the injection of MgCl2 induces quiescence. III. Pinching-Off Reaction. 7. A hyaline blister produced by the injection of water may be pinched off. The pinched-off blister is a liquid sphere surrounded by a pellicle. 8. Pinching off always takes place with injections of HCl when the injected region is solidified. 9. The injection of CaCl2 usually results in the pinching off of the portion solidified. The rate of pinching off varies with the concentration of the salt. The injection of MgCl2 does not cause pinching off. IV. Reparability of Torn Surfaces. 10. The repair of a torn surface takes place readily in distilled water. In the different salt solutions, reparability varies specifically with each salt, with the concentration of the salt, and with the extent of the tear. In NaCl and in KCl repair occurs less readily than in water. In MgCl2 repair takes place with great difficulty. In CaCl2 a proper estimate of the process of repair is complicated by the pinching-off phenomenon. However, CaCl2 is the only salt found to increase the mobility of the plasmalemma, and this presumably enhances its reparability. 11. The repair of the surface is probably a function of the internal protoplasm and depends upon an interaction of the protoplasm with the surrounding medium. V. Permeability. 12. NaCl and KCl readily penetrate the ameba from the exterior. CaCl2 and MgCl2 do not. 13. All four salts when injected into an ameba readily diffuse through the internal protoplasm. In the case of CaCl2 the diffusion may be arrested by the pinching-off process. VI. Toxicity. 14. NaCl and KCl are more toxic to the exterior of the cell than to the interior, and the reverse is true for CaCl2 and MgCl2. 15. The relative non-toxicity of injected NaCl to the interior of the ameba is not necessarily due to its diffusion outward from the cell. 16. HCl is much more toxic to the exterior of a cell than to the interior; at pH 5.5 it is toxic to the surface whereas at pH 2.5 it is not toxic to the interior. NaOH to pH 9.8 is not toxic either to the surface or to the interior. VII. Antagonism. 17. The toxic effects of NaCl and of KCl on the exterior of the cell can be antagonized by CaCl2 and this antagonism occurs at the surface. Although the lethal effect of NaCl is thus antagonized, NaCl still penetrates but at a slower rate than if the ameba were immersed in a solution of this salt alone. 18. NaCl and HCl are mutually antagonistic in the interior of the ameba. No antagonism between the salts and HCl was found on the exterior of the ameba. No antagonism between the salts and NaOH was found on the interior or exterior of the ameba. 19. The pinching-off phenomenon can be antagonized by NaCl or by KCl, and the rate of the retardation of the pinching-off process varies with the concentration of the antagonizing salt. 20. The prevention of repair of a torn membrane by toxic solutions of NaCl or KCl can be antagonized by CaCl2. These experiments show directly the marked difference between the interior and the exterior of the cell in their behavior toward the chlorides of Na, K, Ca, and Mg.
Purpose: The objective of this study was to investigate the use of iontophoresis, soluble microneedles and their combination for the transdermal delivery of glycopyrrolate. Methods: In vitro permeation was tested using full thickness porcine ear skin mounted onto Franz diffusion cells. Iontophoresis (0.5 mA/cm2) was done for 4 h using Ag/AgCl electrodes. For microneedles, three line array (27 needles/line) of maltose microneedles were used to microporate the skin prior to mounting. Pore uniformity was determined by taking fluorescent images of distribution of calcein into pores and processing the images using an image analysis tool, which measured the fluorescent intensity in and around each pore to provide a pore permeability index (PPI). The donor chamber contained 500 µL of a 1 mg/mL solution of glycopyrrolate, and the receptor chamber contained 5 mL of 50 mM NaCl in deionized water. Samples were collected at predetermined time points over a period of 24 h and analyzed by HPLC. Skin irritation testing was performed with a 3D cell culture kit of human skin. MTT assay determined cell viability; viability less than 50% was considered irritant. Results: A control experiment which investigated passive permeation of glycopyrrolate delivered an average cumulative amount of 24.92 ± 1.77 µg/cm2 at 24 h, while microneedle pretreatment increased permeability to 46.54 ± 6.9 µg/cm2. Both iontophoresis (158.53 ± 17.50 µg/cm2) and a combination of iontophoresis and microneedles (182.43 ± 20.06 µg/ cm2) significantly increased delivery compared to passive and microneedles alone. Glycopyrrolate solution was found to be nonirritant with cell viability of 70.4% ± 5.03%. Conclusion: Iontophoresis and a combination of iontophoresis with microneedle pretreatment can be effectively used to enhance the transdermal delivery of glycopyrrolate. Glycopyrrolate was found to be non-irritant to skin.
iontophoresis; microneedles; transdermal; quaternary ammonium; glycopyrrolate
Understanding the mechanical functions of specific cartilage molecules such as aggrecan is important for understanding both healthy cartilage and disease progression. Cartilage is primarily composed of chondrocytes and an extracellular matrix consisting of multiple biopolymers, ions, and water. Aggrecan is one matrix biopolymer which consists of a core protein and multiple anionic glycosaminoglylcans. Previous research has demonstrated that the stiffness of extracted aggrecan decreases under increased solution cation concentration, and the purpose of this study was to determine whether changes in solution ion concentration resulted in changes in tissue-level viscoelastic properties.
Middle-zone explants of bovine calf patellofemoral cartilage were harvested and cultured overnight before mechanical testing. Repeated stress-relaxation and cyclical loading tests were performed after equilibration in solutions of 0.15M and 1M NaCl and 0.075M and 0.5M CaCl2. A stretched exponential model was fit to the stress-relaxation data. Storage and loss moduli were determined from the cyclical loading data.
Changes in ionic strength and species affected both stress-relaxation and cyclical loading of cartilage. Stress-relaxation was faster under higher ionic strength. CaCl2 concentration increases resulted in decreased peak stress, while NaCl increases resulted in decreased equilibrium stress. Storage and loss moduli were affected differently by NaCl and CaCl2.
These results show that cartilage stress-relaxation proceeds faster under higher concentrations of solution cations, consistent with the theory of polymer dynamics. These data demonstrate the complexity of cartilage mechanical properties and suggest that aggrecan stiffness may be important in tissue level cartilage viscoelastic properties.
Cartilage biomechanics; flow-independent viscoelasticity; polymer dynamics; cartilage mechanics
These investigations are concerned with the ionic and substrate-site requirements of ribosomal ribonucleic acid (rRNA)-adenine (N6-) methylase of Escherichia coli B. The methylase was essentially inactive in solutions of low ionic strength. The addition of MgCl2 (optimal at 5 mM) or; to a lesser degree, KCl (optimal at 45 mM) stimulated the rate of methylation; the combination of MgCl2 and KCl stimulated methylation to an extent equivalent to the sum of the stimulation of each acting alone. The extent of nonspecific binding of the methylase to rRNA decreased as the ionic strength of the solution increased. In the absence of ions, dimethylsulfoxide (DMSO), a nucleic acid denaturing agent, had little influence on the rate of methylation; however, DMSO plus KCl synergistically increased both the rate and the extent of methylation to a greater degree than the combination of Mg2+ plus K+. NH4+ was less effective than K+, and the divalent Mg2+ offered little stimulation. Monovalent anions (acetate, nitrate, and chloride) were equally effective, whereas divalent SO42− was decidedly inhibitory. The appropriate ionic milieu of mono- and divalent cations was required to provide the appropriate conformation of the rRNA and to facilitate specific interactions of the methylase and its recognition sites in the rRNA, while decreasing nonspecific ionic binding of the methylase to rRNA. DMSO may facilitate methylation by increasing the number of substrate sites exposed in single-stranded regions of the rRNA. Nonmethylatable rRNA species served as competitive inhibitors, whereas the polyanions deoxyribonucleic acid, transfer RNA, and polyadenylic acid were inactive. Micrococcus lysodeikticus and Bacillus subtilis rRNA, methylated by the methylase, each contained two distinct heptanucleotides containing newly synthesized 6-methyladenine moieties. The data are consistent with the view that E. coli strain B possesses two species of rRNA-adenine (N6-) methylases, each of which recognizes a specific adenine moiety in a unique pentapurine nucleotide sequence in a single-stranded region of rRNA.
Iontophoresis was used to enhance the delivery of aceclofenac (ACF) from topical gels formulated with various polymers for the purpose of relieving pain and inflammation.
Materials and Methods
Gels were formulated from hydroxypropyl methyl cellulose (HPMC), carbopol 934P, and sodium carboxymethyl cellulose (NaCMC). The formulations were evaluated for cathodal iontophoretic delivery of ACF through excised rat abdominal skin at three levels of current density of 0.5, 0.6 and 0.7 mA/cm2. The in vivo effectiveness of the drug delivered passively as well as under the influence of iontophoresis at pH 7.4 at a current density of 0.5 mA/cm2 was also investigated using male Albino rats with carrageenan induced paw edema.
Results and Discussion:
In the ex vivo studies, though it was clear that iontophoresis significantly increased drug permeation through the excised skin from all formulations; the percentage drug permeated from HPMC gels was superior to that from carbopol 934P or NaCMC gels but increased with an increase in the current density only for the former. The steady state flux, permeability coefficient, enhancement factor were significantly greater from HPMC gels than from the gels of the ionic polymers due to the interference of competitive ions. With iontophoresis, the carrageenan induced paw edema was significantly reduced by 61.53% (P < 0.01) for HPMC gels as compared to the control although passive permeation without iontophoresis showed a 54.6% reduction (P < 0.05) at the end of 4 h.
The results of the study indicate that ACF could be administered topically by using iontophoresis from a suitably formulated gel for effective control of pain and inflammation.
Aceclofenac; drug permeation; gels; iontophoresis
The effects of groundwater and surface water constituents (i.e., natural organic matter [NOM] and the presence of a complex assortment of ions) on graphene oxide nanoparticles (GONPs) were investigated to provide additional insight into the factors contributing to fate and the mechanisms involved in their transport in soil, groundwater, and surface water environments. The stability and transport of GONPs was investigated using dynamic light scattering, electrokinetic characterization, and packed bed column experiments. Stability results showed that the hydrodynamic diameter of the GONPs at a similar ionic strength (2.1±1.1 mM) was 10 times greater in groundwater environments compared with surface water and NaCl and MgCl2 suspensions. Transport results confirmed that in groundwater, GONPs are less stable and are more likely to be removed during transport in porous media. In surface water and MgCl2 and NaCl suspensions, the relative recovery was 94%±3% indicating that GONPs will be very mobile in surface waters. Additional experiments were carried out in monovalent (KCl) and divalent (CaCl2) salts across an environmentally relevant concentration range (0.1–10 mg/L) of NOM using Suwannee River humic acid. Overall, the transport and stability of GONPs was increased in the presence of NOM. This study confirms that planar “carbonaceous-oxide” materials follow traditional theory for stability and transport, both due to their response to ionic strength, valence, and NOM presence and is the first to look at GONP transport across a wide range of representative conditions found in surface and groundwater environments.
artificial groundwater; artificial surface water; graphene oxide nanoparticles; natural organic matter; solution chemistry; stability; Suwannee River humic acid; transport in porous media
1. The effect of eight salts, NaCl, Na2SO4, Na4Fe(CN)6, CaCl2, LaCl3, ThCl4, and basic and acid fuchsin on the cataphoretic P.D. between solid particles and aqueous solutions was measured near the point of neutrality of water (pH 5.8). It was found that without the addition of electrolyte the cataphoretic P.D. between particles and water is very minute near the point of neutrality (pH 5.8), often less than 10 millivolts, if care is taken that the solutions are free from impurities. Particles which in the absence of salts have a positive charge in water near the point of neutrality (pH 5.8) are termed positive colloids and particles which have a negative charge under these conditions are termed negative colloids. 2. If care is taken that the addition of the salt does not change the hydrogen ion concentration of the solution (which in these experiments was generally pH 5.8) it can be said in general, that as long as the concentration of salts is not too high, the anions of the salt have the tendency to make the particles more negative (or less positive) and that cations have the opposite effect; and that both effects increase with the increasing valency of the ions. As soon as a maximal P.D. is reached, which varies for each salt and for each type of particles, a further addition of salt depresses the P.D. again. Aside from this general tendency the effects of salts on the P.D. are typically different for positive and negative colloids. 3. Negative colloids (collodion, mastic, Acheson's graphite, gold, and metal proteinates) are rendered more negative by low concentrations of salts with monovalent cation (e.g. Na) the higher the valency of the anion, though the difference in the maximal P.D. is slight for the monovalent Cl and the tetravalent Fe(CN)6 ions. Low concentrations of CaCl2 also make negative colloids more negative but the maximal P.D. is less than for NaCl; even LaCl3 increases the P.D. of negative particles slightly in low concentrations. ThCl4 and basic fuchsin, however, seem to make the negative particles positive even in very low concentrations. 4. Positive colloids (ferric hydroxide, calcium oxalate, casein chloride—the latter at pH 4.0) are practically not affected by NaCl, are rendered slightly negative by high concentrations of Na2SO4, and are rendered more negative by Na4Fe(CN)6 and acid dyes. Low concentrations of CaCl2 and LaCl3 increase the positive charge of the particles until a maximum is reached after which the addition of more salt depresses the P.D. again. 5. It is shown that alkalies (NaOH) act on the cataphoretic P.D. of both negative and positive particles as Na4Fe(CN)6 does at the point of neutrality. 6. Low concentrations of HCl raise the cataphoretic P.D. of particles of collodion, mastic, graphite, and gold until a maximum is reached, after which the P.D. is depressed by a further increase in the concentration of the acid. No reversal in the sign of charge of the particle occurs in the case of collodion, while if a reversal occurs in the case of mastic, gold, and graphite, the P.D. is never more than a few millivolts. When HCl changes the chemical nature of the colloid, e.g. when HCl is added to particles of amphoteric electrolytes like sodium gelatinate, a marked reversal will occur, on account of the transformation of the metal proteinate into a protein-acid salt. 7. A real reversal in the sign of charge of positive particles occurs, however, at neutrality if Na4Fe(CN)6 or an acid dye is added; and in the case of negative colloids when low concentrations of basic dyes or minute traces of ThCl4 are added. 8. Flocculation of the suspensions by salts occurs when the cataphoretic P.D. reaches a critical value which is about 14 millivolts for particles of graphite, gold, or mastic or denatured egg albumin; while for collodion particles it was about 16 millivolts. A critical P.D. of about 15 millivolts was also observed by Northrop and De Kruif for the flocculation of certain bacteria.
1. The effects of morganic ions, electrolyte concentration, and pH on the appearance and volume of the isolated rat liver nucleus have been studied. Nuclei were isolated by differential centrifugation in a buffered salt-sucrose mixture at pH 7.1. Nuclear volumes were determined photographically. 2. In solutions of NaCl, of KCl, and in potassium phosphate buffers the nuclear volume decreased markedly with an increase in concentration from 0.001 M to 0.05 M but remained essentially constant with further increase in concentration to 1.0 M. The effects of CaCl2 and MgCl2 differed from those of NaCl and KCl in that a smaller volume was obtained in concentrations less than 0.15 M, and in the case of CaCl2 an increase in volume was obtained in more concentrated solutions. The volume changes are considered to be due primarily to ionic effects on the nuclear colloids rather than to osmotic behavior. 3. Treatment of nuclei with DNAase prevented the characteristic volume changes resulting from ion effects, suggesting the importance of DNA in nuclear volume changes. 4. The optical changes in isolated nuclei in various concentrations of KCl, NaCl, CaCl2, MgCl2, and in potassium phosphate buffers as observed under phase contrast illumination are described. CaCl2 gave the most marked nuclear changes from the conditions in the uninjured cell and caused shrinkage and granulation in 0.001 M concentration. The effects of CaCl2 were also manifested in 0.88 M sucrose, in mixtures with monovalent salts, and in serum. Changes in nuclear volume and optical appearance which occurred in salt solutions and in 0.1 N HCl were readily reversible. 5. Nuclear volume remained constant between pH 8.91 and 5.12 and decreased in more acid solutions. 6. Sucrose had no appreciable osmotic effect, and in hyperosmotic solution. (0.88 M) nuclei showed swelling and rupture comparable to that in distilled water. 7. The results are considered in relation to the requirements of nuclear isolation media. 8. Rat liver nuclei isolated in a buffered salt-sucrose medium by differential centrifugation exhibited a pattern of size distribution similar to that of fixed nuclei but were of considerably larger volume. The ratio of the volumes of the peak frequencies of the two chief size groups was 1:1.9.
1. It has been shown in previous publications that when solutions of different concentrations of salts are separated by collodion-gelatin membranes from water, electrical forces participate in addition to osmotic forces in the transport of water from the side of the water to that of the solution. When the hydrogen ion concentration of the salt solution and of the water on the other side of the membrane is the same and if both are on the acid side of the isoelectric point of gelatin (e.g. pH 3.0), the electrical transport of water increases with the valency of the cation and inversely with the valency of the anion of the salt in solution. Moreover, the electrical transport of water increases at first with increasing concentration of the solution until a maximum is reached at a concentration of about M/32, when upon further increase of the concentration of the salt solution the transport diminishes until a concentration of about M/4 is reached, when a second rise begins, which is exclusively or preeminently the expression of osmotic forces and therefore needs no further discussion. 2. It is shown that the increase in the height of the transport curves with increase in the valency of the cation and inversely with the increase in the valency of the anion is due to the influence of the salt on the P.D. (E) across the membrane, the positive charge of the solution increasing in the same way with the valency of the ions mentioned. This effect on the P.D. increases with increasing concentration of the solution and is partly, if not essentially, the result of diffusion potentials. 3. The drop in the transport curves is, however, due to the influence of the salts on the P.D. (ε) between the liquid inside the pores of the gelatin membrane and the gelatin walls of the pores. According to the Donnan equilibrium the liquid inside the pores must be negatively charged at pH 3.0 and this charge is diminished the higher the concentration of the salt. Since the electrical transport is in proportion to the product of E x ε and since the augmenting action of the salt on E begins at lower concentrations than the depressing action on ε, it follows that the electrical transport of water must at first rise with increasing concentration of the salt and then drop. 4. If the Donnan equilibrium is the sole cause for the P.D. (ε) between solid gelatin and watery solution the transport of water through collodion-gelatin membranes from water to salt solution should be determined purely by osmotic forces when water, gelatin, and salt solution have the hydrogen ion concentration of the isoelectric point of gelatin (pH = 4.7). It is shown that this is practically the case when solutions of LiCl, NaCl, KCl, MgCl2, CaCl2, BaCl2, Na2SO4, MgSO4 are separated by collodion-gelatin membranes from water; that, however, when the salt has a trivalent (or tetravalent?) cation or a tetravalent anion a P.D. between solid isoelectric gelatin and water is produced in which the wall assumes the sign of charge of the polyvalent ion. 5. It is suggested that the salts with trivalent cation, e.g. Ce(NO3)3, form loose compounds with isoelectric gelatin which dissociate electrolytically into positively charged complex gelatin-Ce ions and negatively charged NO3 ions, and that the salts of Na4Fe(CN)6 form loose compounds with isoelectric gelatin which dissociate electrolytically into negatively charged complex gelatin-Fe(CN)6 ions and positively charged Na ions. The Donnan equilibrium resulting from this ionization would in that case be the cause of the charge of the membrane.
This study investigated the possibility of simultaneously extracting glucose and lactate from human subjects, at the same skin location, using transdermal reverse iontophoresis. Transdermal monitoring using iontophoresis is made possible by the skin’s permeability to small molecules and the nanoporous and microporous nature of the structure of skin. The study was intended to provide information which could be used to develop a full, biosensor-based, monitoring system for multiple parameters from transdermal extraction. As a precursor to the human study, in vitro reverse iontophoresis experiments were performed in an artificial skin system to establish the optimum current waveforms to be applied during iontophoresis. In the human study, a bipolar DC current waveform (with reversal of the electrode current direction every 15 minutes) was applied to ten healthy volunteers via skin electrodes and utilized for simultaneous glucose and lactate transdermal extraction at an applied current density of 300 μA/cm2. Glucose and lactate were successfully extracted through each subject’s skin into the conducting gel that formed part of each iontophoresis electrode. The results suggest that it will be possible to noninvasively and simultaneously monitor glucose and lactate levels in patients using this approach and this could have future applications in diagnostic monitoring for a variety of medical conditions.
transdermal; iontophoresis; glucose; lactate; diagnostic monitoring
A study was undertaken to investigate the factors involved in the adhesion of Pseudomonas fluorescens to model meat surfaces (tendon slices). Adhesion was fast (less than 2.5 min) and was not suppressed by killing the cells with UV, gamma rays, or heat, indicating that physiological activity was not required. In various salt solutions (NaCl, KCl, CaCl2, MgCl2), adhesion increased with increasing ionic strength up to 10 to 100 mM, suggesting that, at low ionic strengths, electrostatic interactions were involved in the adhesion process. At higher ionic strengths (greater than 10 to 100 mM) or in the presence of Al3+ ions, adhesion was sharply reduced. Selectively blocking of carboxyl or amino groups at the cell surface by chemical means did not affect adhesion. These groups are therefore not directly involved in an adhesive bond with tendon. Given a sufficient cell concentration (10(10) CFU.ml-1) in the adhesion medium, the surface of tendon was almost entirely covered with adherent bacteria. This suggests that if the adhesion is specific, the attachment sites on the tendon surface must be located within collagen or proteoglycan molecules.
The effects of changes in electrolyte concentration on muscles which had been preserved in 50 per cent glycerol or washed in water were studied. The psoas preparation of Szent-Györgyi was generally used, but smooth and cardiac muscle gave the same results. If the preparations are immersed in 0.16 molar NaCl or KCl and if the electrolyte subsequently is washed out with distilled water, tension rises. This effect is not obtained if solutions of CaCl2 or MgCl2 are used, but it is restored by brief immersion in NaCl or KCl solutions. Changes in pH have no effect. It is concluded that divalent cations are bound more firmly than monovalent ions, but that divalent exchange with monovalent ions. After the application of ATP washing out electrolytes produces a much larger and more rapid rise in tension. This effect persists after ATP has been washed out and seems to be due to the removal of a substance which diminishes the dissociation of bound cations. Washing out electrolytes also causes a large increase in transparency and swelling. These effects are also enhanced by previous application of ATP and are abolished or diminished by divalent cations. The rise in tension and the swelling are explained as the result of an increase in the charge of the polar groups of the proteins. Because this mechanism produces only a small degree of shortening, it does not explain normal contraction, but it may be a part of this process. The significance of the phenomena described in relation to recent theories of the mechanism of muscular contraction is discussed. The observations show that increase in the charge of the contractile proteins causes contraction, not relaxation, as has been commonly assumed.
Iontophoretic mediated transdermal delivery of ferric pyrophosphate (FPP) in combination with microneedle pretreatment was investigated as a potential treatment for iron deficiency anemia (IDA).
In vitro transdermal delivery studies were performed using hairless rat skin and pharmacodynamic studies were performed in hairless anemic rat model. The hematological and biochemical parameters like hemoglobin, hematocrit and % serum transferrin were monitored in rats at healthy, anemic condition and post treatment. Micropores created by the microneedles were visualized in histological skin sections after staining with hemotoxylin and eosin. The recovery of micropores was investigated in vivo by measuring Transepidermal water loss (TEWL) at different time points.
The passive, microneedle and iontophoresis mediated delivery did not lead to significant improvement in hematological and biochemical parameters in anemic rats, when used individually. When iontophoresis (0.15 mA/cm2 for 4 hours) was combined with microneedle pretreatment (for 2 minutes), therapeutically adequate amount of FPP was delivered and there was significant recovery of rats from IDA.
Microneedle and iontophoresis mediated delivery of iron via transdermal route could be developed as a potential treatment for IDA. The transdermal controlled delivery of iron could become a potential, safe and effective alternative to parenteral iron therapy.
Iron deficiency anemia; ferric pyrophosphate; iontophoresis; microneedle; hematology; oxidative stress; noninvasive
The objective of this study was to investigate the effects of pH and ionic strength on electroosmotic transport in transungual iontophoresis. Transungual iontophoretic transport of model neutral permeants mannitol (MA) and urea (UR) across fully hydrated human nail plates in phosphate-buffered saline of different pH and ionic strengths were investigated in vitro. Two protocols were involved in the transport experiments with each protocol divided into stages including passive and iontophoresis transport at 0.1 and/or 0.3 mA. Nail plate electrical resistance and water uptake of nail clippings were measured at various pH and ionic strengths. In the pH study, electroosmosis enhanced the anodal transport of MA at pH 9 and cathodal transport at pH 3. The Peclet numbers of MA were more than two times higher than those of UR under these conditions. No significant electroosmosis enhancement was observed for MA and UR at pH 5. In the ionic strength study, a decrease in solution ionic strength from 0.7 to 0.04 M enhanced electroosmotic transport. Nail electrical resistance increased with decreasing the ionic strength of the equilibrating solution, but reached a plateau when the ionic strength was less than approximately 0.07 M. Solution pH and ionic strength had no significant effect on nail hydration. Under the studied pH and ionic strength conditions, the effects of electroosmosis were small compared to the direct-field effects in transungual iontophoretic transport of small to moderate size permeants.
transungual; iontophoresis; human nail plate; electroosmosis