Electroosmotic flow as a result of buccal iontophoresis - Buccal mucosa properties

The objective of this study was to investigate and to better understand the properties of buccal mucosa as a semipermeable membrane and a portal for drug administration by iontophoretic and electroosmotic means. In vitro experiments showed that buccal mucosa at the pH of about 7.4 behaved as a cation-exchange membrane and non-linear resistor. It had lower resistance and was more permeable for water than a skin. The electroosmotic volume flow through mucosa depended on current density, mucosa resistance and electrolyte concentration. Sodium dodecyl sulfate (in concentration range 0.001-0.005 mol L⁻¹) and urea (in concentration range 0.42-1.67 mol L⁻¹) did not promote a water transfer through buccal mucosa, however, both substances enhanced flow through the skin.     

Effect of formulation factors on the trans-scleral iontophoretic and post-iontophoretic transports of a 40 kDa dextran in vitro

The aim of the work was to study in vitro, across isolated porcine sclera and across the trilayer sclera–choroid–Bruch's membrane (SCB), the effect of iontophoresis on the permeation of a 40 kDa dextran (FD-40), chosen as model compound of high molecular weight neutral drugs.In particular, the effect of vehicle composition (in terms of buffering agent and ionic strength) and current intensity (from 0.3 to 4.2 mA, corresponding to 0.5–7 mA cm^?2) was investigated. Additionally the post-iontophoretic transport of FD-40 through SCB was studied.The results obtained in the present paper confirm the importance of formulation parameters during transscleral iontophoresis of a neutral high molecular weight hydrophilic compound transported by electroosmosis. In particular, ionic strength seems to be the more relevant parameter, while the buffering agent (phosphate vs HEPES) is not relevant. The enhancement obtained increases – although in a stepwise way – with current intensity, after a threshold value of approximately 1.5 mA. However, the real variable to be considered is probably current density (threshold value 2.5 mA cm^?2) more than intensity, in analogy with transdermal iontophoresis. The inclusion of further static barriers besides the sclera, such as choroid and Bruch's membrane, reduces, as expected, the permeation of FD-40, but iontophoresis is able to significantly promote FD-40 transport also through this more complex barrier, without altering its permeability. Finally, the study of the post-iontophoretic transport highlights the formation of a pronounced FD-40 reservoir inside the sclera. This reservoir permits to obtain in vitro a sustained transscleral flux up to 3 h after current stop. This result could be of interest in the case of a real application, prolonging the enhancement effect also after iontophoresis stop.     

Relevance of polymer molecular weight to the in vitro/in vivo performances of ocular inserts based on poly(ethylene oxide)

A previous study of the present authors on gel-forming erodible inserts, based on high molecular weight (MW, 400 kDa) poly(ethylene oxide) (PEO), for ocular controlled delivery of ofloxacin (OFX) has been extended to investigate the effects of PEO MW, in the 200–2000 kDa range, on insert properties relevant to therapeutic efficacy. Mucoadhesion has shown a dependence on MW, with a maximum for PEO 400. The in vitro drug release from inserts based on PEO 200, PEO 400 and PEO 900 was mainly controlled by insert erosion, whereas with PEO 2000 it was mainly diffusion-controlled in a first phase, followed by an erosion-controlled phase. The erosion time scale depended directly on MW. Immediately after application in the lower conjunctival sac of the rabbit eye, the inserts based on PEO of whichever MW formed mucoadhesive gels, well tolerated by the animals; then the gels spread over the corneal surface and eroded. PEO 2000 was unsuitable as an insert material, since the resulting gel spilled from the eye, due to excessive swelling. The gel residence time in the precorneal area, the drug permanence time in the aqueous humor at concentrations >MIC and the time to reach the maximal drug concentration in the aqueous humor (C_max) depended directly on MW, indicating that transcorneal absorption was governed by gel erosion. All inserts increased C_max and AUC_eff (AUC for concentrations >MIC) with respect to the commercial eyedrops. The increases caused by PEO 400 and PEO 900 were similar (3.78- and 3.16-fold, respectively, for C_max; 11.06- and 12.37-fold, respectively, for AUC_eff), whereas smaller increases were produced by PEO 200. The PEO 400 and PEO 900 inserts have shown a potential for a topical treatment of endophthalmitis.     

Diagnostic and therapeutic applications of iontophoresis

Owing to the excellent barrier properties of the stratum corneum, transdermal delivery remains a challenge for a high number of molecules. Iontophoresis is a noninvasive technique which uses a low current to administer polar and charged species through the skin, thereby enlarging the range of drug candidates for transdermal administration. Unlike other techniques of transdermal delivery enhancement, iontophoresis acts on the molecule itself allowing a better control of the dose applied. The symmetry of the technique can be employed for controlled extraction, allowing a relation to be established between extracted flux and subdermal concentration. This opened the way for innovative applications, notably in the field of noninvasive monitoring of glucose and xenobiotics. Rather than being an extensive review of the literature, this article summarizes the basic rules governing iontophoretic transport, discusses advantages and limitations of the technique, and provides an overview of promising therapeutic applications.     

Transdermal iontophoresis of ranitidine: an opportunity in paediatric drug therapy

The objective of this study was to examine the use of transdermal iontophoresis for the delivery of ranitidine hydrochloride in children. Constant, direct current, anodal iontophoresis of ranitidine was performed in vitro across dermatomed pig skin. The effect of donor vehicle, current intensity, and drug concentration were first examined using aqueous solutions. It was found that drug delivery was higher at pH 7 (donor: 5 mM Tris) than pH 5.6 (donor: water). In the presence of low levels of competing background electrolyte, ranitidine delivery increased linearly with applied current but was independent of the donor drug concentration. The second part of the study evaluated two Pluronic^® F-127 gels as potential vehicles for ranitidine delivery. The formulations were characterised in terms of apparent viscosity, conductivity and passive permeation measurements. Iontophoretic delivery of ranitidine was only slightly affected when delivered from the gels relative to aqueous solutions. Overall the results demonstrated that therapeutic paediatric doses of ranitidine (neonates: 0.09–0.17 μmol/kg h; 1 month to 12 years: 0.36–0.71 μmol/kg h) could be easily achieved by transdermal iontophoresis with simple gel patches of practical surface area (0.2–1.5 cm²/kg).     

Amikacin reverse iontophoresis: Optimization of in vitro extraction

The aim of this work was to optimize amikacin reverse iontophoretic extraction across the skin in vitro, for non-invasive drug monitoring. Reverse iontophoresis experiments were performed using vertical diffusion cells. The lower chamber, simulating body fluids, contained amikacin bisulphate and acetaminophen, as marker for electroosmosis, while the upper chamber was filled with the appropriate extraction solution. The effect of concentration of amikacin in the dermal bathing solution and the effect of extraction solution composition and pH were studied.     

Effect of iontophoresis on in vitro transdermal absorption of almotriptan

The aim of the present work was to characterize the in vitro transdermal absorption of almotriptan through pig ear skin. The passive diffusion of almotriptan malate and its iontophoretic transport were investigated using current densities of 0.25 and 0.50 mA/cm². In vitro iontophoresis experiments were conducted on diffusion cells with an agar bridge without background electrolytes in the donor compartment. Although both current densities applied produced a statistically significant increment with respect to passive permeation of almotriptan (p < 0.01), that of 0.50 mA/cm² proved to be the best experimental condition for increasing the transport of almotriptan across the skin. Under these experimental conditions, the transdermal flux of the drug increased 411-fold with respect to passive diffusion, reaching 264 ± 24 μg/cm² h (mean ± SD). Based on these results, and taking into account the pharmacokinetics of almotriptan, therapeutic drug plasma levels for the management of migraine could be achieved via transdermal iontophoresis using a reasonably sized (around 7.2 cm²) patch.     

Effect of iontophoresis and fatty acids on permeation of Arginine Vasopressin through rat skin

The aim of this study was to assess the effects of fatty acids and iontophoretic mode of penetration enhancement on transdermal delivery of Arginine Vasopressin (AVP). Sprague-Dawley (SD) rat skin was pretreated with fatty acids (e.g. 5% w/v, lauric acid, oleic acid, and linoleic acid in ethanol:water (EtOH:W, 2:1 system) for 2h and iontophoresis in vitro, separately or together. The results indicate that all fatty acids studied increased (P<0.05) the flux of AVP in comparison to control (not pretreated with enhancer) and their effectiveness in flux enhancement was comparable. Further, oleic acid in combination with iontophoresis significantly increased the permeation of AVP both in comparison to pretreatment with fatty acids and iontophoresis alone. However, iontophoresis did not further increase the permeation of AVP through linoleic acid pretreated skin. Fourier transform infrared (FT-IR) spectroscopic studies revealed that EtOH:W (2:1) system is not effective in lipid extraction. The shift to higher wavenumbers of the symmetric and asymmetric stretching peaks at 2850 and 2920cm(-1) revealed that at the concentration used, oleic acid and linoleic acid caused fluidization of stratum corneum (SC) lipids. This study provides direct evidence that oleic acid in EtOH:W (2:1) system causes disruption of the SC lipid lamellae and that a combination of oleic acid with iontophoresis further enhances the effects of oleic acid in a synergistic manner.     

Transdermal iontophoresis of 5-fluorouracil combined with electroporation and laser treatment

The influence of iontophoresis and other physical enhancement methods such as electroporation and erbium:yttrium-aluminum-garnet (YAG) laser on the skin permeation of 5-fluorouracil (5-FU) was examined. Iontophoresis increased the in vitro transdermal transport of both the anionic and non-ionic forms of 5-FU. A combination of electroporation pretreatment and subsequent iontophoresis resulted in a higher permeation of 5-FU than either technique alone. It appeared that electroporation treatment exerted a disruptive influence on the stratum corneum (SC). The SC layers in the skin were partly ablated by the laser, resulting in a great enhancement effect on the skin permeation of 5-FU. Application of iontophoresis further increased the drug permeation across laser-pretreated skin. The laser was consistently the most potent technique to enhance 5-FU delivery among the physical enhancement methods examined in this study.     

HPLC法测定眼氨肽注射液中大分子蛋白

目的 建立眼氨肽注射液中大分子蛋白的检测方法,比较不同厂家生产的眼氨肽注射剂中大分子蛋白的质量分数。方法 采用高效液相色谱法测定,TSK-GEL2000SWxl分子排阻色谱柱（300 mm×7.8 mm,5 μm）,以三氟乙酸-乙腈-水（0.1：10：90）为流动相,体积流量为0.6 mL/min,检测波长214 nm,进样体积10 μL。采用面积归一化法计算大分子蛋白的质量分数。结果 不同厂家生产的眼氨肽注射液中的大分子蛋白质量分数普遍较低,在0.020%～0.245%。结论 与原方法20%磺基水杨酸法检测蛋白质比较,本方法的准确度更好,能有效地测定眼氨肽注射液中的大分子蛋白。     

乙肝疫苗体外经大鼠皮肤渗透与离子导入给药特性研究(英文)

对乙肝疫苗进行体外经皮实验以评价疫苗在被动扩散和离子导入情况下的经皮渗透特性。体外透皮研究采用Franz扩散池,以SD大鼠的腹部皮肤为渗透屏障,以酶联免疫法测定药物累积渗透量和在皮肤中的滞留量。乙肝疫苗(质量浓度为23μg·mL-1与46μg·mL-1)经完整皮肤被动扩散的经皮渗透量与皮肤滞留量均极少,24 h累积渗透量仅(2.1±0.1)ng.cm-2和(2.3±0.1)ng.cm-2。去除角质层后,经皮渗透量与皮肤滞留量分别提高至(383.7±86.2)ng.cm-2和(16.8±4.6)ng.cm-2,是完整皮肤的171.6倍与2.1倍(46μg·mL-1)。离子导入对于乙肝疫苗具有明显的经皮渗透促进作用:完整皮肤经皮离子导入6 h,乙肝疫苗的累积渗透量是被动扩散6 h的2.7倍(23μg·mL-1)和6.6倍(46μg·mL-1);去角质层皮肤离子导入,乙肝疫苗的累积渗透量是被动扩散6 h的1.6倍(23μg·mL-1)和1.8倍(46μg·mL-1)。离子导入也能显著增加疫苗在皮肤中的滞留量。离子导入6 h疫苗在完整皮肤中的滞留量和去角质层皮肤中的滞留量均与被动扩散24 h的皮肤滞留量接近[完整皮肤...     

Improved stability and release control of levodopa and metaraminol using ion-exchange fibers and transdermal iontophoresis

Achievement of controlled drug delivery and stability of drugs during storage is a problem also in transdermal drug delivery. The objective of this study was to determine, whether an easily oxidized drug, levodopa, could be stabilized during storage using pH-adjustment and ion-exchange fibers. Controlled transdermal delivery of the zwitterionic levodopa was attempted by iontophoresis and ion-exchange fiber. Ion-exchange kinetics and transdermal permeation of a cationic (presumably more stable) model drug, metaraminol, were compared to the corresponding data of levodopa. Levodopa was rapidly oxidized in the presence of water, especially at basic pH-values. At acidic pH-values the stability was improved significantly. Ion-exchange group and the pH had a clear effect on the release of both the levodopa and metaraminol from the ion-exchange fiber. The adsorption/release kinetics of metaraminol were more easily controllable than the corresponding rate and extent of levodopa adsorption/release. Iontophoretic enhancement of drug permeation across the skin was clearly more significant with the positively charged metaraminol than with the zwitterionic levodopa. Ion-exchange fibers provide a promising alternative to control drug delivery and to store drugs that are degraded easily.     

Liposome coated with low molecular weight chitosan and its potential use in ocular drug delivery

In this study liposome coated with low molecular weight chitosan (LCH) was proposed and investigated its in vitro and in vivo properties, and its potential use in ocular drug delivery was evaluated. LCH with a molecular weight of 8 kDa was prepared and coated on liposome loaded with diclofenac sodium. The LCH coating changed the liposome surface charge and slightly increased its particle size, while the drug encapsulation was not affected. After coating, the liposome displayed a prolonged in vitro drug release profile. LCH coated liposome also demonstrated an improved physicochemical stability at 25 °C in a 30-day storage period. The ocular bioadhesion property was evaluated by rabbit in vivo precorneal retention, and LCH coated liposome achieved a significantly prolonged retention compared with non-coated liposome or drug solution. The LCH coating also displayed a potential penetration enhancing effect for transcorneal delivery of the drug. In the ocular tolerance study, no irritation or toxicity was caused by continual administration of LCH coated liposome in a total period of 7 days. In conclusion, the LCH coating significantly modified the properties of liposome and brought a series of notable advantages for ocular drug delivery.     

离体动物皮肤和人体表皮的被动电学性质

研究和比较了三种无毛实验动物离体皮肤和人体表皮在离子电导中的被动电学性质，发现48小时水合过程显著和连续地降低动物皮肤的阻抗，而人体表皮则保持阻抗相对稳定，但是在各水合时间，在连续升高的脉冲电压与产生的电流之间无论动物皮肤或人体表皮都呈现类似的非线性关系，只是对电压变化的敏感程度不同，其相关方程为：V＝（4ARF／T）Sinh^-1（BI）。式中参数A的大小反映了敏感性的大小，与人体表皮比较，无毛小鼠和无毛豚鼠对电压更为敏感，而无毛大鼠相对不敏感，长时间施加电压得到相同结果，但电阻的显著改变总是发生在电压开始或停止后的短时间内。     

In vitro iontophoretic transport of ketorolac: synthetic membrane as a barrier

The effect of different factors on the iontophoretic transport of ketorolac was analyzed. In vitro experiments were performed in a diffusion cell with a cellulose membrane as a barrier. The results indicated that an increase in current density or drug concentration enhanced the transmembrane permeation of the drug. The presence of extraneous ions (such as NaCl) or an increase in viscosity of the donor medium slowed down the iontophoretic transport of the drug. The pH does not seem to be an important factor determining iontophoretic transport of ketorolac as statistically insignificant difference was observed in flux at pH 5.6, 7.2, and 8. Also, the relative importance of the transport contributions involved in iontophoresis, namely diffusive iontophoretic and electro-osmotic fluxes, was investigated using glucose as a nonionizable drug. The results indicated that the total flux of ketorolac is a result of two contributions: passive diffusion and iontophoretic flux. The contribution of electro-osmosis appears to be negligible.     

In vitro cytotoxic and immunomodulatory profiling of low molecular weight polyethylenimines for pulmonary application

Polyethylenimines (PEI) are potent non-viral nucleic acid delivery vehicles used for gene delivery and RNA interference (RNAi). For non-invasive pulmonary RNAi therapy the respiratory tissue is an attractive application route, but offers particularly unwanted side-effects like cytotoxicity as well as inflammatory and immune responses.In the current study, we determined the most crucial issues of pulmonary applications for two low molecular weight PEIs in comparison to the well-known lung toxic crystalline silica. Cytotoxic effects and inflammatory responses were evaluated in three murine pulmonary target cell lines, the alveolar epithelial (LA4), the alveolar macrophage (MH-S) and the macrophage-monocyte-like (RAW 264.7) cell line.For both PEIs, cytotoxicity was detected most prominently in the alveolar epithelial cells and only at high doses. Cytokine responses, in contrast were observed already at low PEI concentrations and could be divided into three groups, induced (i) by free PEI (IL-6, TNF-α, G-CSF), (ii) by PEI/siRNA complexes (CCL2, -5, CXCL1, -10), or (iii) unaffected by either treatment (IL-2, -4,-7, -9, and CCL3).We conclude that even for the respiratory tissue both PEIs represent powerful siRNA delivery tools with reduced cytotoxicity and minor proinflammatory potency. However, in relation to response levels observed upon crystalline silica exposures, some PEI induced proapoptotic and proinflammatory responses might not be considered completely harmless, therefore further in vivo investigations are advisable.     

Iontophoretic transport kinetics of ketorolac in vitro and in vivo: Demonstrating local enhanced topical drug delivery to muscle

The objective of the study was to investigate the iontophoretic delivery kinetics of ketorolac (KT), a highly potent NSAID and peripherally-acting analgesic that is currently indicated to treat moderate to severe acute pain. It was envisaged that, depending on the amounts delivered, transdermal iontophoretic administration might have two distinct therapeutic applications: (i) more effective and faster local therapy with shorter onset times (e.g. to treat trauma-related pain/inflammation in muscle) or (ii) a non-parenteral, gastrointestinal tract sparing approach for systemic pain relief. The first part of the study investigated the effect of experimental conditions on KT iontophoresis using porcine and human skin in vitro. These results demonstrated that KT electrotransport was linearly dependent on current density – from 0.1875 to 0.5 mA/cm² – (r² > 0.99) and drug concentration – from 5 to 20 mg/ml (r² > 0.99). Iontophoretic permeation of KT from a 2% hydroxymethyl cellulose gel was comparable to that from an aqueous solution with equivalent drug loading (584.59 ± 114.67 and 462.05 ± 66.56 μg/cm², respectively). Cumulative permeation (462.05 ± 66.56 and 416.28 ± 95.71 μg/cm²) and steady state flux (106.72 ± 11.70 and 94.28 ± 15.47 μg/cm² h), across porcine and human skin, were statistically equivalent confirming the validity of the model. Based on the results in vitro, it was decided to focus on topical rather than systemic applications of KT iontophoresis in vivo. Subsequent experiments, in male Wistar rats, investigated the local enhancement of KT delivery to muscle by iontophoresis. Drug biodistribution was assessed in skin, in the biceps femoris muscle beneath the site of iontophoresis (‘treated muscle’; TM), in the contralateral muscle (‘non-treated muscle’; NTM) and in plasma (P). Passive topical delivery and oral administration served as negative and positive controls, respectively. Iontophoretic administration for 30 min was superior to passive topical delivery for 1 h and resulted in statistically significant increases in KT levels in the skin (91.04 ± 15.48 vs. 20.16 ± 8.58 μg/cm²), in the biceps femoris at the treatment site (TM; 6.74 ± 3.80 vs. <LOQ), in the contralateral site (NTM; 1.26 ± 0.54 vs. <LOQ) and in plasma (P; 8.58 ± 2.37 μg/ml vs. <LOD). In addition to increasing bioavailability, iontophoretic administration of KT showed clear selectivity for local delivery to the biceps femoris at the treatment site – the TM:NTM ratio was 5.26 ± 1.45, and the TM:P and NTM:P ratios were 0.75 ± 0.32 and 0.14 ± 0.04, respectively. Furthermore, the post-iontophoretic concentration of KT in the ‘treated’ biceps femoris muscle and the muscle:plasma ratio were also superior to those following oral administration of a 4 mg/kg dose (6.74 ± 3.80 vs. 0.62 ± 0.14 μg/g and 0.75 ± 0.32 vs. 0.14 ± 0.03, respectively). In conclusion, the results demonstrate that iontophoresis of ketorolac enables local enhanced topical delivery to subjacent muscle; this may have clinical application in the treatment of localised inflammation and pain.     

In vitro and in vivo iontophoretic transdermal delivery of an anti-parkinsonian agent

To objective of this work was to study the feasibility of iontophoretic delivery of SLV 318 (7-(4-benzyl-1-piperazinyl)-2(3H)-benzoxazolone methanesulfonate) across hairless rat skin in vitro and in vivo. The effect of counter-ions and temperature were investigated for optimizing SLV 318 solubility. The effect of electrode efficiency and total current applied on the delivery of SLV 318 were studied using Franz diffusion cells and samples were analyzed using HPLC. Delivery increased with increasing concentration. For current-time combinations, electrode had to be replaced every 9 h. Passive, iontophoretic (0.1 mA/cm² for 1 h) and intravenous studies were performed in vivo. Blood samples collected were analyzed using LC-MS/MS. SLV 318 had higher solubility with NaCl (75 mM) as a counter-ion at 25 °C than with other counter-ions tested. In vivo iontophoresis significantly enhanced the permeation and also reduced its lag time (P < 0.05). The C_max of SLV 318 during 1 h iontophoresis was 6.56 ± 0.68 ng/mL at 1.31 ± 0.29 h (T_max) as compared to 2.96 ± 0.29 ng/mL at 25.32 ± 0.67 h (T_max) by 24 h passive permeation. The in vitro and in vivo data has shown the feasibility to enhance delivery of SLV 318 by iontophoresis.     

The role of small molecular weight compounds to increase vacuolation induced by VacA toxin in vitro

VacA is a vacuolation protein toxin secreted by Helicobacter pylori. Many compounds have been implicated in the regulation of VacA toxin activity. In this study, regulation of cell vacuolation induced by VacA was observed with the addition of glycine, glycine hydrochloride, xylitol, and taurine by neutral red dye uptake assay using gastric human epithelial cell cultures. Glycine, xylitol, and taurine increased cell vacuolation significantly after 48 h (p < 0.05), with their effect apparent in a wide concentration range (0.2 mM to about 100 mM). Changes were sharp in respect of concentration and showed little dose–response characteristics. In contrast, upregulation of glycine hydrochloride on cell vacuolation in weak acidic extracellular pH was much retarded with VacA activity not initiated until 72 h. In addition, our results showed that cell vacuolation was highest when the pH was 6.8. The increase in vacuolation was gentle in weak acidic extracellular pH and the increase dose-dependent with a Pearson correlation coefficient (r) of 0.986 from 0.2 to 6.25 mM. In this concentration range and at the same time point, the pH decrease was negatively correlated with vacuolating activity (r = 0.922, p < 0.01). In conclusion, our study showed that three small molecular compounds can increase vacuolation induced by VacA toxin in vitro.     

In vitro degradation and dissolution behaviours of microspheres prepared by three low molecular weight polyesters

The particle morphology and in vitro release of protein from porous and non-porous PCL-F127 blended microparticles were evaluated. The BSA loaded PCL microparticles were prepared by the w/o/o/o emulsion-solvent evaporation method. Two types of homogenizer, a Polytron® homogenizer and a probe ultrasonicator, were used to prepare the emulsion systems. The effects of solvent evaporation rate on the crystallinity and the performance of the microparticles were investigated. Both microparticles showed quite different shapes as well as surface morphology and release characteristics. The microparticles prepared with a Polytron® homogenizer were quite porous in structure, which created channels for protein to continuously diffuse out, and resulted in sustained- and controlled-release characteristics. In addition, the initial burst release of protein from the microparticles was also reduced. Alteration of the evaporation rate of solvent did not change the crystallinity of the final microparticles. An influence of evaporation rate on the size of resulting microparticles was observed. The porous PCL microparticles were developed by choosing a proper homogenizer and fabrication conditions. Carefully controlling these variables resulted in microparticles with desirable release performance.