Ajay K. Banga

Iontophoresis and electroporation: comparisons and contrasts

The techniques of iontophoresis and electroporation can be used to enhance topical and transdermal drug delivery. Iontophoresis applies a small low voltage (typically 10 V or less) continuous constant current (typically 0.5 mA/cm2 or less) to push a charged drug into skin or other tissue. In contrast, electroporation applies a high voltage (typically, ?100 V) pulse for a very short (micros-ms) duration to permeabilize the skin. This electric assistance of drug delivery across skin will expand the scope of transdermal delivery to hydrophilic macromolecules such as the drugs of biotechnology. These two techniques differ in several aspects such as the mode of application and pathways of transport but can be used together for effective drug delivery. Iontophoresis is already used clinically in physical therapy clinics and is close to commercialization for development of a systemic delivery patch with miniaturized circuits and similar in overall size to a passive patch. The use of electroporation for drug delivery is relatively new and is being actively researched.

In vitro transdermal delivery of therapeutic antibodies using maltose microneedles.

This paper investigates the microneedle-mediated in vitro transdermal delivery of human IgG as a model protein and demonstrates its applicability to deliver a monoclonal antibody. Microchannels created by the treatment of maltose microneedles in full thickness hairless rat skin were visualized using methylene blue staining. Cryostat sections were prepared and stained using hematoxylin and eosin to locate the depth of penetration. In vitro penetration studies were conducted using freshly excised full thickness hairless rat skin and various parameters like needle length, number of needles and effect of donor concentration were examined. Pathway of IgG transport across skin was confirmed by immunohistochemical (IHC) studies. A monoclonal antibody was delivered under optimized conditions. Methylene blue was taken up by microchannels indicating disruption of the stratum corneum and cryosections showed that microneedles just reached the dermis. Human IgG delivery increased with increase in arrays of microneedles, concentration and length of microneedles. IHC studies demonstrated that IgG follows microchannels for transport across the skin. Transdermal delivery was also demonstrated for the monoclonal antibody. In conclusion, maltose microneedles provide a means for the transdermal delivery of macromolecules.

Microporation applications for enhancing drug delivery

Microporation involves the creation of micron-sized micropores or microchannels in the skin which can then allow the transport of water soluble molecules and macromolecules. Technologies which can create these microchannels in the skin include mechanical microneedles, thermal or radiofrequency ablation and laser ablation. These technologies will open a new frontier for the delivery of biopharmaceuticals, as these hydrophilic macromolecules cannot be delivered via the skin passively. Companies which are developing these technologies are discussed, along with potential hurdles to commercialization related to the elasticity of skin, immunogenicity issues, pore closure kinetics, or microneedle material and geometries. In spite of the obstacles, these technologies look very promising and are likely to revolutionize transdermal drug delivery in the near future. Bioavailability considerations and the potential use of inexpensive coated microneedles for mass immunizations are also discussed.

The effect of electroporation on iontophoretic transdermal delivery of calcium regulating hormones

Electrically-assisted delivery by iontophoresis and/or electroporation was used in vitro to deliver the calcium regulating hormones, salmon calcitonin (sCT) and parathyroid hormone (1-34) (PTH) through human epidermis. Such delivery could be useful for chronic treatment of post-menopausal osteoporosis and other clinical indications as a superior alternative to parenteral delivery. sCT (50 microg/ml) or PTH (1-34) (100 microg/ml) formulation was prepared in citrate buffer (pH 4.0 or 5.0, respectively). Epidermis separated from human cadaver skin was used. Iontophoresis was applied using a constant current power source and electroporation with an exponential pulse generator. Silver/silver chloride electrodes were used. A combination of electroporation and iontophoresis resulted in higher transdermal permeation than either one technique alone. Electroporation also shortened the lag time of iontophoretic transdermal delivery of salmon calcitonin. Pulsing at lower voltages followed by iontophoresis did not result in increased transport (over iontophoresis alone), perhaps because the transdermal voltage was very low. The transdermal transport of salmon calcitonin by pulsing with 15 pulses (1 ppm) of 500 V (200 ms) followed by iontophoresis led to a quick input and high flux. The average transdermal voltage was only about 50 V for a 500 V study.

Effects of disintegration-promoting agent, lubricants and moisture treatment on optimized fast disintegrating tablets

Effects of calcium silicate (disintegration-promoting agent) and various lubricants on an optimized beta-cyclodextrin-based fast-disintegrating tablet formulation were investigated. Effects of moisture treatment were also evaluated at 75, 85 and 95% relative humidities. A two factor, three levels (3(2)) full factorial design was used to optimize concentrations of calcium silicate and lubricant. Magnesium stearate, being commonly used lubricant, was used to optimize lubricant concentration in optimization study. Other lubricants were evaluated at an obtained optimum concentration. Desiccator with saturated salt solutions was used to analyze effects of moisture treatments. Results of multiple linear regression analysis revealed that concentration of calcium silicate had no effect; however concentration of lubricant was found to be important for tablet disintegration and hardness. An optimized value of 1.5% of magnesium stearate gave disintegration time of 23.4 s and hardness of 1.42 kg. At an optimized concentration, glycerol dibehenate and L-leucine significantly affected disintegration time, while talc and stearic acid had no significant effect. Tablet hardness was significantly affected with L-leucine, while other lubricants had no significant effect. Hardness was not affected at 75% moisture treatment. Moisture treatment at 85 and 95% increased hardness of the tablets; however at the same time it negatively affected the disintegration time.

Transdermal Delivery of Proteins

Transdermal delivery of peptides and proteins avoids the disadvantages associated with the invasive parenteral route of administration and other alternative routes such as the pulmonary and nasal routes. Since proteins have a large size and are hydrophilic in nature, they cannot permeate passively across the skin due to the stratum corneum which allows the transport of only small lipophilic drug molecules. Enhancement techniques such as chemical enhancers, iontophoresis, microneedles, electroporation, sonophoresis, thermal ablation, laser ablation, radiofrequency ablation and noninvasive jet injectors aid in the delivery of proteins by overcoming the skin barrier in different ways. In this review, these enhancement techniques that can enable the transdermal delivery of proteins are discussed, including a discussion of mechanisms, sterility requirements, and commercial development of products. Combination of enhancement techniques may result in a synergistic effect allowing increased protein delivery and these are also discussed.

Synergistic effect of iontophoresis and soluble microneedles for transdermal delivery of methotrexate

The aim of this study was to investigate the transdermal iontophoretic delivery of methotrexate, alone or in combination with microneedles, in‐vitro and in‐vivo using intracutaneous microdialysis in the hairless rat. The average depth of the microdialysis probe in the skin was found to be 0.54 mm. Methotrexate was stable in the presence of an applied electric field as determined by cyclic voltammetry. A current density of 0.4 mA cm−2 applied for 60 min was used in combination with maltose microneedles to enhance delivery of methotrexate across the skin. Delivery was enhanced by iontophoresis and microneedles, both in‐vitro and in‐vivo. A synergistic 25‐fold enhancement of delivery was observed in‐vivo when a combination of microneedles and iontophoresis was used compared with either modality alone.

Direct quantitation of active ingredients in solid artesunate antimalarials by noncovalent complex forming reactive desorption electrospray ionization mass spectrometry

The direct quantitation of active ingredients in solid pharmaceutical tablets by desorption electrospray ionization mass spectrometry (DESI MS) is complicated by the dependence of the DESI signal on variables such as spray angles and distances, morphological sample properties, and the difficulty of properly incorporating an internal standard. Here, a DESI MS method for the direct quantitative screening of widely counterfeited antimalarial tablets containing artesunate is presented. This method is based on reactive DESI, where analyte desorption and ionization occur by the formation of noncovalent complexes between alkylamine molecules in the DESI spray solution and artesunate molecules exposed on the sample surface in the open air. For quantitation purposes, the internal standard d4-artesunic acid was synthesized by esterification of d4-succinic anhydride and dihydroartemisinin, and homogeneously dispersed on the tablet surface via a controlled deposition procedure. The analyte-to-internal standard signal intensity ratio was observed to be largely independent of all DESI variables, only showing dependence on tablet hardness. Analysis of artesunate tablet standards prepared with known amounts of the active ingredient in the 0.02 to 0.32 mg artesunate mg−1 tablet range resulted in a calibration curve with good linearity (r = 0.9985). Application of this method to the direct quantitation of genuine artesunate tablets from Vietnam showed a 6% (n = 4) precision and 94% accuracy after the spectral data were corrected for tablet hardness.

Enhanced transdermal delivery of low molecular weight heparin by barrier perturbation.

The purpose of this work was to investigate the in vitro transdermal delivery of low molecular weight heparin (LMWH). Hairless rat skin was mounted on Franz diffusion cells and treated with various enhancement strategies. Passive flux was essentially zero and remained low even after iontophoresis (0.065 U cm(-2) h(-1)) or application of ultrasound (0.058 U cm(-2) h(-1)). A significant increase in flux across tape stripped skin (4.0 U cm(-2) h(-1)) suggests the interaction of stratum corneum (SC) with LMWH which was confirmed using Differential Scanning Calorimetry and Fourier Transform-Infrared spectrophotometry. Maltose microneedles were then employed as a means to locally disrupt and bypass the SC. Transepidermal water loss (TEWL) and transcutaneous electrical resistance (TER) were measured to confirm the barrier disruption. Microneedles breached the SC resulting in increased TEWL, decreased TER and enhanced LMWH permeability (0.175 U cm(-2) h(-1)). Microneedles when used in conjunction with iontophoresis had a synergistic effect on LMWH delivery resulting in enhancement of flux by 14.7-fold as compared to iontophoresis used alone. Confocal laser scanning microscopy substantiated the evidence about LMWH interaction with SC. In conclusion, LMWH was shown to interact with SC and therefore tape stripping or microneedles dramatically increased its delivery due to disruption of the SC skin barrier.

Transdermal iontophoretic delivery of salmon calcitonin

Electrically enhanced transdermal delivery of salmon calcitonin could be useful for chronic treatment of postmenopausal osteoporosis and other clinical indications as a superior alternative to parenteral delivery. Calcitonin (50 microg/ml) formulation was prepared in citrate buffer (pH 4.0). Epidermis separated from human cadaver skin was used. Most iontophoresis studies were done at a current density of 0.5 m A cm2. Silver/silver-chloride electrodes were used and calcitonin was found to be best delivered under the anode. The relationship between calcitonin flux and current density during iontophoresis was linear. Passive flux was zero. Flux increased with increasing concentration up to 250 microg/ml but then it levels off. Thus, transdermal delivery of salmon calcitonin may be accomplished to achieve therapeutic levels.