Biochemical enhancement of transdermal delivery with magainin peptide: modification of electrostatic interactions by changing pH

Development and evaluation of a drug-in-adhesive transdermal delivery system for delivery of olanzapine

OBJECTIVES

Olanzapine (OZP) is a safe and effective atypical antipsychotic drug used in treating schizophrenia and bipolar disorders. The dosage forms currently on the market for OZP are administered via oral or intramuscular routes. However, there are many problems associated with oral and intramuscular routes of drug administration. Thus, our aim was to develop a drug-in-adhesive transdermal delivery system (TDS) that can deliver OZP for 3 days.

METHODS

We determined passive permeation, effect of oleic acid as chemical enhancer, and delivery of OZP across different skin types. Based on preliminary studies and saturation solubility of OZP in different pressure-sensitive adhesives (PSAs), we formulated and characterized solution-based TDS in acrylate PSA and suspension-based TDS in silicone and PIB PSA, with oleic acid as chemical enhancer.

RESULTS

Acrylate solution-based TDS, silicone, and PIB suspension-based TDS delivered 58.97 ± 6.59 µg/sq.cm, 129.34 ± 16.59 µg/sq.cm, and 245.00 ± 2.51 µg/sq.cm, respectively, using in vitro permeation testing. PIB PSA suspension-based TDS met the 3 days desired target delivery. Skin irritation testing using In vitro EpiDerm^TM skin irritation test (EPI-200-SIT) kit found PIB TDS to be nonirritant.

CONCLUSION

The PIB PSA suspension-based TDS could serve as a potentially effective transdermal delivery system for olanzapine.

Nanocellulose-lysozyme colloidal gels via electrostatic complexation

Biohybrid colloids were fabricated based on electrostatic complexation between anionic TEMPO-oxidized cellulose nanofibrils (TO-CNF) and cationic hen egg white lysozyme (HEWL). By altering the loading of HEWL, physical colloidal complexes can be obtained at a relatively low concentration of TO-CNF (0.1 wt%). At neutral pH, increasing the HEWL loading induces an increase in charge screening, as probed by zeta-potential, resulting in enhanced TO-CNF aggregation and colloidal gel formation. Systematic rheological testing shows that mechanical reinforcement of the prepared biohybrid gels is easily achieved by increasing the loading of HEWL. However, due to the relatively weak nature of electrostatic complexation, the formed colloidal gels exhibit partial destruction when subjected to cyclic shear stresses. Still, they resist thermo-cycling up to 90 °C. Finally, the pH responsiveness of the colloidal complex gels was demonstrated by adjusting pH to above and below the isoelectric point of HEWL, representing a facile mechanism to tune the gelation of TO-CNF/HEWL complexes. This work highlights the potential of using electrostatic complexation between HEWL and TO-CNF to form hybrid colloids, and demonstrates the tunability of the colloidal morphology and rheology by adjusting the ratio between the two components and the pH.

Overcoming negatively charged tissue barriers: Drug delivery using cationic peptides and proteins

Negatively charged tissues are ubiquitous in the human body and are associated with a number of common diseases yet remain an outstanding challenge for targeted drug delivery. While the anionic proteoglycans are critical for tissue structure and function, they make tissue matrix dense, conferring a high negative fixed charge density (FCD) that makes drug penetration through the tissue deep zones and drug delivery to resident cells extremely challenging. The high negative FCD of these tissues is now being utilized by taking advantage of electrostatic interactions to create positively charged multi-stage delivery methods that can sequentially penetrate through the full thickness of tissues, create a drug depot and target cells. After decades of work on attempting delivery using strong binding interactions, significant advances have recently been made using weak and reversible electrostatic interactions, a characteristic now considered essential to drug penetration and retention in negatively charged tissues. Here we discuss these advances using examples of negatively charged tissues (cartilage, meniscus, tendons and ligaments, nucleus pulposus, vitreous of eye, mucin, skin), and delve into how each of their structures, tissue matrix compositions and high negative FCDs create barriers to drug entry and explore how charge interactions are being used to overcome these barriers. We review work on tissue targeting cationic peptide and protein-based drug delivery, compare and contrast drug delivery designs, and also present examples of technologies that are entering clinical trials. We also present strategies on further enhancing drug retention within diseased tissues of lower FCD by using synergistic effects of short-range binding interactions like hydrophobic and H-bonds that stabilize long-range charge interactions. As electrostatic interactions are incorporated into design of drug delivery materials and used as a strategy to create properties that are reversible, tunable and dynamic, bio-electroceuticals are becoming an exciting new direction of research and clinical work.

Advanced Approaches of Bioactive Peptide Molecules and Protein Drug Delivery Systems

Despite the fact that protein and peptide therapeutics are widely employed in the treatment of various diseases, their delivery is posing an unembellished challenge to the scientists. It was discovered that delivery of these therapeutic systems through oral route is easy with high patient compliance. However, proteolytic degradation and absorption through the mucosal epithelium are the barriers in this route. These issues can be minimized by the use of enzyme inhibitors, absorption enhancers, different carrier systems or either by direct modification. In the process of investigation, it was found that transdermal route is not posing any challenges of enzymatic degradation, but, still absorption is the limitation as the outer layer of skin acts as a barrier. To suppress the effect of the barrier and increase the rate of the absorption, various advanced technologies were developed, namely, microneedle technology, iontophoresis, electroporation, sonophoresis and biochemical enhancement. Indeed, even these molecules are targeted to the cells with the use of cell-penetrating peptides. In this review, delivery of the peptide and protein therapeutics using oral, transdermal and other routes is discussed in detail.

Hydrogel-based commercial products for biomedical applications: A review

Hydrogels are hydrophilic polymer networks, able to absorb large amount of water, increasing their volume and showing a plethora of different material behaviors. Since their first practical application, dating from sixties of last century, they have been employed in several fields of biomedical sciences. After more than half a century of industrial uses, nowadays a lot of hydrogels are currently on the market for different purposes, and offering a wide spectra of features. In this review, even if it is virtually impossible to list all the commercial products based on hydrogels for biomedical applications, an extensive analysis of those materials that have reached the market has been carried out. The hydrogel-based materials used for drug delivery, wound dressing, tissue engineering, the building of contact lens, and hygiene products are enlisted and briefly described. A detailed snapshot of the set of these products that have reached the commercial maturity has been then obtained and presented. For each class of application, the basics of requirements are described, and then the materials are listed and classified on the basis of their chemical nature. For each product the commercial name, the producer, the chemical nature and the main characteristics are reported.

Enhanced Transdermal Drug Delivery by Sonophoresis and Simultaneous Application of Sonophoresis and Iontophoresis

Transdermal drug delivery has advantages of topical drug administration compared to the other conventional administration methods. However, the skin penetration of drugs is limited by the barrier properties of stratum corneum. The combinational strategy has been investigated to improve the skin permeability of the drug. For this study, we devised an improved device that can perform not only the single application of sonophoresis or iontophoresis but also the simultaneous application. The enhancement effect of sonophoresis was evaluated for various cosmeceutical drugs using a Franz diffusion cell. The enhancement ratio of niacinamide and retinol with sonophoresis was increased to 402% and 292%, respectively. The relationship was found between the enhancement effect of sonophoresis and the physicochemical properties of drugs. In particular, the simultaneous treatment of sonophoresis and iontophoresis enhanced skin penetration of glutamic acid to 240% using the fabricated device. The simultaneous application showed significantly higher enhancement ratio than application of sonophoresis or iontophoresis alone. Moreover, the improved device achieved skin penetration enhancement of various cosmeceutical drugs with lower intensity and a short application time. This combined strategy of transdermal physical enhancement methods is advantageous in terms of decline in energy density, thereby reducing the skin irritation. The miniaturized device with sonophoresis and iontophoresis is a promising approach due to enhanced transdermal drug delivery and feasibility of self-administration in cosmetic and therapeutic fields.

Passive delivery of protein drugs through transdermal route

Skin is the largest external organ in the human body but its use for therapeutic purposes has been minimal. Stratum corneum residing on the uppermost layer of the skin provides a tough barrier to transport the drugs across the skin. Very small group of drugs sharing Lipinski properties, i.e. drugs having molecular weight not larger than 500 Da, having high lipophilicity and optimum polarity are fortunate enough to be used on skin therapeutics. But, at a time where modern therapeutics is slowly shifting from use of small molecular drugs towards the use of macromolecular therapeutic agents such as peptides, proteins and nucleotides in origin, skin therapeutics need to be evolved accordingly to cater the delivery of these agents. Physical technologies like iontophoresis, laser ablation, micro-needles and ultrasound, etc. have been introduced to enhance skin permeability. But their success is limited due to their complex working mechanisms and involvement of certain irreversible skin damage in some or other way. This review therefore explores the delivery strategies for transport of mainly peptide and protein drugs that do not involve any injuries (non-invasive) to the skin termed as passive delivery techniques. Chemical enhancers, nanocarriers, certain biological peptides and miscellaneous approaches like prodrugs are also thoroughly reviewed for their applications in protein delivery.

Getting Drugs Across Biological Barriers

The delivery of drugs to a target site frequently involves crossing biological barriers. The degree and nature of the impediment to flux, as well as the potential approaches to overcoming it, depend on the tissue, the drug, and numerous other factors. Here an overview of approaches that have been taken to crossing biological barriers is presented, with special attention to transdermal drug delivery. Technology and knowledge pertaining to addressing these issues in a variety of organs could have a significant clinical impact.

Transportan in nanocarriers improves skin localization and antitumor activity of paclitaxel

In this study, the ability of nanocarriers containing protein transduction domains (PTDs) of various classes to improve cutaneous paclitaxel delivery and efficacy in skin tumor models was evaluated. Microemulsions (MEs) were prepared by mixing a surfactant blend (polyoxyethylene 10 oleoyl ether, ethanol and propylene glycol), monocaprylin, and water. The PTD transportan (ME-T), penetratin (ME-P), or TAT (ME-TAT) was added at a concentration of 1 mM to the plain ME. All MEs displayed nanometric size (32.3–40.7 nm) and slight positive zeta potential (+4.1 mV to +6.8 mV). Skin penetration of paclitaxel from the MEs was assessed for 1–12 hours using porcine skin and Franz diffusion cells. Among the PTD-containing formulations, paclitaxel skin (stratum corneum + epidermis and dermis) penetration at 12 hours was maximized with ME-T, whereas ME-TAT provided the lowest penetration (1.6-fold less). This is consistent with the stronger ability of ME-T to increase transepidermal water loss (2.4-fold compared to water) and tissue permeability. The influence of PTD addition on the ME irritation potential was assessed by measuring interleukin-1α expression and viability of bioengineered skin equivalents. A 1.5- to 1.8-fold increase in interleukin-1α expression was induced by ME-T compared to the other formulations, but this effect was less pronounced (5.8-fold) than that mediated by the moderate irritant Triton. Because ME-T maximized paclitaxel cutaneous localization while being safer than Triton, its efficacy was assessed against basal cell carcinoma cells and a bioengineered three-dimensional melanoma model. Paclitaxel-containing ME-T reduced cells and tissue viability by twofold compared to drug solutions, suggesting the potential clinical usefulness of the formulation for the treatment of cutaneous tumors.

Recent advances in peptides for enhancing transdermal macromolecular drug delivery

Transdermal delivery of drugs, a compelling route of systemic drug delivery, provides painless, reliable, targeted, efficient and cost effective therapeutic regimen for patients. However, its use is limited by skin barrier especially the stratum corneum barrier. Moreover, transdermal delivery of macromolecules remains a challenge. Naturally, varieties of physical methods, chemical enhancers and drug carriers have been used to counteract this limitation. Recently, transdermal peptides discovered as safer, more efficient and more specific enhancers could promote the delivery of macromolecules across the skin. Herein, the underlying transdermal peptides are included. Subsequently, we have discussed typical applications and the possible mechanism of two groups of biologically inspired transdermal peptide enhancers, namely cell penetration peptides and transdermal enhanced peptides.

Chemical penetration enhancers

To achieve an efficient skin penetration of most compounds it is necessary to overcome the barrier function of the skin, provided mainly (but not only) by the stratum corneum. Among various strategies used or studied to date, chemical penetration enhancers are the most frequently employed with one of the longest histories of use. There is a multitude of agents described as penetration enhancers, and they present varying properties and structures. In this manuscript, we aim to provide a brief overview of traditional enhancers and some of their properties, focusing on the benefits of combination of chemical enhancers and on selected novel compounds that have shown promise to increase drug delivery into/across the skin.

Basics and recent advances in peptide and protein drug delivery

While the peptide and protein therapeutic market has developed significantly in the past decades, delivery has limited their use. Although oral delivery is preferred, most are currently delivered intravenously or subcutaneously due to degradation and limited absorption in the gastrointestinal tract. Therefore, absorption enhancers, enzyme inhibitors, carrier systems and stability enhancers are being studied to facilitate oral peptide delivery. Additionally, transdermal peptide delivery avoids the issues of the gastrointestinal tract, but also faces absorption limitations. Due to proteases, opsonization and agglutination, free peptides are not systemically stable without modifications. This review discusses oral and transdermal peptide drug delivery, focusing on barriers and solutions to absorption and stability issues. Methods to increase systemic stability and site-specific delivery are also discussed.

Risk assessment of excess drug and sunscreen absorption via skin with ablative fractional laser resurfacing : optimization of the applied dose for postoperative care

The ablative fractional laser is a new modality used for surgical resurfacing. It is expected that laser treatment can generally deliver drugs into and across the skin, which is toxicologically relevant. The aim of this study was to establish skin absorption characteristics of antibiotics, sunscreens, and macromolecules via laser-treated skin and during postoperative periods. Nude mice were employed as the animal model. The skin received a single irradiation of a fractional CO2 laser, using fluences of 4-10 mJ with spot densities of 100-400 spots/cm(2). In vitro skin permeation using Franz cells was performed. Levels of skin water loss and erythema were evaluated, and histological examinations with staining by hematoxylin and eosin, cyclooxygenase-2, and claudin-1 were carried out. Significant signs of erythema, edema, and scaling of the skin treated with the fractional laser were evident. Inflammatory infiltration and a reduction in tight junctions were also observed. Laser treatment at 6 mJ increased tetracycline and tretinoin fluxes by 70- and 9-fold, respectively. A higher fluence resulted in a greater tetracycline flux, but lower skin deposition. On the other hand, tretinoin skin deposition increased following an increase in the laser fluence. The fractional laser exhibited a negligible effect on modulating oxybenzone absorption. Dextrans with molecular weights of 4 and 10 kDa showed increased fluxes from 0.05 to 11.05 and 38.54 μg/cm(2)/h, respectively. The optimized drug dose for skin treated with the fractional laser was 1/70-1/60 of the regular dose. The skin histology and drug absorption had recovered to a normal status within 2-3 days. Our findings provide the first report on risk assessment of excessive skin absorption after fractional laser resurfacing.

Synergistic Effect and Mechanism of Cineole and Terpineol on In-vitro Transdermal Delivery of Huperzine A from Microemulsions

The aim of the present study was to investigate the influence and the mechanisms of cineole and terpineol on the in-vitro transdermal delivery of huperzine A from microemulsions, and their potential synergistic effect on the permeation enhancement. The transdermal delivery of huperzine A from microemulsions with different concentrations of cineole and terpineol through the rat abdominal skin was determined by Franz-type diffusion cells. The partition coefficient of huperzine A between the full thickness skin and microemulsion was determined. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) was carried out to analyze the effects of cineole and terpineol on the biophysical properties of the stratum corneum (SC) and the mechanisms of permeation enhancement. These results indicated that cineole and terpineol could synergistically increase the transdermal delivery of huperzine A from microemulsions through increasing the partition and diffusion coefficients of huperzine A. ATR-FTIR studies further validated the synergistic effect and revealed that the enhancing mechanisms were due to increasing the disorderliness and fluidity of SC lipid alkyl chains, disrupting the structure of keratin in SC, and extracting SC lipids. In conclusion, cineole and terpineol, acting synergistically to enhance the transdermal delivery of huperzine A from microemulsions, might provide an alternative permeation enhancer combination for the transdermal delivery of huperzine A.