Transdermal drug delivery systems: skin perturbation devices

Elucidating collective translocation of nanoparticles across the skin lipid matrix: a molecular dynamics study

The top layer of skin, the stratum corneum, provides a formidable barrier to the skin. Nanoparticles are utilized and further explored for personal and health care applications related to the skin. In the past few years, several researchers have studied the translocation and permeation of nanoparticles of various shapes, sizes, and surface chemistry through cell membranes. Most of these studies focused on a single nanoparticle and a simple bilayer system, whereas skin has a highly complex lipid membrane architecture. Moreover, it is highly unlikely that a nanoparticle formulation applied on the skin will not have multiple nanoparticle-nanoparticle and skin-nanoparticle interactions. In this study, we have utilized coarse-grained MARTINI molecular dynamics simulations to assess the interactions of two types (bare and dodecane-thiol coated) of nanoparticles with two models (single bilayer and double bilayer) of skin lipid membranes. The nanoparticles were found to be partitioned from the water layer to the lipid membrane as an individual entity as well as in the cluster form. It was discovered that each nanoparticle reached the interior of both single bilayer and double bilayer membranes irrespective of the nanoparticle type and concentration, though coated particles were observed to efficiently traverse across the bilayer when compared with bare particles. The coated nanoparticles also created a single large cluster inside the membrane, whereas the bare nanoparticles were found in small clusters. Both the nanoparticles exhibited preferential interactions with cholesterol molecules present in the lipid membrane as compared to other lipid components of the membrane. We have also observed that the single membrane model exhibited unrealistic instability at moderate to higher concentrations of nanoparticles, and hence for translocation study, a minimum double bilayer model should be employed.

Sandpaper curettage: A simple method to improve PDT outcomes for actinic keratosis

INTRODUCTION

Photodynamic therapy (PDT) is a non-scarring, repeatable, and safe treatment for actinic keratosis (AK), but improvements in efficacy are still needed.

BACKGROUND

Devices such as steel blades, needle rollers, and lasers are currently used to remove hypertrophic stratum corneum on AKs to improve PDT outcomes. However, curettage with fine sandpaper could be a gentler, effective alternative.

METHODS

A retrospective study was designed to compare PDT with or without sandpaper curettage. Patients were selected from a database registry of patients with face and scalp AKs (ClinicalTrials.gov NCT03319251). Patients in Group 1 underwent PDT alone (20% ALA, 15 min; blue light 417 nm, 30 min). Patients in Group 2 were pretreated with gentle sandpaper curettage prior to ALA and illumination. The two groups were compared using multivariate matching, normalizing for age, sex, initial AK counts, and time to follow-up.

RESULTS

Sixty-six patients were selected for matching analysis (n=38, PDT only; n=28, PDT+curettage). Demographics between the groups were similar (mean ± SD), including age (71.0 ± 8.3 vs. 71.0 ± 8.0 years), baseline AK count (53 ± 39 vs. 44± 32), and time to post-PDT follow-up (111 ± 28 vs. 113 ± 32 days). At follow-up, patients who received curettage showed an overall 55% improvement in scalp AK clearance compared to patients who did not receive curettage, adjusting for sex, age, time to follow-up, and baseline AK count (p = 0.0322, multivariable linear regression).

DISCUSSION

Sandpaper curettage before PDT treatment is an easy and inexpensive method to significantly improve AK clearance rates.

Plant Nanovesicles for Essential Oil Delivery

Essential oils' therapeutic potential is highly recognized, with many applications rising due to reported anti-inflammatory, cardioprotective, neuroprotective, anti-aging, and anti-cancer effects. Nevertheless, clinical translation still remains a challenge, mainly due to essential oils' volatility and low water solubility and stability. The present review gathers relevant information and postulates on the potential application of plant nanovesicles to effectively deliver essential oils to target organs. Indeed, plant nanovesicles are emerging as alternatives to mammalian vesicles and synthetic carriers due to their safety, stability, non-toxicity, and low immunogenicity. Moreover, they can be produced on a large scale from various plant parts, enabling an easier, more rapid, and less costly industrial application that could add value to waste products and boost the circular economy. Importantly, the use of plant nanovesicles as delivery platforms could increase essential oils' bioavailability and improve chemical stability while reducing volatility and toxicity issues. Additionally, using targeting strategies, essential oils' selectivity, drug delivery, and efficacy could be improved, ultimately leading to dose reduction and patient compliance. Bearing this in mind, information on current pharmaceutical technologies available to enable distinct routes of administration of loaded vesicles is also discussed.

Microneedle system: a modulated approach for penetration enhancement

The microneedles show advantages over transdermal drug delivery systems on account of better skin permeation bypassing the stratum corneum. To increase the flux of permeation, penetration enhancement techniques like physical and chemical methods are combined with a trans-epidermal delivery system across the skin causing minimal pain. These techniques include iontophoresis, sonophoresis, and electroporation for physical enhancement of drug delivery via topical route by either disrupting the structure of the stratum corneum or by creating pores/micro-channels within the skin. The use of chemical penetrants such as ethanol, lipids, surfactants, and terpenes improves the release kinetics by mechanisms like fluidization of lipids, denaturation of proteins, etc. A combination of microneedles and these techniques show a significant increase in the permeability of drugs across the skin by 5-10 times compared to microneedles alone. This review article focuses on various advanced strategies like the use of drug-polymer complexes, application of ultrasound frequency or tolerable electric current, formation of nano-formulations, etc. with microneedle delivery for transportation of high payload of actives, macromolecules, antibodies, gene, proteins, and peptides. In the near future, microneedle systems will offer potential targeted drug delivery, self-sealable administration across the skin, and minimally invasive vaccine transportation in cancer, diabetes, Alzheimer's, and cardiovascular diseases.HighlightsPhysical penetration enhancement techniques: iontophoresis, electroporation, and sonophoresis.Chemical penetration enhancers: polymers, lipids, surfactants.Strategies to use microneedle system with penetration enhancement techniques.The significant difference in the penetration ability of high payload actives.

Polymeric Nanoparticles for Transdermal Delivery of Polyphenols

Polyphenols comprises of a large group of naturally occurring plant secondary metabolites having various nutritional and health benefits. They are safe and are found abundantly in the diet. Current research on polyphenols focuses on their mechanism and their benefits on the human health. However, due to their low solubility and bioavailability, delivery from conventional route has been a challenge and their translation into clinical applications has been limited. Topical and transdermal delivery of polymeric nanoparticles will act as a novel therapeutic approach for promising delivery of polyphenols. In this review, we have evaluated the existing scientific literature and summarized the potential use of polymeric nanoparticles as a carrier for polyphenolic compounds for delivery via topical and transdermal routes for the treatment of skin cancers such as melanoma.

Peeking into the future: Transdermal patches for the delivery of micronutrient supplements

Adhesive transdermal delivery devices (patches) are the latest advancement in the delivery of micronutrients. A common challenge in this mode of delivery includes surpassing the physical barrier of the skin, while the use of microneedle (MN) arrays, or pretreatment of the skin with MNs can be used for a more successful outcome. Limited evidence from human non-randomized trials point to a sub-optimal delivery of iron through skin patches, although no MNs were used in those trials. Moreover, the use of patches proved inefficient in reducing the prevalence of micronutrient deficiencies in post-bariatric surgery patients. The delivery of minerals was tested in animals using reservoir-type patches, gel/foam patches, MNs and iontophoresis. Results from these studies indicate a possible interplay between the dietary manipulation of mineral intake and the trandermal delivery through patches, as reduced, or regular dietary intake seems to increase absorption of the delivered mineral. Moreover, intervention duration could be an additional factor affecting absorption. Possible adverse events from animal studies include redness or decolorization of skin. In vitro and ex vivo studies revealed an increase in vitamin K, vitamin D and iron delivery, however a variety of methodological discrepancies are apparent in these studies, including the models used, the length of the MNs, the duration of application, temperature control and total micronutrient load in the patches. Data indicate that pre-treating the skin with MNs might enhance delivery; however, a source of variability in the observed effectiveness might include the different molecular weights of the nutrients used, skin factors, the ideal tip radius and MN wall thickness. Non-human studies indicate a potential benefit in combining MN with iontophoresis. Presently, the transdermal delivery seems promising with regard to nutritional supplementation, however limited evidence exists for its efficacy in humans. Future research should aim to control for both intervention duration, possible deficiency status and for the dietary intake of participants.

Uptake and trafficking of different sized PLGA nanoparticles by dendritic cells in imiquimod-induced psoriasis-like mice model

Psoriasis is an autoimmune inflammatory disease, where dendritic cells (DCs) play an important role in its pathogenesis. In our previous work, we have demonstrated that topical delivery of curcumin-loaded poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) could treat Imiquimod (IMQ)-induced psoriasis-like mice. The objective of this study is to further elucidate biofate of PLGA NPs after intradermal delivery including DCs uptake, and their further trafficking in psoriasis-like mice model by using fluorescence probes. Two-sized DiO/DiI-loaded PLGA NPs of 50 ± 4.9 nm (S-NPs) and 226 ± 7.8 nm (L-NPs) were fabricated, respectively. In vitro cellular uptake results showed that NPs could be internalized into DCs with intact form, and DCs preferred to uptake larger NPs. Consistently, in vivo study showed that L-NPs were more captured by DCs and NPs were firstly transported to skin-draining lymph nodes (SDLN), then to spleens after 8 h injection, whereas more S-NPs were transported into SDLN and spleens. Moreover, FRET imaging showed more structurally intact L-NPs distributed in skins and lymph nodes. In conclusion, particle size can affect the uptake and trafficking of NPs by DCs in skin and lymphoid system, which needs to be considered in NPs tailing to treat inflammatory skin disease like psoriasis.

Hollow microneedles: A perspective in biomedical applications

Microneedles (MN) have the potential to become a highly progressive device for both drug delivery and monitoring purposes as they penetrate the skin and pierce the stratum corneum barrier, allowing the delivery of drugs in the viable skin layers and the extraction of body fluids. Despite the many years of research and the different types of MN developed, only hollow MN have reached the pharmaceutical market under the path of medical devices. Therefore, this review focuses on hollow MN, materials and methods for their fabrication as well as their application in drug delivery, vaccine delivery and monitoring purposes. Furthermore, novel approaches for the fabrication of hollow MN are included as well as prospects of microneedle-based products on the market.

Polyoxyethylene/polyoxypropylene dimethyl ether (EPDME) random copolymer improves lipid structural ordering in stratum corneum of an epidermal-equivalent model as seen by two-photon microscopy

BACKGROUND/PURPOSE

Topical application of polyoxyethylene/polyoxypropylene dimethyl ether (EPDME) random copolymer improves the barrier function of skin, whereas polyethylene glycol (PEG) and polypropylene glycol (PPG) are ineffective. The aim of this work was to examine the interaction between these polymers and lipid molecules in the stratum corneum in order to establish whether EPDME-specific changes in the structural ordering of lipids might account for the improvement of barrier function.

METHODS

We used two-photon microscopy to evaluate the effects of EPDME, PEG, and PPG on the structural ordering of lipids in an epidermal-equivalent model in terms of the fluorescence changes of Laurdan, a fluorescent dye that responds to changes of membrane fluidity. The generalized polarization (GP) value, a parameter that reflects lipid ordering, was measured at various depths from the surface of the stratum corneum.

RESULTS

EPDME increased the GP value to a depth of about 3 µm from the surface, indicating that lipid ordering was increased in this region, while PEG and PPG of the same molecular weight had no effect. Diffusion of Lucifer yellow into the epidermis was reduced after application of EPDME, indicating that the barrier function was improved.

CONCLUSION

These results support the view that EPDME improves barrier function by increasing the ordering of lipid structures in the stratum corneum. The methodology described here could be useful for screening new compounds that would improve the structural ordering of lipids.

Clinical Evaluation of Sequential Transdermal Delivery of Vitamin B6, Compound Glycyrrhizin, Metronidazole, and Hyaluronic Acid Using Needle-Free Liquid Jet in Facial Seborrheic Dermatitis

Facial seborrheic dermatitis (FSD) is a common facial inflammatory dermatitis. Needle-free transdermal jet injection (NTJI) is a non-invasive injection of drug solution by using a high-pressure liquid injection instrument. To explore a safer, more tolerable, and convenient medical way using NTJI in the treatment of FSD, the patients were treated with vitamin B6, glycyrrhizin compound, metronidazole, and hyaluronic acid sequentially using NTJI every 2 weeks, and only those treated for more than three times were included. A VISIA facial imaging system for the evaluation of erythema, superficial lipid level, and roughness of skin surface and a CK analyzer for biophysical parameters, including the stratum corneum hydration, facial surface lipid, and trans-epidermal water loss, were applied. Erythema was significantly reduced after every treatment (weeks 2, 4, and 6; P < 0.05), whereas superficial lipid level was not improved significantly until week 6 (P < 0.05), and roughness of the skin surface was not improved significantly during the whole treatment. The stratum corneum hydration of lesional skin was significantly increased after three times of treatment (P < 0.05). No observable adverse effect, such as marked erythema, blistering, or atrophy, was observed. Sequential transdermal delivery of small molecular weight drugs (vitamin B6, glycyrrhizin compound, metronidazole, and hyaluronic acid) using NTJI is a safe, low-toxicity, and take-home drug-free therapy for the treatment of FSD.

Microneedles: Characteristics, Materials, Production Methods and Commercial Development

Although transdermal drug delivery systems (DDS) offer numerous benefits for patients, including the avoidance of both gastric irritation and first-pass metabolism effect, as well as improved patient compliance, only a limited number of active pharmaceutical ingredients (APIs) can be delivered accordingly. Microneedles (MNs) represent one of the most promising concepts for effective transdermal drug delivery that penetrate the protective skin barrier in a minimally invasive and painless manner. The first MNs were produced in the 90s, and since then, this field has been continually evolving. Therefore, different manufacturing methods, not only for MNs but also MN molds, are introduced, which allows for the cost-effective production of MNs for drug and vaccine delivery and even diagnostic/monitoring purposes. The focus of this review is to give a brief overview of MN characteristics, material composition, as well as the production and commercial development of MN-based systems.

Derma rollers in therapy: the transition from cosmetics to transdermal drug delivery

Derma roller, a device rolled onto the skin to form micropores, is extensively used for cosmetic purposes. The pores thus created are utilized to either result in the induction of collagen production, leading to glowing and wrinkle-free skin or for permeating the applied formulations to the site of action within the skin. Recent studies have shown the benefits of using derma rollers for transdermal delivery of drugs. In the nascent stage, this approach paves a way to successfully breach the stratum corneum and aid in the movement of medications directed towards the dermis and the hair follicles. The review essentially summarizes the evidence of the use of derma rollers in cosmetic setup, their designing, and the preclinical and clinical reports of efficacy, safety, and concerns when translated for pharmaceutical purposes and transdermal drug delivery.

Potential of Sonophoresis as a Skin Penetration Technique in the Treatment of Rheumatoid Arthritis with Transdermal Patch

Rheumatoid arthritis, a chronic disorder, limits the use of chemical penetration enhancers for a prolonged period of time. Moreover, systemic routes of administration of the first-line drug, methotrexate, have shown undesirable systemic as well as local side effects. The objective of this research was to overcome the limitations associated with treatment of rheumatoid arthritis by utilizing three physical transdermal penetration enhancement techniques namely cold-laser, electroporation, and sonophoresis to deliver methotrexate. Methotrexate patch was prepared using solvent casting method and the ex-vivo release of methotrexate in combination with three physical penetration enhancers (sonophoresis, electroporation, and cold laser) were studied. The best technique was employed in pre-clinical testing in arthritic and control groups of male Wistar rats excluding remaining two techniques. The comparative ex-vivo studies showed that the penetration enhancement of methotrexate is maximum by sonophoresis followed by electroporation and cold laser (sonophoresis > electroporation > cold laser). In pharmacodynamic studies, the reduction in diameter of injected and non-injected paw on day 5 and day 21 for group 4 (ultrasound pre-treated group) was higher as compared to group 3 (group receiving only methotrexate patch). The motility score and the reduction in pain were significantly improved for group 4 than group 3 on both day 5 and day 21 (P ˂ 0.05) which confirmed the faster recovery of animals of group 4 due to penetration enhancement of methotrexate patch by ultrasound treatment. From the results, it can be concluded that sonophoresis along with methotrexate patch has shown a significant effect in the treatment of rheumatoid arthritis.

Evaluation of Heat Effects on Transdermal Nicotine Delivery In Vitro and In Silico Using Heat-Enhanced Transport Model Analysis

A combined experimental and computational model approach was developed to assess heat effects on drug delivery from transdermal delivery systems (TDSs) in vitro and nicotine was the model drug. A Franz diffusion cell system was modified to allow close control of skin temperature when heat was applied from an infrared lamp in vitro. The effects of different heat application regimens on nicotine fluxes from two commercial TDSs across human cadaver skin were determined. Results were interpreted in terms of transport parameters estimated using a computational heat and mass transport model. Steady-state skin surface temperature was obtained rapidly after heat application. Increasing skin surface temperature from 32 to 42°C resulted in an approximately 2-fold increase in average nicotine flux for both TDSs, with maximum flux observed during early heat application. ANOVA statistical analyses of the in vitro permeation data identified TDS differences, further evidenced by the need for a two-layer model to describe one of the TDSs. Activation energies associated with these data suggest similar temperature effects on nicotine transport across the skin despite TDS design differences. Model simulations based on data obtained from continuous heat application were able to predict system response to intermittent heat application, as shown by the agreement between the simulation results and experimental data of nicotine fluxes under four different heat application regimens. The combination of in vitro permeation testing and a computational model provided a parameter-based heat and mass transport approach to evaluate heat effects on nicotine TDS delivery.

Stimuli-responsive graphene-incorporated multifunctional chitosan for drug delivery applications: a review

INTRODUCTION

Recently, the use of chitosan (CS) in the drug delivery has reached an acceptable maturity. Graphene-based drug delivery is also increasing rapidly due to its unique physical, mechanical, chemical, and electrical properties. Therefore, the combination of CS and graphene can provide a promising carrier for the loading and controlled release of therapeutic agents.

AREAS COVERED

In this review, we will outline the advantages of this new drug delivery system (DDS) in association with CS and graphene alone and will list the various forms of these carriers, which have been studied in recent years as DDSs. Finally, we will discuss the application of this hybrid composite in other fields.

EXPERT OPINION

The introducing the GO amends the mechanical characteristics of CS, which is a major problem in the use of CS-based carriers in drug delivery due to burst release in a CS-based controlled release system through the poor mechanical strength of CS. Many related research on this area are still not fully unstated and occasionally they seem inconsistent in spite of the intent to be complementary. Therefore, a sensitive review may be needed to understand the role of graphene in CS/graphene carriers for future drug delivery applications.

Multifunctional chitosan-magnetic graphene quantum dot nanocomposites for the release of therapeutics from detachable and non-detachable biodegradable microneedle arrays

Biodegradable chitosan-magnetic graphene quantum dot (MGQD) nanocomposites were prepared and investigated for the release of small and large molecular weight (MWt) therapeutics from detachable and non-detachable biodegradable microneedle arrays. The presence of MGQDs in chitosan increased the electrical conductivity and biodegradation rate of chitosan while maintaining its mechanical properties. The detachable microneedle arrays were created by including a water-soluble ring of poly(ethylene glycol) (PEG) at the base of the microneedle, which enabled the rapid detachment of the microneedle shaft from the base. The PEG ring did not impede the microneedle array performance, with mechanical properties and a drug release profile of low MWt lidocaine hydrochloride similar to microneedle arrays without the ring. Without the PEG ring, the chitosan-MGQD microneedles were electrically conductive and allowed for electrically stimulated release of large MWt therapeutics which was challenging without the stimulation. These results demonstrate that chitosan nanocomposites containing MGQDs with intrinsic photoluminescent and supermagnetic properties are promising materials for developing multifunctional microneedles for targeted and tracked transdermal drug delivery.

In vitro and in vivo Methods for the Evaluation of Natural Products against Dermatophytes

Dermatomycoses are infections caused by fungi called dermatophytes; these affect 20–25% of the world population and the incidence continues to grow each year. Recently, an alternative for the treatment of these diseases is the use of natural products, thanks to the fact that they possess great chemical diversity and thus biological activity. However, to understand the therapeutic potential of natural products, their microbiological assessment presents certain limitations. Currently, there is no established reference method to determine the antifungal capacity in vitro and in vivo of natural products (i.e., essential oils). This review focuses on describing the various microbiological methods as well as the many adaptations used to evaluate the antifungal activity of natural products both in vitro and in vivo. In addition, the antifungal evaluation of natural products formulated in creams, gels, nanoemulsions, nanocapsules and solid lipid nanoparticles is included.

Transdermal Drug Delivery: Innovative Pharmaceutical Developments Based on Disruption of the Barrier Properties of the stratum corneum

The skin offers an accessible and convenient site for the administration of medications. To this end, the field of transdermal drug delivery, aimed at developing safe and efficacious means of delivering medications across the skin, has in the past and continues to garner much time and investment with the continuous advancement of new and innovative approaches. This review details the progress and current status of the transdermal drug delivery field and describes numerous pharmaceutical developments which have been employed to overcome limitations associated with skin delivery systems. Advantages and disadvantages of the various approaches are detailed, commercially marketed products are highlighted and particular attention is paid to the emerging field of microneedle technologies.

Assessing the Impact of Mechanical Damage on Full-Thickness Porcine and Human Skin Using an In Vitro Approach

For most xenobiotics, the rates of percutaneous absorption are limited by diffusion through the horny layer of skin. However, percutaneous absorption of chemicals may seriously increase when the skin is damaged. The aim of this work was to develop an in vitro representative model of mechanically damaged skins. The epidermal barrier was examined following exposure to a razor, a rotating brush, and a microneedle system in comparison to tape-stripping which acted as a reference. Excised full-thickness skins were mounted on a diffusion chamber in order to evaluate the effect of injuries and to mimic physiological conditions. The transepidermal water loss (TEWL) was greatly increased when the barrier function was compromised. Measurements were made for all the damaged biopsies and observed histologically by microscopy. On human and porcine skins, the tape-stripping application (0 to 40 times) showed a proportional increase in TEWL which highlights the destruction of the stratum corneum. Similar results were obtained for all cosmetic instruments. This is reflected in our study by the nonsignificant difference of the mean TEWL scores between 30 strips and mechanical damage. For a specific appreciation, damaged skins were then selected to qualitatively evaluate the absorption of a chlorogenic acid solution using fluorescence microscopy.

Nanotopography facilitates in vivo transdermal delivery of high molecular weight therapeutics through an integrin-dependent mechanism

Transdermal delivery of therapeutics is restricted by narrow limitations on size and hydrophobicity. Nanotopography has been shown to significantly enhance high molecular weight paracellular transport in vitro. Herein, we demonstrate for the first time that nanotopography applied to microneedles significantly enhances transdermal delivery of etanercept, a 150 kD therapeutic, in both rats and rabbits. We further show that this effect is mediated by remodeling of the tight junction proteins initiated via integrin binding to the nanotopography, followed by phosphorylation of myosin light chain (MLC) and activation of the actomyosin complex, which in turn increase paracellular permeability.

A review of TTS – development, types and preparations

Transdermal Therapeutic Systems (TTS) are elastic multi-layer patches applied to the skin in order to deliver active substances into the bloodstream. One advantage of a transdermal drug delivery route over other types of medication delivery is that the patch provides a noninvasive therapy, longer duration of drug activity, and improves most of bioavailability. TTS consist of a backing layer, a drug, an adhesive, and a release liner. TTS can be divided into five basic types of systems: reservoir, matrix, microreservoir, single-layer drug in adhesive, and multi-layer drug in adhesive. In order to improve the penetration of drugs through the skin, passive and active methods are used. The researchers are constantly developing new methods of improving the delivery of drugs applied by transdermal route.

Biodegradable and conductive chitosan–graphene quantum dot nanocomposite microneedles for delivery of both small and large molecular weight therapeutics

Chitosan–graphene quantum dot nanocomposites are used in microneedle arrays for transdermal delivery of small and large molecular weight drugs.

Strong and conductive chitosan-reduced graphene oxide nanocomposites for transdermal drug delivery

Chitosan-reduced graphene oxide (rGO) nanocomposites were synthesized through a biocompatible reduction process and were first reported for applications in transdermal drug delivery devices, such as microneedle arrays. Introducing rGO improved the mechanical properties of chitosan, with the strongest nanocomposites containing 1 wt% and 2 wt% rGO chosen to undergo drug delivery testing. The addition of rGO increased the electrical conductivity of chitosan, allowing the nanocomposites to be used for electroporation or iontophoresis drug delivery applications. The rGO content was proven to be an important factor for drug delivery due to the bonding of drug onto rGO. Increasing the rGO content allowed for a quicker and more substantial drug release, allowing for a controlled drug release rate. The nanocomposites also exhibited pH dependent release behaviour, with a reduced release rate in the presence of an acidic medium. The biodegradation rate of chitosan decreased when rGO was added but the biodegradation rates of the nanocomposites are not dependent on the rGO concentration, with nanocomposites of 1 wt% and 2 wt% rGO possessing a similar biodegradation path. The use of the nanocomposite in a microneedle array was shown through compression testing and drug release testing in a pseudo-in vivo environment.

Effect of lipophilicity on microneedle-mediated iontophoretic transdermal delivery across human skin in vitro

The effect of lipophilicity of drug on the microneedle (MN)-mediated iontophoretic delivery across dermatomed human skin was studied. Beta blockers with similar pKa but varied log P values were selected as model drugs in this study. Iontophoresis (ITP) or MNs, when used independently, increased the transdermal flux of beta blockers as compared with passive delivery (PD). ITP across the MN-treated skin (MN + ITP) increased the permeation rate of all beta blockers as compared with PD (p < 0.001). The enhancement ratios (ER) for hydrophilic molecules (atenolol and sotalol) were 71- and 78-fold higher for ITP + MN as compared with PD. However, for lipophilic molecule such as propranolol, there was 10-fold increase in the ER as compared with PD. These observations were further substantiated by the skin retention data; an inverse relationship between the skin retention and the hydrophilicity of the drug was observed. The results in the present study point out that the lipophilicity of the molecule plays a significant role on the electrically assisted transdermal delivery of drugs across the microporated skin. Using the combination of ITP + MN, hydrophilic drugs (atenolol and sotalol) were delivered at a much higher rate as compared with lipophilic molecules (propranolol and acebutolol).

Transcutaneous antigen delivery system

Transcutaneous immunization refers to the topical application of antigens onto the epidermis. Transcutaneous immunization targeting the Langerhans cells of the skin has received much attention due to its safe, needle-free, and noninvasive antigen delivery. The skin has important immunological functions with unique roles for antigen-presenting cells such as epidermal Langerhans cells and dermal dendritic cells. In recent years, novel vaccine delivery strategies have continually been developed; however, transcutaneous immunization has not yet been fully exploited due to the penetration barrier represented by the stratum corneum, which inhibits the transport of antigens and adjuvants. Herein we review recent achievements in transcutaneous immunization, focusing on the various strategies for the enhancement of antigen delivery and vaccination efficacy. [BMB Reports 2013; 46(1): 17-24]

Effects of non-Newtonian power law rheology on mass transport of a neutral solute for electro-osmotic flow in a porous microtube

Mass transport of a neutral solute for a power law fluid in a porous microtube under electro-osmotic flow regime is characterized in this study. Combined electro-osmotic and pressure driven flow is conducted herein. An analytical solution of concentration profile within mass transfer boundary layer is derived from the first principle. The solute transport through the porous wall is also coupled with the electro-osmotic flow to predict the solute concentration in the permeate stream. The effects of non-Newtonian rheology and the operating conditions on the permeation rate and permeate solute concentration are analyzed in detail. Both cases of assisting (electro-osmotic and poiseulle flow are in same direction) and opposing flow (the individual flows are in opposite direction) cases are taken care of. Enhancement of Sherwood due to electro-osmotic flow for a non-porous conduit is also quantified. Effects if non-Newtonian rheology on Sherwood number enhancement are observed.

Engineering approaches to transdermal drug delivery: a tribute to contributions of prof. Robert Langer

Transdermal drug delivery continues to provide an advantageous route of drug administration over injections. While the number of drugs delivered by passive transdermal patches has increased over the years, no macromolecule is currently delivered by the transdermal route. Substantial research efforts have been dedicated by a large number of researchers representing varied disciplines including biology, chemistry, pharmaceutics and engineering to understand, model and overcome the skin's barrier properties. This article focuses on engineering contributions to the field of transdermal drug delivery. The article pays tribute to Prof. Robert Langer, who pioneered the engineering approach towards transdermal drug delivery. Over a period spanning nearly 25 years since his first publication in the field of transdermal drug delivery, Bob Langer has deeply impacted the field by quantitative analysis and innovative engineering. At the same time, he has inspired several generations of engineers by collaborations and mentorship. His scientific insights, innovative technologies, translational efforts and dedicated mentorship have transformed the field.

Therapeutic efficacy of halocidin-derived peptide HG1 in a mouse model of Candida albicans oral infection

OBJECTIVES

HG1 is an antimicrobial peptide derived from halocidin, which is naturally found in tunicates. The purpose of this study was to evaluate the therapeutic potential of HG1 as a novel antifungal agent for treating oral candidiasis.

METHODS

The pharmacokinetic properties of HG1 were explored in mice, which were orally administered a single dose of HG1. Anti-Candida activity of HG1 was investigated in a time-dependent manner in the presence of saliva obtained from healthy donors or patients with oral candidiasis. In addition, HG1 was evaluated for its anti-Candida activity in the presence of proteins extracted from the culture supernatant of Candida albicans. The therapeutic potential in vivo and ex vivo of HG1 against oral candidiasis was investigated using a mouse model of oral candidiasis.

RESULTS

Our data showed that absorption of HG1 into the blood did not occur following oral administration. In addition, HG1 exerted marked anti-Candida activity after short-term incubation at a concentration of 20 mg/L and it also caused a considerable reduction in fungal burden in the oral candidiasis mouse model when treated with 1 mg or 0.5 mg.

CONCLUSIONS

This study suggests that HG1, as a novel component of mouthwash, might become an alternative antifungal agent to conventional drugs used to manage oral candidiasis.

Potential of polar lipids from bovine milk to regulate the rodent dorsal hair cycle

Among the lipids in bovine milk, minor components such as conjugated linoleic acids and phospholipids are more attractive than triacylglycerols from the standpoint of biological activity. To explore novel functions of bovine milk polar lipids (MPL), topical application to murine dorsal skin was introduced as an assay system. The acetone-insoluble lipid fraction derived from bovine milk was dispersed in ethanol and applied to 9-wk-old C57BL/6N female mice for 3 wk. In combination with visual assessment of the dorsal pigmentation, the progression of the hair cycle was estimated by calculating the ratio of subcutis to dermis thickness. The administration of MPL led to earlier progression of the hair cycle compared with administration of the vehicle. In some cases, the extent of MPL-induced hair cycle progression was comparable to that in animals treated with minoxidil, the most well-known reagent that initiates anagen. These results indicate that the MPL preparation contains a dermal penetrative component that can regulate the hair cycle and, thus, this preparation possesses potential for cosmetic use.

Effect of a novel penetration enhancer on the ungual permeation of two antifungal agents

OBJECTIVES

The aim of this study was to demonstrate the effect of a novel permeation enhancer system using two existing marketed nail lacquers and the delivery of terbinafine through human nail samples in vitro.

METHODS

Initially a modified Franz cell was used, where sections of human nail serve as the barrier through which drug penetrates into an agar-filled chamber infected with dermatophytes. A second study was performed using a novel infected nail model where dermatophytes are incubated with and grow into human nail and ATP levels are used as biological marker for antimicrobial activity.

KEY FINDINGS

The novel permeation enhancing system increased the permeation of both existing drugs formulated in nail lacquers and terbinafine through human nail sections mounted in a modified Franz cell. Furthermore the ATP assay confirmed that the system also enhanced the permeation of terbinafine through infected cadaver nail resulting in a decrease in ATP levels equivalent to those of uninfected negative control samples.

CONCLUSIONS

This study has clearly demonstrated that the use of a novel permeation enhancing system, which fundamentally alters the chemical structure of the nail, not only enhances the efficacy of the existing topical formulations but also enables the delivery and efficacy of terbinafine when applied ungually. Such a topically applied system has the possibility of overcoming the systemic side effects when terbinafine is delivered orally.

The influence of porosity changes in human epidermal membrane during iontophoresis on the permeability enhancement of a model peptide

PURPOSE

We tested the hypothesis that the increases in the porosity of the skin during iontophoresis would not significantly increase the transport of peptides due to the small size of electrically induced pores. To investigate this mechanistically, we used human epidermal membrane under constant voltage conditions, applying the Nernst-Planck equation to the transport of a small ionic solute, tetraethylammonium bromide (TEAB), and a model peptide, luteinizing hormone releasing hormone.

METHODS

Steady-state flux of the drugs was determined under passive conditions and also during iontophoresis using constant DC voltages applied across side-by-side diffusion cells. Electrical conductance measurements were used to monitor the porosity changes that occur during electrical field application.

RESULTS

Porosity increases observed in the membrane substantially increased the permeability enhancement of the small ionic solute TEAB. The permeability enhancement was well described by Nernst-Planck model predictions after porosity changes in the membrane were taken into account. Enhancement of luteinizing hormone releasing hormone under identical conditions was much less than TEAB. The porosity increases induced by iontophoresis had little or no effect on the permeability enhancement of the larger molecule.

CONCLUSIONS

These findings closely parallel those reports that have found electrically induced pores to be significantly smaller than preexisting pores in the human epidermal membrane. The data obtained also support the view that iontophoresis-induced pores, alone, may provide limited benefit for macromolecule transport across the skin.

Electroporation as an efficient physical enhancer for skin drug delivery

Transdermal drug delivery offers an attractive alternative to the conventional drug delivery methods of oral administration and injection. However, the stratum corneum acts as a barrier that limits the penetration of substances through the skin. Application of high-voltage pulses to the skin increases its permeability (electroporation) and enables the delivery of various substances into and through the skin. The application of electroporation to the skin has been shown to increase transdermal drug delivery. Moreover, electroporation, used alone or in combination with other enhancement methods, expands the range of drugs (small to macromolecules, lipophilic or hydrophilic, charged or neutral molecules) that can be delivered transdermally. The efficacy of transport depends on the electrical parameters and the physicochemical properties of drugs. The in vivo application of high-voltage pulses is well tolerated, but muscle contractions are usually induced. The electrode and patch design is an important issue to reduce the discomfort of the electrical treatment in humans. This review presents the main findings in the field of electroporation-namely, transdermal drug delivery. Particular attention is paid to proposed enhancement mechanisms and trends in the field of topical and transdermal delivery.

Acyclovir delivery systems

Herpes viruses (herpes simplex, varicella zoster, cytomegalovirus) are the main cause of a wide variety of human infections. Although the development of successful antiviral agents against infections caused by herpes viruses had been slow until the last decade, the production of delivery systems for acyclovir are a promising alternative. The present review summarizes the principal advances made in developing carriers for the delivery of acyclovir by different routes of administration.

Applications of ultrasonic skin permeation in transdermal drug delivery

Transdermal ultrasound-mediated drug delivery has been studied as a method for needle-less, non-invasive drug administration. Potential obstacles include the stratum corneum, which is not sufficiently passively permeable to allow effective transfer of many medications into the bloodstream without active methods. A general review of the transdermal ultrasound drug delivery literature has shown that this technology offers promising potential for non-invasive drug administration. Included in this review are the reported acoustic parameters used for achieving delivery, along with the known intensities and exposure times. Ultrasound mechanisms are discussed as well as spatial field characteristics. Accurate and precise quantification of the acoustic field used in drug delivery experiments is essential to ensure safety versus efficacy and to avoid potentially harmful bioeffects.