Iontophoresis of Biological Macromolecular Drugs

(Re)evolution in nanoparticles-loaded microneedle delivery systems: are we getting closer to a clinical translation?

The deposition of drug-loaded nanoparticles within the skin structure has been a challenge due to the inexorable skin barrier function. Unless specific nanoparticles like liposomes and lipid-based related vesicles, most nanoparticles cannot penetrate the epidermal layers by themselves. This is the reason why microneedle-based systems are nowadays the most straightforward systems in skin research. They can greatly bypass the stratum corneum and deposit the supramolecular cargo entities in the dermal layers, which can perform specific features such as drug-controlled release, specific targeting or stimuli-responsive behaviors. At this point, after more than 20 years of research using this nanoparticle-microneedle combination and all the positive results, the clinical experience is still so limited. Therefore, how is it possible that the everlasting promise of the clinical translation of these systems has not reached a real clinical practice? In this piece of work, based on authors' review, a series of limiting factors as the regulatory framework and guidelines are identified and discussed, while it is highlighted that revolutionary advances in the biomedical field such as 3D-printing technology and microfluidics will contribute to accelerate the clinical translation of nanoparticle-microneedle-based devices and make possible their use and entrance to the biomedical market.

Recent advances in cutaneous drug delivery by iontophoresis

INTRODUCTION

Iontophoresis has been extensively studied for topical and transdermal drug delivery to stimulate the absorption of molecules that would hardly pass through the outermost layer of the skin passively. Recent research has focused on its combination with nanoparticle-based systems or microneedles to expand its therapeutic applications.

AREAS COVERED

This review explores the fundamental principles of iontophoresis, focusing on key factors influencing its drug transport mechanisms, and provides a discussion of the field's current state. A comprehensive analysis of articles published or available online in 2024 was conducted, categorizing studies by their application areas, drug delivery systems, iontophoretic conditions, and experimental limitations.

EXPERT OPINION

The findings reveal a recent focus on wound healing and skin repair, and advancements in treating inflammation, pain, and skin cancer. Market translation requires standardized experimental protocols, particularly for iontophoretic parameters and preclinical models, along with the development of cost-effective commercial devices. Additionally, while advancements in cutaneous drug delivery have increasingly benefited from machine learning approaches, their application to iontophoresis remains underexplored. With the growing interest in associating iontophoresis with the Internet of Things, such an integration, if combined with AI tools, could offer promising opportunities for personalized, real-time treatments in modern dermatology, and therapeutic systems.

Novel strategies in topical delivery for psoriasis treatment: nanocarriers and energy-driven approaches

INTRODUCTION

Psoriasis is characterized by abnormal differentiation and hyperproliferation of epidermal keratinocytes. This condition presents significant challenges for effective drug delivery. In addition to overcoming the thickness of the skin, topical treatments must navigate the complex hydrophobic and hydrophilic properties of the skin barrier. Recent advancements in nanocarrier technologies, including energy-driven methods and microneedles that penetrate the stratum corneum, present promising strategies for enhancing drug permeation through tailored physicochemical properties. A literature search was performed using the databases of Google Scholar, PubMed, and ScienceDirect.

AREAS COVERED

This review highlights recent studies on novel topical delivery methods for psoriasis treatment, addressing current therapeutic options and their limitations. We provide a comprehensive overview of chemical nanoformulations and explore physical strategies to improve delivery rates. Furthermore, we discuss the advantages of various formulations that can carry different types of payloads, offering patients diverse strategies for symptom management. The review covers conventional treatments, emphasizing advancements in nanoparticle design and novel macromolecular drugs. This includes Ribonucleic acid (RNA)-based therapies that protect macromolecular drugs from rapid clearance in the body.

EXPERT OPINION

We argue that intelligent design approaches can enhance efficacy across delivery applications while allowing for precision in treatment strategies, ultimately improving patient outcomes.

Current Strategies and Future Directions of Wearable Biosensors for Measuring Stress Biochemical Markers for Neuropsychiatric Applications

Most wearable biosensors aimed at capturing psychological state target stress biomarkers in the form of physical symptoms that can correlate with dysfunction in the central nervous system (CNS). However, such markers lack the specificity needed for diagnostic or preventative applications. Wearable biochemical sensors (WBSs) have the potential to fill this gap, however, the technology is still in its infancy. Most WBSs proposed thus far target cortisol. Although cortisol detection is demonstrated as a viable method for approximating the extent and severity of psychological stress, the hormone also lacks specificity. Multiplex WBSs that simultaneously target cortisol alongside other viable stress-related biochemical markers (SBMs) can prove to be indispensable for understanding how psychological stress contributes to the pathophysiology of neuropsychiatric illnesses (NPIs) and, thus, lead to the discovery of new biomarkers and more objective clinical tools. However, none target more than one SBM implicated in NPIs. Till this review, cortisol's connection to dysfunctions in the CNS, to other SBMs, and their implication in various NPIs has not been discussed in the context of developing WBS technology. As such, this review is meant to inform the biosensing and neuropsychiatric communities of viable future directions and possible challenges for WBS technology for neuropsychiatric applications.

Transdermal Delivery of Botulinum Neurotoxin A: A Novel Formulation with Therapeutic Potential

BACKGROUND

Botulinum neurotoxin is widely regarded as a "wonder medicine" due to its therapeutic efficacy in treating a variety of conditions. While it is traditionally classified as a neurotoxin, it is arguably more appropriate to refer to it as a neuromedicine. All FDA-approved formulations of botulinum neurotoxin are currently administered through intramuscular injections, with no other delivery methods widely used. The primary reasons for this include the following: (a) the extremely high potency of the toxin, (b) the potential for diffusion to adjacent muscles, (c) factors related to the site of administration (e.g., muscle thickness), (d) the large size of the molecule, (e) the impermeability of skin to large protein molecules, and (f) safety concerns. Despite these challenges, there is growing interest in the development of an effective transdermal formulation of botulinum neurotoxin. Refining and standardizing the delivery technology for topical or transdermal use remains an important goal for the future.

METHODS

The aim of this study was to develop a nanoemulsion-based transdermal formulation capable of delivering active botulinum neurotoxin (BoNT) through human skin. The goal was to demonstrate its efficacy in a mouse model, highlighting the therapeutic effects on both neuromuscular activity and hyperhidrosis. We successfully developed a nanoemulsion-based formulation that facilitates the transdermal delivery of BoNT. The formulation was homogeneous, stable, and efficacious. In a mouse model, we evaluated the neurotoxin's impact on neuromuscular function using the Digital Abduction Score (DAS) for toe-spread and rota-rod assay to assess motor coordination.

RESULTS

The results confirmed the successful paralytic effect of the neuotoxin. The formulation significantly reduced sweating in the hyperhidrosis mouse model, indicating the therapeutic potential for this indication. Beyond the neurotoxin's paralyzing effect, we also observed the recovery of nerve function, showing that the neurotoxin does not cause permanent damage, further underscoring its safety and efficacy.

CONCLUSIONS

This formulation is the first of its kind to successfully deliver a large biomolecule like BoNT across the skin and produce a therapeutic effect. The ability to deliver large biomolecules transdermally has the potential to serve as a platform technology for treating a variety of conditions, including neuromuscular disorders, skin conditions, and localized pain management.

Approaches and applications in transdermal and transpulmonary gene drug delivery

Gene therapy has emerged as a pivotal component in the treatment of diverse genetic and acquired human diseases. However, effective gene delivery remains a formidable challenge to overcome. The presence of degrading enzymes, acidic pH conditions, and the gastrointestinal mucus layer pose significant barriers for genetic therapy, necessitating exploration of alternative therapeutic options. In recent years, transdermal and transpulmonary gene delivery modalities offer promising avenues with multiple advantages, such as non-invasion, avoided liver first-pass effect and improved patient compliance. Considering the rapid development of gene therapeutics via transdermal and transpulmonary administration, here we aim to summarize the nearest advances in transdermal and transpulmonary gene drug delivery. In this review, we firstly elaborate on current delivery carrier in gene therapy. We, further, describe approaches and applications for enhancing transdermal and transpulmonary gene delivery encompassing microneedles, chemical enhancers, physical methods for transdermal administration as well as nebulized formulations, dry powder formulations, and pressurized metered dose formulations for efficient transpulmonary delivery. Last but not least, the opportunities and outlooks of gene therapy through both administrated routes are highlighted.

Peptides: Emerging Candidates for the Prevention and Treatment of Skin Senescence: A Review

One class of cosmetic compounds that have raised interest of many experts is peptides. The search for ingredients with good biocompatibility and bioactivity has led to the use of peptides in cosmetic products. Peptides are novel active ingredients that improve collagen synthesis, enhance skin cell proliferation, or decrease inflammation. Based on their mechanism of action, they can be classified into signal peptides, carrier peptides, neurotransmitter inhibitor peptides, and enzyme inhibitor peptides. This review focuses on the main types of peptides and their application in the cosmetic field, underlining their main limitations. One of the most significant drawbacks of cosmetic peptides is their poor permeability through membranes, which limits their delivery and effectiveness. As a result, this review follows the methods used for improving permeability through the stratum corneum. Increasing peptide bioavailability and stability for enhanced delivery to the desired site of action and visible effects have become central points for the latest research due to their promising features. For this purpose, several methods have been identified and described. Physical techniques include thermal ablation (radiofrequency and laser), electrical methods (electroporation, iontophoresis), mechanical approach (microneedles), and ultrasounds. As an alternative, innovative formulations have been developed in nano-systems such as liposomes, niosomes, ethosomes, nanoemulsions, and other nanomaterials to reduce skin irritation and improve product effectiveness. The purpose of this review is to provide the latest information regarding these noteworthy molecules and the reasoning behind their use in cosmetic formulations.

Transdermal Drug Delivery Systems: Different Generations and Dermatokinetic Assessment of Drug Concentration in Skin

Transdermal drug delivery systems (TDDS) are a highly appealing and innovative method of administering drugs through the skin, as it enables the drugs to achieve systemic effects. A TDDS offers patient convenience, avoids first-pass hepatic metabolism, enables local targeting, and reduces the toxic effect of drug. This review details several generations of TDDS and the advancements made in their development to address the constraints associated with skin delivery systems. Transdermal delivery methods of the first generation have been consistently growing in their clinical application for administering small, lipophilic, low-dose drugs. Second-generation TDDS, utilizing chemical enhancers and iontophoresis, have led to the development of clinical products. Third-generation delivery systems employ microneedles, thermal ablation, and electroporation to specifically target the stratum corneum, which is the skin's barrier layer. Dermatokinetics is the study of the movement of drugs and formulations applied to the skin over a period of time. It provides important information regarding the rate and extent to which drugs penetrate skin layers. Several dermatokinetic techniques, including tape stripping, microdialysis, and laser scanning microscopy, have been used to study the intricate barrier properties and clearance mechanisms of the skin. This understanding is essential for developing and improving effective TDDS.

Non-Invasive Delivery of Negatively Charged Nanobodies by Anodal Iontophoresis: When Electroosmosis Dominates Electromigration

Iontophoresis enables the non-invasive transdermal delivery of moderately-sized proteins and the needle-free cutaneous delivery of antibodies. However, simple descriptors of protein characteristics cannot accurately predict the feasibility of iontophoretic transport. This study investigated the cathodal and anodal iontophoretic transport of the negatively charged M7D12H nanobody and a series of negatively charged variants with single amino acid substitutions. Surprisingly, M7D12H and its variants were only delivered transdermally by anodal iontophoresis. In contrast, transdermal permeation after cathodal iontophoresis and passive diffusion was Collapse

Key Words

• anti-EGFR 7D12 nanobody
• electroosmosis
• iontophoresis
• nanobodies
• protein expression and purification
• skin topical and transdermal delivery

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Affiliation(s)

Phedra Firdaws Sahraoui School of Pharmaceutical Sciences, University of Geneva, CMU-1 Rue Michel Servet, 1211 Geneva, Switzerland; Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU-1 Rue Michel Servet, 1211 Geneva, Switzerland
Oscar Vadas Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, CMU-1 Rue Michel Servet, 1211 Geneva, Switzerland;
Yogeshvar N. Kalia School of Pharmaceutical Sciences, University of Geneva, CMU-1 Rue Michel Servet, 1211 Geneva, Switzerland; Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU-1 Rue Michel Servet, 1211 Geneva, Switzerland

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Comparative evaluation of physical and chemical enhancement techniques for transdermal delivery of linagliptin

Linagliptin is a dipeptidyl peptidase-4 inhibitor used for the management of type-2 diabetes. US FDA-approved products are available exclusively as oral tablets. The inherent drawbacks of the oral administration route necessitate exploring delivery strategies via other routes. In this study, we investigated the feasibility of transdermal administration of linagliptin through various approaches. We compared chemical penetration enhancers (oleic acid, oleyl alcohol, and isopropyl myristate) and physical enhancement techniques (iontophoresis, sonophoresis, microneedles, laser, and microdermabrasion) to understand their potential to improve transdermal delivery of linagliptin. To our knowledge, this is the first reported comparison of chemical and physical enhancement techniques for the transdermal delivery of a moderately lipophilic molecule. All physical enhancement techniques caused a significant reduction in the transepithelial electrical resistance of the skin samples. Disruption of the skin's structure post-treatment with physical enhancement techniques was further confirmed using characterization techniques such as dye binding, histology, and confocal microscopy. In vitro permeation testing (IVPT) demonstrated that the passive delivery of linagliptin across the skin was < 5 µg/sq.cm. Two penetration enhancers - oleic acid (93.39 ± 8.34 µg/sq.cm.) and oleyl alcohol (424.73 ± 42.86 µg/sq.cm.), and three physical techniques - iontophoresis (53.05 ± 0.79 µg/sq.cm.), sonophoresis (141.13 ± 34.22 µg/sq.cm.), and laser (555.11 ± 78.97 µg/sq.cm.) exceeded the desired target delivery for therapeutic effect. This study established that linagliptin is an excellent candidate for transdermal delivery and thoroughly compared chemical penetration and physical transdermal delivery strategies.

Smart Physical-Based Transdermal Drug Delivery System:Towards Intelligence and Controlled Release

Transdermal drug delivery systems based on physical principles have provided a stable, efficient, and safe strategy for disease therapy. However, the intelligent device with real-time control and precise drug release is required to enhance treatment efficacy and improve patient compliance. This review summarizes the recent developments, application scenarios, and drug release characteristics of smart transdermal drug delivery systems fabricated with physical principle. Special attention is paid to the progress of intelligent design and concepts in of physical-based transdermal drug delivery technologies for real-time monitoring and precise drug release. In addition, facing with the needs of clinical treatment and personalized medicine, the recent progress and trend of physical enhancement are further highlighted for transdermal drug delivery systems in combination with pharmaceutical dosage forms to achieve better transdermal effects and facilitate the development of smart medical devices. Finally, the next generation and future application scenarios of smart physical-based transdermal drug delivery systems are discussed, a particular focus in vaccine delivery and tumor treatment.

Development of an Effective Psoriasis Treatment by Combining Tacrolimus-Encapsulated Liposomes and Iontophoresis

Psoriasis is a chronic T-cell-mediated autoimmune skin disease. Tacrolimus (FK506) is commonly used treatment for psoriasis. However, since the molecular weight of FK506 is more than 500 Da, its skin penetration is limited, so that there is a need to improve the penetrability of FK506 to allow for more effective treatment. To this end, we employed iontophoresis (ItP), which is a physical, intradermal drug delivery technology that relies on the use of weak electric current. Previous findings suggest that activation of cell signaling by the weak electric current applied during ItP may affect the expression of inflammatory cytokines, leading to aggravation of psoriasis. In this study, we analyzed the effect of ItP on the expression of various inflammatory cytokines in the skin, and subsequently examined the therapeutic effect of ItP using negatively-charged liposomes encapsulating FK506 (FK-Lipo) in a rat psoriasis model induced by imiquimod. We found that ItP (0.34 mA/cm2, 1 h) did not affect mRNA levels of inflammatory cytokines or epidermis thickness, indicating that ItP is a safe technology for psoriasis treatment. ItP of FK-Lipo suppressed the expression of inflammatory cytokines induced by imiquimod treatment to a greater extent than skin treated with FK506 ointment for 1 h. Furthermore, epidermis thickening was significantly suppressed only by ItP of FK-Lipo. Taken together, results of this study demonstrate the successful development of an efficient treatment for psoriasis by combining FK-Lipo and ItP, without disease aggravation associated with the weak electric current.

Intradermal Delivery of Naked mRNA Vaccines via Iontophoresis

Messenger RNA (mRNA) vaccines against infectious diseases and for anticancer immunotherapy have garnered considerable attention. Currently, mRNA vaccines encapsulated in lipid nanoparticles are administrated via intramuscular injection using a needle. However, such administration is associated with pain, needle phobia, and lack of patient compliance. Furthermore, side effects such as fever and anaphylaxis associated with the lipid nanoparticle components are also serious problems. Therefore, noninvasive, painless administration of mRNA vaccines that do not contain other problematic components is highly desirable. Antigen-presenting cells reside in the epidermis and dermis, making the skin an attractive vaccination site. Iontophoresis (ItP) uses weak electric current applied to the skin surface and offers a noninvasive permeation technology that enables intradermal delivery of hydrophilic and ionic substances. ItP-mediated intradermal delivery of biological macromolecules has also been studied. Herein, we review the literature on the use of ItP technology for intradermal delivery of naked mRNA vaccines which is expected to overcome the challenges associated with mRNA vaccination. In addition to the physical mechanism, we discuss novel biological mechanisms of iontophoresis, particularly ItP-mediated opening of the skin barriers and the intracellular uptake pathway, and how the combined mechanisms can allow for effective intradermal delivery of mRNA vaccines.

Up-to-date molecular medicine strategies for management of ocular surface neovascularization

Ocular surface neovascularization and its resulting pathological changes significantly alter corneal refraction and obstruct the light path to the retina, and hence is a major cause of vision loss. Various factors such as infection, irritation, trauma, dry eye, and ocular surface surgery trigger neovascularization via angiogenesis and lymphangiogenesis dependent on VEGF-related and alternative mechanisms. Recent advances in antiangiogenic drugs, nanotechnology, gene therapy, surgical equipment and techniques, animal models, and drug delivery strategies have provided a range of novel therapeutic options for the treatment of ocular surface neovascularization. In this review article, we comprehensively discuss the etiology and mechanisms of corneal neovascularization and other types of ocular surface neovascularization, as well as emerging animal models and drug delivery strategies that facilitate its management.

Transdermal Delivery of Insulin Using Combination of Iontophoresis and Deep Eutectic Solvents as Chemical Penetration Enhancers: In Vitro and in Vivo Evaluations

A serious challenge in transdermal iontophoresis (IP) delivery of insulin (INS) is the low permeability of the drug across the skin. In this paper, we introduced deep eutectic solvent (DESs) as novel chemical penetration enhancers (CPEs) for transdermal IP of INS across rat skin, both in vitro and in vivo. Three different DESs based on choline chloride (ChCl), namely, ChCl/UR (ChCl and urea), ChCl/GLY (ChCl and glycerol), and ChCl/EG (ChCl and ethylene glycol) in the 1:2 molar ratios have been prepared. To evaluate the capability of studied DESs as CPEs for IP delivery of INS, the rat skin sample was treated with each DES. The effects of different experimental parameters (current density, formulation pH, INS concentration, NaCl concentration, and treatment time) on the in vitro transdermal iontophoretic delivery of INS were investigated. The in vitro permeation studies exhibited that INS was easily delivered employing ChCl/EG, and ChCl/GLY treatments, compared with ChCl/UR: the cumulative amount of permeated INS at the end of the experiment (Q24h) was found to be 131.0, 89.4, and 29.6 µg cm-2 in the presence of ChCl/EG, ChCl/GLY, and ChCl/UR, respectively. The differences in Q24h values of INS are due to the different capabilities of the studied DESs to treat the epidermis layer of skin. In vivo experiments revealed that the blood glucose level in diabetic rats could be decreased using ChCl/EG, and ChCl/GLY as novel CPEs in the IP delivery of INS. The presented work will open new doors towards searching for novel CPEs in the development of transdermal IP of INS.

Increasing Skeletal Muscle Mass in Mice by Non-Invasive Intramuscular Delivery of Myostatin Inhibitory Peptide by Iontophoresis

Sarcopenia is a major public health issue that affects older adults. Myostatin inhibitory-D-peptide-35 (MID-35) can increase skeletal muscle and is a candidate therapeutic agent, but a non-invasive and accessible technology for the intramuscular delivery of MID-35 is required. Recently, we succeeded in the intradermal delivery of various macromolecules, such as siRNA and antibodies, by iontophoresis (ItP), a non-invasive transdermal drug delivery technology that uses weak electricity. Thus, we expected that ItP could deliver MID-35 non-invasively from the skin surface to skeletal muscle. In the present study, ItP was performed with a fluorescently labeled peptide on mouse hind leg skin. Fluorescent signal was observed in both skin and skeletal muscle. This result suggested that the peptide was effectively delivered to skeletal muscle from skin surface by ItP. Then, the effect of MID-35/ItP on skeletal muscle mass was evaluated. The skeletal muscle mass increased 1.25 times with ItP of MID-35. In addition, the percentage of new and mature muscle fibers tended to increase, and ItP delivery of MID-35 showed a tendency to induce alterations in the levels of mRNA of genes downstream of myostatin. In conclusion, ItP of myostatin inhibitory peptide is a potentially useful strategy for treating sarcopenia.

Permeation Effect Analysis of Drug Using Raman Spectroscopy for Iontophoresis

Iontophoresis technology could improve the efficiency of transdermal drug delivery through the skin and be a promising prospective tool for clinical drug therapy in the near future. Surface-enhanced Raman spectroscopy (SERS) was used to analyze the concentration distribution of penicillin sodium in the skin of a mice model, and the iontophoresis delivery efficiency of drug percutaneous permeation was evaluated with various times and concentrations of penicillin sodium through Raman spectra. The results showed both the action time and drug concentration for iontophoresis can deeply influence transdermal drug delivery effects, and the Raman spectrum might be an effective method to evaluate transdermal drug delivery efficiency.