Iontophoresis and electroporation: comparisons and contrasts

An Outlook on Platinum-Based Active Ingredients for Dermatologic and Skincare Applications

Platinum-based materials exhibit a broad spectrum of biological activities, including antioxidant, anti-inflammatory, antimicrobial, and pro-collagen synthesis properties, making them particularly useful for various biomedical applications. This review summarizes the biological effects and therapeutic potential of platinum-based active ingredients in dermatological and skincare applications. We discuss their synthesis methods and their antioxidant, anti-inflammatory, antimicrobial, and collagen synthesis properties, which play essential roles in treating skin conditions including psoriasis and acne, as well as enhancing skin aesthetics in anti-aging products. Safety and sustainability concerns, including the need for green synthesis and comprehensive toxicological assessments to ensure safe topical applications, are also discussed. By providing an up-to-date overview of current research, we aim to highlight both the potential and the current challenges of platinum-based active ingredients in advancing dermatology and skincare solutions.

Electrofluidic control for textile-based cell culture: Identification of appropriate conditions required to integrate cell culture with electrofluidics

Electric field-driven microfluidics, known as electrofluidics, is a novel attractive analytical tool when it is integrated with low-cost textile substrate. Textile-based electrofluidics, primarily explored on yarn substrates, is in its early stages, with few studies on 3D structures. Further, textile structures have rarely been used in cellular analysis as a low-cost alternative. Herein, we investigated novel 3D textile structures and develop optimal electrophoretic designs and conditions that are favourable for direct 3D cell culture integration, developing an integrated cell culture textile-based electrofluidic platform that was optimised to balance electrokinetic performance and cell viability requirements. Significantly, there were contrasting electrolyte compositional conditions that were required to satisfy cell viability and electrophoretic mobility requiring the development of and electrolyte that satisfied the minimum requirements of both these components within the one platform. Human dermal fibroblast cell cultures were successfully integrated with gelatine methacryloyl (GelMA) hydrogel-coated electrofluidic platform and studied under different electric fields using 5 mM TRIS/HEPES/300 mM glucose. Higher analyte mobility was observed on 2.5% GelMA-coated textile which also facilitated excellent cell attachment, viability and proliferation. Cell viability also increased by decreasing the magnitude and time duration of applied electric field with good cell viability at field of up to 20 V cm-1.

Advancements in Skin-Mediated Drug Delivery: Mechanisms, Techniques, and Applications

Skin-mediated drug delivery methods currently are receiving significant attention as a promising approach for the enhanced delivery of drugs through the skin. Skin-mediated drug delivery offers the potential to overcome the limitations of traditional drug delivery methods, including oral administration and intravenous injection. The challenges associated with drug permeation through layers of skin, which act as a major barrier, are explored, and strategies to overcome these limitations are discussed in detail. This review categorizes skin-mediated drug delivery methods based on the means of increasing drug permeation, and it provides a comprehensive overview of the mechanisms and techniques associated with these methods. In addition, recent advancements in the application of skin-mediated drug delivery are presented. The review also outlines the limitations of ongoing research and suggests future perspectives of studies regarding the skin-mediated delivery of drugs.

Smartphone-based iontophoresis transdermal drug delivery system for cancer treatment

Cancer is a leading cause of the death worldwide. However, the conventional cancer therapy still suffers from several limitations, such as systemic side effects, poor efficacy, and patient compliance due to limited accessibility to the tumor site. To address these issues, the localized drug delivery system has emerged as a promising approach. In this study, we developed an iontophoresis-based transdermal drug delivery system (TDDS) controlled by a smartphone application for cancer treatment. Iontophoresis, a low-intensity electric current-based TDDS, enhances drug permeation across the skin to provide potential for localized drug delivery and minimize systemic side effects. The fundamental mechanism of our system was modeled using finite element analysis and its performance was corroborated through the flow-through skin permeation tests using a plastic-based microfluidic chip. The results of in vitro cell experiments and skin deposition tests successfully demonstrated that our smartphone-controlled iontophoresis system significantly enhanced the drug permeation for cancer treatment. Therefore, this hand-held smartphone-based iontophoresis TDDS could be a powerful tool for self-administrated anticancer drug delivery applications.

Evolution of Transdermal Drug Delivery Devices and Novel Microneedle Technologies: A Historical Perspective and Review

The history of transdermal drug delivery is as old as humankind. Transdermal drug delivery has undergone three generations of development; the third generation has involved the use of medical devices and instruments. This review provides a historical perspective on the primary approaches employed in the three generations of transdermal drug delivery. In addition, we explore some of the recently developed transdermal techniques that are deemed promising in the field of drug delivery. We discuss how advances in these techniques have led to the development of devices for the delivery of a therapeutically effective amount of drug across human skin and highlight the limitations of the first- and second-generation drug delivery tools. As such, a review of the performance of these techniques and the toxicity of the devices used in transdermal drug delivery are considered. In the last section of the review, a discussion of the fabrication and operation of different types of microneedles is presented. The applications of microneedles in the sensing and delivery of various therapeutic agents are described in detail. Furthermore, an overview of the efficacy of microneedles as emerging tools for the controlled release of drugs is presented.

Transdermal drug delivery via microneedles for musculoskeletal systems

As the population is ageing and lifestyle is changing, the prevalence of musculoskeletal (MSK) disorders is gradually increasing with each passing year, posing a serious threat to the health and quality of the public, especially the elderly. However, currently prevalent treatments for MSK disorders, mainly administered orally and by injection, are not targeted to the specific lesion, resulting in low efficacy along with a series of local and systemic adverse effects. Microneedle (MN) patches loaded with micron-sized needle array, combining the advantages of oral administration and local injection, have become a potentially novel strategy for the administration and treatment of MSK diseases. In this review, we briefly introduce the basics of MNs and focus on the main characteristics of the MSK systems and various types of MN-based transdermal drug delivery (TDD) systems. We emphasize the progress and broad applications of MN-based transdermal drug delivery (TDD) for MSK systems, including osteoporosis, nutritional rickets and some other typical types of arthritis and muscular damage, and in closing summarize the future prospects and challenges of MNs application.

Wearable patches for transdermal drug delivery

Transdermal drug delivery systems (TDDs) avoid gastrointestinal degradation and hepatic first-pass metabolism, providing good drug bioavailability and patient compliance. One emerging type of TDDs is the wearable patch worn on the skin surface to deliver medication through the skin. They can generally be grouped into passive and active types, depending on the properties of materials, design principles and integrated devices. This review describes the latest advancement in the development of wearable patches, focusing on the integration of stimulus-responsive materials and electronics. This development is deemed to provide a dosage, temporal, and spatial control of therapeutics delivery.

Recent Advances in Oral and Transdermal Protein Delivery Systems

Protein and peptide drugs are predominantly administered by injection to achieve high bioavailability, but this greatly compromises patient compliance. Oral and transdermal drug delivery with minimal invasiveness and high adherence represent attractive alternatives to injection administration. However, oral and transdermal administration of bioactive proteins must overcome biological barriers, namely the gastrointestinal and skin barriers, respectively. The rapid development of new materials and technologies promises to address these physiological obstacles. This review provides an overview of the latest advances in oral and transdermal protein delivery, including chemical strategies, synthetic nanoparticles, medical microdevices, and biomimetic systems for oral administration, as well as chemical enhancers, physical approaches, and microneedles in transdermal delivery. We also discuss challenges and future perspectives of the field with a focus on innovation and translation.

Electromotive Enhanced Drug Administration in Oncology: Principles, Evidence, Current and Emerging Applications

Local-regional administration of cytotoxic drugs is an important adjunct to systemic chemotherapy amongst cancer patients. It allows for targeted delivery of agents at high concentration to target sites while minimizing systemic side effects. Despite the pharmacokinetic advantages of the local-regional approach, drug transport into tumor nodules remains limited due to the biophysical properties of these tissues. Electromotive enhanced drug administration (EMDA) represents a potential solution to overcome challenges in local drug transport by applying electric currents. Through electrokinetic phenomena of electromigration, electroosmosis and electroporation, electric currents have been shown to improve drug penetration and distribution in a wide variety of clinical applications. Amongst patients with non-muscular invasive bladder cancer (NMIBC) and basal and squamous cell skin cancers, EMDA has been successfully adopted and proven efficacious in several pre-clinical and clinical studies. Its application in ophthalmological and other conditions has also been explored. This review provides an overview of the underlying principles and factors that govern EMDA and discusses its application in cancer patients. We also discuss novel EMDA approaches in pre-clinical studies and explore future opportunities of developments in this field.

Application of microneedle patches for drug delivery; doorstep to novel therapies

In the past decade, microneedle-based drug delivery systems showed promising approaches to become suitable and alternative for hypodermic injections and can control agent delivery without side effects compared to conventional approaches. Despite these advantages, the procedure of microfabrication is facing some difficulties. For instance, drug loading method, stability of drugs, and retention time are subjects of debate. Besides, the application of novel refining fabrication methods, types of materials, and instruments are other issues that need further attention. Herein, we tried to summarize recent achievements in controllable drug delivery systems (microneedle patches) in vitro and in vivo settings. In addition, we discussed the influence of delivered drugs on the cellular mechanism and immunization molecular signaling pathways through the intradermal delivery route. Understanding the putative efficiency of microneedle patches in human medicine can help us develop and design sophisticated therapeutic modalities.

Transdermal Delivery of Baclofen Using Iontophoresis and Microneedles

Baclofen, a GABA_b agonist, is used in the treatment of multiple sclerosis, a neurodegenerative disease. Currently available dosage forms to deliver baclofen are through the oral and the intrathecal routes. The disadvantage of oral baclofen is that it requires administering the drug multiple times a day, owing to baclofen's short half-life. On the other hand, intrathecal baclofen pumps are invasive and cannot be an alternative to oral baclofen. Hence, there is a need to develop a dosage form that can deliver baclofen non-invasively and for an extended period at a steady rate, increasing the dosing interval. A transdermal baclofen delivery system might be the solution to this problem. Hence, this research focuses on evaluating microneedles, iontophoresis, and a combination of microneedles-iontophoresis as transdermal delivery enhancement strategies for baclofen. In vitro permeation studies were conducted on dermatomed porcine ear skin using vertical Franz diffusion cells to evaluate transdermal baclofen delivery. Anodal iontophoresis was applied at a current density of 0.5 mA/cm², and transdermal delivery was assessed from pH 4.5 (45.51±0.76 μg/cm²) and pH 7.4 (68.84±10.13 μg/cm²) baclofen solutions. Iontophoresis enhanced baclofen delivery but failed to reach target delivery. Maltose microneedles were used to create hydrophilic microchannels on the skin, and this technique enhanced baclofen delivery by 89-fold. Both microneedles (447.88±68.06 μg/cm²) and combination of microneedles - iontophoresis (428.56±84.33 μg/cm²) reached the target delivery range (222-1184 μg/cm²) for baclofen. The findings of this research suggest that skin could be a viable route for delivery of baclofen. Graphical Abstract.

Iontophoresis of Biological Macromolecular Drugs

Over the last few decades, biological macromolecular drugs (e.g., peptides, proteins, and nucleic acids) have become a significant therapeutic modality for the treatment of various diseases. These drugs are considered superior to small-molecule drugs because of their high specificity and favorable safety profiles. However, such drugs are limited by their low oral bioavailability and short half-lives. Biological macromolecular drugs are typically administrated via invasive methods, e.g., intravenous or subcutaneous injections, which can be painful and induce needle phobia. Noninvasive transdermal delivery is an alternative administration route for the local and systemic delivery of biological macromolecular drugs. However, a challenge with the noninvasive transdermal delivery of biological macromolecular drugs is the outermost layer of the skin, known as the stratum corneum, which is a physical barrier that restricts the entry of extraneous macromolecules. Iontophoresis (IP) relies on the application of a low level of electricity for transdermal drug delivery, in order to facilitate the skin permeation of hydrophilic and charged molecules. The IP of several biological macromolecular drugs has recently been investigated. Herein, we review the IP-mediated noninvasive transdermal delivery of biological macromolecular drugs, their routes of skin permeation, their underlying mechanisms, and their advance applications.

Numerical simulation of iontophoresis for in-silico prediction of transdermal drugs in the dermal layers using skin impedance values

BACKGROUND AND OBJECTIVE

Transdermal delivery of a therapeutic drug is a non-invasive method of drug administration. For a controlled delivery of the maximum number of drugs, several external enhancement mechanisms are used in the domain of transdermal drug delivery (TDD). Iontophoresis is one of the processes which uses a weak electric current to increase drug delivery and electrically control its penetration into the body. This method is governed by the Nernst-Planck equation, which gives the total flux of administering drugs due to iontophoresis. In this work, an effort has been made to simulate iontophoresis to predict transdermal drugs in the dermal layers using electrical equivalent skin models.

METHODS

As the executable route of drug administration is skin, the electrical impedance value of the dermal layers can be utilized in predicting the amount of iontophoretic drug flux by introducing impedance parameters of skin in the Nernst-Planck equation. Researchers have developed electrical equivalent models of skin that explain the skin's physiological stratification and biological properties.

RESULTS

Numerical simulation of iontophoresis is performed using the human skin impedance values with these impedance models of skin to predict drug concentrations in the dermal layers. For the computation and analysis of drug delivery using simulations, boundary conditions were developed based on the descriptions of the electrical impedance models and the morphology of human skin.

CONCLUSIONS

This proposed method establishes a clear relationship between TDD and skin impedance. It could be used in in-silico prediction before experimentation of any drugs on live animals or humans. The adopted methodology could be implemented in programming to develop software for real-time prediction of transdermal drugs in dermal layers using instantaneous skin impedance values. Further researchers can work upon this idea to include more natural constraints that identify complex biological features of the skin and physio-chemical properties of drugs.

Tuning the transdermal transport by application of external continuous electric field: a coarse-grained molecular dynamics study

The control of skin permeability to specific substances (e.g., medications, vitamins, and nutrients) through stratum corneum is a challenge. Iontophoresis is an option in spite of the lack of a detailed understanding of the underlying molecular mechanism. In the present work, the simulations concerning application of an external continuous electric field to stratum corneum, in a range of low intensity (0-24 mV nm^-1), were carried out using the coarse-grained molecular dynamics approach. Using a set of random seed replicas of the starting configuration, we observed that in the range of electric field intensity of 22-23 mV nm^-1, water-rich lipid vesicles were formed in 20% of cases. Pores appeared in the remaining 80%. We argue that lipids undergo fast re-orientations under electric field inducing mechanical instability, which originates the pores. We presented a simple electrostatic model to interpret the results where the mismatch between electrical permittivities of the membrane and external media and the gradient of the local electric field in the membrane surface, govern the time scales and electric fields for vesicle formation. Our results indicate that just 10% difference between electrical permittivities of the membrane and external media decreases 1/6 the minimal time required for vesicle formation. The minimal electric field required decreases 10 times. The control and tunning of formation of biologically compatible vesicles, capable of transporting substances under low-intensity electric fields, has a promising application in fields such as drug therapy and dermo-cosmetics allowing the use of hydrophilic substances in dermal applications.

Skin Penetration Enhancement Strategies Used in the Development of Melanoma Topical Treatments

Malignant melanoma is an aggressive form of skin cancer for which there is currently no reliable therapy and is considered one of the leading health issues in the USA. At present, surgery is the most effective and acceptable treatment; however, surgical excision can be impractical in certain circumstances. Topical skin delivery of drugs using topical formulations is a potential alternative approach which can have many advantages aside from being a non-invasive delivery route. Nevertheless, the presence of the stratum corneum (SC) limits the penetration of drugs through the skin, lowering their treatment efficacy and raising concerns among physicians and patients as to their effectiveness. Currently, research groups are trying to circumvent the SC barrier by using skin penetration enhancement (SPE) strategies. The SPE strategies investigated include chemical skin penetration enhancers (CPEs), physical skin penetration enhancers (PPEs), nanocarrier systems, and a combination of SPE strategies (cream). Of these, PPEs and cream are the most advanced approaches in terms of preclinical and clinical studies, respectively.

Small interfering RNAs (siRNAs) based gene silencing strategies for the treatment of glaucoma: Recent advancements and future perspectives

RNA-interference-based mechanisms, especially the use of small interfering RNAs (siRNAs), have been under investigation for the treatment of several ailments and have shown promising results for ocular diseases including glaucoma. The eye, being a confined compartment, serves as a good target for the delivery of siRNAs. This review focuses on siRNA-based strategies for gene silencing to treat glaucoma. We have discussed the ocular structures and barriers to gene therapy (tear film, corneal, conjunctival, vitreous, and blood ocular barriers), methods of administration for ocular gene delivery (topical instillation, periocular, intracameral, intravitreal, subretinal, and suprachoroidal routes) and various viral and non-viral vectors in siRNA-based therapy for glaucoma. The components and mechanism of siRNA-based gene silencing have been mentioned briefly followed by the basic strategies and challenges faced during siRNA therapeutics development. We have emphasized different therapeutic targets for glaucoma which have been under research by scientists and the current siRNA-based drugs used in glaucoma treatment. We also mention briefly strategies for siRNA-based treatment after glaucoma surgery.

Engineering Antiviral Vaccines

Despite the vital role of vaccines in fighting viral pathogens, effective vaccines are still unavailable for many infectious diseases. The importance of vaccines cannot be overstated during the outbreak of a pandemic, such as the coronavirus disease 2019 (COVID-19) pandemic. The understanding of genomics, structural biology, and innate/adaptive immunity have expanded the toolkits available for current vaccine development. However, sudden outbreaks and the requirement of population-level immunization still pose great challenges in today's vaccine designs. Well-established vaccine development protocols from previous experiences are in place to guide the pipelines of vaccine development for emerging viral diseases. Nevertheless, vaccine development may follow different paradigms during a pandemic. For example, multiple vaccine candidates must be pushed into clinical trials simultaneously, and manufacturing capability must be scaled up in early stages. Factors from essential features of safety, efficacy, manufacturing, and distributions to administration approaches are taken into consideration based on advances in materials science and engineering technologies. In this review, we present recent advances in vaccine development by focusing on vaccine discovery, formulation, and delivery devices enabled by alternative administration approaches. We hope to shed light on developing better solutions for faster and better vaccine development strategies through the use of biomaterials, biomolecular engineering, nanotechnology, and microfabrication techniques.

Modeling iontophoretic drug delivery in a microfluidic device

Iontophoresis employs low-intensity electrical voltage and continuous constant current to direct a charged drug into a tissue. Iontophoretic drug delivery has recently been used as a novel method for cancer treatment in vivo. There is an urgent need to precisely model the low-intensity electric fields in cell culture systems to optimize iontophoretic drug delivery to tumors. Here, we present an iontophoresis-on-chip (IOC) platform to precisely quantify carboplatin drug delivery and its corresponding anti-cancer efficacy under various voltages and currents. In this study, we use an in vitro heparin-based hydrogel microfluidic device to model the movement of a charged drug across an extracellular matrix (ECM) and in MDA-MB-231 triple-negative breast cancer (TNBC) cells. Transport of the drug through the hydrogel was modeled based on diffusion and electrophoresis of charged drug molecules in the direction of an oppositely charged electrode. The drug concentration in the tumor extracellular matrix was computed using finite element modeling of transient drug transport in the heparin-based hydrogel. The model predictions were then validated using the IOC platform by comparing the predicted concentration of a fluorescent cationic dye (Alexa Fluor 594®) to the actual concentration in the microfluidic device. Alexa Fluor 594® was used because it has a molecular weight close to paclitaxel, the gold standard drug for treating TNBC, and carboplatin. Our results demonstrated that a 50 mV DC electric field and a 3 mA electrical current significantly increased drug delivery and tumor cell death by 48.12% ± 14.33 and 39.13% ± 12.86, respectively (n = 3, p-value <0.05). The IOC platform and mathematical drug delivery model of iontophoresis are promising tools for precise delivery of chemotherapeutic drugs into solid tumors. Further improvements to the IOC platform can be made by adding a layer of epidermal cells to model the skin.

Vaccination into the Dermal Compartment: Techniques, Challenges, and Prospects

In 2019, an 'influenza pandemic' and 'vaccine hesitancy' were listed as two of the top 10 challenges to global health by the WHO. The skin is a unique vaccination site, due to its immune-rich milieu, which is evolutionarily primed to respond to challenge, and its ability to induce both humoral and cellular immunity. Vaccination into this dermal compartment offers a way of addressing both of the challenges presented by the WHO, as well as opening up avenues for novel vaccine formulation and dose-sparing strategies to enter the clinic. This review will provide an overview of the diverse range of vaccination techniques available to target the dermal compartment, as well as their current state, challenges, and prospects, and touch upon the formulations that have been developed to maximally benefit from these new techniques. These include needle and syringe techniques, microneedles, DNA tattooing, jet and ballistic delivery, and skin permeabilization techniques, including thermal ablation, chemical enhancers, ablation, electroporation, iontophoresis, and sonophoresis.

Noninvasive transdermal delivery of liposomes by weak electric current

Noninvasive transdermal drug delivery (NTDD) offers an exciting new method of administration relative to conventional routes, but is associated with some challenges. Liposomes are capable of encapsulating transdermally-unfavorable drugs. However, the horny layer of skin is a significant barrier that limits efficient transdermal delivery of liposomes. Iontophoresis using weak electric current (WEC) represents a NTDD technology. WEC treatment of liposomes applied to the skin surface improves transdermal penetration of encapsulated drugs by cooperative effects. In this review, we provide an overview of the application of WEC/liposomes for transdermal delivery of macromolecules and low molecular weight drugs. We compare the transdermal delivery and therapeutic efficiency of the combined system with conventional routes of administration and their individual use. We discuss a novel perspective on the mechanism of WEC-mediated transdermal delivery of liposomes, which suggests that WEC activates the intracellular signaling pathway for transdermal permeation and induces unique endocytosis in skin cells.

Applications of cold atmospheric plasma for transdermal drug delivery: a review

Although transdermal drug delivery would be very useful for the treatment of many diseases, in practice it is difficult to accomplish for the obstruction of the stratum corneum. The application of cold atmospheric plasma (CAP) as a pretreatment to the skin surface helps to enhance the delivery of topically applied drugs into the skin and the systemic circulation. CAP can change the skin properties to improve drug penetration by various different effects based on its multiple components. This review first introduces the skin barrier properties and some traditional transdermal drug delivery strategies. Next what is known about the application of CAP in transdermal drug delivery has been summarized, including the mechanisms and possible side effects. We believe that CAP could be developed as a non-invasive and efficient pretreatment to improve the transdermal permeation of drugs in clinical practice, although more research needs to be done to overcome the challenges. Graphical Abstract.

Electroporation-enhanced transdermal drug delivery: Effects of logP, pKa, solubility and penetration time

Electroporation is an important physical technique to improve drug transdermal delivery, although its mechanism remains unclear. Here, some types of polar drugs, including aspirin, diclofenac sodium, metformin hydrochloride, ibuprofen and zidovudine, were used as the model drugs for the exploration of electroporation mechanisms. Electroporation had great influences on the structure of stratum corneum to improve the cumulative permeability due to the formation of pores maintaining for at least 2 h, depending on the power and time, and then the permeation gradually recovered to the normal value after 12 h. A mathematical model was firstly established to exhibit the relationship between the electroporation-improving cumulative permeation and the physiochemical properties of the model drugs, involving oil-water partition coefficient (logP), dissociation constant (pKa) and solubility (S). Increased cumulative permeation depended on increased S, decreased logP and pKa. Electroporation is an effective physical technique to improve transdermal drug delivery depending on itself and the properties of drugs.

Low Electric Treatment activates Rho GTPase via Heat Shock Protein 90 and Protein Kinase C for Intracellular Delivery of siRNA

Low electric treatment (LET) promotes intracellular delivery of naked siRNA by altering cellular physiology. However, which signaling molecules and cellular events contribute to LET-mediated siRNA uptake are unclear. Here, we used isobaric tags in relative and absolute quantification (iTRAQ) proteomic analysis to identify changes in the levels of phosphorylated proteins that occur during cellular uptake of siRNA promoted by LET. iTRAQ analysis revealed that heat shock protein 90 (Hsp90)α and myristoylated alanine-rich C-kinase substrate (Marcks) were highly phosphorylated following LET of NIH 3T3 cells, but not untreated cells. Furthermore, the levels of phosphorylated Hsp90α and protein kinase C (PKC)γ were increased by LET both with siRNA and liposomes having various physicochemical properties used as model macromolecules, suggesting that PKCγ activated partly by Ca²⁺ influx as well as Hsp90 chaperone function were involved in LET-mediated cellular siRNA uptake. Furthermore, LET with siRNA induced activation of Rho GTPase via Hsp90 and PKC, which could contribute to cellular siRNA uptake accompanied by actin cytoskeleton remodeling. Collectively, our results suggested that LET-induced Rho GTPase activation via Hsp90 and PKC would participate in actin-dependent cellular uptake of siRNA.

Current Advancements in Transdermal Biosensing and Targeted Drug Delivery

In this manuscript, recent advancements in the area of minimally-invasive transdermal biosensing and drug delivery are reviewed. The administration of therapeutic entities through the skin is complicated by the stratum corneum layer, which serves as a barrier to entry and retards bioavailability. A variety of strategies have been adopted for the enhancement of transdermal permeation for drug delivery and biosensing of various substances. Physical techniques such as iontophoresis, reverse iontophoresis, electroporation, and microneedles offer (a) electrical amplification for transdermal sensing of biomolecules and (b) transport of amphiphilic drug molecules to the targeted site in a minimally invasive manner. Iontophoretic delivery involves the application of low currents to the skin as well as the migration of polarized and neutral molecules across it. Transdermal biosensing via microneedles has emerged as a novel approach to replace hypodermic needles. In addition, microneedles have facilitated minimally invasive detection of analytes in body fluids. This review considers recent innovations in the structure and performance of transdermal systems.

Ionic Liquids as Potential and Synergistic Permeation Enhancers for Transdermal Drug Delivery

Transdermal drug delivery systems (TDDS) show clear advantages over conventional routes of drug administration. Nonetheless, there are limitations to current TDDS which warrant further research to improve current TDD platforms. Spurred by the synthesis of novel biodegradable ionic liquids (ILs) and favorable cytotoxicity studies, ILs were shown to be a possible solution to overcome these challenges. Their favorable application in overcoming challenges ranging from synthesis, manufacture, and even therapeutic benefits were documented. In this review, said ILs are highlighted and their role in TDDS is reviewed in terms of (a) ILs as permeation enhancers (single agents or combined), (b) ILs in drug modification, and (c) ILs as active pharmaceutical ingredients. Furthermore, future combination of ILs with other chemical permeation enhancers (CPEs) is proposed and discussed.

Overcoming ocular drug delivery barriers through the use of physical forces

Overcoming the physiological barriers in the eye remains a key obstacle in the field of ocular drug delivery. While ocular barriers naturally have a protective function, they also limit drug entry into the eye. Various pharmaceutical strategies, such as novel formulations and physical force-based techniques, have been investigated to weaken these barriers and transport therapeutic agents effectively to both the anterior and the posterior segments of the eye. This review summarizes and discusses the recent research progress in the field of ocular drug delivery with a focus on the application of physical methods, including electrical fields, sonophoresis, and microneedles, which can enhance penetration efficiency by transiently disrupting the ocular barriers in a minimally or non-invasive manner.

Enhanced transdermal delivery of ondansetron using nanovesicular systems: Fabrication, characterization, optimization and ex-vivo permeation study-Box-Cox transformation practical example

This study aimed to formulate suitable nanovesicles (NVs) for transdermal delivery of Ondansetron. It also illustrated a practical example for the importance of Box-Cox transformation. A 2³ full factorial design was used to enable testing transfersomes, ethosomes, and transethosomes of Ondansetron simultaneously. The independent variables (IVs) studied were sodium taurocholate amount, ethanol volume in hydration medium and sonication time. The studied dependent variables (DVs) were: particle size (PS), zeta potential (ZP) and entrapment efficiency (EE). Polynomial equations were used to study the influence of IVs on each DV. Numerical multiple response optimization was applied to select an optimized formula (OF) with the goals of minimizing PS and maximizing ZP absolute value and EE. Box-Cox transformation was adopted to enable modeling PS raised to the power of 1.2 with an excellent prediction R² of 1.000. ZP and EE were adequately represented directly with prediction R² of 0.9549 and 0.9892 respectively. Response surface plots helped in explaining the influence of IVs on each DV. Two-sided 95% prediction interval test and percent deviation of actual values from predicted ones proved the validity of the elucidated models. The OF was a transfersomal formula with desirability of 0.866 and showed promising results in ex-vivo permeation study.

Noninvasive penetration of 5 nm hyaluronic acid molecules across the epidermal barrier (in vitro) and its interaction with human skin cells

OBJECTIVE

Hyaluronic acid represents one of the major components of the extracellular environment. The main challenge remains in the ability to deliver these molecules noninvasively across the skin barrier, which can be overcome by the reduction in size to an extent that allows these molecules to pass across the skin barrier. The aim of this study was to measure the penetration and bioavailability of low molecular weight hyaluronic acid to cross an epidermal barrier model.

METHODS

Determining the quantity of hyaluronic acid in the test solutions was carried with method of photocolorimetry analysis. Investigation of the interaction of cells with LMWHA was studied with a confocal microscope.

RESULTS

The study showed that LMWHA is able to cross the epidermis. Most effective penetration level is during the first 6 hours reaching 75%, and then the concentration started to decline and reached the equilibrium state within the following 2 hours. Confocal laser microscopy demonstrated different distribution and behavior of these molecules among the keratinocytes and fibroblasts.

CONCLUSION

Reducing the size of hyaluronic acid to 5 nm enhance their transport across the epidermal layer. The concentration of hyaluronic acid molecules was higher on the fibroblast surface in comparison to their extracellular environment.

Injection Guidance System for Cellular Microinjections

In this paper we present a novel injection guidance system that assists an operator in the microinjection of living adherent cells. The system includes a micromanipulator, an injection system, an impedance measurement device and control software. The impedance measurement system detects changes in the resistance of an injection capillary during cell injections. From the measurement signal, the software determines parameters that can be used to detect several injection events such as cell—capillary contact, capillary breakage and capillary clogging, which are all unavailable in the current microinjection systems. Real cell injection experiments indicate that injection success rates can be significantly increased: from 30—40% without the system to 65% with the system.

TRANSDERMAL DRUG DELIVERY AND METHODS TO ENHANCE IT

The paper presents the common methods employed in recent years for enhancing transdermal delivery of drug substances when applying transdermal therapeutic delivery systems. The chemical, physical and mechanical methods to enhance the transport of macromolecular compounds through the skin are considered in details. 

Nucleic acid delivery into skin for the treatment of skin disease: Proofs-of-concept, potential impact, and remaining challenges

Nucleic acids (NAs) hold significant potential for the treatment of several diseases. Topical delivery of NAs for the treatment of skin diseases is especially advantageous since it bypasses the challenges associated with systemic administration which suffers from enzymatic degradation, systemic toxicity and lack of targeting to skin. However, the skin's protective barrier function limits the delivery of NAs into skin after topical application. Here, we highlight strategies for enhancing delivery of NAs into skin, and provide evidence that translation of topical NA therapies could have a transformative impact on the treatment of skin diseases.

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.

Potential of combined ultrasound and microneedles for enhanced transdermal drug permeation: a review

Transdermal drug delivery (TDD) is limited by the outer layer of the skin, i.e., the stratum corneum. Research on TDD has become very active in the recent years and various technologies have been developed to overcome the resistance of the stratum corneum to molecular diffusion. In particular, researchers have started to consider the possibility of combining the TDD technologies in order to have further increase in drug permeability. Both microneedles (MNs) and ultrasound are promising technologies. They achieve enhancement in drug permeation via different mechanisms and therefore give a good potential for combining with each other. This review will focus on discussing the potential of this combinational technique along with other important issues, e.g., the mechanisms of ultrasound and MNs as it is and these mechanisms which are coupled via the two systems (i.e. MNs and ultrasound). We discuss the possible ways to achieve this combination as well as how this combination would increase the permeability. Some of the undeveloped (weaker) research areas of MNs and sonophoresis are also discussed in order to understand the true potential of combining the two technologies when they are developed further in the future. We propose several hypothetical combinations based on the possible mechanisms involved in MNs and ultrasound. Furthermore, we carry out a cluster analysis by which we determine the significance of this combinational method in comparison with some other selected combinational methods for TDD (e.g., MNs and iontophoresis). Using a time series analysis tool (ARIMA model), the current trend and the future development of combined MNs and ultrasound are also analysed. Overall, the review in this paper indicates that combining MNs and ultrasound is a promising TDD method for the future.

Cutaneous drug delivery: an update

Cutaneous delivery of therapeutics represents a proven and attractive option for treating a variety of dermatologic conditions with minimal systemic side effects. Although there have been many innovations in drug delivery systems, the number of effective cutaneous drugs remains small, primarily because of the stratum corneum permeability barrier. Overcoming this barrier safely and reversibly to deliver large hydrophilic drugs cutaneously is one of the major challenges in the field of dermatologic therapy.

Mometasone furoate-loaded cold processed oil-in-water emulsions: in vitro and in vivo studies

Over the years, research has focused on strategies to increase benefit/risk ratio of corticoids. However, vehicles intended for topical glucocorticoids delivery with an improved benefit/risk ratio are still on demand. The aim of this work was the in vitro and in vivo characterization of cold processed oil-in-water (o/w) emulsions intended for mometasone furoate (MF) delivery to induce drug targeting to upper skin strata, decreasing adverse effects. Two o/w emulsions, containing 0.1% of MF, were developed differing in the glycol used (2-methyl-2,4-pentanediol - PT and ethoxydiglycol - TC emulsions). In vitro permeation studies revealed that these emulsions are suitable vehicles for the delivery of MF containing ingredients which are responsible for a drastically increased on the permeability coefficients of MF from a theoretical value of 1.18 × 10(-4 )cm/h to 5.20 × 10(-4) ± 2.05 × 10(-4 )cm/h and 6.30 × 10(-4) ± 2.94 × 10(-4 )cm/h, for PT and TC, respectively. The tape stripping results showed that the amount of drug that reached the viable skin layers was very low (1.99 %) and the amount that remained in the stratum corneum (SC) was 10.61%. The in vivo studies showed that the developed formulations decreased the edema and erythema in mice skin in more that 90%, assuring, at least, the same anti-inflammatory effect compared with the commercial cream. PT placebo demonstrated to contribute to restore the skin barrier by increasing the amount of lipids within the human skin.

Sonophoresis in transdermal drug deliverys

Transdermal drug delivery (TDD) has several significant advantages compared to oral drug delivery, including elimination of pain and sustained drug release. However, the use of TDD is limited by low skin permeability due to the stratum corneum (SC), the outermost layer of the skin. Sonophoresis is a technique that temporarily increases skin permeability such that various medications can be delivered noninvasively. For the past several decades, various studies of sonophoresis in TDD have been performed focusing on parameter optimization, delivery mechanism, transport pathway, or delivery of several drug categories including hydrophilic and high molecular weight compounds. Based on these various studies, several possible mechanisms of sonophoresis have been suggested. For example, cavitation is believed to be the predominant mechanism responsible for drug delivery in sonophoresis. This review presents details of various studies on sonophoresis including the latest trends, delivery of various therapeutic drugs, sonophoresis pathways and mechanisms, and outlook of future studies.

Permeability enhancement for transdermal delivery of large molecule using low-frequency sonophoresis combined with microneedles

Transdermal drug delivery is limited by the high resistance of skin towards diffusion of high-molecular-weight drugs. This is mainly because of the fact that the outer layer of the skin, that is the stratum corneum, can prevent diffusion of molecules whose molecular weight is greater than 500 Da. Sonophoresis can be used to enhance the permeability of the skin. However, in the delivery of large molecules, ultrasound alone cannot provide sufficient permeability enhancement. In addressing this issue, we propose optimised ultrasound combined with microneedles to further increase the permeation rates. In this paper, we use porcine ear skin to simulate human skin and treat the skin samples with both ultrasound and microneedles. Further, bovine serum albumin (BSA) is used as a model of larger molecular weight molecule. Our results show that the permeability of BSA is increased to 1 μm/s with the combination of 1.5 mm microneedles patch and 15-W ultrasound output which is about 10 times higher than the permeability obtained in passive diffusion. Diffusion with only microneedles or ultrasound pre-treatment is also tested. The maximum permeability from microneedles and ultrasound treatment reached 0.43 and 0.4 μm/s, respectively.

Ablative fractional resurfacing in topical drug delivery: an update and outlook

BACKGROUND

The effective delivery of therapeutic molecules to varied targets in the skin and elsewhere has been an area of ongoing research and development.

OBJECTIVE

To review the structure of the skin with an emphasis on topical drug delivery and to present the rationale for the use of ablative and nonablative fractional resurfacing in assisted drug delivery.

METHODS AND MATERIALS

Review of the currently available scientific literature on laser-assisted drug delivery.

RESULTS

A number of strategies can be employed to enhance topical drug delivery. Ablative fractional resurfacing (AFR) has been demonstrated to be effective in enhancing drug delivery. Further studies are needed to assess the use of nonablative fractional resurfacing in assisted drug delivery.

CONCLUSION

AFR-assisted drug delivery is a promising tool for the future of dermatology. We expect to see a number of agents to be paired with AFR for enhanced drug delivery. Further investigation is necessary to evaluate appropriate drug specific channel density and depth parameters. Factors that must be considered include the physicochemical properties of the drug, the target tissue, skin wounding, and cost when evaluating the drugs and conditions that will most benefit from this promising new drug delivery system.

Transdermal iontophoretic delivery of timolol maleate

Transdermal iontophoresis would be a promising method for the systemic delivery of water soluble and ionic drugs of relatively high molecular size, including peptides. The objective of the present study was to investigate the effect of biological variable such as guinea pig and human cadaver skin and other variables like drug concentration, current density on the transdermal iontophoretic transport of timolol maleate. The permeation profile of drug using solution and gel formulation was studied and compared. For better bioavailability, better patient compliance, and enhanced delivery, an iontophoretic drug delivery system of a timolol maleate matrix gel was formulated using Carbopol 974P. The study was conducted using silver-silver chloride electrodes across the guinea pig and human cadaver skin. Viscosity measurements and flux calculations indicated the suitability of the Carbopol 974P gel for transdermal iontophoretic delivery of timolol maleate. Anodal iontophoresis with silver-silver chloride electrode significantly increased the timolol maleate skin permeation as compared with the passive permeation study. The amount of timolol maleate transported during iontophoresis was significantly different among the different skins. However, iontophoretic gel formulations provided required flux of drug through human cadaver skin.

Numerical and Experimental Studies on DNA Combing Used in Fabricating Nanochannel Electroporation (NEP) Chips

Microelectromechanical processes were used to generate a stamp with array of micro pillars. This stamp was subjected to DNA combing and imprinting to form nanostrands between the micro pillars, followed by sputter coating with gold, vapour deposition and imprinting processes in order to produce the required nanochannels for the gene chip. These preparation processes have been widely used to create implementations for cell manipulation and electroporation. However, the underlying mechanism of DNA stretching has only been demonstrated experimentally and is not fully understood. It, therefore, arrives unstable yield rate when process parameters are changed. This study investigated the DNA combing and imprinting processes using two-phase flow and moving mesh methods to analyse the variation of flow field at the micron level. It shows that while withdrawing from water, a smaller velocity difference in each location and the velocity difference of pillars are the major determinants of DNA stretching and curing. The simulation results showed that a bigger α and θ led to a greater difference in flow velocity on the PDMS stamp surface; greater flow velocity difference could affect the adhesion of DNA (subsequently compromising the formation of the nanochannels). As suggested by our experimental data, longer nanochannels (3 μm) displayed a wider range of stretching speed with yield rate >90%.