Prodrug strategies for enhancing the percutaneous absorption of drugs

Ex vivo Evaluation of a Liposome-Mediated Antioxidant Delivery System on Markers of Skin Photoaging and Skin Penetration

Purpose

The topical application of antioxidants has been shown to augment the skin's innate antioxidant system and enhance photoprotection. A challenge of topical antioxidant formulation is stability and penetrability. The use of a targeted drug delivery system may improve the bioavailability and delivery of antioxidants. In this ex vivo study, we assessed the effects of the topical application of a liposome-encapsulated antioxidant complex versus a free antioxidant complex alone on skin photoaging parameters and penetrability in human skin explants.

Patients and Methods

Human organotypic skin explant cultures (hOSEC) were irradiated to mimic photoaging. The encapsulated antioxidant complex and free antioxidant complex were applied topically onto the irradiated hOSEC daily for 7 days. The two control groups were healthy untreated hOSEC and irradiated hOSEC. Photoprotective efficacy was measured with pro-inflammatory cytokine (IL-6 and IL-8) and matrix metalloproteinase 9 (MMP-9) secretion. Cell viability and metabolic activity were measured via resazurin assay. Tissue damage was evaluated via lactate dehydrogenase (LDH) cytotoxicity assay. Skin penetration of the encapsulated antioxidant complex was assessed via fluorescent dye and confocal microscopy.

Results

Compared to healthy skin, irradiated skin experienced increases in IL-6, IL-8 (p < 0.05), and MMP-9 (p < 0.05) secretion. After treatment with the encapsulated antioxidant complex, there was a 39.3% reduction in IL-6 secretion, 49.8% reduction in IL-8 (p < 0.05), and 38.5% reduction in MMP-9 (p < 0.05). After treatment with the free antioxidant complex, there were no significant differences in IL-6, IL-8, or MMP-9 secretion. Neither treatment group experienced significant LDH leakage or reductions in metabolic activity. Liposomes passed through the stratum corneum and into the epidermis.

Conclusion

The topical application of a liposome-encapsulated antioxidant complex containing ectoin, astaxanthin-rich microalgae Haematococcus pluvialis extract, and THDA improves penetrability and restored IL-6, IL-8, and MMP-9 levels in irradiated human skin explants, which was not seen in the comparator free antioxidant complex group.

Strategies to Improve the Transdermal Delivery of Poorly Water-Soluble Non-Steroidal Anti-Inflammatory Drugs

The transdermal delivery of non-steroidal anti-inflammatory drugs (NSAIDs) has the potential to overcome some of the major disadvantages relating to oral NSAID usage, such as gastrointestinal adverse events and compliance. However, the poor solubility of many of the newer NSAIDs creates challenges in incorporating the drugs into formulations suitable for application to skin and may limit transdermal permeation, particularly if the goal is therapeutic systemic drug concentrations. This review is an overview of the various strategies used to increase the solubility of poorly soluble NSAIDs and enhance their permeation through skin, such as the modification of the vehicle, the modification of or bypassing the barrier function of the skin, and using advanced nano-sized formulations. Furthermore, the simple yet highly versatile microemulsion system has been found to be a cost-effective and highly successful technology to deliver poorly water-soluble NSAIDs.

A New Hyaluronic Emulgel of Hesperetin for Topical Application-An In Vitro Evaluation

The present study aimed to formulate and characterize a hesperetin formulation to achieve adequate deposition and retention of hesperetin in the epidermis as a target for some cosmetic/dermatological actions. To derive the final emulgel, various formulations incorporating different proportions of Polysorbate 80 and hyaluronic acid underwent testing through a Box-Behnken experimental design. Nine formulations were created until the targeted emulgel properties were achieved. This systematic approach, following the principles of a design of experiment (DoE) methodology, adheres to a quality-by-design (QbD) paradigm, ensuring a robust and purposeful formulation and highlighting the commitment to a quality-driven design approach. The emulsions were developed using the phase inversion method, optimizing the emulgel with the incorporation of hyaluronic acid. Physically stable optimized emulgels were evaluated for their globule size, surface charge, viscosity, pH, electrical conductivity, and hesperetin content. These assays, along with the temperature swing test, were used to select the optimal formulation. It was characterized by a droplet size, d[4,3], of 4.02 μm, a Z-potential of -27.8 mV, an O/W sign, a pH of 5.2, and a creamy texture and proved to be stable for at least 2 months at room temperature. Additionally, in vitro release kinetics from the selected emulgel exhibited a sustained release profile of hesperetin. Skin assays revealed adequate retention of hesperetin in the human epidermis with minimum permeation. Altogether, these results corroborate the promising future of the proposed emulgel in cosmetic or dermatological use on healthy or diseased skin.

Topical steroids or emollients: does order matter?

Topical corticosteroids, topical steroid-sparing agents, and emollients are all used to treat atopic dermatitis. However, there are no formal guidelines dictating the order and timing in which these topical modalities should be applied. Additionally, the order of application may change drug absorption, efficacy, and distribution. This is especially important for patients with atopic dermatitis. These patients have a dysfunctional skin barrier, which can lead to greater systemic absorption of drugs. Moreover, children already have an increased rate of systemic absorption due to a higher ratio of body surface area to body weight. Thus, the order of application of topical regimens is of the utmost importance in pediatric dermatology. This manuscript presents an updated review of the literature with a focus on guiding clinicians toward the best practices from the available resources.

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.

Advances in the transdermal delivery of antiretroviral drugs

Antiretroviral therapy regimens are successful in stopping the advancement of human immunodeficiency virus infection to acquired immunodeficiency syndrome, and other opportunistic infections. However, they do have significant disadvantages, including long-term treatment, limited oral bioavailability, inaccessibility to organs, non-adherence by patients, and the development of medication resistance. Because of the listed drawbacks of available routes and the availability of curative medicines for human immunodeficiency virus/acquired immunodeficiency syndrome, advanced solutions are required. Antiretroviral therapy transdermal delivery is one of the current strategies that have attracted much attention from many researchers. In this narrative review, various in vitro, in vivo, and ex vivo transdermal antiretroviral therapy delivery strategies were reviewed, such as transdermal patches and films, lipid-based nano-delivery systems, microneedles, chemical penetration enhancers, and iontophoresis, which showed promising results. Although the majority of studies on Antiretroviral transdermal delivery have produced hopeful findings, additional in-depth research on passive and physical enhancement techniques, both existing and new, is necessary to fully understand the potential of this route and to make it accessible to human immunodeficiency virus patients.

Topical drug delivery strategies for enhancing drug effectiveness by skin barriers, drug delivery systems and individualized dosing

Topical drug delivery is widely used in various diseases because of the advantages of not passing through the gastrointestinal tract, avoiding gastrointestinal irritation and hepatic first-pass effect, and reaching the lesion directly to reduce unnecessary adverse reactions. The skin helps the organism to defend itself against a huge majority of external aggressions and is one of the most important lines of defense of the body. However, the skin's strong barrier ability is also a huge obstacle to the effectiveness of topical medications. Allowing the bioactive, composition in a drug to pass through the stratum corneum barrier as needed to reach the target site is the most essential need for the bioactive, composition to exert its therapeutic effect. The state of the skin barrier, the choice of delivery system for the bioactive, composition, and individualized disease detection and dosing planning influence the effectiveness of topical medications. Nowadays, enhancing transdermal absorption of topically applied drugs is the hottest research area. However, enhancing transdermal absorption of drugs is not the first choice to improve the effectiveness of all drugs. Excessive transdermal absorption enhances topical drug accumulation at non-target sites and the occurrence of adverse reactions. This paper introduces topical drug delivery strategies to improve drug effectiveness from three perspectives: skin barrier, drug delivery system and individualized drug delivery, describes the current status and shortcomings of topical drug research, and provides new directions and ideas for topical drug research.

Phosphate Prodrugs: An Approach to Improve the Bioavailability of Clinically Approved Drugs

The phosphate prodrug approach has emerged as a viable option for increasing the bioavailability of a drug candidate with low hydrophilicity and poor cell membrane permeability. When a phosphoric acid moiety is attached to the parent drug, it results in a several-fold elevation in aqueous solubility which helps to achieve desired bioavailability of the pharmaceutically active parental molecule. The neutral phosphate prodrugs have rapid diffusion ability through the plasma membrane as compared to their charged counterpart. The presence of phosphate mono ester breaking alkaline phosphatase (ALP) enzyme throughout the whole human body, is the main consideration behind the development of phosphate prodrug strategy. The popularity of this phosphate prodrug strategy is increasing nowadays due to the fulfillment of different desired pharmacokinetic characteristics required to get pharmaceutical and therapeutic responses without showing any serious adverse drug reactions (ADR). This review article mainly focuses on various phosphate prodrugs synthesized within the last decade to get an improved pharmacological response of the parent moiety along with various preclinical and clinical challenges associated with this approach. Emphasis is also given to the chemical mechanism to release the parent moiety from the prodrug.

Microneedle-Assisted Transfersomes as a Transdermal Delivery System for Aspirin

Transdermal drug delivery systems offer several advantages over conventional oral or hypodermic administration due to the avoidance of first-pass drug metabolism and gastrointestinal degradation as well as patients' convenience due to a minimally invasive and painless approach. A novel transdermal drug delivery system, comprising a combination of transfersomes with either solid silicon or solid polycarbonate microneedles has been developed for the transdermal delivery of aspirin. Aspirin was encapsulated inside transfersomes using a "thin-film hydration sonication" technique, yielding an encapsulation efficiency of approximately 67.5%. The fabricated transfersomes have been optimised and fully characterised in terms of average size distribution and uniformity, surface charge and stability (shelf-life). Transdermal delivery, enhanced by microneedle penetration, allows the superior permeation of transfersomes into perforated porcine skin and has been extensively characterised using optical coherence tomography (OCT) and transmission electron microscopy (TEM). In vitro permeation studies revealed that transfersomes enhanced the permeability of aspirin by more than four times in comparison to the delivery of unencapsulated "free" aspirin. The microneedle-assisted delivery of transfersomes encapsulating aspirin yielded 13-fold and 10-fold increases in permeation using silicon and polycarbonate microneedles, respectively, in comparison with delivery using only transfersomes. The cytotoxicity of different dose regimens of transfersomes encapsulating aspirin showed that encapsulated aspirin became cytotoxic at concentrations of ≥100 μg/mL. The results presented demonstrate that the transfersomes could resolve the solubility issues of low-water-soluble drugs and enable their slow and controlled release. Microneedles enhance the delivery of transfersomes into deeper skin layers, providing a very effective system for the systemic delivery of drugs. This combined drug delivery system can potentially be utilised for numerous drug treatments.

Investigation and Evaluation of the Transdermal Delivery of Ibuprofen in Various Characterized Nano-Drug Delivery Systems

The aim was to assess the suitability of three nano-based transdermal drug delivery systems containing ibuprofen: a nano-emulsion, a nano-emulgel, and a colloidal suspension with ibuprofen-loaded nanoparticles. Understanding the transdermal delivery of ibuprofen using nano-based drug delivery systems can lead to more effective pain relief and improved patient compliance. Characterization tests assessed the suitability of the developed drug delivery systems. Membrane release and skin diffusion studies, along with tape stripping, were performed to determine drug release and skin permeation of ibuprofen. In vitro cytotoxicity studies on HaCaT cells were conducted using MTT and neutral red assays to evaluate the safety of the developed drug delivery systems. Characterization studies confirmed stable drug delivery systems with ideal properties for transdermal delivery. Membrane release studies demonstrated the successful release of ibuprofen. In vitro skin diffusion experiments and tape stripping, detecting ibuprofen in the receptor phase, stratum corneum-epidermis, and epidermis-dermis, indicating successful transdermal and topical delivery. The in vitro cytotoxicity studies observed only minor cytotoxic effects on HaCaT cells, indicating the safety of the developed drug delivery systems. The investigation demonstrated promising results for the transdermal delivery of ibuprofen using the developed drug delivery systems, which contributes to valuable insights that may lead to improved pain management strategies.

Algae-Derived Natural Products in Diabetes and Its Complications-Current Advances and Future Prospects

Diabetes poses a significant global health challenge, necessitating innovative therapeutic strategies. Natural products and their derivatives have emerged as promising candidates for diabetes management due to their diverse compositions and pharmacological effects. Algae, in particular, have garnered attention for their potential as a source of bioactive compounds with anti-diabetic properties. This review offers a comprehensive overview of algae-derived natural products for diabetes management, highlighting recent developments and future prospects. It underscores the pivotal role of natural products in diabetes care and delves into the diversity of algae, their bioactive constituents, and underlying mechanisms of efficacy. Noteworthy algal derivatives with substantial potential are briefly elucidated, along with their specific contributions to addressing distinct aspects of diabetes. The challenges and limitations inherent in utilizing algae for therapeutic interventions are examined, accompanied by strategic recommendations for optimizing their effectiveness. By addressing these considerations, this review aims to chart a course for future research in refining algae-based approaches. Leveraging the multifaceted pharmacological activities and chemical components of algae holds significant promise in the pursuit of novel antidiabetic treatments. Through continued research and the fine-tuning of algae-based interventions, the global diabetes burden could be mitigated, ultimately leading to enhanced patient outcomes.

Advance and Challenges in the Treatment of Skin Diseases with the Transdermal Drug Delivery System

Skin diseases are among the most prevalent non-fatal conditions worldwide. The transdermal drug delivery system (TDDS) has emerged as a promising approach for treating skin diseases, owing to its numerous advantages such as high bioavailability, low systemic toxicity, and improved patient compliance. However, the effectiveness of the TDDS is hindered by several factors, including the barrier properties of the stratum corneum, the nature of the drug and carrier, and delivery conditions. In this paper, we provide an overview of the development of the TDDS from first-generation to fourth-generation systems, highlighting the characteristics of each carrier in terms of mechanism composition, penetration method, mechanism of action, and recent preclinical studies. We further investigated the significant challenges encountered in the development of the TDDS and the crucial significance of clinical trials.

The Skin and Natural Cannabinoids-Topical and Transdermal Applications

The chemical constituents of the Cannabis plant known as cannabinoids have been extensively researched for their potential therapeutic benefits. The use of cannabinoids applied to the skin as a potential method for both skin-related benefits and systemic administration has attracted increasing interest in recent years. This review aims to present an overview of the most recent scientific research on cannabinoids used topically, including their potential advantages for treating a number of skin conditions like psoriasis, atopic dermatitis, and acne. Additionally, with a focus on the pharmacokinetics and security of this route of administration, we investigate the potential of the transdermal delivery of cannabinoids as a method of systemic administration. The review also discusses the restrictions and difficulties related to the application of cannabinoids on the skin, emphasizing the potential of topical cannabinoids as a promising route for both localized and systemic administration. More studies are required to fully comprehend the efficacy and safety of cannabinoids in various settings.

Chitosan capped-gold nanoparticles as skin penetration enhancer for small molecules: A study in porcine skin

Skin is considered one of the most convenient sites for drug administration. The present study evaluated the effect of gold nanoparticles stabilized by chitosan (CS-AuNPs) and citrate ions (Ci-AuNPs) on skin permeation of sodium fluorescein (NaFI) and rhodamine b base (RhB) as small model hydrophilic and lipophilic permeants, respectively. CS-AuNPs and Ci-AuNPs were characterized by transmitted electron microscopy (TEM) and dynamic light scattering (DLS). Skin permeation was investigated using porcine skin with diffusion cells and confocal laser scanning microscopy (CLSM). The CS-AuNPs and Ci-AuNPs were spherical-shaped nanosized particles (38.4±0.7 and 32.2±0.7 nm, respectively). The zeta potential of CS-AuNPs was positive (+30.7±1.2 mV) whereas that of Ci-AuNPs was negative (-60.2±0.4 mV). The skin permeation study revealed that CS-AuNPs could enhance the permeation of NaFI with enhancement ratio (ER) of 38.2±7.5, and the effect was superior to that of Ci-AuNPs. CLSM visualization suggested that skin permeation was enhanced by improving the delivery through the transepidermal pathway. However, the permeability of RhB, a lipophilic molecule, was not significantly affected by CS-AuNPs and Ci-AuNPs. Moreover, CS-AuNPs had no cytotoxic toward human skin fibroblast cells. Therefore, CS-AuNPs are a promising skin permeation enhancer of small polar compounds.

The Science of Selecting Excipients for Dermal Self-Emulsifying Drug Delivery Systems

Self-emulsification is considered a formulation technique that has proven capacity to improve oral drug delivery of poorly soluble drugs by advancing both solubility and bioavailability. The capacity of these formulations to produce emulsions after moderate agitation and dilution by means of water phase addition provides a simplified method to improve delivery of lipophilic drugs, where prolonged drug dissolution in the aqueous environment of the gastro-intestinal (GI) tract is known as the rate-limiting step rendering decreased drug absorption. Additionally, spontaneous emulsification has been reported as an innovative topical drug delivery system that enables successful crossing of mucus membranes as well as skin. The ease of formulation generated by the spontaneous emulsification technique itself is intriguing due to the simplified production procedure and unlimited upscaling possibilities. However, spontaneous emulsification depends solely on selecting excipients that complement each other in order to create a vehicle aimed at optimizing drug delivery. If excipients are not compatible or unable to spontaneously transpire into emulsions once exposed to mild agitation, no self-emulsification will be achieved. Therefore, the generalized view of excipients as inert bystanders facilitating delivery of an active compound cannot be accepted when selecting excipients needed to produce self-emulsifying drug delivery systems (SEDDSs). Hence, this review describes the excipients needed to generate dermal SEDDSs as well as self-double-emulsifying drug delivery systems (SDEDDSs); how to consider combinations that complement the incorporated drug(s); and an overview of using natural excipients as thickening agents and skin penetration enhancers.

Mixed Edge Activators in Ibuprofen-Loaded Transfersomes: An Innovative Optimization Strategy Using Box-Behnken Factorial Design

Transfersomes have been highlighted as an interesting nanotechnology-based approach to facilitate the skin delivery of bioactive compounds. Nevertheless, the properties of these nanosystems still need to be improved to enable knowledge transfer to the pharmaceutical industry and the development of more efficacious topical medicines. Quality-by-design strategies, such as Box-Behnken factorial design (BBD), are in line with the current need to use sustainable processes to develop new formulations. Thus, this work aimed at optimizing the physicochemical properties of transfersomes for cutaneous applications, by applying a BBD strategy to incorporate mixed edge activators with opposing hydrophilic-lipophilic balance (HLB). Tween^® 80 and Span^® 80 were used as edge activators and ibuprofen sodium salt (IBU) was selected as the model drug. After the initial screening of the IBU solubility in aqueous media, a BBD protocol was implemented, and the optimized formulation displayed appropriate physicochemical properties for skin delivery. By comparing the optimized transfersomes to equivalent liposomes, the incorporation of mixed edge activators was found to be beneficial to upgrade the storage stability of the nanosystems. Furthermore, their cytocompatibility was shown by cell viability studies using 3D HaCaT cultures. Altogether, the data herein bode well for future advances in the use of mixed edge activators in transfersomes for the management of skin conditions.

Microneedle-assisted transdermal delivery of nanoparticles: Recent insights and prospects

Transdermal delivery of drugs offers an interesting alternative for the administration of molecules that present certain troubles when delivered by the oral route. It can produce systemic effects or perform a local action when the formulation exerts an optimal controlled drug release or a targeted delivery to the specific cell type or site. It also avoids several inconveniences of the oral administration such as the hepatic first pass effect, gastric pH-induced hydrolysis, drug malabsorption because of certain diseases or surgeries, and unpleasant organoleptic properties. Nanomedicine and microneedle array patches (MAPs) are two of the trendiest delivery systems applied to transdermal research nowadays. However, the skin is a protective barrier and nanoparticles (NPs) cannot pass through the intact stratum corneum. The association of NPs and MAPs (NPs@MAPs) work synergistically, since MAPs assist NPs to bypass the outer skin layers, and NPs contribute to the system providing controlled drug release and targeted delivery. Vaccination and tailored therapies have been proposed as fields where both NPs and MAPs have great potential due to inherent characteristics. MAPs conception and easy use could allow self-administration and therefore facilitate mass vaccination campaigns in undeveloped areas with weak healthcare services. Additionally, nanomedicine is being explored as a platform to personalize therapies in such an important field as oncology. In this work we show recent insights that prove the benefits of NPs@MAPs association and analyze the prospects and the discrete interest of the industry in NPs@MAPs, evaluating different limiting steps that restricts NPs@MAPs translation to the clinical practice. This article is categorized under: Nanotechnology Approaches to Biology > NA Therapeutic Approaches and Drug Discovery > NA.

The effect of polysorbate 20 and polysorbate 80 on the solubility of quercetin

Background: Quercetin acts as an antioxidant, anti-inflammatory, wound healing, and anti-aging so quercetin can be used as a topical preparation. However, it has low solubility in water at 0.01 mg/ml at 25°C. Increasing the solubility of quercetin in water was done by the addition of surfactants. Objective: This study compared the solubility of quercetin in Polysorbate 20 (P20) and Polysorbate 80 (P80) in a citrate buffer medium pH 4.5±0.2. Methods: The surfactants Polysorbate 80 and Polysorbate 20 differ in their alkyl chain length. Polysorbate 80 has an alkyl chain length of 18, while Polysorbate 20 has an alkyl chain length of 12. The concentrations of surfactant are above, below, and at the critical micelle concentration (CMC) values. The concentrations of quercetin were determined at the maximum wavelength by spectrophotometric method. Results: The results of the quercetin solubility test without surfactant were 3.89±0.59 mg/L. The results of the quercetin solubility test by adding Polysorbate 20 at a concentration of 42.0 ppm; 57.5 ppm; and 73.0 ppm were 3.62±0.72, 4.04±0.23 and 8.35±1.97 mg/L, respectively. While the solubility of quercetin by adding Polysorbate 80 at a concentration of 4.0 ppm, 11.5 ppm, and 19.0 ppm was 11.15±0.72, 11.37±1.23 and 14.17±1.96 mg/L, respectively. The solubility of quercetin is greater after the addition of surfactant Polysorbate 20 only at the concentration above the CMC value and the solubility of quercetin is greater with the addition of surfactant Polysorbate 80 at all concentrations. Surfactant Polysorbate 20 increases the solubility of quercetin in citrate buffer pH 4.5±0.2 only at concentrations above the CMC value of 2.14 times. Polysorbate 80 can increase the solubility of quercetin in citrate buffer pH 4.5±0.2 at concentrations below, at, and above CMC by 2.87, 2.92, and 3.63 times, respectively. Conclusion: Polysorbate 80 can increase the solubility of quercetin in citrate buffer pH 4.5±0.2 higher than Polysorbate 20.

Skin drug delivery using lipid vesicles: A starting guideline for their development

Lipid vesicles can provide a cost-effective enhancement of skin drug absorption when vesicle production process is optimised. It is an important challenge to design the ideal vesicle, since their properties and features are related, as changes in one affect the others. Here, we review the main components, preparation and characterization methods commonly used, and the key properties that lead to highly efficient vesicles for transdermal drug delivery purposes. We stand by size, deformability degree and drug loading, as the most important vesicle features that determine the further transdermal drug absorption. The interest in this technology is increasing, as demonstrated by the exponential growth of publications on the topic. Although long-term preservation and scalability issues have limited the commercialization of lipid vesicle products, freeze-drying and modern escalation methods overcome these difficulties, thus predicting a higher use of these technologies in the market and clinical practice.

Chitin-Glucan Complex Hydrogels: Physical-Chemical Characterization, Stability, In Vitro Drug Permeation, and Biological Assessment in Primary Cells

Chitin-glucan complex (CGC) hydrogels were fabricated by coagulation of the biopolymer from an aqueous alkaline solution, and their morphology, swelling behavior, mechanical, rheological, and biological properties were studied. In addition, their in vitro drug loading/release ability and permeation through mimic-skin artificial membranes (Strat-M) were assessed. The CGC hydrogels prepared from 4 and 6 wt% CGC suspensions (Na5₁*⁴ and Na5₁*⁶ hydrogels, respectively) had polymer contents of 2.40 ± 0.15 and 3.09 ± 0.22 wt%, respectively, and displayed a highly porous microstructure, characterized by compressive moduli of 39.36 and 47.30 kPa and storage moduli of 523.20 and 7012.25 Pa, respectively. Both hydrogels had a spontaneous and almost immediate swelling in aqueous media, and a high-water retention capacity (>80%), after 30 min incubation at 37 °C. Nevertheless, the Na5₁*⁴ hydrogels had higher fatigue resistance and slightly higher-water retention capacity. These hydrogels were loaded with caffeine, ibuprofen, diclofenac, or salicylic acid, reaching entrapment efficiency values ranging between 13.11 ± 0.49% for caffeine, and 15.15 ± 1.54% for salicylic acid. Similar release profiles in PBS were observed for all tested APIs, comprising an initial fast release followed by a steady slower release. In vitro permeation experiments through Strat-M membranes using Franz diffusion cells showed considerably higher permeation fluxes for caffeine (33.09 µg/cm²/h) and salicylic acid (19.53 µg/cm²/h), compared to ibuprofen sodium and diclofenac sodium (4.26 and 0.44 µg/cm²/h, respectively). Analysis in normal human dermal fibroblasts revealed that CGC hydrogels have no major effects on the viability, migration ability, and morphology of the cells. Given their demonstrated features, CGC hydrogels are very promising structures, displaying tunable physical properties, which support their future development into novel transdermal drug delivery platforms.

Liposomal Amphotericin B for Treatment of Leishmaniasis: From the Identification of Critical Physicochemical Attributes to the Design of Effective Topical and Oral Formulations

The liposomal amphotericin B (AmB) formulation, AmBisome^®, still represents the best therapeutic option for cutaneous and visceral leishmaniasis. However, its clinical efficacy depends on the patient's immunological status, the clinical manifestation and the endemic region. Moreover, the need for parenteral administration, its side effects and high cost significantly limit its use in developing countries. This review reports the progress achieved thus far toward the understanding of the mechanism responsible for the reduced toxicity of liposomal AmB formulations and the factors that influence their efficacy against leishmaniasis. It also presents the recent advances in the development of more effective liposomal AmB formulations, including topical and oral liposome formulations. The critical role of the AmB aggregation state and release rate in the reduction of drug toxicity and in the drug efficacy by non-invasive routes is emphasized. This paper is expected to guide future research and development of innovative liposomal formulations of AmB.

Comparative study on the topical and transdermal delivery of diclofenac incorporated in nano-emulsions, nano-emulgels, and a colloidal suspension

Transdermal delivery of active pharmaceutical ingredients (APIs) can be challenging, since the skin possesses a rate-limiting barrier, which may be overcome when APIs possess certain ideal physicochemical properties. The lack thereof would require that APIs be included in drug delivery vehicles to enhance skin permeation. Hence, diclofenac was incorporated into various drug delivery vehicles (i.e., nano-emulsions, nano-emulgels, and a colloidal suspension containing drug-loaded nanoparticles) to investigate the transdermal delivery thereof, while nano-emulsions and nano-emulgels had varying concentrations of evening primrose oil (EPO). The aim of the study was to compare the topical and transdermal diclofenac delivery from the different types of vehicles and to investigate the influence the different EPO concentrations had on diclofenac delivery. After characterization, membrane release studies were performed (to determine whether the API was successfully released from the vehicle) followed by in vitro skin diffusion studies and tape stripping (to establish whether the vehicles assisted the API in reaching the target site (transdermal delivery)). Lastly, cytotoxicity studies were conducted via methyl thiazolyl tetrazolium (MTT) and neutral red (NR) assays on human keratinocyte (HaCaT) cells. Results showed minimal cytotoxic effects at concentrations equivalent to that which had permeated through the skin, while the membrane release and in vitro skin diffusion studies indicated that the nano-emulsions and the 10% EPO vehicles increased API release and diffusion when compared to the other vehicles. However, the colloidal suspension had the highest concentrations of API within the skin. Hence, all the vehicles were non-toxic and effectively delivered diclofenac through the transdermal route.

Studies Regarding the Antimicrobial Behavior of Clotrimazole and Limonene

The paper presents the results of the studies performed to establish the effect of the mixtures between limonene and clotrimazole against microbial pathogens involved in dermatological diseases, such as Candida albicans, Staphyloccocus aureus, and Escherichia coli. Preliminary data obtained from the studies performed in microplates revealed a possible synergism between the mixture of clotrimazole and limonene for Staphylococcus aureus. Studies performed "in silico" with programs such as CLC Drug Discovery Workbench and MOLEGRO Virtual Docker, gave favorable scores for docking each compound on a specific binding site for each microorganism. The tests performed for validation, with the clotrimazole (0.1%) and different sources of limonene (1.9% citrus essential oils), showed a synergistic effect on Staphylococcus aureus in the case of the mixtures between clotrimazole and the essential oils of Citrus reticulata or Citrus paradisi. The studies performed on Staphylococcus aureus MRSA showed a synergistic effect between clotrimazole and the essential oils obtained from Citrus bergamia, Citrus aurantium, or Citrus paradisi. In the case of Pseudomonas aeruginosa, essential oils and clotrimazole used alone did not exhibit antimicrobial activities, but the mixtures between clotrimazole and the essential oils of Citrus bergamia or Citrus sinensis exhibited a synergistic antimicrobial effect.

Permeation of albumin through the skin depending on its concentration and the substrate used in simulated conditions in vivo

OBJECTIVE

Many drugs applied to the skin with a systemic effect do not have a therapeutic effect, due to the barrier posed by the complex structure of the skin. To counteract this, absorption promoters are often added to the drug formulation. The use of albumin as an effective drug carrier is increasingly being addressed. Albumin, a natural, non-toxic polymer, can target drugs to specific cells and extend their biological half-life. This study was designed to trace the permeation of albumin after topical administration to the skin as a potential carrier of therapeutic substances.

MATERIALS AND METHODS

Four dermal formulations based on different polymers were prepared: methyl cellulose, sodium alginate, hypromellose and chitosan with methyl cellulose, obtaining final concentrations of albumin of 2%, 1.5% and 1%. The permeation of albumin through the skin was examined under simulated in vivo conditions.

RESULTS

Most albumin permeated from the methylcellulose-based hydrogel. Depending on the concentration of albumin, permeation profiles were plotted and permeation rate constant and AUC_(0-24 h) were calculated.

CONCLUSION

Methylcellulose was the optimal polymer for albumin release, whereas hypromellose was the least favorable. The concentration of albumin influences the amount and rate of permeation of this protein. The optimal concentration was 10 mg/g, from which the most albumin penetrated and the fastest. Human skin appeared to be more permeable to albumin than pig skin. However, the similar permeation profile through both membranes successfully allows the use of pig skin to track and evaluate the permeation of therapeutic substances with systemic effects.

Adapting Clofazimine for Treatment of Cutaneous Tuberculosis by Using Self-Double-Emulsifying Drug Delivery Systems

Although chemotherapeutic treatment regimens are currently available, and considerable effort has been lavished on the development of new drugs for the treatment of tuberculosis (TB), the disease remains deeply intractable and widespread. This is due not only to the nature of the life cycle and extraordinarily disseminated habitat of the causative pathogen, principally Mycobacterium tuberculosis (Mtb), in humans and the multi-drug resistance of Mtb to current drugs, but especially also to the difficulty of enabling universal treatment of individuals, immunocompromised or otherwise, in widely differing socio-economic environments. For the purpose of globally eliminating TB by 2035, the World Health Organization (WHO) introduced the "End-TB" initiative by employing interventions focusing on high impact, integrated and patient-centered approaches, such as individualized therapy. However, the extraordinary shortfall in stipulated aims, for example in actual treatment and in TB preventative treatments during the period 2018-2022, latterly and greatly exacerbated by the COVID-19 pandemic, means that even greater pressure is now placed on enhancing our scientific understanding of the disease, repurposing or repositioning old drugs and developing new drugs as well as evolving innovative treatment methods. In the specific context of multidrug resistant Mtb, it is furthermore noted that the incidence of extra-pulmonary TB (EPTB) has significantly increased. This review focusses on the potential of utilizing self-double-emulsifying drug delivery systems (SDEDDSs) as topical drug delivery systems for the dermal route of administration to aid in treatment of cutaneous TB (CTB) and other mycobacterial infections as a prelude to evaluating related systems for more effective treatment of CTB and other mycobacterial infections at large. As a starting point, we consider here the possibility of adapting the highly lipophilic riminophenazine clofazimine, with its potential for treatment of multi-drug resistant TB, for this purpose. Additionally, recently reported synergism achieved by adding clofazimine to first-line TB regimens signifies the need to consider clofazimine. Thus, the biological effects and pharmacology of clofazimine are reviewed. The potential of plant-based oils acting as emulsifiers, skin penetration enhancers as well as these materials behaving as anti-microbial components for transporting the incorporated drug are also discussed.

Amorphization of Drugs for Transdermal Delivery-a Recent Update

Amorphous solid dispersion is a popular formulation approach for orally administered poorly water-soluble drugs, especially for BCS class II. But oral delivery could not be an automatic choice for some drugs with high first-pass metabolism susceptibility. In such cases, transdermal delivery is considered an alternative if the drug is potent and the dose is less than 10 mg. Amorphization of drugs causes supersaturation and enhances the thermodynamic activity of the drugs. Hence, drug transport through the skin could be improved. The stabilization of amorphous system is a persistent challenge that restricts its application. A polymeric system, where amorphous drug is dispersed in a polymeric carrier, helps its stability. However, high excipient load often becomes problematic for the polymeric amorphous system. Coamorphous formulation is another approach, where one drug is mixed with another drug or low molecular weight compound, which stabilizes each other, restricts crystallization, and maintains a single-phase homogenous amorphous system. Prevention of recrystallization along with enhanced skin permeation has been observed by the transdermal coamorphous system. But scalable manufacturing methods, extensive stability study and in-depth in vivo evaluation are lacking. This review has critically studied the mechanistic aspects of amorphization and transdermal permeation by analyzing recent researches in this field to propose a future direction.

Mechanism and Application of Chitosan and Its Derivatives in Promoting Permeation in Transdermal Drug Delivery Systems: A Review

The mechanisms and applications of chitosan and its derivatives in transdermal drug delivery to promote drug permeation were reviewed in this paper. Specifically, we summarized the permeation-promoting mechanisms of chitosan and several of its derivatives, including changing the structure of stratum corneum proteins, acting on the tight junction of granular layers, affecting intercellular lipids, and increasing the water content of stratum corneum. These mechanisms are the reason why chitosan and its derivatives can increase the transdermal permeation of drugs. In addition, various transdermal preparations containing chitosan and its derivatives were summarized, and their respective advantages were expounded, including nanoparticles, emulsions, transdermal microneedles, nanocapsules, transdermal patches, transdermal membranes, hydrogels, liposomes, and nano-stents. The purpose of this review is to provide a theoretical basis for the further and wider application of chitosan in transdermal drug delivery systems. In the future, research results of chitosan and its derivatives in transdermal drug delivery need more support from in vivo experiments, as well as good correlation between in vitro and in vivo experiments. In conclusion, the excellent permeability-promoting property, good biocompatibility, and biodegradability of chitosan and its derivatives make them ideal materials for local transdermal drug delivery.

The effectiveness of synthetic methoxylated isoflavones in delivering to the skin and alleviating psoriasiform lesions via topical absorption

This study was conducted to appraise the possible potential of synthetic isoflavones (SIFs) on psoriasis treatment. A practical and easy-to-operate approach was employed in synthesizing a series of SIFs, considering that acquiring flavonoids from natural resources is usually expensive, time-consuming, and non-eco-friendly. Seven SIFs derived from daidzein were produced with differences in the location of the hydroxyl groups and degree of methoxylation. The in vitro and in vivo skin absorption of topically applied SIFs was estimated. Further, keratinocytes (HaCaT) were employed as the model to investigate the anti-inflammatory activity of the isoflavones. The lipophilicity was increased from SIF-1 to -7. Noteworthily, there was a parabolic relationship between lipophilicity and skin absorption, with SIF-5 (4',7-dihydroxyisoflavone, daidzein) and SIF-6 (7-hydroxy-3',4'-dimethoxyisoflavone, cladrin) demonstrating the highest retention in pig skin. The methoxylated isoflavone SIF-5 showed the greatest permeation into barrier-deficient skin among the compounds tested, with a 6- and 8-fold increase after lipid and protein removal. The cell-based study exhibited the capability of SIFs to restrain the overexpressed IL-6, IL-8, and CXCL1 in stimulated HaCaT. The therapeutic index (TI) predicted the potential candidates of SIF-5 and SIF-6 for topical application to treat psoriatic inflammation. The imiquimod (IMQ)-driven psoriasiform murine model manifested the inhibition of hyperplasia and immune cell infiltration by topically administered SIF-5 and SIF-6. The epidermal thickness of IMQ-treated skin was decreased from 172 to 40 μm by both isoflavones. This effect was comparable with that of betamethasone, the positive control. The topical treatment of SIF-6 significantly reduced cytokine/chemokine upregulation by IMQ. The methoxylated isoflavone with dramatic anti-inflammatory activity is promising for the development of an antipsoriatic agent.

GSH/enzyme-responsive 2-sulfonyl-1-methylimidazole prodrug for enhanced transdermal drug delivery and therapeutic efficacy against hyperthyroidis

Novel GSH/enzyme-responsive anti-hyperthyroidism prodrugs designed for transdermal delivery of 2-sulfonyl-1- methylimidazole (MMI) were synthesized by a Michael addition reaction of MMI with propiolic acid (PA) followed by esterification with three long chain fatty alcohols and their structures were characterized by ¹H-NMR, ¹³C-NMR and mass spectrometry. Their maximum steady state flux through rat skin in the PG/W solution was found to be more than 37-times faster than that of MMI. The result may be attributed to the improved lipophilicity of prodrug and rapid bioconversion. The prodrugs were hydrolyzed by esterase on passing through the skin and appeared mainly as intermediate MMI-PA in the receiver compartment and accompanied by a small amount of MMI and intact prodrug. The prodrugs did not release any MMI in the media without GSH or with 100 µM GSH, while the obvious MMI release could be observed within 6.4 h in the media containing 2 mM and 10 mM GSH, and their maximum cumulative release rates reached 95.07% for lauryl alcohol ester prodrug (MMI-PA-OLa). MMI-PA-OLa exhibited a significant inhibition effect on lactoperoxidase (LPO) after being incubated in millimolar GSH media, whose inhibition rate was very similar to that of free MMI with an equivalent dose. These results suggested that MMI-PA-OLa could pass efficiently through the skin and release MMI in response to the intracellular environment.

The Challenge in Combining Pelotherapy and Electrotherapy (Iontophoresis) in One Single Therapeutic Modality

Pelotherapy and electrotherapy are therapeutic methodologies with proven success in physical medicine and rehabilitation (PMR) and dermatology fields. The main purpose of these therapeutic modalities is to reduce pain, accelerate wound healing, alleviate muscle spasms, and improve mobility, and muscle tone. Their main challenge is in the passage of some ionic species through the skin barrier. The use of drugs, such as diclofenac, corticosteroids or steroids, has gained widespread efficacy recognition in physical therapy and the therapeutic action of these drugs is widely studied in experimental and clinical trials. Unlike pharmaceutical and cosmetic clays, peloids are not subject to any prior quality control or subject to any specific European regulation. The dermal absorption values are an integral part of the risk assessment process for peloids. This work explores the converging points between these two transdermal drug delivery systems (TDDS) and the presentation of methodologies to achieve peloid safety compliance, especially concerning the potential and degree of toxicity arising from ion exchange and trace elements. TDDS is applied to the pharmaceuticals industry and drug is the generic term for the active substances released into skin tissues. The transdermal delivery of drugs or clay components with therapeutic properties is limited due to the excellent barrier function of the stratum corneum. The transdermal drug delivery of pelotherapy is enhanced by temperature and electrically by iontophoresis. The low voltage of iontophoresis and sweat phenomena with pore dilation driven by pelotherapy allows the use of the same pathways: hair follicles and sweat pore. The therapeutic integration of iontophoresis and pelotherapy focused on patient benefits and low safety-related risk may contribute to the outstanding physiological performance of pelotherapy, specifically, in the way the essential elements and exchange cations pass through the skin barrier. The validation of an innovative iontophoretic systems applied to pelotherapy can also promote future challenges in the obtaining of the ideal therapeutic control of peloids and the clinical validation of results with physiological efficacy recognition.

Terpenoid Hydrazones as Biomembrane Penetration Enhancers: FT-IR Spectroscopy and Fluorescence Probe Studies

Hydrazones based on mono- and bicyclic terpenoids (verbenone, menthone and carvone) have been investigated in vitro as potential biomembrane penetration enhancers. In this regard, liposomes composed of lecithin or cardiolipin as phospholipid phase components with incorporated fluorescence probes have been prepared using the thin-film ultrasonic dispersion method. The mean particle size of the obtained liposomes, established using laser diffraction, was found to be 583 ± 0.95 nm, allowing us to categorize them as multilamellar vesicles (MLVs) according to their morphology. Pursuant to fluorescence analysis, we may assume a reduction in microviscosity and, consequently, a decrease in the packing density of lecithin and cardiolipin lipids to be the major mechanism of action for terpenoid hydrazones 1–15. In order to determine the molecular organization of the lipid matrix, lipids were isolated from rat strata cornea (SCs) and their interaction with tested compounds was studied by means of Fourier transform infrared spectroscopy. FT-IR examination suggested that these hydrazones fluidized the SC lipids via the disruption of the hydrogen-bonded network formed by polar groups of SC constituents. The relationship between the structure of terpenoid hydrazones and their ability to enhance biomembrane penetration is discussed.

Synthesis of rutin derivatives to enhance lipid solubility and development of topical formulation with a validated analytical method

BACKGROUND

Rutin is available on the market as a topical formulation for the treatment of several conditions, such as internal bleeding, hemorrhoids, and varicose veins. However, these gels have low solubility and limited bioavailability due to their decreased lipid solubility.

OBJECTIVE

In this study, we aimed to synthesize potentially novel lipophilic rutin prodrugs. The suggested library of these rutin prodrugs includes changing the solubility profile to facilitate rutin transport across biological barriers, thereby improving drug delivery through topical application.

METHODS

Six rutin derivatives were synthesized based on the ester prodrug strategy. The synthesized compounds were formulated as topical ointments, and their permeability via Franz diffusion was measured. An ultraviolet (UV) analytical method was developed in our laboratories to quantify rutin derivatives both as raw materials and in final dosage forms. The analytical method was then validated.

RESULT

The results of Franz diffusion analyses showed that transdermal permeability increased by 10_Fo.jpgl height=""d for decaacetylated rutin compared to the other esterified rutins. A simple analytical method for the analysis of the formulated rutin ester was developed and validated. Moreover, the formulated ointment of decaacetylated rutin in our research laboratory was found to be stable under stability accelerated conditions. Synthesis of potentially more lipophilic compounds would yield novel rutin prodrugs suitable for topical formulation.

CONCLUSION

This project provides a synthetic approach for many similar natural products. The research idea and strategy followed in this research project could be adapted by pharmaceutical and herbal establishments.

A systematic comparison of the effect of topically applied anthraquinone aglycones to relieve psoriasiform lesion: The evaluation of percutaneous absorption and anti-inflammatory potency

The anthraquinones derived from rhubarb are reported to have anti-inflammatory activity. The present study aimed to assess the topical application of rhubarb anthraquinone aglycones for psoriasis treatment. The antipsoriatic effect of five anthraquinones, including aloe-emodin, rhein, emodin, physcion, and chrysophanol, was compared to elucidate a structure-permeation relationship. Molecular modeling was employed to determine the physicochemical properties. Both macrophages (differentiated THP-1) and keratinocytes (HaCaT) were used to examine the anti-inflammatory activity in the cell-based study. The in vitro pig skin absorption showed that chrysophanol was the compound with the highest cutaneous accumulation. Topically applied rhein was detected to be largely delivered to the receptor compartment. The absorption of rhein was increased by 5-fold in the barrier-deficient skin as compared to intact skin. By stimulating macrophages with imiquimod (IMQ) to model the inflammation in psoriasis, it was found that the anthraquinones significantly reduced IL-6, IL-23, and TNF. The cytokine inhibition level was comparable for the five compounds. The anthraquinones suppressed cytokines by inhibiting the activation of MAPK and NF-κB signaling. The anthraquinones also downregulated IL-6, IL-8, and IL-24 in the inflammatory keratinocytes stimulated with TNF. Rhein and chrysophanol were comparable to curtail the STAT3 phosphorylation in keratinocytes induced by the conditioned medium of stimulated macrophages. The IMQ-induced psoriasiform mouse model demonstrated the improvement of scaling, erythema, and epidermal hyperplasia by topically applied rhein or chrysophanol. The epidermal acanthosis evoked by IMQ was reduced with rhein and chrysophanol by 3-fold. The histological profiles exhibit that both anthraquinone compounds diminished the number of macrophages and neutrophils in the lesional skin, skin-draining lymph node, and spleen. Rhein and chrysophanol showed multifunctional inhibition, by regulating several targets for alleviating psoriasiform inflammation.

Submerged Eutectic-Assisted, Solvent-Free Mechanochemical Formation of a Propranolol Salt and Its Other Multicomponent Solids

Salt preparation via a solid-state reaction offers a solution to challenges posed by current pharmaceutical research, which include combining development of novel forms of active pharmaceutical ingredients with greener, sustainable synthesis. This work investigated in detail the mechanism of salt formation between propranolol (PRO) and capric acid (CAP) and explored the solid eutectic phases comprising this salt, propranolol caprate (PRC). The salt structure was solved by X-ray diffraction, and the properties in the crystalline and supercooled states were fully characterised using thermal analysis, nuclear magnetic resonance, Fourier-transform infrared spectroscopy and broadband dielectric spectroscopy (BDS). PRC forms via a submerged eutectic phase composed of PRO and CAP, below room temperature, by mechanochemistry without an extra input of energy. Two other solid eutectic phases are composed of PRC and either CAP or PRO, at 0.28 and 0.82 mol fraction of PRO, respectively. BDS indicated that the supercooled PRC has ionic character, whereas the supercooled PRC-PRO eutectic had predominantly non-ionic properties despite comprising the salt. In conclusion, knowledge of the mechanism of formation of multicomponent systems can help in designing more sustainable pharmaceutical processes.

Topical Delivery of Niacinamide to Skin Using Hybrid Nanogels Enhances Photoprotection Effect

Niacinamide (NIA) has been widely used in halting the features of ageing by acting as an antioxidant and preventing dehydration. NIA’s physicochemical properties suggest difficulties in surpassing the barrier imposed by the stratum corneum layer to reach the target in the skin. To improve cutaneous delivery of NIA, a hybrid nanogel was designed using carrageenan and polyvinylpyrrolidone polymers combined with jojoba oil as a permeation enhancer. Three different types of transethosomes were prepared by the thin-film hydration method, made distinct by the presence of either an edge activator or a permeation enhancer, to allow for a controlled delivery of NIA. Formulations were characterized by measurements of size, polydispersity index, zeta potential, encapsulation efficiency, and loading capacity, and by evaluating their chemical interactions and morphology. Skin permeation assays were performed using Franz diffusion cells. The hybrid hydrogels exhibited robust, porous, and highly aligned macrostructures, and when present, jojoba oil changed their morphology. Skin permeation studies with transethosomes-loaded hydrogels showed that nanogels per se exhibit a more controlled and enhanced permeation, in particular when jojoba oil was present in the transethosomes. These promising nanogels protected the human keratinocytes from UV radiation, and thus can be added to sunscreens or after-sun lotions to improve skin protection.

Emulgel: an effective drug delivery system

BACKGROUND

Emulgels are the emerging drug delivery system nowadays that has become popular for the delivery of hydrophobic drugs. This formulation is considered a novel type of drug delivery system and a mixture of emulsion and gel.

OBJECTIVE

The objective of this review is to throw light on the preparation of emulgels and their evaluation which will conclude how important these dosage forms are. In the coming years, it will be most commonly used because it is easy to use and enhances patient compliance.

CONCLUSION

Emulgels are easily removable, spreadable, thixotropic, greaseless, have a pleasing appearance, emollient, long shelf life, and transparent. In the present era, the emulgels are being used for the delivery of many drugs like analgesics, anti-inflammatory, anti-acne and anti-fungal. Hence, it is of great pharmacological importance and is relatively free of side effects.

Molecular perspective of efficiency and safety problems of chemical enhancers: bottlenecks and recent advances

Chemical penetration enhancer (CPE) is a preferred approach to improve drug permeability through the skin, due to its unique advantages of simple use and high compatibility. However, CPEs efficiency and safety problems frequently arise, which greatly restrains the further application in transdermal drug delivery systems (TDDS). To get access to the root of problems, the efficiency and safety of CPEs are reviewed especially from molecular perspectives, which include (1) the possible factors of CPEs low efficiency; (2) the possible contribution of CPEs in the evolution of safety problems such as skin irritation and allergic reaction; (3) the interactive relationship between CPEs efficiency and safety, as well as the bottlenecks of achieving their balance. More importantly, based on these, recent advances are summarized in improving efficiency or safety of CPEs, which offers a guidance of rationally selecting CPEs in future research.

Dermal Drug Delivery of Phytochemicals with Phenolic Structure via Lipid-Based Nanotechnologies

Phenolic compounds are a large, heterogeneous group of secondary metabolites found in various plants and herbal substances. From the perspective of dermatology, the most important benefits for human health are their pharmacological effects on oxidation processes, inflammation, vascular pathology, immune response, precancerous and oncological lesions or formations, and microbial growth. Because the nature of phenolic compounds is designed to fit the phytochemical needs of plants and not the biopharmaceutical requirements for a specific route of delivery (dermal or other), their utilization in cutaneous formulations sets challenges to drug development. These are encountered often due to insufficient water solubility, high molecular weight and low permeation and/or high reactivity (inherent for the set of representatives) and subsequent chemical/photochemical instability and ionizability. The inclusion of phenolic phytochemicals in lipid-based nanocarriers (such as nanoemulsions, liposomes and solid lipid nanoparticles) is so far recognized as a strategic physico-chemical approach to improve their in situ stability and introduction to the skin barriers, with a view to enhance bioavailability and therapeutic potency. This current review is focused on recent advances and achievements in this area.

A transferosome-loaded bigel for enhanced transdermal delivery and antibacterial activity of vancomycin hydrochloride

Transdermal drug delivery is an attractive route of administration relative to other routes as it offers enhanced therapeutic efficacy. However, due to poor skin permeability of certain drugs, their application in transdermal delivery is limited. The ultra-deformable nature of transferosomes makes them suitable vehicles for transdermal delivery of drugs that have high molecular weights and hydrophilicity. However, their low viscosity, which leads to low contact time on the surface of the skin, has restricted their application in transdermal delivery. Therefore, this study aimed to deliver transferosomes loaded with a highly water-soluble and high molecular weight vancomycin hydrochloride (VCM-HCl) via a bigel for systemic delivery and treatment of microbial infections. VCM-HCl-loaded transferosomal formulations (TNFs) were prepared using a reverse-phase evaporation method and then loaded into a bigel. Both the TNFs and TNFs-loaded bigel (TNF-L-B) were characterized by a range of in vitro and ex vivo techniques. TNFs and TNF-L-B were tested for biosafety via the MTT assay and found to be biosafe. Prepared TNFs had sizes, zeta potential and entrapment efficiency of 63.02 ± 5.34 nm, -20.93 ± 6.13 mV and 84.48 ± 1.22% respectively. VCM-HCl release from TNF-L-B showed a prolonged release profile with 39.76 ± 1.6% after 24hrs when compared to bare VCM-HCl loaded in the bigel (74.81 ± 8.84%). Ex-vivo permeation of prepared TNF-L-B showed a higher permeation flux of 0.56 µg/cm²/h compared to the bare VCM-HCl-loaded bigel of 0.23 µg/cm²/h, indicating superior permeation and bioavailability of the drug. Additionally, the prepared TNF-L-B demonstrated improved antimicrobial activity. The TNF-L-B showed minimum inhibitory concentrations (MIC) of 0.97 μg/ml against Staphylococcus aureus (SA) and 1.95 μg/ml against methicillin-resistant SA (MRSA), which were 2-fold lower MIC values than the bare drug. The time-kill assay showed that both TNFs and TNF-L-B systems caused a 5.6-log reduction (100%) in MRSA compared to bare VCM-HCl after 24 hrs of incubation. Furthermore, as opposed to the bare VCM-HCl solution, the degree of biofilm reduction caused by TNFs (55.72%) and TNF-L-B (34.58%) suggests their dominance in eradicating MRSA biofilm. These findings indicate that TNF-L-B is a promising system for transdermal delivery of hydrophilic and high molecular weight drugs.

Topical NSAIDs for acute local pain relief: in vitro characterization of drug delivery profiles into and through human skin

OBJECTIVE

The efficacy of topical nonsteroidal anti-inflammatory drugs (NSAIDs) relates not only to the individual NSAID used but also to differences in formulation design. The aim of this study was to investigate the fundamental differences in ibuprofen and diclofenac drug delivery vehicles, specifically gels and plasters, compared to a recently launched 200 mg ibuprofen medicated plaster and characterize the resulting dermatologic-pharmacokinetic profiles into and through ex vivo human skin layers.

METHODS

In vitro skin permeation testing over 24 h and sacrificial timepoint penetration experiments (at 1, 4, 8, 12, and 24 h) were conducted using an automated flow-through diffusion cell system. The amount of drug delivered to the epidermis, dermis, and receptor solution (representing deeper tissue) was determined by liquid chromatography-tandem mass spectrometry. Skin protein binding of ibuprofen and diclofenac was investigated by spiking skin homogenate with increasing concentrations of each drug and determining the fraction unbound.

RESULTS

Differences were observed in the amount of drug recovered at sacrificial timepoints and rate at which drug was delivered to the target site between plaster and gel formulations of ibuprofen and diclofenac and between plaster formulations of the same drug (ibuprofen). While the amount of drug quantified at sacrificial timepoints did not necessarily determine in vivo flux rates, differences in drug distribution within the skin layers indicated where drug reservoirs were formed.

CONCLUSIONS

These findings highlight the importance of intelligent formulation design in determining NSAID delivery through skin layers. Further work is required to quantify drug delivery into deeper tissues and the resultant local anti-inflammatory effects.

Chitosan-based microneedles as a potential platform for drug delivery through the skin: Trends and regulatory aspects

Microneedles (MNs) fabrication using chitosan has gained significant interest due to its ability of film-forming, biodegradability, and biocompatibility, making it suitable for topical and transdermal drug delivery. The presence of amine and hydroxyl functional groups on chitosan permits the modification with tunable properties and functionalities. In this regard, chitosan is the preferred material for fabrication of MNs because it does not produce an immune response in the body and can be tailored as per required strength and functionalities. Therefore, many researchers have attempted to use chitosan as a drug delivery vehicle for hydrophilic drugs, peptides, and hormones. In 2020, the FDA has issued "Regulatory Considerations for Microneedling Products". This official guidance is a sign for future opportunities in the development of MNs. The present review focuses on properties, and modifications of chitosan used in the fabrication of MNs. The therapeutic and diagnostic applications of different types of chitosan-based MNs have been discussed. Further, the regulatory aspects of MN-based devices, and patents related to chitosan-based MNs are discussed.

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.

Safety, Tolerability, and Pharmacokinetics of Ibuprofenamine Hydrochloride Spray (NSAIDs), a New Drug for Rheumatoid Arthritis and Osteoarthritis, in Healthy Chinese Subjects

Background

Ibuprofenamine hydrochloride spray is novel transdermal nonsteroidal anti-inflammatory drugs (NSAIDs), under clinical development for the treatment of Rheumatoid Arthritis and Osteoarthritis as a novel transdermal drug.

Methods

A single and multiple ascending dose study investigated the safety, tolerability and pharmacokinetics of ibuprofenamine hydrochloride in healthy Chinese subjects. A total of 34 subjects (single-dose study: 34 subjects and multiple-dose study: 20 subjects) were involved in the trial. In the single-dose study, subjects were assigned to one of the four groups received 35, 70, 140, 280 mg. In the 70 mg and 140 mg treatment groups, subjects received one dose on the first day and twice a day from day 6 to 12. The starting dose was determined considering the no observed adverse effect level based on preclinical studies, and the dose escalations in subsequent cohorts were decided based on safety, tolerability, and pharmacokinetic data from previous dose cohorts.

Results

After a single dose, both ibuprofenamine and ibuprofen plasma exposure showed a more than dose-proportional increase across a dose range of 35–280 mg. After multiple dosing, both ibuprofenamine and ibuprofen steady-state exposure increased obviously more than dose-proportional manner across the evaluated dose range (twice a day for 7 days) resulted in obvious accumulation. Single or multiple doses of ibuprofenamine hydrochloride were generally well tolerated and no obvious skin irritation was observed.

Conclusion

Ibuprofenamine hydrochloride exhibited a safety and pharmacokinetic profile that supports its future investigation as a potential therapeutic for Rheumatoid Arthritis and Osteoarthritis.

Enhancement strategies for transdermal drug delivery systems: current trends and applications

Transdermal drug delivery systems have become an intriguing research topic in pharmaceutical technology area and one of the most frequently developed pharmaceutical products in global market. The use of these systems can overcome associated drawbacks of other delivery routes, such as oral and parenteral. The authors will review current trends, and future applications of transdermal technologies, with specific focus on providing a comprehensive understanding of transdermal drug delivery systems and enhancement strategies. This article will initially discuss each transdermal enhancement method used in the development of first-generation transdermal products. These methods include drug/vehicle interactions, vesicles and particles, stratum corneum modification, energy-driven methods and stratum corneum bypassing techniques. Through suitable design and implementation of active stratum corneum bypassing methods, notably microneedle technology, transdermal delivery systems have been shown to deliver both low and high molecular weight drugs. Microneedle technology platforms have proven themselves to be more versatile than other transdermal systems with opportunities for intradermal delivery of drugs/biotherapeutics and therapeutic drug monitoring. These have shown that microneedles have been a prospective strategy for improving transdermal delivery systems.

The bioavailability of cytarabine in dogs with meningoencephalitis of unknown etiology through iontophoresis and rectal delivery

Background:

Cytarabine (CA) is used to treat dogs with meningoencephalitis of unknown etiology (MUE) by subcutaneous or intravenous administration.

Aim:

The objective was to investigate transdermal iontophoresis and rectal administration as alternative routes of CA delivery.

Methods:

Two client-owned dogs with MUE were studied. The ActivaPatch® IONTOGO™ 12.0 iontophoresis drug delivery system delivered 200 mg/m2 CA transdermally. Blood samples were collected by sparse sampling technique after initiation of the device. At another visit, 100 mg/m2 CA was administered rectally. Blood samples were collected by sparse sampling technique after administration. Plasma CA concentrations were measured by high-pressure liquid chromatography.

Results:

The concentration of plasma CA after transdermal and rectal administration was below the limits of quantification (0.1 μg/ml) in all samples suggesting inadequate bioavailability with transdermal and rectal administration.

Conclusion:

Transdermal and rectal CA administration are not reasonable alternative routes of delivery.

Development and characterization of nano-emulsions and nano-emulgels for transdermal delivery of statins

BACKGROUND

Oral administration of statins for the treatment of familial hypercholesterolemia results in poor therapeutic outcomes and patient compliance. An alternative administration route is proposed to circumvent the current limitations. This research is aimed at developing nano-emulsions and nano-emulgels as the ultimate potential delivery systems of statins for administration via the transdermal route.

METHODS

Oil-in-water (o/w) nano-formulations (nano-emulsions and nano-emulgels) containing 2% (w/w) of the selected statin and 8% apricot kernel oil as oil phase were formulated. The nano-formulations were characterized using transmission electron microscopy (TEM), pH, viscosity, droplet size and zeta-potential.

RESULTS

Nano-emulsions' and nano-emulgels' droplet size ranged between 114.23-169.83 nm and 149.83-267.53 nm, respectively. The addition of Carbopol® Ultrez 20 increased the nano-emulsions' viscosity (3.59-8.38 cP) resulting in the formation of nano-emulgels (viscosity: 1911.00-46,090.00 cP). The entrapment efficiency (90.77-99.55%) confirmed the incorporation of the statins. Membrane release studies indicated that statins were released at higher flux values in nano-emulsions compared to their respective nano-emulgels. Ex vivo (skin diffusion) studies indicated higher median values in the nano-emulgels compared to their nano-emulsion counterparts.

CONCLUSIONS

The results indicate the benefits of nano-emulsions and nano-emulgels as potential alternative delivery systems for the transdermal delivery of statins.