Polymeric Microneedles Enhance Transdermal Delivery of Therapeutics

This research presents the efficacy of polymeric microneedles in improving the transdermal permeation of methotrexate across human skin. These microneedles were fabricated from PLGA Expansorb® 50-2A and 50-8A and subjected to comprehensive characterization via scanning electron microscopy, Fourier-transform infrared spectroscopy, and mechanical analysis. We developed and assessed a methotrexate hydrogel for physicochemical and rheological properties. Dye binding, histological examinations, and assessments of skin integrity demonstrated the effective microporation of the skin by PLGA microneedles. We measured the dimensions of microchannels in the skin using scanning electron microscopy, pore uniformity analysis, and confocal microscopy. The skin permeation and disposition of methotrexate were researched in vitro. PLGA 50-8A microneedles appeared significantly longer, sharper, and more mechanically uniform than PLGA 50-2A needles. PLGA 50-8A needles generated substantially more microchannels, as well as deeper, larger, and more uniform channels in the skin than PLGA 50-2A needles. Microneedle insertion substantially reduced skin electrical resistance, accompanied by an elevation in transepidermal water loss values. PLGA 50-8A microneedle treatment provided a significantly higher cumulative delivery, flux, diffusion coefficient, permeability coefficient, and predicted steady-state plasma concentration; however, there was a shorter lag time than for PLGA 50-2A needles, base-treated, and untreated groups (p < 0.05). Conclusively, skin microporation using polymeric microneedles significantly improved the transdermal delivery of methotrexate.

Unravelling the role of microneedles in drug delivery: Principle, perspectives, and practices

In recent year, the research of transdermal drug delivery systems has got substantial attention towards the development of microneedles (MNs). This shift has occurred due to multifaceted advantages of MNs as they can be utilized to deliver the drug deeper to the skin with minimal invasion, offer successful delivery of drugs and biomolecules that are susceptible to degradation in gastrointestinal tract (GIT), act as biosensors, and help in monitoring the level of biomarkers in the body. These can be fabricated into different types based on their applications as well as material for fabrication. Some of their types include solid MNs, hollow MNs, coated MNs, hydrogel forming MNs, and dissolving MNs. These MNs deliver the therapeutics via microchannels deeper into the skin. The coated and hollow MNs have been found successful. However, they suffer from poor drug loading and blocking of pores. In contrast, dissolving MNs offer high drug loading. These MNs have also been utilized to deliver vaccines and biologicals. They have also been used in cosmetics. The current review covers the different types of MNs, materials used in their fabrication, properties of MNs, and various case studies related to their role in delivering therapeutics, monitoring level of biomarkers/hormones in body such as insulin. Various patents and clinical trials related to MNs are also covered. Covered are the major bottlenecks associated with their clinical translation and potential future perspectives.

Dissolving microneedle patch-assisted transdermal delivery of methotrexate improve the therapeutic efficacy of rheumatoid arthritis

Methotrexate (MTX) is a first-line treatment for rheumatoid arthritis (RA), but its clinical use is greatly limited by the adverse effects and poor patient compliance caused by traditional oral administration or injection. In recent years, some transdermal drug delivery systems have received considerable attention due to overcoming these shortcomings. In this study, we developed dissolving microneedle patch (DMNP) for transdermal delivery of MTX to treat RA safely and effectively. The morphology, mechanical strength, skin insertion, drug content, in vitro transdermal delivery, and other properties of DMNP were characterized. Meanwhile, the adjuvant-induced arthritis model of rats was established to investigate the therapeutic effect of MTX-loaded DMNP in vivo. The results showed that the microneedles had excellent morphology with neat array and complete needles, good puncture performance and mechanical strength, and rapid intradermal dissolution rate. In vitro transdermal delivery results indicated that microneedles could significantly increase drug transdermal permeation compared with the cream group. The pharmacological study showed that MTX-loaded DMNP significantly alleviated paw swelling, inhibit inflammatory response via downregulating the levels of TNF-α and IL-1β, relieved synovium destruction with less cartilage erosion, and slowed the progression of RA in AIA rats. Besides, DMNP presented better therapeutic performance than cream or intragastric administration at the same dosage of MTX. In conclusion, the MTX-loaded dissolving microneedle patch has advantages of safety, convenience, and high efficacy over conventional administrations, laying a foundation for the transdermal drug delivery system treatment of rheumatoid arthritis.

Advances in microneedle-based therapy for bone disorders

Bone-related disorders treatment is a serious public health concern, imposing a significant social and economic burden on patients and healthcare systems. Although conventional drug delivery systems have made advances in bone diseases prevention and management, the limited delivery efficiency and convoluted focal environment lead to inadequate drug absorption and lack of specificity to achieve the intended therapeutic impact. Microneedle-based therapy represents an extraordinarily safe and well-tolerable therapeutic approach for treating bone disorders, providing improved efficacy by breaking down the barriers and delivery of therapeutic components to the target sites with programable release profiles in a less invasive manner. Over the past decades, numerous significant achievements in the development of various types of drug-carried microneedles have been made to address the obstacles encountered in the bone-treating procedure, enabling the microneedle-based therapy to take an important step in practical applications. In this light, this review summarizes these remarkable researches in terms of microneedles types and drug delivery strategies, with the goal of demonstrating the benefits of exploiting microneedle-based therapy as a novel strategy for treating bone-related disorders. The remaining challenges and future perspectives are also discussed in the hope of inspiring more efficient and intelligent bone treatment strategies.

Microneedles: materials, fabrication, and biomedical applications

The microneedles have attracted great interests for a wide range of transdermal biomedical applications, such as biosensing and drug delivery, due to the advantages of being painless, semi-invasive, and sustainable. The ongoing challenges are the materials and fabrication methods of the microneedles in order to obtain a specific shape, configuration and function of the microneedles to achieve a target biomedical application. Here, this review would introduce the types of materials of the microneedles firstly. The hardness, Young's modulus, geometric structure, processability, biocompatibility and degradability of the microneedles are explored as well. Then, the fabrication methods for the solid and hollow microneedles in recent years are reviewed in detail, and the advantages and disadvantages of each process are analyzed and compared. Finally, the biomedical applications of the microneedles are reviewed, including biosensing, drug delivery, body fluid extraction, and nerve stimulation. It is expected that this work provides the fundamental knowledge for developing new microneedle devices, as well as the applications in a variety of biomedical fields.

Promising Strategies for Transdermal Delivery of Arthritis Drugs: Microneedle Systems

Arthritis is a general term for various types of inflammatory joint diseases. The most common clinical conditions are mainly represented by rheumatoid arthritis and osteoarthritis, which affect more than 4% of people worldwide and seriously limit their mobility. Arthritis medication generally requires long-term application, while conventional administrations by oral delivery or injections may cause gastrointestinal side effects and are inconvenient for patients during long-term application. Emerging microneedle (MN) technology in recent years has created new avenues of transdermal delivery for arthritis drugs due to its advantages of painless skin perforation and efficient local delivery. This review summarizes various types of arthritis and current therapeutic agents. The current development of MNs in the delivery of arthritis drugs is highlighted, demonstrating their capabilities in achieving different drug release profiles through different self-enhancement methods or the incorporation of nanocarriers. Furthermore, the challenges of translating MNs from laboratory studies to the clinical practice and the marketplace are discussed. This promising technology provides a new approach to the current drug delivery paradigm in treating arthritis in transdermal delivery.

Recent Advances of Microneedles and Their Application in Disease Treatment

For decades, scientists have been doing a lot of research and exploration to find effective long-term analgesic and/or disease-modifying treatments. Microneedles (MNs) are a simple, effective, and painless transdermal drug delivery technology that has emerged in recent years, and exhibits great promise for realizing intelligent drug delivery. With the development of materials science and fabrication technology, the MN transdermal drug delivery technology has been applied and popularized in more and more fields, including chronic illnesses such as arthritis or diabetes, cancer, dermatocosmetology, family planning, and epidemic disease prevention, and has made fruitful achievements. This paper mainly reviews the latest research status of MNs and their fabrication methodology, and summarizes the application of MNs in the treatment of various diseases, as well as the potential to use nanotechnology to develop more intelligent MNs-based drug delivery systems.

Programmable Polymeric Microneedles for Combined Chemotherapy and Antioxidative Treatment of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease. Antioxidative treatment combined with chemotherapy holds great promise for RA treatment, and the ability to efficiently deliver drugs and antioxidants to the RA synovial joint is highly desired. Herein, we developed a programmable polymeric microneedle (MN) platform for transdermal delivery of methotrexate (MTX) and reactive oxygen species (ROS) scavengers for RA treatment. The biodegradable MNs made of polyvinylpyrrolidone (PVP) were incorporated with polydopamine/manganese dioxide (termed PDA@MnO₂) and MTX. After insertion into skin tissue, the MNs degraded, thus enabling release of loaded MTX and PDA@MnO₂. The PDA@MnO₂ could be utilized as an MRI contrast agent in the RA synovial microenvironment. It also acted as a robust antioxidant to remove ROS and decrease RA inflammation, which when combined with the MTX-mediated chemotherapy led to an ideal outcome for RA treatments in a murine model. This work not only represents a valuable MN-assisted RA therapeutic agent transdermal delivery approach but also opens a new avenue for chemotherapy and antioxidative synergistic treatment of RA.

Improved imiquimod-induced psoriasis like dermatitis using microneedles in mice

Psoriasis is a chronic inflammatory skin disease, in which the key features are epidermis hyperplasia, hyper-keratinization, leading to low drug absorption. As an approach of transdermal drug delivery, the microneedle (MN) has received increasing attentions for its painless penetration and efficient administration. In this study, we fabricated polylactic acid polymer MNs with hot-press method and established a psoriasis-like skin inflammation model in ear and dorsal skin of mice by topical application of imiquimod (IMQ). The dynamometer and insertion test of MNs into parafilm and skin of mice were done, revealing that the MNs have sufficient mechanical properties to insert parafilm and skin of mice. The two methods (apply calcipotriol (CAL) directly and pre-treat with MNs before applying CAL) were used to treat psoriasis and observe the skin inflammation, including skin and epidermal thickening, spleen weight gain, inflammatory cell infiltration, and expression of inflammatory cytokines of TNF-α. Both methods have a therapeutic effect and the effect of the MN pretreatment group is better. In addition, there are statistical differences between the two groups (P < 0.05). These features indicated that the MNs may be promising in future clinical applications in improving the imiquimod-induced psoriasis like dermatitis.

Localised and sustained intradermal delivery of methotrexate using nanocrystal-loaded microneedle arrays: Potential for enhanced treatment of psoriasis

Methotrexate (MTX), typically used as its sodium salt (MTX Na), is a first-line treatments for moderate to severe psoriasis, showing good efficacy. However, its systemic administration is associated with many side effects. Intradermal delivery into psoriatic tissue could offer an alternative approach. However, successful intradermal administration of MTX Na is currently precluded by its physicochemical properties. Moreover, due to its hydrophilic nature, MTX Na is swiftly cleared from the target tissue, necessitating frequent dosing which may affect patient compliance. To address these limitations, we investigated the combination of nanocrystal (NC) and dissolving microneedle (MN) technologies as an alternative approach for localised and sustained intradermal delivery of MTX Na. Poorly water-soluble MTX nanocrystals (MTX NC) were produced by a bottom-up technique with a mean particle size of 678 ± 15 nm. Sustained in vitro drug release was observed over 72 h. The MTX NC were then incorporated into the shafts of dissolving MN arrays with a drug loading of 2.48 mg/array. The MTX NC-loaded MN arrays exhibited satisfactory mechanical strength and insertion capabilities in the skin-simulant Parafilm M® and their shafts dissolved entirely in less than 20 min after insertion into excised neonatal porcine skin. Importantly, in vivo studies in Sprague Dawley rats revealed that the MN arrays were able to deposit approximately 25.1% of the loaded MTX NC in the skin, which acted, in turn, as a drug depot and released the MTX in a sustained manner over 72 h, while minimising MTX systemic exposure. Indeed, 24 h from MN application, 312.70 ± 161.95 µg/g of MTX was retained in the skin at the application site. This was approximately 322-fold higher than the amount of MTX (0.942 ± 0.59 µg/g) retained in the skin after oral administration of MTX Na. Interestingly, even after 72 h after MN application, around 12.5% of the MTX NC deposited in the skin by the MN was retained. In contrast, the maximal blood concentration of MTX achieved following MN application, was only 40% of that measured after oral administration of MTX Na. Accordingly, MTX NC-loaded dissolving MN arrays could be a promising approach for effective localised and sustained intradermal delivery of MTX as a potential enhanced treatment for psoriasis.

Enhanced Percutaneous Delivery of Methotrexate Using Micelles Prepared with Novel Cationic Amphipathic Material

BACKGROUND

Methotrexate (MTX) is an antiproliferative drug widely used to treat inflammatory diseases and autoimmune diseases. The application of percutaneous administration is hindered due to its poor transdermal penetration. To reduce side effects and enhanced percutaneous delivery of MTX, novel methotrexate (MTX)-loaded micelles prepared with a amphiphilic cationic material, N,N-dimethyl-(N',N'-di-stearoyl-1-ethyl)1,3-diaminopropane (DMSAP), was designed.

MATERIALS AND METHODS

DMSAP was synthesized via three steps using simple chemical agents. H nuclear magnetic resonance and mass spectroscopy were used to confirm the successful synthesis of DMSAP. A safe and non-toxic phosphatidylcholine, soybean phosphatidylcholine (SPC), was added to DMSAP at different ratios to form P/D-micelles. Then, MTX-entrapped micelles (M/P/D-micelles) were prepared by electrostatic adsorption. The physicochemical properties and blood stability of micelles were examined thoroughly. In addition, the transdermal potential of the micelles was evaluated by permeation experiments.

RESULTS

In aqueous environments, DMSAP conjugates could self-assemble spontaneously into micelles with a low critical micelle concentration (CMC) of 0.056 mg/mL. Stable, spherical MTX-entrapped micelles (M/P/D-micelles) with a size of 100-120 nm and high zeta potential of +36.26 mV were prepared. In vitro permeation studies showed that M/P/D-micelles exhibited superior skin permeability and deposition of MTX in the epidermis and dermis compared with that of free MTX.

CONCLUSION

These special novel cationic M/P/D-micelles can enhance the permeability of MTX and are expected to be a promising percutaneous delivery system for therapy skin diseases.

Effect of polymer microneedle pre-treatment on drug distributions in the skin in vivo

Solid microneedles (MNs) represent a useful tool for enhancing skin permeability by creating microchannels that provide a drug delivery route. To achieve the solid polymer MNs to become a clinical reality and to be commercialised, it is much essential to understand the skin penetration process. In this work, the effect of polymer MN height and density, drug molecular weight, as well as drug diffusion time on the drug permeability distribution was systemically investigated in vivo. MN with a height of 800 µm was most conductive to enhance the vertical distribution of drug permeation into the skin, while 11 × 11 MN array was most beneficial to promote the horizontal distribution of drug permeation into the skin. In addition, the increasing of drug molecular weight could reduce the drug permeability distribution and Fluorescein isothiocyanate most likely to penetrate into the skin after MNs pre-treatment. With the increase of drug diffusion time, the drug distribution in the subcutaneous gradually weakened until the drug was absorbed by the subcutaneous tissue at 8 h. These results suggest that the solid polymer MNs can penetrate the stratum corneum of the skin for enhancing drug delivery, especially small molecule drugs.

Hyaluronic Acid-Based Dissolving Microneedle Patch Loaded with Methotrexate for Improved Treatment of Psoriasis

Methotrexate (MTX) is one of the first-line treatments for moderate to severe psoriasis, while the side effects caused by injection and oral administration of MTX greatly restrict its clinical application. Transdermal drug delivery offers a desirable alternative to the conventional approaches, but the performances of the currently available skin penetration enhancement techniques are not so satisfactory. To address these limitations, we developed a dissolving microneedle (MN) patch made of hyaluronic acid (HA) with excellent water solubility, biocompatibility, biodegradability, and mechanical properties. The amount of MTX encapsulated in the needles of the patch could be controlled during the fabrication process for precise dosage. Interestingly, the MTX-loaded MNs successfully penetrated imiquimod (IMQ)-induced thickened epidermis in mice and delivered the drug intralesionally. Meanwhile, fast dissolution of HA endowed the MNs with operability for patients. We found that the MTX-loaded MNs not only showed well-maintained inhibitory effect in vitro but also alleviated the psoriasis-like skin inflammation in mice. Moreover, the MTX-loaded MNs were significantly more efficacious than taking the same dose of drug orally. Consequently, a higher oral dose of MTX was required for a comparable amelioration, which in turn increased its systemic toxicity. Taken together, the proposed MTX-loaded dissolving MN patch strategy provides a new opportunity for efficient and safe treatment of psoriasis.

Delivery of Methotrexate and Characterization of Skin Treated by Fabricated PLGA Microneedles and Fractional Ablative Laser

PURPOSE

This study investigated in vitro transdermal delivery of methotrexate through dermatomed porcine ear and cadaver human skin treated with poly (D,L-lactide-co-glycolide) acid microneedles or fractional ablative laser.

METHODS

PLGA microneedles were fabricated and characterized using scanning electron microscopy and mechanical assessment techniques. The integrity of treated skin was evaluated by rheometer, transepidermal water loss, and skin electrical resistance measurements. Successful skin microporation was demonstrated by dye binding, histology, pore uniformity, confocal laser microscopy, and DermaScan studies. In vitro permeation experiment was performed on Franz diffusion cells to determine drug delivery into and across the skin.

RESULTS

Both physical treatments resulted in a considerable decrease in skin resistance and an increase in transepidermal water loss value. The laser-created microchannels were significantly larger than those formed by microneedles (p < 0.05). An effective force of 41.04 ± 18.33 N was required to achieve 100% penetration efficiency of the microneedles. For both porcine ear and human skin, laser ablation provided a significantly higher methotrexate permeability into the receptor chamber and skin layers compared to microneedle poration and untreated skin (p < 0.05).

CONCLUSIONS

Both fractional ablative laser and polymeric microneedles markedly enhanced in vitro transdermal delivery of methotrexate into and across skin. Graphical Abstract ᅟ.

Novel in situ forming hydrogel microneedles for transdermal drug delivery

Novel in situ forming hydrogel microneedles were evaluated for transdermal drug delivery using a biocompatible non-ionic triblock amphiphilic thermosensitive copolymer. The transition property of poloxamer from solution at room temperature to gel at skin temperature (32 °C) was utilized in preparation of in situ forming hydrogel microneedles. Methotrexate has been used to treat solid tumors, but because of its narrow safety margin, it requires sustained delivery within the therapeutic window. Formulations with and without poloxamer at different methotrexate concentrations were prepared and evaluated for drug permeation across skin using vertical Franz diffusion cell for 72 h. Sol-gel transition, skin resistance and thickness, microneedles geometry, microchannel depth, shape, formation and uniformity, viscoelasticity of skin, and in vitro drug permeation were characterized and tested. An average cumulative drug amount of 32.2 ± 15.76 and 114.54 ± 40.89 μg/cm² for porcine ear skin and 3.89 ± 0.60 and 10.27 ± 6.98 μg/cm² for dermatomed human skin from 0.2 % w/w and 0.4 % w/w methotrexate formulations was delivered by the in situ forming hydrogel microneedles. These in situ hydrogel microneedles embedded within the porated site of the skin provided a steady and sustained drug delivery.

Topically applied methotrexate is rapidly delivered into skin by fractional laser ablation

OBJECTIVES

Methotrexate (MTX) is a chemotherapeutic and anti-inflammatory drug that may cause systemic adverse effects. This study investigated kinetics and biodistribution of MTX delivered topically by ablative fractional laser (AFXL).

METHODS

In vitro passive diffusion of 10 mg/ml MTX (1 w/v%) was measured from 0.25 to 24 h through AFXL-processed and intact porcine skin in Franz Cells (n = 46). A 2,940 nm fractional Erbium Yttrium Aluminium Garnet laser generated mid-dermal microchannels at 2.4% density, and 256 mJ/microchannel. HPLC quantified MTX-concentrations in extracts from mid-dermal skin sections, donor and receiver compartments. Fluorescence microscopy of UVC-activated MTX-fluorescence and desorption electro-spray ionization mass spectrometry imaging (DESI-MSI) evaluated MTX biodistribution.

RESULTS

AFXL-processed skin facilitated rapid MTX delivery through cone-shaped microchannels of 690 µm ablation depth, lined by the 47 µm thermal coagulation zone (CZ). Quantitatively, MTX was detectable by HPLC in mid-dermis after 15 min, significantly exceeded deposition in intact skin after 1.5 h, and saturated skin after 7 h at a 10-fold increased MTX-deposition versus intact skin (3.08 vs 0.30 mg/cm(3), p = 0.002). Transdermal permeation was < 1.5% of applied MTX before skin saturation, and increased up to 8.0% after 24 h. Qualitatively, MTX distributed into CZ within 15 min (p = 0.015) and further into surrounding dermal tissue after 1.5 h (p = 0.004). After skin saturation at 7 h, MTX fluorescence intensities in CZ and tissue were similar and DESI-MSI confirmed MTX biodistribution throughout the mid-dermal skin section.

CONCLUSIONS

MTX absorbs rapidly into mid-dermis of AFXL-processed skin with minimal transdermal permeation until skin saturation, suggesting a possible alternative to systemic MTX for some skin disorders.