Sustained-Release Hydrogen-Powered Bilateral Microneedles Integrating CD-MOFs for In Situ Treating Allergic Rhinitis

Glucocorticoids are widely used for treating allergic rhinitis, but conventional intranasal administration encounters unfavorable nasal cilia clearance and nasal mucosal barrier. Herein, a bilateral microneedle patch is fabricated for delivering cyclodextrin-based metal-organic frameworks (CD-MOF) encapsulating dexamethasone (DXMS) and paeonol (Pae), while NaH particles are mounted on the basal part of each microneedle. By intranasal administration, the microneedles are propelled into the nasal mucosa by NaH-generated hydrogen and then swell to form a hydrogel for sustainedly releasing drugs. The DXMS/Pae combination is demonstrated to be superior to more than the twofold dose of DXMS alone for improving allergic rhinitis in rats. It involves reducing mast cell degranulation and modulating Treg/Th17 cell homeostasis, whereas inhibiting Th1 to Th2 differentiation is associated with regulating the GATA3/T-bet pathway, as well as repairing epithelial barrier function by increasing MUC1 and downregulating periostin. In addition, this delivery system modulates the lipid metabolism of the nasal mucosa. Notably, the newly designed device significantly enhances the drug's therapeutic effect, and NaH-generated hydrogen may have the potential adjunctive therapeutic effect. Collectively, such an emerging microneedle-mediated nasal drug delivery creates a new form for alleviating immune inflammation and contributes a promising solution to reduce clinical glucocorticoid abuse.

3D DLP-printed cannabinoid microneedles patch and its pharmacokinetic evaluation in rats

OBJECTIVE

The objective of the present study was to enhance the bioavailability of cannabidiol (CBD) using 3D Digital Light Processing (DLP)-printed microneedle (MN) transdermal drug delivery system.

METHODS

CBD MN patch was fabricated and optimized using 3D DLP printing using CBD (8% w/v), Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) (0.49% w/v), distilled water (20% w/v), and poly (ethylene glycol) dimethacrylate 550 (PEGDAMA 550) (up to 100% w/v). CBD MNs were characterized for their morphology, mechanical strength, in vitro release study, ex vivo permeation study, and in vivo pharmacokinetic (PK) profile.

KEY FINDINGS

Microscopic images showed that sharp CBD MNs with a height of ~800 μm, base diameter of ~250 μm, and tip with a radius of curvature (RoC) of ~15 μm were successfully printed using optimized printing parameters. Mechanical strength studies showed no significant deformation in the morphology of CBD MNs even after applying 0.5N/needle force. Ex vivo permeation study showed significant (P < .0001) permeation of CBD in the receiving media as compared to CBD patch (control). In vivo PK study showed significantly (P < .05) enhanced bioavailability in the case of CBD MN patch as compared to CBD subcutaneous inj. (control).

CONCLUSION

Overall, systemic absorption of CBD was significantly enhanced using 3D-printed MN drug delivery system.

Minoxidil Nanosuspension-Loaded Dissolved Microneedles for Hair Regrowth

Minoxidil (MIN) is used topically to treat alopecia. However, its low absorption limits its use, warranting a new strategy to enhance its delivery into skin layers. The objective of this study was to evaluate the dermal delivery of MIN by utilizing dissolved microneedles (MNs) loaded with MIN nanosuspension (MIN-NS) for hair regrowth. MIN-NS was prepared by the solvent-antisolvent precipitation technique. The particle size of MIN-NS was 226.7 ± 9.3 nm with a polydispersity index of 0.29 ± 0.17 and a zeta potential of -29.97 ± 1.23 mV. An optimized formulation of MIN-NS was selected, freeze-dried, and loaded into MNs fabricated with sodium carboxymethyl cellulose (Na CMC) polymeric solutions (MIN-NS-loaded MNs). MNs were evaluated for morphology, dissolution rate, skin insertion, drug content, mechanical properties, ex vivo permeation, in vivo, and stability studies. MNs, prepared with 14% Na CMC, were able to withstand a compression force of 32 N for 30 s, penetrate Parafilm M® sheet at a depth of 374-504 µm, and dissolve completely in the skin within 30 min with MIN %recovery of 95.1 ± 6.5%. The release of MIN from MIN-NS-loaded MNs was controlled for 24 h. MIN-NS-loaded MNs were able to maintain their mechanical properties and chemical stability for 4 weeks, when kept at different storage conditions. The in vivo study of the freeze-dried MIN-NS and MIN-NS-loaded MNs proved hair regrowth on rat skin after 11 and 7 days, respectively. These results showed that MIN-NS-loaded MNs could potentially improve the dermal delivery of MIN through the skin to treat alopecia.

Engineering Hyaluronic Acid Microneedles Loaded with Mn2+ and Temozolomide for Topical Precision Therapy of Melanoma

Topical therapy has received worldwide attention for in situ tumors owing to its higher efficacy of drug delivery. Herein, this work reports a dissolvable multifunctional hyaluronic acid microneedles (HMNs) patch coloaded with temozolomide (TMZ) and MnCl2 (TMZ/MnCl2@HMN) for chemoimmunotherapy of melanoma. HMNs can ensure the stability of TMZ over time, and exhibit fewer side effects with a localized release way. In particular, TMZ not only promotes dendritic cell maturation by triggering immunogenic cell death in tumor cells, but also induces DNA damage that can further enhance the Mn2+-activated cGAS-STING (stimulator of interferon genes pathway). As a result, the TMZ/MnCl2@HMN multifunctional platform significantly inhibits lung metastases for melanoma, providing a practical strategy for precision therapy of melanoma.

HPMC/PVP K90 Dissolving Microneedles Fabricated from 3D-Printed Master Molds: Impact on Microneedle Morphology, Mechanical Strength, and Topical Dissolving Property

Three-dimensional (3D) printing can be used to fabricate custom microneedle (MN) patches instead of the conventional method. In this work, 3D-printed MN patches were utilized to fabricate a MN mold, and the mold was used to prepare dissolving MNs for topical lidocaine HCl (L) delivery through the skin. Topical creams usually take 1-2 h to induce an anesthetic effect, so the delivery of lidocaine HCl from dissolving MNs can allow for a therapeutic effect to be reached faster than with a topical cream. The dissolving-MN-patch-incorporated lidocaine HCl was constructed from hydroxypropyl methylcellulose (HPMC; H) and polyvinyl pyrrolidone (PVP K90; P) using centrifugation. Additionally, the morphology, mechanical property, skin insertion, dissolving behavior, drug-loading content, drug release of MNs and the chemical interactions among the compositions were also examined. H51P2-L, H501P2-L, and H901P2-L showed an acceptable needle appearance without bent tips or a broken structure, and they had a low % height change (<10%), including a high blue-dot percentage on the skin (>80%). These three formulations exhibited a drug-loading content approaching 100%. Importantly, the composition-dependent dissolving abilities of MNs were revealed. Containing the lowest amount of HPMC in its formulation, H901P2-L showed the fastest dissolving ability, which was related to the high amount of lidocaine HCl released through the skin. Moreover, the results of an FTIR analysis showed no chemical interactions among the two polymers and lidocaine HCl. As a result, HPMC/PVP K90 dissolving microneedles can be used to deliver lidocaine HCl through the skin, resulting in a faster onset of anesthetic action.

Mechanical Characterization of Dissolving Microneedles: Factors Affecting Physical Strength of Needles

Dissolving microneedles (MNs) are novel transdermal drug delivery systems that can be painlessly self-administered. This study investigated the effects of experimental conditions on the mechanical characterization of dissolving MNs for quality evaluation. Micromolding was used to fabricate polyvinyl alcohol (PVA)-based dissolving MN patches with eight different cone-shaped geometries. Axial force mechanical characterization test conditions, in terms of compression speed and the number of compression needles per test, significantly affected the needle fracture force of dissolving MNs. Characterization using selected test conditions clearly showed differences in the needle fracture force of dissolving MNs prepared under various conditions. PVA-based MNs were divided into two groups that showed buckling and unbuckling deformation, which occurred at aspect ratios (needle height/base diameter) of 2.8 and 1.8, respectively. The needle fracture force of PVA-based MNs was negatively correlated with an increase in the needle's aspect ratio. Higher residual water or higher loading of lidocaine hydrochloride significantly decreased the needle fracture force. Therefore, setting appropriate methods and parameters for characterizing the mechanical properties of dissolving MNs should contribute to the development and supply of appropriate products.

Advances in Formulations of Microneedle System for Rheumatoid Arthritis Treatment

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic joint inflammation, eventually leading to severe disability and premature death. At present, the treatment of RA is mainly to reduce inflammation, swelling, and pain. Commonly used drugs are non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, and disease-modifying anti-rheumatic drugs (DMARDs). These drugs lack specificity and require long-term, high-dose administration, which can cause serious adverse effects. In addition, the oral, intravenous, and intra-articular injections will reduce patient compliance, resulting in high cost and low bioavailability. Due to these limitations, microneedles (MNs) have emerged as a new strategy to efficiently localize the drugs in inflamed joints for the treatment of RA. MNs can overcome the cuticle barrier of the skin without stimulating nerves and blood vessels. Which can increase patient compliance, improve bioavailability, and avoid systemic circulation. This review summarizes and evaluates the application of MNs in RA, especially dissolving MNs (DMNs). We encourage the use of MNs to treat RA, by describing the general properties of MNs, materials, preparation technology, drug release mechanism, and advantages. Furthermore, we discussed the biological safety, development prospects, and future challenges of MNs, hoping to provide a new strategy for the treatment of RA.

Construction and application of microneedle-mediated photothermal therapy and immunotherapy combined anti-tumor drug delivery system

Conventional treatments for tumors were frequently accompanied by drawbacks and side effects. It might be useful to use the revolutionary microneedle technology which combines photothermal therapy with tumor immunotherapy. In this study, we created a microneedle drug delivery system with mercapto-modified gold nanorods and immune checkpoint blocker anti-PD-1 polypeptide. With good mechanical strength, the microneedle system can efficiently penetrate the skin and deliver drugs. When inserted into human skin, anti-PD-1 peptides and gold nanorods can be released, boosting the capacity of cytotoxic T lymphocytes to destroy tumor cells. Additionally, the elimination of the tumor is aided by the production of heat while being exposed to near-infrared light. This microneedle drug delivery system can enhance the immunological reaction and prolong the survival time of mice. Moreover, it has been demonstrated that the system has mild toxic and side effects on normal tissues and can effectively inhibit the growth of tumors, indicating a bright prospect for the treatment of cancers.

The Progress in the Application of Dissolving Microneedles in Biomedicine

In recent years, microneedle technology has been widely used for the transdermal delivery of substances, showing improvements in drug delivery effects with the advantages of minimally invasive, painless, and convenient operation. With the development of nano- and electrochemical technology, different types of microneedles are increasingly being used in other biomedical fields. Recent research progress shows that dissolving microneedles have achieved remarkable results in the fields of dermatological treatment, disease diagnosis and monitoring, and vaccine delivery, and they have a wide range of application prospects in various biomedical fields, showing their great potential as a form of clinical treatment. This review mainly focuses on dissolving microneedles, summarizing the latest research progress in various biomedical fields, providing inspiration for the subsequent intelligent and commercial development of dissolving microneedles, and providing better solutions for clinical treatment.

Dissolving and Swelling Hydrogel-Based Microneedles: An Overview of Their Materials, Fabrication, Characterization Methods, and Challenges

Polymeric hydrogels are a complex class of materials with one common feature-the ability to form three-dimensional networks capable of imbibing large amounts of water or biological fluids without being dissolved, acting as self-sustained containers for various purposes, including pharmaceutical and biomedical applications. Transdermal pharmaceutical microneedles are a pain-free drug delivery system that continues on the path to widespread adoption-regulatory guidelines are on the horizon, and investments in the field continue to grow annually. Recently, hydrogels have generated interest in the field of transdermal microneedles due to their tunable properties, allowing them to be exploited as delivery systems and extraction tools. As hydrogel microneedles are a new emerging technology, their fabrication faces various challenges that must be resolved for them to redeem themselves as a viable pharmaceutical option. This article discusses hydrogel microneedles from a material perspective, regardless of their mechanism of action. It cites the recent advances in their formulation, presents relevant fabrication and characterization methods, and discusses manufacturing and regulatory challenges facing these emerging technologies before their approval.

Sublingual Dissolving Microneedle (SLDMN)-Based Vaccine for Inducing Mucosal Immunity against SARS-CoV-2

The coronavirus pandemic has accelerated the development of next-generation vaccination technology to combat future pandemic outbreaks. Mucosal vaccination effectively protects the mucosal surfaces, the primary sites of viral entry, by inducing the secretion of immunoglobulin A (IgA) and humoral IgG. Here, a dissolving microneedle (DMN) is adopted as a mucosal vaccine delivery platform to directly penetrate the sublingual site, which is rich in antigen-presenting cells (APCs) and lymphoid tissues. The sublingual dissolving microneedle (SLDMN) vaccination platform comprised a micropillar-based compartment and a 3D-printed SLDMN applicator as a substitute for the DMN patch. The penetration efficacy of SLDMNs is assessed using in vitro optical coherence tomography (OCT) and in vivo histological analysis. The efficacy of SLDMN is also evaluated in a vaccine form using the recombinant spike (S1) protein of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Furthermore, SLDMN is used to challenge transgenic mice expressing human angiotensin-converting enzyme 2 (hACE2) receptors. Its effects are evaluated on antibody production, survival rate, and inflammation attenuation after infection compared to the intramuscular (IM) injections. Overall, SLDMN effectively induced mucosal immunity via IgA secretion, attenuated lung inflammation, and lowered the levels of cytokines and chemokines, which may prevent the "cytokine storm" after SARS-CoV-2 infection.

Nanosuspension-Based Dissolvable Microneedle Arrays to Enhance Diclofenac Skin Delivery

Applying a formulation on the skin represents a patient-acceptable and therapeutically effective way to administer drugs locally and systemically. However, the stratum corneum stands as an impermeable barrier that only allows a very limited number of drugs to be distributed in the underlying tissues, limiting the feasibility of this administration route. Microneedle arrays are minimally invasive platforms that allow the delivery of drugs within/across the skin through the temporary mechanical disruption of the stratum corneum. In this work, microneedle arrays were combined with nanosuspensions, a technology for solubility enhancement of water insoluble molecules, for the skin delivery of diclofenac. Nanosuspensions were prepared using a top-down method and loaded in the tips of 500 µm or 800 µm high microneedles. The quality of the combined platform was assessed using electron microscopy and spectroscopic and calorimetry techniques, demonstrating the ability to load high amounts of the hydrophobic drug and the compatibility between excipients. Lastly, the application of nanosuspension-loaded microneedles on the skin in vitro allowed the delivery of diclofenac within and across the stratum corneum, proving the potential of this combination to enhance skin delivery of scarcely soluble drugs.

Collagen-Based Dissolving Microneedles with Flexible Pedestals: A Transdermal Delivery System for Both Anti-Aging and Skin Diseases

Biocompatible polymer microneedles (MNs) are emerging as a promising platform for transdermal drug delivery, especially for facial treatments. Therefore, an MN patch in this study uses hydrolyzed collagen (HC) contained in skin cells as the main raw material and adopts a two-step cast method to develop a rapidly dissolving microneedle (DMN) to deliver collagen in a simple and minimally invasive way, allowing the release of the encapsulated drug in the skin. By optimizing the formulation and proportion of HC and auxiliary support materials, the mechanical strength required to pierce the skin is obtained, while the soft pedestal allows for flexibility in application. The DMNs can dissolve completely in the skin within 15 min and release within ≈ 8 h, and do not cause toxicity or irritation when being applied. In contrast to the ineffectiveness of oral and external application, and the high risk of dermal injection, drug-loaded DMNs overcome the drawbacks of traditional methods with direct penetration and minimally invasive manner, enabling efficient and safe treatment. The successful preparation and research of HC DMNs have innovative and practical significance in this field, and it is expected to become a simple, effective, and popular transdermal drug delivery platform for cosmetics.

Mechanically Robust Dissolving Microneedles Made of Supramolecular Photosensitizers for Effective Photodynamic Bacterial Biofilm Elimination

Bacterial biofilms pose severe threats to public health worldwide and are intractable by conventional antibiotic treatment. Antimicrobial photodynamic therapy (PDT) is emerging as a promising strategy for eradicating biofilms by virtue of low invasiveness, broad-spectrum antibacterial activity, and nondrug resistance. However, its practical efficacy is impeded by the low water solubility, severe aggregation, and poor penetration of photosensitizers (PSs) into the dense extracellular polymeric substances (EPS) of biofilms. Herein, we develop a dissolving microneedle (DMN) patch composed of a sulfobutylether-β-cyclodextrin (SCD)/tetra(4-pyridyl)-porphine (TPyP) supramolecular PS for enhanced biofilm penetration and eradication. The inclusion of TPyP into the SCD cavity can drastically inhibit the aggregation of TPyP, thereby allowing for nearly tenfold reactive oxygen species production and high photodynamic antibacterial efficacy. Moreover, the TPyP/SCD-based DMN (TSMN) possesses excellent mechanical performance that can easily pierce the EPS of biofilm with a penetration depth of ∼350 μm, enabling sufficient contact of TPyP with bacteria and optimal photodynamic elimination of bacterial biofilms. Furthermore, TSMN could efficiently eradicate Staphylococcus aureus biofilm infection in vivo with good biosafety. This study offers a promising platform for supramolecular DMN for efficient biofilm elimination and other PDTs.

Hybrid Dissolving Microneedle-Mediated Delivery of Ibuprofen: Solubilization, Fabrication, and Characterization

Microneedles have recently emerged as a promising platform for delivering therapeutic agents by disrupting the skin, resulting in improved and high drug delivery via this route. Ibuprofen is widely used topically and orally for chronic pain conditions; to avoid untoward gastric effects, topical application is preferred over the oral route. This study aimed to enhance the solubility of the poorly water-soluble ibuprofen using Soluplus (SP) as a solubilizer and to fabricate dissolving microneedle patches of the drug. The fabricated patches were compared with marketed oral and topical formulations of ibuprofen. A 432-fold increase was observed in the solubility of the drug at 8% SP. The FTIR studies revealed that the drug and polymers were compatible. MNs were of uniform morphology and released the drug in a predictable manner. The in vivo analysis on healthy human volunteers revealed a Cmax of 28.7 µg/mL ± 0.5 with a T_max of 24 h and a MRT of 19.5 h, which was significantly higher than that observed for commercially available topical formulations. The prepared ibuprofen microneedles have higher bioavailability and MRT at a lower dose (165 µg) as compared to tablet and cream doses (200 mg).

Dissolving Microneedles Loaded with Nanoparticle Formulation of Respiratory Syncytial Virus Fusion Protein Virus-like Particles (F-VLPs) Elicits Cellular and Humoral Immune Responses

Respiratory syncytial virus (RSV) is one of the leading causes of bronchiolitis and pneumonia in children ages five years and below. Recent outbreaks of the virus have proven that RSV remains a severe burden on healthcare services. Thus, a vaccine for RSV is a need of the hour. Research on novel vaccine delivery systems for infectious diseases such as RSV can pave the road to more vaccine candidates. Among many novel vaccine delivery systems, a combined system with polymeric nanoparticles loaded in dissolving microneedles holds a lot of potential. In this study, the virus-like particles of the RSV fusion protein (F-VLP) were encapsulated in poly (D, L-lactide-co-glycolide) (PLGA) nanoparticles (NPs). These NPs were then loaded into dissolving microneedles (MNs) composed of hyaluronic acid and trehalose. To test the in vivo immunogenicity of the nanoparticle-loaded microneedles, Swiss Webster mice were immunized with the F-VLP NPs, both with and without adjuvant monophosphoryl lipid A (MPL) NPs loaded in the MN. The mice immunized with the F-VLP NP + MPL NP MN showed high immunoglobulin (IgG and IgG2a) levels both in the serum and lung homogenates. A subsequent analysis of lung homogenates post-RSV challenge revealed high IgA, indicating the generation of a mucosal immune response upon intradermal immunization. A flowcytometry analysis showed high CD8+ and CD4+ expression in the lymph nodes and spleens of the F-VLP NP + MPL NP MN-immunized mice. Thus, our vaccine elicited a robust humoral and cellular immune response in vivo. Therefore, PLGA nanoparticles loaded in dissolving microneedles could be a suitable novel delivery system for RSV vaccines.

Supramolecular Dissolving Microneedle Patch Loading Hydrophobic Glucocorticoid for Effective Psoriasis Treatment

Glucocorticoid-based creams are commonly used for treatments of psoriatic skin lesions while showing poor permeation because the thickened stratum corneum severely limits drug absorption. Although dissolving microneedle (DMN) patches have been employed in treating skin disease by virtue of their direct target to the lesion site, conventional DMN patches are generally fabricated from the water-soluble matrix, making them difficult to efficiently encapsulate hydrophobic glucocorticoids. Here, we develop a mechanically robust supramolecular DMN composed of hydroxypropyl β-cyclodextrin (HPCD) to effectively and uniformly load triamcinolone acetonide (TA). The TA-loaded HPCD DMN (TAMN) exhibits excellent mechanical performance that can easily pierce the thickened psoriasis lesions and deliver TA efficiently. Owing to the increased water solubility and bioavailability of TA after inclusion into HPCD, TAMN shows a superior in vitro inhibitory effect on immortalized human keratinocyte (HaCaT) cells. Importantly, the administration of TAMN twice a week effectively alleviates psoriatic signs and reduces the expression of Ki67, IL-23, and IL-17 in the ear lesions of imiquimod-induced psoriasis-like mice. This supramolecular DMN provides a promising strategy for the efficient treatment of psoriasis and other skin diseases, greatly broadens the applications of supramolecular materials in transdermal drug delivery, and widens the range of drugs in DMNs.

Rapidly Dissolving Microneedles for the Delivery of Steroid-Loaded Nanoparticles Intended for the Treatment of Inflammatory Skin Diseases

Drug delivery through the skin has immense advantages compared to other routes of administration and offers an optimal way to treat inflammatory skin diseases, where corticosteroids are the cornerstone of topical therapy. Still, their therapeutic efficiency is limited due to inadequate skin permeability, potential side effects, and reduced patient compliance. To overcome these drawbacks, we propose a drug delivery system consisting of dexamethasone (DEX)-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) incorporated in sodium alginate (SA) microneedles (MNs) as a minimally invasive dosage form for controlled drug release. Drug-loaded PLGA NPs were prepared by a nanoprecipitation method with a high encapsulation yield. They exhibited a controlled release pattern over 120 h. A modified vacuum-deposition micromolding method was used to load the obtained DEX-NPs into the tips of dissolving MNs. The NP-MNs showed improved insertion capabilities into the skin-simulant parafilm model and enhanced mechanical strength when tested against different static forces compared to their counterparts (SA-MNs). The results of an MN dissolution study following application to ex vivo chicken skin and agarose gel indicate that the NP-loaded segments of MNs dissolve within 15 s, in which the NPs are released into the skin. Taken together, the incorporation of DEX-NPs into SA-MNs could be a promising approach to bypass the limitations of conventional topical treatment of skin diseases, allowing for self-administration, increased patient compliance, and controlled drug release.

Transdermal delivery of celecoxib and α-linolenic acid from microemulsion-incorporated dissolving microneedles for enhanced osteoarthritis therapy

Dissolving microneedles, the promising vehicles for transdermal delivery, are incapable of directly loading hydrophobic components that limit the application of transdermal drug delivery. Microemulsion holds great potential in the solubilisation of water-insoluble drugs but is limited by the high epidermal retention. In this study, we fabricated microemulsion-incorporated dissolving microneedles co-loading celecoxib and α-linolenic acid (Cel-MEs@MNs) for enhancing osteoarthritis (OA) therapy via synergistic anti-inflammation and potent transdermal delivery. Cel-MEs@MNs composed of celecoxib & α-linolenic acid-coloaded microemulsion (Cel-MEs) and hyaluronic acid-based microneedles (MNs) can be completely dissolved in 90 s with a particle size of ∼30 nm. Each microneedle array with a hardness exceeding 30 N contained 57.9 ± 2.5 μg of celecoxib and 442.5 ± 24.2 μg of α-linolenic acid. The 8 h-cumulative transdermal of celecoxib from Cel-MEs@MNs was 89.2 ± 5.1 μg celecoxib/cm², which is 2.98-fold higher than that from Cel-MEs. Combinational celecoxib and α-linolenic acid with a weight ratio of 1/5 can synergistically induce M1-like macrophage to M2 repolarization, reduce M1-like macrophages-resulted chondrocytes apoptosis, and lower serum prostaglandin E-2 (PGE-2). Notably, Cel-MEs@MNs amplified such collaborated anti-inflammatory effects. More importantly, in the treatment of OA-bearing rat models, Cel-MEs@MNs with a half-dose of celecoxib and α-linolenic acid significantly shrunk the paw swelling, reduced inflammatory cytokines, and improved cartilage damage compared with the oral administration of celecoxib and α-linolenic acid, as well as transdermal administration of Cel-MEs. Such an integrational strategy of microemulsion-incorporated dissolving MNs offers the feasibility of combinational celecoxib and α-linolenic acid in transdermal permeation and boosted OA therapy.

Enhancing Intradermal Delivery of Lidocaine by Dissolving Microneedles: Comparison between Hyaluronic Acid and Poly(Vinyl Pyrrolidone) Backbone Polymers

Lidocaine hydrochloride (LiH), an amide-type local anesthetic agent, is commonly used in dermatological procedures. LiH is categorized as a BCS (biopharmaceutics classification system) class III group, which has high solubility and poor permeability. It should be noted that, in this context, LiH is intended as a local anesthetic, so the level of LiH in systemic circulation should be minimized to avoid toxicity and unwanted side effects such as hypotension and bradycardia. This study aimed to formulate and evaluate LiH-loaded dissolving microneedles (DMNs) with different polymer bases. Moreover, an in vitro permeation study using Franz diffusion cells and in vivo study were also performed. LiH-loaded DMNs were prepared using polymer groups of poly(vinyl pyrrolidone) (PVP-K30) and hyaluronic acid (HA). DMNs were created using the micro-molding method with centrifugation. The formulations selected based on the evaluation were F3 (HA 10%) and F5 (PVP-K30 25%). Based on the in vitro permeation study, the amount of drug permeated and deposited in the skin at F3 (HA 10%) was 247.1 ± 41.85 and 98.35 ± 12.86 μg, respectively. On the other hand, the amount of drug permeated and deposited in the skin at F5 (PVP-K30 25%) was 277.7 ± 55.88 and 59.46 ± 9.25 μg, respectively. Our in vivo drug-permeation study showed that only one rat from the PVP-K30 polymer group-with a concentration of 150.32 ng/mL-was detected on rat plasma. Therefore, LiH can be formulated into a DMN and can be deposited in the skin with a safe concentration of the drug permeating into systemic circulation.

Demonstrating Biological Fate of Nanoparticle-Loaded Dissolving Microneedles with Aggregation-Caused Quenching Probes: Influence of Application Sites

Integrating dissolving microneedles (DMNs) and nanocarriers (NC) holds great potential in transdermal drug delivery because it can simultaneously overcome the stratum corneum barrier and achieve efficient and controlled drug delivery. However, different skin sites with different thicknesses and compositions can affect the transdermal diffusion of NC-loaded DMNs. There are few reports on the biological fate (especially transdermal diffusion) of NC-loaded DMNs, and inaccurate bioimaging information of intact NC limits the accurate understanding of the in vivo fate of NC-loaded DMNs. The aggregation-caused quenching (ACQ) probes P4 emitted intense fluorescence signals in intact NC while quenched after the degradation of NC, had been demonstrated the feasibility of label intact NC. In this study, P4 was loaded in solid lipid nanoparticles (SLNs), and further encapsulated into DMNs, to track the transdermal diffusion of SLNs delivered at different skin sites. The results showed that SLNs had excellent stability after being loaded into DMNs with no significant changes in morphology and fluorescence properties. The in vivo live and ex vivo imaging showed that the transdermal diffusion rate of NC-loaded DMNs was positively correlated with skin thickness, with the order ear > abdomen > back. In conclusion, this study confirmed the site-dependency of transdermal diffusion in NC-loaded DMNs.

Deferasirox Nanosuspension Loaded Dissolving Microneedles for Intradermal Delivery

Microneedles are minimally invasive systems that can deliver drugs intradermally without pain and bleeding and can advantageously replace the hypodermal needles and oral routes of delivery. Deferasirox (DFS) is an iron chelator employed in several ailments where iron overload plays an important role in disease manifestation. In this study, DFS was formulated into a nanosuspension (NSs) through wet media milling employing PVA as a stabilizer and successfully loaded in polymeric dissolving microneedles (DMNs). The release studies for DFS-NS clearly showed a threefold increased dissolution rate compared to pure DFS. The mechanical characterization of DFS-NS-DMNs revealed that the system was sufficiently strong for efficacious skin penetration. Optical coherence tomography images confirmed an insertion of up to 378 µm into full-thickness porcine skin layers. The skin deposition studies showed 60% drug deposition from NS-DMN, which was much higher than from the DFS-NS transdermal patch (DFS-NS-TP) (without needles) or pure DFS-DMNs. Moreover, DFS-NS without DMNs did not deposit well inside the skin, indicating that DMNs played an important role in effectively delivering drugs inside the skin. Therefore, it is evident from the findings that loading DFS-NS into novel DMN devices can effectively deliver DFS transdermally.

Strong and Tough Supramolecular Microneedle Patches with Ultrafast Dissolution and Rapid-Onset Capabilities

Dissolving microneedle (DMN) patches are emerging as a minimally invasive and efficient transdermal drug delivery platform. Generally, noncrystalline, water-soluble, and high-molecular-weight polymers are employed in DMNs because their sufficient intermolecular interactions can endow the DMNs with necessary mechanical strength and toughness. However, high viscosity and heavy chain entanglement of polymer solutions greatly hinder processing and dissolution of polymeric DMNs. Here, a strong and tough supramolecular DMN patch made of highly water-soluble cyclodextrin (CD) derivatives is described. Due to the synergy of multiple supramolecular interactions, the CD DMN patch exhibits robust mechanical strength outperforming the state-of-the-art polymeric DMNs. The CD DMN displays ultrafast dissolution (<30 s) in skin models by virtue of the dynamic and weak noncovalent bonds, which also enables the CD DMN and its payloads to diffuse rapidly into the deep skin layer. Moreover, the unique supramolecular structure of CD allows the CD DMNs to load not only hydrophilic drugs (e.g., rhodamine B as a model) but also hydrophobic model drugs (e.g., ibuprofen). As a proof-of-concept, CD DMNs loading ibuprofen show a rapid onset of therapeutic action in a xylene-induced acute inflammation model in mice. This work opens a new avenue for the development of mechanically robust supramolecular DMNs and broadens the applications of supramolecular materials.

Chitosan-based microneedle arrays for dermal delivery of Centella Asiatica

Centella asiatica, a medicinal herb used for wound healing, has a limited effect when delivered as an ointment. Centella asiatica's active component asiatic acid (AA) increases extracellular matrix development and reduces inflammation but cannot penetrate the stratum corneum to access deeper skin layers. To bypass the stratum corneum, we formulated two types of AA-loaded microneedle arrays. We fabricated, characterised and optimised a dissolving array made from chitosan and PVA and a hydrogel array made from chitosan and PVP. Both needles were strong and long enough to pierce the epidermis without breaking. Both were biocompatible with keratinocytes and fibroblasts (>75% viability at 100% concentration) and showed a sustained drug release over 48 hours. The hydrogel microneedle released more AA (52.2%) than the dissolving formulation (26.4%); thus, we evaluated them in an excisional rat model. The hydrogel microneedle arrays significantly increased the rate of wound closure compared to the control. This research has shown that the chitosan-PVA hydrogel microneedles could penetrate the epidermis, effectively release AA, and increase the wound closure rate. This AA-loaded delivery system shows promise as a natural treatment for wound healing and may be applied to other bioactive compounds with similar physiochemical properties in the future.

Ciprofloxacin-loaded dissolving polymeric microneedles as a potential therapeutic for the treatment of S. aureus skin infections

Microneedles have been widely studied for many topical and transdermal therapeutics due to their ability to painlessly puncture the skin, thereby bypassing the stratum corneum, the main skin barrier. In this study, ciprofloxacin (CIP) was loaded into dissolving polymeric microneedles prepared by a two-layer centrifugation method as a potential treatment of skin infections such as cellulitis. The polymers used were polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP). Two formulations were investigated, namely CIP_MN1, composed of 10 mg ciprofloxacin incorporated into a polymer matrix of PVA and PVP with a weight ratio of (9:1), and CIP_MN2, composed of 10 mg ciprofloxacin incorporated into PVA polymer. CIP_MN1 and CIP_MN2 showed a mean microneedle height of 188 and 179 µm, respectively. Since Parafilm has been proven as a model to examine the perforation of microneedles in skin, it was used to evaluate the ability of microneedles to perforate the skin. CIP_MN1 showed almost complete perforation of Parafilm, 190 pores, compared to CIP_MN2 which created only 85 pores in Parafilm, and therefore CIP_MN1 was used for subsequent studies. Examining CIP_MN1 on agarose gel as an in vitro model of human skin showed that the formula was able to fully perforate the agarose gel. Moreover, this formula showed significantly greater antimicrobial activity (p < 0.0001) compared to a free gel of ciprofloxacin against Staphylococcus aureus in an agarose gel-based model. This was evidenced by a zone of inhibition of 29 mm for the microneedle formulation of ciprofloxacin (CIP_MN1) compared to 2 mm for the free gel of ciprofloxacin. Furthermore, the CIP_MN1 showed complete dissolution in human skin after 60 min from application. Finally, the skin deposition of CIP_MN1 was investigated in ex vivo excised human skin. CIP_MN1 showed significantly more deposition of ciprofloxacin in deeper skin layers compared to the free gel of ciprofloxacin, and the released ciprofloxacin from the microneedles tends to migrate to deeper layers with time. Collectively, these results suggest that CIP_MN1 can be a potential delivery system for the treatment of S. aureus skin infections.

A Novel Approach for Skin Regeneration by a Potent Bioactive Placental-Loaded Microneedle Patch: Comparative Study of Deer, Goat, and Porcine Placentas

The aims of this study were to investigate the skin regeneration potential of bioactive placenta (deer placenta (DP), goat placenta (GP), and porcine placenta (PP)) and fabricate bioactive extract-loaded dissolving microneedles (DMNs) as a dermal delivery approach. The placentas were water-extracted, and the active compounds were evaluated. Bioactivity studies were performed in dermal fibroblasts and keratinocytes. DMNs were fabricated to deliver the potent bioactive placenta extract into the skin. All placental extracts expressed high amounts of protein, growth factors (EGF, FGF, IGF-1 and TGF-β1), and amino acids. These extracts were not toxic to the skin cells, while the proliferation of fibroblast cells significantly increased in a time-dependent manner. GP extract that exhibited the maximum proliferation, migration, and regeneration effect on fibroblast cells was loaded into DMN patch. The suitable physical properties of DMNs led to increased skin permeation and deposition of bioactive macromolecules. Moreover, GP extract-loaded DMNs showed minimal invasiveness to the skin and were safe for application to human skin. In conclusion, placental extracts act as potent bioactive compounds for skin cells, and the highest bioactive potential of GP-loaded DMNs might be a novel approach to regenerate the skin.

A Rapid Corneal Healing Microneedle for Efficient Ocular Drug Delivery

Fungal keratitis (FK) remains a serious clinical problem worldwide, so the ultimate goal of the treatment is to develop a minimally invasive, safe, and effective method for ocular drug delivery. Here, a minimally invasive delivery system is reported for treating FK by using a dissolving microneedle (MN)-array patch based on Poly(D,L-lactide) (PLA) and hyaluronic acid (HA). By altering the concentration of PLA, MN patches with excellent properties are modified and optimized. The 30% PLA-HA MN patches penetrate the corneal epithelial layer reversibly with no apparent ocular irritation as well as a short recovery time of less than 12 h, and increase the residence time by 2.5 h in the conjunctival sac, thereby offering higher drug bioavailability. Remarkably, the rabbit model of FK shows that the topical MN(+) patch medication exerts superior therapeutic effects compared with the conventional eye drop formulation, and also presents comparable therapeutic efficacy with that of the clinical mainstay strategy (i.e., intrastromal injection). Therefore, the MN patch, acting as an ocular drug delivery system with high efficacy and ability of rapid corneal healing, promises a cost-effective household solution for the treatment of FK, which may also lead to a new approach for treating FK in clinics.

Microneedle-Mediated Biomimetic Cyclodextrin Metal Organic Frameworks for Active Targeting and Treatment of Hypertrophic Scars

Due to the lack of a delivery system that actively targets hypertrophic scar fibroblasts (HSFs), it is difficult to concentrate the effects of drugs on hypertrophic scars (HSs). We recently discovered that the HSF membrane has a homologous targeting effect and developed an active targeted drug delivery system for the local treatment of HSs. A diphenyl carbonate cross-linked cyclodextrin metal organic framework (CDF) containing more than 26% (w/w) quercetin (QUE) was coated with a HSF membrane (QUE@HSF/CDF) and then dispersed in Bletilla striata polysaccharide (BSP)-fabricated dissolvable microneedles (BSP-MNs-QUE@HSF/CDF) for local administration. This biomimetic nanodrug delivery system improved efficacy on HSs by regulating Wnt/β-catenin and JAK2/STAT3 pathways and reducing the expression of collagens I and III in HS, and this performance was superior to those of systems without HSF functionalization or the assistance of microneedles. Additionally, we found that BSP has synergistic effects and the microneedles have higher mechanical strength and better physical stability than microneedles made of hyaluronic acid. This currently designed drug delivery strategy integrating biomimetic nanoparticles and dissolvable microneedles is promising for applications in the fields of skin disease treatment and cosmetics.

A Facile Low-Dose Photosensitizer-Incorporated Dissolving Microneedles-Based Composite System for Eliciting Antitumor Immunity and the Abscopal Effect

Nanomedicine-based photodynamic therapy (PDT) for melanoma treatment has attracted great attention. However, the complex design of polymer nanoparticles and high doses of photosensitizers used in intravenous injections (for sufficient accumulation of drugs in tumor lesions) pose a huge challenge to the commercialization and further clinical application. Herein, we fabricated the carrier-free nanoassemblies of a chlorin e6 (L-Ce6 NAs)-integrated fast-dissolving microneedles patch (L-Ce6 MNs) enriching only about 3 μg of Ce6 in the needle tips via a facile fabrication method. The L-Ce6 MNs had sufficient mechanical strength to penetrate the skin and facilitated the transportation of L-Ce6 NAs to a depth of 200-500 μm under the skin, thereby achieving efficient and accurate drug delivery to tumor lesions. In a xenograft mouse melanoma model, the L-Ce6 MNs-based PDT with low dose of Ce6 (0.12 mg/kg) exerted efficient ablation of the primary lesions in situ through reactive oxygen species (ROS) generation. More importantly, a significant abscopal effect was also elicited by activating immunogenic cell death (ICD) and releasing danger-associated molecular patterns (DAMPs), which in turn promoted dendritic cells (DCs) maturation and the subsequent antigen presentation, thereby facilitating the T-cell-mediated immune response without synergetic immunotherapies. Collectively, our findings indicate the facile, controllable, and fast-dissolving microneedles patch with a low dose of photosensitizers presented great therapeutic potential for enhanced photoimmunotherapy.

Pharmacokinetic Evaluation of a Novel Donepezil-Loaded Dissolving Microneedle Patch in Rats

Research on the development of dissolving microneedles (DMNs) has focused on bolus drug delivery, with little attention on sustained release. Here, we evaluated the sustained release, absorption pattern, and effective drug permeation of a novel donepezil-loaded DMN patch through an in vivo investigation on rats. The applications of DMN patches to the shaved skin of rats for 1 week and 1 h were compared with oral donepezil administration to assess their sustained release capabilities. We used a validated liquid chromatography–tandem mass spectrometry method to quantify donepezil in the plasma. We found that the microneedle arrays effectively delivered donepezil across the skin, with dissolution observed within 1 h of application. Furthermore, skin irritation test showed that the patches produced no irritation response. The DMN arrays also effectively increased drug permeation and demonstrated sustained release and absorption of donepezil from DMN patches. These patches allow extended dosing intervals, reduced gastrointestinal adverse effects, and convenient self-administration to mitigate poor drug compliance, making them beneficial for the treatment of elderly patients with Alzheimer’s disease.

[Preparation of triptolide-loaded dissolving microneedles and its transdermal penetration]

Triptolide(TP), the main active and toxic component of Tripterygium wilfordii, has the limitations of low bioavailability, poor absorption, low concentration in plasma, and small lethal dose. Microneedle(MN), the hybrid of hypodermic needle and transdermal patch, is a physical penetration-enhancing system. Dissolving microneedles(DMNs) can be tailored to specific needs of degradation rate. In this study, the TP-loaded DMNs(DMNs-TP) were prepared with the two-step centrifugation method. The optimal ratio of PVA to PVP K30, water content in matrix solution, demoulding method, and plasticizer for preparing DMNs were investigated with the indexes of formability and mechanical strength. The drug loading capacity was determined by HPLC and morphological characteristics were observed under an optical microscope. The mechanical properties were investigated by H&amp;E staining and Franz diffusion cell was used to detect the in vitro skin permeation characteristics. Through the experiment, we confirmed that the optimal backing material should be PVA and PVP K30(3∶1) and the optimal ratio of matrix material to water should be 3∶4. The prepared DMNs-TP were pyramidal with smooth surface and length of approximately 550 μm. Each patch(2.75 cm~2) had the drug loading capacity of(153.41±2.29) μg, and TP was located in the upper part of the needle. The results of in vitro skin permeation assay demonstrated that the cumulative penetration of TP in DMNs-TP reached 80% in 24 h, while little TP solution penetrated the skin, which proved that DMNs promoted the transdermal delivery of TP.

Dissolving Polymer Microneedles for Transdermal Delivery of Insulin

It’s of great significance to develop insulin-loaded dissolving microneedles (MNs) which are fabricated with various methods and materials for transdermal delivery of insulin to effectively and efficiently treat diabetes. In this work, we present a kind of FITC-insulin tip-loaded dissolving MNs fabricated with the mixture of polyvinyl alcohol (PVA) and sucrose using homemade PDMS MNs mold under vacuum conditions. The uniform appearance of MN arrays contributes to controlling the drug dosage well as required. Sufficient mechanical strength for penetrating tough stratum corneum can be obtained by vacuum frozen-drying for at least 6 h after peeling MNs off the mold. About 90% of the FITC-insulin is localized in the conical MN tips and can be released into the skin within 2 min after insertion. The in vivo insulin absorption study and hypoglycemic effect in diabetic mice demonstrate that the proposed insulin-loaded MNs can efficiently deliver the insulin to the systemic circulation and exhibit a similar effect to hypodermic injection on hypoglycemic administration. Together these results suggested that the efficient MN fabrication process proposed in this work shows great potential for mass production and practical application of drug-loaded dissolving MNs in the future.

Dissolving Microneedles Developed in Association with Nanosystems: A Scoping Review on the Quality Parameters of These Emerging Systems for Drug or Protein Transdermal Delivery

The largest organ of the body provides the main challenge for the transdermal delivery of lipophilic or high molecular weight drugs. To cross the main barrier of the skin, the stratum corneum, many techniques have been developed and improved. In the last 20 years, the association of microneedles with nanostructured systems has gained prominence for its versatility and for enabling targeted drug delivery. Currently, the combination of these mechanisms is pointed to as an emerging technology; however, some gaps need to be answered to transcend the development of these devices from the laboratory scale to the pharmaceutical market. It is known that the lack of regulatory guidelines for quality control is a hindrance to market conquest. In this context, this study undertakes a scoping review of original papers concerning methods applied to evaluate both the quality and drug/protein delivery of dissolving and hydrogel-forming microneedles developed in association with nanostructured systems.

Fabrication and characterization of dissolving microneedles for transdermal drug delivery of allopurinol

Allopurinol (AP) is the first line drug in treating hyperuricemia and gout in clinical by oral drug delivery, which is associated with severe adverse effects and the hepatic first-pass effect. Herein, we first proposed AP encapsulated dissolving microneedles (DMNs) for transdermal drug delivery to realize the sustained drug release and avoid the hepatic first-pass effect, which will help to reduce the adverse effects and improve the bioavailability of AP. DMNs were fabricated by a suspension solution casting method with precisely controlled dose. They had sufficient mechanical strength to penetrate through the skin and resulted in the formation of hundreds of micropores in skin. The results of in vitro and ex vivo release experiments demonstrated that the release profile of DMNs was independent with the dose of AP, and they indeed had much higher drug delivery efficiency (DDE) than the equal amount of AP in solutions. In vivo DDE reached to 38.9% within 1 h, and the drug residual can be served as a drug reservoir for sustained drug release. The result of pharmacodynamic study further confirmed that the sustained release and the anti-hyperuricemia effect of DMNs encapsulating AP were achieved. Moreover, transepidermal water loss significantly increased to 49.50 ± 3.82 g/m²·h after the application of DMNs and returned to normal levels (12.25 ± 0.21 g/m²·h) after 8 h, indicating that the DMNs were well tolerated. These results suggest that transdermal drug delivery of AP by using DMNs is an efficient and safe alternative to currently available routes of administration.

Dissolving Candlelit Microneedle for Chronic Inflammatory Skin Diseases

Chronic inflammatory skin diseases (CISDs) negatively impact a large number of patients. Injection of triamcinolone acetonide (TA), an anti-inflammatory steroid drug, directly into the dermis of diseased skin using needle-syringe systems is a long-established procedure for treating recalcitrant lichenified lesions of CISDs, referred to as TA intralesional injection (TAILI). However, TAILI causes severe pain, causing patients to be stressed and reluctant to undergo treatment. Furthermore, the practitioner dependency on the amount and depth of the injected TA makes it difficult to predict the prognosis. Here, candle flame ("candlelit")-shaped TA-loaded dissolving microneedles (Candlelit-DMN) are designed and fabricated out of biocompatible and biodegradable molecules. Candlelit-DMN distributes TA evenly across human skin tissue. Conjoined with the applicator, Candlelit-DMN is efficiently inserted into human skin in a standardized manner, enabling TA to be delivered within the target layer. In an in vivo skin inflammation mouse model, Candlelit-DMN inserted with the applicator effectively alleviates inflammation by suppressing inflammatory cell infiltration and cytokine gene expression, to the same extent as TAILI. This Candlelit-DMN with the applicator arouses the interest of dermatologists, who prefer it to the current TAILI procedure.

A Perspective on Imiquimod Microneedles for Treating Warts

Warts are a common skin problem and are caused by infection with a virus. Warts are currently mainly treated by therapies involving ablating tissue or interrupting cellular division. However, all these existing treatments are either invasive or cause skin pain and tissue destruction. Imiquimod is a synthetic compound that belongs to the imidazoquinolinone family. It has been successfully used as a topical drug to treat external anogenital warts. However, topical imiquimod cream for warts is restricted by low skin permeability, and several side effects such as itching, pain, and erosions occur most frequently following topical treatment. Microneedle technology, a minimally invasive drug delivery system, has the potential to overcome the barrier of the stratum corneum. This technique would also offer a painless treatment choice and provide personalized therapies. In the study, we loaded imiquimod within dissolving microneedles using the molding method. Gelatin was used as a structural material for microneedle formation without adding a crosslinker. To our knowledge, this is the first study of using dissolving microneedles and exploring their utilization with imiquimod for the treatment of warts. First, we added fluorescent dye and trypan blue into the microneedles to evaluate the status of drugs in the microneedles and the degradation property of microneedles made of gelatin, respectively. Here we also prove the strength of the imiquimod microneedles and study their capability to penetrate the skin. The results show no apparent differences in mechanical failure after an additional imiquimod-loaded. Besides, we provide evidence that imiquimod microneedles induce secreted embryonic alkaline phosphatase (SEAP) in the RAW 264.7 macrophages. Gelatin does not affect the imiquimod in microneedles; a similar immune response was affected by the imiquimod alone or imiquimod complexed with gelatin. Our research demonstrates a proof of concept of using imiquimod microneedles for future warts treatment.

In Situ Self-Assembly Nanomicelle Microneedles for Enhanced Photoimmunotherapy via Autophagy Regulation Strategy

Although certain therapeutic agents with immunogenic properties may enhance antitumor immunity, cancer cells can eliminate harmful cytoplasmic entities and escape immunosurveillance by orchestrating autophagy. Here, an ingenious in situ self-assembled nanomicelle dissolving microneedle (DMN) patch was designed for intralesional delivery of immunogenic cell death-inducer (IR780) and autophagy inhibitor (chloroquine, CQ) coencapsulated micelles (C/I-Mil) for efficient antitumor therapy. Upon insertion into skin, the self-assembled C/I-Mil was generated, followed by electrostatic binding of hyaluronic acid, the matrix material of DMNs, accompanied by the dissolution of DMNs. Subsequently, photothermal-mediated size-tunable C/I-Mil could effectively penetrate into deep tumor tissue and be massively internalized via CD44 receptor-mediated endocytosis, precisely ablate tumors with the help of autophagy inhibition, and promote the release of damage-associated molecular patterns. Moreover, CQ could also act as an immune modulator to remodel tumor-associated macrophages toward the M1 phenotype via activating NF-κB. In vivo results showed that the localized photoimmunotherapy in synergy with autophagy inhibition could effectively eliminate primary and distant tumors, followed by a relapse-free survival of more than 40 days via remodeling the tumor immunosuppressive microenvironment. Our work provides a versatile, generalizable framework for employing self-assembled DMN-mediated autophagy inhibition integrated with photoimmunotherapy to sensitize superficial tumors and initiate optimal antitumor immunity.

Dissolving microneedles containing aminolevulinic acid improves protoporphyrin IX distribution

One important limitation of topical photodynamic therapy (PDT) is the limited tissue penetration of precursors. Microneedles (MNs) are minimally invasive devices used to promote intradermal drug delivery. Dissolving MNs contain drug-associated to polymer blends, dissolving after insertion into skin, allowing drug release. This study comprises development and characterization of a pyramidal model of dissolving MNs (500 μm) prepared with 5% wt/wt aminolevulinic acid and 20% wt/wt Gantrez AN-139 in aqueous blend. Protoporphyrin IX formation and distribution were evaluated in tumor mice model by using fluorescence widefield imaging, spectroscopy, and confocal microscopy. MNs demonstrated excellent mechanical resistance penetrating about 250 μm with minor size alteration in vitro, and fluorescence intensity was 5-times higher at 0.5 mm on average compared to cream in vivo (being 10 ± 5 a.u. for MNs and 2.4 ± 0.8 a.u. for cream). Dissolving MNs have overcome topical cream application, being extremely promising especially for thicker skin lesions treatment using PDT.

Poly(d,l-lactide-co-glycolide) (PLGA) Nanoparticles Loaded with Proteolipid Protein (PLP)-Exploring a New Administration Route

The administration of specific antigens is being explored as a mean to re-establish immunological tolerance, namely in the context of multiple sclerosis (MS). PLP139-151 is a peptide of the myelin's most abundant protein, proteolipid protein (PLP), which has been identified as a potent tolerogenic molecule in MS. This work explored the encapsulation of the peptide into poly(lactide-co-glycolide) nanoparticles and its subsequent incorporation into polymeric microneedle patches to achieve efficient delivery of the nanoparticles and the peptide into the skin, a highly immune-active organ. Different poly(d,l-lactide-co-glycolide) (PLGA) formulations were tested and found to be stable and to sustain a freeze-drying process. The presence of trehalose in the nanoparticle suspension limited the increase in nanoparticle size after freeze-drying. It was shown that rhodamine can be loaded in PLGA nanoparticles and these into poly(vinyl alcohol)-poly(vinyl pyrrolidone) microneedles, yielding fluorescently labelled structures. The incorporation of PLP into the PLGA nanoparticles resulted in nanoparticles in a size range of 200 µm and an encapsulation efficiency above 20%. The release of PLP from the nanoparticles occurred in the first hours after incubation in physiological media. When loading the nanoparticles into microneedle patches, structures were obtained with 550 µm height and 180 µm diameter. The release of PLP was detected in PLP-PLGA.H20 nanoparticles when in physiological media. Overall, the results show that this strategy can be explored to integrate a new antigen-specific therapy in the context of multiple sclerosis, providing minimally invasive administration of PLP-loaded nanoparticles into the skin.

Polyvinylpyrrolidone microneedles for localized delivery of sinomenine hydrochloride: preparation, release behavior of in vitro & in vivo, and penetration mechanism

Sinomenine (SIN) is an anti-inflammatory alkaloid derived from Sinomenium acutum, and the products sinomenine hydrochloride (SH) tablets and injections have been marketed in China to treat rheumatoid arthritis (RA). Oral administration of SH has shortcomings of gastrointestinal irritation and low bioavailability. The injection may require professional training and higher cost. It is of interest to develop an alternative form that is easier to administer and avoids the first-pass metabolism. In this study, SH-loaded dissolving microneedles (SH-MN) were fabricated using polyvinyl pyrrolidone and chondroitin sulfate with a casting method. In percutaneous permeation studies of In vitro, the cumulative permeation and permeation rate of SH-MN were 5.31 and 5.06 times higher than that of SH-gel (SH-G). In percutaneous pharmacokinetic studies, the values of the area under the curve after administration of SH-MN in the skin and blood were 1.43- and 1.63-fold higher than that of SH-G, respectively. In percutaneous absorption studies, SH-MN could absorb into tissue fluid; and dissolve after skin penetration. The drug was released along the channel and spread to surrounding skin tissue. After 4 h, the needle tip was almost completely dissolved, and the drug could penetrate to a depth of 200 μm under the skin. These results demonstrate that the SH-MN is an effective, safe, and simple strategy for transdermal SH delivery.

Dissolving Microneedles with Spatiotemporally controlled pulsatile release Nanosystem for Synergistic Chemo-photothermal Therapy of Melanoma

High aggressiveness and recurrence of melanoma tumors require multiple systemic drug administrations, causing discomfort and severe side effects to the patients. Topical treatment strategies that provide repetitively controllable and precise drug administrations will greatly improve treatment effects.

Methods: In this study, a spatiotemporally controlled pulsatile release system, which combined dissolving microneedles (DMNs) and thermal-sensitive solid lipid nanoparticles (SLNs), was constructed to realize multiple doses of dual-modal chemo-photothermal therapy in a single administration. Paclitaxel (PTX) and photothermal agent IR-780 were encapsulated into SLNs and were concentrated in the tips of DMNs (PTX/IR-780 SLNs @DMNs). Equipped with several needles, the DMN patch could be directly inserted into the tumor site and provide a stable “Zone accumulation” to constrain the PTX/IR-780 SLNs at the tumor site with uniform distribution.

Results:In vitro experiments showed that after irradiation with near-infrared light, the PTX/IR-780 SLNs gradually underwent phase transition, thereby accelerating the release of PTX. When irradiation was switched off, the PTX/IR-780 SLNs cooled to re-solidify with limited drug release. Compared with intravenous and intratumoral injections, very few SLNs from PTX/IR-780 SLNs @DMNs were distributed into other organs, resulting in enhanced bioavailability at the tumor site and good safety. In vivo analysis revealed that PTX/IR-780 SLNs @DMNs exhibited significant anti-tumor efficacy. In particular, the primary tumor was completely eradicated with a curable rate of 100% in 30 days and the highest survival rate of 66.67% after 100 days of treatment.

Conclusion: Herein, we developed a DMN system with a unique spatiotemporally controlled pulsatile release feature that provides a user-friendly and low-toxicity treatment route for patients who need long-term and repeat treatments.

Dissolving Microneedles for Rapid and Painless Local Anesthesia

Microneedles are emerging drug delivery methods for painless treatment. The current study tested dissolving microneedles containing lidocaine (Li-DMN) for use in local anesthesia. An Li-DMN patch was fabricated by centrifugal lithography with carboxymethyl cellulose as a structural polymer and assessed for physical properties by optical microscopy and a fracture force analyzer. The biocompatibility was evaluated by a histology section in vitro and by ear thickness in vivo. The efficacy of the Li-DMN patch was assessed by electrophysiological recordings in primary cultured sensory neurons in vitro and a von Frey test on rats’ hind paws in vivo. The physical properties of the microneedle showed enough rigidity for transdermal penetration. The maximal capacity of lidocaine-HCl in the Li-DMN patch was 331.20 ± 6.30 µg. The cytotoxicity of the dissolving microneedle to neuronal cells was negligible under an effective dose of lidocaine for 18 h. Electrophysiological recordings verified the inhibitory effect of the voltage-gated sodium channel current by the Li-DMN patch in vitro. A skin reaction to the edema test and histologic analysis of the rats’ ears after application of the Li-DMN patch were negligible. Also, the application of the Li-DMN patch reduced the nocifensive behavior of the rats almost immediately. In conclusion, the dissolving microneedle patch with carboxymethyl cellulose is a promising candidate method for the painless delivery of lidocaine-HCl.

HPMC/PVP Dissolving Microneedles: a Promising Delivery Platform to Promote Trans-Epidermal Delivery of Alpha-Arbutin for Skin Lightening

Alpha-arbutin is one of the most efficient skin lightener agents, which shows the effect on reducing the pigmentation by competitively inhibiting human tyrosinase. However, alpha-arbutin has difficulty in skin permeability due to its hydrophilic property. The objective of this study was, therefore, to develop alpha-arbutin-loaded dissolving microneedles (DMNs) for improving the delivery of alpha-arbutin into the skin. The DMN patch was prepared using Gantrez™ S-97, hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone K-90 (PVP), chitosan, and their combinations. The optimal 8% alpha-arbutin-loaded DMNs, aside from Gantrez™ S-97, was successfully formulated with combination of 8% w/w HPMC and 40% w/w PVP K-90 (HPMC/PVP) at the weight ratio of 1:1. Both DMNs had 100% of penetration into porcine skin. Over 12 h of skin permeation, the flux of Gantrez™ S-97 DMNs and the HPMC/PVP DMNs were 66.21 μg/cm²/h and 74.24 μg/cm²/h, respectively. The accumulation amount of alpha-arbutin in the skin from Gantrez™ S-97 DMNs and HPMC/PVP DMNs was 107.76 μg and 312.23 μg, respectively. In comparison to the gel formulations, Gantrez™ S-97 DMNs and HPMC/PVP DMNs increase the delivery of alpha-arbutin across the skin approximately 2 and 4.7 times, respectively. In vivo studies found that alpha-arbutin-loaded HPMC/PVP DMNs delivered more alpha-arbutin into the skin than commercial cream. Moreover, the skin can reseal naturally after removal of DMNs patch without any signs of infection and remain stable in accelerated conditions for 4 weeks. Accordingly, alpha-arbutin-loaded HPMC/PVP DMNs could be a promising delivery platform for promoting trans-epidermal delivery of alpha-arbutin for skin lightening.

5-Aminolevulinic Acid-Loaded Hyaluronic Acid Dissolving Microneedles for Effective Photodynamic Therapy of Superficial Tumors with Enhanced Long-Term Stability

5-Aminolevulinic acid (5-ALA) is one of the most widely used prodrug in clinical photodynamic therapy of dermatological diseases and cancers; yet, its clinical application is still limited by the shallow skin penetration and unsatisfied stability in any existed formulations. Here, 5-ALA-loaded hyaluronic acid dissolving microneedles (5-ALA@HAMNs) are prepared for photodynamic therapy of superficial tumors. The HAMNs can not only assist the loaded 5-ALA to effectively penetrate the stratum corneum but also provide 5-ALA with an acidic and oxygen-free environment to reduce the dimerization of 5-ALA molecules via Schiff-base bonds and formation of inactive pyrazine derivatives, thus maintaining its chemical structure and biological activity. The chemical stability of 5-ALA in HAMNs is confirmed by UV-vis spectra and mass spectra measurements. The 5-ALA@HAMNs display remarkable tumor elimination both in vitro and in vivo, even after storage at room temperature for nine months, making it a highly potential device for effective delivery of 5-ALA in cancer photodynamic therapy.

Nanosuspension-Based Dissolving Microneedle Arrays for Intradermal Delivery of Curcumin

The objective of this study was to evaluate the intradermal delivery of curcumin utilising poly(vinylalcohol) (PVA)-based microneedles loaded with curcumin nanosuspension (CU-NS). Nanoprecipitation was used to formulate the CU-NS which was then incorporated into PVA microneedles arrays consisting of 11 × 11 microneedles of conical shape, measuring 900 µm in height and with 300 µm base diameter. The nanosuspension particle size was 520 ± 40 nm, with a polydispersity of 0.27 ± 0.02 using sodium lauryl sulfate (SLS) as a stabiliser. In vitro dissolution studies in 10% w/v Tween 80 showed that the CU-NS dissolved significantly faster than unmodified curcumin powder, with 34% released from the CU-NS, compared to 16% from the curcumin powder after 48 h. The CU-NS-loaded microneedles (CU-MN) were able to withstand a compression force of 32 N for 30 s. Moreover, these microneedles were able to penetrate excised neonatal porcine skin to a depth of 500 µm, dissolved completely in the skin within 60 min. After CU-MN dissolution, the drug diffused from the application site and migrated through the skin layers down to 2300 µm, significantly more than observed with topical application of CU-NS. This suggest that the fabricated microneedles with the incorporated CU-NS could enhance the intradermal delivery of curcumin.

Combinatorial application of dissolving microneedle patch and cream for improvement of skin wrinkles, dermal density, elasticity, and hydration

BACKGROUND

Dissolving microneedles (DMNs), microscale needles with a biodegradable polymer matrix, have been widely investigated for transdermal drug delivery. However, the restricted drug loading space of DMNs limited the delivery of the desired quantity of active compounds. In this study, we developed novel combinatorial therapies involving sequential application of adenosine-loaded DMN (Ad-DMN) patches and a topical adenosine-loaded cream (Ad-cream). The application of DMNs created skin channels, which delivered encapsulated drugs from both the DMNs and cream. The use of combinatorial therapies can maximize drug delivery.

METHODS

To compare the efficacy of combinatorial therapies and Ad-cream application, a double-blind clinical test was conducted over 10 weeks on 21 females with wrinkles around their eyes, and the skin parameters such as wrinkles, dermal density, elasticity, and hydration were analyzed. The skin irritation test was assessed by expert interviewers to elucidate undesirable side effects.

RESULTS

The combinatorial therapies showed statistically significant efficacy for the improvement of average depth of wrinkles, dermal density, elasticity, and hydration after an 8-week application (P < 0.001). Adverse effects on the skin were not observed in any subject during the test period.

CONCLUSION

The efficacy and safety results showed that the combinatorial therapies were a safe and outstanding innovation for the optimization of transdermal therapy.

Novel nanosuspension-based dissolving microneedle arrays for transdermal delivery of a hydrophobic drug

A nanosuspension (NS) was formulated from the lipophilic molecule cholecalciferol (CL) for enhanced transdermal delivery by embedding this NS into hydrophilic polymer-based dissolving microneedles (DMNs). First, the NS was prepared by sonoprecpitation with different molecular weights of poly (vinyl alcohol) and poly (vinyl pyrrolidone) as stabilizers and using two different solvents for particle size and zeta potential optimization. DMN arrays were then prepared by centrifugation-assisted micromoulding and subsequently dried. Poly (vinyl alcohol) (10 kDa) produced a NS with the lowest particle size ( ~ 300 nm). These particles yielded DMN with good mechanical properties when combined with aqueous blends of high molecular weight poly (vinyl pyrrolidone) (360 kDa). The particle size remained similar before and after MN preparation, as confirmed by scanning electron microscope. The CL was in the amorphous state in the free particles as well as in the DMN and, hence, no characteristic CL peak was observed in differential scanning calorimetry or X-ray diffraction. DMN arrays were found to be strong enough to bear a 32 N force, showed efficient skin insertion, and penetrated down to the third layer (depth ≈ 375 μm) of the validated skin model Parafilm M®. An ex vivo porcine skin permeation study using Franz diffusion cells compared the permeation of CL from CL-NS-loaded DMN arrays and MN-free CL-NS patches. It was observed that CL-NS-loaded DMN arrays showed significantly higher (498.19 μg ± 89.3 μg) ex vivo skin permeation compared with MN-free CL-NS patches (73.2 μg ± 26.5 μg) over 24 h. This is the first time a NS of a hydrophobic drug has been successfully incorporated into dissolving MN and suggest that NS-containing DMN systems could be a promising strategy for transdermal delivery of hydrophobic drugs.

Comparative Study of Two Droplet-Based Dissolving Microneedle Fabrication Methods for Skin Vaccination

Dissolving microneedles (DMNs) have been widely studied in medical applications due to their pain-free administration, superior efficiency, and safe drug delivery. In skin vaccination, preserving the activity of the encapsulated antigen is an important consideration, as antigen activity is lost during DMN fabrication because of various stress factors. These stress factors vary between fabrication methods and each method affects the antigen's activity to different degrees. In this study, the activity of encapsulated antigens delivered by DMNs is compared between two recently developed DMN fabrication methods; droplet-born air blowing (DAB) and centrifugal lithography (CL) for a model scrub typhus vaccine antigen, ScaA. Although the in vitro analysis of ScaA-loaded DMNs (ScaA-DMNs) does not show any differences in physical properties depending on the fabrication methods, the immunogenicity of the CL-produced ScaA-DMN is significantly higher based on cytokine measurement and humoral immunity. DAB and CL differ in their solidification conditions, suggesting that solidification factors critically affect the encapsulated antigen's activity. ScaA-DMNs may also be stably stored for 4 weeks at room temperature. In conclusion, CL is a superior DMN fabrication method compared with DAB, and this study proves that DMN is feasible and practical for skin vaccination.

Au Nanocage-Strengthened Dissolving Microneedles for Chemo-Photothermal Combined Therapy of Superficial Skin Tumors

For superficial skin tumors (SST) with high incidence, surgery and systemic therapy are relatively invasive and possible to cause severe side effect, respectively. Yet, topical therapy is confronted with the limited transdermal capacity because of the stratum corneum barrier layer of skin. Therefore, it is crucial to develop a highly effective and minimally invasive alternative transdermal approach for treating SST. Here, we developed gold nanocage (AuNC)- and chemotherapeutic drug doxorubicin (DOX)-loaded hyaluronic acid dissolving microneedle (MN) arrays. The loaded AuNCs are not only reinforcers to enhance the mechanical strength of the MNs, but also effective agents for photothermal therapy to obtain effective transdermal therapy for SST. The resultant MNs can effectively penetrate the skin, dissolve in the skin and release cargoes within the tumor site. Photothermal effect of AuNCs initiated by near-infrared laser irradiation combined with the chemotherapy effect of DOX destroyed tumors synergistically. Moreover, we verified the potent antitumor effects of the DOX/AuNC-loaded MNs after four administrations to SST-bearing mice without obvious side effects. Therefore, the drug/AuNC-loaded dissolving MN system provides a promising platform for effective, safe, minimally invasive combined treatment of SST.

Microneedle Patches as Drug and Vaccine Delivery Platform

BACKGROUND

Transcutaneous delivery is the ideal method for delivering therapeutic reagents or vaccines into skin. With their promise of self-administration, cost-effective and high efficiency, microneedle patches have been studied intensively as therapeutic and vaccination delivery platform that replaces injection by syringe. This review aims to summarize the recent advancements of microneedle patches in application for drugs and vaccine delivery.

METHODS

We reviewed the most of recently published papers on microneedle patches, summarized their evolution, classification, state-of the-art capabilities and discussed promising application in drugs and vaccine delivery.

RESULTS

With the rapid development of nanotechnology, microneedle patches have been improved by switching from undissolving to dissolving microneedles, and their safety has also improved dramatically. As a drug delivery tool, microneedle patches can deliver bioactive molecular of different physical size. Additionally, microneedle patches can be coated or encapsulate with DNA vaccine, subunit antigen, inactivated or live virus vaccine. Combining clinical results with the results of patient interview, microneedle patches are found to be feasible and are predicated to soon be acceptable for the medical service.

CONCLUSION

In this review, we summarized the evolution, current and future application of microneedle patches as delivery vehicle for drugs and vaccines. Compared with traditional delivery tools, microneedle patches have many advantages, such as providing pain-free, non-invasive, convenient route for reagent administration and delivery, with no cold chain required for storage and transportation as well as decreasing sharp medical waste, needle-caused injury and transmission of blood-borne infectious disease in rural area. However, even though there are dramatic progress in preclinical investigation of microneedle patches, further testing will be required for clinical application. Further research should be implemented in multiple fields, such as vaccinology, immunology, and materials science, to improve this delivery platform. Because of their advantages in dose sparing, safety and treatment compliance, microneedle patches are expected to be widely applied in clinical treatment and vaccine administration in near future.