Spiderweb-Shaped Iron-Coordinated Polymeric Network as the Novel Coating on Microneedles for Transdermal Drug Delivery Against Infectious Wounds.

Coated microneedles (CMNs) are a minimally invasive platform for immediate-release transdermal drug delivery. However, the practical applications of CMNs have been significantly hindered by the challenges associated with complex formulations, single function, and limited drug loading capacity. This study has developed a spiderweb-shaped iron-coordinated polymeric nanowire network (Fe-IDA NWs). The resulting Fe-IDA NWs are endowed with a certain viscosity due to the synergy of multiple supramolecular interactions. This allows them to replace traditional polymeric thickeners as microneedle coatings. The Fe-IDA NWs-coated microneedles (Fe-IDA MNs) display rapid disintegration in the skin model, which also enables the swift diffusion of Fe-IDA NWs and their payloads into the deeper skin layers. Additionally, Fe-IDA MNs exhibit desirable enzymatic activity and potential antibacterial ability. Thus, Fe-IDA MNs can enhance the therapeutic efficacy against wound infection through synergistic effects, and avoid the overly complicated formulation and the release of nontherapeutic molecules of conventional CMNs. As a proof-of-concept, Fe-IDA MNs loaded with chlorin e6 showed a synergistic chemodynamic-photodynamic antibacterial effect in a methicillin-resistant Staphylococcus aureus-infected wound model in mice. Collectively, this work has significant implications for the future of CMNs-based transdermal drug delivery systems and expands the application fields of metal coordination polymer (MCP) materials.

Effect of microneedles shape on skin penetration and transdermal drug administration.

Microneedle (MN) patches are highly efficient and versatile tools for transdermal drug administration, in particular for pain-free, self-medication and rapid local applications. Diffraction ultraviolet (UV) light lithography offers an advanced method in fabricating poly(ethylene glycol)-based MNs with different shapes, by changing both the UV-light exposure time and photomask design. The exposure time interval is limited at obtaining conical structures with aspect ratio < 1:3, otherwise MNs exhibit reduced fracture load and poor indentation ability, not suitable for practical application. Therefore, this work is focused on a systematic analysis of the MN's base shapes effects on the structural characteristics, skin penetration and drug delivery. Analyzing four different base shapes (circle, triangle, square and star), it has been found that the number of vertices in the polygon base heavily affects these properties. The star-like MNs reveal the most efficient skin penetration ability (equal to 40 % of -their length), due to the edges action on the skin during the perforation. Furthermore, the quantification of the drug delivered by the MNs through ex-vivo porcine skin shows that the amounts of small molecules released over 24 h by star-like MNs coated by local anesthetic (Lidocaine) and an anti-inflammatory (Diclofenac epolamine) drugs are 1.5× and 2× higher than the circular-MNs, respectively.

The Relationship between the Drug Delivery Properties of a Formulation of Teriparatide Microneedles and the Pharmacokinetic Evaluation of Teriparatide Administration in Rats.

PURPOSE: Teriparatide is an effective drug for the treatment of osteoporosis. This study examines the relationship between the drug delivery properties of the solid formulation with teriparatide and the pharmacokinetic properties of teriparatide in vivo. METHODS: Teriparatide microneedles with different dissolution rates were prepared using sucrose and carboxymethylcellulose (CMC). There were three aspects of this study: (1) The dissolution rate of teriparatide from both formulations (sucrose and CMC) was measured in vitro. (2) After administration into porcine skin ex vivo, the diffusion rate of FITC-dextran was observed using a confocal microscope. (3) Pharmacokinetic studies were performed in rats and pharmacokinetic data compared with the release rate and the diffusion pattern. RESULTS: In the in vitro dissolution experiment, 80% of teriparatide was released within 30 min from the CMC MNs, whereas 80% of teriparatide was released within 10 min from the sucrose MNs. After 30 min, the fluorescence intensity on the surface of the MNs was 40% of the initial intensity for sucrose MNs and 90% for CMC MNs. In the pharmacokinetic study, the Cmax values of the CMC and sucrose MNs were 868 pg/mL and 6809 pg/mL, respectively, and the AUClast values were 6771 pg*hr/mL for the CMC MNs and 17,171 pg*hr/mL for the sucrose MNs. CONCLUSIONS: When teriparatide is delivered into the skin using microneedles, the release rate from the solid formulation determines the drug's pharmacokinetic properties. The diffusion pattern of fluorescence into the skin can be used to anticipate the pharmacokinetic properties of the drug.

Targeted allergen-specific immunotherapy within the skin improves allergen delivery to induce desensitization to peanut.

Aim: Epicutaneous immunotherapy (EPIT) with peanut has been demonstrated to be safe but efficacy may be limited by allergen uptake through the skin barrier. To enhance allergen uptake into the skin, the authors used peanut-coated microneedles and compared them with EPIT in a peanut allergy mouse model. Methods: Sensitized mice were treated with peanut-coated microneedles or peanut-EPIT and then challenged with peanut to determine protection. Results: Treatment with peanut-coated microneedles was safe and showed enhanced desensitization to peanut compared with peanut-EPIT administered via a similar schedule. Protection was associated with reduced Th2 immune responses and mast cell accumulation in the intestine. Conclusion: Peanut-coated microneedles have the potential to present a safe method of improving allergen delivery for cutaneous immunotherapy.

Epicutaneous immunotherapy (EPIT) with peanut has been demonstrated to be safe but efficacy has been varied. The tight barrier provided by the skin may limit the amount of allergen taken up through the skin and thus reduce efficacy. The authors evaluated a microneedle-based approach to improve the amount of allergen deposited into the skin to improve efficacy. Mice were made allergic to peanut and then treated with peanut-coated microneedles or peanut-EPIT. Mice were challenged with peanut to determine suppression of allergic reactivity. In mice, treatment with peanut-coated microneedles was safe and enhanced desensitization to peanut compared with peanut-EPIT administered via a similar schedule. Peanut-coated microneedles may present a novel method of improving allergen immunotherapy delivered through the skin.

A novel method for fabrication of coated microneedles with homogeneous and controllable drug dosage for transdermal drug delivery.

Over the years, scientists have been focused on the development of microneedle coating process to coat a broad range of therapeutic agents onto the surface of the solid microneedles for effective drug delivery. The precise dose control, content uniformity as well as large-scale production of coated microneedles are still the core issues that have been the interest of researchers in this topic. To this end, a repeatable method that involved a micro-molding process was demonstrated for mass fabrication of coated microneedles with homogeneous and controllable drug loading under mild conditions. In this system, the dissolvable drug carriers with precise dosage were first mounted onto the solid microneedles and then exposed to the high moisture condition to finally obtain the coated microneedle with uniform and precise drug loading. Using the microneedle molds with the volume of 4.71 nL, 8.24 nL, 10.47 nL, and 12.56 nL per cavity, the drug loadings were precisely controlled at 4.8 ng, 6.4 ng, 9.3 ng, and 13.5 ng per needle, with the standard deviation of 0.09, 0.01, 0.07, and 0.53%, respectively. Mechanical property tests showed that the coated microneedles are strong enough for reliable skin insertion, and with in vivo trials in diabetic mice, we further confirmed the similar hypoglycaemic effect of insulin-coated microneedles to subcutaneous injection. Taken together, the micro-molding-based fabrication process has practical merits in the mass production of coated microneedles with homogeneous and controllable drug loading, facilitating the clinical translation of the microneedle technique.

Development of Polylactic Acid and Bovine Serum Albumin-layered-coated Chitosan Microneedles Using Novel Bees Wax Mould

Objectives: This work illustrates a novel method of fabrication of polymeric microneedle (MN) construct using bees wax as mould and development of coated polymeric MNs for drug delivery. Materials and Methods: A novel method of MN fabrication using bees wax as mould was established. The porous chitosan MN arrays were fabricated and coated with polylactic acid (PLA). The optimized MN arrays were coated with bovine serum albumin (BSA). The MNs were subjected to physiochemical and tensile strength characterization, followed by drug release study. The skin penetration and irritation study were performed in vivo in Wistar Albino rats. Results: The constructed MN arrays contain MNs with 0.9 mm length, 600 µm width at the base, 30-60 µm diameter at the tip, and 1.5 mm distance between 2 needles. These MNs patch was having good mechanical strength (0.72 N/needle) and tensile strength 15.23 Mpa. The MN array patch had 6.26% swelling index and 98.5% drug release was observed on the 50th hr. Good penetration and no skin irritation was observed for optimized MN batch. Conclusion: Polymeric MN arrays were successfully developed using bees wax mould and were successfully coated with PLA to deliver the BSA through skin epidermis layer.

Smart Microneedles with Porous Polymer Layer for Glucose-Responsive Insulin Delivery.

A closed-loop system imitating the function of pancreatic cells, connected to microneedles (MNs) that automatically "release" insulin in response to the blood glucose (BG) levels would be highly satisfactory for improving the quality of life and health for diabetes patients. This paper describes an easy, fast and simple technique of coating a porous polymer layer on stainless steel (SS) MNs that release insulin in a glucose-responsive fashion. It was fabricated by sealing insulin, sodium bicarbonate (a pH-sensitive element [NaHCOз]) and glucose oxidase (glucose-specific enzymes [GOx]) into the pores of a porous polymer coating. Glucose can passively diffuse into the pores and become oxidized to gluconic acid by GOx, thereby causing a decrease in local pH. The subsequent reaction of protons with NaHCOз forms carbon dioxide (CO2) which creates pressure inside the pores, thereby rupturing the thin polymer film and releasing the encapsulated insulin. Field emission scanning electron microscopy (FE-SEM) images displayed that upon the exposure of MNs to glucose-free phosphate buffer saline (PBS) with pH 7.4, the pores of the porous MNs were closed, while in MNs exposed to a hyperglycemic glucose level, the pores were opened and the thin film burst. These MNs demonstrated both in vitro (in porcine skin and PBS) and in vivo (in diabetic rats) glucose-mediated insulin release under hyperglycemic conditions with rapid responsiveness. This study validated that the release of insulin from porous MNs was effectively correlated with glucose concentration.

Safe Coated Microneedles with Reduced Puncture Occurrence after Administration.

The goal of this study is the preparation of safer coated microneedles so that tips remaining after the initial use are less likely to be reinserted on a second use. Twelve groups of uncoated microneedles (u-MNs) were prepared from the combination of three different aspect ratios (height to base width) and four kinds of polymer (polyethylene (PE), polypropylene (PP), nylon and polylactic acid (PLA)). After coating the u-MNs with polyvinyl alcohol formulation to make coated MNs (c-MNs), the force displacement of the u-MNs and the c-MNs was measured. The aspect ratio was reduced from 2.2, 2.5 and 3.0 with u-MNs to 1.3, 1.4 and 1.6 with c-MNs, respectively, after the coating formulation was applied to the MNs. All PLA MNs had a puncture performance of more than 95%. However, the puncture performance of u-MNs made of PE and of PP with a 3.0 aspect ratio was only 8% and 53%, respectively, whereas the rates of c-MNs made of PE and of PP were 82% and 95%, respectively. In animal experiments with PP MNs with a 3.0 aspect ratio, the 59% rate of puncture performance with u-MNs increased to above 96% with c-MNs and fell to 13% for r-MNs. Safe c-MNs can overcome the disadvantages of standard c-MNs by reducing the probable contamination of remaining tips after use. Safe c-MNs have advantages over standard c-MNs in terms of humidity resistance, reasonable cost, sterilization process and short processing time through the separate process of u-MN preparation and simple dip-coating.

Applications of microneedles in delivering drugs for various ocular diseases.

Treatment of majority of eye diseases involve the use of eye drops or eye ointments, which have major drawbacks of needing frequent administration, lower bioavailability and inability to cross the various eye barriers. This necessitates the use of novel delivery systems. Microneedles (MNs) as an alternate novel delivery system facilitate drug delivery to various ocular diseases with promising approaches in healthcare. Advances in pharmaceutical technology have made MNs provide localized, effective, less invasive and targeted drug delivery in the eye. The purpose of this review is to provide an insight to efficacious therapeutic applications the MNs can bring in various ocular diseases. Out of which, glaucoma, age-related macular degeneration, uveitis, retinal vascular occlusion and retinitis pigmentosa are majorly discussed. Among the various types of MNs; solid coated, hollow and dissolving polymeric MNs are specifically focused for their applications in ocular diseases. In addition, MNs shows improvement in the visual acuity and decreases the progression of the different ocular diseases.

Microneedles coated with peanut allergen enable desensitization of peanut sensitized mice.

The prevalence of peanut allergies has escalated over the last 20 years, yet there are no FDA approved treatments for peanut allergies. In this study we evaluated the potential of microneedles to deliver peanut protein extract (PE) into skin and assessed if the ensuing immune responses could desensitize mice that were sensitized to peanuts. Peanut sensitized mice were either treated through cutaneous immunotherapy using PE-coated microneedles or not treated, and then orally challenged with PE. After oral challenge, the clinical symptoms of peanut-induced anaphylaxis were significantly lower in the microneedle treated mice as compared to untreated mice, and this was accompanied by down-regulation of systemic anaphylaxis mediators such as histamine and mast cell protease-1 (MCPT-1) in the microneedles treated group. Overall, there was an up-regulation of Th1 cytokines (IL-2 and IFN-γ) as compared to Th2 cytokines (IL-4 and IL-5) in splenocyte culture supernatants of the microneedle treated group as compared to untreated group, suggesting that microneedles promoted immune modulation towards the Th1 pathway. Furthermore, mice treated with PE-coated microneedles were observed to retain integrity of their small intestine villi and had reduced eosinophilic infiltration as compared to the untreated but peanut sensitized mice, which further confirmed the desensitization capability of peanut cutaneous immunotherapy using coated microneedles. Thus, our current study represents a novel minimally invasive microneedle based cutaneous immunotherapy, which may provide a novel route of desensitization for the treatment of peanut allergies.

Coated microneedles mediated intradermal delivery of octaarginine/BRAF siRNA nanocomplexes for anti-melanoma treatment.

BRAF is the most frequently mutated gene in skin melanoma. Applying BRAF siRNA (siBraf) to silencing BRAF gene is a current frontline therapy for melanoma. However, delivery of macromolecular siRNA into the tumor site and introduction of siRNA into the tumor cells remain as challenges. In this study, we for the first time developed a siBraf delivery system based on cell penetrating peptide octaarginine (R8) nanocomplexes combined with coated microneedles (MNs), i.e. R8/siBraf coated MNs, for targeted anti-melanoma treatment. The R8/siBraf nanocomplexes were optimized based on the internalization of siBraf by A375 cells. In vitro A375 cell experiments presented that R8/siBraf can enhance siBraf transfection, silence BRAF gene, and inhibit tumor cells growth, comparable to polyethylenimine (PEI)/siBraf. R8/siBraf coated MNs can effectively deliver R8/siBraf into the disease site. In vivo anti-melanoma experiments indicated that R8/siBraf coated MNs can significantly inhibit the melanoma development, induce the tumor cells apoptosis, and suppress their proliferation. The BRAF gene in tumor were also significantly silenced in vivo. SiBraf intradermal delivery via combining MNs and R8 nanocomplexes is a promising approach for skin melanoma treatment, which exploited both virtues of MNs and cell penetrating peptide to obtain the targeting inhibition efficacy on skin melanoma.

Coated and Hollow Microneedle-Mediated Intradermal Immunization in Mice with Diphtheria Toxoid Loaded Mesoporous Silica Nanoparticles.

PURPOSE: To examine the immunogenicity of diphtheria toxoid (DT) loaded mesoporous silica nanoparticles (MSNs) after coated and hollow microneedle-mediated intradermal immunization in mice. METHODS: DT was loaded into MSNs and the nanoparticle surface was coated with a lipid bilayer (LB-MSN-DT). To prepare coated microneedles, alternating layers of negatively charged LB-MSN-DT and positively charged N-trimethyl chitosan (TMC) were coated onto pH-sensitive microneedle arrays via a layer-by-layer approach. Microneedle arrays coated with 5 or 3 layers of LB-MSN-DT were used to immunize mice and the elicited antibody responses were compared with those induced by hollow microneedle-injected liquid formulation of LB-MSN-DT. Liquid DT formulation with and without TMC (DT/TMC) injected by a hollow microneedle were used as controls. RESULTS: LB-MSN-DT had an average size of about 670 nm and a zeta potential of -35 mV. The encapsulation efficiency of DT in the nanoparticles was 77%. The amount of nano-encapsulated DT coated onto the microneedle array increased linearly with increasing number of the coating layers. Nano-encapsulated DT induced stronger immune responses than DT solution when delivered intradermally via hollow microneedles, but not when delivered via coated microneedles. CONCLUSION: Both the nano-encapsulation of DT and the type of microneedles affect the immunogenicity of the antigen.

Development of transdermal vitamin D3 (VD3) delivery system using combinations of PLGA nanoparticles and microneedles.

Although vitamin D3 (VD3), which is the main form of vitamin D, can be produced in human skin under the sunlight, vitamin D deficiency emerged as a major public health problem worldwide. Mainly, oral supplements or vitamin D-fortified foods are distributed to help supplementation of vitamin D. However, those oral methods are limitedly supplied in the Middle East countries, and oral absorption has low efficiency due to many barriers and various changes of conditions along the route. Then, it is recommended to take them every day in order to maintain the adequate serum level of vitamin D. Alternatively, transdermal delivery system could provide a convenient way to get sustained supplement of vitamin D by its advantages like avoiding first-pass effect of the liver and providing release for long periods of time. In this study, we introduced transdermal delivery system for sustained vitamin D release using coating microneedles that easily pierce the skin layer with enough mechanical strength and allow the localization of drugs within the dermal region. According to the experimental results, poly (lactic-co-glycolic acid) (PLGA) successfully encapsulated VD3 as a nanoparticle form with appropriate properties for transdermal delivery such as size distribution, skin compatibility, and effective release of encapsulated compound. Finally, PVD3 layers coated on solid microneedles were completely dissolved into intradermal region in porcine skin model and revealed better performance for VD3 release into plasma compared to ointment base transdermal method.

Diphtheria toxoid and N-trimethyl chitosan layer-by-layer coated pH-sensitive microneedles induce potent immune responses upon dermal vaccination in mice.

Dermal immunization using antigen-coated microneedle arrays is a promising vaccination strategy. However, reduction of microneedle sharpness and the available surface area for antigen coating is a limiting factor. To overcome these obstacles, a layer-by-layer coating approach can be applied onto pH-sensitive microneedles. Following this approach, pH-sensitive microneedle arrays (positively charged at coating pH5.8 and nearly uncharged at pH7.4) were alternatingly coated with negatively charged diphtheria toxoid (DT) and N-trimethyl chitosan (TMC), a cationic adjuvant. First, the optimal DT dose for intradermal immunization was determined in a dose-response study, which revealed that low-dose intradermal immunization was more efficient than subcutaneous immunization and that the EC50 dose of DT upon intradermal immunization is 3-fold lower, as compared to subcutaneous immunization. In a subsequent immunization study, microneedle arrays coated with an increasing number (2, 5, and 10) of DT/TMC bilayers resulted in step-wise increasing DT-specific immune responses. Dermal immunization with microneedle arrays coated with 10 bilayers of DT/TMC (corresponding with ±0.6µg DT delivered intradermally) resulted in similar DT-specific immune responses as subcutaneous immunization with 5µg of DT adjuvanted with aluminum phosphate (8-fold dose reduction). Summarizing, the layer-by-layer coating approach onto pH-sensitive microneedles is a versatile method to precisely control the amount of coated and dermally-delivered antigen that is highly suitable for dermal immunization.

Drug-coated microneedles for rapid and painless local anesthesia.

This study showed that drug-coated PLLA (Poly (L-lactide)) microneedle arrays can induce rapid and painless local anesthesia. Microneedle arrays were fabricated using a micro-molding technique, and the needle tips were coated with 290.6 ± 45.9 µg of lidocaine, the most widely used local anesthetic worldwide. A dip-coating device was newly designed for the coating step using an optimized coating formulation. Lidocaine coated on the arrays was released rapidly into PBS within 2 min, and its stability in storage lasted 3 weeks at 4, 25, and 37°C. Furthermore, the microneedle arrays showed consistent in vitro skin penetration and delivered 200.8 ± 43.9, 224.2 ± 39.3, and 244.1 ± 19.6 µg of lidocaine into the skin 1, 2, and 5 min after application with a high delivery efficiency of 69, 77, and 84%. Compared to a commercially available topical anesthetic EMLA® cream, a 22.0, 13.6, and 14.0-fold higher amount of lidocaine was delivered into the skin. Note, in vitro skin permeation of Lidocaine was also notably enhanced by a 2-min-application of the lidocaine-coated microneedle arrays. Altogether, these results suggest that the biocompatible lidocaine-coated PLLA microneedle arrays could provide significantly rapid local anesthesia in a painless manner without any of the issues from topical applications or hypodermic injections of local anesthetics.

5-Aminolevulinic acid coated microneedles for photodynamic therapy of skin tumors.

This study evaluated the potential of coated microneedles for improved dermal delivery of 5-aminolevulinic acid (5-ALA), which naturally gets converted by cells of the tissue in to a photosensitizer called protoporphyrin IX (PPIX). Microneedle patches containing 57 microneedles were coated with 5-ALA using an in-house developed micro-precision dip coater. The coating process was optimized to achieve higher 5-ALA loading on microneedles and a high delivery efficiency into porcine cadaver skin. Using 5 dips with 25% w/v 5-ALA solution, a mass of about 350µg of 5-ALA was coated per patch, which gave a delivery efficiency of about 90% in porcine cadaver skin. Bright-field and scanning electron microscopy established that coatings of 5-ALA on microneedles of the patch were uniform. In vivo dermal pharmacokinetics showed that delivery of just 350µg of 5-ALA using coated microneedles led to about 3.2-fold higher PPIX formation after 4h, as compared to topical application of 20% w/w 5-ALA in a conventional cream formulation (25mg cream). Furthermore, with use of coated microneedles, PPIX was observed in deeper regions of the skin (~480µm) as compared to topical 5-ALA cream formulation (~150µm). The potential of PPIX for photodynamic therapy was tested in vivo. After light exposure (633nm; 118J/cm(2)), PPIX got photosensitized, and due to higher initial amount of PPIX in the coated microneedle group, about twice the amount of PPIX was photobleached compared to topical cream application. Finally, even with a lower dose of just 1.75mg 5-ALA, coated microneedles suppressed the growth of subcutaneous tumors by ~57%, while a topical cream containing 5mg of 5-ALA did not suppress the tumor volume and led to tumor growth comparable to the untreated control group. Overall, the strategy of delivering 5-ALA using coated microneedles could be a promising approach for photodynamic therapy of skin tumors.