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

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.

Comparative efficacy evaluation of different penetration enhancement strategies for dermal delivery of poorly soluble drugs - A case with sertaconazole nitrate

The aim of this study was to compare the efficacy of different approaches for enhancement of dermal availability of the highly lipophilic antifungal model drug - sertaconazole nitrate (SN). For this purpose, a physical penetration enhancer - dissolving microneedles (MNs) was fabricated by filling moulds with liquid formulation based on polyvinylpyrrolidone and loaded with SN. Dissolving MNs were characterised regarding their morphological and mechanical characteristics. A penetration enhancement efficacy of MNs was evaluated in vitro using porcine ear skin in parallel with the efficacy of formerly developed chemical penetration enhancer - biocompatible microemulsion (ME) formulation. Moreover, an ability of solid silicon MNs to significantly improve delivery of SN from ME into the skin has also been investigated. The obtained results showed that dissolving MNs had satisfying morphological properties and mechanical strength. This type of MNs provided comparable drug deposition in the skin as ME formulation, but also revealed an indication of percutaneous absorption of a portion of the administered drug dose. However, the penetration/permeation study results were largely influenced by experimental setup and dosing regimen. Although solid silicon MNs assisted SN dermal delivery led to increase of drug cutaneous retention (1.9-fold) under infinite dosing regimen, the synergistic action of solid MNs and ME applied under finite dosing was more pronounced in comparison with the application either of physical (dissolving MNs) or chemical enhancer (ME) alone. Namely, SN amount accumulated into the skin increased up to 4.67 and 4.37 folds in comparison with ME and dissolving MNs alone, respectively, while reaching a significant decrease in drug permeation through the skin compared to the use of dissolving MNs. Application of ME per se was the only approach that provided selective in vitro dermal drug delivery without SN permeation across the skin. However, despite both types of the used MNs lead to SN permeation in vitro, the ratio between the drug amount deposited in the skin and SN content permeated was significantly higher for the combined approach (12.05) than for dissolving MNs (2.10). Therefore, a combination of solid silicon MNs and biocompatible ME favoured more pronouncedly SN skin accumulation, which is preferable in the treatment of skin fungal infections.

Etravirine-loaded dissolving microneedle arrays for long-acting delivery

A key challenge of HIV treatment with multiple antiretroviral drugs is patient adherence. Thus, there is an urgent need for long-acting depot systems for delivering drugs over an extended duration. Although the parenteral route is preferred for depot systems, it is associated with obvious drawbacks, such as painful injections, potentially-contaminated sharps waste, and the necessity of trained healthcare personnel for administration. Amongst a small number of alternatives in development microneedles are versatile delivery systems enabling systemic drug delivery and potentially improving patient adherence due to their capacity for self-administration. We have developed dissolving microneedle (DMNs) embedded with etravirine nanosuspension (ETR NS) as a long-acting HIV therapy to improve patient adherence. The ETR NS prepared by sonoprecipitation yielded particle sizes of 764 ± 96.2 nm, polydispersity indices of of 0.23 ± 0.02, and zeta potentials of -19.75 ± 0.55 mV. The DMNs loaded with ETR NS demonstrated 12.84 ± 1.33% ETR deposition in ex-vivo neonatal porcine skin after 6 h application. In in vivo rat pharmacokinetic studies, the Cmax exhibited by DMNs loaded with ETR powder and ETR NS were 158 ± 10 ng/mL and 177 ± 30 ng/mL, respectively. DMN groups revealed a higher t_1/2, Tmax, and mean residence time compared to intravenous ETR solutions, suggesting the long-acting potential of etravirine delivered intradermally using DMNs.

Microneedles for Extended Transdermal Therapeutics: A Route to Advanced Healthcare

Sustained release of drugs over a pre-determined period is required to maintain an effective therapeutic dose for variety of drug delivery applications. Transdermal devices such as polymeric microneedle patches and other microneedle-based devices have been utilized for sustained release of their payload. Swift clearing of drugs can be prevented either by designing a slow-degrading polymeric matrix or by providing physiochemical triggers to different microneedle-based devices for on-demand release. These long-acting transdermal devices prevent the burst release of drugs. This review highlights the recent advances of microneedle-based devices for sustained release of vaccines, hormones, and antiretrovirals with their prospective safe clinical translation.

Transdermal Delivery of Kidney-Targeting Nanoparticles Using Dissolvable Microneedles

INTRODUCTION

Chronic kidney disease (CKD) affects approximately 13% of the world's population and will lead to dialysis or kidney transplantation. Unfortunately, clinically available drugs for CKD show limited efficacy and toxic extrarenal side effects. Hence, there is a need to develop targeted delivery systems with enhanced kidney specificity that can also be combined with a patient-compliant administration route for such patients that need extended treatment. Towards this goal, kidney-targeted nanoparticles administered through transdermal microneedles (KNP/MN) is explored in this study.

METHODS

A KNP/MN patch was developed by incorporating folate-conjugated micelle nanoparticles into polyvinyl alcohol MN patches. Rhodamine B (RhB) was encapsulated into KNP as a model drug and evaluated for biocompatibility and binding with human renal epithelial cells. For MN, skin penetration efficiency was assessed using a Parafilm model, and penetration was imaged via scanning electron microscopy. In vivo, KNP/MN patches were applied on the backs of C57BL/6 wild type mice and biodistribution, organ morphology, and kidney function assessed.

RESULTS

KNP showed high biocompatibility and folate-dependent binding in vitro, validating KNP's targeting to folate receptors in vitro. Upon transdermal administration in vivo, KNP/MN patches dissolved within 30 min. At varying time points up to 48 h post-KNP/MN administration, higher accumulation of KNP was found in kidneys compared with MN that consisted of the non-targeting, control-NP. Histological evaluation demonstrated no signs of tissue damage, and kidney function markers, serum blood urea nitrogen and urine creatinine, were found to be within normal ranges, indicating preservation of kidney health.

CONCLUSIONS

Our studies show potential of KNP/MN patches as a non-invasive, self-administrable platform to direct therapies to the kidneys.

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

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

A Semi-Dissolving Microneedle Patch Incorporating TEMPO-Oxidized Bacterial Cellulose Nanofibers for Enhanced Transdermal Delivery

Although dissolving microneedles have garnered considerable attention as transdermal delivery tools, insufficient drug loading remains a challenge owing to their small dimension. Herein, we report a one-step process of synthesizing semi-dissolving microneedle (SDMN) patches that enable effective transdermal drug delivery without loading drugs themselves by introducing TEMPO-oxidized bacterial cellulose nanofibers (TOBCNs), which are well dispersed, while retaining their unique properties in the aqueous phase. The SDMN patch fabricated by the micro-molding of a TOBCN/hydrophilic biopolymer mixture had a two-layer structure comprising a water-soluble needle layer and a TOBCN-containing insoluble backing layer. Moreover, the SDMN patch, which had a hole in the backing layer where TOBCNs are distributed uniformly, could offer novel advantages for the delivery of large quantities of active ingredients. In vitro permeation analysis confirmed that TOBCNs with high water absorption capacity could serve as drug reservoirs. Upon SDMN insertion and the application of drug aqueous solution through the drug inlet hole, the TOBCNs rapidly absorbed the solution and supplied it to the needle layer. Simultaneously, the needle layer dissolved in body fluids and the drug solution to form micro-channels, which enabled the delivery of larger quantities of drugs to the skin compared to that enabled by solution application alone.

Bacterially sensitive nanoparticle-based dissolving microneedles of doxycycline for enhanced treatment of bacterial biofilm skin infection: A proof of concept study

The presence of bacterial biofilms in wounds is a main issue in the healing process. Conventional therapy of bacterial biofilms is hampered by the poor penetration of antibacterial agents through the physical barrier on the infected skin and the non-specific target of antibacterial agents. Here, we present a combination approach of bacterial sensitive nanoparticles (NPs) and dissolving microneedles (MNs) of doxycycline (DOX) for improved biofilm penetration and specifically delivering DOX to the infection site. The NPs were prepared from poly(lactic-co-glycolic acid) and poly (Ɛ-caprolactone) decorated with chitosan. The release of DOX was improved with the presence of bacterial producing biofilm up to 7-fold. The incorporation of these NPs into dissolving MNs was able to significantly enhance the dermatokinetic profiles of DOX, indicated by higher retention time compared to needle-free patches. Importantly, the antibiofilm activity in ex vivo biofilm model showed that after 48 h, the bacterial bioburdens decreased up to 99.99% following the application of this approach. The results presented here assist as proof of principle for the improvement of dermatokinetic profiles and antibiofilm activities of DOX, following its formulation into bacterial sensitive NPs and delivery via MN. Future studies must explore in vivo efficacy in a suitable animal model.

Pullulan-based dissolving microneedle arrays for enhanced transdermal delivery of small and large biomolecules

One specific technological advance in transdermal drug delivery is the development of dissolving microneedles (DMNs), which efficiently deliver therapeutics through a rapid dissolution of polymers after penetration into the skin. However, there is a limited range of water soluble, biodegradable polymers that can be used to manufacture DMN. Here, we report for the first time, the preparation and characterisation of a DMN system from the carbohydrate biopolymer, pullulan (PL). PL gels, of varying concentration, were studied for viscosity, film formation properties, and subsequently, microneedle formation. Model molecules and protein/peptide were loaded into PL DMN and characterised. The stability of model biomolecules, such as FITC-BSA and insulin, following DMN manufacture were assessed using circular dichroism. Ex-vivo porcine skin permeation studies using Franz diffusion cell apparatus for Flu-Na and FITC-BSA loaded PL-DMN were conducted. This study demonstrates that PL DMNs may serve as a promising tool for efficient transdermal drug delivery.

Advanced modification of drug nanocrystals by using novel fabrication and downstream approaches for tailor-made drug delivery

Drug nanosuspensions/nanocrystals have been recognized as one useful and successful approach for drug delivery. Drug nanocrystals could be further decorated to possess extended functions (such as controlled release) and designed for special in vivo applications (such as drug tracking), which make best use of the advantages of drug nanocrystals. A lot of novel and advanced size reduction methods have been invented recently for special drug deliveries. In addition, some novel downstream processes have been combined with nanosuspensions, which have highly broadened its application areas (such as targeting) besides traditional routes. A large number of recent research publication regarding as nanocrystals focuses on above mentioned aspects, which have widely attracted attention. This review will focus on the recent development of nanocrystals and give an overview of regarding modification of nanocrystal by some new approaches for tailor-made drug delivery.

Design and Development of Liquid Drug Reservoirs for Microneedle Delivery of Poorly Soluble Drug Molecules

The poor aqueous solubility of existing and emerging drugs is a major issue faced by the pharmaceutical industry. Water-miscible organic solvents, termed co-solvents, can be used to enhance the solubility of poorly soluble substances. Typically, drugs with poor aqueous solubility and Log P > 3 are not amenable to delivery across the skin. This study investigated the use of co-solvents as reservoirs to be used in combination with hydrogel-forming microneedles to enhance the transdermal delivery of hydrophobic compounds, namely Nile red, olanzapine and atorvastatin. A custom-made Franz cell apparatus was fabricated to test the suitability of a liquid drug reservoir in combination with polymeric microneedles. A co-solvency approach to reservoir formulation proved effective, with 83.30% ± 9.38% of Nile red dye, dissolved in 1 mL poly(ethylene glycol) (PEG 400), permeating neonatal porcine skin over 24 h. PEG 400 and propylene glycol were found to be suitable reservoir media for olanzapine and atorvastatin, with approximately 50% of each drug delivered after 24 h. This work provides crucial proof-of-concept evidence that the manipulation of microneedle reservoir properties is an effective method to facilitate microneedle-mediated delivery of hydrophobic compounds.

Enhanced Intradermal Delivery of Nanosuspensions of Antifilariasis Drugs Using Dissolving Microneedles: A Proof of Concept Study

Conventional oral administration of antifilariasis drugs results in nonspecific targeting of the drugs and the intradermal delivery of nanoparticles with sizes of <100 nm could be used to improve lymphatic uptake. This study investigated the combination of nanosuspension and dissolving microneedles (MN-NS) as an alternative intradermal delivery approach for the delivery of antifilariasis drugs, namely doxycycline, albendazole, and ivermectin. NS were fabricated and optimized using a bottom-up technique. The NS were then incorporated into the MN arrays. The optimized NS were <100 nm in diameter. Furthermore, MN-NS had suitable mechanical strength and insertion capabilities. The dermatokinetic study revealed that the delivery of drugs into the dermis of excised neonatal porcine skin by MNs was significantly higher than that from a needle-free patch, with 29.29 ± 4.65%, 31.54 ± 5.35%, and 34.54 ± 4.98% of doxycycline, albendazole sulfoxide, and ivermectin retained in the dermis after 24 h. The results presented here serve as proof of concept for the significant enhancement of drug retention times in the dermis, following their formulation into NS and delivery via MN. Leading on from these studies, future work must investigate in vivo lymphatic pharmacokinetic profiling of drugs formulated into NS, in a suitable animal model.

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.

Design, Formulation, and Evaluation of Novel Dissolving Microarray Patches Containing Rilpivirine for Intravaginal Delivery

Antiretroviral (ARV) drugs have, for many years, been studied and administered in the prevention and treatment of human immunodeficiency virus (HIV). Intramuscular (IM) injection of long acting (LA) ARVs are in clinical development, but injectable formulations require regular access to healthcare facilities and disposal facilities for sharps. The development of a discrete, self-administered, and self-disabling vehicle to deliver ARVs could obviate these issues. This study describes the formulation, mechanical characterization, and in vivo evaluation of dissolving microarray patches (MAPs) containing a LA nanosuspension of the ARV, rilpivirine (RPV, RPV LA), for vaginal delivery. This is the first study to apply MAPs into vaginal tissue. The RPV LA MAPs penetrate ex vivo skin and a synthetic vaginal skin model and withstand the effects of potential dragging motion across synthetic vaginal epithelium. In in vivo studies, the mean plasma concentration of RPV in rats at the 56 day endpoint (116.5 ng mL^-1 ) is comparable to that achieved in the IM control cohort (118.9 ng mL^-1 ). RPV is detected systemically, in lymph and vaginal tissue, indicating the potential to deliver RPV LA to primary sites of viral challenge and replication. This innovative research has future potential for patients and healthcare workers, particularly in low-resource settings.