Development and characterization of a dry reservoir-hydrogel-forming microneedles composite for minimally invasive delivery of cefazolin

Direct 3D printing of triple-responsive nanocomposite hydrogel microneedles for controllable drug delivery

Hydrogel microneedle patches have emerged as promising platforms for painless, minimally invasive, safe, and portable transdermal drug administration. However, the conventional mold-based fabrication processes and inherent single-functionality of such microneedles present significant hurdles to broader implementation. Herein, we have developed a novel approach utilizing a precursor solution of robust nanocomposite hydrogels to formulate photo-printable inks suitable for the direct 3D printing of high-precision, triple-responsive hydrogel microneedle patches through digital light processing (DLP) technology. The ink formulation comprises four functionally diverse monomers including 2-(dimethylamino)ethyl methacrylate, N-isopropylacrylamide, acrylic acid, and acrylamide, which were crosslinked by aluminum hydroxide nanoparticles (AH NPs) acting as both reinforcing agents and crosslinking centers. This results in the formation of a nanocomposite hydrogel characterized by exceptional mechanical strength, an essential attribute for the 3D printing of hydrogel microneeedle patches. Furthermore, this innovative 3D printing strategy facilitates facile customization of microneedle geometry and patch dimensions. As a proof-of-concept, we employed the fabricated hydrogel microneedles for transdermal delivery of bovine serum albumin (BSA). Importantly, these hydrogel microneedles displayed no cytotoxic effects and exhibited triple sensitivity to pH, temperature and glucose levels, thereby enabling more precise on-demand drug delivery. This study provides a universal method for the rapid fabrication of hydrogel microneedles with smart responsiveness for transdermal drug delivery applications.

Risperidone-cyclodextrin complex reservoir combined with hydrogel-forming microneedle array patches for enhanced transdermal delivery

Hydrogel-forming microneedle array patches (HFMAPs) are microneedles that create microconduits upon insertion and swelling in the skin, potentially allowing prolonged drug delivery without generating sharps waste. Delivering hydrophobic drugs using HFMAPs poses challenges, which can be addressed using solubility enhancers such as cyclodextrins (CDs). This study aimed to deliver risperidone (RIS) transdermally using HFMAPs. To enhance the aqueous solubility of RIS hydroxypropyl-beta-cyclodextrin (HP-β-CD) and hydroxypropyl-gamma-cyclodextrin (HP-γ-CD) were utilised and their performance was tested using phase solubility studies. The aqueous solubility of RIS was enhanced by 4.75-fold and 2-fold using HP-β-CD and HP-γ-CD, respectively. RIS-HP-β-CD complex (CX) and physical mixture (PM) directly compressed tablets were prepared and combined with HFMAPs. Among the tested formulations, RIS-HP-β-CD PM reservoirs with 11 x 11 PVA/PVP HFMAPs exhibited the best performance in ex vivo studies and were further evaluated in in vivo experiments using female Sprague Dawley rats. The extended wear time of the MAPs resulted in the sustained release of RIS and its active metabolite 9-hydroxyrisperidone (9-OH-RIS) in plasma samples, lasting from 3 to 5 days with a 1-day application and up to 10 days with a 5-day application. For a 1-day application, HFMAPs showed greater systemic exposure to RIS compared to intramuscular control (AUC0-t: 13330.05 ± 2759.95 ng/mL/hour versus 2706 ± 1472 ng/mL/hour). Moreover, RIS exposure was extended to 5 days (AUC0-t: 12292.37 ± 1801.94 ng/mL/hour). In conclusion, HFMAPs could serve as an alternative for delivering RIS in a sustained manner, potentially improving the treatment of schizophrenia.

The Synergistic Potential of Hydrogel Microneedles and Nanomaterials: Breaking Barriers in Transdermal Therapy

The stratum corneum, which acts as a strong barrier against external agents, presents a significant challenge to transdermal drug delivery. In this regard, microneedle (MN) patches, designed as modern systems for drug delivery via permeation through the skin with the ability to pass through the stratum corneum, are known to be convenient, painless, and effective. In fact, MN have shown significant breakthroughs in transdermal drug delivery, and among the various types, hydrogel MN (HMNs) have demonstrated desirable inherent properties. Despite advancements, issues such as limited loading capacity, uncontrolled drug release rates, and non-uniform therapeutic approaches persist. Conversely, nanomaterials (NMs) have shown significant promise in medical applications, however, their efficacy and applicability are constrained by challenges including poor stability, low bioavailability, limited payload capacity, and rapid clearance by the immune system. Incorporation of NMs within HMNs offers new prospects to address the challenges associated with HMNs and NMs. This combination can provide a promising field of research for improved and effective delivery of therapeutic agents and mitigate certain adverse effects, addressing current clinical concerns. The current review highlights the use of NMs in HMNs for various therapeutic and diagnostic applications.

Nanomaterials: leading immunogenic cell death-based cancer therapies

The field of oncology has transformed in recent years, with treatments shifting from traditional surgical resection and radiation therapy to more diverse and customized approaches, one of which is immunotherapy. ICD (immunogenic cell death) belongs to a class of regulatory cell death modalities that reactivate the immune response by facilitating the interaction between apoptotic cells and immune cells and releasing specific signaling molecules, and DAMPs (damage-associated molecular patterns). The inducers of ICD can elevate the expression of specific proteins to optimize the TME (tumor microenvironment). The use of nanotechnology has shown its unique potential. Nanomaterials, due to their tunability, targeting, and biocompatibility, have become powerful tools for drug delivery, immunomodulators, etc., and have shown significant efficacy in clinical trials. In particular, these nanomaterials can effectively activate the ICD, trigger a potent anti-tumor immune response, and maintain long-term tumor suppression. Different types of nanomaterials, such as biological cell membrane-modified nanoparticles, self-assembled nanostructures, metallic nanoparticles, mesoporous materials, and hydrogels, play their respective roles in ICD induction due to their unique structures and mechanisms of action. Therefore, this review will explore the latest advances in the application of these common nanomaterials in tumor ICD induction and discuss how they can provide new strategies and tools for cancer therapy. By gaining a deeper understanding of the mechanism of action of these nanomaterials, researchers can develop more precise and effective therapeutic approaches to improve the prognosis and quality of life of cancer patients. Moreover, these strategies hold the promise to overcome resistance to conventional therapies, minimize side effects, and lead to more personalized treatment regimens, ultimately benefiting cancer treatment.

Development of ropivacaine hydrochloride-loaded dissolving microneedles as a local anesthetic agent: A proof-of-concept

Ropivacaine hydrochloride (RPL) is a local anesthetic agent that has been widely used for the treatment of pain during or after surgery. However, this drug is only available in parenteral dosage form and may contribute to the infiltration of RPL into the plasma, causing some undesirable side effects. Intradermal delivery of RPL using dissolving microneedles may become a promising strategy to deliver such drugs into the skin. This research aimed to develop RPL-loaded dissolving microneedles (DMN-RPLs) as a proof of the concept of intradermal delivery of a local anesthetic. The DMN-RPLs were fabricated using either centrifugation or air-pressurized chamber methods. Several polymers, such as poly(vinyl pyrrolidone) (PVP), poly(vinyl alcohol) (PVA), and sodium hyaluronate (SH), were utilized for manufacturing the DMN-RPLs. The prepared DMN-RPLs were assessed for their thermal properties, chemical bonds, mechanical strength, insertion ability, skin-dissolution study, and drug content. Furthermore, in-skin deposition and dermatokinetic studies were also performed. The results showed that F9 (30 % w/w PVP-4 % w/w SH) and F10 (30 % w/w PVP-5 % w/w PVA) containing 5 % w/w of RPL were the most promising formulations, as shown by their needle height reduction (<10 %) and insertion depth (∼400 μm). Both formulations were also able to deliver more than 60 % of the RPL contained in the DMNs into the epidermis, dermis, and receiver compartment. This study, for the first time, has provided a proof concept to deliver RPL as a local anesthetic using DMNs and the intradermal route, aiming to minimize pain and discomfort during administration and improve the patient's experience.

Development of Norelgestromin Dissolving Bilayer Microarray Patches for Sustained Release of Hormonal Contraceptive

Microarray patches (MAPs) offer a noninvasive and patient-friendly drug delivery method, suitable for self-administration, which is especially promising for low- and middle-income country settings. This study focuses on the development of dissolving bilayer MAPs loaded with norelgestromin (NGMN) as a first step towards developing a future potential drug delivery system for sustained hormonal contraception. The fabricated MAPs were designed with the appropriate needle lengths to penetrate the stratum corneum, while remaining minimally stimulating to dermal nociceptors. Ex vivo assessments showed that the MAPs delivered an average of 176 ± 60.9 μg of NGMN per MAP into excised neonatal porcine skin, representing 15.3 ± 5.3% of the loaded drug. In vivo pharmacokinetic analysis in Sprague Dawley rats demonstrated a Tmax of 4 h and a Cmax of 67.4 ± 20.1 ng/mL for the MAP-treated group, compared to a Tmax of 1 h and a Cmax of 700 ± 138 ng/mL for the intramuscular (IM) injection group, with a relative bioavailability of approximately 10% for the MAPs. The MAP-treated rats maintained plasma levels sufficient for therapeutic effects for up to 7 days after a single application. These results indicate the potential of NGMN-loaded dissolving bilayer MAPs, with further development focused on extending the release duration and improving bioavailability for prolonged contraceptive effects.

Transdermal Delivery of Pramipexole Using Microneedle Technology for the Potential Treatment of Parkinson's Disease

Parkinson's disease (PD) is a debilitating neurodegenerative disease primarily impacting neurons responsible for dopamine production within the brain. Pramipexole (PRA) is a dopamine agonist that is currently available in tablet form. However, individuals with PD commonly encounter difficulties with swallowing and gastrointestinal motility, making oral formulations less preferable. Microneedle (MN) patches represent innovative transdermal drug delivery devices capable of enhancing skin permeability through the creation of microconduits on the surface of the skin. MNs effectively reduce the barrier function of skin and facilitate the permeation of drugs. The work described here focuses on the development of polymeric MN systems designed to enhance the transdermal delivery of PRA. PRA was formulated into both dissolving MNs (DMNs) and directly compressed tablets (DCTs) to be used in conjunction with hydrogel-forming MNs (HFMNs). In vivo investigations using a Sprague-Dawley rat model examined, for the first time, if it was beneficial to prolong the application of DMNs and HFMNs beyond 24 h. Half of the patches in the MN cohorts were left in place for 24 h, whereas the other half remained in place for 5 days. Throughout the entire 5 day study, PRA plasma levels were monitored for all cohorts. This study confirmed the successful delivery of PRA from DMNs (Cmax = 511.00 ± 277.24 ng/mL, Tmax = 4 h) and HFMNs (Cmax = 328.30 ± 98.04 ng/mL, Tmax = 24 h). Notably, both types of MNs achieved sustained PRA plasma levels over a 5 day period. In contrast, following oral administration, PRA remained detectable in plasma for only 48 h, achieving a Cmax of 159.32 ± 113.43 ng/mL at 2 h. The HFMN that remained in place for 5 days demonstrated the most promising performance among all investigated formulations. Although in the early stages of development, the findings reported here offer a hopeful alternative to orally administered PRA. The sustained plasma profile observed here has the potential to reduce the frequency of PRA administration, potentially enhancing patient compliance and ultimately improving their quality of life. This work provides substantial evidence advocating the development of polymeric MN-mediated drug delivery systems to include sustained plasma levels of hydrophilic pharmaceuticals.

Application of hydrogel microneedles in the oral cavity

Microneedles are a transdermal drug delivery system in which the needle punctures the epithelium to deliver the drug directly to deep tissues, thus avoiding the influence of the first-pass effect of the gastrointestinal tract and minimizing the likelihood of pain induction. Hydrogel microneedles are microneedles prepared from hydrogels that have good biocompatibility, controllable mechanical properties, and controllable drug release and can be modified to achieve environmental control of drug release in vivo. The large epithelial tissue in the oral cavity is an ideal site for drug delivery via microneedles. Hydrogel microneedles can overcome mucosal hindrances to delivering drugs to deep tissues; this prevents humidity and a highly dynamic environment in the oral cavity from influencing the efficacy of the drugs and enables them to obtain better therapeutic effects. This article analyzes the materials and advantages of common hydrogel microneedles and reviews the application of hydrogel microneedles in the oral cavity.

Bioavailability enhancement of sildenafil citrate via hydrogel-forming microneedle strategy in combination with cyclodextrin complexation

Sildenafil citrate (SIL) as a first-line treatment for erectile dysfunction is currently reported to have poor solubility and bioavailability. Moreover, SIL undergoes first-pass metabolism when taken orally and its injection can lead to discomfort. In this study, we introduce a novel transdermal delivery system that integrates hydrogel-forming microneedles with the inclusion complex tablet reservoir. The hydrogel-forming microneedle was prepared from a mixture of polymers and crosslinkers through a crosslinking process. Importantly, the formulations showed high swelling capacity (>400 %) and exhibited adequate mechanical and penetration properties (needle height reduction < 10 %), penetrating up to five layers of Parafilm® M (assessed to reach the dermis layer). Furthermore, to improve the solubility of SIL in the reservoir, the SIL was pre-complexed with β-cyclodextrin. Molecular docking analysis showed that SIL was successfully encapsulated into the β-cyclodextrin cavity and was the most suitable conformation compared to other CD derivatives. Moreover, to maximize SIL delivery, sodium starch glycolate was also added to the reservoir formulation. As a proof of concept, in vivo studies demonstrated the effectiveness of this concept, resulting in a significant increase in AUC (area under the curve) compared to that obtained after administration of pure SIL oral suspension, inclusion complex, and Viagra® with relative bioavailability > 100 %. Therefore, the approach developed in this study could potentially increase the efficacy of SIL in treating erectile dysfunction by being non-invasive, safe, avoiding first-pass metabolism, and increasing drug bioavailability.

New graphene-containing pharmaceutical formulations for infrared lamps-based phototherapy of skin cancer: In vitro validation and ex-vivo human skin permeation

Basal cell carcinoma (BCC) is the most common form of human cancer, and treatment usually involves surgery, with alternative strategies being needed. We propose the use of carbopol hydrogels (HG) for topical administration of nanographene oxide (GOn) and partially-reduced nanographene oxide (p-rGOn) for photothermal therapy (PTT) of BCC. GOn and p-rGOn incorporated into the HG present lateral sizes ∼200 nm, being stable for 8 months. After 20 min irradiation with an infrared (IR) photothermal therapy lamp (15.70 mW cm-2), GOn-HG increased temperature to 44.7 °C, while p-rGOn-HG reached 47.0 °C. Human skin fibroblasts (HFF-1) cultured with both hydrogels (250 μg mL-1) maintained their morphology and viability. After 20 min IR irradiation, p-rGOn HG (250 μg mL-1) completely eradicated skin cancer cells (A-431). Ex vivo human skin permeability tests showed that the materials can successfully achieve therapeutic concentrations (250 μg mL-1) inside the skin, in 2.0 h for GO HG or 0.5 h for p-rGOn HG.

Pharmaceutical Formulations Containing Graphene and 5-Fluorouracil for Light-Emitting Diode-Based Photochemotherapy of Skin Cancer

Nonmelanoma skin cancer (NMSC) is the most common cancer worldwide, among which 80% is basal cell carcinoma (BCC). Current therapies' low efficacy, side effects, and high recurrence highlight the need for alternative treatments. In this work, a partially reduced nanographene oxide (p-rGOn) developed in our laboratory was used. It has been achieved through a controlled reduction of nanographene oxide via UV-C irradiation that yields small nanometric particles (below 200 nm) that preserve the original water stability while acquiring high light-to-heat conversion efficiency. The latter is explained by a loss of carbon-oxygen single bonds (C-O) and the re-establishment of sp2 carbon bonds. p-rGOn was incorporated into a Carbopol hydrogel together with the anticancer drug 5-fluorouracil (5-FU) to evaluate a possible combined PTT and chemotherapeutic effect. Carbopol/p-rGOn/5-FU hydrogels were considered noncytotoxic toward normal skin cells (HFF-1). However, when A-431 skin cancer cells were exposed to NIR irradiation for 30 min in the presence of Carbopol/p-rGOn/5-FU hydrogels, almost complete eradication was achieved after 72 h, with a 90% reduction in cell number and 80% cell death of the remaining cells after a single treatment. NIR irradiation was performed with a light-emitting diode (LED) system, developed in our laboratory, which allows adjustment of applied light doses to achieve a safe and selective treatment, instead of the standard laser systems that are associated with damages in the healthy tissues in the tumor surroundings. Those are the first graphene-based materials containing pharmaceutical formulations developed for BCC phototherapy.

MAP-box: a novel, low-cost and easy-to-fabricate 3D-printed box for the storage and transportation of dissolving microneedle array patches

Research on the use of microarray patches (MAPs) has progressed at an unprecedented rate over the years, leading to the development of many novel drug delivery systems. As the technology approaches patients, there are several key aspects that ought to be addressed in order to facilitate the smooth translation of MAPs from bench to bedside. One integral factor includes the choice of devices and packaging for the storage of MAPs. In the current work, a slide-and-seal box, MAP-box, was developed for the storage of dissolving MAPs, using fused-deposition modelling. The device has been designed to act as a pill-box for MAPs not only to provide protection for MAPs from the environment, but also to improve patient's adherence to treatment. The overall design of the MAP-box was simple, yet offers the capability of sealing and protecting dissolving MAPs up to 30 days. Donepezil HCl was formulated into a dissolvable MAP, which was used to treat dementia related to Alzheimer's disease. This compound was used as a model formulation to evaluate the utility of the 3D printed MAP-box when placed under three storage conditions: 5 °C and ambient humidity, 25 °C and 65% relative humidity and 40 °C and 75% relative humidity. It was shown that the slide-and-seal box was able to confer protection to MAPs for up to 30 days under accelerated stability study conditions as the drug loading, mechanical properties and insertion properties of MAPs remained unaffected when compared to the unpackaged MAPs stored under these same parameters. These preliminary data provide evidence that the MAP-box prototype may be of great utility for the storage of single or multiple MAPs. Nevertheless, future work will be needed to evaluate their patient usability and its application to different types of MAP systems to fully validate the overall robustness of the prototype.

Hydrogel-Based Microneedle as a Drug Delivery System

The skin is considered the largest and most accessible organ in the human body, and allows the use of noninvasive and efficient strategies for drug administration, such as the transdermal drug delivery system (TDDS). TDDSs are systems or patches, with the ability and purpose to deliver effective and therapeutic doses of drugs through the skin. Regarding the specific interaction between hydrogels (HG) and microneedles (MNs), we seek to find out how this combination would be applied in the context of drug delivery, and we detail some possible advantages of the methods used. Depending on the components belonging to the HG matrix, we can obtain some essential characteristics that make the combination of hydrogels-microneedles (HG-MNs) very advantageous, such as the response to external stimuli, among others. Based on multiple characteristics provided by HGMNs that are depicted in this work, it is possible to obtain unique properties that include controlled, sustained, and localized drug release, as well as the possibility of a synergistic association between the components of the formulation and the combination of more than one bioactive component. In conclusion, a system based on HG-MNs can offer many advantages in the biomedical field, bringing to light a new technological and safe system for improving the pharmacokinetics and pharmacodynamics of drugs and new treatment perspectives.

Fabrication and characterisation of poly(sulfonated) and poly(sulfonic acid) dissolving microneedles for delivery of antibiotic and antifungal agents

Skin and soft tissue infections (SSTIs) arise from microbial ingress into the skin. In this study, poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (polyAMPS), which has been reported to exhibit antimicrobial properties was synthesised for the manufacture of microarray patches (MAPs). The free acid and sodium salt of polyAMPS with controlled molar masses and narrow dispersity were synthesised via reversible addition - fragmentation chain-transfer (RAFT) polymerisation reaction with a monomer conversion of over 99%, as determined by 1H NMR. The polymers were shown to be biocompatible when evaluated using a fibroblast dermal cell line while agar plating assay using cultures of C. albican demonstrated that the acid form of polyAMPS exhibited antimicrobial inhibition, which is potentiated in the presence of antimicrobial agents. The synthesised polymers were then used to fabricate dissolving MAPs, which were loaded with either ITRA or levofloxacin (LEV). The MAPs displayed acceptable mechanical resistance and punctured ex vivo skin to a depth of 600 µm. Skin deposition studies revealed that the MAPs were able to administer up to ∼ 1.9 mg of LEV (delivery efficiency: 94.7%) and ∼ 0.2 mg of ITRA (delivery efficiency: 45.9%), respectively. Collectively, the synthesis and development of this novel pharmaceutical system may offer a strategy to manage SSTIs.

Fabrication of 3D Printed Hollow Microneedles by Digital Light Processing for the Buccal Delivery of Actives

In the present study, two different microneedle devices were produced using digital light processing (DLP). These devices hold promise as drug delivery systems to the buccal tissue as they increase the permeability of actives with molecular weights between 600 and 4000 Da. The attached reservoirs were designed and printed along with the arrays as a whole device. Light microscopy was used to quality control the printability of the designs, confirming that the actual dimensions are in agreement with the digital design. Non-destructive volume imaging by means of microfocus computed tomography was employed for dimensional and defect characterization of the DLP-printed devices, demonstrating the actual volumes of the reservoirs and the malformations that occurred during printing. The penetration test and finite element analysis showed that the maximum stress experienced by the needles during the insertion process (10 N) was below their ultimate compressive strength (240-310 N). Permeation studies showed the increased permeability of three model drugs when delivered with the MN devices. Size-exclusion chromatography validated the stability of all the actives throughout the permeability tests. The safety of these printed devices for buccal administration was confirmed by histological evaluation and cell viability studies using the TR146 cell line, which indicated no toxic effects.

Preparation and Evaluation of Auxiliary Permeable Microneedle Patch Composed of Polyvinyl Alcohol and Eudragit NM30D Aqueous Dispersion

Poor transdermal permeability limits the possibility of most drug delivery through the skin. Auxiliary permeable microneedles (AP-MNs) with a three-dimensional network structure can effectively break the skin stratum corneum barrier and assist in the transdermal delivery of active ingredients. Herein, we propose a simple method for preparing AP-MNs using polyvinyl alcohol and Eudragit NM30D for the first time. To optimize the formulation of microneedles, the characteristics of swelling properties, skin insertion, solution viscosity, and needle integrity were systematically examined. Additionally, the morphology, mechanical strength, formation mechanism, skin permeability, swelling performance, biocompatibility, and in vitro transdermal drug delivery of AP-MNs were evaluated. The results indicated that the microneedles exhibited excellent mechanical-strength and hydrogel-forming properties after swelling. Further, it proved that a continuous and unblockable network channel was created based on physical entanglement and encapsulation of two materials. The 24 h cumulative permeation of acidic and alkaline model drugs, azelaic acid and matrine, were 51.73 ± 2.61% and 54.02 ± 2.85%, respectively, significantly enhancing the transdermal permeability of the two drugs. In summary, the novel auxiliary permeable microneedles prepared through a simple blending route of two materials was a promising and valuable way to improve drug permeation efficiency.

Metronidazole nanosuspension loaded dissolving microarray patches: An engineered composite pharmaceutical system for the treatment of skin and soft tissue infection

Bacteroides fragilis is one of the most common causative group of microorganisms that is associated with skin and soft tissue infections (SSTI). Metronidazole (MTZ) is the drug of choice used in the treatment of SSTI caused by the bacterium. However, owing to its physiochemical properties, MTZ have limited skin permeation, which render the drug unsuitable for the treatment of deep-rooted SSTIs. One strategy to overcome this limitation is to reformulate MTZ into nanosuspension which will then be loaded into dissolving microarray patches (MAPs) for the treatment of SSTIs caused by B. fragilis. Herein, we report for the first time on the preparation and optimisation of MAP loaded with MTZ nanosuspension (MTZ-NS). After screening a range of polymeric surfactants, we identified that Soluplus® resulted in the formation of MTZ-NS with the smallest particle size (115 nm) and a narrow PDI of 0.27. Next, the MTZ-NS was further optimised using a design of experiments (DoE) approach. The optimised MTZ-NS was then loaded into dissolving MAPs with varying MTZ-NS content. Furthermore, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and cell proliferation assays along with LIVE/DEAD™ staining on the 3T3L1 cell line showed that the MTZ-NS loaded dissolving MAPs displayed minimal toxicity and acceptable biocompatibility. In vitro dermatokinetic studies showed that the MTZ-NS loaded MAPs were able to deliver the nitroimidazole antibiotic across all strata of the skin resulting in a delivery efficiency of 95 % after a 24-hour permeation study. Lastly, agar plating assay using bacterial cultures of B. fragilis demonstrated that MTZ-NS loaded MAP resulted in complete bacterial inhibition in the entire plate relative to the control group. Should this formulation be translated into clinical practice, this pharmaceutical approach may provide a minimally invasive strategy to treat SSTIs caused by B. fragilis.

Microneedle-Mediated Permeation Enhancement of Chlorhexidine Digluconate: Mechanistic Insights Through Imaging Mass Spectrometry

PURPOSE

Chlorhexidine digluconate (CHG) is a first-line antiseptic agent typically applied to the skin as a topical solution prior to surgery due to its efficacy and safety profile. However, the physiochemical properties of CHG limits its cutaneous permeation, preventing it from reaching potentially pathogenic bacteria residing within deeper skin layers. Thus, the utility of a solid oscillating microneedle system, Dermapen®, and a CHG-hydroxyethylcellulose (HEC) gel were investigated to improve the intradermal delivery of CHG.

METHODS

Permeation of CHG from the commercial product, Hibiscrub®, and HEC-CHG gels (containing 1% or 4% CHG w/w) was assessed in intact skin, or skin that had been pre-treated with microneedles of different array numbers, using an Franz diffusion cells and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS).

RESULTS

Gels containing 1% and 4% CHG resulted in significantly increased depth permeation of CHG compared to Hibiscrub® (4% w/v CHG) when applied to microneedle pre-treated skin, with the effect being more significant with the higher array number. ToF-SIMS analysis indicated that the depth of dermal penetration achieved was sufficient to reach the skin strata that typically harbours pathogenic bacteria, which is currently inaccessible by Hibiscrub®, and showed potential lateral diffusion within the viable epidermis.

CONCLUSIONS

This study indicates that HEC-CHG gels applied to microneedle pre-treated skin may be a viable strategy to improve the permeation CHG into the skin. Such enhanced intradermal delivery may be of significant clinical utility for improved skin antisepsis in those at risk of a skin or soft tissue infection following surgical intervention.

Microneedle-based ocular drug delivery systems - recent advances and challenges

Eye diseases and injuries constitute a significant clinical problem worldwide. Safe and effective delivery of drugs to the eye is challenging mostly due to the presence of ocular barriers and clearance mechanisms. In everyday practice, the traditional eye drops, gels and ointments are most often used. Unfortunately, they are usually not well tolerated by patients due to the need for frequent use as well as the discomfort during application. Therefore, novel drug delivery systems with improved biopharmaceutical properties are a subject of ongoing scientific investigations. Due to the developments in microtechnology, in recent years, there has been a remarkable advance in the development of microneedle-based systems as an alternative, non-invasive form for administering drugs to the eye. This review summarizes the latest achievements in the field of obtaining microneedle ocular patches. In the manuscript, the most important manufacturing technologies, microneedle classification, and the research studies related to ophthalmic application of microneedles are presented. Finally, the most important advantages and drawbacks, as well as potential challenges related to the unique anatomy and physiology of the eye are summarized and discussed.