Dermatotoxicology of microneedles (MNs) in man

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.

A novel chlorin e6 derivative-mediated photodynamic therapy STBF-PDT reverses photoaging via the TGF-β pathway

OBJECTIVE

Photoaging is characterized by wrinkles in the skin and the deterioration of the skin barrier function, mainly caused by long-term exposure to ultraviolet (UV) radiation. Photodynamic therapy (PDT) has been shown to treat photoaging. The novel photosensitizer ShengTaiBuFen(STBF) is a derived substance of Chlorin e6(Ce6) that can exert photodynamic effects directly. In this study, we investigated the availability and the mechanism of STBF-PDT in the treatment of photoaging.

METHODS

Fluorophotometer was used to determine therapeutic parameters for in vivo experiments. Camera photographs, dermoscopy, HE and Masson staining, skin pH, trans epidermal water loss (TEWL), epidermal water content, and sebum testing were used together to evaluate the results of the treatment. Dark toxicity and therapeutic parameters for in vitro experiments were determined by CCK8 analysis. Scratch assay was used to identify the cell migration of STBF-PDT on HaCaT cells. qPCR and Western blot were used to evaluate the TGF-β/Smad signaling pathway in human dermal fibroblast (HDF) cells.

RESULTS

We investigated the optimal STBF concentration and time of incubation in vivo and in vitro experiments. STBF-PDT improved the skin phenotype of photoaged mice. The skin of photoaged mice treated with 80 J/cm² STBF-PDT became smooth, while skin flakes were reduced. The epidermis of STBF-PDT-treated mice was thinner, and the cells were neatly arranged, with increased dermal collagen. In vitro, STBF-PDT promoted the migration of HaCaT cells below a light dose of 0.1 J/cm². HDF cells co-cultured with HaCaT cells treated with low-dose STBF-PDT showed activation of the TGF-β pathway.

CONCLUSION

As a novel photosensitizer, STBF-mediated low-dose PDT could reverse photoaging via the TGF-β pathway.

Microneedling Outcomes in Early Post-Surgical Scars

BACKGROUND

Scars are a vexing sequela of surgery. Microneedling, also known as Minimally Invasive Percutaneous Collagen Induction (MIPCI), has demonstrated impressive improvements in chronic acne scars; however, no evidence exists for treating post-surgical scars during active wound healing. The purpose of this study was to demonstrate the utility and safe use of MIPCI in acute post-surgical scars.

METHODS

Twenty-five subjects who underwent surgery had scars treated with 3 treatments of MIPCI in the postoperative period. Scar assessment was measured by Vancouver Scar Scale (VSS), Patient & Observer Scar Assessment Scale (POSAS) and Global Aesthetic Improvement Scale (GAIS) after each of the 3 treatments and at final 2 month follow up.

RESULTS

Patients had positive improvement in VSS, POSAS and GAIS at 16-week post treatment initiation evaluation compared to initial measurement (p value<0.001). No statistically significant differences were noted when comparing the age of the patient, location of scars or Fitzpatrick Phototype Scales between patients. However, when comparing patients who began treatment early (week 6 to 7 post-op) to those who began treatment late (week 13 to 16 postop), there was a statistically significant difference in the POSAS group (p value <0.04).

CONCLUSIONS

Post-surgical scars treated with MIPCI in the maturation and remodeling phase had no adverse outcomes. Interestingly, our data shows treatment initiated early in the maturation phase (6-7 weeks post-op) while natural collagen formation was tapering off demonstrated improved aesthetic outcomes compared to treatments initiated late in the maturation phase (13-16wk post-op).

Novel transdermal device for delivery of triamcinolone for nail psoriasis treatment

ABSTRACT Introduction: Nail psoriasis treatment is challenging due to difficult drug delivery and systemic therapy toxicities. Self-dissolvable microneedle patches embedded with corticosteroids offers a potentially rapid, minimally invasive drug delivery platform with good efficacy and minimal adverse side effects. Methods: We conducted a 4-month prospective randomised controlled trial. Subjects with psoriatic nails were randomised to receive microneedle device delivered topical steroids on one hand and control treatment (topical Daivobet gel) on the other. Two independent dermatologists blinded to the treatment assignment scored their Nail Psoriasis Severity Index (NAPSI) during visits at baseline, 2 and 4 months. All treatment was discontinued after 2 months. Average NAPSI score on each hand was analysed. Results: A total of 25 participants were recruited, aged 22 to 73 years. Majority were Chinese (72%), followed by Indian and Malay. There was equal randomisation of treatment to the left and right nail. While there was a rapid significant improvement in average NAPSI score for the control arm at 2 months, the treatment arm had a greater, more sustained improvement of the NAPSI score at 4 months. The average NAPSI score improved for both treatment and control group at 4 months compared to baseline. However, only the NAPSI value improvement in the controls at 2 months compared to baseline was statistically significant (P=0.0039). No severe adverse effects were reported. Conclusion: To the best of our knowledge, this is the first prospective randomised control trial comparing microneedle technology against conventional topical steroids in nail psoriasis treatment. Our findings demonstrate microneedle technology is as efficacious as topical therapy. Keywords: Microneedle, nail, psoriasis

Recent advances in microneedles-based drug delivery device in the diagnosis and treatment of cancer

Microneedles are unique, novel and an effective approach designed to deliver therapeutic agents and immunobiologicals in several diseases. These tiny needle patches are designed to load vaccine, small or large drug molecule, heavy molecular weighted proteins, genes, antibodies, nanoparticles and many more. These nanoparticles loaded microneedles deliver drugs deep within the skin near underlying neutrophils, langerhans and dendritic cells and induces required immunological response. With the drawbacks associated with conventional methods of cancer chemotherapy, the focus was shifted towards use of microneedles in not just anti-cancer vaccine/drug delivery but also for their early diagnosis. This delivery device is also suited for synergistic approaches such as chemotherapy or gene therapy combined with photothermal or photodynamic therapy. The painless self-administrative device offers an alternative over traditional routes of drug delivery including systemic administration via hypodermic needles. Additionally, these microneedles can be fabricated and altered in shape, size and geometry and the material polymer can be chosen depending on use and release mechanism. This review consolidates positive results obtained from studies done for different type of microneedle array in several tumor cell lines and animal models. It further highlights the use of biodegradable polymers such as hydrogel or any dissolving polymer that can be utilized for sustained codelivery of drug/vaccine to shun the need of multiple dosing. It covers the existing limitations that still needs to be resolved and further highlights on the future aspects of their use in cancer therapy.

Nanomedicines and microneedles: a guide to their analysis and application

The fast-advancing progress in the research of nanomedicine and microneedle applications in the past two decades has suggested that the combination of the two concepts could help to overcome some of the challenges we are facing in healthcare. They include poor patient compliance with medication and the lack of appropriate administration forms that enable the optimal dose to reach the target site. Nanoparticles as drug vesicles can protect their cargo and deliver it to the target site, while evading the body's defence mechanisms. Unfortunately, despite intense research on nanomedicine in the past 20 years, we still haven't answered some crucial questions, e.g. about their colloidal stability in solution and their optimal formulation, which makes the translation of this exciting technology from the lab bench to a viable product difficult. Dissolvable microneedles could be an effective way to maintain and stabilise nano-sized formulations, whilst enhancing the ability of nanoparticles to penetrate the stratum corneum barrier. Both concepts have been individually investigated fairly well and many analytical techniques for tracking the fate of nanomaterials with their precious cargo, both in vitro and in vivo, have been established. Yet, to the best of our knowledge, a comprehensive overview of the analytical tools encompassing the concepts of microneedles and nanoparticles with specific and successful examples is missing. In this review, we have attempted to briefly analyse the challenges associated with nanomedicine itself, but crucially we provide an easy-to-navigate scheme of methods, suitable for characterisation and imaging the physico-chemical properties of the material matrix.

Microvascular effects of microneedles with subsequent histamin application in the skin prick test

BACKGROUND

Since decades, histamin applications are routinely performed in skin prick tests using a lancet. However, this technique is associated with various drawbacks.

MATERIALS AND METHODS

In healthy human subjects, we investigated the effects of microneedle-enhanced histamin delivery (wheal size, erythema size) in the skin microvasculature using polarized light spectroscopy imaging (Tissue Viability imaging, TiVi). Histamin was applied on microneedle-pretreated skin or on -untreated skin, to assess the microvascular response in the local skin.

RESULTS

In our results, histamin was delivered more rapidly into the skin after microneedle pretreatment compared to passive diffusion, visible as wheal and erythema.

CONCLUSION

The here presented technique might be useful for a personalized drug-testing system in the future.

Advances in Antimicrobial Microneedle Patches for Combating Infections

Skin infections caused by bacteria, viruses and fungi are difficult to treat by conventional topical administration because of poor drug penetration across the stratum corneum. This results in low bioavailability of drugs to the infection site, as well as the lack of prolonged release. Emerging antimicrobial transdermal and ocular microneedle patches have become promising medical devices for the delivery of various antibacterial, antifungal, and antiviral therapeutics. In the present review, skin anatomy and its barriers along with skin infection are discussed. Potential strategies for designing antimicrobial microneedles and their targeted therapy are outlined. Finally, biosensing microneedle patches associated with personalized drug therapy and selective toxicity toward specific microbial species are discussed.

Microvascular effects of microneedle application

BACKGROUND

The efficiency of transdermal drug delivery may be increased by pretreating the skin with microneedles, but distinct effects of microneedles and the microneedle-enhanced delivery of vasoactive drugs on the skin microvasculature are still not well investigated.

MATERIALS AND METHODS

In eight healthy human subjects, we measured the microvascular response to microneedle-induced microtraumas in the skin microvasculature using polarized light spectroscopy imaging (Tissue Viability imaging, TiVi). The microvascular response was assessed for up to 48 hours for three microneedle sizes (300 µm, 500 µm, and 750 µm) and for different pressures and application times.

RESULTS

In our results, microneedle application increased the local red blood cell (RBC) concentration for up to 24 hours dependent on the needle lengths, applied time, and force.

CONCLUSION

Optimization of microneedles size, pressure, and application time should be taken into account for future protocols for drug delivery and experimental provocations.

Evaluation of the clinical impact of repeat application of hydrogel-forming microneedle array patches

Hydrogel-forming microneedle array patches (MAPs) have been proposed as viable clinical tools for patient monitoring purposes, providing an alternative to traditional methods of sample acquisition, such as venepuncture and intradermal sampling. They are also undergoing investigation in the management of non-melanoma skin cancers. In contrast to drug or vaccine delivery, when only a small number of MAP applications would be required, hydrogel MAPs utilised for sampling purposes or for tumour eradication would necessitate regular, repeat applications. Therefore, the current study was designed to address one of the key translational aspects of MAP development, namely patient safety. We demonstrate, for the first time in human volunteers, that repeat MAP application and wear does not lead to prolonged skin reactions or prolonged disruption of skin barrier function. Importantly, concentrations of specific systemic biomarkers of inflammation (C-reactive protein (CRP); tumour necrosis factor-α (TNF-α)); infection (interleukin-1β (IL-1β); allergy (immunoglobulin E (IgE)) and immunity (immunoglobulin G (IgG)) were all recorded over the course of this fixed study period. No biomarker concentrations above the normal, documented adult ranges were recorded over the course of the study, indicating that no systemic reactions had been initiated in volunteers. Building upon the results of this study, which serve to highlight the safety of our hydrogel MAP, we are actively working towards CE marking of our MAP technology as a medical device.

STAR particles for enhanced topical drug and vaccine delivery

Drug delivery to the skin is highly constrained by the stratum corneum barrier layer¹. Here, we developed star-shaped particles, termed STAR particles, to dramatically increase skin permeability. STAR particles are millimeter-scale particles made of aluminum oxide or stainless steel with micron-scale projections designed to create microscopic pores across the stratum corneum. After gentle topical application for 10 s to porcine skin ex vivo, delivery of dermatological drugs and macromolecules, including those that cannot be given topically, was increased by 1 to 2 orders of magnitude. In mice treated with topical 5-fluorouracil, use of STAR particles increased the efficacy of the drug in suppressing the growth of subcutaneous melanoma tumors and prolonging survival. Moreover, topical delivery of tetanus toxoid vaccine to mice using STAR particles generated immune responses that were at least as strong as delivery of the vaccine by intramuscular injection, albeit at a higher dose for topical than intramuscular vaccine administration. STAR particles were well tolerated and effective at creating micropores when applied to the skin of human participants. Use of STAR particles provides a simple, low-cost and well-tolerated method for increasing drug and vaccine delivery to the skin and could widen the range of compounds that can be topically administered.