The Necessity to Investigate In Vivo Fate of Nanoparticle-Loaded Dissolving Microneedles

(Re)evolution in nanoparticles-loaded microneedle delivery systems: are we getting closer to a clinical translation?

The deposition of drug-loaded nanoparticles within the skin structure has been a challenge due to the inexorable skin barrier function. Unless specific nanoparticles like liposomes and lipid-based related vesicles, most nanoparticles cannot penetrate the epidermal layers by themselves. This is the reason why microneedle-based systems are nowadays the most straightforward systems in skin research. They can greatly bypass the stratum corneum and deposit the supramolecular cargo entities in the dermal layers, which can perform specific features such as drug-controlled release, specific targeting or stimuli-responsive behaviors. At this point, after more than 20 years of research using this nanoparticle-microneedle combination and all the positive results, the clinical experience is still so limited. Therefore, how is it possible that the everlasting promise of the clinical translation of these systems has not reached a real clinical practice? In this piece of work, based on authors' review, a series of limiting factors as the regulatory framework and guidelines are identified and discussed, while it is highlighted that revolutionary advances in the biomedical field such as 3D-printing technology and microfluidics will contribute to accelerate the clinical translation of nanoparticle-microneedle-based devices and make possible their use and entrance to the biomedical market.

Preparation and In Vitro/In Vivo Characterization of Mixed-Micelles-Loaded Dissolving Microneedles for Sustained Release of Indomethacin

Background/Objectives: Indomethacin (IDM) is commonly used to treat chronic inflammatory diseases such as rheumatoid arthritis and osteoarthritis. However, long-term oral IDM treatment can harm the gastrointestinal tract. This study presents a design for encapsulating IDM within mixed micelles (MMs)-loaded dissolving microneedles (DMNs) to improve and sustain transdermal drug delivery. Methods: Indomethacin-loaded mixed micelles (IDM-MMs) were prepared from Soluplus® and Poloxamer F127 by means of a thin-film hydration method. The MMs-loaded DMNs were fabricated using a two-step molding method and evaluated for storage stability, insertion ability, in vitro release, in vitro transdermal penetration, and in vivo PK/PD studies. Results: The obtained MMs were stable at 4 °C and 30 °C for 60 days. The in vitro IDM transdermal penetration was remarkably improved by the MMs-loaded DMNs compared to a commercial patch. A pharmacokinetic study demonstrated that the MMs-loaded DMNs had a relative bioavailability of 4.1 in comparison with the commercial patch. Furthermore, the MMs-loaded DMNs showed a significantly shorter lag time than the commercial patch, as well as a more stable plasma concentration than the DMNs without MMs. The therapeutic efficacy of the IDM DMNs was examined in Complete Freund's Adjuvant-induced arthritis mice. The IDM DMN treatment effectively reduced arthritis severity, resulting in decreased paw swelling, arthritis index, spleen hyperplasia, and serum IL-1β and TNF-α levels. Conclusions: Our findings demonstrated that the novel MMs-loaded DMNs were an effective strategy for sustained IDM release, providing an alternate route of anti-inflammatory drug delivery.

Soluble hyaluronic acid microneedle arrays mediated RGD-modified liposome delivery for pain relief during photodynamic therapy by blocking TRPV1

In photodynamic therapy (PDT), reactive oxygen species (ROS) are key products that induce cell death, and increasing amount of ROS is a crucial way to enhance PDT efficacy. However, the generated ROS stimulates the transient receptor potential vanilloid 1 channel (TRPV1), which can be activated in the pain pathway and then exacerbate pain. Herein, we utilized arginine-glycine-aspartate (RGD) peptide-modified liposomes for encapsulation Chlorin e6 (Ce6) and capsazepine (Cz), a receptor antagonist of TRPV1, to prepare drug-loaded liposomes, RLCC. Soluble hyaluronic acid microneedle arrays (MNs), which possess sufficient skin penetration capability and excellent biosafety, was applied for in situ delivery of RLCC. With the aid of RGD peptides, the efficiency of intracellular liposomal uptake and the dispersion of drugs in tumor after delivery by MNs were significantly enhanced, showcasing tremendous potential for improving the PDT efficacy. Besides, through the analysis of sciatic nerve signals in mice during PDT, RLCC demonstrated remarkable effectiveness in alleviating pain by significantly reducing nerve impulses. Hence, RLCC demonstrated outstanding effectiveness in PDT and effectively alleviated the associated pain. Overall, this research highlights the potential of utilizing MNs for the in situ delivery of RLCC, facilitating effective PDT while addressing the issue of pain during the treatment.