The Progress in the Application of Dissolving Microneedles in Biomedicine

Emerging biomedical technologies for scarless wound healing

Complete wound healing without scar formation has attracted increasing attention, prompting the development of various strategies to address this challenge. In clinical settings, there is a growing preference for emerging biomedical technologies that effectively manage fibrosis following skin injury, as they provide high efficacy, cost-effectiveness, and minimal side effects compared to invasive and costly surgical techniques. This review gives an overview of the latest developments in advanced biomedical technologies for scarless wound management. We first introduce the wound healing process and key mechanisms involved in scar formation. Subsequently, we explore common strategies for wound treatment, including their fabrication methods, superior performance and the latest research developments in this field. We then shift our focus to emerging biomedical technologies for scarless wound healing, detailing the mechanism of action, unique properties, and advanced practical applications of various biomedical technology-based therapies, such as cell therapy, drug therapy, biomaterial therapy, and synergistic therapy. Finally, we critically assess the shortcomings and potential applications of these biomedical technologies and therapeutic methods in the realm of scar treatment.

Visualizing the transdermal delivery of berberine loaded within chitosan microneedles using mass spectrometry imaging

Berberine (BR), an alkaloid isolated from the Chinese traditional medicine Coptidis rhizoma, exhibits therapeutic effects on several diseases including bacterial infections, diabetes, and hyperlipidemia, but the oral availability is poor. In this work, we prepared the chitosan microneedle array-loaded BR (BR-CS MNAs) to transdermally deliver BR, and the spatial distribution of BR in heterogeneous skin tissues was analyzed and imaged by matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI). Some endogenous phospholipids with specific spatial distribution were used to differentiate the epidermis and dermis regions of the skin. The results showed that BR was effectively delivered and could permeate to both epidermis and dermis regions of the skin. This demonstrated the feasibility of MALDI-MSI to evaluate the transdermal delivery efficiency of microneedle arrays and suggested BR could be transdermally delivered by CS MNAs.

Dissolvable microneedle-based wound dressing transdermally and continuously delivers anti-inflammatory and pro-angiogenic exosomes for diabetic wound treatment

Due to overactive inflammation and hindered angiogenesis, self-healing of diabetic wounds (DW) remains challenging in the clinic. Platelet-derived exosomes (PLT-Exos), a novel exosome capable of anti-inflammation and pro-angiogenesis, show great potential in DW treatment. However, previous administration of exosomes into skin wounds is topical daub or intradermal injection, which cannot intradermally deliver PLT-Exos into the dermis layer, thus impeding its long-term efficacy in anti-inflammation and pro-angiogenesis. Herein, a dissolvable microneedle-based wound dressing (PLT-Exos@ADMMA-MN) was developed for transdermal and long-term delivery of PLT-Exos. Firstly, a photo-crosslinking methacrylated acellular dermal matrix-based hydrogel (ADMMA-GEL), showing physiochemical tailorability, fast-gelling performance, excellent biocompatibility, and pro-angiogenic capacities, was synthesized as a base material of our dressing. For endowing the dressing with anti-inflammation and pro-angiogenesis, PLT-Exos were encapsulated into ADMMA-GEL with a minimum effective concentration determined by our in-vitro experiments. Then, in-vitro results show that this dressing exhibits excellent properties in anti-inflammation and pro-angiogenesis. Lastly, in-vivo experiments showed that this dressing could continuously and transdermally deliver PLT-Exos into skin wounds to switch local macrophage into M2 phenotype while stimulating neovascularization, thus proving a low-inflammatory and pro-angiogenic microenvironment for DW healing. Collectively, this study provides a novel wound dressing capable of suppressing inflammation and stimulating vascularization for DW treatment.

Dissolving microneedles: standing out in melanoma treatment

Melanoma is one of the most significant and dangerous superficial skin tumors with a high fatality rate, thanks to its high invasion rate, drug resistance and frequent metastasis properties. Unfortunately, researchers for decades have demonstrated that the outcome of using conventional therapies like chemotherapy and immunotherapy with normal drug delivery routes, such as an oral route to treat melanoma was not satisfactory. The severe adverse effects, slow drug delivery efficiency and low drug accumulation at targeted malignancy sites all lead to poor anti-cancer efficacy and terrible treatment experience. As a novel transdermal drug delivery system, microneedles (MNs) have emerged as an effective solution to help improve the low cure rate of melanoma. The excellent characteristics of MNs make it easy to penetrate the stratum corneum (SC) and then locally deliver the drug towards the lesion without drug leakage to mitigate the occurrence of side effects and increase the drug accumulation. Therefore, loading chemotherapeutic drugs or immunotherapy drugs in MNs can address the problems mentioned above, and MNs play a crucial role in improving the curative effect of conventional treatment methods. Notably, novel tumor therapies like photothermal therapy (PTT), photodynamic therapy (PDT) and chemodynamic therapy (CDT) have shown good application prospects in the treatment of melanoma, and MNs provide a valid platform for the combination of conventional therapies and novel therapies by encompassing different therapeutic materials in the matrix of MNs. The synergistic effect of multiple therapies can enhance the therapeutic efficacy compared to single therapies, showing great potential in melanoma treatment. Dissolving MNs have been the most commonly used microneedles in the treatment of melanoma in recent years, mainly because of their simple fabrication procedure and enough drug loading. So, considering the increasing use of dissolving MNs, this review collects research studies published in the last four years (2020-2024) that have rarely been included in other reviews to update the progress of applications of dissolving MNs in anti-melanoma treatment, especially in synergistic therapies. This review also presents current design and fabrication methods of dissolving MNs; the limitations of microneedle technology in the treatment of melanoma are comprehensively discussed. This review can provide valuable guidance for their future development.

Iontophoresis and electroporation-assisted microneedles: advancements and therapeutic potentials in transdermal drug delivery

Transdermal drug delivery (TDD) using electrically assisted microneedle (MN) systems has emerged as a promising alternative to traditional drug administration routes. This review explores recent advancements in this technology across various therapeutic applications. Integrating iontophoresis (IP) and electroporation (EP) with MN technology has shown significant potential in improving treatment outcomes for various conditions. Studies demonstrate their effectiveness in enhancing vaccine and DNA delivery, improving diabetes management, and increasing efficacy in dermatological applications. The technology has also exhibited promise in delivering nonsteroidal anti-inflammatory drugs (NSAIDs), treating multiple sclerosis, and advancing obesity and cancer therapy. These systems offer improved drug permeation, targeted delivery, and enhanced therapeutic effects. While challenges remain, including safety concerns and technological limitations, ongoing research focuses on optimizing these systems for broader clinical applications. The future of electrically assisted MN technologies in TDD appears promising, with potential advancements in personalized medicine, smart monitoring systems, and expanded therapeutic applications.

An Invisible Dermal Nanotattoo-Based Smart Wearable Sensor for eDiagnostics of Jaundice

Despite substantial progress in the diagnosis of jaundice/hyperbilirubinemia as the most common disease and cause of hospitalization of newborns, on the eve of Industry/Healthcare 5.0, the development of accurate and reliable wearable diagnostic sensors for noninvasive smart monitoring of bilirubin (BIL) is still in high demand. Aiming to fabricate a smart wearable sensor for early diagnosis of neonatal jaundice and its therapeutic monitoring, we here report a fluorescent dermal nanotattoo that further coupled with an IoT-integrated wearable optoelectronic reader for minimally invasive, continuous, and real-time monitoring of BIL in interstitial fluid. Selective recovery of quenched fluorescence of the dermal tattoo sensor, composed of biocompatible dissolving/hydrogel microneedles loaded with fluorescent carbon quantum dots, upon blue light exposure used for jaundice phototherapy was utilized for highly selective BIL sensing. The fascinating features of our developed smart wearable tattoo sensor and its successful results with high correlation with blood BIL results make it a highly promising sensor for easy, minimally invasive, reliable, and smart eDiagnostics and continuous therapeutic eMonitoring of jaundice and other BIL-induced diseases at the point of care. We envision that the developed nanotattoo sensing bioplatform will inspire the development of future smart tattoo sensors in various diagnostic and monitoring scenarios.

A hyaluronic acid-based dissolving microneedle patch loaded with 5-aminolevulinic acid for improved oral leukoplakia treatment

INTRODUCTION

A local microneedle patch loaded with 5-aminolevulinic acid (ALA) was constructed to improve the efficiency of ALA photodynamic treatment of oral leukoplakia, reduce local photosensitivity reactions, and promote the healing of lesions.

METHODS

The microneedle patch loaded with ALA was constructed with the hyaluronic acid (HA) solution (ALA-HAMN), and its morphology, strength, mucosal penetration, and biocompatibility were tested.

RESULTS

In vivo safety and permeability tests confirmed that ALA-HAMN had good biocompatibility and could penetrate the mucosal barrier and quickly dissolve and release ALA for in situ transdermal administration. The 4-nitroquinoline oxide (NQO) rat model experiment showed that ALA-HAMN can significantly improve photodynamic therapy (PDT) efficiency and has no damage to mucosal tissue compared with the commonly used ALA cotton ball dressing.

CONCLUSIONS

The ALA-loaded microneedle patch was successfully constructed for the photodynamic treatment of oral leukoplakia, and the photodynamic efficiency and comfort of oral leukoplakia were improved, which provided an effective delivery mode to improve clinical ALA-PDT treatment of oral leukoplakia (OLK).

Determination of vat-photopolymerization parameters for microneedles fabrication and characterization of HPMC/PVP K90 dissolving microneedles utilizing 3D-printed mold

Three-dimensional (3D) printing serves as an alternative method for fabricating microneedle (MN) patches with a high object resolution. In this investigation, four distinct needle shapes: pyramid mounted over a long cube (shape A), cone mounted over a cylinder (shape B), pyramidal shape (shape C), and conical shape (shape D) were designed using computer-aided design (CAD) software with compensated bases of 350, 450 and 550 µm. Polylactic acid (PLA) biophotopolymer resin from eSun and stereolithography (SLA) 3D printer from Anycubic technology were used to print MN patches. The 3D-printed MN patches were employed to construct MN molds, and those molds were used to produce hydroxypropyl methylcellulose (HPMC) and polyvinyl pyrrolidone (PVP) K90 dissolving microneedles (DMNs). Various printing parameters, such as curing time, printing angle, and anti-aliasing (AA), were varied to evaluate suitable printing conditions for each shape. Furthermore, physical appearance, mechanical property, and skin insertion ability of HPMC/PVP K90 DMNs were examined. The results showed that for shape A and C, the suitable curing time and printing angle were 1.5 s and 30° while for shapes B and D, they were 2.0 s and 45°, respectively. All four shapes required AA to eliminate their stair-stepped edges. Additionally, it was demonstrated that all twelve designs of 3D-printed MN patches could be employed for fabricating MN molds. HPMC/PVP K90 DMNs with the needles of shape A and B exhibited better physicochemical properties compared to those of shape C and D. Particularly, both sample 9 and 10 displayed sharp needle without bent tips, coupled with minimal height reduction (< 10%) and a high percentage of blue dots (approximately 100%). As a result, 3D printing can be utilized to custom construct 3D-printed MN patches for producing MN molds, and HPMC/PVP K90 DMNs manufactured by those molds showed excellent physicochemical properties.

Preconditioning Strategies for Improving the Outcome of Fat Grafting

Autologous fat grafting is a common procedure in plastic, reconstructive, and aesthetic surgery. However, it is frequently associated with an unpredictable resorption rate of the graft depending on the engraftment kinetics. This, in turn, is determined by the interaction of the grafted adipose tissue with the tissue at the recipient site. Accordingly, preconditioning strategies have been developed following the principle of exposing these tissues in the pretransplantation phase to stimuli inducing endogenous protective and regenerative cellular adaptations, such as the upregulation of stress-response genes or the release of cytokines and growth factors. As summarized in the present review, these stimuli include hypoxia, dietary restriction, local mechanical stress, heat, and exposure to fractional carbon dioxide laser. Preclinical studies show that they promote cell viability, adipogenesis, and angiogenesis, while reducing inflammation, fibrosis, and cyst formation, resulting in a higher survival rate and quality of fat grafts in different experimental settings. Hence, preconditioning represents a promising approach to improve the outcome of fat grafting in future clinical practice. For this purpose, it is necessary to establish standardized preconditioning protocols for specific clinical applications that are efficient, safe, and easy to implement into routine procedures.

Microneedles Based on a Biodegradable Polymer-Hyaluronic Acid

Transdermal transport can be challenging due to the difficulty in diffusing active substances through the outermost layer of the epidermis, as the primary function of the skin is to protect against the entry of exogenous compounds into the body. In addition, penetration of the epidermis for substances hydrophilic in nature and particles larger than 500 Da is highly limited due to the physiological properties and non-polar nature of its outermost layer, namely the stratum corneum. A solution to this problem can be the use of microneedles, which "bypass" the problematic epidermal layer by dispensing the active substance directly into the deeper layers of the skin. Microneedles can be obtained with various materials and come in different types. Of special interest are carriers based on biodegradable and biocompatible polymers, such as polysaccharides. Therefore, this paper reviews the latest literature on methods to obtain hyaluronic acid-based microneedles. It focuses on the current advancements in this field and consequently provides an opportunity to guide future research in this area.

Challenges in Optimizing Nanoplatforms Used for Local and Systemic Delivery in the Oral Cavity

In this study, we focused on innovative approaches to improve drug administration in oral pathology, especially by transmucosal and transdermal pathways. These improvements refer to the type of microneedles used (proposing needles in the saw), to the use of certain enhancers such as essential oils (which, besides the amplifier action, also have intrinsic actions on oral health), to associations of active substances with synergistic action, as well as the use of copolymeric membranes, cemented directly on the tooth. We also propose a review of the principles of release at the level of the oral mucosa and of the main release systems used in oral pathology. Controlled failure systems applicable in oral pathology include the following: fast dissolving films, mucoadhesive tablets, hydrogels, intraoral mucoadhesive films, composite wafers, and smart drugs. The novelty elements brought by this paper refer to the possibilities of optimizing the localized drug delivery system in osteoarthritis of the temporomandibular joint, neuropathic pain, oral cancer, periodontitis, and pericoronitis, as well as in maintaining oral health. We would like to mention the possibility of incorporating natural products into the controlled failure systems used in oral pathology, paying special attention to essential oils.

Fabrication Technology of Self-Dissolving Sodium Hyaluronate Gels Ultrafine Microneedles for Medical Applications with UV-Curing Gas-Permeable Mold

Microneedles are of great interest in diverse fields, including cosmetics, drug delivery systems, chromatography, and biological sensing for disease diagnosis. Self-dissolving ultrafine microneedles of pure sodium hyaluronate hydrogels were fabricated using a UV-curing TiO2-SiO2 gas-permeable mold polymerized by sol-gel hydrolysis reactions in nanoimprint lithography processes under refrigeration at 5 °C, where thermal decomposition of microneedle components can be avoided. The moldability, strength, and dissolution behavior of sodium hyaluronate hydrogels with different molecular weights were compared to evaluate the suitability of ultrafine microneedles with a bottom diameter of 40 μm and a height of 80 μm. The appropriate molecular weight range and formulation of pure sodium hyaluronate hydrogels were found to control the dissolution behavior of self-dissolving ultrafine microneedles while maintaining the moldability and strength of the microneedles. This fabrication technology of ultrafine microneedles expands their possibilities as a next-generation technique for bioactive gels for controlling the blood levels of drugs and avoiding pain during administration.