Hyaluronic acid based microneedle array: Recent applications in drug delivery and cosmetology

Battery-free optoelectronic patch for photodynamic and light therapies in treating bacteria-infected wounds

Light therapy is an effective approach for the treatment of a variety of challenging dermatological conditions. In contrast to existing methods involving high doses and large areas of illumination, alternative strategies based on wearable designs that utilize a low light dose over an extended period provide a precise and convenient treatment. In this study, we present a battery-free, skin-integrated optoelectronic patch that incorporates a coil-powered circuit, an array of microscale violet and red light emitting diodes (LEDs), and polymer microneedles (MNs) loaded with 5-aminolevulinic acid (5-ALA). These polymer MNs, based on the biodegradable composite materials of polyvinyl alcohol (PVA) and hyaluronic acid (HA), serve as light waveguides for optical access and a medium for drug release into deeper skin layers. Unlike conventional clinical photomedical appliances with a rigid and fixed light source, this flexible design allows for a conformable light source that can be applied directly to the skin. In animal models with bacterial-infected wounds, the experimental group with the combination treatment of metronomic photodynamic and light therapies reduced 2.48 log10 CFU mL-1 in bactericidal level compared to the control group, indicating an effective anti-infective response. Furthermore, post-treatment analysis revealed the activation of proregenerative genes in monocyte and macrophage cell populations, suggesting enhanced tissue regeneration, neovascularization, and dermal recovery. Overall, this optoelectronic patch design broadens the scope for targeting deep skin lesions, and provides an alternative with the functionality of standard clinical light therapy methods.

Simulated skin model for in vitro evaluation of insertion performance of microneedles: design, development, and application verification

Microneedles, as a new efficient and safe transdermal drug delivery technology, has a wide range of applications in drug delivery, vaccination, medical cosmetology, and diagnostics. The degree of microneedles penetration into the skin determines the reliability of the delivery dose, but its evaluation is not yet well-established, which is one of the major constraints in the commercialization of microneedles. In this paper, a novel visual simulated skin model was developed with reference to the physical properties of real skin. The simulated skin model was well-designed and its prescription was optimized to make the thickness, hardness, elasticity, and other parameters close to those of real skin. It not only meets the need to assess the degree of insertion of microneedles but also provides a visual observation of the insertion state of microneedles.

Curcumin analogue AC17-loaded dissolvable microneedles activate FOXO3 and enhance localized drug delivery for oral squamous cell carcinoma treatment

Curcumin, a polyphenol extracted from turmeric, is a potential alternative for the treatment of oral squamous cell carcinoma (OSCC) due to its remarkable anticancer activity and low systemic toxicity. To further enhance the anticancer activity and bioavailability of curcumin, we synthesized a curcumin analogue, AC17, by modifying the benzene ring and methylene group of curcumin. A soluble hyaluronic acid microneedle patch (AC17@HAMN) was developed to ensure accurate and safe delivery of AC17 to tumor tissues. The inhibitory effect of AC17 on OSCC cells was stronger than that of curcumin and some common analogues. Transcriptome sequencing showed that the target genes of AC17 were mainly concentrated in apoptosis, cell cycle and cell senescence pathways. Among them, AC17 induces cell cycle arrest and inhibits cell proliferation mainly by activating FOXO3 signaling. With good penetration and dissolution properties, microneedles can deliver AC17 directly to the tumor site and show good anti-tumor effect. Moreover, AC17@HAMN showed good biosafety. In summary, AC17@HAMN offers high efficiency, minimal invasiveness, and few adverse reactions. This microneedle patch holds great promise for potential clinical applications, especially for the treatment of OSCC.

Dissolving microneedles for transdermal drug delivery in cancer immunotherapy

Immunotherapy is an important approach in cancer treatment. Transdermal administration is emerging as a promising method for delivering immunotherapeutics. Dissolving microneedles are made mainly of soluble or biodegradable polymers and have garnered widespread attention due to their painlessness, safety, convenience, excellent drug loading capacity, and easy availability of various materials, making them an ideal transdermal delivery system. This review comprehensively summarized the preparation methods, materials, and applications of dissolving microneedles in cancer vaccines, immune checkpoint inhibitors, and adoptive cell therapy. Additionally, the challenges and perspectives associated with their future clinical translation are discussed.

Converting Short-Acting Insulin into Thermo-Stable Longer-Acting Insulin Using Multi-Layer Detachable Microneedles

The detachable dissolving microneedles (DDMNs) feature an array of needles capable of being separated from the base sheet during administration. Here they were fabricated to address delivery efficiency and storage stability of insulin. The constructed insulin-DDMN is multi-layered, with 1) a hard tip cover layer; 2) a layer of regular short-acting insulin (RI) mixed with hyaluronic acid (HA) and sorbitol (Sor) which occupies the taper tip region of the needles; 3) a barrier layer situated above the RI layer; and 4) a fast-dissolving layer connecting the barrier layer to the base sheet. RI entrapped in DDMNs exhibited enhanced thermal stability; it could be stored at 40 °C for 35 days without losing significant biological activity. Differential scanning calorimetric analysis revealed that the HA-Sor matrix could improve the denaturation temperature of the RI from lower than room temperature to 186 °C. Tests in ex vivo porcine skin demonstrated RI delivery efficiency of 91±1.59 %. Experiments with diabetic rats revealed sustained release of RI, i.e., when compared to subcutaneous injection with the same RI dose, RI-DDMNs produced slower absorption of insulin into blood circulation, delayed onset of hypoglycemic effect, longer serum insulin half-life, and longer hypoglycemic duration.

Dissolvable microneedles in the skin: Determination the impact of barrier disruption and dry skin on dissolution

Dissolvable microneedles (DMNs), fabricated from biocompatible materials that dissolve in both water and skin have gained popularity in dermatology. However, limited research exists on their application in compromised skin conditions. This study compares the hyaluronic acid-based DMNs penetration, formation of microchannels, dissolution, and diffusion kinetics in intact, barrier-disrupted (tape stripped), and dry (acetone-treated) porcine ear skin ex vivo. After DMNs application, comprehensive investigations including dermoscopy, stereomicroscope, skin hydration, transepidermal water loss (TEWL), optical coherence tomography (OCT), reflectance confocal laser scanning microscopy (RCLSM), confocal Raman micro-spectroscopy (CRM), two-photon tomography combined with fluorescence lifetime imaging (TPT-FLIM), histology, and scanning electron microscopy (SEM) were conducted. The 400 µm long DMNs successfully penetrated the skin to depths of ≈200 µm for dry skin and ≈200-290 µm for barrier-disrupted skin. Although DMNs fully inserted into all skin conditions, their dissolution rates were high in barrier-disrupted and low in dry skin, as observed through stereomicroscopy and TPT-FLIM. The dissolved polymer exhibited a more significant expansion in barrier-disrupted skin compared to intact skin, with the smallest increase observed in dry skin. Elevated TEWL and reduced skin hydration levels were evident in barrier-disrupted and dry skins compared to intact skin. OCT and RCLSM revealed noticeable skin indentation and pronounced microchannel areas, particularly in barrier-disrupted and dry skin. Additional confirmation of DMN effects on the skin and substance dissolution was obtained through histology, SEM, and CRM techniques. This study highlights the impact of skin condition on DMN effectiveness, emphasizing the importance of considering dissolvability and dissolution rates of needle materials, primarily composed of hyaluronic acid, for optimizing DMN-based drug delivery.

Self-assembled gel microneedle formed by MS deep eutectic solvent as a transdermal delivery system for hyperpigmentation treatment

Hyperpigmentation (HP) is an unfavorable skin disease that typically caused by injury, inflammation, or photoaging and leads to numerous physical and psychological issues in patients. Recently, development and application of natural whitening substances, particularly compound curcumin (CUR), is one of the most prevalent treatments for HP. However, it is still a formidable challenge to improve the percutaneous delivery of CUR due to its inadequate solubility in water and excellent barrier function of skin. To overcome the limitations of conventional delivery and increase the percutaneous absorption of CUR, the efficient delivery of CUR is urgently required. Herein, we developed a new malic acid-sorbitol deep eutectic solvent (MS/DES) gel microneedle loaded with CUR as a transdermal delivery system for HP treatment. The MS/DES gel produces three-dimensional (3D) network structure by self-assembly of hydrogen bond interactions, which conferred the CUR-MS/DES-GMN with sufficient mechanical properties to successfully penetrate skin tissue while also helping to enhance the drug's release rate. The CUR-MS/DES-GMN exhibit high biocompatibility and mechanical property in vivo of mice. The zebrafish experiments also show that CUR-MS/DES gel has significant effect of anti-pigmentation. Therefore, the designed CUR-MS/DES-GMN system provides a novel strategy for HP treatment based on self-assembly of naturally molecules.

Hyaluronic acid-oleylamine and chitosan-oleic acid conjugate-based hybrid nanoparticle delivery via. dissolving microneedles for enhanced treatment efficacy in localized breast cancer

Microneedle technology offers a minimally invasive treatment strategy to deliver chemotherapeutics to localized tumors. Amalgamating the surface functionalized nanoparticles with microneedle technology can potentially deliver drugs directly to tumors and subsequently target cancer cells via, overexpressed receptors on the cell surface, thereby enhancing the treatment efficacy while reducing side effects. Here, we report cetuximab anchored hyaluronic acid-oleylamine and chitosan-oleic acid-based hybrid nanoparticle (HA-OA/CS-OA NPT)-loaded dissolving microneedles (MN) for targeted delivery of cabazitaxel (CBT) in localized breast cancer tumor. The HA-OA/CS-OA NPT was characterized for their size, surface charge, morphology, physicochemical characteristics, drug release behavior, and in vitro anti-cancer efficacy. The HA-OA/CS-OA NPT were of ~125 nm size, showed enhanced cytotoxicity and cellular uptake, and elicited a superior apoptotic response against MDA-MB-231 cells. Subsequently, the morphology and physicochemical characteristics of HA-OA/CS-OA NPT-loaded MN were also evaluated. The fabricated microneedles were of ~550 μm height and showed loading of nanoparticles equivalent to ~250 μg of CBT. The ex vivo skin permeation study revealed fast dissolution of microneedles upon hydration, while the drug permeation across the skin exhibited ~4-fold improvement in comparison to free drug-loaded MN. In vivo studies performed on DMBA-induced breast cancer in female SD rats showed a marked reduction in tumor volume after administration of drug and nanoparticle-loaded microneedles in comparison to intravenous administration of free drug. However, the HA-OA/CS-OA NPT-MN showed the highest tumor reduction and survival rate, with the lowest body weight reduction in comparison to other treatment groups, indicating its superior efficacy and low systemic toxicity. Overall, the dissolving microneedle-mediated delivery of targeted nanoparticles loaded with chemotherapeutics offers a superior alternative to conventional intravenous chemotherapy.

Hyaluronic acid dissolving microneedle patch loaded with tranexamic acid for melasma treatment

Melasma is an acquired hypermelanotic condition characterized by the presence of irregular light-to-dark brown macules that primarily manifest on the sun-exposed areas of the skin, particularly the face. The management of melasma poses significant challenges, as it is often recalcitrant to treatment and tends to recur despite successful treatment. In this study, we explored a safe, easy, and effective melasma treatment strategy. A hyaluronic acid (HA)-based microneedle (MN) patch loaded with tranexamic acid (TXA) was designed to deliver the necessary medication for melasma treatment. The MN patch features uniform needles with adequate mechanical strength and effective penetration and solubility in the skin without cytotoxicity. Remarkably, these MNs substantially reduce the thickness of the epidermis of melasma mice, curtail melanin production, and diminish dopachrome tautomerase (DCT) expression.

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.

Rosacea treatment with mussel adhesive protein delivered via microneedling: In vivo and clinical studies

BACKGROUND

Rosacea is a prevalent chronic dermatological condition marked by facial inflammation and erythema, significantly compromising the quality of life for affected individuals. Current treatment methods for rosacea are not considered ideal because of the complex etiology of the disease. Mussel adhesive protein (MAP) is a glycoprotein derived from the foot gland of mussels. The protein exhibits anti-inflammatory properties, relieves skin itching, and promotes wound healing.

AIMS

We aimed to explore the feasibility of using MAP administered via microneedle delivery for treating rosacea and the potential molecular mechanism involved.

MATERIALS AND METHODS

The therapeutic effect and mechanism of MAP microneedle delivery in an LL-37-induced rosacea-like mouse model were observed using morphological and histological methods. Twenty-seven patients with erythematotelangiectatic rosacea (ETR) underwent treatment once every 1 month, with three treatments constituting one treatment course. The therapeutic effect was evaluated by comparing the clinical images taken at baseline, after the first treatment course, and after the second treatment course. The red value, CEA, and GFSS score were also calculated.

RESULTS

In response to the microneedle delivery of MAP, innate immunity, inflammatory infiltration, and abnormal neurovascular regulation improved significantly in rosacea-like mice. In the clinical experiments, the microneedle delivery of MAP significantly improved the symptoms of erythema, flushing, and telangiectasia in patients with ETR, and no obvious adverse reactions were observed.

CONCLUSIONS

MAP delivered by microneedling is effective and safe for treating ETR.

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.

Multienzyme-Like Nanozyme Encapsulated Ocular Microneedles for Keratitis Treatment

Keratitis, an inflammation of the cornea caused by bacterial or fungal infections, is one of the leading causes of severe visual disability and blindness. Keratitis treatment requires both the prevention of infection and the reduction of inflammation. However, owing to their limited therapeutic functions, in addition to the ocular barrier, existing conventional medications are characterized by poor efficacy and low bioavailability, requiring high dosages or frequent topical treatment, which represents a burden on patients and increases the risk of side effects. In this study, manganese oxide nanocluster-decorated graphdiyne nanosheets (MnOx/GDY) are developed as multienzyme-like nanozymes for the treatment of infectious keratitis and loaded into hyaluronic acid and polymethyl methacrylate-based ocular microneedles (MGMN). MGMN not only exhibits antimicrobial and anti-inflammatory effects owing to its multienzyme-like activities, including oxidase, peroxidase, catalase, and superoxide dismutase mimics but also crosses the ocular barrier and shows increased bioavailability via the microneedle system. Moreover, MGMN is demonstrated to eliminate pathogens, prevent biofilm formation, reduce inflammation, alleviate ocular hypoxia, and promote the repair of corneal epithelial damage in in vitro, ex vivo, and in vivo experiments, thus providing a better therapeutic effect than commercial ophthalmic voriconazole, with no obvious microbial resistance or cytotoxicity.

Dissolving Hyaluronic Acid-Based Microneedles to Transdermally Deliver Eugenol Combined with Photothermal Therapy for Acne Vulgaris Treatment

A microneedle transdermal drug delivery system simultaneously avoids systemic toxicity of oral administration and low efficiency of traditional transdermal administration, which is of great significance for acne vulgaris therapy. Herein, eugenol-loaded hyaluronic acid-based dissolving microneedles (E@P-EO-HA MNs) with antibacterial and anti-inflammatory activities are developed for acne vulgaris therapy via eugenol transdermal delivery integrated with photothermal therapy. E@P-EO-HA MNs are pyramid-shaped with a sharp tip and a hollow cavity structure, which possess sufficient mechanical strength to penetrate the stratum corneum of the skin and achieve transdermal delivery, in addition to excellent in vivo biocompatibility. Significantly, E@P-EO-HA MNs show effective photothermal therapy to destroy sebaceous glands and achieve antibacterial activity against deep-seated Propionibacterium acnes (P. acnes) under near-infrared-light irradiation. Moreover, cavity-loaded eugenol is released from rapidly dissolved microneedle bodies to play a sustained antibacterial and anti-inflammatory therapy on the P. acnes infectious wound. E@P-EO-HA MNs based on a synergistic therapeutic strategy combining photothermal therapy and eugenol transdermal administration can significantly alleviate inflammatory response and ultimately facilitate the repair of acne vulgaris. Overall, E@P-EO-HA MNs are expected to be clinically applied as a functional minimally invasive transdermal delivery strategy for superficial skin diseases therapy in skin tissue engineering.

Microneedle Delivery Platform Integrated with Codelivery Nanoliposomes for Effective and Safe Androgenetic Alopecia Treatment

Although topical application of minoxidil is a widely used, FDA-approved therapy for androgenetic alopecia (AGA) treatment, it suffers from low bioavailability, the requirement for frequent long-term use, and side effects. With a similar structure as minoxidil, kopexil and kopyrrol are less toxic and have been commercialized, but show an inferior hair regeneration effect compared to minoxidil. Herein, we developed a hyaluronic acid (HA)-based dissolvable microneedles (MNs) delivery platform integrated with kopexil and kopyrrol coencapsulated nanoliposomes (KK-NLPs) to effectively and safely treat AGA. Facilitated by nanoliposomes and MNs, the encapsulated KK-NLPs performed efficient skin penetration and enhanced cellular internalization into human dermal papilla cells. Furthermore, within the target cells, the codelivered kopexil and kopyrrol show synergistic effects by orchestrating an upregulation in the expression of Ki67, β-catenin, vascular endothelial growth factor (VEGF), and CD31. These molecular responses collectively foster cell proliferation, migration, and antioxidative effects, thereby facilitating the expedited progression of hair follicles (HFs) into the anagen phase and promoting peripheral angiogenesis. Notably, the KK-NLPs-integrated MNs treatment group exhibits noteworthy enhanced hair regeneration in vivo, with identical or superior therapeutic effects at a much lower dosage than that of minoxidil. These results suggest the great potential of this kopexil and kopyrrol codelivery nanoliposomes-integrated MNs platform for AGA treatment in a safe and efficient way.

Marine polysaccharides: Biological activities and applications in drug delivery systems

The ocean is the common home of a large number of marine organisms, including plants, animals, and microorganisms. Researchers can extract thousands of important bioactive components from the oceans and use them extensively to treat and prevent diseases. In contrast, marine polysaccharide macromolecules such as alginate, carrageenan, Laminarin, fucoidan, chitosan, and hyaluronic acid have excellent physicochemical properties, good biocompatibility, and high bioactivity, which ensures their wide applications and strong therapeutic potentials in drug delivery. Drug delivery systems (DDS) based on marine polysaccharides and modified marine polysaccharide molecules have emerged as an innovative technology for controlling drug distribution on temporal, spatial, and dosage scales. They can detect and respond to external stimuli such as pH, temperature, and electric fields. These properties have led to their wide application in the design of novel drug delivery systems such as hydrogels, polymeric micelles, liposomes, microneedles, microspheres, etc. In addition, marine polysaccharide-based DDS not only have smart response properties but also can combine with the unique biological properties of the marine polysaccharide base to exert synergistic therapeutic effects. The biological activities of marine polysaccharides and the design of marine polysaccharide-based DDS are reviewed. Marine polysaccharide-based responsive DDS are expected to provide new strategies and solutions for disease treatment.

Recent progress on the development of bioinspired surfaces with high aspect ratio microarray structures: From fabrication to applications

Surfaces with high aspect ratio microarray structures can implement sophisticated assignment in typical fields including microfluidics, sensor, biomedicine, et al. via regulating their deformation or the material properties. Inspired by natural materials and systems, for example sea cockroaches, water spiders, cacti, lotus leaves, rice leaves, and cedar leaves, many researchers have focused on microneedle functional surface studies. When the surface with high aspect ratio microarray structures is stimulated by the external fields, such as optical, electric, thermal, magnetic, the high aspect ratio microarray structures can undergo hydrophilic and hydrophobic switching or shape change, which may be gifted the surfaces with the ability to perform complex task, including directional liquid/air transport, targeted drug delivery, microfluidic chip sensing. In this review, the fabrication principles of various surfaces with high aspect ratio microarray structures are classified and summarized. Mechanisms of liquid manipulation on hydrophilic/hydrophobic surfaces with high aspect ratio microarray structures are clarified based on Wenzel model, Cassie model, Laplace pressure theories and so on. Then the intelligent control strategies have been demonstrated. The applications in microfluidic, drug delivery, patch sensors have been discussed. Finally, current challenges and new insights of future prospects for dynamic manipulation of liquid/air based on biomimetic surface with high aspect ratio microarray structures are also addressed.

Egg microneedles for transdermal vaccination of inactivated influenza virus

The use of dissolving microneedles (DMNs) is a drug delivery technique in which drug dissolution occurs once it is administered into the skin. The skin is a remarkable site for vaccination due to its significant immunologic properties. Compared to the traditional hypodermic intramuscular (IM) injection, vaccination via DMN does not require cold chains and allows for minimal invasive drug delivery. On account of the significance of skin vaccination, preceding studies have been conducted to elucidate the importance of the DMN technology in vaccination. Most of these studies focused on formulations that maintain the activity of the vaccine, so formulations designed to be specific to the mechanical properties of the microneedle could not be used together independently. In this study, we have developed influenza vaccine loaded egg microneedles (EMN) and characterized the specificity of layer-specific functions of EMN by distinguishing between formulations that can maintain the activity of the vaccine and have the mechanical strength. By the use of in vitro tests such as ELISA and SRID assays, we quantitively evaluated the antigen activity of the formulation candidates to be 87% and 91%, respectively. In vivo tests were also conducted as mouse groups were inoculated with the formulation constructed into egg microneedles (FLU-EMN) to determine the protective efficacy against infection. The results demonstrated that FLU-EMN with functionalized formulations successfully enabled protective immune response even with a fractional dose compared to IM injection.

MiR-141-3p-Functionalized Exosomes Loaded in Dissolvable Microneedle Arrays for Hypertrophic Scar Treatment

Hypertrophic scar (HS) is a common fibroproliferative disease caused by abnormal wound healing after deep skin injury. However, the existing approaches have unsatisfactory therapeutic effects, which promote the exploration of newer and more effective strategies. MiRNA-modified functional exosomes delivered by dissolvable microneedle arrays (DMNAs) are expected to provide new hope for HS treatment. In this study, a miRNA, miR-141-3p, which is downregulated in skin scar tissues and in hypertrophic scar fibroblasts (HSFs), is identified. MiR-141-3p mimics inhibit the proliferation, migration, and myofibroblast transdifferentiation of HSFs in vitro by targeting TGF-β2 to suppress the TGF-β2/Smad pathway. Subsequently, the engineered exosomes encapsulating miR-141-3p (miR-141-3pOE -Exos) are isolated from adipose-derived mesenchymal stem cells transfected with Lv-miR-141-3p. MiR-141-3pOE -Exos show the same inhibitive effects as miR-141-3p mimics on the pathological behaviors of HSFs in vitro. The DMNAs for sustained release of miR-141-3pOE -Exos are further fabricated in vivo. MiR-141OE -Exos@DMNAs effectively decrease the thickness of HS and improve fibroblast distribution and collagen fiber arrangement, and downregulate the expression of α-SMA, COL-1, FN, TGF-β2, and p-Smad2/3 in the HS tissue. Overall, a promising, effective, and convenient exosome@DMNA-based miRNA delivery strategy for HS treatment is provided.

Potential strategy of microneedle-based transdermal drug delivery system for effective management of skin-related immune disorders

Skin-related immune disorders are a category of diseases that lead to the dysregulation of the body's immune response due to imbalanced immune regulation. These disorders exhibit diverse clinical manifestations and complicated pathogenesis. The long-term use of corticosteroids, anti-inflammatory drugs, and immunosuppressants as traditional treatment methods for skin-related immune disorders frequently leads to adverse reactions in patients. In addition, the effect of external preparations is not ideal in some cases due to the compacted barrier function of the stratum corneum (SC). Microneedles (MNs) are novel transdermal drug delivery systems that have theapparent advantages ofpenetrating the skin barrier, such as long-term and controlled drug delivery, less systemic exposure, and painless and minimally invasive targeted delivery. These advantages make it a good candidate formulation for the treatment of skin-related immune disorders and a hotspot for research in this field. This paper updates the classification, preparation, evaluation strategies, materials, and related applications of five types of MNs. Specific information, including the mechanical properties, dimensions, stability, and in vitro and in vivo evaluations of MNs in the treatment of skin-related immune disorders, is also discussed. This review provides an overview of the advances and applications of MNs in the effective treatment of skin-related immune disorders and their emerging trends.

The Chimera of TPGS and Nanoscale Lipid Carriers as Lymphatic Drug Delivery Vehicles to Fight Metastatic Cancers

The lymphatic system (LS) plays a crucial role in fluid balance, transportation of macromolecules, and immune response. Moreover, LS is a channel for microbial invasion and cancer metastasis. Particularly, solid tumors, including lung, breast, melanoma, and prostate cancers, are metastasized across highways of LS. Subsequently, the fabrication of chimeric lymphatic drug delivery systems (LDDS) is a promising strategy to fight cancer metastasis and control microbial pandemics. In this regard, LDDS, in terms of PEG-nanoscaled lipid carriers, elicited a revolution during the COVID-19 pandemic as cargoes for mRNA vaccines. The drug delivered by the lymphatic pathway escapes first-pass metabolism and enhances the drug's bioavailability. Ample approaches, including synthesis of prodrugs, trigging of chylomicron biosynthesis, and fabrication of nanocarriers, facilitate lymphatic drug delivery. Specifically, nanoscales lipid cargoes have the propensity to lymphatic trafficking. Interestingly, TPGSengineered nanoscale lipid cargoes enhance lymphatic trafficking, increase tissue permeation, and, specifically, uptake. Moreover, they overcome biological barriers, control biodistribution, and enhance organelles localization. Most anticancer agents are non-specific, have low bioavailability, and induced drug resistance. Therefore, TPGS-engineered nanoscale lipid chimeras improve the therapeutic impact of anticancer agents. This review highlights lymphatic cancer metastasis, nanoscales lipid cargoes as LDDS, and their influence on lymphatic trafficking, besides the methods of LDD studies.

Advances in Formulations of Microneedle System for Rheumatoid Arthritis Treatment

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic joint inflammation, eventually leading to severe disability and premature death. At present, the treatment of RA is mainly to reduce inflammation, swelling, and pain. Commonly used drugs are non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, and disease-modifying anti-rheumatic drugs (DMARDs). These drugs lack specificity and require long-term, high-dose administration, which can cause serious adverse effects. In addition, the oral, intravenous, and intra-articular injections will reduce patient compliance, resulting in high cost and low bioavailability. Due to these limitations, microneedles (MNs) have emerged as a new strategy to efficiently localize the drugs in inflamed joints for the treatment of RA. MNs can overcome the cuticle barrier of the skin without stimulating nerves and blood vessels. Which can increase patient compliance, improve bioavailability, and avoid systemic circulation. This review summarizes and evaluates the application of MNs in RA, especially dissolving MNs (DMNs). We encourage the use of MNs to treat RA, by describing the general properties of MNs, materials, preparation technology, drug release mechanism, and advantages. Furthermore, we discussed the biological safety, development prospects, and future challenges of MNs, hoping to provide a new strategy for the treatment of RA.

Botulinum toxin A dissolving microneedles for hyperhidrosis treatment: design, formulation and in vivo evaluation

Multiple periodic injections of botulinum toxin A (BTX-A) are the standard treatment of hyperhidrosis which causes excessive sweating. However, BTX-A injections can create problems, including incorrect and painful injections, the risk of drug entry into the bloodstream, the need for medical expertise, and waste disposal problems. New drug delivery systems can substantially reduce these problems. Transdermal delivery is an effective alternative to conventional BTX-A injections. However, BTX-A's large molecular size and susceptibility to degradation complicate transdermal delivery. Dissolving microneedle patches (DMNPs) encapsulated with BTX-A (BTX-A/DMNPs) are a promising solution that can penetrate the dermis painlessly and provide localized translocation of BTX-A. In this study, using high-precision 3D laser lithography and subsequent molding, DMNPs were prepared based on a combination of biocompatible polyvinylpyrrolidone and hyaluronic acid polymers to deliver BTX-A with ultra-sharp needle tips of 1.5 ± 0.5 µm. Mechanical, morphological and histological assessments of the prepared DMNPs were performed to optimize their physicochemical properties. Furthermore, the BTX-A release and diffusion kinetics across the skin layers were investigated. A COMSOL simulation was conducted to study the diffusion process. The primary stability analysis reported significant stability for three months. Finally, the functionality of the BTX-A/DMNPs for the suppression of sweat glands was confirmed on the hyperhidrosis mouse footpad, which drastically reduced sweat gland activity. The results demonstrate that these engineered DMNPs can be an effective, painless, inexpensive alternative to hypodermic injections when treating hyperhidrosis.

A Rapidly Dissolvable Microneedle Patch with Tip-Accumulated Antigens for Efficient Transdermal Vaccination

Dissolvable microneedles (DMNs) are an attractive alternative for vaccine delivery due to their user-friendly, skin-targeted, and minimally invasive features. However, vaccine waste and inaccurate dosage remain significant issues faced by DMNs, as the skin's elasticity makes it difficult to insert MNs completely. Here, a simple and reliable fabrication method are introduced based on two-casting micromolding with centrifugal drying to create a rapidly DMN patch made of hyaluronic acid. Ovalbumin (OVA), as the model antigens, is concentrated in the tip parts of the DMNs (60% of the needle height) to prevent antigen waste caused by skin elasticity. The time and temperature of the initial centrifugal drying significantly affect antigen distribution within the needle tips, with lower temperature facilitating antigen accumulation. The resulting DMN patch is able to penetrate the skin with enough mechanical strength and quickly release antigens into the skin tissue within 3 min. The in vivo study demonstrates that immunization of OVA with DMNs outperforms conventional vaccination routes, including subcutaneous and intramuscular injections, in eliciting both humoral and cellular immunity. This biocompatible DMN patch offers a promising and effective strategy for efficient and safe vaccination.

Development of hyaluronic acid-silica composites via in situ precipitation for improved penetration efficiency in fast-dissolving microneedle systems

Fast-dissolving microneedles (DMNs) hold significant promise for transdermal drug delivery, offering improved patient compliance, biocompatibility, and functional adaptability for various therapeutic purposes. However, the mechanical strength of the biodegradable polymers used in DMNs often proves insufficient for effective penetration into human skin, especially under high humidity conditions. While many composite strategies have been developed to reinforce polymer-based DMNs, simple mixing of the reinforcements with polymers often results in ineffective penetration due to inhomogeneous dispersion of the reinforcements and the formation of undesired micropores. In response to this challenge, this study aimed to enhance the mechanical performance of hyaluronic acid (HA)-based microneedles (MNs), one of the most commonly used DMN systems. We introduced in situ precipitation of silica nanoparticles (Si) into the HA matrix in conjunction with conventional micromolding. The precipitated silica nanoparticles were uniformly distributed, forming an interconnected network within the HA matrix. Experimental results demonstrated that the mechanical properties of the HA-Si composite MNs with up to 20 vol% Si significantly improved, leading to higher penetration efficiency compared to pure HA MNs, while maintaining structural integrity without any critical defects. The composite MNs also showed reduced degradation rates and preserved their drug delivery capabilities and biocompatibility. Thus, the developed HA-Si composite MNs present a promising solution for efficient transdermal drug delivery and address the mechanical limitations inherent in DMN systems. STATEMENT OF SIGNIFICANCE: HA-Si composite dissolving microneedle (DMN) systems were successfully fabricated through in situ precipitation and conventional micromolding processes. The precipitated silica nanoparticles formed an interconnected network within the HA matrix, ranging in size from 25 to 230 nm. The optimal silica content for HA-Si composite MN systems should be up to 20 % by volume to maintain structural integrity and mechanical properties. HA-Si composite MNs with up to 20 % Si showed improved penetration efficiency and reduced degradation rates compared to pure HA MNs, thereby expanding the operational window. The HA-Si composite MNs retained good drug delivery capabilities and biocompatibility.

Advanced Silk Fibroin Biomaterials-Based Microneedles for Healthcare

Microneedles are a promising transdermal drug delivery system that has the advantages of minimal invasiveness, painlessness, and on-demand drug delivery compared with commonly used medical techniques. Natural resources are developed as next-generation materials for microneedles with varying degrees of success. Among them, silk fibroin is a natural polymer obtained from silkworms with good biocompatibility, high hardness, and controllable biodegradability. These properties provide many opportunities for integrating silk fibroin with implantable microneedle systems. In this review, the research progress of silk fibroin microneedles in recent years is summarized, including their materials, processing technology, detection, drug release methods, and applications. Besides, the research and development of silk fibroin in a multidimensional way are analyzed. Finally, it is expected that silk fibroin microneedles will have excellent development prospects in various fields.

Combination therapy using multifunctional dissolvable hyaluronic acid microneedles for oral ulcers

Oral ulcers are common in the oral mucosa. Frequent occurrences of oral ulcers commonly afflict patients, seriously impacting their daily life. Treatments with good anti-inflammatory and antibacterial properties are important for promoting the healing of oral ulcers. In this study, a multifunctional, soluble hyaluronic acid (HA) microneedle (MN) patch was prepared to promote oral ulcer healing. The tip layer of the MN patch was loaded with triamcinolone acetonide (TA) and epidermal growth factor (EGF) to inhibit inflammation and promote angiogenesis. Zeolitic imidazolate framework-8 (ZIF-8) was loaded onto the base layer of the MN patch, which effectively released Zn2+ to mediate antibacterial effects. In addition, HA exerts a protective effect on the mucous membrane. Owing to these properties, the multifunctional MN patches were found to have good anti-inflammatory, antibacterial, and tissue-healing abilities, indicating that the multifunctional MN patch design successfully promoted the healing of oral ulcers.

Dissolving and Swelling Hydrogel-Based Microneedles: An Overview of Their Materials, Fabrication, Characterization Methods, and Challenges

Polymeric hydrogels are a complex class of materials with one common feature-the ability to form three-dimensional networks capable of imbibing large amounts of water or biological fluids without being dissolved, acting as self-sustained containers for various purposes, including pharmaceutical and biomedical applications. Transdermal pharmaceutical microneedles are a pain-free drug delivery system that continues on the path to widespread adoption-regulatory guidelines are on the horizon, and investments in the field continue to grow annually. Recently, hydrogels have generated interest in the field of transdermal microneedles due to their tunable properties, allowing them to be exploited as delivery systems and extraction tools. As hydrogel microneedles are a new emerging technology, their fabrication faces various challenges that must be resolved for them to redeem themselves as a viable pharmaceutical option. This article discusses hydrogel microneedles from a material perspective, regardless of their mechanism of action. It cites the recent advances in their formulation, presents relevant fabrication and characterization methods, and discusses manufacturing and regulatory challenges facing these emerging technologies before their approval.

Recent Trends in Macromolecule-Based Approaches for Hair Loss Treatment

Macromolecules are large, complex molecules composed of smaller subunits known as monomers. The four primary categories of macromolecules found in living organisms are carbohydrates, lipids, proteins, and nucleic acids; they also encompass a broad range of natural and synthetic polymers. Recent studies have shown that biologically active macromolecules can help regenerate hair, providing a potential solution for current hair regeneration therapies. This review examines the latest developments in the use of macromolecules for the treatment of hair loss. The fundamental principles of hair follicle (HF) morphogenesis, hair shaft (HS) development, hair cycle regulation, and alopecia have been introduced. Microneedle (MN) and nanoparticle (NP) delivery systems are innovative treatments for hair loss. Additionally, the application of macromolecule-based tissue-engineered scaffolds for the in vitro and in vivo neogenesis of HFs is discussed. Furthermore, a new research direction is explored wherein artificial skin platforms are adopted as a promising screening method for hair loss treatment drugs. Through these multifaceted approaches, promising aspects of macromolecules for future hair loss treatments are identified.

Modern microelectronics and microfluidics on microneedles

Possessing the attractive advantages of moderate invasiveness and high compliance, there is no doubt that microneedles (MNs) have been a gradually rising star in the field of medicine. Recent evidence implies that microelectronics technology based on microcircuits, microelectrodes and other microelectronic elements combined with MNs can realize mild electrical stimulation, drug release and various types of electrical sensing detection. In addition, the combination of microfluidics technology and MNs makes it possible to transport fluid drugs and access a small quantity of body fluids which have shown significant untapped potential for a wide range of diagnostics. Of particular note is that combining both technologies and MNs is more difficult, but is promising to build a modern healthcare platform with more comprehensive functions. This review introduces the properties of MNs that can form integrated systems with microelectronics and microfluidics, and summarizes these systems and their applications. Furthermore, the future challenges and perspectives of the integrated systems are conclusively proposed.

Polysaccharide-Based Coatings as Drug Delivery Systems

Therapeutic polysaccharide-based coatings have recently emerged as versatile strategies to transform a conventional medical implant into a drug delivery system. However, the translation of these polysaccharide-based coatings into the clinic as drug delivery systems still requires a deeper understanding of their drug degradation/release profiles. This claim is supported by little or no data. In this review paper, a comprehensive description of the benefits and challenges generated by the polysaccharide-based coatings is provided. Moreover, the latest advances made towards the application of the most important representative coatings based on polysaccharide types for drug delivery are debated. Furthermore, suggestions/recommendations for future research to speed up the transition of polysaccharide-based drug delivery systems from the laboratory testing to clinical applications are given.

Clinical Development and Evaluation of a Multi-Component Dissolving Microneedle Patch for Skin Pigmentation Disorders

Excessive melanin deposition in the skin leads to various skin pigmentation diseases, such as chloasma and age spots. The deposition is induced by several factors, including tyrosinase activities and ultraviolet-induced oxidative stress. Herein, we propose a multi-component, multi-pathway drug combination, with glabridin, 3-O-ethyl-L-ascorbic acid, and tranexamic acid employed as, respectively, a tyrosinase inhibitor, an antioxidant, and a melanin transmission inhibitor. Considering the poor skin permeability associated with topical application, dissolving microneedles (MNs) prepared with hyaluronic acid/poly(vinyl alcohol)/poly(vinylpyrrolidone) were developed to load the drug combination. The drug-loaded microneedles (DMNs) presented outstanding skin insertion, dissolution, and drug delivery properties. In vitro experiments confirmed that DMNs loaded with active ingredients had significant antioxidant and inhibitory effects on tyrosinase activity. Furthermore, the production of melanin both in melanoma cells (B16-F10) and in zebrafish was directly reduced after using DMNs. Clinical studies demonstrated the DMNs' safety and showed that they have the ability to effectively reduce chloasma and age spots. This study indicated that a complex DMN based on a multifunctional combination is a valuable depigmentation product worthy of clinical application.

Efficient production of hyaluronic acid by Streptococcus zooepidemicus using two-stage semi-continuous fermentation

Hyaluronic acid is a kind of mucopolysaccharide that has wide applications in cosmetics, health food, and orthopedics. Using Streptococcus zooepidemicus ATCC 39920 as parent, a beneficial mutant SZ07 was obtained by UV mutagenesis, giving 1.42 g/L hyaluronic acid in shake flasks. To enhance the efficiency of hyaluronic acid production, a semi-continuous fermentation process consisted of two-stage 3-L bioreactors was developed, in which 1.01 g/L/h productivity and 14.60 g/L hyaluronic acid were obtained. To further enhance the titer of hyaluronic acid, recombinant hyaluronidase SzHYal was added into 2^nd stage bioreactor at 6 h to reduce the viscosity of broth. The highest hyaluronic acid titer of 29.38 g/L was achieved with a productivity of 1.13 g/L/h at 300 U/L SzHYal after 24 h. This newly developed semi-continuous fermentation process provides a promising strategy for the industrial production of hyaluronic acid and related polysaccharides.

Co-Delivery of Loxoprofen and Tofacitinib by Photothermal Microneedles for Rheumatoid Arthritis Treatment

Rheumatoid arthritis (RA) is an autoimmune disease of synovial inflammation that affects populations worldwide. Transdermal drug delivery systems for treating RA have increased but remain challenging. We fabricated a dissolving microneedle (MN) system with photothermal (PT) polydopamine (PDA) to co-load the non-steroidal anti-inflammatory drug loxoprofen (Lox) and the Janus kinase inhibitor tofacitinib (Tof), with the aim of co-delivering Lox and Tof directly to the articular cavity, aided by the combination of MN and PT. In vitro and in vivo permeation studies showed that the PT MN significantly promoted drug permeation and retention in the skin. An in vivo visualization of the drug distribution in the articular cavity showed that the PT MN significantly promoted drug retention in the articular cavity. Importantly, compared to the intra-articular injection of Lox and Tof, the application of the PT MN to a carrageenan/kaolin-induced arthritis rat model exhibited superior performance in reducing joint swelling, muscle atrophy, and cartilage destruction. Furthermore, the PT MN downregulated the mRNA expression levels of proinflammatory cytokines, including TNF-α, IL-1β, iNOS, JAK2, JAK3, and STAT3. The results show that the PT MN transdermal co-delivery of Lox and Tof is a new synergetic therapy with high compliance and good therapeutic efficacy for RA.

Microneedle patches containing mesoporous polydopamine nanoparticles loaded with triamcinolone acetonide for the treatment of oral mucositis

Oral mucositis (OM) is the most common disease of the oral mucosa, which affects people's daily production and life. Triamcinolone ointment is the common clinical drug for OM treatment. However, the hydrophobic properties of triamcinolone acetonide (TA) and the complex microenvironment of the oral cavity led to its low bioavailability and unstable therapeutic effects on ulcer wounds. Herein, dissolving microneedle patches (MNs) composed of mesoporous polydopamine nanoparticles (MPDA) loaded with TA (TA@MPDA), sodium hyaluronic acid (HA), and Bletilla striata polysaccharide (BSP) are prepared as the transmucosal delivery system. The prepared TA@MPDA-HA/BSP MNs exhibit well-arranged microarrays, high mechanical strength and fast solubility (<3 min) properties. In addition, the hybrid structure improves the biocompatibility of TA@MPDA and expedites oral ulcer healing in the SD rat model through the synergistic anti-inflammatory and pro-healing effects of microneedle ingredients (hormones, MPDA and Chinese herbs extracts), with 90% less amount of TA compared with Ning Zhi Zhu^®. TA@MPDA-HA/BSP MNs are shown to be their great potential as novel ulcer dressings for OM management.

Microneedles: structure, classification, and application in oral cancer theranostics

Oral cancer is a malignant tumor that threatens the health of individuals on a global scale. Currently available clinical treatment methods, including surgery, radiotherapy, and chemotherapy, significantly impact the quality of life of patients with systemic side effects. In the treatment of oral cancer, local and efficient delivery of antineoplastic drugs or other substances (like photosensitizers) to improve the therapy effect is a potential way to optimize oral cancer treatments. As an emerging drug delivery system in recent years, microneedles (MNs) can be used for local drug delivery, offering the advantages of high efficiency, convenience, and noninvasiveness. This review briefly introduces the structures and characteristics of various types of MNs and summarizes MN preparation methods. An overview of the current research application of MNs in different cancer treatments is provided. Overall, MNs, as a means of transporting substances, demonstrate great potential in oral cancer treatments, and their promising future applications and perspectives of MNs are outlined in this review.

Sustained Release Microneedles: Materials and Applications in Facial Rejuvenation

Wrinkled and loose skin resulting from collagen degradation along with fibers decreasing reflects the youth diminishing. Microneedles (MNs) have opened up new avenues for the development of painless and noninvasive transdermal drug delivery systems for facial rejuvenation. Encapsulated drugs or molecules are transmitted to targeted tissues via percutaneous microchannels, which eliminate potential gastric stimulation or first-pass metabolic effects, as well as boost patient compliance. Although MNs are considered effective and feasible therapeutic alternatives to metals, silicon, and polymers, traditional procedures with reduction processes continue to encounter methodological limitations. In recent years, promising additive manufacturing processes such as three-dimensional printing and two-photon polymerization manufacturing have been developed with the aim of overcoming the limitations by traditional processes to facilitate an efficient and economic production mode. This review summarizes the design, material selection, and manufacturing method for recently advanced MN systems. Furthermore, we also highlight specific polymeric or natural microneedle products, like hyaluronan, plant derivates, and vitamins, for esthetic applications in this review. Impact Statement In this review, the materials and manufactural routes of microneedles (MNs) are detailed. Moreover, similar to the diagnostic or therapeutic MNs, the feature of dispensation with training and ready-to-use is perfect for beautification and anti-aging, which necessitate repeated and long-term usage. Furthermore, the specific polymeric or natural products for esthetic applications of MNs are highlighted in this review.

Topical Delivery of ROS-Responsive Methotrexate Prodrug Nanoassemblies by a Dissolvable Microneedle Patch for Psoriasis Therapy

Purpose

Oxidative stress, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and adenosine signaling are factors associated with psoriatic inflammation. Topical delivery of methotrexate (MTX) has become an option to overcome the side effects caused by systemic therapy in psoriasis, leading to the suppression of NF-κB activation through boosting adenosine release. However, thickened psoriatic skin is the primary restriction against local drug delivery.

Methods

In this study, a ROS responsive MTX prodrug (MTX-TK-HA) was synthesized with the feature of CD44 mediated active targeting to hyperproliferative keratinocytes. MTX prodrug and PLA-mPEG were formulated by nano-precipitation method to develop the MTX-TK-HA/PLA-mPEG nanoassemblies. To achieve painless transdermal delivery, a dissolving microneedle was applied for direct loading of these nanoassemblies by micromolding technique. The particle size, zeta potential, ROS-responsiveness, permeability, and mechanical strength of nanoassemblies and microneedle arrays were determined, respectively. Then, MTT assay, immunoblot analysis, ELISA assay, flow cytometry, and histological staining were utilized to thoroughly evaluate the efficacy of nanoassemblies-loaded microneedles in an imiquimod-induced psoriatic mouse model.

Results

Nanoassemblies-loaded microneedle arrays were capable of significantly penetrating imiquimod-induced psoriatic epidermis in mice. The efficient topical delivery of these nanoassemblies was achieved by potent mechanical strength and hyaluronic acid as the dissolvable matrix for microneedle arrays. CD44-mediated endocytosis enabled the intracellular uptake of nanoassemblies in keratinocytes, and methotrexate was released from MTX-TK-HA with ROS stimuli, followed by suppressing the proliferation of epidermal cells via NF-κB pathway blockade.

Conclusion

In a psoriatic mouse model, nanoassemblies loaded microneedle arrays relieve inflammatory skin disorders via regulation of adenosine and NF-κB signaling. Our study offered a rational design for the transdermal delivery of hydrophobic agents and defined an effective therapeutic option for psoriasis treatment.

Novel Microneedle Patch-Based Surface-Enhanced Raman Spectroscopy Sensor for the Detection of Pesticide Residues

Pesticide residues are a global threat to human health, and conventional sensors fail to simultaneously detect pesticide residues on the surface and inside agricultural products. In this work, we present a new microneedle (MN) patch-based surface-enhanced Raman spectroscopy (SERS) sensor. The needles and the basement of MNs can simultaneously detect pesticide residues on the surface and inside agricultural products. The Ag nanoparticles and sodium hyaluronate/poly(vinyl alcohol) (HA/PVA) hydrogel used in this MN patch-based sensor efficiently amplify the Raman signals of the pesticide residues. In addition, the HA/PVA hydrogel can effectively and quickly collect the residues, allowing this sensor to detect pesticide residues more conveniently. Furthermore, the stepped structure of the MNs increases the sensor's surface area. Experimental results show that the sensor can detect thiram and thiabendazole (TBZ) pesticide residues with detection limits of 10^-7 and 10^-8 M, respectively. The detection process is minimally invasive and not harmful to agricultural products. The application of this MN patch-based SERS sensor can be extended to the safety and health monitoring of other plants and animals.

Enhancing Intradermal Delivery of Lidocaine by Dissolving Microneedles: Comparison between Hyaluronic Acid and Poly(Vinyl Pyrrolidone) Backbone Polymers

Lidocaine hydrochloride (LiH), an amide-type local anesthetic agent, is commonly used in dermatological procedures. LiH is categorized as a BCS (biopharmaceutics classification system) class III group, which has high solubility and poor permeability. It should be noted that, in this context, LiH is intended as a local anesthetic, so the level of LiH in systemic circulation should be minimized to avoid toxicity and unwanted side effects such as hypotension and bradycardia. This study aimed to formulate and evaluate LiH-loaded dissolving microneedles (DMNs) with different polymer bases. Moreover, an in vitro permeation study using Franz diffusion cells and in vivo study were also performed. LiH-loaded DMNs were prepared using polymer groups of poly(vinyl pyrrolidone) (PVP-K30) and hyaluronic acid (HA). DMNs were created using the micro-molding method with centrifugation. The formulations selected based on the evaluation were F3 (HA 10%) and F5 (PVP-K30 25%). Based on the in vitro permeation study, the amount of drug permeated and deposited in the skin at F3 (HA 10%) was 247.1 ± 41.85 and 98.35 ± 12.86 μg, respectively. On the other hand, the amount of drug permeated and deposited in the skin at F5 (PVP-K30 25%) was 277.7 ± 55.88 and 59.46 ± 9.25 μg, respectively. Our in vivo drug-permeation study showed that only one rat from the PVP-K30 polymer group-with a concentration of 150.32 ng/mL-was detected on rat plasma. Therefore, LiH can be formulated into a DMN and can be deposited in the skin with a safe concentration of the drug permeating into systemic circulation.

Microneedle-Mediated Transdermal Delivery of Biopharmaceuticals

Transdermal delivery provides numerous benefits over conventional routes of administration. However, this strategy is generally limited to a few molecules with specific physicochemical properties (low molecular weight, high potency, and moderate lipophilicity) due to the barrier function of the stratum corneum layer. Researchers have developed several physical enhancement techniques to expand the applications of the transdermal field; among these, microneedle technology has recently emerged as a promising platform to deliver therapeutic agents of any size into and across the skin. Typically, hydrophilic biomolecules cannot penetrate the skin by passive diffusion. Microneedle insertion disrupts skin integrity and compromises its protective function, thus creating pathways (microchannels) for enhanced permeation of macromolecules. Microneedles not only improve stability but also enhance skin delivery of various biomolecules. Academic institutions and industrial companies have invested substantial resources in the development of microneedle systems for biopharmaceutical delivery. This review article summarizes the most recent research to provide a comprehensive discussion about microneedle-mediated delivery of macromolecules, covering various topics from the introduction of the skin, transdermal delivery, microneedles, and biopharmaceuticals (current status, conventional administration, and stability issues), to different microneedle types, clinical trials, safety and acceptability of microneedles, manufacturing and regulatory issues, and the future of microneedle technology.

Treatment of Hypertrophic Scars with Corticoid-Embedded Dissolving Microneedles

Hypertrophic scarring (HTS) is frequently observed after deep dermal and full-thickness skin defects. Local drug delivery in HTS has been shown more effective compared to other (minimally) invasive treatments. Disadvantages being operator-dependency and non-uniform drug distribution. Moreover, injections are painful and difficult when confronted with extensive scars or HTS in children. Corticoid-embedded dissolving microneedles (CEDMN) were developed that provide painless skin penetration and direct dermal drug delivery. Hyaluronic acid-based DMN and CEDMN patches were utilized. Structural analysis was performed via nuclear magnetic resonance (NMR) spectroscopy while gel permeation chromatography (GPC) was applied to determine chain length (molar mass) and dispersity of hyaluronic acid. Mechanical properties were evaluated by compression testing. Five burn victims with HTS were included. For each individual, three comparable scars were chosen. One control scar was left untreated. Two scars were treated with either 600 or 800 µm CEDMN patches. Patients were treated monthly for 4 months. Treatment with 800 µm CEDMN was initiated after 8 weeks. Assessor-blinded POSAS was registered. Hydration, evaporation, color and elasticity were recorded. The physico-chemical characterization suggests that the mechanical properties enable skin penetration and adequate drug delivery. Patients experienced the therapy as painless. According to the POSAS, all scars improved over time. However, the scars that were treated with CEDMN patches improved faster and with increased increment. The 800 µm CEDMN ensured the fastest POSAS-decrease. Hyaluronic acid-based CEDMN patches are valuable alternatives to intracicatrical injections, as they offer a painless and effective method for administering corticosteroids in HTS.

Long-Term Vaccine Delivery and Immunological Responses Using Biodegradable Polymer-Based Carriers

Biodegradable polymers are largely employed in the biomedical field, ranging from tissue regeneration to drug/vaccine delivery. The biodegradable polymers are highly biocompatible and possess negligible toxicity. In addition, biomaterial-based vaccines possess adjuvant properties, thereby enhancing immune responses. This Review introduces the use of different biodegradable polymers and their degradation mechanism. Different kinds of vaccines, as well as the interaction between the carriers with the immune system, then are highlighted. Natural and synthetic biodegradable micro-/nanoplatforms, hydrogels, and scaffolds for local or targeted and controlled vaccine release are subsequently discussed.

Polymeric microneedles for enhanced drug delivery in cancer therapy

Microneedles (MNs) have attracted the interest of researchers. Polymeric MNs offer tremendous promise as drug delivery vehicles for bio-applications because of their high loading capacity, strong patient adherence, excellent biodegradability and biocompatibility, low toxicity, and extremely cheap cost. Incorporating enhanced-property nanomaterials into polymeric MNs matrix increases their features such as better mechanical strength, sustained drug delivery, lower toxicity, and higher therapeutic effects, therefore considerably increasing their biomedical application. This paper discusses polymeric MN fabrication techniques and the present status of polymeric MNs as a delivery method for enhanced drug delivery in cancer therapeutic applications. Furthermore, the opportunities and challenges of polymeric MNs for improved drug delivery in cancer therapy are highlighted.

Design and Evaluation of Complex Polypeptide-Loaded Dissolving Microneedles for Improving Facial Wrinkles in Different Areas

Wrinkles are one of the most intuitive manifestations of skin aging. Complex polypeptide-loaded dissolving microneedles (CP-DMNs) for facial wrinkles in different areas have been developed and evaluated for the first time. In optimizing formulations, we compared the differences in CP-DMNs heights on skin insertion depth and skin repair and healing. Furthermore, systemic safety experiments were carried out to provide a reference for clinical application. On this basis, an 84-day efficacy assessment based on the improvement of facial wrinkles in different areas and a comparison between CP-DMNs vs. placebo was performed on 30 healthy subjects. As a result, DMNs with a height of 300 μm presented sufficient strength to pierce the stratum corneum with minimized skin damage. In addition, CP-DMNs possessed excellent biological safety and skin compatibility for clinical application. Compared with placebo, CP-DMNs exhibited obvious improvements in wrinkles distributed in the corners of eyes, under-eyes, and nasolabial folds. Furthermore, after using CP-DMNs for 84 days, facial wrinkles in five different areas were smoothed. In short, the complex polypeptides showed apparent anti-wrinkle efficacy with the aid of DMNs technology, and CP-DMNs seemed to work better on deeper wrinkles, such as frown lines and nasolabial folds.