Separable Microneedles for Synergistic Chemo-Photothermal Therapy against Superficial Skin Tumors

Customizable Fabrication of Photothermal Microneedles with Plasmonic Nanoparticles Using Low-Cost Stereolithography Three-Dimensional Printing

Photothermal microneedle (MN) arrays have the potential to improve the treatment of various skin conditions such as bacterial skin infections. However, the fabrication of photothermal MN arrays relies on time-consuming and potentially expensive microfabrication and molding techniques, which limits their size and translation to clinical application. Furthermore, the traditional mold-and-casting method is often limited in terms of the size customizability of the photothermal array. To overcome these challenges, we fabricated photothermal MN arrays directly via 3D-printing using plasmonic Ag/SiO2 (2 wt % SiO2) nanoaggregates dispersed in ultraviolet photocurable resin on a commercial low-cost liquid crystal display stereolithography printer. We successfully printed MN arrays in a single print with a translucent, nanoparticle-free support layer and photothermal MNs incorporating plasmonic nanoaggregates in a selective fashion. The photothermal MN arrays showed sufficient mechanical strength and heating efficiency to increase the intradermal temperature to clinically relevant temperatures. Finally, we explored the potential of photothermal MN arrays to improve antibacterial therapy by killing two bacterial species commonly found in skin infections. To the best of our knowledge, this is the first time describing the printing of photothermal MNs in a single step. The process introduced here allows for the translatable fabrication of photothermal MN arrays with customizable dimensions that can be applied to the treatment of various skin conditions such as bacterial infections.

Application of biomacromolecule-based passive penetration enhancement technique in superficial tumor therapy: A review

Transdermal drug delivery (TDD) has shown great promise in superficial tumor therapy due to its noninvasive and avoidance of the first-pass effect. Especially, passive penetration enhancement technique (PPET) provides the technical basis for TDD by temporarily altering the skin surface structure without requiring external energy. Biomacromolecules and their derived nanocarriers offer a wide range of options for PPET development, with outstanding biocompatibility and biodegradability. Furthermore, the abundant functional groups on biomacromolecule surfaces can be modified to yield functional materials capable of targeting specific sites and responding to stimuli. This enables precise drug delivery to the tumor site and controlled drug release, with the potential to replace traditional drug delivery methods and make PPET-related personalized medicine a reality. This review focuses on the mechanism of biomacromolecules and nanocarriers with skin, and the impact of nanocarriers' surface properties of nanocarriers on PPET efficiency. The applications of biomacromolecule-based PPET in superficial tumor therapy are also summarized. In addition, the advantages and limitations are discussed, and their future trends are projected based on the existing work of biomacromolecule-based PPET.

Microneedle-mediated nanomedicine to enhance therapeutic and diagnostic efficacy

Nanomedicine has been extensively explored for therapeutic and diagnostic applications in recent years, owing to its numerous advantages such as controlled release, targeted delivery, and efficient protection of encapsulated agents. Integration of microneedle technologies with nanomedicine has the potential to address current limitations in nanomedicine for drug delivery including relatively low therapeutic efficacy and poor patient compliance and enable theragnostic uses. In this Review, we first summarize representative types of nanomedicine and describe their broad applications. We then outline the current challenges faced by nanomedicine, with a focus on issues related to physical barriers, biological barriers, and patient compliance. Next, we provide an overview of microneedle systems, including their definition, manufacturing strategies, drug release mechanisms, and current advantages and challenges. We also discuss the use of microneedle-mediated nanomedicine systems for therapeutic and diagnostic applications. Finally, we provide a perspective on the current status and future prospects for microneedle-mediated nanomedicine for biomedical applications.

Red blood cell membrane-coated functionalized Cu-doped metal organic framework nanoformulations as a biomimetic platform for improved chemo-/chemodynamic/photothermal synergistic therapy

Nanoformulations for combining chemotherapy, chemodynamic therapy, and photothermal therapy have enormous potential in tumor treatment. Coating nanoformulations with cell membranes endows them with homologous cellular mimicry, enabling nanoformulations to acquire new functions and properties, including homologous targeting and long circulation in vivo, and can enhance internalization by homologous cancer cells. Herein, we fused multifunctional biomimetic nanoformulations based on Cu-doped zeolitic imidazolate framework-8 (ZIF-8). Hydroxycamptothecin (HCPT), a clinical anti-tumor drug, was encapsulated into ZIF-8, which was subsequently coated with polydopamine (PDA) and red blood cell membrane. The as-fabricated biomimetic nanoformulations showed an enhanced cell uptake in vitro and the potential to prolong blood circulation in vivo, producing effective synergistic chemotherapy, chemodynamic therapy, and photothermal therapy under the 808 nm laser irradiation. Together, the biomimetic nanoformulations showed a prolonged blood circulation and evasion of immune recognition in vivo to provide a bio-inspired strategy which may have the potential for the multi-synergistic therapy of breast cancer.

Red Blood Cell Membrane-Camouflaged Polydopamine and Bioactive Glass Composite Nanoformulation for Combined Chemo/Chemodynamic/Photothermal Therapy

Combinations of different therapeutic strategies, including chemotherapy (CT), chemodynamic therapy (CDT), and photothermal therapy (PTT), are needed to effectively address evolving drug resistance and the adverse effects of traditional cancer treatment. Herein, a camouflage composite nanoformulation (TCBG@PR), an antitumor agent (tubercidin, Tub) loaded into Cu-doped bioactive glasses (CBGs) and subsequently camouflaged by polydopamine (PDA), and red blood cell membranes (RBCm), was successfully constructed for targeted and synergetic antitumor therapies by combining CT of Tub, CDT of doped copper ions, and PTT of PDA. In addition, the TCBG@PRs composite nanoformulation was camouflaged with a red blood cell membrane (RBCm) to improve biocompatibility, longer blood retention times, and excellent cellular uptake properties. It integrated with long circulation and multimodal synergistic treatment (CT, CDT, and PTT) with the benefit of RBCms to avoid immune clearance for efficient targeted delivery to tumor locations, producing an "all-in-one" nanoplatform. In vivo results showed that the TCBG@PRs composite nanoformulation prolonged blood circulation and improved tumor accumulation. The combination of CT, CDT, and PTT therapies enhanced the antitumor therapeutic activity, and light-triggered drug release reduced systematic toxicity and increased synergistic antitumor effects.

Fabrication of lidocaine-loaded polymer dissolving microneedles for rapid and prolonged local anesthesia

There is an urgent need for research into effective interventions for pain management to improve patients' life quality. Traditional needle and syringe injection were used to administer the local anesthesia. However, it causes various discomforts, ranging from brief stings to trypanophobia and denial of medical operations. In this study, a dissolving microneedles (MNs) system made of composite matrix materials of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and sodium hyaluronate (HA) was successfully developed for the loading of lidocaine hydrochloride (LidH). The morphology, size and mechanical properties of the MNs were also investigated. After the insertion of MNs into the skin, the matrix at the tip of the MNs was swelled and dissolved by absorption of interstitial fluid, leading to a rapid release of loaded LidH from MNs' tips. And the LidH in the back patching was diffused into deeper skin tissue through microchannels created by MNs insertion, forming a prolonged anesthesia effect. In addition, the back patching of MNs could be acted as a drug reservoir to form a prolonged local anesthesia effect. The results showed that LidH MNs provided a superior analgesia up to 8 h, exhibiting a rapid and long-lasting analgesic effects. Additionally, tissue sectioning and in vitro cytotoxicity tests indicated that the MNs patch we developed had a favorable biosafety profile.

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.

Thermosensitive Microneedles Capable of On Demand Insulin Release for Precise Diabetes Treatment

As a novel painless and minimally invasive transdermal drug delivery method, microneedles have solved the challenges of microbial infection and tissue necrosis associated with multiple subcutaneous injections in patients with diabetes. However, traditional soluble microneedles cannot switch drug release on and off according to the patient's needs during long-term use, which is one of the most critical elements of diabetes treatment. Herein, an insoluble thermosensitive microneedle (ITMN) that can control the release of insulin by adjusting the temperature, enabling the precise treatment of diabetes is designed. Thermosensitive microneedles are produced by in situ photopolymerization of the temperature-sensitive compound N-isopropylacrylamide with the hydrophilic monomer N-vinylpyrrolidone, which is encapsulated with insulin and bound to a mini-heating membrane. ITMN are demonstrated to have good mechanical strength and temperature sensitivity, can release significantly different insulin doses at different temperatures, and effectively regulate blood glucose in type I diabetic mice. Therefore, the ITMN provides a possibility for intelligent and convenient on-demand drug delivery for patients with diabetes, and when combined with blood glucose testing devices, it has the potential to form an integrated and precise closed-loop treatment for diabetes, which is of great importance in diabetes management.

Dissolving microneedles-based programmed delivery system for enhanced chemo-immunotherapy of melanoma

Immune checkpoint blockade, especially the programmed cell death ligand 1 (PD-L1) blockade, has revolutionized the treatment of melanoma. However, PD-1/PD-L1 monotherapy leads to unsatisfactory therapeutic outcomes. The immunotherapy of melanoma could be improved by adding doxorubicin (DOX), which triggers immunogenic cell death (ICD) effect to activate anti-tumor immunity. Additionally, microneedles, especially dissolving microneedles (dMNs), can further enhance outcomes of chemo-immunotherapy due to the physical adjuvant effect of dMNs. Herein, we developed the dMNs-based programmed delivery system that incorporated pH-sensitive and melanoma-targeting liposomes to co-deliver DOX and siPD-L1, achieving enhanced chemo-immunotherapy of melanoma (si/DOX@LRGD dMNs). The incorporated si/DOX@LRGD LPs demonstrated uniform particle size, pH-sensitive drug release, high in vitro cytotoxicity and targeting ability. Besides, si/DOX@LRGD LPs effectively downregulated the expression of PD-L1, induced tumor cell apoptosis and triggered ICD effect. The si/DOX@LRGD LPs also showed deep penetration (approximately 80 μm) in 3D tumor spheroids. Moreover, si/DOX@LRGD dMNs dissolved rapidly into the skin and had sufficient mechanical strength to penetrate skin, reaching a depth of approximately 260 μm in mice skin. In mice model of melanoma tumor, si/DOX@LRGD dMNs exhibited better anti-tumor efficacy than monotherapy by dMNs and tail intravenous injection at the same dose. This was due to the higher cytotoxic CD8+ T cells and the secreted cytotoxic cytokine IFN-γ evoked by si/DOX@LRGD dMNs, thereby eliciting strong T-cell mediated immune response and resulted in enhanced anti-tumor effects. In conclusion, these findings suggested that si/DOX@LRGD dMNs provided a promising and effective strategy for enhanced chemo-immunotherapy of melanoma.

New Insights in Topical Drug Delivery for Skin Disorders: From a Nanotechnological Perspective

Skin, the largest organ in humans, is an efficient route for the delivery of drugs as it circumvents several disadvantages of the oral and parenteral routes. These advantages of skin have fascinated researchers in recent decades. Drug delivery via a topical route includes moving the drug from a topical product to a locally targeted region with dermal circulation throughout the body and deeper tissues. Still, due to the skin's barrier function, delivery through the skin can be difficult. Drug delivery to the skin using conventional formulations with micronized active components, for instance, lotions, gels, ointments, and creams, results in poor penetration. The use of nanoparticulate carriers is one of the promising strategies, as it provides efficient delivery of drugs through the skin and overcomes the disadvantage of traditional formulations. Nanoformulations with smaller particle sizes contribute to improved permeability of therapeutic agents, targeting, stability, and retention, making nanoformulations ideal for drug delivery through a topical route. Achieving sustained release and preserving a localized effect utilizing nanocarriers can result in the effective treatment of numerous infections or skin disorders. This article aims to evaluate and discuss the most recent developments of nanocarriers as therapeutic agent vehicles for skin conditions with patent technology and a market overview that will give future directions for research. As topical drug delivery systems have shown great preclinical results for skin problems, for future research directions, we anticipate including in-depth studies of nanocarrier behavior in various customized treatments to take into account the phenotypic variability of the disease.

Porcupine-inspired microneedles coupled with an adhesive back patching as dressing for accelerating diabetic wound healing

Diabetes chronic wound is a severe and frequently occurring medical issue in patients with diabetes that often leads to more serious complications. Microneedles (MNs) can be used for wound healing as they can effectively pierce the epidermis and inject drugs into the wound tissue. However, common MN patches cannot provide sufficient skin adhesion to prevent detachment from the wound area. Inspired by the barb hangnail microstructure of porcupine quills, a porcupine quill-like multilayer MN patch with an adhesive back patching for tissue adhesion and diabetic wound healing was designed. Sodium hyaluronate-modified CaO2 nanoparticles and metformin (hypoglycemic agent) were loaded into the polycaprolactone tips of MNs, endowing them with exceptional antibacterial ability and hypoglycemic effect. A flexible and adhesive back patching was formed by polyacrylamide-polydopamine/Cu2+ composite hydrogel, which ensures that the MN patches do not peel off from the application sites and reduce bacterial infection. The bioinspired multilayer structure of MN patches exhibits satisfactory mechanical and antibacterial properties, which is a potential multifunctional dressing platform for promoting wound healing. STATEMENT OF SIGNIFICANCE: The porcupine quill-like microneedles (MNs) with PAM-PDA/Cu2+ (PPC) composite hydrogel back patching have been fabricated, which can enhance the adhesion property of MNs to the skin through a physical interlock of multilayer MNs and chemical bonding of hydrogel patching. CaO2-HA NPs and metformin were loaded into the polycaprolactone tips of MNs, endowing them with the exceptional antibacterial ability and hypoglycemic effect, which could accelerate diabetic wound healing. As a safe and effective strategy in transdermal delivery of drugs, the as-fabricated flexible multilayer MN patch with good antibacterial, hypoglycemic, and biocompatibility has been used to promote the healing of diabetic wound by releasing oxygen and inhibiting inflammation at the wound site.

Hybrid microneedle arrays for antibiotic and near-IR photothermal synergistic antimicrobial effect against Methicillin-Resistant Staphylococcus aureus

The rise of antibiotic-resistant skin and soft tissue infections (SSTIs) necessitates the development of novel treatments to improve the efficiency and delivery of antibiotics. The incorporation of photothermal agents such as plasmonic nanoparticles (NPs) improves the antibacterial efficiency of antibiotics through synergism with elevated temperatures. Hybrid microneedle (MN) arrays are promising local delivery platforms that enable co-therapy with therapeutic and photothermal agents. However, to-date, the majority of hybrid MNs have focused on the potential treatment of skin cancers, while suffering from the shortcoming of the intradermal release of photothermal agents. Here, we developed hybrid, two-layered MN arrays consisting of an outer water-soluble layer loaded with vancomycin (VAN) and an inner water-insoluble near-IR photothermal core. The photothermal core consists of flame-made plasmonic Au/SiO2 nanoaggregates and polymethylmethacrylate (PMMA). We analyzed the effect of the outer layer polymer, polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP), on MN morphology and performance. Hybrid MNs produced with 30 wt% PVA contain a highly drug-loaded outer shell allowing for the incorporation of VAN concentrations up to 100 mg g-1 and temperature increases up to 60 °C under near-IR irradiation while showing sufficient mechanical strength for skin insertion. Furthermore, we studied the combinatorial effect of VAN and heat on the growth inhibition of methicillin-resistant Staphylococcus aureus (MRSA) showing synergistic inhibition between VAN and heat above 55 °C for 10 min. Finally, we show that treatment with hybrid MN arrays can inhibit the growth of MRSA due to the synergistic interaction of heat with VAN reducing the bacterial survival by up to 80%. This proof-of-concept study demonstrates the potential of hybrid, two-layered MN arrays as a novel treatment option for MRSA-associated skin infections.

Research progress of physical transdermal enhancement techniques in tumor therapy

The advancement and popularity of transdermal drug delivery (TDD) based on the physical transdermal enhancement technique (PTET) has opened a new paradigm for local tumor treatment. The drug can be directly delivered to the tumor site through the skin, thus avoiding the toxic side effects caused by the first-pass effect and achieving high patient compliance. Further development of PTETs has provided many options for antitumor drugs and laid the foundation for future applications of wearable closed-loop targeting drug delivery systems. In this highlight, the different types of PTETs and related mechanisms, and applications of PTET-related tumor detection and therapy are highlighted. According to their type and characteristics, PTETs are categorized as follows: (1) iontophoresis, (2) electroporation, (3) ultrasound, (4) thermal ablation, and (5) microneedles. PTET-related applications in the local treatment of tumors are categorized as follows: (1) melanoma, (2) breast tumor, (3) squamous cell carcinoma, (4) cervical tumor, and (5) others. The challenges and future prospects of existing PTETs are also discussed. This highlight will provide guidance for the design of PTET-based wearable closed-loop targeting drug delivery systems and personalized therapy for tumors.

Transdermal delivery of allopurinol to acute hyperuricemic mice via polymer microneedles for the regulation of serum uric acid levels

Allopurinol (AP) is widely used to treat hyperuricemia which may cause severe side effects upon oral administration. Alternative means for the treatment of hyperuricemia are demanded to simultaneously facilitate drug absorption, patient compliance, and fewer side effects. In this study, a new polymer microneedle (MN) system was developed for the transdermal delivery of AP to acute hyperuricemic mice. This study aims to achieve the controllable regulation of serum uric acid (SUA) levels with fewer side effects compared with oral administration. The matrix of polymer MNs consisted of polyvinylpyrrolidone (PVP) and polycaprolactone (PCL), in which the rapid dissolution of PVP offers a rapid dissolution of AP into the blood and the biodegradability of PCL resulting in a sustainable drug release behavior. An in vivo study demonstrated that the AP-loaded MN system can effectively reduce the SUA levels as oral administration with lower side effects, which will be conducive to reducing the adverse reactions and improving the bioavailability of AP. This MN-mediated strategy can facilitate transcutaneous hyperuricemia treatment and provide a new alternative for the exploration of clinical treatment of hyperuricemia and improvement of patient compliance.

Reaching new lights: a review on photo-controlled nanomedicines and their in vivo evaluation

The selective and efficient delivery of bioactive molecules to sites of interest remains a formidable challenge in medicine. In recent years, it has been shown that stimuli-responsive drug delivery systems display several advantages over traditional drug administration such as an improved pharmacokinetic profile and the desirable ability to gain control over release. Light emerged as one of the most powerful stimuli due to its high biocompatibility, spatio-temporal control, and non-invasiveness. On the road to clinical translation, various chemical systems of high complexity have been reported with the aim to improve efficacy, safety, and versatility of drug delivery under complex biological conditions. For future research on the chemical design of such photo-controlled nanomedicines, it is essential to gain an understanding of their in vivo translation and efficiency. Here, we discuss photo-controlled nanomedicines that have been evaluated in vivo and provide an overview of the state-of-the-art that should guide future research design.

Photoresponsive polymeric microneedles: An innovative way to monitor and treat diseases

Microneedles (MN) technology is an emerging technology for the transdermal delivery of therapeutics. When combined with photoresponsive (PR) materials, MNs can deliver therapeutics precisely and effectively with enhanced efficacy or synergistic effects. This review systematically summarizes the therapeutic applications of PRMNs in cancer therapy, wound healing, diabetes treatment, and diagnostics. Different PR approaches to activate and control the release of therapeutic agents from MNs are also discussed. Overall, PRMNs are a powerful tool for stimuli-responsive controlled-release therapeutic delivery to treat various diseases.

PVP-microneedle array for drug delivery: mechanical insight, biodegradation, and recent advances

Microneedle arrays are micron-sized needles usually attached to a supporting base or patch facilitated drug delivery for systemic effects. Polyvinylpyrrolidone (PVP) is a lactam polymer containing an internal amide linkage. Because of its versatility and biocompatibility, it has been widely utilized to treat several skin, bone and eye problems. Due to its specific and unique properties, the researchers realize its utility as a polymer of tremendous potential. PVP-based dissolvable microneedles have widely been utilized as a carrier for delivering DNAs, proteins, vitamins, and several biological macromolecules transdermally. However, it does not get biodegraded into the body. Therefore, the presence of its fragments in the body post-treatment needs proper justification. The adequate justification for the fate of the fragment's end products in the body will allow even better utilization of PVP. This review analyses and illustrates various experimental findings to highlight the most recent advancements and applications of PVP microneedles in drug delivery systems and cosmetology and the potential for PVP microneedles in treating dermal and systemic disorders. This review presents the expected mode of PVP biodegradation in aqueous and soil environments as a waste material, its inertness, biocompatibility, and the importance of PVP as a fabricating material, pharmaceutical uses, and non-toxic profile.

A spark to the powder keg: Microneedle-based antitumor nanomedicine targeting reactive oxygen species accumulation for chemodynamic/photothermal/chemotherapy

HYPOTHESIS

Chemodynamic therapy (CDT) can efficiently kill cancer cells by producing hydroxyl radical (•OH), a kind of high-toxic reactive oxygen species (ROS), via Fenton or Fenton-like reactions. This study involved a versatile nanomedicine, MSN@DOX/GA-Fe/PDA (M@DGP), delivered via microneedles, which was expected to combine chemodynamic/photothermal/chemotherapy and efficiently increase ROS accumulation to achieve significant therapeutic efficacy against melanoma.

EXPERIMENTS

The composition of the synthesized nanoparticles was confirmed by a series of characterizations including transmission electron microscopy, Fourier transform infrared spectroscopy, and zeta potential. The photothermal properties of the nanomedicine was evaluated via infrared imaging, and •OH-producing ability was evaluated by UV-Vis and electron spin resonance. The mechanisms of ROS accumulation were studied in B16 cells by detecting intracellular •OH, glutathione, and ROS levels. The drug-loaded microneedles (M@DGP-MNs) were prepared, and their morphology and mechanical strength were characterized. The in vivo antimelanoma effect and biosafety evaluation of the nanomedicine were investigated in tumor-bearing C57 mice.

FINDINGS

M@DGP was successfully prepared and could achieve ROS accumulation through a photothermal-enhanced Fenton reaction, polydopamine-induced glutathione consumption, and doxorubicin-mediated mitochondrial dysfunction which induced oxidative stress and apoptosis of tumor cells. M@DGP-MNs showed superior antitumor efficacy and good biosafety, providing a promising strategy for melanoma treatment.

Next-Generation 3D Scaffolds for Nano-Based Chemotherapeutics Delivery and Cancer Treatment

Cancer is the leading cause of death after cardiovascular disease. Despite significant advances in cancer research over the past few decades, it is almost impossible to cure end-stage cancer patients and bring them to remission. Adverse effects of chemotherapy are mainly caused by the accumulation of chemotherapeutic agents in normal tissues, and drug resistance hinders the potential therapeutic effects and curing of this disease. New drug formulations need to be developed to overcome these problems and increase the therapeutic index of chemotherapeutics. As a chemotherapeutic delivery platform, three-dimensional (3D) scaffolds are an up-and-coming option because they can respond to biological factors, modify their properties accordingly, and promote site-specific chemotherapeutic deliveries in a sustainable and controlled release manner. This review paper focuses on the features and applications of the variety of 3D scaffold-based nano-delivery systems that could be used to improve local cancer therapy by selectively delivering chemotherapeutics to the target sites in future.

Highly Efficient Near-IR Photothermal Microneedles with Flame-Made Plasmonic Nanoaggregates for Reduced Intradermal Nanoparticle Deposition

Near-infrared (NIR) photothermal therapy by microneedles (MNs) exhibits high potential against skin diseases. However, high costs, photobleaching of organic agents, low long-term stability, and potential nanotoxicity limit the clinical translation of photothermal MNs. Here, photothermal MNs are developed by utilizing Au nanoaggregates made by flame aerosol technology and incorporated in water-insoluble polymer matrix to reduce intradermal nanoparticle (NP) deposition. The individual Au interparticle distance and plasmonic coupling within the nanoaggregates are controlled by the addition of a spacer during their synthesis rendering the Au nanoaggregates highly efficient NIR photothermal agents. In situ aerosol deposition of Au nanoaggregates on MN molds results in the fabrication of photothermal MNs with thin plasmonic layers. The photothermal performance of these MN arrays is compared to ones made by three methods utilizing NP dispersions, and it is found that similar temperatures are reached with 28-fold lower Au mass due to reduced light scattering losses of the thin layers. Finally, all developed photothermal MN arrays here cause clinically relevant hyperthermia at benign laser intensities while reducing intradermal NP deposition 127-fold compared to conventional MNs made with water-soluble polymers. Such rational design of photothermal MNs requiring low laser intensities and minimal NP intradermal accumulation sets the basis for their safe clinical translation.

Microneedles-mediated drug delivery system for the diagnosis and treatment of melanoma

As an emerging novel drug delivery system, microneedles (MNs) have a wide range of applications in the medical field. They can overcome the physiological barriers of the skin, penetrate the outermost skin of the human body, and form hundreds of reversible microchannels to enhance the penetration of drugs and deliver drugs to the diseased sites. So they have great applications in the diagnosis and treatment of melanoma. Melanoma is a kind of malignant tumor, the survival rate of patients with metastases is extremely low. The traditional methods of surgery and drug treatment for melanoma are often accompanied by large adverse reactions in the whole body, and the drug concentration is low. The use of MNs for transdermal administration can increase the drug concentration, reduce adverse reactions in the treatment process, and have good therapeutic effect on melanoma. This paper introduced various types of MNs and their preparation methods, summarized the diagnosis and various treatment options for melanoma with MNs, focused on the treatment of melanoma with dissolved MNs, and made prospect of MNs-mediated transdermal drug delivery in the treatment of melanoma.

Transdermal Insulin Delivery and Microneedles-based Minimally Invasive Delivery Systems

Diabetes has become a serious threat to human health, causing death and pain to numerous patients. Transdermal insulin delivery is a substitute for traditional insulin injection to avoid pain from the injection. Transdermal methods include non-invasive and invasive methods. As the non-invasive methods could hardly get through the stratum corneum, minimally invasive devices, especially microneedles, could enhance the transappendageal route in transcutaneous insulin delivery, and could act as connectors between the tissue and outer environment or devices. Microneedle patches have been in quick development in recent years and with different types, materials and functions. In those patches, the smart microneedle patch could perform as a sensor and reactor responding to glucose to regulate the blood level. In the smart microneedles field, the phenylboronic acid system and the glucose oxidase system have been successfully applied on the microneedle platform. Insulin transdermal delivery strategy, microneedles technology and smart microneedles' development would be discussed in this review.

Microneedle-mediated drug delivery for cutaneous diseases

Microneedles have garnered significant interest as transdermal drug delivery route owing to the advantages of nonselective loading capacity, minimal invasiveness, simple operation, and good biocompatibility. A number of therapeutics can be loaded into microneedles, including hydrophilic and hydrophobic small molecular drugs, and macromolecular drugs (proteins, mRNA, peptides, vaccines) for treatment of miscellaneous diseases. Microneedles feature with special benefits for cutaneous diseases owing to the direct transdermal delivery of therapeutics to the skin. This review mainly introduces microneedles fabricated with different technologies and transdermal delivery of various therapeutics for cutaneous diseases, such as psoriasis, atopic dermatitis, skin and soft tissue infection, superficial tumors, axillary hyperhidrosis, and plantar warts.

Microneedle patch with "spongy coating" to co-load multiple drugs to treat multidrug-resistant melanoma

Melanoma is the most aggressive skin malignancy that continues to increase in worldwide. The transferability and multidrug resistance lead to a high fatality rate. Synergistic administration of hydrophilic carboplatin (CBP) and hydrophobic vorinostat (SAHA) can be a reliable way to treat multidrug-resistant melanoma. However, the different physicochemical properties of multiple drugs make it difficult to achieve a convenient co-loading and an ideal synergistic treatment efficacy. To solve the problem, a microneedle patch with a porous "spongy coating" (PF-MNP) was fabricated. Firstly, (polyacrylic acid/polyethyleneimine)₁₀ multilayers were fabricated on polymethyl methacrylate MNP. Then a "spongy coating" was achieved by acid treatment and freeze-drying. Due to the capillary effect, hydrophobic SAHA and hydrophilic CBP could be conveniently adsorbed step-by-step. The two drugs could distribute evenly on the surface, and the morphology of MNP remained good. The loading content of SAHA and CBP was easily regulated by adjusting the concentration of the adsorption solution, and MNP could quickly release most drugs within 30 min. The final in vivo experiments proved that CBP/SAHA co-loaded PF-MNP had the best therapeutic efficiency for multidrug-resistant melanoma. The MNP with a "spongy coating" showed potential to be a safe and efficient transdermal delivery platform for multiple drugs.

Research progress on detachable microneedles for advanced applications

INTRODUCTION

Microneedles (MNs) have undergone great advances in transdermal drug delivery, and commercialized MN applications are currently available in vaccination and cosmetic products. Despite the development of MN technologies, common limitations of MN products still exist. Typical MN patches are applied to target tissues, where the substrate of an MN patch must remain until the drug is delivered, which reduces patients' compliance and hinders the applicability of the MN technique to many diseases in various tissues. MN research is ongoing to solve this issue.

AREAS COVERED

Most recent MNs developed by combining various biomaterials with appropriate fabrication processes are detachable MNs (DeMNs). Because of advances in biomaterials and fabrication techniques, various DeMNs have been rapidly developed. In this review, we discuss four types of DeMN: substrate-separable, multi-layered, crack-inducing, and shell DeMN. These DeMNs deliver various therapeutic agents ranging from small- and large-molecular-weight drugs to proteins and even stem cells for regeneration therapy. Furthermore, DeMNs are applied to skin as well as non-transdermal tissues.

EXPERT OPINION

It has become increasingly evident that novel MN technologies can be expected in terms of designs, fabrication methods, materials, and even possible application sites given the recent advances in DeMNs.

An update on biomaterials as microneedle matrixes for biomedical applications

Microneedles (MNs) have been developed for various applications such as drug delivery, cosmetics, diagnosis, and biosensing. To meet the requirements of MNs used in these areas, numerous materials have been used for the fabrication of MNs. However, MNs will be exposed to skin tissues after piercing the stratum corneum barrier. Thus, it is necessary to ensure that the matrix materials of MNs have the characteristics of low toxicity, good biocompatibility, biodegradability, and sufficient mechanical properties for clinical application. In this review, the matrix materials currently used for preparing MNs are summarized and reviewed in terms of these factors. In addition, MN products used on the market and their applications are summarized in the end. This work may provide some basic information to researchers in the selection of MN matrix materials and in developing new materials.

Research progress of microneedles in the treatment of melanoma

Melanoma is an aggressive malignancy deriving from melanocytes, which is characterized by high tendency of metastases and mortality rate. Current therapies for melanoma, like chemotherapy, immunotherapy and targeted therapy, have the problem of systemic exposure of drugs, which will lead to many side effects and premature degradation of drugs. The resulting low drug accumulation at the lesion limits the therapeutic effect on melanoma and makes the cure rate low. As an emerging drug delivery system, microneedles (MNs) can efficiently deliver drugs through the skin, increase the drug distribution in deeper tumor sites and minimize the leakage of therapeutic drugs into adjacent tissues, thus improving the therapeutic effect. In addition, compared with traditional drug delivery methods, MN-based drug delivery system has the advantages of simplicity, safety and little pain. So MNs can be developed for the treatment of melanoma, which can relieve the pain of patients and improve the survival rate. This review aims to introduce an update on the progress of MNs as an innovative strategy for melanoma, especially when MNs combining with different therapies against melanoma, such as chemotherapy, targeted therapy, immunotherapy, photothermal therapy (PTT), photodynamic therapy (PDT) and synergic therapy.

Recent Progress in Microneedles-Mediated Diagnosis, Therapy, and Theranostic Systems

Theranostic system combined diagnostic and therapeutic modalities is critical for the real-time monitoring of disease-related biomarkers and personalized therapy. Microneedles, as a multifunctional platform, are promising for transdermal diagnostics and drug delivery. They have shown attractive properties including painless skin penetration, easy self-administration, prominent therapeutic effects, and good biosafety. Herein, an overview of the microneedles-based diagnosis, therapies, and theranostic systems is given. Four microneedles-based detection methods are concluded based on the sensing mechanism: i) electrochemistry, ii) fluorometric, iii) colorimetric, and iv) Raman methods. Additionally, robust microneedles are suitable for implantable drug delivery. Microneedles-assisted transdermal drug delivery can be primarily classified as passive, active, and responsive drug release, based on the release mechanisms. Microneedles-assisted oral and implantable drug delivery mechanisms are also presented in this review. Furthermore, the key frontier developments in microneedles-mediated theranostic systems as the major selling points are emphasized in this review. These systems are classified into open-loop and closed-loop theranostic systems based on the indirectness and directness of feedback between the transdermal diagnosis and therapy, respectively. Finally, conclusions and future perspectives for next-generation microneedles-mediated theranostic systems are also discussed. Taken together, microneedle-based systems are promising as the new avenue for diagnosis, therapy, and disease-specific closed-loop theranostic applications.

GelMA/PEGDA microneedles patch loaded with HUVECs-derived exosomes and Tazarotene promote diabetic wound healing

Clinical work and research on diabetic wound repair remain challenging globally. Although various conventional wound dressings have been continuously developed, the efficacy is unsatisfactory. The effect of drug delivery is limited by the depth of penetration. The sustained release of biomolecules from biological wound dressings is a promising treatment approach to wound healing. An assortment of cell-derived exosomes (exos) have been proved to be instrumental in tissue regeneration, and researchers are dedicated to developing biomolecules carriers with unique properties. Herein, we reported a methacrylate gelatin (GelMA) microneedles (MNs) patch to achieve transdermal and controlled release of exos and tazarotene. Our MNs patch comprising GelMA/PEGDA hydrogel has distinctive biological features that maintain the biological activity of exos and drugs in vitro. Additionally, its unique physical structure prevents it from being tightly attached to the skin of the wound, it promotes cell migration, angiogenesis by slowly releasing exos and tazarotene in the deep layer of the skin. The full-thickness cutaneous wound on a diabetic mouse model was carried out to demonstrate the therapeutic effects of GelMA/PEGDA@T + exos MNs patch. As a result, our GelMA/PEGDA@T + exos MNs patch presents a potentially valuable method for repairing diabetic wound in clinical applications.

Recent advances in polymer microneedles for drug transdermal delivery: Design strategies and applications

In recent years, the transdermal drug delivery based on microneedles (MNs) technology has received extensive attention, which offers a safer and painless alternative to hypodermic needle injection. They can pierce the stratum corneum and deliver drugs to the epidermis and dermis-structures of skin, showing prominent properties such as minimally invasive, bypassing first-pass metabolism, and self-administered. A range of materials have been used to fabricate MNs, such as silicon, metal, glass, and polymers. Among them, polymer MNs have gained increasing attention from pharmaceutical and cosmetic companies as one of the promising drug delivery methods. Microneedle products have recently become available on the market, and some of them are under evaluation for efficacy and safety. This paper focuses on current state of polymer MNs in the drug transdermal delivery. The materials and methods for the fabrication of polymer MNs and their drug administration are described. The recent progresses of polymer MNs for treatment of cancer, vaccine delivery, blood glucose regulation, androgenetic alopecia, obesity, tissue healing, myocardial infarction and gout are reviewed. The challenges of MNs technology are summarized and the future development trend of MNs is also prospected. This article is protected by copyright. All rights reserved.

Studies on local anesthetic lidocaine hydrochloride delivery via photo-triggered implantable polymeric microneedles as a patient-controlled transdermal analgesia system

This study aimed to develop photo-triggered implantable polymeric microneedles (MNs) for successful drug delivery in a transdermal analgesia system. The prepared iron oxide nanoparticles (Fe₃O₄NPs) were coated with polydopamine (PDA) followed by polyvinylpyrrolidone (PVP) and polycaprolactone (PCL). While the PCL/PVP-Fe₃O₄NPs synthesis, the absorption band of PVP at 1656 cm^-1 shifted to 1665 cm^-1 which indicate the presence of interaction between Fe⁺ and C = O groups. The size and morphology of PCL/PVP-Fe₃O₄NPs were examined by scanning electron microscope and transmission electron microscope (SEM and TEM) analysis. The results confirmed that the prepared PCL/PVP-Fe₃O₄NPs were spherical with sizes ranging from 9 to 11 nm. The lidocaine hydrochloride content in the microneedles was 3.72 ± 0.31 mg and A + 2.2S ≤ L representing that the drug was uniformly distributed. The insertion ability of lidocaine hydrochloride@PCL/PVP-Fe₃O₄NPs-DMNs was tested by porcine skin. The results demonstrated outstanding insertion ability and potential for drug delivery. In addition, near-infrared (NIR) irradiation has the potential to penetrate the skin and enhance lidocaine hydrochloride-releasing activity. The in vivo experimental data confirmed that lidocaine hydrochloride@PCL/PVP-Fe₃O₄NPs-DMNs allowed for painless drug delivery by breaking the barrier of the stratum corneum. To conclude, lidocaine hydrochloride can be safely delivered through the transdermal analgesic system, with a quick onset time.

Skin cancer biology and barriers to treatment: Recent applications of polymeric micro/nanostructures

Background

Skin cancer has been the leading type of cancer worldwide. Melanoma and non-melanoma skin cancers are now the most common types of skin cancer that have been reached to epidemic proportion. Based on the rapid prevalence of skin cancers, and lack of efficient drug delivery systems, it is essential to surge the possible ways to prevent or cure the disease.

Aim of review

Although surgical modalities and therapies have been made great progress in recent years, however, there is still an urgent need to alleviate its increased burden. Hence, understanding the precise pathophysiological signaling mechanisms and all other factors of such skin insults will be beneficial for the development of more efficient therapies.

Key scientific concepts of review

In this review, we explained new understandings about onset and development of skin cancer and described its management via polymeric micro/nano carriers-based therapies, highlighting the current key bottlenecks and future prospective in this field. In therapeutic drug/gene delivery approaches, polymeric carriers-based system is the most promising strategy. This review discusses that how polymers have successfully been exploited for development of micro/nanosized systems for efficient delivery of anticancer genes and drugs overcoming all the barriers and limitations associated with available conventional therapies. In addition to drug/gene delivery, intelligent polymeric nanocarriers platforms have also been established for combination anticancer therapies including photodynamic and photothermal, and for theranostic applications. This portfolio of latest approaches could promote the blooming growth of research and their clinical availability.

Systematic comparisons of dissolving and swelling hyaluronic acid microneedles in transdermal drug delivery

Transdermal drug delivery efficacy of hyaluronic acid dissolving microneedles (HA DMNs) is limited by low loading dose and poor drug condensation in needles. HA swelling MNs (HA SMNs) could improve the efficacy, but comparisons between the formulations is missing. In this work, DMNs and SMNs were fabricated of HA and methacrylated HA, respectively. Their properties of transdermal drug delivery were systematically compared. HA SMNs exhibited enhanced mechanical strength, fast swelling performance, and extended duration of microchannels in skin. The doxorubicin (DOX) loaded by one-step loading protocol in needles and baseplate of SMNs could be transdermally delivered through the diffusing path mediated by swollen needles, conquering the limit of poor drug condensation in DMNs needles and generated a longer Tmax but higher Cmax. The relative bioavailability of DOX/SMNs towards DOX/DMNs was 200% within 12 h. The results provide theoretical references for the application of HA MNs mediated transdermal drug delivery.

Transdermal delivery of multifunctional CaO2@Mn-PDA nanoformulations by microneedles for NIR-induced synergistic therapy against skin melanoma

The development of multifunctional nanoformulations (NFs) include several features in a single nanosystem for these devices to overcome the disadvantages of inefficiency and undesirable toxicity of traditional therapies and provide new opportunities in the management of tumors. Herein, multifunctional CaO₂@Mn-PDA NFs with a core-shell structure, integrating the photothermal conversion properties of Mn-PDA, the chemodynamic properties of doped Mn ions, and relieving hypoxia in the tumor microenvironment (TME) were developed. The as-fabricated CaO₂@Mn-PDA NFs were embedded in microneedles (MNs) for transdermal delivery into tumor sites, leading to the generation of a new minimally invasive and synergistic therapeutic strategy against skin melanoma. Under near-infrared (NIR) light irradiation, the CaO₂@Mn-PDA NFs exhibited a synergistic therapeutic effect, including photothermal therapy (PTT), chemodynamic therapy (CDT), and modulating hypoxia due to their high photothermal conversion efficiency, boosted intracellular production of reactive oxygen species, excellent chemodynamic reactions, etc. Therefore, the developed MN platform, which can build implanted multifunctional characteristics for on-demand NIR-induced synergistic therapy, have a bright future in tumor suppression.

3D-Printed Hydrogel-Filled Microneedle Arrays

Microneedle arrays (MNAs) have been used for decades to deliver drugs transdermally and avoid the obstacles of other delivery routes. Hydrogels are another popular method for delivering therapeutics because they provide tunable, controlled release of their encapsulated payload. However, hydrogels are not strong or stiff, and cannot be formed into constructs that penetrate the skin. Accordingly, it has so far been impossible to combine the transdermal delivery route provided by MNAs with the therapeutic encapsulation potential of hydrogels. To address this challenge, a low cost and simple, but robust, strategy employing MNAs is developed. These MNAs are formed from a rigid outer layer, 3D printed onto a conformal backing, and filled with drug-eluting hydrogels. Microneedles of different lengths are fabricated on a single patch, facilitating the delivery of various agents to different tissue depths. In addition to spatial distribution, temporal release kinetics can be controlled by changing the hydrogel composition or the needles' geometry. As a proof-of-concept, MNAs are used for the delivery of vascular endothelial growth factor (VEGF). Application of the rigid, resin-based outer layer allows the use of hydrogels regardless of their mechanical properties and makes these multicomponent MNAs suitable for a range of drug delivery applications.

Dissolvable carboxymethyl cellulose/polyvinylpyrrolidone microneedle arrays for transdermal delivery of Amphotericin B to treat cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) is a significant public health problem caused by different species of Leishmania parasites. Due to low skin permeability, the development of an effective system for delivery of Amphotericin B (AMB), the common effective drug for leishmaniasis treatment, is required to replace the unpleasant and problematic injections. To overcome this problem, a dissolvable microneedle (MN) patch was developed, using biodegradable polymers (a mixture of polyvinylpyrrolidone and carboxymethyl cellulose) for AMB's transdermal delivery. Scanning electron microscopy and fluorescent images showed successful fabrication of the MNs and homogeneous dispersion of the drug into the needles. MNs showed good mechanical properties with the ability to penetrate the rat skin and reach the lower layers. After insertion to the skin, the MNs were rapidly dissolved to release the encapsulated drug, and the resulted micropores in the skin were quickly resealed within 30 min. MN patches showed non-toxicity as exposed to HT-29 cell line. Flow cytometry results showed a potent in vitro leishmanicidal activity of AMB-loaded MN patches against the Leishmania parasites (up to 86% of the parasites' death). Taken together, MN patches might represent a new, efficient and clinically translational approach for transdermal AMB delivery to treat CL.

Fabrication of Rapidly Separable Microneedles for Transdermal Delivery of Metformin on Diabetic Rats

In this work, the rapidly separable microneedles (MNs) consisted of needle-tips and supporting bases have been fabricated by a step-by-step coating method. Poly (vinyl alcohol) (PVA) have been used to prepare the needle-tips of MNs in which they are capped on the solvable supporting bases consisted of sodium bicarbonate, poly (vinyl pyrolidone) (PVP), and tartaric acid (TA) (NaHCO₃/PVP/TA). After insertion into the skin, the needle-tips can be separated rapidly from the patches within 90 s due to the generation of air bubbles in the supporting bases by the reaction between NaHCO₃ and TA after absorption of tissue fluid, leading to the needle-tips remaining in the skin tissue. Metformin, a hypoglycemic drug, encapsulated in the needle-tips of MNs can be released due to swelling and decomposition of PVA by the absorption of tissue fluid. To investigate the pharmacological effect via transdermal delivery route, metformin-loaded MNs are applied on the diabetic SD rats induced by streptozotocin (STZ). They exhibit a longer hypoglycemic effect in vivo than that of subcutaneous injection. These results indicated the as-fabricated rapidly separable MNs present a promising platform for transdermal delivery of drugs against diabetic patients.

Novel dissolving microneedles preparation for synergistic melasma therapy: Combined effects of tranexamic acid and licorice extract

The aim of this study was to prepare dissolving microneedles (DMNs) patches containing tranexamic acid (TA) for the treatment of melasma. Polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) were preferred as matrix materials through the compatibility experiment. In the in vitro permeation study, the transdermal amount of TA was significantly promoted through dissolving microneedles with the cumulative release was 44.43 ± 6.55%. By comparison, the release of TA solution assisted with solid microneedles (SMNs) was merely 11.31 ± 2.30% (p < 0.05). Pharmacokinetics study indicated the bioavailability of dissolving microneedles was more than 1.3 times compared with oral administration. In pharmacodynamics investigation, TA dissolving microneedles obviously reduced melanin deposition in the skin of melasma guinea pigs after 8 consecutive administrations. In particular, the combination of tranexamic acid and licorice extract (LIC) dissolving microneedles worked better than tranexamic acid alone. Accelerated stress conditions including high temperature, high humidity, as well as photostability were designed to prove that TA microneedles maintained good pharmaceutical stability. In conclusion, tranexamic acid dissolving microneedles showed reliable quality and remarkable effect. Moreover, the combination of tranexamic acid and licorice extract had a synergistic therapy in melasma.

Advances in Indocyanine Green-Based Codelivery Nanoplatforms for Combinatorial Therapy

Indocyanine green (ICG), a near-infrared (NIR) agent with an excellent imaging performance, has captivated enormous interest from researchers owing to its excellent therapeutic and imaging abilities. Although various nanoplatforms-based drug delivery systems (DDS) with the ability to overcome the clinical limitations of ICG has been reported, ICG-medicated conventional cancer diagnosis and photorelated therapies still lack in exhibiting the therapeutic efficacy, resulting in incomplete or partly tumor elimination. In the view of addressing these concerns, various DDSs have been engineered for the efficient codelivery of combined therapeutic agents with ICG, aiming to achieve promising therapeutic results due to multifunctional imaging-guided synergistic antitumor effects. In this article, we will systematically review currently available nanoplatforms based on polymers, inorganic, proteins, and metal-organic frameworks (MOFs), among others, for codelivery of ICG along with other therapeutic agents, providing a foundation for future clinical development of ICG. In addition, codelivery systems for ICG and different mechanism-based therapeutic agents will be illustrated. In summary, we conclude the review with the challenges and perspectives of ICG-based versatile nanoplatforms in detail.