Transdermal Composite Microneedle Composed of Mesoporous Iron Oxide Nanoraspberry and PVA for Androgenetic Alopecia Treatment

Advances in magnetic microneedles: From fabrications to applications

Microneedles (MNs) are a new type of physically facilitated penetration technology that not only allows for transdermal drug delivery in a minimally invasive and painless manner, but also serves as a channel for biosignal sensing, demonstrating great potential for application in the medical field. Magnetic materials consist of magnetic elements and their compounds, which can be used for separation, diagnosis, drug delivery and other applications in the fields of medicine, biology and materials. Combining magnetic materials with microneedles can confer magnetic responsiveness to microneedles. Specific strategies for magnetic introduction, corresponding synthetic methods, related applications, and comparisons with other externally stimulus-responsive microneedles are reviewed in this paper on magnetic microneedles. In the end, the limitations of current research and the potential for development of magnetically responsive microneedles are discussed. We hope that the description of magnetic microneedle synthesis methods and related applications in this paper will provide readers with a better understanding of magnetic microneedle systems and inspire the development of novel magnetic microneedle products.

Hyaluronic Acid Microneedles Loaded with Chinese Herbal Extracts as an Intradermal Delivery System for Hair Regeneration

Androgenic alopecia is one of the most common chronic problems for dermatologists worldwide. Some Chinese herbal extracts have been shown to promote hair growth, but the active ingredients are difficult to enter the dermis. Therefore, delivering the active ingredients into the dermis becomes a key factor. Herein, Platycladus orientalis leaf extract (PO-ex) was obtained using ethanol as a solvent, and then hyaluronic acid methacrylate/hyaluronic acid (HAMA/HA) hydrogel was loaded with PO-ex to prepare hyaluronic acid microneedles (PO-ex MN). The double cross-linked HAMA/HA provides sufficient mechanical strength to pierce the stratum corneum and deliver PO-ex into the dermis; PO-ex can effectively improve the environment for hair follicle cell proliferation by removing reactive oxygen free radicals; in addition, the self-repair reaction caused by microneedle mechanical stimulation activates the Wnt/β-catenin pathway associated with trauma repair and promotes hair follicle growth. PO-ex MN is a potential therapeutic strategy for the treatment of androgenic alopecia.

Comparative study of microneedle insertion across different skin models

Microneedles (MNs) enhance drug delivery by painlessly penetrating the stratum corneum, with hardness being crucial for safe insertion. While human/animal skins and synthetic materials are used to test MNs, their variability affects results. Finite element methods (FEM) simulate insertion, but skin model complexity and software limitations cause inconsistencies. This study employs FEM to compare MN performance across skun models under uniform conditions. Results reveal small volume change differences during insertion and rank penetration ease for human/animal models, aiding skin model selection and species-specific MN design optimization.

The Future of Alopecia Treatment: Plant Extracts, Nanocarriers, and 3D Bioprinting in Focus

Alopecia is a concerning dermatological issue and is also known as alopecia. This disease can affect men and women, influencing their confidence and appearance. It targets the scalp or any area of the entire body. Alopecia has become widespread worldwide over the years and has many types and different causes: hereditary, hormonal, immunological, therapeutic, or psychological. This review will present a comprehensive study of the physiological structure of hair and the different growth and shedding phases. It discusses using nano-drug delivery systems that contain natural substances of plant origin, which are effective, less harmful compared to current treatments, and help avoid adverse effects. This review also covers the latest trends in treating alopecia, including drug delivery systems, the materials and methods used to prepare these systems, three-dimensional (3D) bioprinting strategies, and plant extracts that may be utilized for treatment in the coming years.

3D printed microneedles: revamping transdermal drug delivery systems

One of the advancements of the transdermal drug delivery system (TDDS) is the development of microneedles (MNs). These micron-sized needles are used for delivering various types of drugs to address the disadvantage of other transdermal techniques as well as oral drug delivery systems. MNs have high patient acceptance due to self-administration with minimally invasive and pain compared to the parenteral drug delivery. Over the years, various methods have been adopted to evolve the MNs and make them more cost-effective, accurate, and suitable for multiple applications. One such method is the 3D printing of MNs. The development of MN platforms using 3D printing has been made possible by improved features like precision, printing resolution, and the feasibility of using low-cost raw materials. In this review, we have tried to explain various types of MNs, fabrication methods, materials used in the formulation of MNs, and the recent applications that utilize 3D-printed MNs.

Toward precision medicine: End-to-end design and construction of integrated microneedle-based theranostic systems

With the growing demand for precision medicine and advancements in microneedle technology, microneedle-based drug delivery systems have evolved into integrated theranostic platforms. However, the development of these systems is currently limited by the absence of clear conclusions and standardized construction strategies. The end-to-end concept offers an innovative approach to theranostic systems by creating a seamless process that integrates target sampling, sensing, analysis, and on-demand drug delivery. This approach optimizes each step based on data from the others, effectively eliminating the traditional separation between drug delivery and disease monitoring. Furthermore, by incorporating artificial intelligence and machine learning, these systems can enhance reliability and efficiency in disease management, paving the way for more personalized and effective healthcare solutions. Based on the concept of end-to-end and recent advancements in theranostic systems, nanomaterials, electronic components, micro-composites, and data science, we propose a modular strategy for constructing integrated microneedle-based theranostic systems by detailing the methods and functions of each critical component, including monitoring, decision-making, and on-demand drug delivery units, though the total number of units might vary depending on the specific application. Notably, decision-making units are emerging trends for fully automatic and seamless systems and featured for integrated microneedle-based theranostic systems, which serve as a bridge of real-time monitoring, on-demand drug delivery, advanced electronic engineering, and data science for personalized disease management and remote medical application. Additionally, we discuss the challenges and prospects of integrated microneedle-based theranostic systems for precision medicine and clinical application.

Intradermal implantation of methotrexate-loaded puerarin-gelatin hydrogel via bubble-generating microneedles for psoriasis treatment

Methotrexate (MTX) is a primary treatment for moderate to severe psoriasis, but conventional oral or subcutaneous delivery has limitations, including poor drug targeting, side effects, and low patient compliance. This study introduces implantable hydrogel microneedles (HMNs) made from photo-cross-linked gelatin methacryloyl (GelMA) and puerarin (Pue), a traditional Chinese medicine, for intradermal and sustained MTX delivery. The ratio of Pue to GelMA significantly influenced the morphology, mechanical strength, MTX release profiles, and degradation behavior of the HMNs. After insertion into the skin, the backing layer of the microneedles, which incorporates effervescent agents (NaHCO3 and citric acid), rapidly generates gas bubbles (CO₂) upon contact with skin interstitial fluid, facilitating the immediate separation of the HMNs from the backing and their implantation into skin tissue as MTX reservoirs. HMNs with 1.5 % w/v Pue and 20 % w/v GelMA achieved a 10-day MTX release in vivo. In vivo studies demonstrate that MTX-loaded Pue/GelMA HMNs significantly enhance therapeutic outcomes in alleviating psoriasis symptoms and downregulating psoriasis-associated cytokines due to the synergistic effects of MTX and Pue, outperforming oral administration, subcutaneous injection, and GelMA HMNs containing either Pue or MTX alone. This HMN patch offers great promise for improving psoriasis treatment and patient adherence.

Physical stimuli-responsive polymeric patches for healthcare

Many chronic diseases have become severe public health problems with the development of society. A safe and efficient healthcare method is to utilize physical stimulus-responsive polymer patches, which may respond to physical stimuli, including light, electric current, temperature, magnetic field, mechanical force, and ultrasound. Under certain physical stimuli, these patches have been widely used in therapy for diabetes, cancer, wounds, hair loss, obesity, and heart diseases since they could realize controllable treatment and reduce the risks of side effects. This review sketches the design principles of polymer patches, including composition, properties, and performances. Besides, control methods of using different kinds of physical stimuli were introduced. Then, the fabrication methods and characterization of patches were explored. Furthermore, recent applications of these patches in the biomedical field were demonstrated. Finally, we discussed the challenges and prospects for its clinical translation. We anticipate that physical stimulus-responsive polymer patches will open up new avenues for healthcare by acting as a platform with multiple functions.

Transdermal Drug Delivery Systems (TDDS): Recent Advances and Failure Modes

Transdermal drug delivery systems (TDDS), commonly refered to as "patches", present a nonintrusive technique to provide medication without the need for invasive procedures. These products adhere to the skin and gradually release a specific dosage of medicine at a defined rate into the bloodstream. Compared with other methods of drug delivery, TDDS offer benefits such as reduced invasiveness, convenience for patients, and avoidance of the metabolic processes that occur when drugs are orally consumed. Throughout time, TDDS have been used to provide medications for various medical conditions (such as nicotine, fentanyl, nitroglycerin, and clonidine), and their potential for delivering biologics is currently being explored. This review investigates the current literature on the drug delivery efficacy of medical TDDS through the transdermal route. Additionally, the review addresses potential risks and failure modes associated with TDDS design and development as well as strategies for mitigating such risks. A thorough understanding of failure modes provides a blueprint to mitigate failure and produce high-quality efficacious therapeutics.

Micronutrients and Androgenetic Alopecia: A Systematic Review

SCOPE

Hair loss is a common problem that can negatively impact individuals' psychological well-being. Androgenetic alopecia (AGA) is one of the most prevalent types of nonscarring hair loss. This review summarizes the existing evidence on the relationship between AGA and various micronutrients, including vitamin B, vitamin D, vitamin A, vitamin C, iron, selenium, zinc, manganese, and copper.

METHODS

A literature search was conducted to identify relevant articles published between 1993 and 2023. The search identified 49 relevant articles.

RESULTS

The findings suggest that deficiencies or imbalances in these micronutrients may contribute to the pathogenesis of AGA and represent modifiable risk factors for hair loss prevention and treatment. Vitamin B, vitamin D, iron, and zinc appear to play critical roles in hair growth and maintenance. Deficiencies in these micronutrients have been associated with increased risk of AGA, while supplementation with these nutrients has shown potential benefits in improving hair growth and preventing hair loss. However, the current evidence is not entirely consistent, with some studies reporting no significant associations.

CONCLUSION

Deficiencies or imbalances in specific vitamins and minerals, especially vitamin B, vitamin D, Fe, Se, and Zn are involved in the pathogenesis of AGA and may represent modifiable risk factors for the treatment and prevention of this condition.

Advances of Smart Stimulus-Responsive Microneedles in Cancer Treatment

Microneedles (MNs) have emerged as a highly promising technology for delivering drugs via the skin. They provide several benefits, including high drug bioavailability, non-invasiveness, painlessness, and high safety. Traditional strategies for intravenous delivery of anti-tumor drugs have risks of systemic toxicity and easy development of drug resistance, while MN technology facilitates precise delivery and on-demand release of drugs in local tissues. In addition, by further combining with stimulus-responsive materials, the construction of smart stimulus-responsive MNs can be achieved, which can respond to specific physical/chemical stimuli from the internal or external environment, thereby further improving the accuracy of tumor treatment and reducing toxicity to surrounding tissues/cells. This review systematically summarizes the classification, materials, and reaction mechanisms of stimulus-responsive MNs, outlines the benefits and challenges of various types of MNs, and details their application and latest progress in cancer treatment. Finally, the development prospects of smart MNs in tumor treatment are also discussed, bringing inspiration for future precision treatment of tumors.

Fabrication and mechanical modelling of dissolvable PVA/PVP composite microneedles with biocompatibility for efficient transdermal delivery of ibuprofen

Microneedles offer minimally invasive, user-friendly, and subcutaneously accessible transdermal drug delivery and have been widely investigated as an effective transdermal delivery system. Ibuprofen is a common anti-inflammatory drug to treat chronic inflammation. It is crucial to develop microneedle patches capable of efficiently delivering ibuprofen through the skin for the effective treatment of arthritis patients requiring repeated medication. In this study, the mechanical properties of a new type of polymer microneedle were studied by finite element analysis, and the experimental results showed that the microneedle could effectively deliver drugs through the skin. In addition, a high ibuprofen-loaded microneedle patch was successfully prepared by micromolding and subjected to evaluation of its infrared spectrum morphology and dissolve degree. The morphology of microneedles was characterized by scanning electron microscopy, and the mechanical properties were assessed using a built linear stretching system. In the in-vitro diffusion cell drug release test, the microneedle released 85.2 ± 1.52% (210 ± 3.7 μg) ibuprofen in the modified Franz diffusion within 4 h, exhibiting a higher drug release compared to other drug delivery methods. This study provides a portable, safe and efficient treatment approach for arthritis patients requiring daily repeated medication.

Smart Responsive Microneedles for Controlled Drug Delivery

As an emerging technology, microneedles offer advantages such as painless administration, good biocompatibility, and ease of self-administration, so as to effectively treat various diseases, such as diabetes, wound repair, tumor treatment and so on. How to regulate the release behavior of loaded drugs in polymer microneedles is the core element of transdermal drug delivery. As an emerging on-demand drug-delivery technology, intelligent responsive microneedles can achieve local accurate release of drugs according to external stimuli or internal physiological environment changes. This review focuses on the research efforts in smart responsive polymer microneedles at home and abroad in recent years. It summarizes the response mechanisms based on various stimuli and their respective application scenarios. Utilizing innovative, responsive microneedle systems offers a convenient and precise targeted drug delivery method, holding significant research implications in transdermal drug administration. Safety and efficacy will remain the key areas of continuous efforts for research scholars in the future.

Nanotechnology-based techniques for hair follicle regeneration

The hair follicle (HF) is a multicellular complex structure of the skin that contains a reservoir of multipotent stem cells. Traditional hair repair methods such as drug therapies, hair transplantation, and stem cell therapy have limitations. Advances in nanotechnology offer new approaches for HF regeneration, including controlled drug release and HF-specific targeting. Until recently, embryogenesis was thought to be the only mechanism for forming hair follicles. However, in recent years, the phenomenon of wound-induced hair neogenesis (WIHN) or de novo HF regeneration has gained attention as it can occur under certain conditions in wound beds. This review covers HF-specific targeting strategies, with particular emphasis on currently used nanotechnology-based strategies for both hair loss-related diseases and HF regeneration. HF regeneration is discussed in several modalities: modulation of the hair cycle, stimulation of progenitor cells and signaling pathways, tissue engineering, WIHN, and gene therapy. The HF has been identified as an ideal target for nanotechnology-based strategies for hair regeneration. However, some regulatory challenges may delay the development of HF regeneration nanotechnology based-strategies, which will be lastly discussed.

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.

Fabrication of carboxymethyl cellulose/hyaluronic acid/polyvinylpyrrolidone composite pastes incorporation of minoxidil-loaded ferulic acid-derived lignin nanoparticles and valproic acid for treatment of androgenetic alopecia

Androgenetic alopecia (AGA) is a transracial and cross-gender disease worldwide with a higher prevalence among young individuals. Traditional oral or subcutaneous injections are often used to treat AGA, however, they may cause severe side-effects and therefore effective treatments for AGA are currently lacking. In this work, to treat AGA, we developed a composite paste system based on minoxidil (MXD)-loaded nanoparticles and valproic acid (VPA) with the assistance of roller-microneedles (roller-MNs). The matrix of composite paste systems is carboxymethyl cellulose (CMC), hyaluronic acid (HA) and polyvinylpyrrolidone (PVP). The roller-MNs can create microchannels in the skin to enhance drug transdermal efficiency. With the combined effects of the stimulation hair follicle (HF) regrowth by upregulating Wnt/beta-catenin of VPA and the mechanical microchannels induced by roller-MNs, the as-prepared composite paste systems successfully boost perifollicular vascularization, and activate hair follicle stem cells, thereby inducing notably faster hair regeneration at a lower administration frequency on AGA mouse model compared with minoxidil. This approach offers several benefits, including the avoidance of efficacy loss due to the liver's first-pass effect associated with oral drug, reduction in the risk of infection from subcutaneous injection, and significant decrease in the side effects of lower-dose MXD.

Preparation and evaluation of dissolving tofacitinib microneedles for effective management of rheumatoid arthritis

Dissolving microneedles have become a focal point in transdermal drug delivery. They have the advantages of painless, rapid drug delivery and high drug utilization. The purpose of this study was to evaluate the efficacy of Tofacitinib citrate microneedles in arthritis treatment, assess the dose-effect relationship, and determine the cumulative penetration during percutaneous injection. In this study, block copolymer was utilized to prepare the dissolving microneedles. The microneedles were characterized through skin permeation tests, dissolution tests, treatment effect evaluations, and Western blot experiments. In vivo dissolution experiments revealed that the soluble microneedles completely dissolved within 2.5 min, while in vitro skin permeation experiments demonstrated the highest unit area of skin permeation of the microneedles reached 2118.13 mg/cm2. The inhibition of Tofacitinib microneedle on joint swelling in rats with Rheumatoid arthritis was better than Ketoprofen and close to that of oral Tofacitinib. Western-blot experiment comfirmed the Tofacitinib microneedle's inhibitory effect on the JAK-STAT3 pathway in rats with Rheumatoid arthritis. In conclusion, Tofacitinib microneedles effectively inhibited arthritis in rats, demonstrating potential for Rheumatoid arthritis treatment.

Dissolving microneedles for alopecia treatment

Alopecia is a treatable benign disease, however, approximately 15-30% of women and 50% of men suffer from alopecia, which greatly affects patient's self-esteem and quality of life. Currently, commercial products for alopecia treatment include topical minoxidil solution, oral finasteride tablets and oral baricitinib tablets. However, the barrier of stratum corneum, systemic adverse effects and poor cure rate limit the application of commercial products. Therefore, researchers investigated the mechanism of alopecia, and developed new drugs that could target lactate dehydrogenase-related pathways, remove excessive reactive oxygen in hair follicles, and reduce the escape of hair follicle stem cells, thus injecting new strength into the treatment of alopecia. Moreover, starting from improving drug stratum corneum penetration and reducing side effects, researchers have developed hair loss treatment strategies based on dissolved microneedles (MNs), such as drug powders/microparticles, nanoparticles, biomimetic cell membranes, phototherapy and magnetically responsive soluble microneedles, which show exciting alopecia treatment effects. However, there are still some challenges in the practical application of the current alopecia treatment strategy with soluble microneedles, and further studies are needed to accelerate its clinical translation.

Dissolving Microneedle Patch Integrated with Microspheres for Long-Acting Hair Regrowth Therapy

Androgenetic alopecia (AGA) is the most common type of progressive hair loss in both men and women that severely reduces life quality and affects patients' self-esteem. Due to the shortcomings of traditional therapeutic formulations (e.g., topical minoxidil and oral finasteride), such as low bioavailability, frequent dosing, and significant side effects, there is an urgent need to develop a safe and effective strategy for AGA treatment. Here, we report a water-soluble microneedle (MN) patch integrated with biodegradable minoxidil (MXD)-loaded microspheres for long-acting AGA treatment with reduced administration frequency and improved patient compliance. When the patch pierces the skin, the MNs rapidly dissolve and deliver MXD-encapsulated polylactic-co-glycolic acid (PLGA) microspheres into the skin, which, subsequently act as drug reservoirs for the sustained release of the therapeutics for over 2 weeks. Additionally, the application of the MN patch provided a mechanical stimulation on mouse skin, which was also helpful for hair regrowth. Compared with the topical MXD solutions that have been commercialized on the market and require daily application, the long-acting MN patch contains a much lower drug amount and shows a similar or superior hair regeneration effect in AGA mice while only requiring monthly or weekly administration. These encouraging results suggest a simple, safe, and effective strategy for long-acting hair regeneration in clinics.

Research progress of advanced microneedle drug delivery system and its application in biomedicine

Transdermal drug delivery is an effective way of drug delivery in addition to oral and intravenous administration. Among them, microneedle administration is a new type of subcutaneous drug delivery, which forms micron-level pores on the surface of the skin, making the drug enter the dermis through the cuticular layer of the skin in the least invasive way. This mode of drug delivery not only increases the permeation efficiency of transdermal drug delivery but also improves the bioavailability of drug delivery. At present, there are many kinds of research on microneedles, such as solid microneedles, hollow microneedles, soluble polymer microneedles, etc. However, some new microneedle drug delivery systems have been gradually developed and applied with the development of microneedle drug delivery technology, for meeting the more complex pathological environment. In this review, we focus on the principle, structure, and function of some new types of microneedles, such as stimulus-response microneedles, iontophoresis microneedles, and bionic microneedles. We summarize the effects of materials, geometry, and size on the properties of microneedles as well as their applications and potential developments in the field of biomedicine. We hope that this review can provide new ideas and help with the development of new microneedle drug delivery systems.

Advances in microneedles research based on promoting hair regrowth

Alopecia is the most common and difficult-to-treat hair disorder. It usually brings a significant psychological burden to the patients. With the growing popularity of alopecia, the study of alopecia has gained more attention. Currently, only minoxidil and finasteride have been approved by the FDA for the treatment of alopecia, but the efficacy has always been unsatisfactory. As a new form of transdermal drug delivery, microneedles have been widely used in the treatment of alopecia and have proven to be effective. Microneedles delivery can improve the efficiency of local drug delivery and patients' compliance, which can achieve better therapeutic effects on hair-related diseases. Therefore, microneedles have gained much attention in the field of alopecia and hair regrowth promotion in recent years. This review summarizes the last decade of research on the microneedles delivery design for the treatment of alopecia or promotion of hair regrowth and provides a comprehensive evaluation of this field.

A Review of 3D-Printing of Microneedles

Microneedles are micron-sized devices that are used for the transdermal administration of a wide range of active pharmaceutics substances with minimally invasive pain. In the past decade, various additive manufacturing technologies have been used for the fabrication of microneedles; however, they have limitations due to material compatibility and bioavailability and are time-consuming and expensive processes. Additive manufacturing (AM), which is popularly known as 3D-printing, is an innovative technology that builds three-dimensional solid objects (3D). This article provides a comprehensive review of the different 3D-printing technologies that have the potential to revolutionize the manufacturing of microneedles. The application of 3D-printed microneedles in various fields, such as drug delivery, vaccine delivery, cosmetics, therapy, tissue engineering, and diagnostics, are presented. This review also enumerates the challenges that are posed by the 3D-printing technologies, including the manufacturing cost, which limits its viability for large-scale production, the compatibility of the microneedle-based materials with human cells, and concerns around the efficient administration of large dosages of loaded microneedles. Furthermore, the optimization of microneedle design parameters and features for the best printing outcomes is of paramount interest. The Food and Drug Administration (FDA) regulatory guidelines relating to the safe use of microneedle devices are outlined. Finally, this review delineates the implementation of futuristic technologies, such as artificial intelligence algorithms, for 3D-printed microneedles and 4D-printing capabilities.

A Comprehensive Review of Microneedling as a Potential Treatment Option for Androgenetic Alopecia

BACKGROUND

Microneedling refers to a minimally invasive technique that uses multiple fine needles targeted skin epidermis for mechanical stimulation to obtain therapeutic or cosmetic effects. It is suitable for the treatment of a variety of dermatological conditions, including androgenetic alopecia (AGA).

OBJECTIVE

This article aims to make a comprehensive review of the relevant studies on microneedling for the management of AGA.

METHODS

Extensive literature search was performed using PubMed, Web of Science, and EBSCO databases. 4 in vivo studies and 25 clinical trials were included according to the inclusion and exclusion criteria.

RESULTS

The effects of microneedling on AGA was investigated in animal experiments. Several clinical trials, including randomized controlled trials, strengthen the validity of the findings. Microneedling therapy showed some encouraging results with minor complications when used alone or in combination with topical products.

CONCLUSIONS

Microneedling appears to be a safe and effective therapeutic option for AGA. Larger and more randomized controlled trials regarding the role of microneedling in AGA are strongly recommended to provide more definitive evidence.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Promotion of Hair Regrowth by Transdermal Dissolvable Microneedles Loaded with Rapamycin and Epigallocatechin Gallate Nanoparticles

Interest in transdermal delivery methods for stimulating hair regrowth has been increasing recently. The microneedle approach can break the barrier of the stratum corneum through puncture ability and improve drug delivery efficiency. Herein, we report a dissolvable microneedle device for the co-delivery of rapamycin and epigallocatechin gallate nanoparticles that can significantly promote hair regeneration. Compared with the mice without any treatment, our strategy can facilitate hair growth within 7 days. Higher hair shaft growth rate and hair follicle density with inconspicuous inflammation were exhibited in C57BL/6 mice, elucidating its potential for clinical application.

Hair follicle-targeting drug delivery strategies for the management of hair follicle-associated disorders

The hair follicle is not only a critical penetration route in percutaneous absorption but also has been recognized to be a target for hair follicle-associated disorders, such as androgenetic alopecia (AGA) and acne vulgaris. Hair follicle-targeting drug delivery systems allow for controlled drug release and enhance therapeutic efficacy with minimal side effects, exerting a promising method for the management of hair follicle-associated dysfunctions. Therefore, they have obtained much attention in several fields of research in recent years. This review gives an overview of potential follicle-targeting drug delivery formulations currently applied based on the particularities of the hair follicles, including a comprehensive assessment of their preclinical and clinical performance.

Stimuli-Responsive Microneedles as a Transdermal Drug Delivery System: A Demand-Supply Strategy

Microneedles are one of the most prominent approaches capable of physically disrupting the stratum corneum without devastating the deeper tissues to deliver both small molecules and macromolecules into the viable epidermis/dermis for local/systemic effects. Over the past two decades, microneedles have caught the attention of many researchers because of their outstanding advantages over oral and parenteral drug delivery systems such as self-administration, pain-free, steady-plasma concentration maintenance, avoidance of first-pass hepatic biotransformation, and so on. So far, scientists have reported various types of microneedle patches to deliver the loaded therapeutics as soon as the microneedles are inserted into the skin, regardless of the demand for therapeutics to treat a specific condition. This way of drug delivery can lead to potential risks such as poor therapeutic efficacy or drug overdose. The stimuli-responsive microneedles are the most predominant tool to achieve the on-demand/need-based drug delivery, leading to safe and effective treatment. Various natural and synthetic polymers that can undergo significant transitions such as swelling, shrinking, dissolution, or disintegration play a pivotal role in the development of stimuli-responsive microneedles. The current Review provides brief information about the history, emergence, type, and working principles of microneedles. Furthermore, it selectively discusses various exogenous and endogenous stimuli-responsive microneedles along with their mechanism of action involved in treating different disease conditions. Collaterally, the emergence of "closed-loop" combinatorial stimuli-responsive microneedle patches for precise delivery of therapeutics is meticulously canvassed. Subsequently, it covers the patents of different stimuli-responsive microneedles and further highlights the existing challenges and future perspectives concerning clinical application and large-scale production.

Recent progress in three-dimensionally-printed dosage forms from a pharmacist perspective

OBJECTIVE

Additive manufacturing (AM), commonly known as 3D printing (3DP), has opened new frontiers in pharmaceutical applications. This review is aimed to summarise the recent development of 3D-printed dosage forms, from a pharmacists' perspective.

METHODS

Keywords including additive manufacturing, 3D printing and drug delivery were used for literature search in PubMed, Excerpta Medica Database (EMBASE) and Web of Science, to identify articles published in the year 2020.

RESULTS

For each 3DP study, the active pharmaceutical ingredients, 3D printers and materials used for the printing were tabulated and discussed. 3DP has found its applications in various dosage forms for oral delivery, transdermal delivery, rectal delivery, vaginal delivery, implant and bone scaffolding. Several topics were discussed in detail, namely patient-specific dosing, customisable drug administration, multidrug approach, varying drug release, compounding pharmacy, regulatory progress and future perspectives. AM is expected to become a common tool in compounding pharmacies to make polypills and personalised medications.

CONCLUSION

3DP is an enabling tool to fabricate dosage forms with intricate structure designs, tailored dosing, drug combinations and controlled release, all of which lend it to be highly conducive to personalisation, thereby revolutionising the future of pharmacy practice.

Application of microneedle patches for drug delivery; doorstep to novel therapies

In the past decade, microneedle-based drug delivery systems showed promising approaches to become suitable and alternative for hypodermic injections and can control agent delivery without side effects compared to conventional approaches. Despite these advantages, the procedure of microfabrication is facing some difficulties. For instance, drug loading method, stability of drugs, and retention time are subjects of debate. Besides, the application of novel refining fabrication methods, types of materials, and instruments are other issues that need further attention. Herein, we tried to summarize recent achievements in controllable drug delivery systems (microneedle patches) in vitro and in vivo settings. In addition, we discussed the influence of delivered drugs on the cellular mechanism and immunization molecular signaling pathways through the intradermal delivery route. Understanding the putative efficiency of microneedle patches in human medicine can help us develop and design sophisticated therapeutic modalities.

Design and fabrication of hybrid triple-responsive κ-carrageenan-based nanospheres for controlled drug delivery

In the last two decades, the utilization of magnetic nanospheres in intelligent polymeric structures have received increased attention of researchers in numerous biomedical applications. Here, hybrid nanostructured triple-responsive magnetic nanospheres (κ-Car-g-P(AA/DMA)@Fe₃O₄) containing inorganic iron oxide core (Fe₃O₄) and organic graft copolymeric shell based on κ-carrageenan (κ-Car) and poly(acrylic acid/dimethylaminoethyl methacrylate) (P(AA/DMA)) were synthesized by microwave induced co-precipitation technique. The structure, size, surface morphology, magnetic property and stability of synthesized κ-Car-g-P(AA/DMA)@Fe₃O₄ magnetic nanospheres were characterized using FTIR, UV, XRD, TEM, Zeta-sizer, and VSM. κ-Car-g-P(AA/DMA)@Fe₃O₄ nanospheres were loaded with 5-Fluorouracil (5-FU) as an antineoplastic drug, and their 5-FU release behavior was explored in diverse graft yields, pH values, temperatures and in the existence of an alternating magnetic field. The κ-Car-g-P(AA/DMA)@Fe₃O₄ nanospheres demonstrated pH-, thermo-, and magnetic field-responsive 5-FU release with good biocompatibility and excellent anticancer activity. In addition, 5-FU release under 50 mT magnetic field reached to 100% within 4 h. This work exhibits that hybrid nanospheres have a triple stimuli-responsive influence, which is of principal importance for the future design and application of multi-functional responsive platforms to develop externally stimulated release of active agents and their healthcare capability.

Dissolving Microneedles Developed in Association with Nanosystems: A Scoping Review on the Quality Parameters of These Emerging Systems for Drug or Protein Transdermal Delivery

The largest organ of the body provides the main challenge for the transdermal delivery of lipophilic or high molecular weight drugs. To cross the main barrier of the skin, the stratum corneum, many techniques have been developed and improved. In the last 20 years, the association of microneedles with nanostructured systems has gained prominence for its versatility and for enabling targeted drug delivery. Currently, the combination of these mechanisms is pointed to as an emerging technology; however, some gaps need to be answered to transcend the development of these devices from the laboratory scale to the pharmaceutical market. It is known that the lack of regulatory guidelines for quality control is a hindrance to market conquest. In this context, this study undertakes a scoping review of original papers concerning methods applied to evaluate both the quality and drug/protein delivery of dissolving and hydrogel-forming microneedles developed in association with nanostructured systems.

Potential of nanoparticulate based delivery systems for effective management of alopecia

In recent times, more than 50 % of the global population is facing hair-related issues (alopecia) which is seen mostly amongst the people in the age group of 30-40 years. The conventional topical dosage forms available in the market falls short in effectively managing alopecia. Despite various advancements in topical dosage forms, it is still disposed to limited clinical application and provides poor penetration of drug molecules into the skin. The exact etiology of alopecia is still unknown and various researchers link lifestyle, hereditary, and auto immune-based events with its existence. Nanoparticulate-based delivery are hence brought in use to enhance the permeability properties of the drug. In comparison to conventional methods nanotechnology-based drug delivery system tames drug molecules to a specific site with much better efficacy. This review is engrossed in the journey and role of nano technological-based drug delivery in the management of alopecia and its clinical application.

The selection of photoinitiators for photopolymerization of biodegradable polymers and its application in digital light processing additive manufacturing

Digital light processing additive manufacturing (DLP-AM) technology has received a lot of attention in the field of biomedical engineering due to its high precision and customizability. However, some photoinitiators, as one of the key components in DLP-AM, may present toxicity and limit the application of DLP-AM toward biomedical applications. In order to gain further insights into the correlation between biocompatibility and photoinitiators in photoresins, a study on the selection of photoinitiators used in DLP-AM is conducted. The light absorbance range and cytocompatibility of four photoinitiators, vitamin B2 combined with triethanolamine (B2/TEOA), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), 2-dimethoxy-2-phenylacetophenone (DMPA), and 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone (I2959), are characterized. Each photoinitiator is then combined with poly(glycerol sebacate) acrylate (PGSA) and poly(ε-caprolactone) diacrylate (PCLDA), to evaluate their miscibility and film formation ability through photopolymerization. The mechanical properties, in vitro and in vivo biocompatibility studies on bulk films are investigated. It is found that B2/TEOA and TPO exhibit a wider light absorbance range than I2959 and DMPA. PGSA films with B2/TEOA (PGSA-B2/TEOA) is capable of sustaining cell proliferation up to 10 days and showing low immune responses after 14 days post implantation, proving its biocompatibility. Although B2/TEOA requires longer photopolymerization time, the mechanical strength of PGSA-B2/TEOA is comparable to PGSA films with TPO and DMPA, and this combination is 3D-printable through DLP-AM at the rate of 100 s per layer. In summary, B2/TEOA is a promising photoinitiator for 3D printing.

3D Printing-A "Touch-Button" Approach to Manufacture Microneedles for Transdermal Drug Delivery

Microneedles (MNs) represent the concept of attractive, minimally invasive puncture devices of micron-sized dimensions that penetrate the skin painlessly and thus facilitate the transdermal administration of a wide range of active substances. MNs have been manufactured by a variety of production technologies, from a range of materials, but most of these manufacturing methods are time-consuming and expensive for screening new designs and making any modifications. Additive manufacturing (AM) has become one of the most revolutionary tools in the pharmaceutical field, with its unique ability to manufacture personalized dosage forms and patient-specific medical devices such as MNs. This review aims to summarize various 3D printing technologies that can produce MNs from digital models in a single step, including a survey on their benefits and drawbacks. In addition, this paper highlights current research in the field of 3D printed MN-assisted transdermal drug delivery systems and analyzes parameters affecting the mechanical properties of 3D printed MNs. The current regulatory framework associated with 3D printed MNs as well as different methods for the analysis and evaluation of 3D printed MN properties are outlined.

Diving into 3D (bio)printing: A revolutionary tool to customize the production of drug and cell-based systems for skin delivery

The incorporation of 3D printing technologies in the pharmaceutical industry can revolutionize its R&D, by providing a simple and rapid method to produce tailored one-off batches, each with customized dosages, different compounds, shapes, sizes, and adjusted release rates. Particularly, this type of technology can be advantageous for the development of topical and transdermal drug delivery systems, including patches and microneedles. The use of both systems as drug carriers offers advantages over the oral administration, but the possibility of skin irritation and sensitization, and the high production costs, may hinder the expansion of this market. In this context, 3D printing, a high-resolution technique, allows the design of high quality, personalized, complex and sophisticated structures, thus reducing the production costs and improving the patient compliance. This review covers the 3D printing concept and discusses the relevance of this technology to the pharmaceutical industry, with a special focus on the development of topical and transdermal products - patches and microneedles. The potential of 3D bioprinting for skin applications is also presented, highlighting the development of patch-like skin constructs for wound and burn treatment, and skin equivalents for in vitro research and drug development. Several recent studies were selected to support the relevance of the subjects addressed herein. Additionally, the limitations of these printing technologies are discussed, including regulatory, quality and safety issues.

3D printing as a transformative tool for microneedle systems: Recent advances, manufacturing considerations and market potential

The present review aims at identifying the key progress points that have been made on the use of 3D printing to manufacture microneedles in the past 3 years. The advances in the field of photopolymerization and extrusion-based 3D printing are outlined. The study revealed that the printing resolution and the material properties are the two critical parameters that have the most influential effect on the outcome of every microneedle printing endeavour. Finally, the authors attempt to estimate the impact of 3D printing on the transdermal drug delivery market.

Topical Treatment for Scarring and Non-Scarring Alopecia: An Overview of the Current Evidence

Alopecia is a clinical condition related to hair loss that can significantly affect both male and female adults' quality of life. Despite the high market demand, only few drugs are currently approved for alopecia treatment. Topical formulations still bring drawbacks, such as scalp irritation with frequent use, and low drug absorption to the site of action, which limits the efficacy. The most recent research points out that different formulation technology could circumvent the aforementioned flaws. Such technology includes incorporation of drugs in rigid or deformable nanoparticles, strategies involving physical, energetical and mechanical techniques, such as iontophoresis, sonophoresis, microneedling, and the use of solid effervescent granules to be hydrated at the moment of application in the scalp. In this paper, the progress of current research on topical formulations dedicated to the treatment of alopecia is reviewed and discussed.

Transdermal Delivery Systems of Natural Products Applied to Skin Therapy and Care

Natural products are favored because of their non-toxicity, low irritants, and market reacceptance. We collected examples, according to ancient wisdom, of natural products to be applied in transdermal delivery. A transdermal delivery system, including different types of agents, such as ointments, patches, and gels, has long been used for skin concerns. In recent years, many novel transdermal applications, such as nanoemulsions, liposomes, lipid nanoparticles, and microneedles, have been reported. Nanosized drug delivery systems are widely applied in natural product deliveries. Nanosized materials notably enhance bioavailability and solubility, and are reported to improve the transdermal permeation of many substances compared with conventional topical formulations. Natural products have been made into nanosized biomaterials in order to enhance the penetration effect. Before introducing the novel transdermal applications of natural products, we present traditional methods within this article. The descriptions of novel transdermal applications are classified into three parts: liposomes, emulsions, and lipid nanoparticles. Each section describes cases that are related to promising natural product transdermal use. Finally, we summarize the outcomes of various studies on novel transdermal agents applied to skin treatments.

Drug Delivery Applications of Three-Dimensional Printed (3DP) Mesoporous Scaffolds

Mesoporous materials are structures characterized by a well-ordered large pore system with uniform porous dimensions ranging between 2 and 50 nm. Typical samples are zeolite, carbon molecular sieves, porous metal oxides, organic and inorganic porous hybrid and pillared materials, silica clathrate and clathrate hydrates compounds. Improvement in biochemistry and materials science led to the design and implementation of different types of porous materials ranging from rigid to soft two-dimensional (2D) and three-dimensional (3D) skeletons. The present review focuses on the use of three-dimensional printed (3DP) mesoporous scaffolds suitable for a wide range of drug delivery applications, due to their intrinsic high surface area and high pore volume. In the first part, the importance of the porosity of materials employed for drug delivery application was discussed focusing on mesoporous materials. At the end of the introduction, hard and soft templating synthesis for the realization of ordered 2D/3D mesostructured porous materials were described. In the second part, 3DP fabrication techniques, including fused deposition modelling, material jetting as inkjet printing, electron beam melting, selective laser sintering, stereolithography and digital light processing, electrospinning, and two-photon polymerization were described. In the last section, through recent bibliographic research, a wide number of 3D printed mesoporous materials, for in vitro and in vivo drug delivery applications, most of which relate to bone cells and tissues, were presented and summarized in a table in which all the technical and bibliographical details were reported. This review highlights, to a very cross-sectional audience, how the interdisciplinarity of certain branches of knowledge, as those of materials science and nano-microfabrication are, represent a growing valuable aid in the advanced forum for the science and technology of pharmaceutics and biopharmaceutics.

A Semi-Dissolving Microneedle Patch Incorporating TEMPO-Oxidized Bacterial Cellulose Nanofibers for Enhanced Transdermal Delivery

Although dissolving microneedles have garnered considerable attention as transdermal delivery tools, insufficient drug loading remains a challenge owing to their small dimension. Herein, we report a one-step process of synthesizing semi-dissolving microneedle (SDMN) patches that enable effective transdermal drug delivery without loading drugs themselves by introducing TEMPO-oxidized bacterial cellulose nanofibers (TOBCNs), which are well dispersed, while retaining their unique properties in the aqueous phase. The SDMN patch fabricated by the micro-molding of a TOBCN/hydrophilic biopolymer mixture had a two-layer structure comprising a water-soluble needle layer and a TOBCN-containing insoluble backing layer. Moreover, the SDMN patch, which had a hole in the backing layer where TOBCNs are distributed uniformly, could offer novel advantages for the delivery of large quantities of active ingredients. In vitro permeation analysis confirmed that TOBCNs with high water absorption capacity could serve as drug reservoirs. Upon SDMN insertion and the application of drug aqueous solution through the drug inlet hole, the TOBCNs rapidly absorbed the solution and supplied it to the needle layer. Simultaneously, the needle layer dissolved in body fluids and the drug solution to form micro-channels, which enabled the delivery of larger quantities of drugs to the skin compared to that enabled by solution application alone.