Bio-inspired swellable hydrogel-forming double-layered adhesive microneedle protein patch for regenerative internal/external surgical closure

Bilayer Hydrogels for Wound Dressing and Tissue Engineering

A large number of different skin diseases such as hits, acute, and chronic wounds dictate the search for alternative and effective treatment options. The wound healing process requires a complex approach, the key step of which is the choice of a dressing with controlled properties. Hydrogel-based scaffolds can serve as a unique class of wound dressings. Presented on the commercial market, hydrogel wound dressings are not found among proposals for specific cases and have a number of disadvantages—toxicity, allergenicity, and mechanical instability. Bilayer dressings are attracting great attention, which can be combined with multifunctional properties, high criteria for an ideal wound dressing (antimicrobial properties, adhesion and hemostasis, anti-inflammatory and antioxidant effects), drug delivery, self-healing, stimulus manifestation, and conductivity, depending on the preparation and purpose. In addition, advances in stem cell biology and biomaterials have enabled the design of hydrogel materials for skin tissue engineering. To improve the heterogeneity of the cell environment, it is possible to use two-layer functional gradient hydrogels. This review summarizes the methods and application advantages of bilayer dressings in wound treatment and skin tissue regeneration. Bilayered hydrogels based on natural as well as synthetic polymers are presented. The results of the in vitro and in vivo experiments and drug release are also discussed.

Recent Advances in Intelligent Wearable Medical Devices Integrating Biosensing and Drug Delivery

The primary roles of precision medicine are to perform real-time examination, administer on-demand medication, and apply instruments continuously. However, most current therapeutic systems implement these processes separately, leading to treatment interruption and limited recovery in patients. Personalized healthcare and smart medical treatment have greatly promoted research on and development of biosensing and drug-delivery integrated systems, with intelligent wearable medical devices (IWMDs) as typical systems, which have received increasing attention because of their non-invasive and customizable nature. Here, the latest progress in research on IWMDs is reviewed, including their mechanisms of integrating biosensing and on-demand drug delivery. The current challenges and future development directions of IWMDs are also discussed.

Construction of multifunctional wound dressings with their application in chronic wound treatment

As the prevalence of diabetes increases year by year and the aging population continues to intensify in the world, chronic wounds such as diabetic foot ulcers and pressure ulcers have become serious problems that threaten people's health, and have brought an enormous burden to the world healthcare system. Conventional clinical treatment of chronic wounds relies on non-specific topical care (including debridement, infection/inflammation control, and frequent wound dressing changes), which can alleviate disease progression and reduce patient suffering to a certain extent, but the overall cure rate is less than 50% and the recurrence rate is high. Traditional wound dressings such as gauze, hydrocolloids, films and foams are single-function, acting as a physical barrier or absorbing exudates, and cannot meet all the needs of the entire chronic wound healing process. Recently, a large number of novel functional dressings have been reported for chronic wound repair. Based on the progress on wound dressings in recent years and the relevant research experience of our group, the review summarizes and discusses the progress on multifunctional wound dressings (such as microneedles, sponges and hydrogels) with anti-inflammatory, antioxidant, antibacterial, pro-angiogenic and tissue adhesive functions in detail. At the same time, the various responsive mechanisms (in vivo microenvironment or in vitro stimulation) of the smart multifunctional wound dressing are also analyzed in detail. It is expected that the review could provide some inspiration and suggestions for research on dressings for chronic wound treatment.

Comparison of Surgical Outcomes of Laparoscopic Glue and Laparoscopic Suture Hernioplasty in Pediatric Female Inguinal Hernia

This study aimed to report the surgical outcomes of laparoscopic glue hernioplasty (LGH) compared with conventional laparoscopic suture hernioplasty (LSH) in pediatric female inguinal hernia repair. We retrospectively analyzed 465 female pediatric patients who underwent laparoscopic inguinal hernia repair between January 2013 and December 2020. LGH and LSH were performed in 95 and 370 cases, respectively. Surgical outcomes (length of hospital stay, operative time, complications, and recurrences) were compared between the LGH and LSH groups. We found that the operation times for bilateral hernia repair were shorter in the LGH group (LGH: 35.5 ± 8.2 min, LSH: 45.2 ± 11.6 min; p < 0.001). No significant differences in complications or recurrences were observed between the two groups during the follow-up period. Our findings suggest that LGH is a feasible and easily applied surgical technique for the treatment of pediatric female inguinal hernia.

Responsive hydrogel-based microneedle dressing for diabetic wound healing

Wound healing is a critical challenge in diabetic patients, mainly due to long-term dysglycemia and its related pathological complications. Subcutaneous insulin injection represents a typical clinical solution, while the low controllability of insulin administration commonly leads to a result far from the optimal therapeutic effect. In this work, we developed a glucose-responsive insulin-releasing hydrogel for microneedle dressing fabrication and then investigated its effects on diabetic wound healing. The hydrogel system was composed of biocompatible gelatin methacrylate (GelMa), glucose-responsive monomer 4-(2-acrylamidoethylcarbamoyl)-3-fluorophenylboronic acid (AFPBA) and gluconic insulin (G-insulin), and the Gel-AFPBA-ins hydrogel-based microneedle dressing was developed by replicating PDMS molds. The resultant hydrogel microneedle dressing exhibited adequate mechanical properties, high biocompatibility, glucose-responsive insulin release behavior upon exposure to different glucose solutions, and potent adhesion to the skin compared to hydrogels without microstructures. The microneedle dressing could accelerate the diabetic wound healing process with decreased inflammatory reaction, enhanced collagen deposition on the regenerated tissue sites, and improved blood glucose control in animals. Therefore, the glucose-responsive insulin-releasing hydrogel microneedle dressing is effective in diabetic wound management and has potential for treatment of other chronic skin injuries.

Dissolving microneedle-encapsulated drug-loaded nanoparticles and recombinant humanized collagen type III for the treatment of chronic wound via anti-inflammation and enhanced cell proliferation and angiogenesis

Nowadays, diabetic chronic wounds impose a heavy burden on patients and the medical system. Persistent inflammation and poor tissue remodeling severely limit the healing of chronic wounds. For these issues, the first recombinant humanized collagen type III (rhCol III) and naproxen (Nap) loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticle incorporated hyaluronic acid (HA) microneedle (MN) was fabricated for diabetic chronic wound therapy. As the tailored rhCol III was synthesized based on the Gly483-Pro512 segment, which contained the highly adhesive fragments (GER, GEK) in the human collagen type III sequence, it possessed strong cell adhesion. The mechanical strength of the prepared MN was enough to overcome the tissue barrier of necrosis/hyperkeratosis in a minimally invasive way after being applied in wounds. Subsequently, rhCol III and Nap@PLGA nanoparticles were rapidly released to the wound site within a few minutes. The prepared MN possessed favourable biocompatibility and could effectively facilitate the proliferation and migration of fibroblasts and endothelial cells. Furthermore, the regenerative efficacy of the MN was evaluated in vivo using the diabetic rat full-thickness skin wound model. These results illustrated that the prepared MN could accelerate wound closure by reducing the inflammatory response and enhancing angiogenesis or collagen deposition, indicating their significant application value in wound dressings for chronic wound repair.

Microneedle-based insulin transdermal delivery system: current status and translation challenges

Diabetes mellitus is a metabolic disease manifested by hyperglycemia. For patients with type 1 and advanced type 2 diabetes mellitus, insulin therapy is essential. Subcutaneous injection remains the most common administration method. Non-invasive insulin delivery technologies are pursued because of their benefits of decreasing patients' pain, anxiety, and stress. Transdermal delivery systems have gained extensive attention due to the ease of administration and absence of hepatic first-pass metabolism. Microneedle (MN) technology is one of the most promising tactics, which can effectively deliver insulin through skin stratum corneum in a minimally invasive and painless way. This article will review the research progress of MNs in insulin transdermal delivery, including hollow MNs, dissolving MNs, hydrogel MNs, and glucose-responsive MN patches, in which insulin dosage can be strictly controlled. The clinical studies about insulin delivery with MN devices have also been summarized and grouped based on the study phase. There are still several challenges to achieve successful translation of MNs-based insulin therapy. In this review, we also discussed these challenges including safety, efficacy, patient/prescriber acceptability, manufacturing and scale-up, and regulatory authority acceptability.

Double-layered adhesive microneedle bandage based on biofunctionalized mussel protein for cardiac tissue regeneration

Heart failure following myocardial infarction (MI), the primary cause of mortality worldwide, is the consequence of cardiomyocyte death or dysfunction. Clinical efforts involving the delivery of growth factors (GFs) and stem cells with the aim of regenerating cardiomyocytes for the recovery of structural and functional integrity have largely failed to deliver, mainly due to short half-lives and rapid clearance in in vivo environments. In this work, we selected and genetically fused four biofunctional peptides possessing angiogenic potential, originating from extracellular matrix proteins and GFs, to bioengineered mussel adhesive protein (MAP). We found that MAPs fused with vascular endothelial growth factor (VEGF)-derived peptide and fibronectin-derived RGD peptide significantly promoted the proliferation and migration of endothelial cells in vitro. Based on these characteristics, we fabricated advanced double-layered adhesive microneedle bandages (DL-AMNBs) consisting of a biofunctional MAP-based root and a regenerated silk fibroin (SF)-based tip, allowing homogeneous distribution of the regenerative factor via swellable microneedles. Our developed DL-AMNB system clearly demonstrated better preservation of cardiac muscle and regenerative effects on heart remodeling in a rat MI model, which might be attributed to the prolonged retention of therapeutic peptides as well as secure adhesion between the patch and host myocardium by MAP-inherent strong underwater adhesiveness.

Advances of Microneedles in Biomedical Applications

A microneedle (MN) is a painless and minimally invasive drug delivery device initially developed in 1976. As microneedle technology evolves, microneedles with different shapes (cone and pyramid) and forms (solid, drug-coated, hollow, dissolvable and hydrogel-based microneedles) have been developed. The main objective of this review is the applications of microneedles in biomedical areas. Firstly, the classifications and manufacturing of microneedle are briefly introduced so that we can learn the advantages and fabrications of different MNs. Secondly, research of microneedles in biomedical therapy such as drug delivery systems, diagnoses of disease, as well as wound repair and cancer therapy are overviewed. Finally, the safety and the vision of the future of MNs are discussed.

Functional Hydrogels as Wound Dressing to Enhance Wound Healing

Hydrogels, due to their excellent biochemical and mechnical property, have shown attractive advantages in the field of wound dressings. However, a comprehensive review of the functional hydrogel as a wound dressing is still lacking. This work first summarizes the skin wound healing process and relates evaluation parameters and then reviews the advanced functions of hydrogel dressings such as antimicrobial property, adhesion and hemostasis, anti-inflammatory and anti-oxidation, substance delivery, self-healing, stimulus response, conductivity, and the recently emerged wound monitoring feature, and the strategies adopted to achieve these functions are all classified and discussed. Furthermore, applications of hydrogel wound dressing for the treatment of different types of wounds such as incisional wound and the excisional wound are summarized. Chronic wounds are also mentioned, and the focus of attention on infected wounds, burn wounds, and diabetic wounds is discussed. Finally, the future directions of hydrogel wound dressings for wound healing are further proposed.

Microneedles for drug delivery: recent advances in materials and geometry for preclinical and clinical studies

INTRODUCTION

A microneedle array patch (MAP) has been studied as a means for delivering drugs or vaccines and has shown superior delivery efficiency compared to the conventional transdermal drug delivery system (TDD). This paper reviews recent advancements in the development of MAPs, with a focus on their size, shapes, and materials in preclinical and clinical studies for pharmaceutics.

AREA COVERED

We classified MAPs for drug delivery into four types: coated, dissolving, separable, and swellable. We covered their recent developments in materials and geometry in preclinical and clinical studies.

EXPERT OPINION

The design of MAPs needs to be determined based on what properties would be effective for the target diseases and purposes. In addition, in preclinical studies, it is necessary to consider not only the novelty of the formulations but also the feasibility of clinical application. Currently, clinical studies of microneedles loaded with various drugs and vaccines are in progress. When the regulation of pharmaceutical microneedles is established and more clinical studies are published, more drugs will be developed as microneedle products and clinical research will proceed. With these considerations, the microneedle array patch will be a better option for drug delivery.

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.

MXene-Integrated Microneedle Patches with Innate Molecule Encapsulation for Wound Healing

Wound healing is a complex physiological process that involves coordinated phases such as inflammation and neovascularization. Attempts to promote the healing process tend to construct an effective delivery system based on different drugs and materials. In this paper, we propose novel MXene-integrated microneedle patches with adenosine encapsulation for wound healing. Owing to the dynamic covalent bonding capacity of boronate molecules with adenosine, 3-(acrylamido)phenylboronic acid- (PBA-) integrated polyethylene glycol diacrylate (PEGDA) hydrogel is utilized as the host material of microneedle patches. Benefitting from photothermal conversion capacity of MXene, the release of loaded adenosine could be accelerated under NIR irradiation for maintaining the activation signal around injury site. In vitro cell experiments proved the effect of MXene-integrated microneedle patches with adenosine encapsulation in enhancing angiogenesis. When applied for treating animal models, it is demonstrated that the microneedle patches efficiently promote angiogenesis, which is conductive to wound healing. These features make the proposed microneedle patch potential for finding applications in wound healing and other biomedical fields.

Multifaceted Design and Emerging Applications of Tissue Adhesives

Tissue adhesives can form appreciable adhesion with tissues and have found clinical use in a variety of medical settings such as wound closure, surgical sealants, regenerative medicine, and device attachment. The advantages of tissue adhesives include ease of implementation, rapid application, mitigation of tissue damage, and compatibility with minimally invasive procedures. The field of tissue adhesives is rapidly evolving, leading to tissue adhesives with superior mechanical properties and advanced functionality. Such adhesives enable new applications ranging from mobile health to cancer treatment. To provide guidelines for the rational design of tissue adhesives, here, existing strategies for tissue adhesives are synthesized into a multifaceted design, which comprises three design elements: the tissue, the adhesive surface, and the adhesive matrix. The mechanical, chemical, and biological considerations associated with each design element are reviewed. Throughout the report, the limitations of existing tissue adhesives and immediate opportunities for improvement are discussed. The recent progress of tissue adhesives in topical and implantable applications is highlighted, and then future directions toward next-generation tissue adhesives are outlined. The development of tissue adhesives will fuse disciplines and make broad impacts in engineering and medicine.

Zn-MOF Encapsulated Antibacterial and Degradable Microneedles Array for Promoting Wound Healing

An infected skin wound caused by external injury remains a serious challenge in clinical practice. Wound dressings with the properties of antibacterial activity and potent regeneration capacity are highly desirable for wound healing. In this paper, a degradable, ductile, and wound-friendly Zn-MOF encapsulated methacrylated hyaluronic acid (MeHA) microneedles (MNs) array is fabricated through the molding method for promoting wound healing. Due to the damage capability against the bacteria capsule and oxidative stress of the zinc ion released from the Zn-MOF, such MNs array presents excellent antibacterial activity, as well as considerable biocompatibility. Besides, the degradable MNs array composed of photo-crosslinked MeHA possesses the superior capabilities to continuously and steadily release the loaded active ingredients and avoid secondary damage to the wound. Moreover, the low molecular weight hyaluronic acid (HA) generated by hydrolysis of MeHA is also conducive to tissue regeneration. Benefiting from these features, it has been demonstrated that the Zn-MOF encapsulated degradable MNs array can dramatically accelerate epithelial regeneration and neovascularization. These results indicate that the combination of MOFs and degradable MNs array is of great value for promoting wound healing.

Emerging Functional Biomaterials as Medical Patches

Medical patches have been widely explored and applied in various medical fields, especially in wound healing, tissue engineering, and other biomedical areas. Benefiting from emerging biomaterials and advanced manufacturing technologies, great achievements have been made on medical patches to evolve them into a multifunctional medical device for diverse health-care purposes, thus attracting extensive attention and research interest. Here, we provide up-to-date research concerning emerging functional biomaterials as medical patches. An overview of the various approaches to construct patches with micro- and nanoarchitecture is presented and summarized. We then focus on the applications, especially the biomedical applications, of the medical patches, including wound healing, drug delivery, and real-time health monitoring. The challenges and prospects for the future development of the medical patches are also discussed.

Recent advances in mechanical force-assisted transdermal delivery of macromolecular drugs

The transdermal delivery of macromolecular drugs has become one of the focused topics in pharmaceutical research since it enables highly specific and effective delivery, while avoiding the pain and needle phobia associated with injection, or incidences like drug degradation and low bioavailability of oral administration. However, the passive absorption of macromolecular drugs via skin is highly restricted by the stratum corneum owing to high molecular weight. Therefore, various strategies have been extensively developed and conducted to facilitate the transdermal delivery of macromolecular drugs, among which, mechanical force-assisted techniques occupy dominant positions. Such techniques include ultrasound, needle-free jet injection, temporary pressure and microneedles. In this review, we focus on recent transdermal enhancing strategies utilizing mechanical force, and summarize their mechanisms, advantages, limitations and clinical applications respectively.

Microneedles for painless transdermal immunotherapeutic applications

Immunotherapy has recently garnered plenty of attention to improve the clinical outcomes in the treatment of various diseases. However, owing to the dynamic nature of the immune system, this approach has often been challenged by concerns regarding the lack of adequate long-term responses in patients. The development of microneedles (MNs) has resulted in the improvement and expansion of immuno-reprogramming strategies due to the housing of high accumulation of dendritic cells, macrophages, lymphocytes, and mast cells in the dermis layer of the skin. In addition, MNs possess many outstanding properties, such as the ability for the painless traverse of the stratum corneum, minimal invasiveness, facile fabrication, excellent biocompatibility, convenient administration, and bypassing the first pass metabolism that allows direct translocation of therapeutics into the systematic circulation. These advantages make MNs excellent candidates for the delivery of immunological biomolecules to the dermal antigen-presenting cells in the skin with the aim of vaccinating or treating different diseases, such as cancer and autoimmune disorders, with minimal invasiveness and side effects. This review discusses the recent advances in engineered MNs and tackles limitations relevant to traditional immunotherapy of various hard-to-treat diseases.

Microneedle arrays for the treatment of chronic wounds

INTRODUCTION

Chronic wounds are seen frequently in diabetic and bedbound patients. Such skin injuries, which do not heal in a timely fashion, can lead to life-threatening conditions. In an effort to resolve the burdens of chronic wounds, numerous investigations have explored the efficacy of various therapeutics on wound healing. Therapeutics can be topically delivered to cutaneous wounds to reduce the complications associated with systemic drug delivery because the compromised skin barrier is not expected to negatively affect drug distribution. However, researchers have recently demonstrated that the complex environment of chronic wounds could lower the localized availability of the applied therapeutics. Microneedle arrays (MNAs) can be exploited to enhance delivery efficiency and consequently improved healing.

AREAS COVERED

In this review, we briefly describe the pathophysiology of chronic wounds and current treatment strategies. We further introduce methods and materials commonly used for the fabrication of MNAs. Subsequently, the studies demonstrating the benefits of MNAs in wound care are highlighted.

EXPERT OPINION

Microneedles have great potential to treat the complicated pathophysiology of chronic wounds. Challenges that will need to be addressed include development of a robust chronic wound model and MNAs that combine complex functionality with simplicity of use.

Hydrogel-Forming Microneedles: Current Advancements and Future Trends

In this focused progress review, the recent developments and trends of hydrogel-forming microneedles (HFMs) and potential future directions are presented. Previously, microneedles (solid, hollow, coated, and dissolving microneedles) have primarily been used to enhance the effectiveness of transdermal drug delivery to facilitate a wide range of applications such as vaccinations and antibiotic delivery. However, the recent trend in microneedle development has resulted in microneedles formed from hydrogels which have the ability to offer transdermal drug delivery and, due to the hydrogel swelling nature, passively extract interstitial fluid from the skin, meaning they have the potential to be used for biocompatible minimally invasive monitoring devices. Thus, in this review, these recent trends are highlighted, which consolidate microneedle design considerations, hydrogel formulations, fabrication processes, applications of HFMs and the potential future opportunities for utilizing HFMs for personalized healthcare monitoring and treatment.

Polymeric-based microneedle arrays as potential platforms in the development of drugs delivery systems

BACKGROUND

Microscopic patches as quite promising platforms in transdermal drug delivery suffer from conventional injections. In other hand, a wide range of pharmacokinetics, ranging from fast oral administration to sustained drug delivery, can be implemented with the help of microneedle arrays (MNAs).

AIM OF REVIEW

Hence, in this paper, we overviewed different kinds of MNAs such as solid/coated, hollow, porous, hydrogel/swellable, and merged-tip geometry followed by introducing different types of material (silicon, glass, ceramics, dissolving and biodegradable polymers, and hydrogel) used for fabrication of MNAs. Afterwards, some conventional and brand-new simple and customizable MN mold fabrication techniques were surveyed. Polymeric MNAs have received a great deal of attention due to their potential biocompatibility and biodegradability in comparison to other materials. Therefore, we also covered different kinds of polymers such as hydrogel/swellable, dissolving and biodegradable analogues used for the development of MNAs as potential candidates in drug delivery systems (DDSs). Finally, we discussed different challenges and future perspectives in the aspect of MNAs-based drug delivery platforms.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review may provide guidelines for the rational design of polymeric MNAs-based DDSs for promising programmable drug release and enhanced therapeutic effect.

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.

Stimuli-Responsive Hydrogels for Local Post-Surgical Drug Delivery

Currently, surgical operations, followed by systemic drug delivery, are the prevailing treatment modality for most diseases, including cancers and trauma-based injuries. Although effective to some extent, the side effects of surgery include inflammation, pain, a lower rate of tissue regeneration, disease recurrence, and the non-specific toxicity of chemotherapies, which remain significant clinical challenges. The localized delivery of therapeutics has recently emerged as an alternative to systemic therapy, which not only allows the delivery of higher doses of therapeutic agents to the surgical site, but also enables overcoming post-surgical complications, such as infections, inflammations, and pain. Due to the limitations of the current drug delivery systems, and an increasing clinical need for disease-specific drug release systems, hydrogels have attracted considerable interest, due to their unique properties, including a high capacity for drug loading, as well as a sustained release profile. Hydrogels can be used as local drug performance carriers as a means for diminishing the side effects of current systemic drug delivery methods and are suitable for the majority of surgery-based injuries. This work summarizes recent advances in hydrogel-based drug delivery systems (DDSs), including formulations such as implantable, injectable, and sprayable hydrogels, with a particular emphasis on stimuli-responsive materials. Moreover, clinical applications and future opportunities for this type of post-surgery treatment are also highlighted.

A Double-Layered Microneedle Platform Fabricated through Frozen Spray-Coating

This work reports a frozen spray-coating method for the fabrication of double-layered microneedles (MNs). Taking swellable methacrylated hyaluronic acid (MeHA)-derived MNs as the model, both hydrophobic molecules (Nile red, Cy5) and hydrophilic ones (FITC, FITC-Dextran, Insulin) can be homogeneously coated without impacting the mechanical properties of the original MeHA MNs. The prepared double-layered MNs can execute multiple roles. It is demonstrated that insulin-coated MeHA double-layered MNs allow the effective delivery of the insulin into circulation of mice for controlling the blood glucose level while they also permit the extraction of skin interstitial fluid for the timely analysis of the biomarker (glucose).

Progress in Microneedle-Mediated Protein Delivery

The growing demand for patient-compliance therapies in recent years has led to the development of transdermal drug delivery, which possesses several advantages compared with conventional methods. Delivering protein through the skin by transdermal patches is extremely difficult due to the presence of the stratum corneum which restricts the application to lipophilic drugs with relatively low molecular weight. To overcome these limitations, microneedle (MN) patches, consisting of micro/miniature-sized needles, are a promising tool to perforate the stratum corneum and to release drugs and proteins into the dermis following a non-invasive route. This review investigates the fabrication methods, protein delivery, and translational considerations for the industrial scaling-up of polymeric MNs for dermal protein delivery.

Smart Microneedles for Therapy and Diagnosis

Microneedles represent a cutting-edge and idea-inspiring technology in biomedical engineering, which have attracted increasing attention of scientific researchers and medical staffs. Over the past decades, numerous great achievements have been made. The fabrication process of microneedles has been simplified and becomes more precise, easy-to-operate, and reusable. Besides, microneedles with various features have been developed and the microneedle materials have greatly expanded. In recent years, efforts have been focused on generating smart microneedles by endowing them with intriguing functions such as adhesion ability, responsiveness, and controllable drug release. Such improvements enable the microneedles to take an important step in practical applications including household drug delivery devices, wearable biosensors, biomedical assays, cell culture, and microfluidic chip analysis. In this review, the fabrication strategies, distinctive properties, and typical applications of the smart microneedles are discussed. Recent accomplishments, remaining challenges, and future prospects are also presented.