Design and characterization of matrix metalloproteinase-responsive hydrogels for the treatment of inflammatory skin diseases

Advances in Drug Delivery Systems for Atopic Dermatitis Treatment

Atopic dermatitis (AD) is a chronic inflammatory skin disorder characterized by pruritus and impaired skin barrier function. Advances in drug delivery systems have transformed AD treatment by enhancing drug stability, bioavailability, and targeted delivery. Drug delivery systems such as liposomes, hydrogels, and microneedles enable deeper skin penetration, prolonged drug retention, and controlled release, reducing side effects and treatment frequency. Liposomes improve drug absorption and stability, while hydrogels offer high water content and responsive drug release. Microneedles facilitate painless, localized drug delivery, enhancing patient compliance. These systems address the limitations of traditional therapies like topical corticosteroids and systemic immunosuppressants, which are associated with adverse effects and poor patient adherence. Recent innovations include Janus kinase (JAK) inhibitors and biologics targeting immune pathways, demonstrating significant efficacy in reducing inflammation and symptoms. Drug delivery systems offer a safer, more efficient alternative for delivering these advanced therapies. By improving therapeutic outcomes and patient experience, drug delivery systems represent a crucial advancement in AD management.

Polysaccharide-based hydrogels for atopic dermatitis management: A review

Atopic dermatitis (AD) is the most common form of eczema and the most burdensome skin disease globally, affecting nearly 223 million. A major AD predisposition is genetic susceptibility, affecting skin barrier integrity and cell-mediated immunity. Manifesting as red, dry, and itchy skin, basic treatment involves skin hydration with emollients. Despite their effectiveness, poor patient compliance remains a major drawback. In severe cases, medicated emollients are used, but carry risks, including skin thinning, and immunosuppression. Hence, hydrogels have emerged as a promising alternative for AD management based on their ability to improve skin hydration, attributed to their hydrophilicity and high water retention capacity. Moreover, researchers have loaded hydrogels with various compounds for AD management; they also hold the potential to reduce systemic side effects of commercial drugs by enhancing dermal retention. Hydrogels address the challenges of patient compliance based on their non-greasy texture and reduced application frequency. Their appeal also stems from their versatility, as they can be fabricated from varying polymers. Due to their abundance, this review focuses on polysaccharides including alginate, cellulose, chitosan, and hyaluronic acid, which are preferred for fabricating natural and modified natural hydrogels for AD. It also briefly explores hydrogel application methods and key AD models.

Hydrogels in Alveolar Bone Regeneration

Alveolar bone defects caused by oral trauma, alveolar fenestration, periodontal disease, and congenital malformations can severely affect oral function and facial aesthetics. Despite the successful clinical applications of bone grafts or bone substitutes, optimal alveolar bone regeneration continues to be challenging due to the complex oral environment and its unique physiological functions. Hydrogels that serve as promising candidates for tissue regeneration are under development to meet the specific needs for increased bone regeneration capacity and improved operational efficiency in alveolar bone repair. In this review, we emphasize the considerations in hydrogel design for alveolar bone regeneration and summarize the latest applications of hydrogels in prevalent clinical diseases related to alveolar bone defects. The future perspectives and challenges for the application of hydrogels in the field of alveolar bone regeneration are also discussed. Deepening our understanding of these biomaterials will facilitate the advent of novel inventions to improve the outcome of alveolar bone tissue regeneration.

Matrix metalloproteinase landscape in the imiquimod-induced skin inflammation mouse model

Inflammation and autoimmunity are known as central processes in many skin diseases, including psoriasis. It is therefore important to develop pre-clinical models that describe disease-related aspects to enable testing of pharmaceutical drug candidates and formulations. A widely accepted pre-clinical model of psoriasis is the imiquimod (IMQ)-induced skin inflammation mouse model, where topically applied IMQ provokes local skin inflammation. In this study, we investigated the abundance of a subset of matrix metalloproteinases (MMPs) in skin from mice with IMQ-induced skin inflammation and skin from naïve mice using targeted proteomics. Our findings reveal a significant increase in the abundance of MMP-2, MMP-7, MMP-8, and MMP-13 after treatment with IMQ compared to the control skin, while MMP-3, MMP-9, and MMP-10 were exclusively detected in the IMQ-treated skin. The increased abundance and broader representation of MMPs in the IMQ-treated skin provide valuable insight into the pathophysiology of skin inflammation in the IMQ model, adding to previous studies on cytokine levels using conventional immunochemical methods. Specifically, the changes in the MMP profiles observed in the IMQ-treated skin resemble the MMP patterns found in skin lesions of individuals with psoriasis. Ultimately, the differences in MMP abundance under IMQ-induced inflammation as compared to non-inflamed control skin can be exploited as a model to investigate drug efficacy or performance of drug delivery systems.

Inflammation environment-adaptive matrix confinement for three-dimensional modulation of macrophages

The balance of macrophages in immune reactions is crucial for tissue repair. Despite some studies on responsive surfaces for immunomodulation regulation of macrophage phenotypes via external stimuli, 2D and manual interventions are limited. Herein, to address these limitations, we developed an inflammation environment-responsive macrophage-laden hydrogel-filled scaffold for investigating the impact of matrix confinement on macrophage phenotypes adaptively. We fabricated gelatin scaffolds with a controllable pore size and found that macrophages within smaller pores tended to have an anti-inflammation phenotype. We prepared poly(vinyl alcohol) (PVA)-based hydrogels crosslinked with phenylboronic acid (PBA)-based linkers. The hydrogels possessed shear-thinning, cell-loading, and ROS-sensitive-degradation abilities. Subsequently, a macrophage-laden hydrogel-filled scaffold was fabricated by filling the hydrogels into the porous scaffold under vacuum. With the degradation of the hydrogels under the overexpression of ROS in an inflammation environment, the macrophages were transferred from a state with strong matrix confinement to that with a weaker one. Meanwhile, with the change in matrix confinement, the macrophages upregulated the expressions of Arg-1 and IL-10 and downregulated the expressions of IL-1β, TNF-α, and IL-6, indicating polarization toward the anti-inflammatory phenotype. The inflammation environment-adaptive modulation of macrophage phenotypes in 3D provides a smart and biomimetic strategy for immunomodulation and regenerative medicine.

Stimuli-responsive drug delivery systems for inflammatory skin conditions

Inflammatory skin conditions highly influence the quality of life of the patients suffering from these disorders. Symptoms include red, itchy and painful skin lesions, which are visible to the rest of the world, causing stigmatization and a significantly lower mental health of the patients. Treatment options are often unsatisfactory, as they suffer from either low patient adherence or the risk of severe side effects. Considering this, there is a need for new treatments, and notably of new ways of delivering the drugs. Stimuli-responsive drug delivery systems are able to deliver their drug cargo in response to a given stimulus and are, thus, promising for the treatment of inflammatory skin conditions. For example, the use of external stimuli such as ultraviolet light, near infrared radiation, or alteration of magnetic field enables drug release to be precisely controlled in space and time. On the other hand, internal stimuli induced by the pathological condition, including pH alteration in the skin or upregulation of reactive oxygen species or enzymes, can be utilized to create drug delivery systems that specifically target the diseased skin to achieve a better efficacy and safety. In the latter context, however, it is of key importance to match the trigger mechanism of the drug delivery system to the actual pathological features of the specific skin condition. Hence, the focus of this article is placed not only on reviewing stimuli-responsive drug delivery systems developed to treat specific inflammatory skin conditions, but also on critically evaluating their efficacy in the context of specific skin diseases. STATEMENT OF SIGNIFICANCE: Skin diseases affect one-third of the world's population, significantly lowering the quality of life of the patients, who deal with symptoms such as painful and itchy skin lesions, as well as stigmatization due to the visibility of their symptoms. Current treatments for inflammatory skin conditions are often hampered by low patient adherence or serious drug side effects. Therefore, more emphasis should be placed on developing innovative formulations that provide better efficacy and safety for patients. Stimuli-responsive drug delivery systems hold considerable promise in this regard, as they can deliver their cargo precisely where and when it is needed, reducing adverse effects and potentially offering better treatment outcomes.

Advancing inflammatory skin disease therapy: Sustained tofacitinib release via electrospun fiber dressings

Inflammatory skin diseases are typically managed with semi-solid formulations such as creams and ointments. These treatments often fail to remain on the skin for long, as they can be easily wiped off by clothing, necessitating frequent reapplication throughout the day and resulting in poor patient adherence. Therefore, this study sought to fabricate an electrospun dressing as an alternative dosage form that provides a sustained release of the anti-inflammatory agent tofacitinib over three days. In this study, three types of electrospun fiber dressings - uniaxial, coaxial, and layer-by-layer - were produced and examined for their morphological, mechanical, and release characteristics. In addition to a comprehensive characterization, another objective was to analyze the drug permeation behavior from these fiber dressings on porcine skin, comparing their performance to that of a tofacitinib cream. The layer-by-layer system notably exhibited a delayed drug release, while the uniaxial and coaxial systems demonstrated an initial burst release. However, the permeation studies revealed no significant differences between these systems, underscoring the necessity of conducting such studies - a crucial aspect often overlooked in research on electrospun fiber dressings. Overall, this study highlights the potential of electrospun, drug-loaded dressings for the treatment of inflammatory skin diseases.

Hydrogels: a promising therapeutic platform for inflammatory skin diseases treatment

Inflammatory skin diseases, such as psoriasis and atopic dermatitis, pose significant health challenges due to their long-lasting nature, potential for serious complications, and significant health risks, which requires treatments that are both effective and exhibit minimal side effects. Hydrogels offer an innovative solution due to their biocompatibility, tunability, controlled drug delivery capabilities, enhanced treatment adherence and minimized side effects risk. This review explores the mechanisms that guide the design of hydrogel therapeutic platforms from multiple perspectives, focusing on the components of hydrogels, their adjustable physical and chemical properties, and their interactions with cells and drugs to underscore their clinical potential. We also examine various therapeutic agents for psoriasis and atopic dermatitis that can be integrated into hydrogels, including traditional drugs, novel compounds targeting oxidative stress, small molecule drugs, biologics, and emerging therapies, offering insights into their mechanisms and advantages. Additionally, we review clinical trial data to evaluate the effectiveness and safety of hydrogel-based treatments in managing psoriasis and atopic dermatitis under complex disease conditions. Lastly, we discuss the current challenges and future opportunities for hydrogel therapeutics in treating psoriasis and atopic dermatitis, such as improving skin barrier penetration and developing multifunctional hydrogels, and highlight emerging opportunities to enhance long-term safety and stability.

Hydrogel-exosome system in tissue engineering: A promising therapeutic strategy

Characterized by their pivotal roles in cell-to-cell communication, cell proliferation, and immune regulation during tissue repair, exosomes have emerged as a promising avenue for "cell-free therapy" in clinical applications. Hydrogels, possessing commendable biocompatibility, degradability, adjustability, and physical properties akin to biological tissues, have also found extensive utility in tissue engineering and regenerative repair. The synergistic combination of exosomes and hydrogels holds the potential not only to enhance the efficiency of exosomes but also to collaboratively advance the tissue repair process. This review has summarized the advancements made over the past decade in the research of hydrogel-exosome systems for regenerating various tissues including skin, bone, cartilage, nerves and tendons, with a focus on the methods for encapsulating and releasing exosomes within the hydrogels. It has also critically examined the gaps and limitations in current research, whilst proposed future directions and potential applications of this innovative approach.

Design and evaluation of an MMP-9-responsive hydrogel for vital pulp therapy

OBJECTIVE

To design and evaluate a matrix metalloproteinase 9 (MMP-9)-responsive hydrogel for vital pulp therapy.

METHODS

A peptide linker with optimized sensitivity toward MMP-9 was crosslinked with 4-arm poly (ethylene glycol)-norbornene (PEG-NB) by thiol-norbornene photo-polymerization. This resulted in the formation of a hydrogel network in which the peptide IDR-1002 was incorporated. Hydrogel characterization and gelation kinetics were examined with Fourier-transform infrared spectroscopy, scanning electron microscopy, rheological testing, and swelling evaluation. Hydrogel degradation was examined through multiple exposure to pre-activated MMP-9, to simulate flare-ups of dental pulp inflammation. The IDR-1002 released from degraded hydrogels was measured with high-performance liquid chromatography. Effect of IDR-1002 released from hydrogels on one-week-old multispecies oral biofilms was evaluated using confocal laser scanning microscopy.

RESULTS

MMP-9-responsive, injectable, and photo-crosslinkable hydrogels were successfully synthesized. When hydrogel degradation and release of IDR-1002 were examined with exposure to pre-activated MMP-9, IDR-1002 release was significantly correlated with elevated levels of MMP-9 (p < 0.05). The effectiveness of IDR-1002 in killing bacteria in multispecies oral biofilms was significantly enhanced when the hydrogels were immersed in 10 nM or 20 nM pre-activated MMP-9, compared to immersion in phosphate-buffered saline (p < 0.05).

CONCLUSIONS

The MMP-9-responsive hydrogel is a promising candidate for on-demand delivery of bioactive agent in vital pulp therapy.

CLINICAL SIGNIFICANCE

MMP-9 is one of the most important diagnostic and prognostic biomarkers for pulpitis. An MMP-9-responsive hydrogel has potential to be used as an in-situ on-demand release system for the diagnosis and treatment of dental pulp inflammation.

Local and Sustained Baricitinib Delivery to the Skin through Injectable Hydrogels Containing Reversible Thioimidate Adducts

Janus kinase (JAK) inhibitors are approved for many dermatologic disorders, but their use is limited by systemic toxicities including serious cardiovascular events and malignancy. To overcome these limitations, injectable hydrogels are engineered for the local and sustained delivery of baricitinib, a representative JAK inhibitor. Hydrogels are formed via disulfide crosslinking of thiolated hyaluronic acid macromers. Dynamic thioimidate bonds are introduced between the thiolated hyaluronic acid and nitrile-containing baricitinib for drug tethering, which is confirmed with 1H and 13C nuclear magnetic resonance (NMR). Release of baricitinib is tunable over six weeks in vitro and active in inhibiting JAK signaling in a cell line containing a luciferase reporter reflecting interferon signaling. For in vivo activity, baricitinib hydrogels or controls are injected intradermally into an imiquimod-induced mouse model of psoriasis. Imiquimod increases epidermal thickness in mice, which is unaffected when treated with baricitinib or hydrogel alone. Treatment with baricitinib hydrogels suppresses the increased epidermal thickness in mice treated with imiquimod, suggesting that the sustained and local release of baricitinib is important for a therapeutic outcome. This study is the first to utilize a thioimidate chemistry to deliver JAK inhibitors to the skin through injectable hydrogels, which has translational potential for treating inflammatory disorders.

Smart Hydrogels for Tissue Regeneration

The rapid growth in the portion of the aging population has led to a consequent increase in demand for biomedical hydrogels, together with an assortment of challenges that need to be overcome in this field. Smart hydrogels can autonomously sense and respond to the physiological/pathological changes of the tissue microenvironment and continuously adapt the response according to the dynamic spatiotemporal shifts in conditions. This along with other favorable properties, make smart hydrogels excellent materials for employing toward improving the precision of treatment for age-related diseases. The key factor during the smart hydrogel design is on accurately identifying the characteristics of natural tissues and faithfully replicating the composition, structure, and biological functions of these tissues at the molecular level. Such hydrogels can accurately sense distinct physiological and external factors such as temperature and biologically active molecules, so they may in turn actively and promptly adjust their response, by regulating their own biological effects, thereby promoting damaged tissue repair. This review summarizes the design strategies employed in the creation of smart hydrogels, their response mechanisms, as well as their applications in field of tissue engineering; and concludes by briefly discussing the relevant challenges and future prospects.

Stimuli-responsive peptide hydrogels for biomedical applications

Stimuli-responsive hydrogels can respond to external stimuli with a change in the network structure and thus have potential application in drug release, intelligent sensing, and scaffold construction. Peptides possess robust supramolecular self-assembly ability, enabling spontaneous formation of nanostructures through supramolecular interactions and subsequently hydrogels. Therefore, peptide-based stimuli-responsive hydrogels have been widely explored as smart soft materials for biomedical applications in the last decade. Herein, we present a review article on design strategies and research progress of peptide hydrogels as stimuli-responsive materials in the field of biomedicine. The latest design and development of peptide hydrogels with responsive behaviors to stimuli are first presented. The following part provides a systematic overview of the functions and applications of stimuli-responsive peptide hydrogels in tissue engineering, drug delivery, wound healing, antimicrobial treatment, 3D cell culture, biosensors, etc. Finally, the remaining challenges and future prospects of stimuli-responsive peptide hydrogels are proposed. It is believed that this review will contribute to the rational design and development of stimuli-responsive peptide hydrogels toward biomedical applications.

Photo-Controllable Smart Hydrogels for Biomedical Application: A Review

Nowadays, smart hydrogels are being widely studied by researchers because of their advantages such as simple preparation, stable performance, response to external stimuli, and easy control of response behavior. Photo-controllable smart hydrogels (PCHs) are a class of responsive hydrogels whose physical and chemical properties can be changed when stimulated by light at specific wavelengths. Since the light source is safe, clean, simple to operate, and easy to control, PCHs have broad application prospects in the biomedical field. Therefore, this review timely summarizes the latest progress in the PCHs field, with an emphasis on the design principles of typical PCHs and their multiple biomedical applications in tissue regeneration, tumor therapy, antibacterial therapy, diseases diagnosis and monitoring, etc. Meanwhile, the challenges and perspectives of widespread practical implementation of PCHs are presented in biomedical applications. This study hopes that PCHs will flourish in the biomedical field and this review will provide useful information for interested researchers.

Tofacitinib in dermatology: a potential opportunity for topical applicability through novel drug-delivery systems

Tofacitinib is a first-generation JAK inhibitor approved by the US FDA for treating rheumatoid arthritis. It exhibits a broad-spectrum inhibitory effect with abilities to block JAK-STAT signalling. The primary objective of this review is to obtain knowledge about cutting-edge methods for effectively treating a variety of skin problems by including tofacitinib into formulations that are based on nanocarriers. The review also highlights clinical trials and offers an update on published clinical patents. Nanocarriers provide superior performance compared to conventional treatments in terms of efficacy, stability, drug bioavailability, target selectivity and sustained drug release. Current review has the potential to make significant contributions to the ongoing discussion involving dermatological treatments and the prospective impact of nanotechnology on transforming healthcare within this field.

Protease-Responsive Hydrogel Microparticles for Intradermal Drug Delivery

Protease-responsive multi-arm polyethylene glycol-based microparticles with biscysteine peptide crosslinkers (CGPGG↓LAGGC) were obtained for intradermal drug delivery through inverse suspension photopolymerization. The average size of the spherical hydrated microparticles was ∼40 μm after crosslinking, making them attractive as a skin depot and suitable for intradermal injections, as they are readily dispensable through 27G needles. The effects of exposure to matrix metalloproteinase 9 (MMP-9) on the microparticles were evaluated by scanning electron microscopy and atomic force microscopy, demonstrating partial network destruction and decrease in elastic moduli. Given the recurring course of many skin diseases, the microparticles were exposed to MMP-9 in a flare-up mimicking fashion (multiple-time exposure), showing a significant increase in release of tofacitinib citrate (TC) from the MMP-responsive microparticles, which was not seen for the non-responsive microparticles (polyethylene glycol dithiol crosslinker). It was found that the degree of multi-arm complexity of the polyethylene glycol building blocks can be utilized to tune not only the release profile of TC but also the elastic moduli of the hydrogel microparticles, with Young's moduli ranging from 14 to 140 kPa going from 4-arm to 8-arm MMP-responsive microparticles. Finally, cytotoxicity studies conducted with skin fibroblasts showed no reduction in metabolic activity after 24 h exposure to the microparticles. Overall, these findings demonstrate that protease-responsive microparticles exhibit the properties of interest for intradermal drug delivery.

Microporous Implants Modified by Bifunctional Hydrogel with Antibacterial and Osteogenic Properties Promote Bone Integration in Infected Bone Defects

Prosthesis implantation and bone integration under bacterial infection are arduous challenges in clinical practice. It is well known that the reactive oxygen species (ROS) produced by bacterial infection around the bone defects will further hinder bone healing. To solve this problem, we prepared a ROS-scavenging hydrogel by cross-linking polyvinyl alcohol and a ROS-responsive linker, N¹-(4-boronobenzyl)-N³-(4-boronophenyl)-N¹, N¹, N³, N³-tetramethylpropane-1, 3-diaminium, to modify the microporous titanium alloy implant. The prepared hydrogel was used as an advanced ROS-scavenging tool to promote bone healing by inhibiting the ROS levels around the implant. Bifunctional hydrogel serving as a drug delivery system can release therapeutic molecules, including vancomycin, to kill bacteria and bone morphogenetic protein-2 to induce bone regeneration and integration. This multifunctional implant system that combines mechanical support and disease microenvironment targeting provides a novel strategy for bone regeneration and integration of implants in infected bone defects.