Skin-penetrating polymeric nanoparticles incorporated in silk fibroin hydrogel for topical delivery of curcumin to improve its therapeutic effect on psoriasis mouse model

Exploring the Therapeutic Potential of Natural Compounds in Psoriasis and Their Inclusion in Nanotechnological Systems

Psoriasis is a chronic inflammatory disease that affects around 2-3% of the world's population. The treatment for this autoimmune disease still remains centered around conventional methods using synthetic substances, even though more recent advancements focus on biological therapies. Given the numerous side effects of such treatments, current research involves plant extracts and constituents that could prove useful in treating psoriasis. The aim of this narrative review is to highlight the most known representatives belonging to classes of natural compounds such as polyphenols (e.g., astilbin, curcumin, hesperidin, luteolin, proanthocyanidins, and resveratrol), alkaloids (e.g., berberine, capsaicin, and colchicine), coumarins (psoralen and 8-methoxypsoralen), and terpenoids (e.g., celastrol, centelloids, and ursolic acid), along with plants used in traditional medicine that could present therapeutic potential in psoriasis. The paper also provides an overview of these compounds' mechanisms of action and current inclusion in clinical studies, as well as an investigation into their potential incorporation in various nanotechnological systems, such as lipid-based nanocarriers or polymeric nanomaterials, that may optimize their efficacy during treatment.

Superb Silk Hydrogels with High Adaptability, Bioactivity, and Versatility Enabled by Photo-Cross-Linking

The exceptional biocompatibility and adaptability of hydrogels have garnered significant interest in the biomedical field for the fabrication of biomedical devices. However, conventional synthetic hydrogels still exhibit relatively weak and fragile properties. Drawing inspiration from the photosynthesis process, we developed a facile approach to achieve a harmonious combination of superior mechanical properties and efficient preparation of silk fibroin hydrogel through photo-cross-linking technology, accomplished within 60 s. The utilization of riboflavin and H2O2 enabled a sustainable cyclic photo-cross-linking reaction, facilitating the transformation from tyrosine to dityrosine and ultimately contributing to the formation of highly cross-linked hydrogels. These photo-cross-linking hydrogels exhibited excellent elasticity and restorability even after undergoing 1000 cycles of compression. Importantly, our findings presented that hydrogel-encapsulated adipose stem cells possess the ability to stimulate cell proliferation along with stem cell stemness. This was evidenced by the continuous high expression levels of OCT4 and SOX2 over 21 days. Additionally, the utilization of photo-cross-linking hydrogels can be extended to various material molding platforms, including microneedles, microcarriers, and bone screws. Consequently, this study offered a significant approach to fabricating biomedical hydrogels capable of facilitating real-time cell delivery, thereby introducing an innovative avenue for designing silk devices with exceptional machinability and adaptability in biomedical applications.

Recent Approaches for the Topical Treatment of Psoriasis Using Nanoparticles

Psoriasis (PSO) is a chronic autoimmune skin condition characterized by the rapid and excessive growth of skin cells, which leads to the formation of thick, red, and scaly patches on the surface of the skin. These patches can be itchy and painful, and they may cause discomfort for patients affected by this condition. Therapies for psoriasis aim to alleviate symptoms, reduce inflammation, and slow down the excessive skin cell growth. Conventional topical treatment options are non-specific, have low efficacy and are associated with adverse effects, which is why researchers are investigating different delivery mechanisms. A novel approach to drug delivery using nanoparticles (NPs) shows promise in reducing toxicity and improving therapeutic efficacy. The unique properties of NPs, such as their small size and large surface area, make them attractive for targeted drug delivery, enhanced drug stability, and controlled release. In the context of PSO, NPs can be designed to deliver active ingredients with anti-inflammatory effect, immunosuppressants, or other therapeutic compounds directly to affected skin areas. These novel formulations offer improved access to the epidermis and facilitate better absorption, thus enhancing the therapeutic efficacy of conventional anti-psoriatic drugs. NPs increase the surface-to-volume ratio, resulting in enhanced penetration through the skin, including intracellular, intercellular, and trans-appendage routes. The present review aims to discuss the latest approaches for the topical therapy of PSO using NPs. It is intended to summarize the results of the in vitro and in vivo examinations carried out in the last few years regarding the effectiveness and safety of nanoparticles.

Chitosan hydrogels with MK2 inhibitor peptide-loaded nanoparticles to treat atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disorder that lacks ideal long-term treatment options due to a series of side effects, such as skin atrophy, related to the most common treatment prescribed to manage moderate-to-severe AD. In this study, a cell-penetrating MK2 inhibitor peptide YARA (YARAAARQARAKALNRQGLVAA) was loaded into hollow thermo-responsive pNIPAM nanoparticles (NP), which were further incorporated into chitosan hydrogels (H-NP-YARA) to promote local drug delivery, improve moisture and the anti-inflammatory activity. The NPs exhibited high loading efficiency (>50%) and the hydrogel remained porous following NP incorporation as observed by scanning electron microscopy (SEM). Both nanoparticles and hydrogels were able to improve the release of YARA and sustained release to up to 120 h. The hydrogels and NPs delivered 2 and 4-fold more YARA into viable skin layers of porcine skin in vitro at 12 h post-application than the non-encapsulated compound in intact and impaired barrier conditions. Furthermore, the YARA-loaded NPs (NP-YARA) and H-NP-YARA treatment decreased the levels of inflammatory cytokines up to 20 time-fold compared with the non-treated group of human keratinocytes under inflammatory conditions. Consistent with the results in cell culture, the loading of YARA in NP reduced the levels of IL-1β, IL-6, and TNF-α up to 3.3 times in an ex vivo skin culture model after induction of inflammation. A further decrease of up to 17 times-fold was observed with H-NP-YARA treatment compared to the drug in solution. Our data collectively suggest that chitosan hydrogel containing YARA-loaded nanoparticles is a promising new formulation for the topical treatment of AD.

State-of-the-art advances in nanocomposite and bio-nanocomposite polymeric materials: A comprehensive review

The modern eco-friendly materials used in research and innovation today consist of nanocomposites and bio-nanocomposite polymers. Their unique composite properties make them suitable for various industrial, medicinal, and energy applications. Bio-nanocomposite polymers are made of biopolymer matrices that have nanofillers dispersed throughout them. There are several types of fillers that can be added to polymers to enhance their quality, such as cellulose-based fillers, clay nanomaterials, carbon black, talc, carbon quantum dots, and many others. Biopolymer-based nanocomposites are considered a superior alternative to traditional materials as they reduce reliance on fossil fuels and promote the use of renewable resources. This review covers the current state-of-the-art in nanocomposite and bio-nanocomposite materials, focusing on ways to improve their features and the various applications they can be used for. The review article also investigates the utilization of diverse nanocomposites as a viable approach for developing bio-nanocomposites. It delves into the underlying principles that govern the synthesis of these materials and explores their prospective applications in the biomedical field, food packaging, sensing (Immunosensors), and energy storage devices. Lastly, the review discusses the future outlook and current challenges of these materials, with a focus on sustainability.

Recent developments in natural biopolymer based drug delivery systems

Targeted delivery of drug molecules to diseased sites is a great challenge in pharmaceutical and biomedical sciences. Fabrication of drug delivery systems (DDS) to target and/or diagnose sick cells is an effective means to achieve good therapeutic results along with a minimal toxicological impact on healthy cells. Biopolymers are becoming an important class of materials owing to their biodegradability, good compatibility, non-toxicity, non-immunogenicity, and long blood circulation time and high drug loading ratio for both macros as well as micro-sized drug molecules. This review summarizes the recent trends in biopolymer-based DDS, forecasting their broad future clinical applications. Cellulose chitosan, starch, silk fibroins, collagen, albumin, gelatin, alginate, agar, proteins and peptides have shown potential applications in DDS. A range of synthetic techniques have been reported to design the DDS and are discussed in the current study which is being successfully employed in ocular, dental, transdermal and intranasal delivery systems. Different formulations of DDS are also overviewed in this review article along with synthesis techniques employed for designing the DDS. The possibility of these biopolymer applications points to a new route for creating unique DDS with enhanced therapeutic qualities for scaling up creative formulations up to the clinical level.

Microemulsion-Based Keratin-Chitosan Gel for Improvement of Skin Permeation/Retention and Activity of Curcumin

Curcumin (Cur) is a kind of polyphenol with a variety of topical pharmacological properties including antioxidant, analgesic and anti-inflammatory activities. However, its low water solubility and poor skin bioavailability limit its effectiveness. In the current study, we aimed to develop microemulsion-based keratin-chitosan gel for the improvement of the topical activity of Cur. The curcumin-loaded microemulsion (CME) was formulated and then loaded into the keratin-chitosan (KCS) gel to form the CME-KCS gel. The formulated CME-KCS gel was evaluated for its characterization, in vitro release, in vitro skin permeation and in vivo activity. The results showed that the developed CME-KCS gel had an orange-yellow and gel-like appearance. The particle size and zeta potential of the CME-KCS gel were 186.45 ± 0.75 nm and 9.42 ± 0.86 mV, respectively. The CME-KCS gel showed desirable viscoelasticity, spreadability, bioadhesion and controlled drug release, which was suitable for topical application. The in vitro skin permeation and retention study showed that the CME-KCS gel had better in vitro skin penetration than the Cur solution and achieved maximum skin drug retention (3.75 ± 0.24 μg/cm²). In vivo experimental results confirmed that the CME-KCS gel was more effective than curcumin-loaded microemulsion (Cur-ME) in analgesic and anti-inflammatory activities. In addition, the CME-KCS gel did not cause any erythema or edema based on a mice skin irritation test. These findings indicated that the developed CME-KCS gel could improve the skin penetration and retention of Cur and could become a promising formulation for topical delivery to treat local diseases.

An overview of topical lipid-based and polymer-based nanocarriers for treatment of psoriasis

Psoriasis is a consistently recurring, inflammatory skin disease, affecting about 2 - 5 % of the world population. Different types of psoriasis can be observed such as guttate psoriasis, pustular psoriasis, psoriatic arthritis, scalp psoriasis, flexural psoriasis etc. Several therapeutic approaches are available for the treatment of psoriasis. However, none of them are entirely safe and effective to treat the disease without compromising patient compliance. The traditional treatment plan is associated with harmful side effects such asimmune system suppression and damage of essential organs at high doses, which poses a challenge to treat psoriasis. Novel drug delivery systems are being developed to replace traditional therapy in order to address these shortcomings. Currently, nanoformulations have gained widespread application for treatment of psoriasis. Researchers have developed different types of lipid-based nanoparticles like liposomes, niosomes, ethosomes, transethosomes, nanostructured lipid carriers and solid lipid nanoparticles. These innovative formulations provide advantages in terms of reduction in dose, dosing frequency, dose-dependency with enhanced efficacy, improved encapsulation efficiency, controlled release, increased surface area, high bioavailability and greater stratum corneum permeability. This review highlights detailed and comparative discussion of lipid-based and polymer-based nanoparticles for psoriasis along with the pathophysiology and other treatments of psoriasis.

Next-Generation Hydrogels as Biomaterials for Biomedical Applications: Exploring the Role of Curcumin

Since the first report on the pharmacological activity of curcumin in 1949, enormous amounts of research have reported diverse activities for this natural polyphenol found in the dietary spice turmeric. However, curcumin has not yet been used for human application as an approved drug. The clinical translation of curcumin has been hampered due to its low solubility and bioavailability. The improvement in bioavailability and solubility of curcumin can be achieved by its formulation using drug delivery systems. Hydrogels with their biocompatibility and low toxicity effects have shown a substantial impact on the successful formulation of hydrophobic drugs for human clinical trials. This review focuses on hydrogel-based delivery systems for curcumin and describes its applications as anti-cancer as well as wound healing agents.

Can Essential Oils/Botanical Agents Smart-Nanoformulations Be the Winning Cards against Psoriasis?

Although psoriasis remains one of the most devastating inflammatory disorders due to its huge negative impact on patients’ quality of life, new “green” treatment approaches still need to be fully explored. The purpose of this review article is to focus on the utilization of different essential oils and active constituents of herbal botanical origin for the treatment of psoriasis that proved efficacious via both in vitro and in vivo models. The applications of nanotechnology-based formulations which displayed great potential in augmenting the permeation and delivery of these agents is also addressed. Numerous studies have been found which assessed the potential activity of natural botanical agents to overcome psoriasis. Nano-architecture delivery is applied in order to maximize the benefits of their activity, improve properties, and increase patient compliance. This field of natural innovative formulations can be a promising tool to optimize remediation of psoriasis while minimizing adverse effects.

Silk Nanocarrier with Tunable Size to Improve Transdermal Capacity for Hydrophilic and Hydrophobic Drugs

Transdermal drug delivery is an attractive option for multiple disease therapies as it reduces adverse reactions and improves patient compliance. Water-dispersible β-sheet rich silk nanofiber carriers have hydrophobic properties that benefit transdermal delivery but still show inferior transdermal capacities. Thus, hydrophobic silk nanofibers were fabricated to fine-tune their size and endow them with desirable transdermal delivery capacities. Silk nanocarrier length was shortened from 2000 nm to approximately 40 nm after ultrasonic treatment. In vitro human skin and in vivo animal studies revealed different transdermal behaviors for silk nanocarriers at different nanosizes. Silk nanocarriers passed slowly through the corneum without destroying the corneum structure. Improved transdermal capacity was achieved for smaller size carriers. Both hydrophilic and hydrophobic drugs could be loaded onto silk nanocarriers, suggesting a promising future for different disease therapies. No cytotoxicity and skin irritation were identified for silk nanocarriers, which strengthened their superiority as transdermal carriers. Therefore, silk nanocarriers <100 nm may promote the percutaneous absorption of active cargos for disease therapy and cosmetic applications.

Nanoscale Topical Pharmacotherapy in Management of Psoriasis: Contemporary Research and Scope

Psoriasis is a typical dermal condition that has been anticipated since prehistoric times when it was mistakenly implicit in being a variant of leprosy. It is an atypical organ-specific autoimmune disorder, which is triggered by the activation of T-cells and/or B-cells. Until now, the pathophysiology of this disease is not completely explicated and still, many research investigations are ongoing. Different approaches have been investigated to treat this dreadful skin disease using various anti-psoriatic drugs of different modes of action through smart drug-delivery systems. Nevertheless, there is no ideal therapy for a complete cure of psoriasis owing to the dearth of an ideal drug-delivery system for anti-psoriatic drugs. The conventional pharmacotherapy approaches for the treatment of psoriasis demand various classes of anti-psoriatic drugs with optimum benefit/risk ratio and insignificant untoward effects. The advancement in nanoscale drug delivery had a great impact on the establishment of a nanomedicine-based therapy for better management of psoriasis in recent times. Nanodrug carriers are exploited to design and develop nanomedicine-based therapy for psoriasis. It has a promising future in the improvement of the therapeutic efficacy of conventional anti-psoriatic drugs. The present manuscript aims to discuss the pathophysiology, conventional pharmacotherapy, and contemporary research in the area of nanoscale topical drug delivery systems for better management of psoriasis including the significance of targeted pharmacotherapy in psoriasis.

The Therapeutic Effect of Tacrolimus in a Mouse Psoriatic Model is Associated with the Induction of Myeloid-derived Suppressor Cells

Objectives

Topical administration of Tacrolimus (TAC) is efective in the treatment of psoriasis in human patients and in mouse models. Previously, we showed that, though promoting the proliferative expansion of CD4⁺Foxp3⁺ regulatory T cells (Tregs), TNFR2 was protective in mouse psoriasis model. We thus examined the role of TNFR2 signal in the efect of TAC in the treatment of mouse psoriasis.

Methods

To this end, psoriasis was induced in WT, or TNFR1 KO, or TNFR2 KO mice, and the psoriatic mice were treated with or without IMQ.

Results

The results showed that TAC treatment potently inhibited the development of psoriasis in WT and TNFR1 KO mice, but not in TNFR2 KO mice. However, the treatment of TAC failed to induce the expansion of Tregs in psoriatic mice. In addition to playing a decisive role in the activation of Tregs, TNFR2 stimulates the generation and activation of myeloid-derived suppressor cells (MDSCs). This led us to found that the topical treatment with TAC markedly increased the number of MDSCs in the spleen of WT and TNFR1 KO mice, but not in TNFR2 KO mice. Consequently, TAC potently decreased serum levels of IL-17A, INF-γ, and TNF and their mRNA levels in the inflamed skin lesion.

Conclusion

Therefore, our study for the first time found that the therapeutic efect of TAC in psoriasis is associated with the expansion of MDSCs in a TNFR2-dependent manner.

Novel Herbal Nanocarriers for Treatment of Dermatological Disorders

BACKGROUND AND OBJECTIVE

In the present scenario, the use of novel nanocarriers to provide a better therapy regimen is noteworthy. Nanotechnology with the advanced system enables the herbs for encapsulation within the smart carrier and boosts the nanotherapeutic. These emerging innovations of herbal nanocarriers have paved the way for dermal targeting by eliciting the desired response for particular diseases.

METHODS

In this current manuscript, an extensive search is conducted for the original research papers using databases, viz., Google Scholar, PubMed, Science Direct, etc. Furthermore, painstaking efforts are made to compile and update the novel herbal nanocarriers, such as liposomes, ethosomes, transferosomes, niosomes, nanoemulsions, nanogels, nanostructured lipid carriers, solid lipid carriers, etc., which are mostly used for the treatment of several skin maladies, viz., eczema, psoriasis, acne, etc. This article highlights the recent findings that the innovators are exclusively working on herbal drug delivery systems for dermal targeting, and these are enumerated in the form of tables.

CONCLUSION

Herbal formulations employing a suitable nanocarrier could be a promising approach for the treatment of several pathological conditions, including skin ailments. Therefore, scientific research is still being carried out in this specific area for a better perspective in herbal drug delivery and targeting.

A double-edged sword: ROS related therapies in the treatment of psoriasis

In the onset and progression of psoriasis, redox imbalance is a vital factor. It's widely accepted that too much reactive oxygen species (ROS) always make psoriasis worse. Recent research, however, has shown that the accumulation of ROS is not entirely detrimental, as it helps reduce psoriasis lesions by inhibiting epidermal proliferation and keratinocyte death. As a result, ROS appears to have two opposing effects on the treatment of psoriasis. In this review, the current ROS-related therapies for psoriasis, including basic and clinical research, are presented. Additionally, the design and therapeutic benefits of various drug delivery systems and therapeutic approaches are examined, and a potential balance between anti-oxidative stress and ROS accumulation is also trying to be investigated.

Silk peptide-hyaluronic acid based nanogels for the enhancement of the topical administration of curcumin

The present study focused on the development of Cur-loaded SOHA nanogels (Cur-SHNGs) to enhance the topical administration of Cur. The physiochemical properties of Cur-SHNGs were characterized. Results showed that the morphology of the Cur-SHNGs was spherical, the average size was 171.37 nm with a zeta potential of −13.23 mV. Skin permeation experiments were carried out using the diffusion cell systems. It was found that the skin retention of Cur-SHNGs was significantly improved since it showed the best retention value (0.66 ± 0.17 μg/cm²). In addition, the hematoxylin and eosin staining showed that the Cur-SHNGs improved transdermal drug delivery by altering the skin microstructure. Fluorescence imaging indicated that Cur-SHNGs could effectively deliver the drug to the deeper layers of the skin. Additionally, Cur-SHNGs showed significant analgesic and anti-inflammatory activity with no skin irritation. Taken together, Cur-SHNGs could be effectively used for the topical delivery of therapeutic drugs.

Efficacy and safety of curcumin in psoriasis: preclinical and clinical evidence and possible mechanisms

Background: Psoriasis is a chronic and immune-mediated inflammatory skin disease. Many studies have shown that curcumin (CUR) has strong anti-inflammatory effects and can improve psoriasis; however, its efficacy and safety have not been confirmed, and the specific mechanism remains to be elucidated.

Objective: To evaluate the efficacy, safety, and possible mechanisms of CUR in the treatment of psoriasis.

Methods: The Cochrane Library, Embase, PubMed, Web of Science, China National Knowledge Infrastructure, Wanfang, and VIP (China Science and Technology Journal Database) were systematically searched for clinical trials and preclinical studies on the use of CUR in psoriasis treatment. All databases were searched from inception to January 2022. The meta-analysis was performed using RevMan 5.3 software.

Results: Our meta-analysis included 26 studies, comprising seven clinical randomized controlled trials and 19 preclinical studies. A meta-analysis of clinical trials showed that both CUR monotherapy and combination therapy improved Psoriasis Area and Severity Index (PASI) scores in patients compared to controls (standard mean difference [std.MD]: −0.83%; 95% confidence interval [CI]: −1.53 to 0.14; p = 0.02). In preclinical studies, CUR showed better performance in improving the phenotype of psoriatic dermatitis mice compared to controls, including total PASI score (std.MD: 6.50%; 95% CI: 10.10 to −2.90; p = 0.0004); ear thickness (p = 0.01); and the expression of inflammatory cytokines such as interleukin (IL)-17, tumor necrosis factor (TNF)-α, IL-17F, and IL-22 (p < 0.05). In cell studies, CUR inhibited cell proliferation (p = 0.04) and the cell cycle (p = 0.03) and downregulated the inflammatory cytokines IL-6 and IL-8 (p < 0.05).

Conclusions: CUR has excellent efficacy and broad potential to treat psoriasis in multiple ways. Its use also plays a crucial role in improving the psoriasis phenotype and reducing the inflammatory microenvironment. In conclusion, our findings suggest that CUR alone or in combination with other conventional treatments can effectively treat psoriasis.

Latest on biomaterial-based therapies for topical treatment of psoriasis

Psoriasis is an autoimmune inflammatory disease which is fundamentally different from dermatitis. Its treatments include topical medications and systemic drugs depending on different stages of the disease. However, these commonly used therapies are falling far short of clinical needs due to various drawbacks. More precise therapeutic strategies with minimized side effects and improved compliance are highly demanded. Recently, the rapid development of biomaterial-based therapies has made it possible and promising to attain topical psoriasis treatment. In this review, we briefly describe the significance and challenges of the topical treatment of psoriasis and emphatically overview the latest progress in novel biomaterial-based topical therapies for psoriasis including microneedles, nanoparticles, nanofibers, and hydrogels. Current clinical trials related to each biomaterial are also summarized and discussed.

Exploring the potential of nanocarriers in antipsoriatic therapeutics

Psoriasis is an autoimmune disease characterized by erythematous, scaly patches on the skin. It can be effectively managed with topical therapies since they deliver drugs to target sites of disease efficiently and can minimize systemic side-effects while ensuring high patient compliance. However, conventional topical formulations are ineffective in treating psoriasis due to their poor percutaneous penetration and inability to reach deeper layers of the skin. Thus, it is important to explore new approaches for managing psoriasis safely and effectively while also maintaining patient compliance without compromising safety. Over the last few decades, a variety of nanocarriers have been extensively investigated as a new approach to delivering drugs to the skin that are effective against psoriasis. These nanocarriers are notable for their therapeutic effectiveness, increased localization of medication in the skin, and reduced side-effects. The purpose of this review is to explore the recent advances in polymer-based, lipid-based, metallic, and microneedle-based novel nanoformulations of antipsoriatic drugs. There have been detailed discussions about several nanocarrier systems including nanoemulsions, liposomes, nanostructured lipid carriers, ethosomes, solid lipid nanoparticles, micelles, gold nanoparticles, silver nanoparticles, and microneedles. In a nutshell, nanoformulations are considered a promising avenue for psoriasis treatment since they offer better penetration, targeted delivery, and enhanced safety and efficacy.

Curcumin-based nanotechnology approaches and therapeutics in restoration of autoimmune diseases

Autoimmune diseases usually arise as a result of an aberrant immune system attack on normal tissues of the body, which leads to a cascade of inflammatory reactions. The immune system employs different types of protective and anti-inflammatory cells for the regulation of this process. Curcumin is a known natural anti-inflammatory agent that inhibits pathological autoimmune processes by regulating inflammatory cytokines and their associated signaling pathways in immune cells. Due to the unstable nature of curcumin and its susceptibility to either degradation, or metabolism into other chemical entities (i.e., metabolites), encapsulation of this agent into various nanocarriers would appear to be an appropriate strategy for attaining greater beneficial effects from curcumin as it pertains to immunomodulation. Many studies have focused on the design and development of curcumin nanodelivery systems (micelles, dendrimers, and diverse nanocarriers) and are summarized in this review in order to obtain greater insight into novel drug delivery systems for curcumin and their suitability for the management of autoimmune diseases.

Boosting the anti-inflammatory effect of self-assembled hybrid lecithin-chitosan nanoparticles via hybridization with gold nanoparticles for the treatment of psoriasis: elemental mapping and in vivo modeling

Gold nanoparticles are a promising drug delivery system for treatment of inflammatory skin conditions, including psoriasis, due to their small size and anti-inflammatory properties. The aim of this study was to conjugate gold nanoparticles with anti-psoriatic formulations that previously showed successful results in the treatment of psoriasis (tacrolimus-loaded chitosan nanoparticles and lecithin-chitosan nanoparticles) by virtue of their surface charges, then examine whether the hybridization with gold nanoparticles would enhance the anti-psoriatic efficacy in vivo. Successful formation of gold nanoparticles was examined by elemental mapping and selected area electron diffraction (SAED). Hybrid conjugates were examined in terms of particle size and zeta potential by dynamic light scattering (DLS). Morphological features were captured by transmission electron microscope (TEM) and X-ray diffraction (XRD) analysis was conducted, as well. All characterization was conducted for the conjugated nanoparticles and compared with their bare counterparts. The in vivo results on imiquimod (IMQ)-induced mouse model showed promising anti-psoriatic effects upon application of gold conjugated tacrolimus-loaded lecithin-chitosan hybrid nanoparticles with a significant difference from the bare hybrid nanoparticles in some of the inflammatory markers. The anti-inflammatory effect of the gold conjugate was also evident by a lower spleen to body weight ratio and a better histopathological skin condition compared to other tested formulations.

Strategies for Biomaterial-Based Spinal Cord Injury Repair via the TLR4-NF-κB Signaling Pathway

The repair and motor functional recovery after spinal cord injury (SCI) has remained a clinical challenge. Injury-induced gliosis and inflammation lead to a physical barrier and an extremely inhibitory microenvironment, which in turn hinders the recovery of SCI. TLR4-NF-κB is a classic implant-related innate immunomodulation signaling pathway and part of numerous biomaterial-based treatment strategies for SCI. Numerous experimental studies have demonstrated that the regulation of TLR4-NF-κB signaling pathway plays an important role in the alleviation of inflammatory responses, the modulation of autophagy, apoptosis and ferroptosis, and the enhancement of anti-oxidative effect post-SCI. An increasing number of novel biomaterials have been fabricated as scaffolds and carriers, loaded with phytochemicals and drugs, to inhibit the progression of SCI through regulation of TLR4-NF-κB. This review summarizes the empirical strategies for the recovery after SCI through individual or composite biomaterials that mediate the TLR4-NF-κB signaling pathway.

Transdermal Permeation Assays of Curcumin Aided by CAGE-IL: In Vivo Control of Psoriasis

Psoriasis is a clinically heterogeneous skin disease with an important genetic component, whose pathophysiology is not yet fully understood and for which there is still no cure. Hence, alternative therapies have been evaluated, using plant species such as turmeric (Curcuma longa Linn.) in topical preparations. However, the stratum corneum is a barrier to be overcome, and ionic liquids have emerged as potential substances that promote skin permeation. Thus, the main objective of this research was to evaluate a biopolysaccharide hydrogel formulation integrating curcumin with choline and geranic acid ionic liquid (CAGE-IL) as a facilitator of skin transdermal permeation, in the treatment of chemically induced psoriasis in mice. The developed gel containing curcumin and CAGE-IL showed a high potential for applications in the treatment of psoriasis, reversing the histological manifestations of psoriasis to a state very close to that of normal skin.

Peroxisome proliferator-activator receptor γ and psoriasis, molecular and cellular biochemistry

The pathophysiology of psoriasis is complex and has not been completely elucidated. Better understanding of the pathogenesis may contribute to further improvement of our therapeutic strategies controlling psoriasis. Emerging evidence points to a causative relationship between altered activity of peroxisome proliferator-activated receptor γ (PPARγ) and psoriasis. The present review focuses on deeper understanding of the possible role of PPARγ in the pathogenesis of psoriasis and the potential of PPARγ agonist to improve the treatment of psoriasis. PPARγ is decreased in psoriasis. PPARγ possibly has effects on the multiple aspects of the pathogenesis of psoriasis, including abnormal lipid metabolism, insulin resistance, immune cells, pro-inflammatory cytokines, keratinocytes, angiogenesis, oxidative stress, microRNAs and nuclear factor kappa B. As defective activation of PPARγ is involved in psoriasis development, PPARγ agonists may be promising agents for treatment of psoriasis. Pioglitazone appears an effective and safe option in the treatment of patients with psoriasis, but there are still concerns about its potential side effects. Research effort has recently been undertaken to explore the PPARγ-activating potential of natural products. Among them some have been studied clinically or preclinically for treatment of psoriasis with promising results.

Immunomodulatory effects of curcumin in systemic autoimmune diseases

Systemic autoimmune diseases like rheumatoid arthritis, multiple sclerosis, and systemic lupus erythematosus represent various autoimmune conditions identified by immune system dysregulation. The activation of immune cells, auto-antigen outbreak, inflammation, and multi-organ impairment is observed in these disorders. The immune system is an essential complex network of cells and chemical mediators which defends the organism's integrity against foreign microorganisms, and its precise operation and stability are compulsory to avoid a wide range of medical complications. Curcumin is a phenolic ingredient extracted from turmeric and belongs to the Zingiberaceae, or ginger family. Curcumin has multiple functions, such as inhibiting inflammation, oxidative stress, tumor cell proliferation, cell death, and infection. Nevertheless, the immunomodulatory influence of curcumin on immunological reactions/processes remains mostly unknown. In the present narrative review, we sought to provide current information concerning the preclinical and clinical uses of curcumin in systemic autoimmune diseases.

Polymeric Nanoparticles-Loaded Hydrogels for Biomedical Applications: A Systematic Review on In Vivo Findings

Clinically available medications face several hurdles that limit their therapeutic activity, including restricted access to the target tissues due to biological barriers, low bioavailability, and poor pharmacokinetic properties. Drug delivery systems (DDS), such as nanoparticles (NPs) and hydrogels, have been widely employed to address these issues. Furthermore, the DDS improves drugs’ therapeutic efficacy while reducing undesired side effects caused by the unspecific distribution over the different tissues. The integration of NPs into hydrogels has emerged to improve their performance when compared with each DDS individually. The combination of both DDS enhances the ability to deliver drugs in a localized and targeted manner, paired with a controlled and sustained drug release, resulting in increased drug therapeutic effectiveness. With the incorporation of the NPs into hydrogels, it is possible to apply the DDS locally and then provide a sustained release of the NPs in the site of action, allowing the drug uptake in the required location. Additionally, most of the materials used to produce the hydrogels and NPs present low toxicity. This article provides a systematic review of the polymeric NPs-loaded hydrogels developed for various biomedical applications, focusing on studies that present in vivo data.

Protein materials as sustainable non- and minimally invasive strategies for biomedical applications

Protein-based materials have found applications in a wide range of biomedical fields because of their biocompatibility, biodegradability and great versatility. Materials of different physical forms including particles, hydrogels, films, fibers and microneedles have been fabricated e.g. as carriers for drug delivery, factors to promote wound healing and as structural support for the generation of new tissue. This review aims at providing an overview of the current scientific knowledge on protein-based materials, and selected preclinical and clinical studies will be reviewed in depth as examples of the latest progress within the field of protein-based materials, specifically focusing on non- and minimally invasive strategies mainly for topical application.

Chitosan/hyaluronan nanogels co-delivering methotrexate and 5-aminolevulinic acid: A combined chemo-photodynamic therapy for psoriasis

Psoriasis does not respond adequately to the monotherapy, tailoring combined strategies for synergistical treatment remains challenging. We fabricated chitosan/hyaluronan nanogels to co-load methotrexate (MTX) and 5-aminoleavulinic acid (ALA), i.e., MTX-ALA NGs, for a combined chemo-photodynamic therapy for psoriasis. Compared with MTX-ALA suspension, the NGs enhanced the penetration and retention of MTX and ALA through and into the skin in vitro and in vivo (p < 0.001). NGs enhanced the cellular uptake (p < 0.001), protoporphyrin IX conversion (p < 0.001), and reactive oxygen species generation (3.93-fold), subsequently exerted the synergistical anti-proliferation and apoptosis on lipopolysaccharide-irritated HaCaT cells with the apoptosis rate of 78.6%. MTX-ALA NGs efficiently ameliorated the skin manifestations and down-regulated the proinflammatory cytokines of TNF-α and IL-17A in imiquimod-induced psoriatic mice (p < 0.001). Importantly, MTX-ALA NGs reduced the toxicities of oral MTX to the liver and kidney. The results support that MTX-ALA NG is a convenient, effective, and safe combined chemo-photodynamic strategy for psoriasis treatment.

Nanotechnology-based medicinal products and patents: a promising way to treat psoriasis

Psoriasis is an autoimmune skin disorder that is characterised by chronic inflammation and erythematous scaly patches. It has a significant impact on the patient's quality of life and can cause psychological stress. There are several aspects which cause psoriasis for instance, environmental issues, immune disorders, bacterial infections, and genetic issues. Plentiful therapeutic means or treatments are accessible, but not any of them can completely and effectively cure psoriasis without hindering patient compliance. Hence, it becomes challenging to discover a new drug moiety or any drug delivery method to cure psoriasis. Conventional treatment of psoriasis involves anti-inflammatory agents, immune suppressants, phototherapy, and biologic treatment, those were given in different forms such as topical, oral, or systemic formulations, but these all were unsuccessful to accomplish complete reduction of psoriasis as well as causing adverse side effects. In terms of dose frequency, doses, efficacy, and side effects, nanotechnology-based new formulations are the most promising prospects for addressing the challenges and limits associated with present psoriasis formulations. Hence, our major goal of this review is to present various advanced nanotechnological approaches for effective topical treatment of psoriasis. In short, nano-formulations continue to be formed as very promising modality in the treatment of psoriasis as they suggest improved penetration, targeted delivery, increased safety, and efficacy.

Transdermal Delivery of Therapeutic Compounds With Nanotechnological Approaches in Psoriasis

Psoriasis is a chronic, immune-mediated skin disorder involving hyperproliferation of the keratinocytes in the epidermis. As complex as its pathophysiology, the optimal treatment for psoriasis remains unsatisfactorily addressed. Though systemic administration of biological agents has made an impressive stride in moderate-to-severe psoriasis, a considerable portion of psoriatic conditions were left unresolved, mainly due to adverse effects from systemic drug administration or insufficient drug delivery across a highly packed stratum corneum via topical therapies. Along with the advances in nanotechnologies, the incorporation of nanomaterials as topical drug carriers opens an obvious prospect for the development of antipsoriatic topicals. Hence, this review aims to distinguish the benefits and weaknesses of individual nanostructures when applied as topical antipsoriatics in preclinical psoriatic models. In view of specific features of each nanostructure, we propose that a proper combination of distinctive nanomaterials according to the physicochemical properties of loaded drugs and clinical features of psoriatic patients is becoming a promising option that potentially drives the translation of nanomaterials from bench to bedside with improved transdermal drug delivery and consequently therapeutic effects.

Mathematical modelling of nanoparticle-mediated topical drug delivery to skin tissue

Nanoparticles have been extensively studied to improve drug delivery outcomes, however, their use in topical delivery remains controversial. Although the feasibility to cross the human skin barrier has been demonstrated in experiments, the risk of low drug concentration in deep tissue still limits the application. In this study, mathematical modelling is employed to examine the performance of nanoparticle-mediated topical delivery for sending drugs into the deep skin tissue. The pharmacokinetic effect is evaluated based on the drug exposure over time. As compared to the delivery using plain drugs, nanoparticle-mediated topical delivery has the potential to significantly improve the drug exposure in deep skin tissue. Modelling predictions denote that the importance of sufficient long-term drug-skin contact in achieving effective drug deposition in the deep skin tissue. The delivery outcomes are highly sensitive to the release rate. Accelerating the release from nanoparticles in stratum corneum is able to improve the drug exposure in stratum corneum and viable epidermis while resulting in the reductions in dermis and blood. The release rate in stratum corneum and viable epidermis should be well-designed below a threshold for generating effective drug accumulation in dermis and blood. A more localised drug accumulation can be achieved in the capillary-rich region of dermis by increasing the local release rate. The release rate in dermis needs to be optimised to increase the drug exposure in the dermis region where there are fewer blood and lymphatics capillaries. Results from this study can be used to improve the regimen of topical delivery for localised treatment.

Polymer nanotherapeutics to correct autoimmunity

The immune system maintains homeostasis and protects the body from pathogens, mutated cells, and other harmful substances. When immune homeostasis is disrupted, excessive autoimmunity will lead to diseases. To inhibit the unexpected immune responses and reduce the impact of treatment on immunoprotective functions, polymer nanotherapeutics, such as nanomedicines, nanovaccines, and nanodecoys, were developed as part of an advanced strategy for precise immunomodulation. Nanomedicines transport cytotoxic drugs to target sites to reduce the occurrence of side effects and increase the stability and bioactivity of various immunomodulating agents, especially nucleic acids and cytokines. In addition, polymer nanomaterials carrying autoantigens used as nanovaccines can induce antigen-specific immune tolerance without interfering with protective immune responses. The precise immunomodulatory function of nanovaccines has broad prospects for the treatment of immune related-diseases. Besides, nanodecoys, which are designed to protect the body from various pathogenic substances by intravenous administration, are a simple and relatively noninvasive treatment. Herein, we have discussed and predicted the application of polymer nanotherapeutics in the correction of autoimmunity, including treating autoimmune diseases, controlling hypersensitivity, and avoiding transplant rejection.

Preparation, Characterization and Evaluation of the Anti-Inflammatory Activity of Epichlorohydrin-β-Cyclodextrin/Curcumin Binary Systems Embedded in a Pluronic®/Hyaluronate Hydrogel

Curcumin (Cur) is an anti-inflammatory polyphenol that can be complexed with polymeric cyclodextrin (CD) to improve solubility and bioavailability. The aim of the present work was to prepare a CurCD hydrogel to treat inflammatory skin conditions. Epichlorohydrin-β-CD (EpiβCD) was used as polymeric CD. To characterize the binary system, solid-state and in-solution studies were performed. Afterwards, an experimental design was performed to optimize the hydrogel system. Finally, the CurEpiβCD hydrogel system was tested for anti-inflammatory activity using a HaCat psoriasis cell model. Co-grinded Cur/EpiβCD binary system showed a strong interaction and Curcumin solubility was much improved. Its combination with Pluronic® F-127/hyaluronate hydrogel demonstrated an improvement in release rate and Curcumin permeation. After testing its anti-inflammatory activity, the system showed a significant reduction in IL-6 levels. Hydrogel-containing CurEpiβCD complex is a great alternative to treat topical inflammatory diseases.

Self-assembled tacrolimus-loaded lecithin-chitosan hybrid nanoparticles for in vivo management of psoriasis

Lecithin-chitosan hybrid nanoparticles are emerging as a promising nanocarrier for topical drug delivery. They could achieve a maximized encapsulation of hydrophobic drugs due to the lipophilic nature of lecithin that comprises the core while enhancing retention in the upper skin layers using the positively charged polymeric coat of chitosan. The aim of this study is to incorporate tacrolimus; a hydrophobic anti-proliferative agent into lecithin chitosan hybrid nanoparticles by ethanolic injection technique using a suitable co-solvent to enhance encapsulation of the drug and allow a satisfactory release profile in the upper skin layers. Tacrolimus was successfully incorporated into the synthesized particles using olive oil and Tween 80 as co-solvents, with particle size (160.9 nm ± 15.9 and 118.7 nm ± 13.3, respectively) and EE (88.27% ± 4.3 and 66.72% ± 1.8, respectively). The in vitro drug release profile showed a faster release pattern for the Tween 80-containing particles over a 48-hour period (79.98% vs. 35.57%), hence, were selected for further investigation. The hybrid nanoparticles achieved significantly higher skin deposition than the marketed product (63.51% vs. 34.07%) through a 24-hour time interval, particularly, to the stratum corneum and epidermis skin layers. The in vivo results on IMQ-mouse models revealed superior anti-psoriatic efficacy of the synthesized nanoparticles in comparison to the marketed product in terms of visual observation of the skin condition, PASI score and histopathological examination of autopsy skin samples. Additionally, the in vivo drug deposition showed superior skin deposition of the nanoparticles compared to the marketed product (74.9% vs. 13.4%).

Tacrolimus-loaded chitosan nanoparticles for enhanced skin deposition and management of plaque psoriasis

Tacrolimus is a natural macrolide that exhibits an anti-proliferative action by T-lymphocytic cells inhibition. Hence, it was tested as a potential topical treatment to improve and control psoriatic plaques. In this study, for the first time the lipophilic tacrolimus in chitosan nanoparticles was used to achieve the desired response and dermal retention of the drug using a modified ionic gelation technique. The hydrophobic drug, tacrolimus, was successfully encapsulated into the synthesized positively-charged particles (140.8 nm ± 50.0) and EE of (65.5% ± 1.3). Local skin deposition of the drug was significantly enhanced with 82.0% ± 0.6 of the drug retained in the skin compared to 34.0% ± 0.9 from tarolimus® ointment. An outstanding response to the prepared formula was the enhanced hair growth rate in the treated animals, which can be considered an excellent sign of the skin recovery from the induced psoriatic plaques after only three days of treatment.

Lipid-based nanoparticles for psoriasis treatment: a review on conventional treatments, recent works, and future prospects

Psoriasis is a lingering inflammatory skin disease that attacks the immune system. The abnormal interactions between T cells, immune cells, and inflammatory cytokines causing the epidermal thickening. International guidelines have recommended topical treatments for mild to moderate psoriasis whilst systemic and phototherapy treatments for moderate to severe psoriasis. However, current therapeutic approaches have a wider extent to treat moderate to severe type of psoriasis especially since the emergence of diverse biologic agents. In the meantime, topical delivery of conventional treatments has prompted many unsatisfactory effects to penetrate through the skin (stratum corneum). By understanding the physiology of stratum corneum barrier functions, scientists have developed different types of lipid-based nanoparticles like solid lipid nanoparticles, nanostructured lipid carriers, nanovesicles, and nanoemulsions. These novel drug delivery systems help the poorly solubilised active pharmaceutical ingredient reaches the targeted site seamlessly because of the bioavailability feature of the nanosized molecules. Lipid-based nanoparticles for psoriasis treatments create a paradigm for topical drug delivery due to their lipids' amphiphilic feature to efficiently encapsulate both lipophilic and hydrophilic drugs. This review highlights different types of lipid-based nanoparticles and their recent works of nano formulated psoriasis treatments. The encapsulation of psoriasis drugs through lipid nanocarriers unfold numerous research opportunities in pharmaceutical applications but also draw challenges for the future development of nano drugs.

Preparation of Silk Fibroin/Carboxymethyl Chitosan Hydrogel under Low Voltage as a Wound Dressing

At present, silk fibroin (SF) hydrogel can be prepared by means of electrodeposition at 25 V in direct current (DC) mode. Reducing the applied voltage would provide benefits, including lower fabrication costs, less risk of high voltage shocks, and better stability of devices. Here, a simple but uncommon strategy for SF-based hydrogel preparation using 4 V in DC mode is discussed. SF was mixed and cross-linked with carboxymethyl chitosan (CMCS) through hydrogen bonding, then co-deposited on the graphite electrode. The thickness, mass, and shape of the SF/CMCS hydrogel were easily controlled by adjusting the electrodeposition parameters. Morphological characterization of the prepared hydrogel via SEM revealed a porous network within the fabricated hydrogel. This structure was due to intermolecular hydrogen bonding between SF and CMCS, according to the results of thermogravimetric analysis and rheological measurements. As a potential wound dressing, SF/CMCS hydrogel maintained a suitable moisture environment for wound healing and demonstrated distinct properties in terms of promoting the proliferation of HEK-293 cells and antibacterial activity against Escherichia coli and Staphylococcus aureus. Furthermore, histological studies were conducted on a full-thickness skin wound in rats covered with the SF/CMCS hydrogel, with results indicating that this hydrogel can promote wound re-epithelization and enhance granulation tissue formation. These results illustrate the feasibility of using the developed strategy for SF-based hydrogel fabrication in practice for wound dressing.

Enhanced transdermal efficiency of curcumin-loaded peptide-modified liposomes for highly effective antipsoriatic therapy

Psoriasis is one of the most influential and fastest-growing inflammatory diseases of the skin. Curcumin (CRC) is an effective antipsoriatic drug that is often carried by nanoparticles or liposomes mainly administered via the skin. However, the therapeutic effectiveness and bioavailability of this drug are restricted due to the functions of the skin barrier to liposomes. Herein, we proposed a peptide-modified curcumin-loaded liposome (CRC-TD-Lip) to expedite the transdermal delivery of curcumin and enhance the inhibition of psoriasis. CRC-TD-Lip was prepared and dispersed uniformly with high stability and high curcumin encapsulation efficiency. We confirmed the improved intracellular uptake of CRC-TD-Lip, the increased inhibitory effect of CRC-TD-Lip on HaCaT cells, and the heightened transdermal ability of CRC-TD-Lip. Then, the enhanced antipsoriatic ability of CRC-TD-Lip was evaluated in vivo using an imiquimod-induced psoriasis mouse model. The results indicated that the developed CRC-TD-Lip can effectively improve the delivery of curcumin across the skin and enhance the antipsoriasis efficiency. This work can provide a strategy for enhancing the transdermal delivery efficiency of drugs for various skin diseases.

A comprehensive review of the therapeutic potential of curcumin nanoformulations

Today, due to the prevalence of various diseases such as the novel coronavirus (SARS-CoV-2), diabetes, central nervous system diseases, cancer, cardiovascular disorders, and so on, extensive studies have been conducted on therapeutic properties of natural and synthetic agents. A literature review on herbal medicine and commercial products in the global market showed that curcumin (Cur) has many therapeutic benefits compared to other natural ingredients. Despite the unique properties of Cur, its use in clinical trials is very limited. The poor biopharmaceutical properties of Cur such as short half-life in plasma, low bioavailability, poor absorption, rapid metabolism, very low solubility (at acidic and physiological pH), and the chemical instability in body fluids are major concerns associated with the clinical applications of Cur. Recently, nanoformulations are emerging as approaches to develop and improve the therapeutic efficacy of various drugs. Many studies have shown that Cur nanoformulations have tremendous therapeutic potential against various diseases such as SARS-CoV-2, cancer, inflammatory, osteoporosis, and so on. These nanoformulations can inhibit many diseases through several cellular and molecular mechanisms. However, successful long-term clinical results are required to confirm their safety and clinical efficacy. The present review aims to update and explain the therapeutic potential of Cur nanoformulations.

Nanomaterials and Essential Oils as Candidates for Developing Novel Treatment Options for Bovine Mastitis

Nanomaterials have been used for diagnosis and therapy in the human medical field, while their application in veterinary medicine and animal production is still relatively new. Nanotechnology, however, is a rapidly growing field, offering the possibility of manufacturing new materials at the nanoscale level, with the formidable potential to revolutionize the agri-food sector by offering novel treatment options for prevalent and expensive illnesses such as bovine mastitis. Since current treatments are becoming progressively more ineffective in resistant bacteria, the development of innovative products based on both nanotechnology and phytotherapy may directly address a major global problem, antimicrobial resistance, while providing a sustainable animal health solution that supports the production of safe and high-quality food products. This review summarizes the challenges encountered presently in the treatment of bovine mastitis, emphasizing the possibility of using new-generation nanomaterials (e.g., biological synthesized nanoparticles and graphene) and essential oils, as candidates for developing novel treatment options for bovine mastitis.

Immunomodulatory nanosystems for treating inflammatory diseases

Inflammatory disease (ID) is an umbrella term encompassing all illnesses involving chronic inflammation as the central manifestation of pathogenesis. These include, inflammatory bowel diseases, hepatitis, pulmonary disorders, atherosclerosis, myocardial infarction, pancreatitis, arthritis, periodontitis, psoriasis. The IDs create a severe burden on healthcare and significantly impact the global socio-economic balance. Unfortunately, the standard therapies that rely on a combination of anti-inflammatory and immunosuppressive agents are palliative and provide only short-term relief. In contrast, the emerging concept of immunomodulatory nanosystems (IMNs) has the potential to address the underlying causes and prevent reoccurrence, thereby, creating new opportunities for treating IDs. The IMNs offer exquisite ability to precisely modulate the immune system for a therapeutic advantage. The nano-sized dimension of IMNs allows them to efficiently infiltrate lymphatic drainage, interact with immune cells, and subsequently to undergo rapid endocytosis by hyperactive immune cells (HICs) at inflamed sites. Thus, IMNs serve to restore dysfunctional or HICs and alleviate the inflammation. We identified that different IMNs exert their immunomodulatory action via either of the seven mechanisms to modulate; cytokine production, cytokine neutralization, cellular infiltration, macrophage polarization, HICs growth inhibition, stimulating T-reg mediated tolerance and modulating oxidative-stress. In this article, we discussed representative examples of IMNs by highlighting their rationalization, design principle, and mechanism of action in context of treating various IDs. Lastly, we highlighted technical challenges in the application of IMNs and explored the future direction of research, which could potentially help to overcome those challenges.